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Deposition from United States v. SFWMD, et al., Case No. 88-1886-CIV-HOEVELER |
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834
1 UNITED STATES DISTRICT COURT
FOR THE
2 SOUTHERN DISTRICT OF FLORIDA
3
****************************
4 UNITED STATES OF AMERICA, *
Plaintiff *
5 * Case Number
VS. * 88-1886-CIV
6 * Hoeveler
SOUTH FLORIDA WATER *
7 MANAGEMENT DISTRICT, ET AL., *
Defendants *
8 *****************************
9
10 Deposition of WILLIAM W. WALKER, JR.,
11 taken on behalf of the defendants South Florida
12 Water Management District and John R. Wodraska
13 pursuant to the applicable rules of the Federal
14 Rules of Civil Procedure, before Linda Marie
15 MacDonald, Registered Professional Reporter and
16 Notary Public within and for the Commonwealth
17 of Massachusetts, at the offices of Skadden,
18 Arps, Slate, Meagher & Flom, One Beacon Street,
19 Boston, Massachusetts, on Tuesday, February 12,
20 1991, commencing at 9:08 a.m.
21
22
23 LINDA MARIE MacDONALD, RPR-CM
REGISTERED PROFESSIONAL REPORTER
24 60 LAWRENCE ROAD, PLYMOUTH, MA 02360
(508) 747-6615
835
1 A P P E A R A N C E S:
2 UNITED STATES ATTORNEY'S OFFICE
By A.U.S.A Richard Harrison
3 155 South Miami Avenue, Suite 600
Miami, FL 33130
4 for the United States of America.
5 SKADDEN, ARPS, SLATE, MEAGHER & FLOM
By Attorney Laura B. Ahearn
6 1440 New York Ave., N.W.
Washington, D.C. 20005
7 for South Florida Water Management
District and John R. Wodraska.
8
PEEPLES, EARL & BLANK
9 By Attorney Rick J. Burgess
One Biscayne Tower, Suite 3636
10 Miami, FL 33131
for the cities of Belle Glade and
11 Clewiston, defendant intervenors.
12 STATE OF FLORIDA OFFICE OF GENERAL COUNSEL
By Asst. Gen. Counsel David A. Crowley
13 Department of Environmental Regulation
Twin Towers Office Building
14 2600 Blair Stone Road
Tallahassee, FL 332301
15 for the Florida Department of
Environmental Regulation.
16
17 A L S O P R E S E N T:
18 Douglas Robson, Consultant, SFWMD
John Davis, Consultant, Belle Glade and
19 Clewiston
Peter Ghavami, Legal Assistant, Skadden
20 Arps
21
22
23
24
DEPOSITION OF WILLIAM W. WALKER, JR.
836
1 I N D E X
Witnesses Examination
2
WILLIAM W. WALKER, JR., resumed
3 (By Ms. Ahearn) 838
4 E X H I B I T S
5 Number For ID
DX 38 Total Phosphorus Trend Analysis, 841
6 Shark Slough
7 DX 39 S12 Composite, Shark River Slough, 909
Taylor Slough, Coastal Basin
8
DX 40 Yearly Total P Concs & Loads, 923
9 ENP Inflows, with attachments
10 DX 41 Total P Times Series - ENP Inflows 923
Excluding Outliers, Flow > 0,
11 with attachments
12 DX 42 WQ Summary - ENP Inflows 923
Not Flow-Weighted
13
DX 43 ENP Flow-Weighted Mean Concs 923
14
DX 44 WQ Summary - ENP Marsh Stations 923
15 Not Flow-Weighted
16 DX 45 ENP Marsh Data - Trend Analysis, 923
All Results by Station
17
DX 46 ENP Marsh Data - Trend Analysis, 923
18 All Results for Variable = DO,
TNTP and TP
19
DX 47 Station P35 Total P/Stage Graph 923
20
DX 48 Station P36 Total P/Stage Graph 923
21
DX 49 Memo to Garver from Walker 923
22 11/14/90; Re: Data Needs to
Support Research
23
DX 50 Document dated 1/7/91 923
24 Data Needs: Supplement to 11/9/91
Memo to G. Garver
DEPOSITION OF WILLIAM W. WALKER, JR.
837
1 E X H I B I T S
2 Number For ID
3 DX 51 Letter to Scheidt from Higer 923
dated 6/29/89, with attachments
4
DX 52 Memo to Clint Leaks from Walker 923
5 WATSTORE Retrieval Request
6 DX 53 Document entitled "Meeting Agenda" 923
Subject: Access to Technical Data
7 Maintained on District Computers
8 DX 54 Letter to Scheidt from SFWMD 923
(Mary Lou Daniel), 12/13/89,
9 with attachments
10 DX 55 Document entitled "Trends at 923
Other WCA Stations"
11
DX 56 Simulation of Trend Detection 985
12 Procedures; Tests on Means and
Frequency, Clean and Messy Data
13
14
15
16
17
18
19
20
21
22
23
24
DEPOSITION OF WILLIAM W. WALKER, JR.
838
1 P R O C E E D I N G S
2 WILLIAM W. WALKER, JR.,
3 having been previously duly sworn, was deposed
4 and testified as follows:
5 CONTINUED DIRECT EXAMINATION
6 BY MS. AHEARN:
7 Q. Good morning, Dr. Walker.
8 A. Good morning.
9 Q. What is the Chi2 test for homogeneity of trend?
10 A. Are you asking that in reference to a
11 particular document?
12 Q. Well, I guess first I'd like a working
13 definition of this test.
14 MR. HARRISON: Object to form. No
15 foundation, no predicate laid to show that it's
16 a term of art. You may answer.
17 A. As I have applied that test in the trend
18 analysis as described in Exhibit 17, it is a
19 test to determine the likelihood that there are
20 significant differences in the trend magnitude
21 from one season to another.
22 Q. Is the Chi2 test for homogeneity of trend a
23 special term in the field of science of
24 statistics?
DEPOSITION OF WILLIAM W. WALKER, JR.
839
1 A. I have used the term and the equations as they
2 are defined in a book by Gilbert that is
3 referenced in Exhibit 17.
4 Q. Could you, please, point me to that reference,
5 if you could identify for me where in
6 Exhibit 17 we'll see reflected your Chi2 test
7 for homogeneity of trend?
8 MR. HARRISON: Do you want the second
9 one first, Counsel, or the reference? It's
10 compound.
11 Q. Are those two different things, your reference
12 to Gilbert and where in the -- let's start all
13 over.
14 Direct me to the reference to Gilbert,
15 please.
16 A. The reference to Gilbert is on page 45 of
17 Exhibit 17. It's a book entitled "Statistical
18 Methods for Environmental Pollution
19 Monitoring."
20 MS. AHEARN: And I would like the record
21 to reflect that we have numbered each page on
22 the original Exhibit 17 here to which
23 Dr. Walker is referring to make sure that there
24 is a legible page number on each page in the
DEPOSITION OF WILLIAM W. WALKER, JR.
840
1 exhibit.
2 Q. Okay. That was in the list of references,
3 correct?
4 A. Correct.
5 Q. Could you point to me the textual discussion of
6 this Gilbert method?
7 A. I don't recall actually discussing that in the
8 report. This test for homogeneity of trend was
9 something that is included in the computer
10 program that I wrote for the purpose of
11 conducting these tests.
12 But the results -- as I recall, the
13 results of that trend did not indicate that
14 there were significant differences from one
15 season to another with respect to trend
16 magnitude, so there was no reason to discuss
17 those results in the context of the report.
18 Q. Just so it's clear, on reviewing Exhibit 17, I
19 found no mention of the Chi2 test.
20 A. That's right. That's probably correct. I do
21 not recall actually describing it in the text,
22 but it is a test that I applied.
23 Q. Do you recall if you discussed the Chi2 test in
24 any prior drafts of Exhibit 17?
DEPOSITION OF WILLIAM W. WALKER, JR.
841
1 A. I do not believe I did.
2 Q. When in the sequential process of your trend
3 analysis did you perform the Chi2 test?
4 A. I don't recall when I added that particular
5 algorithm to the computer program that I was
6 working with.
7 (Exhibit No. 38 marked for
8 identification)
9 Q. Dr. Walker, I'll ask the court reporter to hand
10 you Exhibit 38. Can you identify that?
11 A. This is two pages of graphs and statistics
12 entitled Total Phosphorus Trend Analysis for
13 Shark slough as described on the first page.
14 And I believe the second page describes --
15 summarizes a similar analysis for Station S332
16 -- that is Taylor slough -- and Station S18C,
17 which is the Coastal station.
18 Q. I see at the bottom of each page here a
19 reference to your Chi2 test.
20 A. That's correct.
21 Q. Let me first ask you, You generated both pages
22 of Exhibit 38?
23 A. Yes, I did.
24 Q. And this was on your personal computer?
DEPOSITION OF WILLIAM W. WALKER, JR.
842
1 A. Yes.
2 Q. I asked because it looks to be a somewhat
3 different format than other things I have seen
4 you produce.
5 Does this Exhibit 38 illustrate how you
6 performed the Chi2 test?
7 A. No. This Exhibit 38 merely states the results
8 of the Chi2 test.
9 Q. Do you recall if you produced any other
10 documents or computer files that illustrate how
11 the Chi2 test was performed?
12 A. The methods that were used to calculate the
13 Chi2 test are reflected in the FORTRAN computer
14 software that I turned over with my other
15 computer files.
16 Q. Those are the files reflected in Exhibit 18,
17 the printout of the directories?
18 A. That's correct.
19 Q. Can you, please, identify by page number and
20 name the directory where I'll find the program
21 that incorporates the Chi2 test algorithms?
22 A. Okay. We're referring now to Exhibit No. 18.
23 The program that contains the Chi2 test for
24 homogeneity of trend would be included in the
DEPOSITION OF WILLIAM W. WALKER, JR.
843
1 directory listed on -- starting on page 14, the
2 directory G:\LIB\FOR.
3 Q. Can you identify a particular file or files
4 that contains the Chi2 test?
5 A. I believe that a portion of the test is
6 contained in the file on page 18 called
7 SKEND.FOR. That's the sixth file from the top
8 on page 18. Other subroutines may be used in
9 calculating that test, as well.
10 Q. I note that there is one labeled CHISQP.FOR.
11 It sounds like a likely candidate.
12 A. Yes. That routine may be used as well in
13 calculating that test result. That's located
14 on page 14.
15 Q. Are each of the trend programs which we have
16 discussed before on page 13 of Exhibit 18, are
17 each of those trends programs designed to call
18 up the Chi2 subroutine from the FORTRAN
19 directory?
20 A. Yes.
21 Q. While we're here on Exhibit 18, I want to ask
22 you a couple more questions I'm not clear on.
23 You identified your G:\DBASE directory as
24 containing the surface water quality data that
DEPOSITION OF WILLIAM W. WALKER, JR.
844
1 you used with the KTEST program for producing
2 Exhibit 17?
3 MR. HARRISON: Counsel, are you on a
4 particular page on Exhibit 18?
5 MS. AHEARN: The DBASE is on page 24.
6 Q. I believe when I had asked you about this
7 before, I only spoke in terms of the surface
8 water quality data.
9 Are all of the files for flow, rainfall
10 and stage data which the KTEST program
11 retrieved for purposes of doing the analysis
12 reflected in Exhibit 17, are all of those data
13 files also included in this G:\DBASE?
14 A. To the best of my recollection, yes.
15 Q. And in G:\DBASE we also see a number of files
16 for various variables that appear to relate to
17 marsh stations; is that correct? For example,
18 entries for P33, those files would denote data
19 concerning a marsh station within Everglades
20 National Park?
21 A. That's correct.
22 Q. In the preliminary analysis that you have
23 performed of Everglades marsh data, am I
24 correct you used a program called MULTI?
DEPOSITION OF WILLIAM W. WALKER, JR.
845
1 A. That's correct.
2 Q. All of the data files set up to be retrieved by
3 the MULTI program, are all of those data files
4 contained in directory G:\DBASE?
5 A. I believe I testified previously regarding the
6 procedures that one would use to execute these
7 programs. Basically the procedure involves
8 editing the file, in this case MULTI.DAT, which
9 contains essentially the instructions of the
10 program to access certain data files, so in
11 that file MULTI.DAT should be the directory and
12 the specific file names that would be used in a
13 particular analysis or run of the program.
14 Q. Would you need to actually look at that entry
15 in the program to ascertain where all of the
16 data files for use in that program are located?
17 A. That's correct. In the listing of that
18 MULTI.DAT input file should be an indication of
19 where the files are located and what their
20 names are.
21 Q. Is the same true for the RMED program? You
22 would need to look at the .DAT file in order to
23 tell us exactly in which directories the
24 appropriate data files were stored?
DEPOSITION OF WILLIAM W. WALKER, JR.
846
1 A. Yes.
2 Q. Just trying to see if I can cut some corners.
3 Dr. Walker, when you edited Exhibit 17
4 for submission to the Water Resources Bulletin,
5 did you look for statements that were more
6 likely to draw questions or criticisms from the
7 peer reviewers? Was that a consideration in
8 deciding which statements to take out of the
9 text?
10 MR. HARRISON: I object to the
11 characterization. I think we had a round on
12 that, whether it was editing or what it was. I
13 think there is a separate exhibit in here,
14 Counsel, that went to the Water Resources
15 Bulletin if you want to refer to that.
16 A. I believe I testified previously that my
17 objective in editing Exhibit 17 for submission
18 to Water Resources Bulletin was to shorten it
19 to provide an acceptable length for
20 publication.
21 Q. And you explained to us why you omitted the
22 section on the loading analysis. Did you omit
23 other parts of the text?
24 A. I may have omitted certain sentences or certain
DEPOSITION OF WILLIAM W. WALKER, JR.
847
1 paragraphs in the effort of -- in the interest
2 of shortening the overall text.
3 Q. In Exhibit 17, would you turn to page 3,
4 please? The last sentence in the first
5 paragraph, is there any reason why you deleted
6 that sentence from the draft submitted to the
7 Water Resources Bulletin?
8 A. I don't recall whether specifically I did
9 delete that sentence.
10 Q. If you would like to refer to Exhibit 12 to
11 verify that, it would be page 2 of Exhibit 12.
12 MR. BURGESS: Exhibit what? I'm sorry?
13 MS. AHEARN: Exhibit 12.
14 A. Well, as I stated, my primary emphasis in
15 editing this for submission was to shorten the
16 document. That was a sentence that I thought
17 was not essential to the rest of the document,
18 and it was rather long and it was an
19 opportunity to shorten the document.
20 I believe that the concept expressed in
21 that sentence is something that is generally
22 accepted in the water quality management field
23 and is not something that is essential for the
24 purposes of understanding this technical
DEPOSITION OF WILLIAM W. WALKER, JR.
848
1 document and understanding the analysis which I
2 performed.
3 Q. Do you feel that you would be able to defend
4 this sentence, the last sentence in the first
5 paragraph of page 3, Exhibit 17, before the
6 peer reviewers of the Water Resources Bulletin?
7 A. Yes.
8 Q. Let me see if I can shorten this up.
9 Recognizing the need to shorten the
10 document, can you tell me what other criteria
11 guided your exercise of judgment in deciding
12 which statements to extract from Exhibit 17?
13 MR. HARRISON: Object. Asked and
14 answered. Also, no foundation for your
15 characterization that there were other
16 criteria.
17 Q. Were there other criteria other than there was
18 a page limitation?
19 MR. HARRISON: Asked and answered.
20 MS. AHEARN: Excuse me. You just told
21 me --
22 A. No.
23 Q. There were no other criteria that guided your
24 judgment?
DEPOSITION OF WILLIAM W. WALKER, JR.
849
1 A. My objective was to shorten the document. And
2 in the process of selecting which particular
3 pieces I would remove for the purpose of
4 shortening the document, I removed those pieces
5 which I felt were not necessary to communicate
6 the essential components of the work and those
7 parts which were separable in a sense as I
8 described earlier.
9 I believe the analysis on the loading is
10 a separate piece that could very well
11 constitute a separate paper, a separate journal
12 article, and I may very well submit that for
13 publication separately. Those are the kinds of
14 considerations that I had, but my overall
15 objective was to shorten the article to make it
16 more acceptable for publication in a journal.
17 Q. Thank you. We had proceeded through page 5 of
18 Exhibit 17 yesterday. Would you turn to
19 page 6? On the first line there you refer to
20 fixed minimum delivery schedules. What do you
21 mean by that phrase?
22 A. I mean that there were certain volumes of water
23 that were scheduled to be released through
24 Structures S332 and S18C. And as distinct from
DEPOSITION OF WILLIAM W. WALKER, JR.
850
1 the schedule for Shark slough, where the
2 volumes were based upon rainfall, these
3 deliveries at S332 and S18C were not based upon
4 antecedent rainfall.
5 Q. I just want to make sure that we're clear here.
6 By "schedules," are we talking about hydrologic
7 ranges as opposed to a calendar schedule?
8 A. What do you mean by "hydrologic ranges"?
9 Q. By "delivery schedule," are you referring to a
10 preset time period for water deliveries? Is it
11 a schedule in that sense like scheduled for
12 every Monday or it's already established on a
13 calendar that deliveries occur on X day?
14 MR. HARRISON: Object to form.
15 Q. Is that what we mean here by "schedules"?
16 MR. HARRISON: Object to form. It might
17 be easier just to ask him when he -- what his
18 understanding of the schedules are.
19 A. To my recollection, the flows through S332 and
20 S18C are operated to provide a certain
21 guaranteed minimum amount of flow. I'm
22 uncertain as to whether that is an annual flow
23 or whether that flow is broken out on a
24 seasonal basis. And then on top of that
DEPOSITION OF WILLIAM W. WALKER, JR.
851
1 minimum guaranteed amount would be any flows
2 that would occur as a result of excess runoff
3 or drainage from the basin following storm
4 events.
5 Q. Are water deliveries scheduled to be made at
6 any specific time?
7 A. I believe that there is a seasonality to the
8 delivery schedule.
9 Q. Are you knowledgeable of the currently
10 effective operating criteria for water
11 deliveries to Everglades National Park?
12 MR. HARRISON: Object to form. There's
13 different delivery points to the Park.
14 A. Which -- which basin are you referring to?
15 Q. Are you familiar with the operating criteria
16 for all three basins?
17 A. I am generally familiar with the operating
18 criteria as they are discussed in Exhibit 17.
19 Q. Are you aware of any changes in operating
20 criteria since the time period which ends 1989
21 that's discussed in Exhibit 17?
22 A. I'm not aware of any such changes.
23 MR. HARRISON: Was that December '89,
24 Counsel?
DEPOSITION OF WILLIAM W. WALKER, JR.
852
1 MS. AHEARN: The text says 1989,
2 Mr. Harrison.
3 MR. HARRISON: But without a month.
4 Q. In the second full paragraph on page 6, the
5 second sentence, you state that:
6 Values reported to be below the
7 detection limit are set equal to the
8 detection limit minus a small
9 concentration increment.
10 At what point in your trend analysis
11 work did you set these below-detection-limit
12 values minus a small concentration increment?
13 A. What do you mean by "point"?
14 Q. Did you do trend analyses with the detection
15 limits without deducting the small
16 concentration increment?
17 A. I believe that the first draft of the work did
18 not perform that task. In other words, the
19 first set of trend analyses that I performed
20 that's described in the July 1990 draft I did
21 not make that adjustment in detection limit.
22 Q. Is there a reason why that wasn't attempted for
23 the first draft?
24 A. To perform that task, it involved a substantial
DEPOSITION OF WILLIAM W. WALKER, JR.
853
1 amount of work. I had to go through and
2 essentially edit the data files, the source
3 data files, to make that adjustment. And I
4 felt in the first draft that since the overall
5 percentage of total phosphorus values below
6 detection limits was on the order of 7 percent
7 or less, it was unlikely that that adjustment
8 would make a significant difference in the
9 results of the trend analysis. Therefore, I
10 did not undertake that adjustment in the first
11 draft.
12 Q. Why did you feel it was worthwhile to do that
13 substantial work after the first draft?
14 A. Because I was given more time -- as I testified
15 earlier, I was under some commitment to
16 complete the first draft by July of 1990, and I
17 had additional time between July and September.
18 And it was also -- a comment regarding this
19 topic was made by one of the reviewers. So
20 those were the reasons why this adjustment was
21 made in the second or in the final version of
22 the trend analysis.
23 Q. Did you have this in mind independent of the
24 comment of the reviewer?
DEPOSITION OF WILLIAM W. WALKER, JR.
854
1 A. I had it in mind as something that might be
2 done as part of the analysis.
3 Q. Did you perform sensitivity analyses to see the
4 effect of setting below-detection-limit values
5 at other levels?
6 A. As the text on page 6 describes, the trend test
7 is based upon ranks of the data and, as such,
8 the results for the trend analyses would not be
9 sensitive to the particular magnitude selected
10 for this adjustment.
11 Q. Could you set it at zero and not have any
12 impact on the trend analysis?
13 A. Setting it at zero would be problematical for
14 the Series C analyses because the Series C
15 analyses involved taking logarithms -- in fact,
16 all of them involve taking logarithms of the
17 data prior to the trend analysis. So now that
18 I think about it, zero could not have been used
19 in the way I performed this test.
20 Q. Does the selection of the level at which to set
21 below-detection-limit values affect the
22 calculation of the Kendall slope?
23 A. Possibly.
24 Q. Did you do any sensitivity analyses of that?
DEPOSITION OF WILLIAM W. WALKER, JR.
855
1 A. Only insofar as the draft -- the July draft did
2 not make any of this sort of adjustment and the
3 final draft did make this adjustment.
4 Q. So you tested between no adjustment and an
5 adjustment of .0001 milligram per liter?
6 A. Correct.
7 Q. What is the difference between those two
8 scenarios?
9 A. Well, it's difficult to generalize about the
10 difference between those scenarios for all
11 variables and all stations. But, for example,
12 if we take what I identified as Series A at
13 Station S12T, the Kendall slope estimated in
14 the July draft when I did not make that
15 adjustment for detection limits was 7.1 percent
16 per year; that is, the median rate of increase
17 in phosphorus concentration at the S12s was
18 7.1 percent per year.
19 Q. Dr. Walker, are you referring to a particular
20 page or table in Exhibit 7?
21 A. Yes. I'm referring to Exhibit 7, Table 5.
22 Q. Thank you.
23 A. And in that Exhibit 7, Table 5, as I just
24 mentioned, the trend for S12T was 7.1 percent
DEPOSITION OF WILLIAM W. WALKER, JR.
856
1 per year. And in the final version, Table 5,
2 Exhibit 17, the trend for the same station and
3 variable was 7.0 percent per year.
4 Q. Is the change from 7.1 to 7.0 not significant?
5 MR. HARRISON: Object to form.
6 A. The change from 7.1 to 7.0 is a change from 7.1
7 to 7.0. I don't know what you mean by
8 "significant."
9 Q. Do you have the sense of what the slope would
10 have been if you had set below-detection-limit
11 values at .002?
12 A. I did not test that directly. But as I stated
13 earlier, since on the order of 7 percent of the
14 observations were below detection limits and
15 since the slope is calculated as the median of
16 all the slopes calculated within each season,
17 it is unlikely that a change in this adjustment
18 factor would have influenced the calculated
19 slope. And in no case would an adjustment of
20 this factor for detection limits influence the
21 calculated P level or the significance level
22 upon which we base -- we estimate the
23 likelihood of a trend.
24 Q. Thank you. I understand that distinction
DEPOSITION OF WILLIAM W. WALKER, JR.
857
1 there. In the middle of the middle paragraph
2 on page 6, Exhibit 17, you state:
3 The detection limit for total and
4 ortho phosphorus increased from .002 to
5 .004 milligram per liter in 1981.
6 What was the cause of that change?
7 A. I do not know.
8 Q. Do you know if there were any changes in lab
9 technique at this time?
10 A. Not to my knowledge.
11 Q. Are you aware of any changes in the detection
12 limits of other constituents?
13 A. The database that was supplied by the District
14 included measurements of trace metal
15 concentrations, heavy metals. And in reviewing
16 the listing of that data, it was apparent that
17 there were some fluctuations in the detection
18 limit in those cases. I did not conduct a
19 trend analysis on that information.
20 Q. Are you aware of any changes in detection
21 limits among any of the water quality
22 constituents you did analyze?
23 MR. HARRISON: Other than total
24 phosphorus?
DEPOSITION OF WILLIAM W. WALKER, JR.
858
1 MS. AHEARN: Yes.
2 Q. Other than the ortho and total phosphorus in
3 '81.
4 A. Of the constituents which I analyzed, the other
5 species for which I recall the presence of
6 values below detection limits would include
7 ammonia nitrogen and nitrate and nitrite
8 nitrogen. The remaining species to my
9 recollection were generally reported at values
10 -- at quantifiable values above the detection
11 limit, so there would be no way of knowing
12 precisely what the detection limit was for
13 those constituents because the concentrations
14 were always above the detection limits.
15 In the case of ammonia nitrogen and
16 nitrite nitrogen, I don't recall a systematic
17 change or a shift in the detection limit in a
18 particular time period.
19 Q. You said that those other constituents were
20 reported at levels. Do you know what the lab
21 detection limit for those constituents were?
22 A. Which constituents?
23 Q. Well, you told us that for ammonia -- I'm
24 afraid I forget the other you pointed out --
DEPOSITION OF WILLIAM W. WALKER, JR.
859
1 you recalled reports below detection limit --
2 A. Right.
3 Q. -- for those two constituents. And all the
4 others you see as being reported at
5 quantifiable values.
6 A. Correct.
7 Q. Do you know at what level the lab felt they
8 could detect those values for those other
9 constituents?
10 A. I'm still unclear as to what you mean by "other
11 constituents."
12 Q. Among the 20 listed in Table 1 that you
13 analyzed in Exhibit 17. I guess my point is
14 quite simple, Dr. Walker. I asked you if you
15 were aware of changes in detection limits among
16 the constituents other than total and ortho
17 phosphorus, and what you have told me is that
18 you saw these other constituents reported above
19 detection.
20 The fact that they are reported above
21 doesn't tell us what the detection limits were,
22 does it?
23 A. That's correct.
24 Q. Okay. It doesn't tell us whether there were
DEPOSITION OF WILLIAM W. WALKER, JR.
860
1 changes of detection limit?
2 A. It tells us if there were detection limits,
3 they were not such that they would be greater
4 than the -- that the new detection limits would
5 not be greater than any value which is reported
6 as quantified in the database.
7 Q. Prior to 1981 were there any values for total
8 or ortho phosphorus reported between .002 and
9 .004?
10 A. There may have been. I don't recall.
11 Q. What was the accurate detection limit for total
12 and ortho phosphorus prior to 1981?
13 MR. HARRISON: Object to form. There's
14 been no predicate laid.
15 A. I don't know what you mean by "accurate."
16 Q. If in 1979 a value for total phosphorus, the
17 .003, was reported, was that value below
18 detection limit?
19 A. If it was reported in the database as a numeric
20 value without a -- an accompanying indicator
21 that would indicate that it was below detection
22 limits such as the less-than sign or K symbol
23 -- I don't recall what the symbol was that the
24 District used in their data sets. But if it
DEPOSITION OF WILLIAM W. WALKER, JR.
861
1 was reported as a numeric value, then it was
2 assumed to be above the -- above or equal to
3 the detection limit that was present in the
4 laboratory at that particular time.
5 Q. With the instrumentation available in 1979,
6 what was the lowest detection limit possible
7 for total phosphorus?
8 A. The detection limit reported by the District
9 which reflected the instrumentation that they
10 had at that particular time in their laboratory
11 proceedures was .002 milligrams per liter.
12 Q. Are you familiar with the instrumentation that
13 was generally available for water quality
14 analyses in 1979?
15 MR. HARRISON: Object to form.
16 A. I am aware that there was instrumentation
17 available that was capable of analyzing total
18 phosphorus concentrations to within a detection
19 limit of .002 to .004 milligrams per liter.
20 But in terms of the specific hardware, I
21 couldn't give you any details on that.
22 Q. How about with respect to instrumentation
23 available presently for total phosphorus
24 analysis?
DEPOSITION OF WILLIAM W. WALKER, JR.
862
1 A. There may have been some improvements in the
2 instrumentation over time that might have made
3 it possible to detect total phosphorus to lower
4 values, but again I cannot give you the details
5 on the specific hardware involved or the
6 technology.
7 Q. In the other constituents where you said you
8 did see values reported below detection, did
9 you employ the same procedure with regard to
10 those constituents of setting the values equal
11 to detection limit minus a small concentration
12 increment?
13 A. To my recollection, yes, I did.
14 Q. What specific detection limits did you use for
15 these other constituents?
16 A. I don't recall.
17 Q. Do you recall the source of the detection limit
18 which you did use?
19 A. It would have been derived by reviewing the
20 data file and essentially identifying the
21 largest numeric value that was reported as less
22 than the detection limit.
23 Q. You adopted that as the lab detection limit?
24 A. For the purpose of adjusting the data to
DEPOSITION OF WILLIAM W. WALKER, JR.
863
1 account for values below detection limit, yes.
2 Q. Just to make sure I'm clear, that's not the
3 source of the .002 and .004 detection limit
4 used for total and ortho phosphorus, correct?
5 A. Yes, it was the same procedure that I used for
6 total and ortho phosphorus.
7 Q. You just derived that by reviewing the data?
8 A. Correct.
9 Q. From that review of the data, you were able to
10 determine that the detection limit changed in
11 1981?
12 A. Yes.
13 Q. Did you have any other source of information on
14 that?
15 A. Well, it may have been discussed in the ONRW
16 meetings. I don't recall for sure.
17 Q. Are there alternative methods for adjusting
18 values reported below detection limits for use
19 in the Seasonal Kendall test other than the
20 method you used here, setting it equal to a
21 detection limit minus a small concentration
22 increment?
23 MR. HARRISON: Did you just say,
24 Counsel, are there other methods or --
DEPOSITION OF WILLIAM W. WALKER, JR.
864
1 MS. AHEARN: Are there alternatives --
2 A. One could conceive of other procedures. A
3 procedure that I have used is the procedure
4 that was recommended in one or more of the
5 papers by Hirsch and Slack on the Seasonal
6 Kendall test.
7 Q. If I could direct your attention a little
8 farther down in this middle paragraph on
9 page 6, Exhibit 17, there is a sentence that
10 starts "Phosphorus time series have been
11 adjusted..." Could you read that sentence and
12 tell me if it is accurate?
13 A. Phosphorus time series have been
14 adjusted to a uniform detection limit of
15 .004 mg/liter by setting each value
16 equal to the minimum of the reported
17 value and .004 mg/liter.
18 I believe there is an error in that
19 equation -- in that sentence. The term
20 "minimum" should be replaced by the term
21 "maximum." That was a grammatical error on my
22 part.
23 Q. If the trend you see in phosphorus
24 concentrations in Park inflows is attributable
DEPOSITION OF WILLIAM W. WALKER, JR.
865
1 to the discharge of agricultural waters, what
2 trends would you expect to see in other
3 constituents that you have analyzed in
4 Exhibit 17?
5 MR. HARRISON: I'm going to object to
6 form. Counsel, does your question assume that
7 the trends are solely due to the discharge of
8 agricultural water without any of these other
9 variables? If that is your assumption, I will
10 object to the assumption since the assumption
11 has no basis in evidence in this deposition.
12 But I want the hypothetical cleared up.
13 A. I believe yesterday I testified to my
14 preliminary conclusions regarding possible
15 causes of these apparent trends, and increases
16 in loadings from the watershed -- watersheds of
17 the Water Conservation Areas was indicated as
18 being one of the likely causes, among others.
19 Other -- if one were to take your
20 hypothetical and if it is based on the
21 assumption that it is agriculture runoff that
22 is the causal factor or contributing to these
23 loads, one might be concerned about potential
24 trends in other substances that are also found
DEPOSITION OF WILLIAM W. WALKER, JR.
866
1 in agricultural runoff.
2 Q. Which would be those substances?
3 A. Well, agricultural runoff would contain a wide
4 range of substances, including nutrients,
5 inorganic species, pesticides, heavy metals.
6 Q. If a trend in phosphorus was attributable to
7 agricultural runoff, would you expect to see
8 corollary trends in other conservative
9 constituents such as chlorides?
10 A. Not necessarily.
11 Q. Are there any constituents other than ortho
12 phosphorus and the nitrogen species in which
13 you would expect to see corollary trends if the
14 trend in total phosphorus concentrations was
15 caused by agricultural runoff?
16 A. Well, I would be concerned about things such as
17 pesticides.
18 Q. And you have not conducted a trend analysis on
19 pesticides, correct?
20 A. To my knowledge, there's not an adequate
21 database to perform such an analysis.
22 Q. Okay. Any other constituents?
23 (The witness gave no response.)
24 Q. How about ions and cations?
DEPOSITION OF WILLIAM W. WALKER, JR.
867
1 A. Well, ions and cations are part of the natural
2 system. They are contained in rainfall, and
3 they are contained in natural drainage. They
4 wouldn't necessarily be exclusively earmarks
5 for agricultural runoff.
6 Q. Could they be earmarks for agricultural runoff?
7 MR. HARRISON: Object to form.
8 A. I said they wouldn't necessarily be earmarks
9 for agricultural runoff.
10 Q. Have you looked for any earmarks for
11 agricultural runoff in the work you have done?
12 A. I have analyzed the data for 12 water quality
13 components for trends at the Park inflow
14 points.
15 Q. Twelve or twenty?
16 A. Excuse me. Twenty.
17 Q. Even apart from this trend analysis, has the
18 work you performed on South Florida water
19 quality issues included any investigation of
20 what constituents might be earmarks for
21 agricultural runoff?
22 A. No.
23 Q. Page 9. We're really moving.
24 For the purposes of the record,
DEPOSITION OF WILLIAM W. WALKER, JR.
868
1 Dr. Walker, could you, please, define the term
2 "robust" as you use it, for example, here in
3 the paragraph at the top of page 9, Exhibit 17?
4 A. I used the term "robust" in page 9 in reference
5 to the Seasonal Kendall slope. What I mean
6 when I say that the estimate of the Seasonal
7 Kendall slope is robust is that it is more
8 likely to reflect the underlying distribution
9 of the bulk of the data than to be -- than to
10 reflect a few data points at the extremes of
11 the data and it is less likely to be sensitive
12 to outliers or other unrepresentative samples.
13 Q. I'd like to refer you to page 3 in Exhibit 7,
14 which is your July 3 draft.
15 You can see in the mid paragraph there
16 under the heading "Methods," the last sentence
17 there in Exhibit 7 does not appear in the
18 comparable text in Exhibit 17. Can you explain
19 that difference?
20 A. You're referring essentially to the omission of
21 one sentence, is that --
22 Q. In Exhibit 17, page 3, middle paragraph,
23 there's a sentence.
24 MR. HARRISON: Exhibit 7, I think,
DEPOSITION OF WILLIAM W. WALKER, JR.
869
1 Counsel.
2 MS. AHEARN: Thank you.
3 Q. Exhibit 7, page 3, middle paragraph, the last
4 sentence starts, "Another advantage is that..."
5 That sentence largely does not appear in
6 Exhibit 17 and, if you can, can you explain why
7 this was changed?
8 A. I don't recall specifically. It may have been
9 in response to one of the reviewers' comments.
10 I don't view it as a particularly important
11 statement.
12 Q. The statement as it appears in Exhibit 7?
13 A. Right.
14 Q. Again with reference to Exhibit 7, page 3, the
15 bottom paragraph, midway in the body of that
16 paragraph is a sentence starting, "Loftis et
17 al..."
18 Is there a reason why that does not
19 appear in Exhibit 17?
20 A. Well, the statement that you're referring to, I
21 believe, is:
22 Loftis et al. (1989) cautioned
23 against using the second test because of
24 its relatively low power (ability to
DEPOSITION OF WILLIAM W. WALKER, JR.
870
1 detect trends); they felt that
2 "reduction in power was too high a
3 price to pay for insensitivity to serial
4 correlation."
5 That statement was derived from -- I
6 derived that statement from the report by
7 Loftis et al. And I believe one of the other
8 reviewers of my report, I think it was Helsel
9 -- Helsel and Slack who together put together a
10 review of my report, took issue with that
11 statement. They disagreed with that statement
12 and they felt it was Loftis' opinion and they
13 disagreed with it. So I decided that it was
14 not an essential statement as far as I was
15 concerned to the report, so I took it out at
16 the suggestion of the reviewers.
17 Q. Well, you included the statement from Loftis in
18 your draft. Do you agree with Loftis?
19 A. I agree in the sense that if you're using the
20 second version of the Seasonal Kendall test
21 which accounts for serial correlation, you are
22 paying a price in that you are being very
23 conservative; you are trying to account for
24 serial correlation, and you're running the risk
DEPOSITION OF WILLIAM W. WALKER, JR.
871
1 of not detecting trends. You are reducing the
2 power of the test. But on the other hand, you
3 are accounting for a real phenomenon -- that
4 is, serial correlation.
5 There are trade-offs involved here. And
6 essentially the decision that I have made in
7 conducting the analysis was in fact to use this
8 more conservative test that accounts for serial
9 correlation even though it may have a chance of
10 failing to detect trends, it may miss trends at
11 some frequency, because I'm trying to account
12 for serial correlation.
13 Q. With a database such that you're using in
14 Exhibit 17, do Helsel and Slack agree that this
15 second version of the Seasonal Kendall test has
16 a reduction in power?
17 (Pause)
18 Q. Do you feel you need to refer to the written
19 comments in order to answer that?
20 A. I'm just looking at one of the previous
21 exhibits for a second.
22 Q. And you're referring to which exhibit number?
23 A. I'm referring to Exhibit No. 37.
24 Q. Thank you.
DEPOSITION OF WILLIAM W. WALKER, JR.
872
1 A. Exhibit No. 37 is the paper by Hirsch and Slack
2 entitled "A Nonparametric Trend Test for
3 Seasonal Data With Serial Dependence."
4 Figure 2 of that paper on page 730 shows the
5 results of power tests that were done in order
6 to compare essentially the power of the test
7 when serial correlation was considered as
8 compared with the power of the test when it was
9 ignored.
10 And those results do show that for a
11 series of ten years' worth of data, that the
12 percent of the time that trends -- that a trend
13 was detected was indeed lower when the test
14 accounted for serial correlation. That's for
15 the ten-year time series.
16 Other tests -- other simulations that
17 are described in this same paper show that the
18 power of the test and the Type 1 error is --
19 other simulations described in this paper show
20 that for time series less than ten years in
21 length, the procedure underestimates the -- the
22 procedure has a Type 1 error rate that is below
23 the nominal Type 1 error rate for time series
24 less than ten years in length.
DEPOSITION OF WILLIAM W. WALKER, JR.
873
1 Q. What about time series 12 years in length?
2 A. They consider the case of ten years in their
3 simulations and show that the test closely
4 approximates the nominal Type 1 error rate for
5 that condition.
6 Q. Have Hirsch and Slack or others addressed the
7 power of the test using a 12-year time series?
8 A. They considered five-, ten- and twenty-year
9 time series, and they recommend that the test
10 for periods of ten years or more, that the test
11 involving -- including serial correlation is
12 appropriate.
13 Q. In other words, it has adequate power to --
14 A. It may -- there may be some loss of power that
15 is associated with using this test which is a
16 more conservative test than the test that is --
17 that does not account for serial correlation,
18 but it has a more accurate representation of
19 the Type 1 error.
20 Q. When we talk about serial correlation here,
21 what does that mean?
22 A. We are talking about the tendency for the
23 values to be -- to occur not as random values
24 over time but to be correlated from one season
DEPOSITION OF WILLIAM W. WALKER, JR.
874
1 to the next.
2 Q. So that the serial correlation accounted for in
3 the modified Kendall test accounts for seasonal
4 serial correlation?
5 A. It accounts for serial correlation in the
6 values after the seasonal effects -- fixed
7 seasonal effects have been removed from the
8 data.
9 Q. Does it account for any serial correlation as
10 between years?
11 A. I believe that we discussed that previously.
12 The test does not account for serial
13 correlation from one year to the next.
14 Q. I apologize, but I'm learning. I want to make
15 sure I keep this straight.
16 What kind of correlation structure did
17 Hirsch and Slack use in simulating and testing
18 the power of their modified test?
19 MR. HARRISON: You mean in their own
20 report, Counsel, or in their review of
21 Dr. Walker's report?
22 Q. Has Hirsch prepared a review of your report,
23 Dr. Walker?
24 A. Dr. Slack has, yes.
DEPOSITION OF WILLIAM W. WALKER, JR.
875
1 Q. Has Dr. Hirsch?
2 A. Not to my knowledge.
3 Q. Okay. You told us about simulations performed
4 of the modified Kendall test for five-, ten-
5 and twenty-year time series --
6 A. Correct.
7 Q. -- by Hirsch and Slack?
8 A. Correct.
9 Q. What kind of correlation structures were they
10 using for those simulations?
11 A. They used a range of correlation structures
12 that are essentially defined as autoregressive
13 moving average models, ARMA models, and they
14 used a range of coefficients to reflect
15 different levels of autoregressive and moving
16 average dependence in the time series.
17 Q. By "models," does this mean that these are
18 artificially constructed correlation
19 structures?
20 A. These are correlation structures which have
21 been found to be representative of and typical
22 of water quality time series that have been
23 studied and analyzed with -- using these time
24 series techniques.
DEPOSITION OF WILLIAM W. WALKER, JR.
876
1 Q. Do you know how representative they are of the
2 correlation structure of the water quality
3 database utilized in Exhibit 17?
4 A. As described in 17, for example, on page 18 I
5 report values for what is called RA, which is
6 the first-order serial correlation coefficient
7 of the values.
8 Also, in Appendix A for each test result
9 I list the serial correlation coefficient for
10 each of the time series or each of the -- for
11 each set of tests that are documented in
12 Appendix A.
13 Q. Is the correlation structure of the water
14 quality data collected from the real world
15 utilized in Exhibit 17 accurately represented
16 by the correlation structures of the models
17 employed by Hirsch and Slack?
18 A. The cases considered by Hirsch and Slack were
19 designed to reflect a wide range of water
20 quality time series that they have examined in
21 their studies. I have not precisely fit these
22 types of time series models to the water
23 quality data that I analyzed for trend, but I
24 have characterized the serial correlation
DEPOSITION OF WILLIAM W. WALKER, JR.
877
1 structure as I mentioned with this term RA that
2 is documented in the report.
3 And the other factor that's important is
4 that -- the reason that we are concerned about
5 this serial correlation structure is because we
6 -- one limitation or one assumption of the test
7 is that there's no serial correlation in the
8 data from one year to the next other than
9 whatever serial correlation would be reflected
10 in a trend. And I have characterized that
11 possibility or evaluated that possibility by
12 calculating the serial correlation coefficients
13 from one year to the next within each season,
14 and these are documented on page 18, Table 2,
15 under -- again, under this column RA for each
16 month.
17 The magnitudes of those correlation
18 coefficients are generally low and not in a
19 range where I would be concerned about serial
20 correlation from one year to the next or in a
21 range where I would be concerned about the
22 applicability of the test.
23 Q. Your RA values are calculated based on years,
24 correct?
DEPOSITION OF WILLIAM W. WALKER, JR.
878
1 A. The RA value reported for a particular month
2 would be the serial correlation coefficient for
3 the values that are one year apart collected
4 within each month.
5 Q. And that would be a first order of correlation
6 structure?
7 A. That's correct.
8 Q. Did you look at any other correlation
9 structures in this database?
10 A. Since the first-order correlation structure for
11 the values one year apart are generally
12 insignificant, there would be no point in going
13 further in -- the difficulty that we have here
14 is that in order to quantify and define a
15 serial correlation structure from one year to
16 the next, it would be very hard to do with only
17 12 years' worth of data.
18 Q. Is it a limitation of the size of the database
19 that precludes looking at other correlation
20 structures in the database employed?
21 A. In terms of looking at whether higher order
22 terms -- whether there's any high-order serial
23 correlation structure in the values that are
24 spaced one year apart, it would be difficult to
DEPOSITION OF WILLIAM W. WALKER, JR.
879
1 identify those -- such terms with -- with only
2 12 years' worth of data. But the data that I
3 do have indicates that the serial correlation
4 coefficients from one year to the next are low
5 and are not in a range where the applicability
6 of the test should be an issue.
7 Q. On Table 2 of Exhibit 17 under your category
8 for RA values, for example, for the first
9 series there, the RA reported for Year* is
10 0.71. Could you, please, explain to me how that
11 was calculated?
12 A. That was calculated by -- starting from the raw
13 data, assigning the value to years and season
14 so that we have one value for each year and
15 season, performing the Seasonal Kendall test,
16 estimating the significance level of the
17 Seasonal Kendall test and estimating the trend
18 slope using the Seasonal Kendall slope
19 estimator, and subtracting from the seasonal
20 values the effect of the long-term trend using
21 that trend slope; so essentially removing the
22 trend from the seasonal values and subsequently
23 calculating the first-order serial correlation
24 coefficient of the remaining values.
DEPOSITION OF WILLIAM W. WALKER, JR.
880
1 Q. So you basically took a residual as against the
2 estimated Kendall slope?
3 A. That's correct.
4 Q. Let me ask you one question I missed along the
5 way, then I propose we take a break.
6 We were talking about the method you
7 used for deriving detection limits by reviewing
8 the values recorded from the lab. Would that
9 method allow you to detect a change in
10 detection limit at the time the detection limit
11 is changed by the lab?
12 A. The change in detection limit would be revealed
13 by the first observation in the data set that
14 would have an altered detection limit prior to
15 the -- compared to the prior part of the
16 record.
17 Q. So your answer is yes, it would allow you to
18 detect that change when it's made?
19 A. Only in terms of -- with -- only with respect
20 to the frame of reference of the sampling
21 dates. It can't tell you on what particular
22 date between sampling dates a change might have
23 occurred, and it can't tell you at what
24 particular date between sampling dates that
DEPOSITION OF WILLIAM W. WALKER, JR.
881
1 contain values above the detection limit. In
2 other words, the first -- the change in the
3 detection limit would be triggered by the first
4 change in the value reported as below a new
5 detection limit that had not occurred in the
6 previous part of the record.
7 MS. AHEARN: Time for a break.
8 (Short recess)
9
10 BY MS. AHEARN:
11 Q. Referring back to your RA values on Table 2,
12 Exhibit 17, Table 2 is on page 18 of that
13 exhibit.
14 For the RA value under Series A Year*,
15 is this 0.71 a month-to-month serial
16 correlation over the 12-year period?
17 MR. HARRISON: Before we go too far, is
18 Rick Burgess --
19 MR. DAVIS: You can go ahead.
20 MR. HARRISON: Okay. I didn't know if
21 he was missing.
22 A. Yes, with the trend removed.
23 Q. Is the procedure you used here deriving this
24 first order of serial correlation a procedure
DEPOSITION OF WILLIAM W. WALKER, JR.
882
1 commonly used in conjunction with the modified
2 Seasonal Kendall test?
3 MR. HARRISON: Object to form.
4 A. It's a common procedure for calculating a
5 serial correlation coefficient.
6 Q. So this procedure is a common statistical
7 procedure?
8 A. The concept of a serial correlation coefficient
9 and its calculation, yes, is a common
10 statistical procedure.
11 Q. Are you aware of any precedents for using this
12 common statistical procedure as you have
13 employed it here in conjunction with the
14 modified Seasonal Kendall test?
15 A. I'm using it here to quantify serial
16 correlation between years and between adjacent
17 months because that serial correlation bears on
18 the accuracy of the test.
19 Q. In the literature concerning the development
20 and testing of the Seasonal Kendall test, can
21 you point me to any discussions advising on the
22 use of this additional first-order serial
23 correlation?
24 A. I believe there was some discussion of that in
DEPOSITION OF WILLIAM W. WALKER, JR.
883
1 the paper by Berryman et al. in the references
2 that I supplied to the District.
3 Q. Are you aware of any applications of the
4 seasonal order of serial correlation method in
5 conjunction with the modified Seasonal Kendall
6 test to databases derived from actual
7 monitoring of other water systems?
8 A. The paper that I mentioned by Berryman may have
9 had some examples in it and some discussion of
10 applications. I don't recall.
11 Q. Table 2 in Exhibit 17 refers to S12T total
12 phosphorus data. Did you perform similar
13 first-order serial correlation calculations
14 with regard to individual S12 structures?
15 A. Yes.
16 Q. And with regard to S333 and S18?
17 A. Yes.
18 Q. Did you perform similar calculations with
19 respect to the other 19 water quality
20 constituents subject to your analysis?
21 A. Yes.
22 Q. Did you perform adjustments of your PROB2
23 values after you calculated the RA values?
24 A. Only as described in the text.
DEPOSITION OF WILLIAM W. WALKER, JR.
884
1 Q. And that would be at the top of page 19, the
2 first paragraph there?
3 A. No.
4 Q. I'm sorry. Could you point to me where that's
5 described in the text?
6 A. It would be the second paragraph on page 19.
7 Q. I'm sorry. I misspoke. Thank you.
8 Did you adjust PROB2 values for any
9 constituent other than total phosphorus?
10 A. No. As I stated, the only adjustments that I
11 made are described in that paragraph.
12 Q. I just wanted to make sure I was clear. I
13 don't see where this paragraph specifically is
14 limited to total phosphorus. It is limited
15 specifically to total phosphorus?
16 A. Only in the case of total phosphorus did I go
17 to the trouble of making those adjustments.
18 Q. Our review of the text left off on page 9. I'm
19 really not backing up. We'll go quickly.
20 MR. HARRISON: Two steps forward and
21 four back. Okay.
22 Q. In selecting to transform your Series A and B
23 data to log scale, was that one of the
24 decisions you made during your interactive
DEPOSITION OF WILLIAM W. WALKER, JR.
885
1 sessions on the computer?
2 A. The reasons why I used the logtransform are
3 described on page 10.
4 Q. Dr. Walker, this may just be a point of
5 clarification, but we talked about your
6 interactive session on the computer. Was this
7 one of the decisions which you investigated
8 during that session?
9 A. It would be very hard to separate what I
10 learned and the impressions that I got from the
11 interactive sessions with the computer and to
12 identify specifically whether that experience
13 influenced this particular decision.
14 Q. Do you recall if you investigated
15 transformations other than the log10?
16 A. Well, as is stated in the text, the reason for
17 using the log10 was to permit expression of the
18 units of the trend in terms of percent per
19 year, which was a convenient way and less
20 awkward way than expressing it in terms of
21 milligram per liter per year or whatever.
22 Also, the important factor is that the
23 results of the analysis in terms of the
24 significance levels and the probability of a
DEPOSITION OF WILLIAM W. WALKER, JR.
886
1 trend or no trend are independent of this log
2 transformation because the procedure -- the
3 Seasonal Kendall test is based upon rankings of
4 the data.
5 Q. Okay. Did you consider any other
6 transformations?
7 A. No, I did not.
8 Q. In Series C why did you limit your samples to
9 samples collected on days with positive flow as
10 opposed to using the Series A basic data?
11 A. The samples collected on days when there was
12 positive flow reflect the concentrations and
13 loadings of materials actually entering the
14 Park on a particular sample day, and they would
15 have, I would think, greater importance in
16 terms of evaluating trends in concentrations
17 and loadings entering the Park as compared with
18 Series A including the data points when there
19 was no flow. The interpretation of those
20 particular data with respect to impact on the
21 Park is difficult because the water was not
22 moving or at least not moving into the Park.
23 Q. But the two hydrologic variables you're looking
24 at here occur outside the Park, correct?
DEPOSITION OF WILLIAM W. WALKER, JR.
887
1 A. That's correct. They reflect conditions in
2 Water Conservation Area 3A, which is the
3 immediate source of water entering the Park in
4 Shark slough.
5 Q. Could I have you refer to your Equation 1 as it
6 appears in Exhibit 7, page 4, and compare that
7 with Equation 1 on page 10 of Exhibit 17?
8 Are there any changes in this equation
9 other than those that reflect the change in
10 hydrologic variables that you used?
11 A. Yes.
12 Q. And what are those other changes?
13 A. In Exhibit 7, Equation 1, concentrations or the
14 logarithm of concentration is regressed against
15 the logarithm of flow and upstream water
16 elevation where the -- where both the flow and
17 the upstream water elevation were measured on
18 the same day that the sample for concentration
19 was collected. So there was no lagging of the
20 time factor for the hydrologic variables.
21 And in the case of Exhibit 17, the final
22 report, Equation 1, we are dealing here with --
23 instead of flow and elevation, we're dealing
24 with rainfall and elevation. That's one
DEPOSITION OF WILLIAM W. WALKER, JR.
888
1 difference. And the other difference is that
2 in this final version the antecedent periods or
3 the averaging periods for the hydrologic
4 factors, rainfall and water elevation, are
5 adjusted. They are selected by the computer
6 using stepwise regression to find the time
7 scale of rainfall -- in other words, the number
8 of days of antecedent rain or the average --
9 the number of days of averaging the antecedent
10 water elevation, which provides the highest
11 degree of correlation with concentration. And
12 those lag periods and factors are subsequently
13 used in the regression equation.
14 Q. With reference to Exhibit 7, I believe you just
15 said that you relate concentration to the
16 elevation measured on the day of the sample; is
17 that correct?
18 A. In Exhibit 7, correct.
19 Q. In the text that starts right under the
20 expression of the equation, the elevation term
21 reflects the average water surface elevation.
22 What is that average?
23 A. That average is a daily average. It's a daily
24 average over the -- over the day at which the
DEPOSITION OF WILLIAM W. WALKER, JR.
889
1 sample was collected, not a spatial average. It
2 is actually the -- the water elevation measured
3 upstream of S12C. That sentence is somewhat
4 misleading.
5 Q. So in the analysis performed for the July 3
6 draft, you were using just the one gauge
7 upstream, the 12 --
8 A. S12C, the only gauge with a consistent record
9 over the entire period, correct.
10 Q. And is this average recording of -- of --
11 excuse me. Is this average the average of all
12 levels recorded from midnight to midnight on
13 the particular calendar date of a given sample?
14 A. Typically, when one deploys a stage recorder in
15 the field, the stage measurements are recorded
16 at certain time intervals. And there would be
17 some averaging process that would occur to
18 calculate the 24-hour average.
19 In other situations the water elevation
20 may be just recorded at one particular time if
21 it's done manually. I believe that these
22 measurements are made automatically and,
23 therefore, would reflect an average of a number
24 of measurements made over the day.
DEPOSITION OF WILLIAM W. WALKER, JR.
890
1 Q. Were these numbers reported to you as averages?
2 A. They were reported -- they were categorized in
3 the District's water quality database as
4 average daily values, to my recollection.
5 Q. So these aren't averages that you computed from
6 raw gauge readings?
7 A. No.
8 Q. Okay. Had you performed the stepwise multiple
9 regression for optimal values by the time you
10 had prepared the July 3 draft, Exhibit 7?
11 (The witness gave no response.)
12 Q. I mean, I recognize you've told us you had a
13 commitment to produce this document. I'm just
14 wondering, had you done the computer work,
15 performed the multiple regression, prior to
16 this time?
17 A. Are you asking me whether I did the multiple
18 regression that is reflected in Equation 1 of
19 Exhibit 17 before I wrote the first draft of
20 the report in July?
21 Q. Okay. That would be a good question.
22 A. No.
23 Q. Why did you subsequently decide to perform the
24 multiple regression?
DEPOSITION OF WILLIAM W. WALKER, JR.
891
1 A. Well, both of these equations that I have used
2 are multiple regressions.
3 Q. Let me ask my question more clearly.
4 Why didn't you select optimal values for
5 antecedent periods to employ in Equation 1 in
6 Exhibit 7?
7 MR. HARRISON: Object to form.
8 A. The concept of using variable antecedent
9 periods, which is the distinction we're making
10 here between these two drafts, I felt was
11 especially important when we brought in the
12 concept of using antecedent rainfall because
13 it's not obvious beforehand if one is trying to
14 correlate rainfall with concentration measured
15 at a certain time, there is no basis a priori
16 to specify the averaging period for the
17 rainfall. In other words, should I use the
18 rainfall on the sampling day? Should I use the
19 rainfall over the past week? Should I use the
20 rainfall over the past month? My answer to
21 those questions is I don't know.
22 So the way that I asked -- I get the
23 answer to that question is I do -- I set up the
24 programs so that they select -- they search for
DEPOSITION OF WILLIAM W. WALKER, JR.
892
1 the antecedent periods, the lengths of time
2 that provide the highest degree of correlation
3 between concentration and antecedent rainfall
4 and between concentration and antecedent water
5 elevation, and use that to adjust the
6 concentrations for hydrologic variability in my
7 Series C.
8 Q. What do you look at -- what factor or value do
9 you look at to determine which antecedent
10 period provides the highest correlation, the
11 optimal correlation?
12 A. I used a stepwise regression routine. I
13 believe the criterion that was used to select
14 the ideal or the optimal time scale was either
15 based upon something such as R2 or the
16 significance level of the regression term. I
17 don't recall precisely.
18 Q. So you may have used the P values as the
19 criterion for selecting the antecedent period?
20 A. Possibly.
21 Q. But you're not sure?
22 A. The P values in the multiple regression.
23 Q. Would you be able at this point to explain the
24 algorithm that you used? Would you be able to
DEPOSITION OF WILLIAM W. WALKER, JR.
893
1 explain that step by step?
2 A. In general terms.
3 Q. Okay.
4 A. The algorithm would involve starting with a
5 complete matrix or a table, if you will, where
6 each row would be a different sample, and for
7 each sample there would be a value for
8 concentration and there would be a value for
9 total antecedent rainfall over one day, seven
10 days, thirty days and so forth as indicated on
11 page 10. And there would also be a value for
12 antecedent water elevation averaged over one
13 day, seven days, thirty days, so forth. So
14 that would comprise a table.
15 I would then compute what is called a
16 correlation matrix or covariance matrix using
17 that table and starting with -- and then
18 address each hydrologic factor. Say if we
19 addressed rainfall, the program would search
20 for the rainfall term or the lag time one day,
21 seven days, thirty days, whatever, that was
22 most highly correlated with concentration and
23 include that in the regression equation. And
24 the next -- if -- it would be included in the
DEPOSITION OF WILLIAM W. WALKER, JR.
894
1 regression equation only if the P level for
2 that term was less than .1 -- that is, if in
3 fact there was a significant correlation
4 between rainfall for any of the time scales and
5 concentration.
6 If that procedure resulted in inclusion
7 of a rainfall term, I would then adjust the
8 concentrations by removing the portion of the
9 variability that is correlated with the
10 rainfall term and then search each of the
11 elevation terms to find the time scale that was
12 most highly correlated with elevation -- with
13 concentration. And from that exercise, I would
14 end up with an equation that had one term for
15 rainfall and one term for water elevation that
16 was correlated with concentration.
17 I tried alternative techniques as part
18 of the sensitivity analysis for fitting these
19 regression equations and found them to lead to
20 similar results in terms of the overall
21 significance level of the trend at S12s.
22 Q. Did you use what Snedecor and Cochran would
23 term a step-up procedure?
24 A. I used a stepwise regression equation. I guess
DEPOSITION OF WILLIAM W. WALKER, JR.
895
1 it would be termed a step-up, that's correct,
2 as opposed to a step-down.
3 Q. How many degrees of freedom did you lose when
4 you decided to use the log10 transformation?
5 A. For what purpose?
6 Q. You're asking me for what purpose you decided
7 to use the logarithmic transformation?
8 A. What are you referring to? When I used the
9 log -- you say when I used the log10
10 transformation. I used it in several instances
11 here.
12 Q. When you decided to use the log10
13 transformation for your Series A, B and C data,
14 how many degrees of freedom for application of
15 the Seasonal Kendall test did you lose?
16 MR. HARRISON: Objection, Counsel. For
17 all three combined, all three series? I just
18 want the witness to specify what his answer is
19 relating to, if he is capable of doing that
20 with that question.
21 A. In the case of Series A, B or C, I would not
22 interpret use of log10 transformation as loss
23 of any degrees of freedom.
24 Q. Some of the structures subject to your analysis
DEPOSITION OF WILLIAM W. WALKER, JR.
896
1 in Exhibit 17 are pumped structures, aren't
2 they?
3 A. I believe that S332 has a pump. I think 18C
4 may have a pump. I don't recall exactly.
5 Q. Are there any adjustments or special
6 statistical procedures that you should employ
7 to reflect the different nature of pumped
8 structures?
9 A. The flow values -- the daily flow values that I
10 have used for each of the structures would
11 reflect the combined flow through the pump plus
12 whatever might have occurred over a spillway if
13 such a structure existed at the particular
14 monitoring station. Other than reflecting the
15 total flow or the total volume released into
16 the Park on a particular day, there was nothing
17 special that needed to be done to account for
18 pumped flow as compared with released flow or
19 spilled flow.
20 Q. In terms of the factors that may impact a trend
21 in total phosphorus concentrations, are there
22 differences between pumped structures and those
23 structures that are not pumped?
24 MR. HARRISON: Object to form.
DEPOSITION OF WILLIAM W. WALKER, JR.
897
1 "Factors" is just too general. Go ahead.
2 A. The problem in your question is that when you
3 say "structures that are not pumped," that
4 could include a wide range of different type of
5 structures that could very well have some
6 distinction with pumped structures. So I can't
7 answer your question. It's way too general.
8 Q. I guess Mr. Harrison's right.
9 Are there any particular factors or
10 features of which you are aware with regard to
11 the impact of a pumped structure on total
12 phosphorus concentrations?
13 MR. HARRISON: Object to form.
14 A. Again, you would have to compare it to some
15 other scenario.
16 Q. Are you aware of any factors with regard to the
17 pumped structures you looked at compared to the
18 other structures that you looked at that didn't
19 have pumps?
20 MR. HARRISON: I object to form. Do you
21 have any of these factors in mind that you
22 might give him some specific guidance as to
23 what you're looking for?
24 MS. AHEARN: I'm wondering if the doctor
DEPOSITION OF WILLIAM W. WALKER, JR.
898
1 looked at this issue and if he identified any
2 structures that distinguished the pumped
3 structures from all other structures.
4 A. There is nothing special about the existence of
5 a pump, but there may be some distinguishing
6 characteristics between those structures with
7 pumps and those structures without pumps.
8 Q. Did you identify any such distinguishing
9 features?
10 A. Well, in the case of S332 and S18C the flow
11 releases into the Park are made from
12 essentially canal environments, canal systems,
13 and that is a different situation as compared
14 with releases through the S12s, where flow is
15 essentially released from a reservoir upstream
16 from Water Conservation Area 3A.
17 Q. Have you identified any other distinguishing
18 features?
19 A. Well, there are certainly geographic
20 differences and differences in watersheds.
21 Q. Any other distinguishing features which relate
22 to total phosphorus concentrations?
23 A. The sources of the water at the individual
24 structures would be different. There's lots of
DEPOSITION OF WILLIAM W. WALKER, JR.
899
1 distinctions from one structure to another.
2 That's my answer.
3 Q. Dr. Walker, have you performed any tests for
4 trend within the hydrologic variables you have
5 employed in Series C, both your Exhibit 7 and
6 your Exhibit 17 versions?
7 A. You're asking me if I tested for trends in the
8 hydrologic variables themselves?
9 Q. Yes.
10 A. Not to my recollection.
11 Q. If you could, please, turn to page 5 in
12 Exhibit 7. There is an Equation 2 expressed
13 mid page and then a paragraph of text under
14 that. Could you, please, read the last
15 sentence in that paragraph? It starts with
16 "More detailed analyses..." Could you read it
17 aloud, please?
18 A. More detailed analyses would be
19 needed to distinguish among alternative
20 trend shapes and to investigate causal
21 factors for those time series with
22 significant apparent trends.
23 Q. Today do you still agree with that statement?
24 MR. HARRISON: I would caution the
DEPOSITION OF WILLIAM W. WALKER, JR.
900
1 witness to ensure that he is comfortable with
2 the context of that statement in Exhibit 7. If
3 he feels the need to read the paragraph, fine.
4 MS. AHEARN: Please, Mr. Harrison.
5 That's a lot of coaching.
6 MR. HARRISON: It's not coaching. I'm
7 not going to let you ask him whether he agrees
8 with a sentence, Counsel, taken out of context
9 if it is out of context. I'm simply cautioning
10 the witness to look at the entire paragraph
11 that it's contained in, which is something that
12 you should have certainly offered in your
13 question. There is no coaching here at all,
14 Counsel. I don't know enough to coach the
15 witness on it.
16 MS. AHEARN: If there's a context,
17 Exhibit 7 clearly provides it.
18 MR. HARRISON: It certainly does.
19 A. Well, as is stated in the sentence above the
20 one that I just read:
21 The basic objective is to determine
22 whether the underlying frequency
23 distribution of concentration (or
24 concentration at a given flow and
DEPOSITION OF WILLIAM W. WALKER, JR.
901
1 upstream surface water elevation) is
2 stable over the time period examined.
3 Q. Do you agree with the sentence that follows
4 that?
5 A. I agree that the work that has been completed
6 to date is sufficient for defining the
7 existence of trends in concentration and
8 loading at various -- under various hydrologic
9 conditions at these locations.
10 Q. Is it tough to distinguish among alternative
11 trend shapes?
12 A. The -- as is stated in this sentence and as is
13 also stated in Exhibit 17, the method that I
14 have used does not distinguish among
15 alternative trend shapes.
16 Q. Is it sufficient to investigate causal factors?
17 A. As we discussed yesterday or last week, the
18 analysis provides information on trends. It
19 provides descriptions of correlations that can
20 be used and interpreted that can -- that can be
21 helpful for formulating opinions regarding
22 causation in the system. But the trend
23 analysis itself does not quantify the causal
24 factors.
DEPOSITION OF WILLIAM W. WALKER, JR.
902
1 Q. Why was this sentence in Exhibit 7 dropped from
2 Exhibit 17?
3 A. Because I view the investigation of the causes
4 and the delineation of the causes as a separate
5 task, as a more involved task, as compared with
6 the identification of the existence of the
7 trends.
8 Q. If you would turn to page 6 in Exhibit 7, the
9 last line of the first full paragraph on that
10 page, why was that sentence dropped from
11 Exhibit 17?
12 MR. HARRISON: I'm going to object to
13 your characterization. I don't doubt that it
14 was, but I think it's more preferable to ask
15 the witness if it was. And I would just
16 caution the witness to ensure that it was
17 dropped prior to answering that question. We
18 have had no testimony on that yet.
19 MS. AHEARN: But we do have the two
20 versions of the document identified by the
21 witness.
22 MR. HARRISON: Which will speak for
23 themselves, Counsel. I mean, if you don't want
24 the documents to speak for themselves, I'm
DEPOSITION OF WILLIAM W. WALKER, JR.
903
1 simply asking you the courtesy of asking him
2 the question to lay a foundation as to whether
3 or not it was dropped. It is certainly
4 conceivable that you could have missed
5 something.
6 A. I can't give a particular reason why that
7 sentence was dropped. It was apparently an
8 editorial decision on my part.
9 Q. Did you employ any analyses using a
10 significance level of .05?
11 A. I -- there was nothing specific to any of this
12 regarding assumptions on significance levels.
13 The results are reported in terms of the P
14 levels, and one can apply whatever -- whatever
15 criterion one wishes in terms of distinguishing
16 between the presence of trend and the absence
17 of trend.
18 As described in both exhibits, a
19 two-tailed hypothesis -- that is, a hypothesis
20 of no trend -- I have used the value of .1 just
21 for convenience purposes just to summarize and
22 tabulate the results. If one is asking the
23 question of whether or not there is an
24 increasing trend in phosphorus, then it is
DEPOSITION OF WILLIAM W. WALKER, JR.
904
1 appropriate to divide that significance level
2 in half so that we are actually talking about a
3 significance level of .05 for summarizing the
4 results with respect to a null hypothesis that
5 assumes that there is no increasing trend in
6 phosphorus.
7 But, as I stated earlier, the report
8 tabulates the actual P levels or the actual
9 significance levels that come out of the
10 Seasonal Kendall test, and they can be
11 interpreted by whoever wants to interpret them.
12 Q. In your interpretations, have you ever employed
13 the .05 significance level?
14 (The witness gave no response.)
15 Q. Well, Dr. Walker, in Exhibit 17 you report the
16 existence of trends, correct?
17 A. I report the likelihood of trends.
18 Q. Okay. In coming to that conclusion from your
19 analysis, what P level did you employ?
20 A. In tabulating the results, as I stated, I used
21 a P level of .1 for a two-tailed hypothesis,
22 which is equivalent to a P level of .05 for a
23 one-tailed hypothesis.
24 Q. A little bit farther down on page 6 of
DEPOSITION OF WILLIAM W. WALKER, JR.
905
1 Exhibit 7, the paragraph that starts "The test
2 data set includes 282 observations..." this
3 line in Exhibit 17 has the number 281.
4 MR. HARRISON: What page on 17, Counsel?
5 MS. AHEARN: Page 14.
6 Q. Can you explain the difference?
7 A. To my recollection, there was one sample that
8 was provided to us by the District that was
9 actually collected in October of 1989. We did
10 not have -- or I did not have the flow data or
11 the elevation data or the hydrologic data that
12 would correspond to that sample. And in the
13 draft analysis that is described in the
14 July 30th document, Exhibit No. 7, that sample
15 that was collected in October of 1989 I believe
16 was incorporated in the analysis in the final
17 version. Because I did not have the hydrologic
18 data for the October 1989 period, I excluded
19 that last sample and restricted the period as
20 described to December '77 through September of
21 1989, and that is the reason for the one-sample
22 decrease in the number of observations, which
23 had no significant effect on the results.
24 Q. Did you have to rerun all of the computer
DEPOSITION OF WILLIAM W. WALKER, JR.
906
1 programs?
2 A. Yes.
3 Q. What percentage of biweekly sampling values was
4 missing from the data that you obtained from
5 the District?
6 A. I don't recall.
7 Q. Was it as many as 15 percent?
8 A. I don't recall.
9 Q. Is it your understanding that 100 percent minus
10 a significance level is a confidence level?
11 A. I have seen it referred to as that, yes.
12 Q. Is that the definition you employ when you talk
13 about a confidence level?
14 A. Generally, yes.
15 Q. If you turn to page 16 in Exhibit 17, is it
16 accurate to say that the whole of the
17 correlation of hydrologic variables to
18 phosphorus concentration is less than the sum?
19 MR. HARRISON: Object to form.
20 Q. I just want to make sure I conceptualize this
21 properly as a layperson. For example, at the
22 top of page 16 you talk about regression
23 against elevation explaining 40 percent,
24 regression against antecedent rainfall
DEPOSITION OF WILLIAM W. WALKER, JR.
907
1 explaining 33.5 percent.
2 If you were to take these and other
3 hydrologic variables and figure out what
4 percentage of the phenomenon they individually
5 explain, you don't get their cumulative effect
6 by adding up those percentages, do you?
7 A. That would depend upon the particular data set
8 that you were analyzing. In some situations,
9 yes, you would get a cumulative -- you would
10 get a sum that would equal the components.
11 Q. Can you give me an example of a data set where
12 you would sum the components?
13 A. Well, you would never perform that sum. You
14 would always perform the regression analyses
15 just as I have done here.
16 Q. Can you give me the example where these
17 hydrologic variables wouldn't have that
18 overlapping effect?
19 A. In situations where the hydrologic factors such
20 as rainfall and water elevation in this example
21 are not correlated with each other. And if
22 their effects on the concentration are not
23 correlated with each other -- that is,
24 correlated between the hydrologic factors --
DEPOSITION OF WILLIAM W. WALKER, JR.
908
1 then you might approach an additive situation
2 such as you described.
3 Q. Do you have a real-world situation in mind
4 where that's the case?
5 A. That's rarely the case.
6 Q. The last sentence of this top paragraph on
7 page 16, you explained a reason for performing
8 your regressions as to generate a time series
9 of residuals which is statistically
10 independent.
11 Wouldn't it be more accurate to say that
12 this time series is uncorrelated?
13 A. Another way of describing it or stating it
14 would be to state that the objective is to
15 generate a time series of residuals which is
16 statistically uncorrelated with antecedent
17 rainfall and elevation for subsequent trend
18 testing. I don't know that stating it that way
19 is any more or less accurate than the way that
20 I have stated it using the word "independent."
21 Q. Are the residual values independent of the
22 hydrologic variables in a literal sense?
23 MR. HARRISON: Object to form.
24 A. In a statistical sense they are uncorrelated
DEPOSITION OF WILLIAM W. WALKER, JR.
909
1 and statistically independent of the hydrologic
2 factors because that is what would come out of
3 the regression analysis.
4 (Exhibit No. 39 marked for
5 identification)
6 Q. Dr. Walker, could you, please, identify
7 Exhibit 39?
8 A. These are graphs of total phosphorus
9 concentration, load and flow data from inflow
10 points to the Park.
11 Q. First I'd like to use this for illustrative
12 purposes. If we look at the first graph that
13 appears on page 1 here, you have a number of
14 data points plotted for I guess it's Period 2.
15 Those are the diamonds?
16 A. Correct.
17 Q. And then a regression line for that set of
18 data?
19 A. Correct.
20 Q. If I were to tell you that this diamond that
21 you have in the upper left-hand corner is in
22 error, in fact we have confirmed that there was
23 never any data collected on that day and you
24 should remove that from your analysis, under
DEPOSITION OF WILLIAM W. WALKER, JR.
910
1 that hypothesis -- hypothetical, excuse me, if
2 you were to make that change, would the
3 residuals for all other values for Period 2
4 change?
5 A. If you remove one data point from the graph,
6 would the other values change?
7 Q. The residuals.
8 A. Offhand I can't -- I don't understand how
9 removing one data point can change anything --
10 any of the other data points on the graph.
11 Q. Well, you've plotted concentration against flow
12 here, right? We're talking about actual
13 measurements?
14 A. Correct.
15 Q. And then the distance from each plotted point
16 from the regression line would be the residual?
17 A. Correct.
18 Q. If you remove this data point that I have
19 identified as being spurious, will your
20 regression line change? Will the slope of your
21 regression line change?
22 A. If you repeat the regression?
23 Q. Do whatever recalculations you feel are
24 appropriate.
DEPOSITION OF WILLIAM W. WALKER, JR.
911
1 MR. HARRISON: Object to form.
2 A. I don't know what you're asking, so I don't
3 know what's appropriate. I can't see why
4 removing one data point is going to change
5 other data points.
6 Q. Let me try and rephrase it one more time
7 because I think I just had a hard time
8 communicating this thought to you.
9 If we were to remove this spurious data
10 point and you were then to refit the regression
11 line to the corrected data set, would the
12 residuals calculated from that new regression
13 line change, the regression value associated
14 with each particular data point which I'm not
15 changing that are plotted on this graph?
16 A. Well, if you had a hypothetical sample such as
17 that and you hypothetically removed it and you
18 hypothetically fit a new regression line, then
19 there would be -- there may be some effect on
20 the residuals from the other data points,
21 that's correct.
22 Q. So in my hypothetical the residuals of the
23 values in Period 2 are statistically
24 interdependent with the erroneous data value
DEPOSITION OF WILLIAM W. WALKER, JR.
912
1 point -- if I change that, I change the rest?
2 A. The regression line would not necessarily
3 change upon removing a particular data point.
4 Q. Well, in my hypothetical here when I'm going to
5 remove this --
6 A. Well, I don't understand what -- what the point
7 of a hypothetical removal of a hypothetical
8 data point is.
9 Q. Just to try and discuss a concept. That's
10 okay. Let's get back to specifics.
11 Why did you generate Exhibit 39?
12 MR. HARRISON: I don't believe that's
13 been established. Maybe it has. I can't
14 remember hearing him identify it. Maybe that's
15 my problem.
16 Q. You have identified this as being a document
17 you produced, correct?
18 A. I don't think I've identified that for the
19 record.
20 Q. Is this your handwriting on it?
21 A. Yes, it is.
22 Q. Is this a document you produced?
23 A. Yes.
24 Q. Okay. Why?
DEPOSITION OF WILLIAM W. WALKER, JR.
913
1 A. This was a sort of an exploratory or
2 supplementary analysis that I did just to
3 examine the relationships between
4 concentration, flow and load, phosphorus load,
5 at each structure for different time periods.
6 Q. At what time did you perform this analysis?
7 A. I don't recall. It would have been probably in
8 1990 sometime.
9 Q. Did you generate Exhibit 39 in conjunction with
10 the analyses which are the basis for
11 Exhibit 17?
12 A. I generated this exhibit using the same data
13 that are used in Exhibit 17, but I wouldn't say
14 that I generated it in conjunction with that
15 exhibit.
16 Q. Did you rely on Exhibit 39 for purposes of
17 performing the analyses reflected in
18 Exhibit 17?
19 A. Well, the results shown in Exhibit 39 are
20 generally consistent with those found and
21 described in Exhibit 17 in that they support or
22 suggest the presence of higher phosphorus
23 concentrations at a given flow and higher
24 phosphorus loadings at a given flow at these
DEPOSITION OF WILLIAM W. WALKER, JR.
914
1 structures when one compares the early part of
2 the record which I identify in Exhibit 39 as
3 Period 1, the first five years of data, and the
4 remaining portion of the record identified as
5 Period 2. In other words, the -- excuse me,
6 the phosphorus concentrations were higher in
7 Period 2 as compared with Period 1.
8 Q. On each page here in Exhibit 39 do these
9 reflect separate regression analyses, for
10 example, where you would fit the regression
11 line to the concentration data and then perform
12 a separate calculation for load?
13 A. During each period a separate regression is fit
14 between concentration and flow or between load
15 and flow.
16 Q. Are you aware that the regression equation for
17 load could have been derived exactly from those
18 for concentration?
19 A. Well, they're essentially the same thing,
20 that's correct.
21 Q. The reference here to "Method: 6 REG-3," what
22 does that mean?
23 A. That essentially identifies a particular method
24 for representing the relationship between
DEPOSITION OF WILLIAM W. WALKER, JR.
915
1 concentration and flow, and that particular
2 method is to regress concentration against
3 flow.
4 Q. The concentration values that you have plotted
5 here, are those flow-weighted?
6 A. These are individual sample values, and on
7 page 1 here we're looking at data from S12T,
8 which is the composite cross session for S12A,
9 B and C.
10 Q. On page 2, the bottom graph, what does the
11 reference "Method: 7 MULTI" refer to?
12 A. That would refer to an alternative way of
13 representing the concentration or load versus
14 flow relationship. But in this example I
15 believe that the way I applied that alternative
16 method, it would be essentially the same as
17 simply regressing concentration against flow
18 for each of the two time periods.
19 Q. On the third page of Exhibit 39, what does
20 "Method: 2 Q WTD C" refer to?
21 A. That means essentially instead of correlating
22 concentration against flow for this particular
23 station, that correlation was not significant.
24 So "2 Q WTD C" is just -- in that situation we
DEPOSITION OF WILLIAM W. WALKER, JR.
916
1 are representing the concentration as merely
2 the flow-weighted average concentration for the
3 entire data set for the entire time period.
4 Q. Are these graphs on the log scale?
5 A. That's correct.
6 Q. Is that true for each page of Exhibit 39? If
7 you could just point out any graphs that aren't
8 on the log scale.
9 A. I believe they're all on log scales.
10 Q. How did you determine how to split your
11 Period 1 and Period 2?
12 A. Period 1 was essentially the first five years
13 of data that we had used in the ONRW
14 discussions and have used in developing the
15 interim standards for the federal remedy to the
16 lawsuit as a baseline period for developing
17 standards.
18 Q. How about for Taylor slough and the Coastal
19 Basin? How did you decide where to cut the
20 data there?
21 A. I believe I attempted to cut the data set
22 approximately in half.
23 Q. Were you surprised when you saw a decreasing
24 trend in nitrogen?
DEPOSITION OF WILLIAM W. WALKER, JR.
917
1 A. I did not anticipate a decrease in the trend in
2 nitrogen.
3 Q. On page 17, paragraph numbered 3, you state
4 that increases in nutrient concentrations have
5 been observed. By "nutrient concentrations"
6 there, do you include both phosphorus and
7 nitrogen?
8 A. At least with reference to that particular
9 report by Worth, 1988, I don't recall whether
10 his work documents such changes in nitrogen,
11 but I know that I was at least referring to
12 phosphorus. Whether I was also including
13 nitrogen as part of that, I don't recall.
14 Q. Does leaching from plant detritus, increased
15 peat mineralization and concentration by
16 evaporation as a general matter commonly lead
17 to increased nitrogen concentrations?
18 MR. HARRISON: I object to form.
19 A. Not necessarily.
20 Q. Does it in some instances and not others?
21 A. It would depend upon the relative magnitudes of
22 the nitrogen sources and sinks in a particular
23 environment.
24 Q. In the Everglades does the leaching of plant
DEPOSITION OF WILLIAM W. WALKER, JR.
918
1 detritus lead to increases in nitrogen
2 concentrations?
3 MR. HARRISON: Increases --
4 A. It is very hard to generalize about that on
5 nitrogen.
6 Q. In Water Conservation Area 2A during the water
7 level drawdown, do you know whether the
8 phenomenon you report here in this Paragraph 3
9 increased nitrogen concentrations?
10 A. I don't recall specifically.
11 Q. Does the term "hydroperiod" have a specific
12 meaning for you?
13 A. It has a general meaning.
14 Q. And what does that term mean to you?
15 A. It would mean that portion of the year at which
16 there is standing water at a given location.
17 Q. Have you ever heard the term "hydroperiod" used
18 to refer to the combined pattern of timing,
19 duration and volume of water at a given
20 location?
21 A. Well, I suppose that the term may have
22 different meanings for different people but --
23 Q. Do you know how the term is usually used in the
24 context of the Everglades?
DEPOSITION OF WILLIAM W. WALKER, JR.
919
1 MR. HARRISON: Object to form. Usually
2 by whom?
3 Q. Do you know how the term is usually used among
4 scientists who have studied the Everglades?
5 A. I have given the definition that I would
6 normally ascribe to the term. I don't know.
7 Other people may have other versions of that
8 definition.
9 Q. Dr. Walker, rather early in Exhibit 17 you make
10 the case for the modified -- the second version
11 of the Seasonal Kendall test because it
12 accounts for serial correlation.
13 Why did you continue your analysis and
14 report your analysis for both versions, that
15 with and without serial correlation?
16 A. Well, first of all, because there were some
17 differences of opinion within the statistical
18 community as we discussed regarding, for
19 example, Mr. Loftis' opinion regarding the fact
20 that this version of the test using serial
21 correlation is too conservative and would,
22 therefore, miss trends and should not be used,
23 I felt that reporting both versions of the test
24 would provide as complete a picture as possible
DEPOSITION OF WILLIAM W. WALKER, JR.
920
1 regarding the probability of trends.
2 And the other important factor is that
3 the version of the test that accounts for
4 serial correlation is -- has been shown to be
5 conservative -- that is, to be probable of
6 missing trends, especially in time series that
7 are less than ten years in length. And two of
8 the time series that I'm examining here, S18C
9 and S332, have durations on the order of six
10 years.
11 So the trend magnitudes estimated by the
12 second test -- not the trend magnitude but the
13 significance levels may be overestimated by the
14 test in those examples.
15 Q. In formulating your opinions concerning the
16 South Florida litigation, will you be relying
17 on both versions of the Seasonal Kendall test?
18 MR. HARRISON: Object to the form of the
19 question.
20 A. I will be relying on all the information and
21 all the analyses that I have conducted. That
22 will include both versions of the Seasonal
23 Kendall test.
24 Q. Is that true also for your trend analyses of
DEPOSITION OF WILLIAM W. WALKER, JR.
921
1 Park marsh stations?
2 A. Yes.
3 Q. And how about the inflows and outflows to the
4 Water Conservation Areas?
5 A. I plan to conduct the tests as I have begun to
6 conduct the tests using both versions of the
7 test, and I will interpret the results based
8 upon the results and upon the applicability of
9 the different tests to each situation.
10 Q. Am I correct, I understood you a couple days
11 ago to tell us that you had performed a
12 preliminary analysis that included both water
13 conservation inflows and outflows and marsh
14 data? Am I correct?
15 A. I have done preliminary analyses on each of
16 those data sets, correct.
17 Q. Did you do independent analyses?
18 A. There are separate data sets, yes.
19 Q. Will you be doing further analyses of the Water
20 Conservation Area marsh data?
21 MR. HARRISON: Asked and answered.
22 A. I don't believe we have talked at all about
23 Water Conservation Area marsh data.
24 Q. Then I am wrong. Let me back up.
DEPOSITION OF WILLIAM W. WALKER, JR.
922
1 I had thought you had told us that you
2 had performed a preliminary analysis of Water
3 Conservation Area inflow/outflow and Water
4 Conservation Area marsh data. Is that correct?
5 A. No, that's not correct.
6 Q. Have your marsh analyses been restricted only
7 to Park marsh stations?
8 A. That's correct.
9 Q. Do you anticipate performing analyses of Water
10 Conservation Area marsh stations?
11 A. I have requested such data from the District,
12 but I am not sure at this point as to whether I
13 will be actually conducting a trend analysis of
14 that information. It would depend upon the
15 extent of the data.
16 Q. When did you request this data?
17 A. Within the last month it was requested through
18 the Justice Department.
19 MS. AHEARN: Okay. Good time to stop
20 for lunch.
21 (Luncheon recess)
22
23
24
DEPOSITION OF WILLIAM W. WALKER, JR.
923
1 A F T E R N O O N S E S S I O N
2 (Exhibit Nos. 40 through 55 marked for
3 identification)
4 BY MS. AHEARN:
5 Q. Dr. Walker, you have before you Exhibits 40
6 through 55 to your deposition. Could I ask you
7 to, please, take those up one by one, state the
8 exhibit number and identify each document?
9 A. Exhibit 40 is some pages of graphs entitled
10 Yearly Total P Concentrations and Loads at ENP
11 Inflows.
12 Q. And is that a document which you created?
13 A. Yes.
14 Q. Exhibit 41 is a mixture of tables and figures
15 identified on the first page with the title
16 Excluding Outliers, Inflow Samples With Flow
17 Greater Than Zero.
18 Q. Is 41 also a document that you created?
19 A. Well, it's a mixture of documents that I have
20 created at one point or another. They're not
21 necessarily related to each other.
22 Exhibit 42 is a table entitled Summary
23 - ENP Inflows, December 29, 1989. This also
24 appears to be a table that I created.
DEPOSITION OF WILLIAM W. WALKER, JR.
924
1 Exhibit 43 is a table entitled ENP
2 Flow-Weighted Mean Concentrations, December 30,
3 1989. This is also a table that I created.
4 Exhibit 44 is another table entitled
5 Water Quality Summary - ENP Marsh Stations Not
6 Flow-Weighted, December 29, 1989. I created
7 this table.
8 Exhibit 45 is a series of tables
9 entitled ENP Marsh Data - Trend Analysis - All
10 Results By Station, which I created.
11 Exhibit 46 is another set of tables
12 which I created entitled ENP Marsh Data - Trend
13 Analysis - All Results For Variable = DO.
14 Q. For sake of clarity, could you also identify
15 the variables reflected on pages 2 and 3?
16 A. Okay. Exhibit 46, the first contains results
17 for variable = do. The second page contains
18 results for variable = tntp. And the third
19 page contains results for variable = tp.
20 Exhibit 47 is a plot of total phosphorus
21 against stage for ENP Marsh Station P35.
22 Exhibit 48 is a plot of total phosphorus
23 concentration against stage for Station P36.
24 Exhibit 49 is a memo to Geoff Garver of
DEPOSITION OF WILLIAM W. WALKER, JR.
925
1 the Justice Department from myself dated
2 November 14, 190.
3 Q. Dr. Walker, is Exhibit 49 the request for WCA
4 marsh data which you told us about just before
5 we broke for lunch?
6 A. No.
7 Q. Okay.
8 A. Exhibit 50 is a single page dated January 7,
9 1991, entitled Data Needs: Supplement to
10 November 9, 1991, Memo to Geoff Garver.
11 Q. Is this the request for marsh data?
12 A. I don't know whether this particular document
13 was forwarded to the District as part of a
14 request for data. But this --
15 Q. Is this the request that you made for the data?
16 A. To supplement this particular request, there
17 were additional materials that I submitted to
18 the Justice Department that I do not have a
19 copy of.
20 Q. All right. Exhibit 51, your counsel pointed
21 out, is a composite exhibit. Could you,
22 please, identify it by page?
23 (The witness gave no response.)
24 Q. Have you seen page 1 of Exhibit 51 before?
DEPOSITION OF WILLIAM W. WALKER, JR.
926
1 A. I don't recall having seen this document
2 before.
3 Q. Did you originate a request for the USGS to
4 retrieve water quality data prior to the date
5 of this letter, June 29, 1989?
6 A. No, I did not.
7 Q. Do you know if the data which Mr. Higer
8 references here in his letter has been used by
9 you in the work you have done on the South
10 Florida matter?
11 A. I'm not familiar with this particular data
12 request, and I have not seen the floppy disks
13 or the data that are referenced in this
14 particular request, and I have not utilized the
15 data.
16 Q. Okay. Can you identify page 2 of Exhibit 51?
17 A. Page 2 is a letter from Carolyn Price of the US
18 Geological Survey, Miami, to myself dated
19 November 27, 1989. Page 3 of Exhibit 51 is a
20 copy of a letter to Carolyn Price from myself
21 dated December 6th of 1989.
22 Q. Dr. Walker, did you receive a response to your
23 letter of December 6th to Carolyn Price?
24 A. I recall working with Carolyn Price during
DEPOSITION OF WILLIAM W. WALKER, JR.
927
1 December of 1989 to essentially clear up the
2 discrepancies in the flow data that are
3 referenced in this letter. I don't recall
4 whether I received the written response from
5 her letter.
6 MS. AHEARN: Off the record.
7 (Off the record)
8 Q. And pages 4 and 5 of Exhibit 51?
9 A. Pages 4 and 5 appear to be copies of a letter
10 from Daniel Scheidt to Carolyn Price of the
11 USGS dated October 20th of 1988.
12 Q. Have you seen this letter before?
13 A. Not to my recollection.
14 Q. Have you received the water quality data
15 Groups 1 and 2 for the parameters referenced in
16 this letter from Mr. Scheidt?
17 A. I don't recall having received any data
18 organized in this way.
19 MR. HARRISON: Let the record reflect
20 that pages 4 and 5, the alleged letter from
21 Mr. Scheidt to Ms. Price, October 20, 1988,
22 does appear to be unsigned and there is no
23 letterhead. I don't think there's been a
24 foundation laid as to whether or not that
DEPOSITION OF WILLIAM W. WALKER, JR.
928
1 letter was ever sent.
2 MS. AHEARN: That's fine, Mr. Harrison.
3 I'm just using it as a frame of reference to
4 these USGS things.
5 Q. Have you ever requested of USGS data using
6 these codes or a similar format?
7 MR. HARRISON: The format contained on
8 page 4 of Exhibit 51, Counsel?
9 MS. AHEARN: Yes.
10 A. I have not requested an identical retrieval,
11 but I have requested data from the USGS.
12 Q. Were you aware at the time you made your
13 request that any prior request by personnel at
14 the Park had been made to USGS for water
15 quality data?
16 MR. HARRISON: Object to form.
17 (The witness gave no response.)
18 Q. What I'm trying to get at, Dr. Walker, is:
19 Did you have to go back to USGS to ask for data
20 because you weren't aware that the Park had
21 USGS data, or did they just not have the data
22 still that you needed from the USGS?
23 MR. HARRISON: Object to form.
24 A. I don't recall any -- having ever seen this
DEPOSITION OF WILLIAM W. WALKER, JR.
929
1 letter of October 20th, 1988, or having seen
2 any reference to this previous request to the
3 USGS for data on the part of the Park.
4 Q. When you subsequently made requests of the USGS
5 for water quality data, had you made prior
6 attempts to obtain that data from the Park?
7 A. I may have discussed with Dan Scheidt the
8 concept of acquiring the USGS data, but I don't
9 recall specifically.
10 Q. Do you recall whether Mr. Scheidt told you that
11 he could provide USGS water quality data?
12 A. I don't recall his having said that to me, no.
13 Q. Okay. Can you identify Exhibit 52?
14 A. Exhibit 52 is a one-page memo to Clint Leaks of
15 the USGS in Miami from myself.
16 Q. Did you send this memo to Clint Leaks?
17 A. Yes, I did. I faxed it.
18 Q. Do you recall approximately when this would
19 have occurred?
20 A. The summer of 1990.
21 Q. And did you receive the data that you request
22 here in Exhibit 52?
23 A. Yes, I did.
24 Q. In what form did you receive that data?
DEPOSITION OF WILLIAM W. WALKER, JR.
930
1 A. I received it in the form of a -- one or more
2 floppy disks.
3 Q. And when did you receive the data from USGS?
4 A. In the summer of 1990.
5 Q. Do you recall if it was before or after you
6 prepared Exhibit 7, the July 3 draft of the
7 trends paper?
8 A. I believe it was after.
9 Q. Have you performed any trend analyses of the
10 data obtained from USGS?
11 A. No.
12 Q. Now, does USGS have permanent sampling stations
13 within the latitude and longitude coordinates
14 you have referenced here in the letter?
15 A. What do you mean by "permanent"?
16 Q. What sampling locations were you including by
17 specifying these latitude and longitude
18 coordinates in the request?
19 A. I don't recall the exact boundaries of these
20 coordinates, but it -- I believe that my intent
21 was to include the stations that would be
22 located along the Tamiami Trail as well as
23 stations that would be located within the Park.
24 Q. Did you include Water Conservation Area 3A?
DEPOSITION OF WILLIAM W. WALKER, JR.
931
1 A. I don't recall whether Water Conservation
2 Area 3A was included in here or not.
3 Q. Do you recall whether you included the other
4 two Water Conservation Areas?
5 A. Like I said, I don't recall the exact bounds of
6 the latitude and longitude coordinates in
7 reference to the map.
8 Q. Could I have you turn to Exhibit 32, please.
9 Keep 52 before you, but if you could turn to
10 Exhibit 32, the fourth page of that exhibit,
11 In your Exhibit 52, the request to Clint
12 Leaks, within the parentheses we first see a
13 four-digit number. Does that number reflect
14 the four digits of the six-digit numbers found
15 under the column LAT in Exhibit 32?
16 A. I'm afraid that you're ahead of me because I
17 haven't found Exhibit 32 yet.
18 Q. I'm sorry.
19 MR. HARRISON: What page on 32,
20 Ms. Ahearn?
21 MS. AHEARN: Page 4.
22 Q. Dr. Walker, I'd be happy to hand you a copy of
23 Exhibit 32. Please turn to page 4.
24 A. Would you repeat the question, please?
DEPOSITION OF WILLIAM W. WALKER, JR.
932
1 Q. You specified the latitude and longitude
2 coordinates within parentheses here. The first
3 entry is a four-digit number. Am I correct
4 that the proper way to determine what sampling
5 station this refers to is to match that with
6 the first four digits of the six-digit numbers
7 that appear under the latitude column?
8 A. We were not attempting to precisely match
9 coordinates in conducting this retrieval.
10 Q. I see. Does this just signify four points and
11 you would ask for any water samples collected
12 within that specified area?
13 A. That's correct.
14 Q. I'll have to get a map, I guess, to figure out
15 what that means.
16 Can you identify Exhibit 53?
17 A. Exhibit 53 is entitled Meeting Agenda on the
18 subject of access to technical data maintained
19 on District computers, Thursday, October 5,
20 1989.
21 Q. And the pages attached?
22 A. The second page is -- appears to be a map with
23 the title Access to the South Florida Water
24 Management District Hydrologic Data Base.
DEPOSITION OF WILLIAM W. WALKER, JR.
933
1 Q. Did you attend the meeting referenced here
2 October 5, 1989?
3 A. Yes, I did.
4 Q. Did you receive these attached pages at that
5 meeting?
6 A. No, I don't think so.
7 Q. Let me represent to you, Dr. Walker, that this
8 is an item that was provided from the U.S.
9 attorney as a copy of a document from your
10 files produced for purposes of this deposition.
11 If you can tell me what your source for
12 the attachments to the meeting agenda are,
13 please?
14 A. I believe I would have obtained those two pages
15 from the staff at the ENP Research Center --
16 the three pages attached to Exhibit 53.
17 Q. Can you identify the third page of Exhibit 53?
18 A. The third page is a -- it appears to be a
19 listing of flow data entitled Example of Output
20 with FORMAT 1.
21 Q. You're looking at the third attachment, the
22 fourth page of the exhibit?
23 A. I'm looking at the fourth page of the exhibit.
24 Q. Could you identify the third page of the
DEPOSITION OF WILLIAM W. WALKER, JR.
934
1 exhibit, please? It's entitled "Getting
2 Started."
3 A. "Getting Started" is another page of material
4 that I believe I received from the Park staff
5 of the Research Center.
6 Q. What is the "Cyber" referenced in "Getting
7 Started"?
8 A. I believe it's reference to a computer.
9 Q. And where is that computer located?
10 A. I don't know.
11 Q. The handwriting at the bottom of this page, is
12 that yours?
13 A. No.
14 Q. Do you know whose handwriting that is?
15 A. No.
16 Q. Have you accessed a Cyber computer in the
17 course of your work on the South Florida
18 matter?
19 A. I have accessed the particular database that is
20 referenced on this page. Yes, I have.
21 Q. Did you use this procedure that's described in
22 the handwritten notations?
23 A. I believe so.
24 Q. And you did this from your personal computer in
DEPOSITION OF WILLIAM W. WALKER, JR.
935
1 Massachusetts?
2 A. That's correct.
3 Q. On how many occasions have you done that?
4 A. I don't recall.
5 Q. Has it been in excess of ten occasions?
6 A. I don't recall the number of times that I've
7 accessed the computer.
8 Q. Can you identify Exhibit 54, please?
9 A. Exhibit 54 is a letter from -- is a copy of a
10 letter from Mary Lou Daniel of South Florida
11 Water Management District to Dan Scheidt of ENP
12 Research Center dated December 13th, 1989, and
13 attached to that letter are four pages of what
14 appears to be a list of test procedures.
15 Q. Have you seen this letter and attachments
16 before?
17 A. I believe so, yes.
18 Q. Did you originate a request for Mr. Scheidt to
19 obtain this information from the District?
20 MR. HARRISON: Object to form.
21 A. I may have. I don't recall.
22 Q. If you did, what was your purpose in
23 originating this request?
24 MR. HARRISON: Objection, Counsel.
DEPOSITION OF WILLIAM W. WALKER, JR.
936
1 Unless there's a predicate laid, it's a little
2 premature to ask him a question about something
3 he doesn't remember.
4 Q. You said you may have. So you're saying yes,
5 you might have done that.
6 If you did, what would have been your
7 purpose?
8 MR. HARRISON: Objection. Calls for
9 speculation.
10 A. I don't know whether I even originated this
11 request. I can't -- I can't answer your
12 question.
13 Q. Have you utilized or relied on the information
14 found in Exhibit 54 in the course of the work
15 you have done on the South Florida matter?
16 MR. HARRISON: Let the record indicate
17 he hasn't seen it yet. He has to take time to
18 read it.
19 MS. AHEARN: I would represent for the
20 record that this is a document provided by the
21 US Attorney's Office as a copy of the document
22 from Dr. Walker's files.
23 MR. HARRISON: Fine. Ask him if he
24 recalls seeing it.
DEPOSITION OF WILLIAM W. WALKER, JR.
937
1 MS. AHEARN: He has already answered
2 that question affirmatively, Mr. Harrison.
3 MR. HARRISON: Okay. I'm sorry. If
4 that's the case, I didn't hear it.
5 (Witness examining document)
6 A. This document provides a reference on the
7 analytical methods that are used by the
8 District in their water quality analyses, and
9 it is useful as background information for the
10 purposes of the analysis that I have conducted.
11 Q. Would you identify Exhibit 55, please?
12 A. Exhibit 55 is a single page entitled Trends at
13 Other WCA Stations.
14 Q. Did you author this exhibit?
15 A. Yes.
16 Q. Do you recall when you authored this?
17 A. The late summer or early fall of 1990.
18 Q. Does Exhibit 55 reflect the current status of
19 your preliminary analysis of trends in and
20 around the Water Conservation Areas?
21 A. What do you mean by "around"?
22 Q. Have you performed any substantial amount of
23 work on your analysis of the water
24 concentrations at monitoring stations in and
DEPOSITION OF WILLIAM W. WALKER, JR.
938
1 around the Everglades Water Conservation Areas
2 since the time you prepared Exhibit 55?
3 A. No, not to my recollection.
4 Q. When you used the term "around" in the first
5 sentence of Exhibit 55, what does that mean
6 there?
7 A. The intent here was to indicate that these are
8 stations at the inflows and outflows from the
9 Everglades Water Conservation Areas.
10 Q. Dr. Walker, yesterday we asked you about
11 various opinions you formulated concerning
12 water quality in South Florida, and you
13 referred to preliminary analyses of Everglades
14 marsh data that show certain trends at certain
15 stations are likely. Is that accurate? Is
16 that what your testimony was yesterday?
17 A. The preliminary analysis has identified trends
18 in phosphorus and other constituents at certain
19 marsh stations.
20 Q. Do Exhibits 43 through 46 represent this
21 preliminary analysis of Park marsh data?
22 A. They would include the preliminary analysis of
23 the marsh data.
24 Q. Are there analyses, printouts more recent than
DEPOSITION OF WILLIAM W. WALKER, JR.
939
1 Exhibits 44, 45 and 46 concerning your analysis
2 of ENP marsh data?
3 A. All of the analyses and all of the printouts on
4 this topic were included in the materials which
5 I turned over to the Justice Department. I
6 believe that those materials are reflected
7 here.
8 Q. You believe that 44 through 46 are the most
9 recent printouts?
10 MR. HARRISON: Counsel, you said 44.
11 A. I --
12 Q. Dr. Walker, you know, if you're right and
13 everything was in the documents handed over to
14 the Department of Justice, that's great. I
15 just wanted to make sure that I have been able
16 to pull out the most relevant documents to
17 discuss with you here.
18 I'm hampered because they aren't clearly
19 dated, and I have tried to look for what looks
20 like the most finished product. And if we
21 discover that there's something more current,
22 wonderful, we'll introduce it. But I just want
23 to get your sense on whether I'm dealing with
24 the most relevant stuff here.
DEPOSITION OF WILLIAM W. WALKER, JR.
940
1 MR. HARRISON: The pending question is,
2 Is this the most recent marsh data analysis
3 that he has performed?
4 MS. AHEARN: Yes. Does Dr. Walker
5 believe that these are the most recent
6 analyses?
7 A. These include the most recent analyses, yes.
8 Q. There would be others?
9 A. These include the most recent analyses.
10 Q. I see. Okay. We'll work through these.
11 With reference back to Exhibit 17, we
12 were on page 19. I want to take an opportunity
13 to identify them all at once. We can get the
14 documents distributed during lunch and
15 hopefully expedite things. I think we'll also
16 incorporate those exhibits as we work through
17 this.
18 So on page 19 of Exhibit 17, I'd like to
19 direct your attention to the first paragraph
20 there. I'd also like to direct your attention
21 to the corresponding paragraph in the July 3
22 draft, Exhibit 3. And you'll find that at the
23 bottom of page 7.
24 MR. HARRISON: Where are we now,
DEPOSITION OF WILLIAM W. WALKER, JR.
941
1 Counsel? Paragraph 3 of 17?
2 MS. AHEARN: Exhibit 17, page 19, top
3 paragraph.
4 MR. HARRISON: Oh, I'm sorry. On
5 page 19.
6 MS. AHEARN: And the corresponding entry
7 in Exhibit 7 is page 7, bottom paragraph.
8 Q. A layman reviewing these two versions of the
9 report, probably the one thing they will
10 understand is that various numbers are changed
11 from one to the other.
12 Could I ask you to please explain why
13 these numbers changed? And to expedite things,
14 I'd ask that you just take the values that
15 change in sequence as we go through the
16 paragraph.
17 MR. HARRISON: Object to form.
18 Q. The first would be a 2.8 value in Exhibit 7
19 appears as 1.7 in Exhibit 17.
20 MR. HARRISON: Object to form, Counsel.
21 I think it would be more proper to ask the
22 doctor whether in fact it compares rather than
23 you stating that it does with no foundation.
24 MS. AHEARN: Well, I think it's
DEPOSITION OF WILLIAM W. WALKER, JR.
942
1 pretty --
2 MR. HARRISON: It may constitute a
3 different analysis, too, that may not be
4 comparable. That's all I'm saying.
5 MS. AHEARN: Well, that's the whole
6 point here. I'm just asking him --
7 Q. Dr. Walker, is it true that one version of the
8 draft, Exhibit 7, contains the value 2.7 and
9 that value is -- 2.8, excuse me, and that value
10 is 1.7 in Exhibit 17?
11 A. That's correct. It is stated as such in the
12 text.
13 Q. Why is the number in the text different?
14 A. Well, as we discussed earlier, the first
15 version, the draft, used flow and water
16 elevation in the Series C results -- that is,
17 the results accounting for hydrologic factors.
18 The second series of tests used antecedent
19 rainfall and water elevation as a basis for
20 adjusting the phosphorus concentrations for
21 hydrologic variations. And I believe that the
22 difference is that we are looking at here with
23 respect to this 1.7 versus --
24 Q. 2.8.
DEPOSITION OF WILLIAM W. WALKER, JR.
943
1 A. -- 2.8 reflects days in the methodology used in
2 Series C that we have already discussed.
3 Q. Great. I don't mean this to be an exercise to
4 have you explain things we have already gone
5 through, but just if you can identify -- we
6 have discussed so many things. If you can
7 identify what it is that would have affected
8 each of these numbers, that would be fine.
9 MR. HARRISON: Counsel, the preceding
10 sentence in both reports just prior to the
11 numbers you just asked about clearly explain
12 the difference that we just had to go through
13 with Dr. Walker's answer -- I mean, that one is
14 with flow and one is with rainfall.
15 MS. AHEARN: Mr. Harrison, if you're
16 such an expert that you can figure all that
17 out, I'm impressed.
18 MR. HARRISON: If you look at the
19 parenthetical phrases in both of those
20 sentences beginning with "A positive trend..."
21 one clearly says "(original data and elevation/
22 rainfall residual)" in Exhibit 17, and
23 Exhibit 7 says "(original data and
24 flow\elevation residual)." I'm just trying
DEPOSITION OF WILLIAM W. WALKER, JR.
944
1 to --
2 MS. AHEARN: I'm just not comfortable,
3 Mr. Harrison, presuming, given my very limited
4 knowledge of this, that the change in the first
5 sentence is the full explanation of the change
6 in the second sentence. I think we can really
7 expedite this if Dr. Walker can just say: This
8 change reflects change in the water variables.
9 The next change represents a correction of the
10 database, what have you. That's all I'm
11 looking for here.
12 MR. HARRISON: Fine.
13 MS. AHEARN: Thank you.
14 MR. BURGESS: Or just swear
15 Mr. Harrison.
16 MS. AHEARN: Okay.
17 (Laughter)
18 (Off the record)
19 A. Well, with respect to the remaining differences
20 between these two paragraphs, which are
21 generally small, I believe that they reflect
22 basically two differences between the analysis
23 that was conducted to support the first draft
24 in July and the analysis that was conducted to
DEPOSITION OF WILLIAM W. WALKER, JR.
945
1 support the final draft in September.
2 We just discussed the first reason as
3 being related to and pertaining to Series C
4 only, and that is the fact that in July I used
5 flow and water elevation as hydrologic factors
6 and in the September draft I used rainfall and
7 water elevation with some additional
8 consideration of lag time.
9 And the other factor which likely
10 accounts for the differences -- the small
11 differences in these numbers for the other
12 series reflects that as I recall in the July
13 draft, I was using a slightly different
14 definition of "season" in defining the -- in
15 applying the Seasonal Kendall test.
16 Q. Okay. And what do you mean by "a slightly
17 different definition"?
18 A. In the July draft I recall that the
19 observations were classified according to
20 season just based upon the calendar month,
21 January, February, March and so forth, in which
22 the observations fell.
23 In the September draft, after looking at
24 some additional materials and reviewing a
DEPOSITION OF WILLIAM W. WALKER, JR.
946
1 computer program that we discussed earlier, the
2 program by Crawford et al., I used -- the
3 definition of "season" was refined to include
4 periods of exactly equal length -- in other
5 words, 12 seasons -- so that they each had the
6 exact same length in terms of number of days as
7 compared with just using the calendar months.
8 I don't know that it makes much
9 difference one way or the other which
10 particular method one uses for defining these
11 seasons, but I wanted to use the second -- I
12 decided to use the second method just to be
13 consistent with the way that the USGS had
14 defined seasons in their computer program.
15 Q. Thanks. A few things make a little more sense
16 now.
17 Does that redefinition of "season"
18 explain the difference between the two versions
19 of Table 2 in Exhibit 17 on page 18 if you look
20 under the test concentrations for Series B and
21 compare that with Table 2 in Exhibit 7?
22 MR. HARRISON: What page is that on,
23 Counsel, on Exhibit 7?
24 MS. AHEARN: They're in the back. They
DEPOSITION OF WILLIAM W. WALKER, JR.
947
1 aren't included in the paginated text.
2 MR. HARRISON: All right.
3 Q. For example, the test concentration values for
4 February, March and April? Am I correct, was
5 it the redefinition of "season" that caused one
6 value to move from April into March?
7 A. That may have occurred, correct.
8 Q. Are there any other changes of which you are
9 aware that would explain the difference in the
10 numbers of test concentrations?
11 A. Not that I can recall.
12 Q. I refer you to page 8 on Exhibit 7, again the
13 numbers in the first full paragraph here.
14 Would changes from these numbers in this
15 version to the final report reflect the two
16 factors that you have just described in the
17 foregoing paragraph?
18 A. To the best of my recollection, those would be
19 the only two factors that would be different.
20 Q. In the next paragraph appearing in the middle
21 of page 8, Exhibit 7, there are a number of
22 statements which do not appear in Exhibit 17.
23 If you would like to turn to that, it starts on
24 page 19, the bottom of that page. First let me
DEPOSITION OF WILLIAM W. WALKER, JR.
948
1 back up into the body of the foregoing
2 paragraph.
3 Midway in that paragraph is a sentence
4 that starts "If we interpolate between these
5 limits..." Do you see where I am? First full
6 paragraph, page 8, Exhibit 7.
7 A. Yes.
8 Q. The next phrase, "and assume a first-order
9 autoregressive process," that phrase does not
10 appear in Exhibit 17. Is there any particular
11 reason why that phrase was deleted?
12 MR. HARRISON: Object to form.
13 A. I don't have any particular reason or any
14 recollection.
15 Q. Does Exhibit 17 also assume a first-order
16 autoregressive process?
17 A. It assumes the process structure that was used
18 in -- by Hirsch and Slack in generating their
19 table that I'm referring to here.
20 Q. The following paragraph on page 8, the second
21 sentence, the phrase "and thereby increases
22 power for trend detection," that phrase does
23 not appear in Exhibit 17. Again, is there a
24 specific reason why it was dropped?
DEPOSITION OF WILLIAM W. WALKER, JR.
949
1 MR. HARRISON: Object to counsel's
2 characterization.
3 A. It really was not dropped. If you look -- if
4 you actually read the paragraph in Exhibit 17,
5 there's essentially an equivalent statement
6 starting on the bottom of page 19 that says:
7 First, it reduces concentration
8 variance by 43.2%. Second, it reduces
9 residual serial correlation from .66 to
10 .29. Both of these impacts would be
11 expected to increase power for trend
12 detection.
13 So the reference to increasing the power
14 for trend detection is contained in both of the
15 documents.
16 Q. So a statistician reading the final would know
17 that that indicates increased power for trend
18 detection?
19 A. I don't know whether it would require a
20 statistician or not. The statement that these
21 factors would tend to increase power for trend
22 detection is contained in both of the
23 documents.
24 Q. In Exhibit 7, the sentence starting "Third, it
DEPOSITION OF WILLIAM W. WALKER, JR.
950
1 reduces the magnitude..." that text proceeding
2 on to the last sentence does not appear in
3 Exhibit 17. Is there a reason why?
4 MR. HARRISON: Object to counsel's
5 characterization. It may appear; you just may
6 not have seen it or recognized it.
7 MS. AHEARN: Well, if that's true, I'd
8 very much appreciate someone pointing out to me
9 what I'm missing.
10 MR. HARRISON: That's why I would
11 appreciate you putting it in the form of a
12 question as opposed to your statement.
13 A. Well, in the case of the draft, there was an
14 indication as stated that the hydrologic
15 adjustment reduced the trend magnitude from 5.8
16 to 4.7 percent per year, and there was further
17 elaboration about that in the draft.
18 In the case of the final, the reduction
19 in the magnitude was considerably less. It was
20 from 5.7 to 5.3 percent per year, as is shown
21 in the first paragraph on page 20 of
22 Exhibit 17.
23 I can't say for certain, but one
24 possible reason why I might have omitted some
DEPOSITION OF WILLIAM W. WALKER, JR.
951
1 of the words there in the final version is
2 because the overall reduction in the trend
3 magnitude was not as large as -- in the final
4 version as it was in the draft.
5 Q. And the change in reduction of trend magnitude
6 is a result of the different selection of
7 hydrologic variables; is that true?
8 A. As I testified earlier, there were two things
9 that were different between the draft and the
10 final. One was in the hydrologic variables
11 that were used for adjustment, and the other
12 one was in the definition of the season length.
13 Q. On page 10 of Exhibit 7 you discuss your
14 sensitivity analysis. The factor identified as
15 Factor 2 here, did you continue to analyze that
16 factor in the final analysis?
17 A. I don't think -- no, I did not include that in
18 the final analysis. That was really
19 superfluous in the draft since the Seasonal
20 Kendall test accounts for seasonality. I
21 didn't think that including a sensitivity
22 analysis on the effect of season was a
23 particularly important result, so I didn't
24 repeat that in the final.
DEPOSITION OF WILLIAM W. WALKER, JR.
952
1 Q. After this draft, did you include additional
2 factors in your sensitivity analysis?
3 MR. HARRISON: Do you mean in the
4 September draft that he did not do in the July
5 draft?
6 MS. AHEARN: Yes.
7 A. Well, if we compare Table 3 in the July draft,
8 Exhibit 7, with Table 3 in the September final,
9 that's Exhibit 17, we can see what additional
10 sensitivity analyses were performed in the
11 final that were not performed in the draft.
12 Q. Why did you pursue additional sensitivity
13 analyses after the draft?
14 A. To further explore the sensitivity of the
15 results to individual factors. In particular,
16 the addition of rainfall as an explanatory
17 variable I felt warranted additional
18 sensitivity analysis using different averaging
19 periods, different groups of stations and
20 different combinations of the three hydrologic
21 variables -- elevation, rainfall and flow. And
22 all of these are outlined in Table 3 on page 27
23 of Exhibit 17.
24 Q. Let's go ahead and turn to Table 3, then.
DEPOSITION OF WILLIAM W. WALKER, JR.
953
1 Before we have you change the page in
2 Exhibit 7, on page 10, Exhibit 7, the bottom
3 paragraph --
4 MR. HARRISON: Page 10, Exhibit 7?
5 MS. AHEARN: Yes.
6 MR. HARRISON: Bottom paragraph?
7 Q. To my reading, Dr. Walker, this paragraph does
8 not appear in the final report. Is there a
9 reason why this discussion was omitted?
10 MR. HARRISON: Object to form.
11 A. If you could point me to the place where that
12 paragraph is missing in the final, I'd be glad
13 to explain it to you.
14 Q. Sure. On page 26.
15 MR. HARRISON: Just so I'm clear,
16 Counsel, are you talking about the paragraph
17 that begins in Exhibit 7 "Lowest significance
18 levels..."?
19 MS. AHEARN: Yes.
20 MR. HARRISON: It's your representation
21 that that entire paragraph is missing on 17?
22 MS. AHEARN: If anyone wants to
23 double-check my --
24 A. I don't see that the concepts contained in that
DEPOSITION OF WILLIAM W. WALKER, JR.
954
1 paragraph are missing from the final draft.
2 There's reference to a range of trend magnitude
3 in both the first and the final versions.
4 There's reference to the effect of the
5 phosphorus spike in 1985. Other than that, I
6 don't know any particular reason why I
7 restructured the paragraphs in the final as
8 compared with the earlier draft.
9 Q. Did you use the same flow data in the nutrient
10 transport analyses that you used in the trend
11 analyses of concentrations?
12 A. I believe that I already testified to in the
13 final version I did not use flow data analyzing
14 the concentration data for trends except in the
15 case of the sensitivity analysis.
16 Q. Okay. Thank you for correcting me.
17 Did you use that same flow data in the
18 sensitivity analysis? Did you use those same
19 flow data for the nutrient transport?
20 A. I believe so.
21 Q. Okay. Thank you. I got lost.
22 I'd like to direct your attention to
23 Table 3 as it appears on page 27 of Exhibit 17.
24 In the entries of the modified regressions for
DEPOSITION OF WILLIAM W. WALKER, JR.
955
1 flow where in NMAX we have the value 7 entered,
2 am I correct, that reflects that there are
3 seven different definitions of flow that you
4 have employed in the sensitivity analysis?
5 A. As is stated in the footnote to Table 3, NMAX
6 equals the maximum number of terms included in
7 hydrologic regression in each class (elevation,
8 rainfall or flow) each term significant at P
9 less than .1.
10 Q. Well, am I correct that those terms for
11 elevation and rainfall would be the result of
12 the step-up regression against antecedent
13 periods?
14 A. NMAX would reflect the maximum number of terms
15 included in the hydrologic regression in each
16 class just as is stated in the footnote. For
17 -- each term within each class would represent
18 a different time interval.
19 Q. We have discussed time intervals that you have
20 employed for elevation and rainfall, correct?
21 I don't want to cover that ground again.
22 Where have you developed various terms
23 included in hydrologic regression for flow?
24 A. The terms included for flow are analogous to
DEPOSITION OF WILLIAM W. WALKER, JR.
956
1 those included for elevation and rainfall.
2 Q. Are these terms of flow that reflect different
3 antecedent periods?
4 A. The procedure was exactly analogous to the
5 procedure that was used for elevation and
6 rainfall. It's just that I added a third term
7 in the regression equation that would reflect
8 flow lagged at different time scales.
9 Q. And am I correct, you had not performed that
10 type of regression in the July 3rd draft?
11 A. That's correct.
12 Q. Okay. In the materials we have looked at, is
13 this the first time we have seen this
14 expression of various terms of flow through
15 this hydrologic regression method?
16 A. That's correct. The report describes the
17 inclusion of flow along with elevation and
18 rainfall only in the section on sensitivity
19 analysis.
20 (Off the record)
21 Q. Dr. Walker, the third entry for modified
22 regressions for flow, you have NMAX, 1. Does
23 that reflect the flow term which provided the
24 optimal antecedent value?
DEPOSITION OF WILLIAM W. WALKER, JR.
957
1 A. That would reflect the single flow term -- the
2 single time scale for averaging the flow that
3 would provide the highest correlation between
4 flow and concentration.
5 Q. If you'll turn to Table 6 on 41, keep both
6 hands on -- we'll flip back and forth here, but
7 we have Table 3 on page 27. I'd also like you
8 to refer to Table 6 on 41.
9 MR. HARRISON: Of Exhibit 17?
10 MS. AHEARN: Of Exhibit 17.
11 Q. Okay. Here for the first entry Total P, Shark
12 River Slough, Flow, we see the same number of
13 observations both on Table 3 and Table 6,
14 correct, 256?
15 A. Correct.
16 Q. And the same term, is the same term of flow
17 employed in both Table 3 and Table 6?
18 A. I don't know what term -- what time scale was
19 selected in Table 3 for the regression. I
20 would have to look at the computer files in
21 order to learn that.
22 Q. If the same time scale was selected both for
23 Table 3 and Table 6, should the resulting
24 values for your Standard Error, RA, Trend,
DEPOSITION OF WILLIAM W. WALKER, JR.
958
1 PROB1 and PROB2 be the same in both tables?
2 A. Well, in a sense we're comparing apples andegressions for flow, you have NMAX, 1. Does
23 that reflect the flow term which provided the
24 optimal antecedent value?
DEPOSITION OF WILLIAM W. WALKER, JR.
957
1 A. That would reflect the single flow term -- the
2 single time scale for averaging the flow that
3 would provide the highest correlation between
4 flow and concentration.
5 Q. If you'll turn to Table 6 on 41, keep both
6 hands on -- we'll flip back and forth here, but
7 we have Table 3 on page 27. I'd also like you
8 to refer to Table 6 on 41.
9 MR. HARRISON: Of Exhibit 17?
10 MS. AHEARN: Of Exhibit 17.
11 Q. Okay. Here for the first entry Total P, Shark
12 River Slough, Flow, we see the same number of
13 observations both on Table 3 and Table 6,
14 correct, 256?
15 A. Correct.
16 Q. And the same term, is the same term of flow
17 employed in both Table 3 and Table 6?
18 A. I don't know what term -- what time scale was
19 selected in Table 3 for the regression. I
20 would have to look at the computer files in
21 order to learn that.
22 Q. If the same time scale was selected both for
23 Table 3 and Table 6, should the resulting
24 values for your Standard Error, RA, Trend,
DEPOSITION OF WILLIAM W. WALKER, JR.
958
1 PROB1 and PROB2 be the same in both tables?
2 A. Well, in a sense we're comparing apples and
3 oranges here because in one case we're talking
4 about a trend test for concentration, which is
5 Table 3, and in Table 6 we're talking about the
6 test on loads. So they would not necessarily
7 give the same result.
8 Q. In the nutrient transport analysis you
9 performed the Seasonal Kendall test both with
10 and without hydrologic adjustment, correct?
11 A. That's correct.
12 Q. And with hydrologic adjustment, that is again
13 the regression using the hydrologic variables?
14 A. Yes. That was the -- that's the definition of
15 the hydrologic adjustment.
16 Q. And is that regression performed against the
17 product of concentration and flow for each
18 sampling date?
19 A. No.
20 Q. Okay. In your nutrient transport analysis you
21 start with an instantaneous nutrient transport
22 rate, correct?
23 A. Yes.
24 Q. And that's calculated as each sampling date and
DEPOSITION OF WILLIAM W. WALKER, JR.
959
1 basin as the product of sample concentration
2 and corresponding daily mean flow, correct?
3 A. Well, that's described on page 35. I believe
4 there was also a units conversion factor that
5 was applied there to convert the units to
6 kilograms per day.
7 Q. Okay. Well, when we're back at the step of
8 just multiplying concentration by daily mean
9 flow, did you take for each structure the
10 concentration and corresponding daily mean flow
11 and then sum the results of that to obtain the
12 loading for the basin? In other words, did you
13 calculate loading through each structure and
14 then aggregate those to get the basin load?
15 A. Well, the basin load was calculated as a
16 product of the flow-weighted concentration for
17 all four gates times the total flow.
18 Q. For all four gates?
19 A. Right, for all four gates. By definition, that
20 would give the same result as the alternative
21 procedure which you described.
22 MS. AHEARN: Mr. Harrison, do you want
23 to take a break?
24 (Off the record)
DEPOSITION OF WILLIAM W. WALKER, JR.
960
1 (Short recess)
2
3 BY MS. AHEARN:
4 Q. Dr. Walker, when you do the step-up regression
5 for the antecedent periods, when you look at
6 the Period 1, is that the date of the sample or
7 the date following the sample, the
8 concentration sample -- excuse me, the date
9 preceding the sample? I misspoke.
10 A. As is stated on page 10 of Exhibit 17
11 underneath Equation 1 where it defines the term
12 for precipitation, it says Pi equals total
13 precipitation for i antecedent days where i
14 equals 1 on the date of the sample.
15 Q. Okay. Thank you for reminding me of that.
16 Now, is this period of one among the
17 antecedent periods that you used for the
18 purposes of defining flow, the terms of flow in
19 Table 3?
20 A. I testified earlier that I was treating flow
21 the same as the other hydrologic factors --
22 namely, elevation and rainfall. And as stated
23 on page 10 in the bottom paragraph, "Antecedent
24 periods of 1, 7, 30, 90, 180, 270 and 365 days
DEPOSITION OF WILLIAM W. WALKER, JR.
961
1 are tested for each hydrologic factor."
2 Q. In the case of your nutrient transport analysis
3 where you're regressing the instantaneous
4 nutrient transport rate against flow, wouldn't
5 you expect to find the highest correlation when
6 the antecedent period is one?
7 A. I wouldn't expect anything.
8 Q. Well, if the antecedent period is one, aren't
9 you using the same value in the regression as
10 you used in the computation of the
11 instantaneous nutrient transport rate?
12 A. That's correct.
13 Q. So you're regressing a value against another
14 value which is a product of --
15 A. On a log scale, that's correct.
16 Q. On a log scale.
17 If you used that same value in the
18 analysis of the nutrient transport data in
19 Table 6, shouldn't the entries for the
20 hydrologic variable flow for SE, RA, Trend,
21 PROB1 and PROB2 be the same as the entries for
22 the hydrologic variable flow using 1 NMAX --
23 using one term in Table 3?
24 A. As I stated earlier, Table 3 involves a
DEPOSITION OF WILLIAM W. WALKER, JR.
962
1 regression analysis of concentration data.
2 Table 6 involves a regression analysis of load
3 or transport rate data. The differences in
4 those statistics which you rattled off could
5 reflect the fact that a different lag time was
6 selected by the stepwise procedure to represent
7 the effects of flow.
8 Q. Do you know whether a lag time other than one
9 was selected for use in Table 6?
10 A. You mean do I know right -- no, I do not know.
11 Q. Would there be a document that would reflect
12 what the result of the stepwise regression was
13 in this regard?
14 A. I believe those results would be contained in
15 one or more of the computer files that I
16 transferred to the Justice Department.
17 Q. In the regression you performed on
18 concentration data and the regression you
19 performed on nutrient transport rates, both
20 employed the lag time period of one. Wouldn't
21 those regressions produce identical residuals?
22 A. I do not know whether or not each of those
23 regressions employed a lag time of one.
24 Q. But if they did, I'm asking you to assume that
DEPOSITION OF WILLIAM W. WALKER, JR.
963
1 they did, wouldn't they produce identical
2 residuals?
3 A. If the regression involved only one term inflow
4 and if the flow lag time were the same in both
5 the concentration and load analysis, then the
6 residuals should be the same.
7 Q. Could you turn to page 28 in Exhibit 17. You
8 described direct regression as an alternative
9 method for estimating trend magnitude. Is
10 there any reason why you didn't employ this
11 method first?
12 A. No.
13 Q. The equation that you express here, Equation
14 No. 5, would that also be expanded to include a
15 term representing season?
16 A. It could.
17 Q. Did you consider doing that?
18 A. I believe I did that in the first draft.
19 Q. Is there a reason why you took it out of the
20 final?
21 A. I don't recall. It could have been that it
22 wasn't -- that the term wasn't significant from
23 a statistical point of view. I don't recall
24 why I took it out.
DEPOSITION OF WILLIAM W. WALKER, JR.
964
1 Q. At this time what do you feel would be the
2 strongest scientific rationale for taking that
3 term out?
4 MR. HARRISON: Object to form.
5 A. Well, if it did not contribute significantly to
6 explaining the variance in the data and if it
7 didn't have any effect on the slope or the
8 significance level of the trend term.
9 Q. So it would be after review of the results of
10 including the term in the original draft?
11 A. I don't understand your question.
12 Q. Would you determine -- if the term for season
13 did not contribute in those regards that you
14 have just identified, would that be based on
15 your review of the results of including the
16 term in the original draft?
17 A. I would test -- are we talking about the
18 original draft or the final draft?
19 Q. How did you determine that the term for season
20 did not contribute anything significant to this
21 analysis?
22 MR. HARRISON: Objection, Counsel. It
23 mischaracterizes his testimony. He said he
24 didn't recall. I suggest if you want to
DEPOSITION OF WILLIAM W. WALKER, JR.
965
1 explore it, it would be better to go to
2 Exhibit 7 and look at where he added it and why
3 he took it out. But you did mischaracterize
4 his testimony.
5 A. I testified that I did not recall why I
6 excluded the seasonal terms from Equation 5 on
7 page 28 of Exhibit 17. It may have been
8 because those terms were not significant, they
9 did not contribute to explaining variance in
10 concentration once the other factors in the
11 equation were considered.
12 Q. Could you, please, turn to Table 4, page 31, in
13 Exhibit 17?
14 MR. HARRISON: Page 34?
15 MS. AHEARN: Page 31, Table 4.
16 MR. HARRISON: Oh, sorry. Table 4.
17 Q. The results that you report here, are those
18 results adjusted for serial correlation?
19 A. I report both results without seasonal
20 covariance and results with seasonal
21 covariance, as is plainly identified in
22 Table 4.
23 Q. I'm sorry. Are these corrected for serial
24 correlation as between years?
DEPOSITION OF WILLIAM W. WALKER, JR.
966
1 A. I believe I testified earlier that there is no
2 identifiable serial correlation between years
3 in the data. These are the results of the
4 Seasonal Kendall test as described in the
5 report.
6 Q. You report here tests for nine stations and 20
7 water quality components. Were each of those
8 tests independent?
9 MR. HARRISON: Object to form.
10 A. What do you mean by "independent"?
11 Q. Well, on Table 4 you employ the term expected
12 number in each case is P less than .05. Does
13 the use of this term assume that each of the
14 tests you will run here is independent of each
15 other?
16 A. Well, Series A, Series B and Series C are
17 certainly not independent of each other because
18 they are each conducted using similar data sets
19 or overlapping data sets, and the nine stations
20 include two stations that are composite
21 stations that are calculated from other
22 stations; for example, the S12 composite is
23 calculated from S12A, B and C. And the other
24 degree of dependence, I guess, would be the
DEPOSITION OF WILLIAM W. WALKER, JR.
967
1 N-to-P ratio is not independent of total P and
2 total N.
3 Q. How about among the nitrogen species?
4 A. And it is true that the -- that there would
5 probably only be two degrees of -- two
6 independent variables among total Kjeldahl N,
7 organic N and ammonia N would only be two
8 independent measurements.
9 Q. Did you account for that dependence in
10 determining the P values?
11 A. Well, in the case of Series A there were -- for
12 total phosphorus there were seven independent
13 tests conducted for trend in total phosphorus;
14 and of those seven independent tests, eight
15 indicated a significant increasing trend. I
16 believe that that probability level is below
17 .05, well below .05.
18 Q. Did you account for the dependence among
19 stations and water quality components in
20 predicting that the expected number in each
21 case for P would be less than .05?
22 A. The number of observed trends was so far in
23 excess of that which would be expected based on
24 chance. I expect that if one were to account
DEPOSITION OF WILLIAM W. WALKER, JR.
968
1 for that dependence, that the probability
2 levels would be less than .05, although I have
3 not done that calculation in detail.
4 Q. Is there any way of doing that calculation?
5 A. Yes.
6 Q. How would you go about doing that?
7 A. I would have to tabulate the number of
8 significant results that were derived from
9 combinations of stations and water quality
10 parameters that were not dependent upon each
11 other and compare that number of significant
12 results with the number of significant results
13 that one would expect based upon chance for the
14 same total number of tests and the level of
15 significance that was used for the test.
16 Q. If you'll turn to page 33, the last sentence in
17 the middle paragraph there, you state that
18 trend magnitudes cannot be estimated because of
19 the high percentage of ortho phosphorus
20 measurements at or below the lower detection
21 limit.
22 Do you have any belief as to whether
23 those ortho phosphorus measurements are
24 accurate?
DEPOSITION OF WILLIAM W. WALKER, JR.
969
1 A. What do you mean by "accurate"?
2 Q. Do they accurately reflect the conditions --
3 the population which was intended to be
4 sampled?
5 MR. HARRISON: Objection. Foundation.
6 You may answer.
7 A. Well, I believe that the accuracy of the ortho
8 phosphorus measurements is less than the
9 accuracy of total phosphorus measurements.
10 Q. Can you quantify relatively how more
11 inaccurate --
12 A. I can't put a quantitative estimate on it.
13 Q. Do you have an estimate as to how many of the
14 ortho phosphorus levels reported at or below
15 detection level were in fact not at or below
16 detection level, an idea of how many of those
17 are --
18 A. All I have is an estimate or a tabulation of
19 the number of values that were reported below
20 the detection limit. I have no way of
21 discerning whether or not some of those values
22 were actually above the detection limit. I'm
23 just working with the data as provided by the
24 District.
DEPOSITION OF WILLIAM W. WALKER, JR.
970
1 Q. On the next page, 34, the first full paragraph,
2 you have a sentence in which you cite to
3 Belanger et al.
4 Is that the same summary paper that we
5 discussed in your earlier reference to
6 Belanger?
7 MR. HARRISON: Object to form. I think
8 there have been several times we talked about
9 Belanger.
10 A. That is a reference to a document that is cited
11 in the reference list on page 45.
12 Q. Do you rely on any primary data or original
13 research to support the statement for which
14 Belanger is here cited?
15 MR. HARRISON: Object to form.
16 A. I have not done any original research or field
17 work on this topic. I just am using Belanger
18 et al. as a reference that describes the
19 observation and measurement of lower dissolved
20 oxygen regimes in phosphorus-enriched zones of
21 the Water Conservation Areas.
22 Q. Have you reviewed any primary data or original
23 research on that topic?
24 A. I don't recall. I may have read some report on
DEPOSITION OF WILLIAM W. WALKER, JR.
971
1 that topic.
2 Q. Previously I asked you if there were
3 differences in the methodology you employed as
4 opposed to that employed by Mattraw et al., and
5 I believe you informed us that you would want
6 to actually refer to the report.
7 MS. AHEARN: Off the record.
8 (Off the record)
9 Q. Dr. Walker, I'm going to hand you a copy of
10 USGS Water-Resources Investigations Report
11 87-4142. This has previously been marked and
12 referred to in this litigation as Deposition
13 Exhibit 60. It was so marked in the deposition
14 of Michael Finley.
15 I'll ask you if this is the Mattraw
16 report to which we have referred and on which
17 you have relied. I would represent,
18 Dr. Walker, that you also provided another copy
19 of this same report in the materials provided
20 to the Department of Justice.
21 A. Yes, I believe that this is the reference
22 report by Mattraw et al.
23 Q. Could you, please, explain in any regards you
24 deem significant how your application of the
DEPOSITION OF WILLIAM W. WALKER, JR.
972
1 Seasonal Kendall test differs from that
2 employed in Mattraw et al.?
3 MR. HARRISON: Object to the breadth of
4 the question.
5 Q. In the interests of expediency, you had
6 reviewed Mattraw et al. prior to preparing
7 Exhibits 7 and 17, correct?
8 A. Yes.
9 Q. Do any differences come to mind in terms of the
10 methodology employed by Mattraw et al. versus
11 that employed by you?
12 A. Well, there are several differences between
13 this study and my own. Those that I can recall
14 would include, first of all, differences in
15 scope with respect to the stations covered, the
16 parameters covered, the time period examined.
17 Generally I'm focusing on inflow points to the
18 Park. Mattraw et al. considered some inflow
19 points to the Park but not all of them.
20 I'm covering a wider range of water
21 quality variables, the 20 components that are
22 listed in my report. Mattraw et al. only
23 considered a subset of water quality variables,
24 which did not include total phosphorus.
DEPOSITION OF WILLIAM W. WALKER, JR.
973
1 The time periods differ. Mattraw et al.
2 considered, I believe, a period from 1978
3 through 1982 using the District's database, and
4 I have considered the time period 1977 through
5 1989, September of 1989.
6 With respect to methodology, the Mattraw
7 report only uses the less conservative version
8 of the Seasonal Kendall test, to my knowledge.
9 In other words, it does not use the version of
10 the Seasonal Kendall test that accounts for
11 seasonal covariance or serial correlation.
12 Mattraw et al. use a different set of
13 procedures and time scales for adjusting
14 concentrations based upon antecedent rainfall.
15 And the other difference that I recall
16 is that Mattraw et al. used a two-month season
17 -- in other words, they only have six seasons
18 per year in calculating their Seasonal Kendall
19 test -- whereas I've used primarily monthly
20 seasons, 12 seasons per year.
21 Those are the distinctions that I can
22 recall.
23 Q. Great. Thank you.
24 MR. HARRISON: Off the record.
DEPOSITION OF WILLIAM W. WALKER, JR.
974
1 (Off the record)
2 Q. Dr. Walker, in your regressions as part of the
3 nutrient transport analysis, did you find high
4 correlation between nutrient transport rate and
5 flow?
6 MR. HARRISON: Object to form.
7 A. In general, the correlations between nutrient
8 transport and flow were higher than those
9 observed between nutrient transport and the
10 other hydrologic factors.
11 Q. Well, for the S12 totals and flow, you obtained
12 an R2 value of .716.
13 A. Correct.
14 Q. Is that what might be called a spurious
15 correlation?
16 MR. HARRISON: Object to form.
17 A. Flow is an important causal factor determining
18 the transport rate of nutrients. The term
19 "spurious correlation" has been used in the
20 literature as describing the situation where
21 one regresses loading calculated as a product
22 of flow and concentration against flow. And
23 the interpretation of the high R2 value there
24 -- relatively high R2 partially reflects the
DEPOSITION OF WILLIAM W. WALKER, JR.
975
1 fact that flow is essentially on both sides of
2 the equation.
3 The purpose of this analysis, however,
4 is not to determine which hydrologic factor is
5 the most predominant factor determining
6 variations in loading, but it is to produce a
7 time series of residuals or differences between
8 the measurements and the prediction that is
9 uncorrelated with the hydrologic factors.
10 Q. Is there any way of determining the nutrient
11 transport rate independent of employing the
12 factor flow?
13 A. No.
14 Q. Now, you looked at nutrient transport rates for
15 the combined discharge to Shark River slough
16 but not for individual release points.
17 Have you calculated nutrient transport
18 rates for the individual release points?
19 A. I don't recall having done that. I may have.
20 Q. You have general familiarity with the work that
21 Dr. Ron Jones has done for the lawsuit,
22 correct?
23 MR. HARRISON: Object to form.
24 A. I am generally aware of the type of work that
DEPOSITION OF WILLIAM W. WALKER, JR.
976
1 Dr. Ron Jones has done --
2 Q. Are you aware --
3 A. -- for the lawsuit.
4 Q. Are you aware of work he's done along a
5 transect located within Everglades National
6 Park?
7 A. I'm aware that he has worked along a transect
8 in Everglades National Park.
9 Q. What is the location of that transect?
10 A. I believe it's in the vicinity of S12C running
11 on a north-to-south axis.
12 Q. Have you reviewed the declaration of Dr. Jones
13 that was submitted in support of the
14 Government's motion for partial summary
15 judgment?
16 A. No, I have not.
17 Q. Are you aware of any opinions Dr. Jones may
18 have regarding the impact of phosphorus loading
19 to the Everglades National Park?
20 A. Yes.
21 Q. What are the opinions of which you are aware?
22 A. In a qualitative sense I'm aware of his
23 concerns about the effects of loading from
24 these structures causing enrichment of the peat
DEPOSITION OF WILLIAM W. WALKER, JR.
977
1 in the downstream system and resulting in
2 subsequent ecological impacts.
3 Q. Are Dr. Jones' opinions based on the work he's
4 done along this transect near S12C?
5 MR. HARRISON: Objection in that the
6 question may call for speculation.
7 A. Dr. Jones' opinions are based upon the combined
8 result of his experience and whatever work he's
9 done on the system. That would include, I
10 suppose, the work along S12C.
11 Q. I think you used the term "impacts" in
12 describing your understanding of Dr. Jones'
13 opinion.
14 Are you aware of any impacts that
15 Dr. Jones is looking at in relation to
16 phosphorus concentrations as opposed to
17 phosphorus loading?
18 MR. HARRISON: I object to the
19 characterization that Dr. Jones has made such a
20 differentiation. To avoid my objections on
21 that, I wouldn't object if your questions were
22 worded whether or not Dr. Jones has done that
23 as opposed to that. You can ask him, but
24 you'll get the objection if you keep
DEPOSITION OF WILLIAM W. WALKER, JR.
978
1 characterizing it. Just trying to --
2 MS. AHEARN: I think if I preface the
3 question whether -- strike it. Let me rephrase
4 it.
5 Q. Are you aware of any impacts that Dr. Jones has
6 identified that relate to phosphorus loading
7 within the Park as opposed to phosphorus
8 concentration?
9 A. It's very difficult to separate out the effects
10 of loading and concentration.
11 Q. Does your analysis of the nutrient transport
12 rate to combined discharge to Shark River
13 slough give us an accurate picture of nutrient
14 loading downstream of the S12C structures?
15 A. It reflects as it has stated the combined
16 discharge to Shark River slough, which includes
17 S12A, B, C, D, and the difference between S333
18 and S334.
19 Q. As a scientist, would you take that analysis of
20 the combined discharge and apply it to an issue
21 relating to the transect downstream of S12C?
22 MR. HARRISON: Object to form. No
23 stated purpose.
24 A. Apply it how?
DEPOSITION OF WILLIAM W. WALKER, JR.
979
1 Q. In investigating the effects of phosphorus
2 loading to that area downstream of S12C.
3 A. I don't know that these results of the trend
4 analysis are something that one would apply to
5 field experiments or to transects, work that's
6 conducted in the field. I don't -- these are
7 different pieces of research.
8 Q. Could the results of your trend analysis on
9 nutrient loading be incorporated into field
10 research within the Park?
11 MR. HARRISON: Object to form.
12 A. Research for what purpose?
13 Q. Let's just start out for any purpose. You seem
14 to draw a distinction here of these being
15 separate pieces of research.
16 Are the results of the trend analysis of
17 nutrient loading amenable to incorporation into
18 field work?
19 A. Well, the field work would have to have some
20 objective to answer a certain question. And I
21 can't just answer your question without having
22 some frame of reference.
23 Q. Okay. How about field work directed to the
24 question of whether nutrient loading has had
DEPOSITION OF WILLIAM W. WALKER, JR.
980
1 any impact within the Park?
2 A. The analysis of loading that I have done and
3 described in Table 6 describes what happened
4 over a certain period of time for the combined
5 discharge to Shark slough.
6 To design a field program to investigate
7 impacts of phosphorus load on the system would
8 be quite another matter. It would not pertain
9 to this analysis.
10 Q. Do you know of any plans or ongoing attempts to
11 incorporate the results of your nutrient
12 loading analysis into any other scientific work
13 other than your own? I'll add that
14 qualification.
15 A. I'm not aware of any such plans.
16 Q. With regard -- let me just go through these
17 questions quickly. Bear with me.
18 With regard to your analysis of the
19 concentrations of water constituents entering
20 the Park, are the results of those analyses
21 amenable for incorporation into field work
22 addressed to determining whether water flowing
23 into the Park has had impacts within the Park?
24 A. Well, one could design such studies quite
DEPOSITION OF WILLIAM W. WALKER, JR.
981
1 independently of the trend analysis.
2 Q. But incorporating the trend analysis or the
3 results of the trend analysis, is that an
4 appropriate use of the results of your work?
5 A. The trend analysis might point out particular
6 stations from the point of view of providing
7 guidance for locating transects, for example,
8 if one wanted to do that sort of work.
9 Q. Are you aware of any current plan or ongoing
10 effort to incorporate the results of your
11 analysis of water quality concentration
12 parameters in the work of any other scientist?
13 A. I'm not aware of any such plans.
14 Q. Or ongoing attempts?
15 A. Or ongoing attempts.
16 Q. Dr. Walker, could you turn to page 40 of
17 Exhibit 17? Midway through the paragraph that
18 starts "The first test..." you talk about test
19 results for the combined discharge are strongly
20 influenced by the 1989 drought. What do you
21 mean by the term "the 1989 drought"?
22 MR. HARRISON: I will for the record
23 note that that's the middle of a sentence and
24 it may or may not be taken out of context.
DEPOSITION OF WILLIAM W. WALKER, JR.
982
1 A. Well, the statement is certainly taken out of
2 context, but that context is there in the
3 report.
4 Q. The purpose of reading was just to point you to
5 the particular phrase I'd like to have you
6 define.
7 A. Fine.
8 Q. Just that phrase is what I'd like to have
9 defined.
10 A. Okay. As is indicated in the sentence after
11 that, as shown in Figure 2, which now we will
12 turn to Figure 2 which is on page 4, and what I
13 refer to as the 1989 drought, if you look at
14 the figure that is smack dab in the middle of
15 the page which is the total flow for S12 plus
16 S333 plus S334, these are monthly flows over
17 time, what I refer to as the 1989 drought is
18 the period which is on the far right-hand side
19 there, which is essentially the period in --
20 throughout most of 1989 through which there was
21 zero flow into the Park in Shark slough as
22 distinct from the entire period of record prior
23 to that in which case -- in which there was
24 flow or, if there was zero flow, it only
DEPOSITION OF WILLIAM W. WALKER, JR.
983
1 occurred for a period of a month or two. So
2 the --
3 Q. So --
4 A. Go ahead.
5 Q. I'm sorry. So you define "drought" in terms of
6 releases to the Shark River slough?
7 A. As I was discussing it in that particular
8 paragraph on page 40, I was referring to
9 drought as it reflected -- as it reflected
10 periods -- an extended period of no flow into
11 Shark River slough during which the transport
12 of phosphorus would be zero regardless of what
13 the water quality conditions would be.
14 Q. So the term as used in this middle paragraph on
15 page 40 "1989 drought" is basically synonymous
16 with no-flow conditions?
17 MR. HARRISON: Asked and answered.
18 Q. Well, Dr. Walker, the term "drought" I think
19 usually connotes reference to much broader
20 climatological factors, what happened over the
21 entire South Florida region. And I understand
22 the definition you're using here as really
23 being quite different from that, so I want to
24 make sure that I understand your definition.
DEPOSITION OF WILLIAM W. WALKER, JR.
984
1 A. The occurrence of an extended period of low
2 flow through the S12s and S333 in 1989 is
3 linked to that broader definition that you are
4 referring to. But in the case of this
5 paragraph on page 40, I am merely using the
6 term "1989 drought" to refer to that particular
7 time period during which there was an extended
8 period of no flow into the Shark slough.
9 Q. Is it that the drought conditions influenced
10 the presence of flow and not necessarily the
11 phenomenon being tested in particular nutrient
12 transport rates?
13 A. The fact that there was no flow for that period
14 also meant that there would be no nutrient
15 transport regardless of what the water quality
16 conditions were upstream.
17 Q. Do you know if there has been a 1990 drought?
18 A. I have not seen the detailed flow record for
19 1990.
20 Q. In the context of your analysis of marsh
21 stations, will you be employing a definition of
22 "drought"?
23 A. I don't know that I will have to define such a
24 term in order to conduct the analysis of the
DEPOSITION OF WILLIAM W. WALKER, JR.
985
1 marsh stations.
2 Q. Have you done any analyses that would show you
3 whether the results for the marsh are
4 influenced by the 1989 drought?
5 A. I haven't -- I have just begun my analysis of
6 the marsh data, and I haven't formed any
7 conclusions on that topic.
8 Q. How about for the preliminary analysis of
9 inflows and outflows to the WCAs?
10 A. My answer is the same. I have only done a
11 preliminary analysis of that.
12 (Off the record)
13 (Short recess)
14
15 (Exhibit No. 56 marked for
16 identification)
17 BY MS. AHEARN:
18 Q. Dr. Walker, can you identify the exhibit marked
19 as No. 56?
20 A. Fifty-six?
21 Q. Yes. We have just handed you a new exhibit.
22 A. Fifty-six is a series of four pages of graphs
23 entitled Simulation of Trend Detection
24 Procedures Test on Means - Clean Data and so
DEPOSITION OF WILLIAM W. WALKER, JR.
986
1 forth.
2 Q. And these graphs were produced by you?
3 A. That's correct.
4 Q. Did you generate these in the context of the
5 ONRW deliberations?
6 A. Yes.
7 Q. Do they have any bearing on your trend analyses
8 as reflected in Exhibit 17?
9 A. No.
10 Q. On page 1 you apparently look at clean data; on
11 page 2, messy data. What is the distinction?
12 A. Well, the terms "clean" and "messy" I believe
13 were derived from an article that was authored
14 by Hippel, I believe, in the materials that I
15 provided to the Justice Department.
16 Clean is generally data that is --
17 refers to data that is not serially correlated;
18 it's random with respect to time and it has a
19 certain distribution. And messy data -- I
20 don't recall exactly what the parameters of
21 this data set were, but messy data would
22 generally include information that was serially
23 correlated, that has some nonrandom behavior to
24 it.
DEPOSITION OF WILLIAM W. WALKER, JR.
987
1 Q. For purposes of trend detection procedures in
2 connection with inflows to the Park, which is
3 the preferable scenario to adopt when you're
4 simulating trend detection procedures?
5 A. Well, these simulations were generally intended
6 to provide a rough scale about the power of
7 various methodologies for setting standards and
8 detecting trends using computer-generated time
9 series. They were not really intended to
10 reflect actual -- actual data from a particular
11 structure.
12 Q. So Exhibit 56 are examples of just a technique
13 as opposed to a particular application?
14 A. Well, the primary purpose for Exhibit 56 was to
15 examine the sensitivity of the methodology for
16 setting standards to the Park to the averaging
17 period -- that is, the values one year, three
18 years and five years.
19 There was some question as to whether,
20 for example, using a five-year period for the
21 purposes of calculating a standard and
22 determining compliance with the standard would
23 provide sufficient sensitivity to protect the
24 Park against short-term variations in
DEPOSITION OF WILLIAM W. WALKER, JR.
988
1 concentration at the inflow points. So the
2 primary purpose of these simulations was to
3 examine the sensitivity of the standards to the
4 assumed averaging period.
5 Q. What do these simulations tell you about the
6 relative sensitivities of the varying averaging
7 periods?
8 A. The simulations involved testing two general
9 types of water quality trends or changes using
10 computer-generated data. The first time was a
11 constant trend in terms of percent per year,
12 and results of that are shown on the top half
13 of each of these figures.
14 The results generally indicate that for
15 the purpose of detecting a steady trend -- a
16 fixed trend in terms of percent per year, that
17 there was very little difference between a
18 one-year and a three-year and a five-year
19 averaging period with respect to the power or
20 the probability of detecting a trend after a
21 given number of years.
22 The other type of water quality change
23 that was investigated involved a step increase
24 or a sudden increase in concentration of a
DEPOSITION OF WILLIAM W. WALKER, JR.
989
1 certain magnitude at a particular date. This
2 is as distinct from a steady increase of a
3 certain percent per year.
4 And for that step increase, it found
5 that a one-year averaging period might have a
6 little bit more power or higher probability of
7 detecting a step increase after one year or so;
8 but after two or more years, the power or the
9 probability of detecting the increase would be
10 greater for the three-year or the five-year
11 averaging periods.
12 Q. What parameter change distinguishes pages 1
13 and 2 of Exhibit 56 from pages 3 and 4?
14 A. There is no change in parameter. These are all
15 artificial data generated by the computer.
16 Q. I see. And the change in the measure that's
17 under investigation is different, the first two
18 pages addressing means and the second two pages
19 frequencies?
20 A. That's correct.
21 Q. Approximately when did you generate Exhibit 56?
22 A. I believe it was in early summer of or late
23 spring of 1990.
24 Q. Was that provided to the District at or about
DEPOSITION OF WILLIAM W. WALKER, JR.
990
1 that time, to your knowledge?
2 A. Yes, it was.
3 Q. I'd like to have you turn to Exhibit 40,
4 please. On the first page, the two barred
5 graphs that appear in the lower left-hand
6 corner, do these employ the same data and
7 method except for the exclusion of outliers in
8 the bottom bar graph?
9 A. I don't recall for sure, but the notation on
10 the figure which is my handwriting indicates
11 that one says all and the other one says minus
12 outliers. To my -- to the best of my
13 recollection, the only differences between
14 those two graphs are the removal of outliers.
15 Q. Do you recall what methodology you used to
16 remove the outliers here?
17 A. It was the same methodology that was described
18 in one of the prior exhibits.
19 Q. Thirty?
20 A. Yes, Exhibit 30.
21 Q. Just so the record is clear for those who for
22 whatever reason decide to read it after we're
23 done here, the term "flux" that appears in
24 Exhibit 40, is that synonymous with loading and
DEPOSITION OF WILLIAM W. WALKER, JR.
991
1 nutrient transport as we have employed those
2 terms in addressing prior exhibits?
3 A. That's correct. The units would be somewhat
4 different, but the concept is the same.
5 Q. How do the units differ for flux?
6 A. Well, I believe in Exhibit 17, for example, I
7 calculated nutrient transport in units of
8 kilograms per day, and in Exhibit 40 units of
9 flux are in terms of kilograms per year.
10 Q. The balance of Exhibit 40 appears to constitute
11 something labeled double mass curves. What are
12 double mass curves?
13 A. Double mass curves constitute a technique which
14 is commonly used in hydrology for investigating
15 the effects between one variable and another
16 expressed as a cumulative total or running
17 total.
18 Q. Are my eyes accurate here, in preparing these
19 double mass curves you just plot the cumulative
20 amount of each of your variables and then draw
21 an end point directly from zero -- you draw a
22 line directly from zero to the end point of
23 that cumulative plotting?
24 A. Yes. That line is just to provide a frame of
DEPOSITION OF WILLIAM W. WALKER, JR.
992
1 reference for visually detecting changes in the
2 slope of the line -- of the other data points
3 that are plotted there.
4 Q. Is the main purpose of this technique simply to
5 allow you to see when a change occurs -- a
6 greater change occurs in one variable in
7 relation to the other at a particular time in
8 the step?
9 A. That's correct. The idea is to see if there
10 were periods during the record when the change
11 occurred in the slope of one variable with
12 respect to another.
13 Q. What in particular were you looking for in
14 preparing the double mass curves in Exhibit 40?
15 A. I was not looking for anything in particular,
16 but I was just applying this technique as an
17 alternative way for examining the time series
18 of nutrients and other water quality
19 constituents and flow collected at each of the
20 Park inflow structures and in examining them
21 for changes in the flow-weighted concentration
22 over time.
23 Q. Do these double mass curves reflect the total
24 periods of record for the data for each set of
DEPOSITION OF WILLIAM W. WALKER, JR.
993
1 structures that you address in Exhibit 17? For
2 example, does the double mass curve for the
3 S12_334 station reflect the period of record
4 1977 through '89?
5 A. I believe so, but I'm not certain of that.
6 Q. Exhibit 41, Dr. Walker, did you place the
7 "confidential" stamp on this exhibit on the
8 original document?
9 A. That does not look familiar. I don't believe
10 so.
11 Q. Do you recall when you generated this document?
12 A. Well, this exhibit contains a number of items
13 which were not necessarily generated during the
14 same time periods or for the same purpose.
15 Q. Okay. Let me back up a little bit.
16 I'll represent to you, Dr. Walker, that
17 this Exhibit 41 which you'll see has the number
18 ENP 0007909 is a set of documents which the
19 federal government had claimed as privileged,
20 and it's my recollection that they had
21 identified a consulting expert as the author of
22 these documents.
23 Now, am I correct that you are the
24 author of all of the pages that are included in
DEPOSITION OF WILLIAM W. WALKER, JR.
994
1 Exhibit 41?
2 MR. HARRISON: Just to respond to the
3 characterization, I'm not saying that you're
4 accurate or not, Counsel, but there are
5 different Bates numbers as you proceed on
6 through it which are not in seriatim.
7 MS. AHEARN: Okay.
8 MR. HARRISON: So --
9 MS. AHEARN: Those two are entries from
10 the Government's privilege list.
11 MR. HARRISON: All three of the Bates
12 numbers that we have seen on here?
13 MS. AHEARN: Yes.
14 A. I authored each of these pages in Exhibit 41.
15 Q. If you could address them page by page and tell
16 us the approximate time at which and the
17 purpose for which you generated each page? The
18 Government apparently felt it was pretty
19 important what you were doing here so --
20 MR. HARRISON: Objection to
21 characterization. Counsel is well aware that
22 at a certain point in this lawsuit consultants
23 prior to their identification were held back as
24 privileged even if it was pure science. I
DEPOSITION OF WILLIAM W. WALKER, JR.
995
1 don't know when or why these were turned over,
2 but I don't know what you mean by the
3 Government felt it was pretty important. And
4 any insinuations as to when it was done or why
5 it was done I don't think are very relevant.
6 I'm going to let you proceed but --
7 MS. AHEARN: Thank you.
8 Q. If it's more expeditious for you to approach
9 them in groups, that's fine. But I would just
10 like to give you an opportunity to give me a
11 fair characterization of each page of
12 Exhibit 41 so that it accurately describes your
13 description of the work that you performed as
14 reflected here.
15 A. I believe that the first four tables in
16 Exhibit 41 would have been prepared either late
17 in 1989 or early in 1990. The next three
18 figures would have been prepared in late spring
19 of 1990 possibly. The next figure and the last
20 figure --
21 Q. You're referring to Total P Frequency Analysis?
22 A. Total P Frequency Analysis and Total P
23 Frequency Distribution would have been prepared
24 in early 1990.
DEPOSITION OF WILLIAM W. WALKER, JR.
996
1 Q. Are these last two figures figures you produced
2 in the course of the ONRW work? No, that's not
3 right. Strike that. Maybe they are.
4 What was your purpose for preparing the
5 total P frequency analysis?
6 A. It was to summarize the frequency of
7 concentrations above 10, 20 and 30 parts per
8 billion for various marsh stations within the
9 Park and inflow stations for various time
10 periods.
11 Q. Has your analysis of these frequency measures
12 proceeded since the time that you created this
13 chart? In other words, does this reflect an
14 up-to-date picture of your work in terms of the
15 marsh analysis?
16 MR. BURGESS: I'm sorry. Referring to
17 what page or what --
18 MS. AHEARN: The total P frequency
19 analysis.
20 MR. BURGESS: Okay.
21 A. I believe that there might have been some
22 subsequent calculations of frequencies for
23 marsh stations that are not reflected in this
24 figure that were performed after this time
DEPOSITION OF WILLIAM W. WALKER, JR.
997
1 period. Any such calculations would be
2 included in one or more of the data files that
3 I transmitted to the Justice Department.
4 Q. On the last page of Exhibit 41 on this graph
5 you have an entry for "standard." What does
6 that mean?
7 A. The intent of this graph was to illustrate the
8 relationship between the mean total phosphorus
9 on the X axis and the frequency of values above
10 10, 20, and 30 parts per billion as represented
11 by a lognormal distribution frequency. And the
12 intent of the graph was to illustrate under the
13 assumption that this lognormal frequency
14 distribution was -- that this property was
15 maintained; that if one shifted the mean from
16 the vicinity of 15 or 16 as shown on that graph
17 down to the vicinity of 10, which is identified
18 as a hypothetical standard, that one would also
19 expect a reduction in the frequencies of values
20 exceeding 10, 20 and 30 parts per billion.
21 Q. I see. So based on the assumption that you
22 have a lognormal distribution in the data, if
23 the mean were to reduce from approximately 15
24 parts per billion to 9, you would then expect
DEPOSITION OF WILLIAM W. WALKER, JR.
998
1 to see the frequency of values in excess of
2 30 parts per billion to be basically zero?
3 A. That's correct, under the assumption of the
4 lognormal distribution.
5 Q. Is the use of a five-year average important for
6 purposes of understanding this graph?
7 A. For purposes of interpreting the mean and the
8 concept of the standard, yes.
9 Q. Did you use five-year averages as your
10 benchmark in preparing this graph?
11 A. As is indicated on the figure, I used the data
12 between 1985 and 1989. I don't recall the
13 months, but that was the general range of years
14 that were used.
15 Q. In establishing the lognormal distribution,
16 does that reflect a five-year average of the
17 mean?
18 A. The moment of the lognormal distribution
19 identified with the symbols M and S were
20 derived from the same period of record; that
21 is, the '85 to '89 samples.
22 Q. So in this case it's a four-year average?
23 A. Correct.
24 Q. Then there's a note here, "When is P not
DEPOSITION OF WILLIAM W. WALKER, JR.
999
1 flow-weighted?" Does that notation have any
2 meaning to you?
3 A. No.
4 Q. The first page of Exhibit 41, does this reflect
5 part of your preliminary marsh analysis,
6 analysis of the Park marsh stations? And my
7 question relates to the first four pages of
8 Exhibit 41.
9 A. This is part of an initial analysis of the
10 marsh data, just a statistical summary.
11 Q. A statistical summary of the District database
12 for monitoring at these nine marsh stations?
13 A. Yes.
14 Q. And to whom did you distribute the analysis in
15 the first four pages of Exhibit 41?
16 A. I believe I gave a copy of this to Dan Scheidt.
17 Q. Anyone else?
18 A. I don't recall whether I also mailed a copy to
19 the Justice Department or not. I may have.
20 Q. When did you first perform adequate analysis of
21 the Park inflow data such that you determined
22 that there were likely trends in total
23 phosphorus concentrations?
24 MR. HARRISON: Object to form.
DEPOSITION OF WILLIAM W. WALKER, JR.
1000
1 A. Well, in reviewing the various exhibits that we
2 have gone over, I have looked at the data in a
3 number of different ways. But in terms of --
4 and in the course of that analysis, I have
5 developed an opinion.
6 I suppose if one wanted to identify a
7 particular time when I formulated an opinion,
8 an official opinion, that there were in fact
9 increasing trends, it would be upon completion
10 of the analysis that supported my draft
11 submission of Exhibit --
12 Q. Seven?
13 A. -- No. 7 in July of 1990 to the Justice
14 Department.
15 Q. When did you complete that analysis?
16 A. That analysis was completed during June --
17 Q. Did you --
18 A. -- of 1990.
19 Q. Did you report to the Justice Department that
20 your analysis had proceeded that far at that
21 time?
22 A. The Justice Department was aware based upon the
23 commitment that I had made to them that I was
24 working on a report and I was conducting an
DEPOSITION OF WILLIAM W. WALKER, JR.
1001
1 analysis regarding the trends at ENP inflow
2 points and that draft report was going to be
3 submitted in midsummer of 1990.
4 Q. When did the Department of Justice first become
5 aware that your analysis had proceeded so far
6 that you could, to use the term, have an
7 official opinion?
8 A. I had developed some preliminary opinions
9 regarding the presence of trends prior to the
10 completion of that report.
11 Q. When did you inform the Department of Justice
12 of your official opinion?
13 MR. HARRISON: Object to form.
14 A. I don't know if there was a particular date, a
15 particular time at which I officially stated
16 that this is my official opinion. I believe
17 that my opinion was expressed in the form of
18 that report that I submitted.
19 Q. The July 3 report?
20 A. Yes.
21 Q. Dr. Walker, could you, please, refer to
22 Exhibit 42? Did you generate this exhibit on
23 or about the date that appears at the top,
24 December 29, 1989?
DEPOSITION OF WILLIAM W. WALKER, JR.
1002
1 A. It would have been on or before that date, I
2 believe.
3 Q. And to whom did you provide this document?
4 A. I believe I provided it to Dan Scheidt,
5 although I'm not sure whether I gave him a copy
6 of this or not. I may not have given anyone a
7 copy of this.
8 Q. I'll represent to you that this is a copy that
9 was provided to us through Everglades National
10 Park. In the documents that you have provided
11 for your deposition, we find some that look
12 very similar but are not exactly identical. It
13 appears to be maybe formatting changes or maybe
14 the date is different. I don't want to have to
15 put you through an exercise to having to
16 compare these charts side by side.
17 Did you, to your recollection, create
18 other analyses around this same time,
19 December 29, that would include different
20 statistics, different values reflecting more
21 than just changes in computer format, sort
22 sequence and the like?
23 A. Well, there are a number of reports that were
24 generated that have this general format. These
DEPOSITION OF WILLIAM W. WALKER, JR.
1003
1 were very preliminary analyses of the data set.
2 I don't recall exactly the complete scope of
3 all the formats that were involved. These look
4 familiar.
5 Q. When you prepared Exhibit 42, did you do it --
6 did you prepare this document for purposes of
7 preparing for the litigation pending in the
8 federal district court in Miami?
9 A. The immediate reason for preparing Exhibit 42,
10 as I recall, was to provide some statistical
11 summaries, some frame of reference that could
12 be used in the ONRW discussions that were
13 scheduled and which did begin with the District
14 in the beginning of 1990.
15 Q. When you produced Exhibit 42, did you have any
16 understanding as to whether this information
17 would be used for purposes of preparing for
18 trial in the South Florida litigation?
19 MR. HARRISON: Objection. Asked and
20 answered from the context that all of his work
21 obviously could have been. If you're asking
22 specifically what he had in his mind when he
23 did that document, you may ask it that way.
24 MS. AHEARN: Well, I believe that that's
DEPOSITION OF WILLIAM W. WALKER, JR.
1004
1 the gist of the question that I have pending.
2 You can answer it.
3 MR. HARRISON: Go ahead. I haven't
4 directed him not to answer.
5 A. Well, as I stated, it was to provide a
6 statistical summary of the data, provide some
7 frame of reference for setting standards at
8 Park inflows to become generally familiar with
9 the data for the ONRW process. But it's hard
10 to distinguish that process from my other
11 involvement in the case.
12 Q. If you could turn to Exhibit 43, does this
13 reflect some type of trend analysis?
14 A. This reflects a preliminary statistical summary
15 of the data from inflow and marsh stations.
16 Part of that summary may include screening for
17 trends.
18 Q. What parts of the analysis here reflect
19 screening for trends, if you can direct me to
20 the terms that would bear on that issue,
21 please?
22 MR. HARRISON: Object to form. He said
23 that it might. If you give him a minute to
24 look at it, maybe he can find it.
DEPOSITION OF WILLIAM W. WALKER, JR.
1005
1 MS. AHEARN: Well, the terms are all
2 listed right there at the top of the first
3 page.
4 MR. HARRISON: I know, Counsel. But he
5 said it might reflect, and the nature of your
6 question or characterization is that it does.
7 I'm not saying it does or does not. I'm just
8 objecting to your mischaracterization.
9 (Witness examining document)
10 A. It's been awhile since I have looked at this.
11 I believe that on the right-hand side the
12 columns identified as T, SIG, and then on the
13 far right &/YR may pertain to a trend analysis.
14 Q. Is that a t-test for trend in residuals from
15 regressing concentration against flow?
16 A. That could be what the analysis involved. The
17 details, I don't remember.
18 MR. HARRISON: I would just ask the
19 witness to be somewhat certain of his answer.
20 We are getting a lot of coulds and mays. If
21 there's something else that would help you
22 assure yourself one way or the other, I think
23 the record will be better served to avoid
24 getting speculation in the record.
DEPOSITION OF WILLIAM W. WALKER, JR.
1006
1 Q. Under Calculation Methods, the entries
2 Method 2, Method 6, Interpol, do those refer to
3 any particular program or routine that you run
4 on your computer?
5 A. Yes.
6 Q. Do you recall in what directory those programs
7 would be found?
8 A. It would be a program in the directory
9 identified with the word FLUX, F-L-U-X. Yes.
10 It would be in the directory TOOLS\FLUX.
11 Q. Are there other entries in Exhibit 18, the
12 printout of computer directories, that would
13 refresh your recollection on what was involved
14 in the trend analysis in 43?
15 (The witness gave no response.)
16 Q. Dr. Walker, if you would like, it's getting
17 late. I have a couple more questions I'd like
18 to ask you, and we can move off this set of
19 exhibits. Perhaps if you would like to
20 ruminate over this overnight, if some of the
21 details of this analysis come to you by
22 morning, we can return to it.
23 A. I can say the directory TOOLS\OTREN may contain
24 some data files and/or programs that are
DEPOSITION OF WILLIAM W. WALKER, JR.
1007
1 relevant to Exhibits 43, 44. There may be
2 others but --
3 Q. Under the column SIG on Exhibit 43, is there a
4 number, a threshold, you should look for to
5 determine whether the results are significant?
6 A. One can select any particular significance
7 level that one desires for the purposes of
8 determining significant results.
9 Q. In screening for the existence of any trend,
10 what would be the significance level you would
11 recommend here?
12 A. Well, I don't recall whether -- what these SIG
13 levels are, whether they're one-tailed or two-
14 tailed SIG levels. And to be consistent with
15 the trend analysis that I have performed, I
16 would use, I guess, point -- if they're
17 two-tailed tests, we would use a significance
18 level of .1 as a screening criterion.
19 But again, the screening criterion is
20 quite arbitrary. It depends upon what level of
21 risk one wishes to make decisions.
22 Q. If I could just ask you a couple of questions
23 on Exhibit 42, I'd be at a good stopping point.
24 In Exhibit 42 when you --
DEPOSITION OF WILLIAM W. WALKER, JR.
1008
1 (Pause)
2 Q. When you looked at the database prior to
3 October '83 for the S12 structures, did you
4 find any significant indication of trend for
5 total phosphorus? I'd refer you to page 4 if
6 you need to see where that analysis is
7 reflected.
8 A. Well, I'd like to emphasize that the methods
9 here -- the methods that I'm using for
10 screening for trend at this particular -- in
11 this particular exhibit are not what I consider
12 to be the most appropriate methods, the most
13 powerful methods; that is, the Seasonal Kendall
14 test. And also, in this particular exhibit I
15 am not looking at effects of hydrologic
16 factors.
17 But in the -- for this particular time
18 frame, October '78 through September '83, it
19 appears that using the test that was used in
20 this test, the significance levels were between
21 .42 and .78 for the various structures during
22 that particular time frame.
23 Q. Does that give you an indication that there was
24 likely a trend in total phosphorus for this
DEPOSITION OF WILLIAM W. WALKER, JR.
1009
1 time period?
2 A. As I said, there was no adjustment. It turns
3 out that in this particular time frame, 1983
4 was a very wet year, and that could influence
5 the results of the test. And I'm not using the
6 most -- the best -- what I consider the best
7 method for testing for trend. This was a very
8 preliminary analysis using only a portion of
9 the record.
10 Q. How would the fact that '83 was a wet year
11 influence the results?
12 A. Because in 1983 it was a wet year, and the
13 concentrations of phosphorus during that year
14 tended to be low. And that is reflected in
15 some of the scatter plots that we have
16 previously discussed today under -- I believe
17 it would be Exhibit No. 39, for example, shows
18 indications of concentrations tending to be
19 lower during wet years.
20 Q. When you analyzed in Exhibit 42 for the period
21 of record October of '83 through September of
22 1989 for total phosphorus at the S12
23 structures, did you find indications of any
24 significant trend? I'd refer you to page 6 of
DEPOSITION OF WILLIAM W. WALKER, JR.
1010
1 Exhibit 42.
2 MR. HARRISON: This is the time frame
3 between '83 and '89 now as opposed to the
4 earlier time frame?
5 MS. AHEARN: Well, Mr. Harrison, I'll
6 refer you to page 6.
7 Q. And in these data you have sample dates that
8 show you the periods under consideration.
9 A. Under Period No. 3 for total phosphorus during
10 that time frame, the test significance levels
11 ranged from zero to .3. And using the
12 criterion of .1, there were increasing -- there
13 were -- there were increasing trends indicated
14 at, it appears, two stations, S183 and S332.
15 Q. But not at the S12 structures?
16 A. But not at the S12 structures. It's important
17 to note that when you are testing for trend
18 over a given time period, if you divide up the
19 time period into little slices, you are
20 reducing severely the probability of detecting
21 any change. If you want to detect a change
22 over a certain time period, you should use the
23 entire period of record which is reflected in
24 Time Period No. 1.
DEPOSITION OF WILLIAM W. WALKER, JR.
1011
1 Q. When you did that for the S12 structure for
2 total phosphorus, did you find indications of a
3 significant trend?
4 A. In the case of Period No. 1, it appears that
5 significant increasing trends were indicated
6 for all of the structures.
7 Q. Is this pattern consistent with a step-change
8 trend?
9 A. Not necessarily.
10 Q. Is it consistent, though?
11 A. It does not in any way support or test a
12 hypothesis of a step change.
13 Q. Does it disprove a hypothesis of a step change?
14 A. No, it does not disprove a hypothesis of a step
15 change.
16 MS. AHEARN: Let's stop.
17 (Deposition adjourned at 5:34 p.m.)
18
19
20
21
22
23
24
DEPOSITION OF WILLIAM W. WALKER, JR.
1012
1 Excerpt from Rule 30(e):
2 Submission to Witness; Changes; Signing.
3 When the testimony is fully transcribed,
the deposition shall be submitted to the
4 witness for examination and shall be read to or
by him, unless such examination and reading are
5 waived by the witness and by the parties. Any
changes in form or substance which the witness
6 desires to make shall be entered upon the
deposition by the officer with a statement of
7 the reasons given by the witness for making
them.
8
*****************************************************
9
I, WILLIAM W. WALKER, JR., have examined
10 the above transcript of my testimony and it is
true and correct to the best of my knowledge,
11 information and belief. Any corrections are
noted on the errata sheet.
12
Signed under the pains and penalties of
13 perjury this day of ,
1990.
14
15 _____________________________
Deponent's Signature
16
17 Subscribed and sworn to before me this
day of , 1991.
18
19 ______________________________
Notary Public
20
21 My Commission Expires:
22
____________________________
23
24
DEPOSITION OF WILLIAM W. WALKER, JR.
1013
1 COMMONWEALTH OF MASSACHUSETTS)
) ss.
2 COUNTY OF PLYMOUTH )
3
I, Linda Marie MacDonald, a Notary
4 Public within and for the Commonwealth of
Massachusetts, duly commissioned, qualified and
5 authorized to administer oaths and to take and
certify depositions, do hereby certify that
6 heretofore, on the date cited above, the
witness personally appeared before me at the
7 above location and testified in the
above-captioned case; that the said witness was
8 by me duly sworn to testify to the truth, the
whole truth and nothing but the truth; that
9 thereupon and while said witness was under
oath, the deposition was taken down by me in
10 machine shorthand at the time and place therein
named and was reduced to typewriting
11 thereafter.
12
I further certify that the said
13 deposition constitutes a true record of the
testimony given by the said witness.
14
15 I further certify that I am not
interested in the event of this action.
16
17 IN WITNESS WHEREOF, I have hereunto
subscribed my hand this 22nd day of February,
18 1991.
19
___________________________________
20 Notary Public in and for the
Commonwealth of Massachusetts
21
My Commission expires
22 November 29, 1996.
23
24
DEPOSITION OF WILLIAM W. WALKER, JR.
