Full opinion text
FINDINGS & ORDER RE: EXPERT WITNESSES JENKINS, Senior District Judge. TABLE OF CONTENTS FINDINGS & ORDER RE: EXPERT WITNESSES I.EXPERT WITNESSES & FED. R. EVID. 702 .!..1271 A. Rule 702, Gatekeeping and the Two R’s: Reliability and Relevance_1271 B. Reliability: Specific Findings Required.1272 C. Expert Opinions & the Ultimate Issue of Injury.1273 D. Relevance & Admissibility: Fed.R.Evid. 401,402, 403 .1275 II. ANALYSIS & FINDINGS RE: EXPERT WITNESSES :.1276 A. Plaintiffs’ Damages Experts: Dr. Brookshire & Mr. Johnson .1276 B. Dr. Dennis E. Williams.1277 1. Dr. Williams’ Plume Volume & “Buffer Zone” Estimates.1277 2. Defendants’ Rule 702 and Relevancy Objections.1280 3. Dr. Williams’ Qualifications.1281 4. Groundwater Flow/Contaminant Transport Modeling.1281 5. Reliability, Uncertainty & “Kriging”.1281 6. Reliability, Helpfulness & Relevance .1283 7. Plume Volumes & Contaminants Attributable to Non-Parties.1285 8. “Buffer Zone” Volume & Loss of Extractive Services.1286 9. Estimated Plume Volume & the Ongoing EPA Remediation.1286 10. Reliability of Dr. Williams’ Methods and Application.1287 11. Dr. Williams’ Estimated “Lost Safe Yield” .1289 12. Summary.1295 C. Dr. Donald E. Myers.1296 D. Dr. John W. Hawley.1296 E. The Defendants’ Experts.1297 1. The Hydrologists:.1298 a. Steven P. Larson.1298 b. Gerald E. Grisak.1299 c. Dr. Matthew Davis.1300 2. The Civil Engineers:.1301 a. John A. Connor.1301 b. John Billiard.1302 c. Phillip Soice .1303 d. Dennis R. Cooper.1304 3. Prof. Emlen Hall.1305 4. The Natural Resource Economists.1306 a. Theodore Tomasi.1306 b. Dr. William H. DesVousges.1307 III. CONCLUSION.1308 For some time, court and counsel have been engaged in an extended Pre-Trial Conference in this case, attempting to identify and define those genuine issues of fact that need to be resolved through trial. (See Memorandum Opinion and Order, filed April 6, 2004 (dkt. no. 1067), passim.) At the August 6-8, 2003 Pretrial Conference, the court heard, considered and granted defendant General Electric Company’s motion for an evidentiary hearing concerning certain expert witnesses under Fed.R.Evid. 702, setting that hearing to commence on December 9, 2003. (See Minute Entry, dated August 6-8, 2003 (dkt. no. 1014), at 5-6, 7-8; Order, filed September 2, 2003 (dkt. no. 1015), at 3.) From December 9 through December 12, 2003, and continuing through January 7 and 8, 2004, the court heard testimony from Dennis E. Williams, David S. Brook-shire, Stephen B. Johnson, Steven P. Larson, Gerald E. Grisak, Matthew Davis, Emlen Hall, John A. Connor, John Billiard, Phillip Soice, Dennis Cooper, Theodore Tomasi, Donald E. Myers, John W. Hawley, and William H. DesVousges. The court also heard argument by counsel concerning these experts and Plaintiffs’ damages theories. The court took those matters under advisement. (See Minute Entry, dated December 9-12, 2003 (dkt. no. 1059); Minute Entry, dated January 7-8, 2004 (dkt. no. 1066).) The court has heard, reviewed and considered the proffered expert testimony in light of the requirements of Fed.R.Evid. 702, as construed in Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 113 S.Ct. 2786, 125 L.Ed.2d 469 (1993), Kumho Tire Co. v. Carmichael, 526 U.S. 137, 119 S.Ct. 1167, 143 L.Ed.2d 238 (1999), and more recently, Dodge v. Cotter Corp., 328 F.3d 1212, 1221-29 (10th Cir.), cert. denied, — U.S. -, 124 S.Ct. 533, 157 L.Ed.2d 408 (2003), as well as considerations of relevance and admissibility under Fed.R.Evid. 401, 402 and 403. I. EXPERT WITNESSES & FED. R. EVID. 702 A. Rule 702, Gatekeeping and the Two R’s: Reliability and Relevance “It is by now well established that Fed.R.Evid. 702 imposes on a district court a gatekeeper obligation to ‘ensure that any and all scientific testimony or evidence admitted is not only relevant, but rehable.’ ” Dodge v. Cotter Corp., 328 F.3d 1212, 1221 (10th Cir.2003) (quoting Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 589, 113 S.Ct. 2786, 125 L.Ed.2d 469 (1993)). This gatekeeper function requires the judge to assess the reasoning and methodology underlying the expert’s'opinion, and determine whether it is both scientifically valid and applicable to a particular set of facts.... The Supreme Court has made clear that “where [expert] testimony’s factual basis, data, principles, methods, or their application are called sufficiently into question ... the trial judge must determine whether the testimony has ‘a reliable basis in the knowledge and experience of [the relevant] discipline.’ ” Id. at 1221-22 (citations omitted) (quoting Kumho Tire Co. v. Carmichael, 526 U.S. 137, 149, 119 S.Ct. 1167, 143 L.Ed.2d 238 (1999) (quoting Daubert, 509 U.S. at 592, 113 S.Ct. 2786)). Accord United States v. Velarde, 214 F.3d 1204, 1208 (10th Cir. 2000). Daubert lists four “non-exclusive” factors that bear upon Rule 702 reliability of scientific testimony: (1) whether the opinion at issue is susceptible to testing and has been subjected to such testing; (2) whether the opinion has been subjected to peer review; (3) whether there is a known or potential rate of error associated with the methodology used and whether there are standards controlling the technique’s operation; and (4) whether the theory has been accepted in the scientific community. Daubert, 509 U.S. at 593-94, 113 S.Ct. 2786. [T]he list is not exclusive, and district courts applying Daubert have broad discretion to consider a variety of other factors. Kumho Tire, 526 U.S. at 150, 119 S.Ct.- 1167 (“[W]e can neither rule out-, nor rule in, for all cases and for all time the applicability of the factors mentioned in Daubert .... Too much depends upon the particular circumstances of the particular case at issue.”). Dodge v. Cotter Corp., 328 F.3d at 1222. ’ The party proffering an expert’s testimony “need not' prove that the expert is undisputably correct or that the expert’s theory is ‘generally accepted’ in the scientific community.” Mitchell v. Gencorp Inc., 165 F.3d 778, 781 (10th Cir.1999). Instead, the proffering party “must show that the method employed by the expert in reaching the conclusion is scientifically sound and that the opinion is based on facts which satisfy Rule 702’s reliability requirements.” Dodge v. Cotter, 328 F.3d at 1222 (citing Mitchell, 165 F.3d at 781). Under Daubert, “any step that renders the analysis unreliable ... renders the expert’s testimony inadmissible. This is true whether the step completely changes a reliable methodology or merely misapplies that methodology.” Mitchell, 165 F.3d at 782 (quoting In re Paoli R.R. Yard PCB Litigation, 35 F.3d 717, 745 (3d Cir.1994)). Where scientific expertise is asserted “It is critical that the district court determine “whether the evidence is genuinely scientific, as distinct from being unscientific speculation offered by a genuine scientist.’ Id. at 783 (quoting Rosen v. Ciba-Geigy Corp., 78 F.3d 316, 318 (7th Cir.1996)).” Dodge v. Cotter Corp., 328 F.3d at 1222. Not limited to scientific subjects, the gatekeeping requirement extends to all expert opinion testimony, and as gatekeeper, a district court should “make certain that an expert, whether basing testimony upon professional studies or personal experience, employs in the courtroom the same level of intellectual rigor that characterizes the practice of an expert in the relevant field.” Kumho Tire, 526 U.S. at 152, 119 S.Ct. 1167. As this court has often observed, the witness may be an expert, and the witness may have an opinion, but it may not be an expert opinion. In addition to reliability, Rule 702 further requires that the evidence or testimony “assist the trier of fact to understand the evidence or to determine a fact in issue.” According to Daubert, This condition goes primarily to relevance. “Expert testimony which does not relate to any issue in the case is not relevant and, ergo, non-helpful.” 3 Weinstein & Berger ¶¶ 702[02], p. 702-18. See also United States v. Downing, 753 F.2d 1224, 1242 (C.A.3 1985) (“An additional consideration under Rule 702 — and another aspect of relevancy— is whether expert testimony proffered in the case is sufficiently tied to the facts of the case that it will aid the jury in resolving a factual dispute”). The consideration has been aptly described by Judge Becker as one of “fit.” Ibid. “Fit” is not always obvious, and scientific validity for one purpose is not necessarily scientific validity for other, unrelated purposes. 509 U.S. at 591,113 S.Ct. 2786. Under Rule 702, then, a district court must determine whether (1) the proposed witness is a qualified expert in the area in which he or she is being offered as an expert; (2) the proposed expert’s testimony is reliable and (3) the expert’s testimony will assist the trier of fact because it fits relevant issues in the case. See In re Paoli Railroad Yard PCB Litigation, 35 F.3d 717, 741-43 (3d Cir.1994) (citing Dau-bert, 509 U.S. at 595, 113 S.Ct. 2786). The proffering party must establish the expert’s qualifications and the reliability and fit of the proposed testimony by a “preponderance of proof.” In re TMI Litigation, 193 F.3d 613, 663 (3d Cir.1999). B. Reliability: Specific Findings Required “A natural requirement of the gatekeeper function is the creation of a ‘sufficiently developed record in order to allow a determination of whether the district court properly applied the relevant law.” Dodge v. Cotter Corp., 328 F.3d at 1223 (quoting Goebel v. Denver & Rio Grande W. R.R. Co., 215 F.3d 1083, 1087 (10th Cir.2000)). In Velarde, we observed that “Kumho and Daubert make it clear that the [district] court must, on the record make some kind of reliability determination.” Thus, we held in Goebel that when faced with a party’s objection, a district court “must adequately demonstrate by specific findings on the record that it has performed its duty as gatekeeper.” 215 F.3d at 1088 (emphasis added). “Without specific findings or discussion on the record, it is impossible on appeal to determine whether the district court carefully and meticulously reviewed the proffered scientific evidence or simply made an off-the-cuff decision to admit the expert testimony.” Id. (quotations omitted). Id. (emphasis in original). Moreover, under Rule 702, the court must “determine reliability in light of the particular facts and circumstances of the particular case,” Kumho Tire, 526 U.S. at 158, 119 S.Ct. 1167, recognizing the quintessential importance of context to the question of whether an expert’s opinions may be helpful to the trier of fact. C. Expert Opinions & the Ultimate Issue of Injury Expert witnesses may offer an opinion on an ultimate issue, Fed.R.Evid. 704(a), ’but to be helpful to the trier of fact, that opinion must necessarily take into account the material facts that bear upon the ultimate issue and must explicitly explore its underlying criteria. See, e.g., United States v. Simpson, 7 F.3d 186,188-89 (10th Cir.1993) (upholding exclusion under Rule 704 when the “expert merely states an opinion on an ultimate issue without adequately exploring the criteria upon which the opinion is based,” so that “the jury is provided with no independent means by which it can reach its own conclusion or give proper weight to the expert testimony”). An opinion on an ultimate issue that omits or ignores material facts bearing upon the ultimate issue cannot be helpful to the trier of fact. Cf. Kieffer v. Weston Land, Inc., 90 F.3d 1496, 1499 (10th Cir.1996) (expert witness “acknowledged he was unable to formulate an opinion on the ultimate issue in dispute,” whether wiring of a vending machine was defective, because of a missing machine part). The question of injury to the State’s interests in South Valley groundwater is an ultimate issue. Establishing an injury to the State’s interest in making groundwater available for appropriation requires proof of a net reduction in the total volume of water that may be extracted from the Middle Rio Grande Basin aquifer as determined by the State Engineer, either to satisfy existing water rights or new applications. This reduction may take the form of an impairment of the exercise of existing water rights, or may be reflected in a reduction in the volume of unappropriated water otherwise available for use. Plaintiffs addressed “injury” in terms of two groundwater services: (1) extractive use as “a drinking water source”; and (2) in situ service as “a ‘drought reserve,’ ” asserting that the State’s interests in groundwater have been injured by the permanent loss of both. Consistent with this approach, Plaintiffs’ expert, Dr. Dennis E. Williams, performed analysis and formulated opinions concerning both services, first by estimating the volume of the plume of contaminated in situ groundwater in excess of New Mexico drinking water standards as well as the volume, of a 4000-foot “buffer zone” surrounding that plume required to prevent migration of the plume toward active wells; then Dr. Williams estimated the hydrological “safe yield” of the portion of the aquifer containing the estimated plume and buffer zone volumes as a means to estimate the alleged “lost safe yield” due to the contamination. Plaintiffs having failed to raise a triable issue concerning loss of extractive services, the court has framed the “injury” issue for trial solely in terms of Plaintiffs’ alleged loss of in situ groundwater service: “What is the volume of in situ groundwater beneath the South Valley Site that has been injured and rendered unavailable (e.g., as drought reserve) for use as drinking water because of that chemical contamination [attributable to the Defendants]?” (Id. at 137.) To be helpful to the trier of fact, the proffered expert opinion must “fit,” i.e., be relevant to at least some of the facts bearing upon the determination of this issue. To embrace the ultimate issue of injury-under Rule 704(a), the proffered expert opinion should account for all of the material factors that bear upon that ultimate issue. In this case, several material factors bear upon the issue of loss of in situ groundwater service as “drought reserve”: (1) the total volume of groundwater and the hydrological “safe yield” of the Middle Rio Grande Basin aquifer; (2) the volume of groundwater polluted by contaminants exceeding New Mexico drinking water standards; (3) the volume of groundwater polluted by contaminants originating from sources other than the Defendants in this action; (4) legal or administrative restrictions on extraction of Middle Rio Grande Basin groundwater; (5) the exercise of existing water rights by water users, e.g., the City of Albuquerque; and (6) in the specific context of this action, the volume of groundwater encompassed within the intended scope of the EPA “Plant 83/Gen-eral Electric” remediation under the Comprehensive Environmental Response, Compensation and Liability Act of 1980 (“CERCLA”), Pub.L. 96-510, 94 Stat. 2767, codified at 42 U.S.C. §§ 9601 et seq. (2000). (See Memorandum Opinion and Order, filed April 6, 2004 (dkt. no. 1067), 335 F.Supp.2d at 1262-63, 2004 WL 2073976, at *53-54.) D. Relevance & Admissibility: Fed. R.Evid. 401, 402, 403 “Relevant evidence” refers to “evidence having any tendency to make the existence of any fact that is of consequence to the determination of the action more probable or less probable than it would be without the evidence.” Fed.R.Evid. 401. Generally, “Mil relevant evidence is admissible” and “[e]vidence which is not relevant is not admissible,” Fed.R.Evid. 402, but in practice, relevant evidence is excluded as required by the Constitution, the law, or court rules, such as the hearsay rule, Fed. R.Evid. 802, which in turn is subject to multiple exceptions. See Fed.R.Evid. 803. Moreover, relevant evidence that escapes these limitations may nevertheless be excluded “if its probative value is substantially outweighed by the danger of unfair prejudice, confusion of the issues, or misleading the jury, or by considerations of undue delay, waste of time, or heedless presentation of cumulative evidence.” Fed.R.Evid. 403. II. ANALYSIS & FINDINGS RE: EXPERT WITNESSES A. Plaintiffs’ Damages Experts: Dr. Brookshire & Mr. Johnson Recently, this court ruled upon the scope of Plaintiffs’ remaining state law claims and the appropriate measure of damages to be applied at trial. (See Memorandum Opinion and Order, filed April 6, 2004 (dkt. no. 1067), 335 F.Supp.2d 1185, at. 1221-33, 1250-51, 1259-63, 2004 WL 2073976, at *22-31, 44, 51-54.) The court’s rulings have rendered significant portions of the testimony of Plaintiffs’ damages experts, Dr. David S. Brookshire and Mr. Stephen B. Johnson, irrelevant to the remaining triable issues. Dr. Brookshire’s analysis and opinions concerning the market value replacement cost of a volume of groundwater totally and permanently lost to use has no bearing upon damages to be measured by the cost of restoration of the affected groundwater to use as drinking water, and therefore cannot be helpful to the trier of fact in this case. Similar analysis and opinion, testimony by Mr. Johnson concerning the cost of replacing the storage capacity of a portion of the Middle Rio Grande Basin aquifer through construction and maintenance of a large surface storage reservoir likewise cannot be helpful to the trier of fact where the Plaintiffs have no cognizable claim for loss of the aquifer’s storage capacity. {See Memorandum Opinion and Order, filed April 6, 2004 (dkt. no. 1067), 335 F.Supp.2d at 1205, 2004 WL 2073976, at *10) The. court need not examine the Rule 702 reliability of Dr. Brookshire’s market value replacement cost computations or Mr. Johnson’s construction and water replacement cost estimates because neither analysis remains relevant to the issues remaining to be tried. See Kerrigan v. Maxon Ind., 223 F.Supp.2d 626, 638-39 (E.D.Pa.2002) (“ ‘There must be a valid connection between the expertise in question and the inquiry being made in the case.’ Main Street Mortgage v. Main Street Bancorp, Inc., 158 F.Supp.2d 510, 518 (E.D.Pa.2001).”) Mr. Johnson also offered opinion testimony concerning the advisability of wellhead treatment to restore contaminated groundwater beneath the South Yalley Site to use as drinking water. (Transcript of Hearing, dated December 10, 2003 A.M. Session (“Tr. 12/10/2003 AM”), at 2782:20-2785:18, 2796:25-2798:17 (testimony of Stephen Johnson).) In this respect, Mr. Johnson largely summarizes his observations as to his own experience and the experience of others in designing and implementing wellhead treatment systems at other locations. As to this portion of Mr. Johnson’s proffered testimony, the • Defendants object that his proffered opinion is “litigation driven,” and “not followed by Mr. Johnson in his practice outside the courtroom,” where “he has never advised a client that groundwater contaminated with volatile organic compounds at levels below drinking water standards is permanently lost for all beneficial uses,” (GE Supp. Mem. at 22 (citing Transcript of Hearing, dated December 10, 2003 PM Session (“Tr. 12/10/2003 PM”), at 2835:11-2837:4, 2869:7-2870:25, 2872:19-2875:5 (testimony of Stephen Johnson))), and that his “opinion regarding the viability of wellhead treatment is not based on any kind of scientific or empirical analysis” and “conflicts with his prior experience and that of the State of New Mexico,” and should therefore be excluded. (Defs. Supp. Br. at 37-38.) Plaintiffs did not respond to these objections. (See Plaintiffs Joint Opposition to Various Motions to Exclude Stephen Johnson, filed January 5, 2004 (dkt. no. 1051); cf. Transcript of Hearing, dated January 8, 2004 P.M., at 4128:24-4129:10 (Mr. Lewis); id. at 4136:15-4137:6 (Mr. Fowler).) At this point, the court concludes that portions of Mr. Johnson’s opinion testimony concerning wellhead treatment as a remedy at South Valley are admissible at least as a summary of the experience of someone working in the field. B. Dr. Dennis E. Williams Originally, Plaintiffs asked Dr. Williams to quantify the loss of groundwater “safe yield” and the total volume of in situ groundwater that has been lost to use because of the chemical contamination at South Valley. Acting upon Plaintiffs’ request, Dr. Williams made an estimate of the initial contamination of the plumes, and then using groundwater hydrologic models, I simulated the plumes forward into time, and then estimated the loss of safe yield and the volume of the aquifer. So those essentially are ... the three main tasks that I was charged with. (Transcript of Hearing, dated December 9, 2003 (“Tr. 12/9/2003”), at 2398:3-10 (testimony of Dr. Williams).) The question now presented is whether it is reasonable to use Dr. Williams’ modeling approach, along with Williams’ “particular method of analyzing the data, to draw a conclusion regarding the particular matter to which the expert testimony [is] directly relevant,” Kmnho Tire, 526 U.S. at 154, 119 S.Ct. 1167 (emphasis in original), in this case, the question of contaminant plume volume and the consequences that may flow from that estimate. 1. Dr. Williams’ Plume Volume & “Buffer Zone” Estimates Dr. Williams, assisted by others, gathered the available South Valley well sampling data from Jacobs Engineering and other sources, primarily from the last quarter of the year 1992, and selected data to construct a model of a contaminant plume circa 1992. (Id. at 2420:23-2421:22.) Those at the GEOSCIENCE firm who were assisting Dr. Williams used the technique referred to as “kriging” to predict the measurements for geographic points within the plume model where actual 1992 sample data were not available. (Id. at 2404:3-8, 2410:19-2415:7, 2415:19-2419:23, 2645:15-2647:17.) [W]e took the Jacobs database, and it goes in and we developed — we did two steps on the kriging. The first, we kriged the plumes, we used the data to develop the variogram, which is the spatial relationship between the data, and we used that experimental variogram and then the model variogram which resulted from that, to krig the data into our groundwater model cells. (Tr. 12/9/2003, at 2422:1-8.) Next, Dr. Williams and his associates generated a groundwater flow model, and used actual and “kriged” contaminant data in constructing solute transport models based on the groundwater flow model, all in an effort to predict the geographic movement of the contaminated South Valley groundwater over a period of time. (Id. at 2398:5-6, 2422:9-2425:13, 2427:6-15, 2438:14-2439:17, 2440:17-2445:3, 2448:2-2449:8, 2456:18-2458:20, 2459:14-2465:7, 2470:10-2476:13.) Having thus modeled the approximate volume, location and directional flow of the projected contaminant plume beneath the South Valley Site at specific points in time, Dr. Williams then analyzed the contamination problem in terms of long-term containment: The basic principle of delineating, when you have a groundwater contamination problem, the first thing you need to do is understand where it is. In other words, where it is spatially, where it is vertically. So you go through a series of testing, usually drilling, measurements and you want to define the plume and make sure that you certainly understand the margins of the plume, where it is laterally, where it is vertically. And then the second issue is to contain the plume, to try to minimize the spread of the contamination, so to protect the fresh drinking water supplies. (Tr. 12/9/2003, at 2397:6-18 (testimony of Dr. Williams) (emphasis added).) Dr. Williams hypothesized the volume of a “buffer zone” of potable water surrounding the contaminant plume that must remain in place to prevent further movement or flow of the modeled contaminant plume in the direction of active water supply wells. (Id. at 2495:18-2509:5, 2512:2-2513:20, 2527:1-18.) Dr. Williams combined the estimated volume of his modeled contaminant plume with the estimated volume of the “buffer zone” needed to immobilize the plume to estimate the total volume of in situ groundwater impacted by the contamination and thereby lost to use as drinking water over a period of time, and to estimate the lost “safe yield” of potable groundwater from the South Valley portion of the Middle Rio Grande Basin aquifer, past, present and future. (Id. at 2514:4-2515:7, 2524:2-2525:22, 2554:21-2555:11.) Q So in terms of alleging — of talking about the alleged loss of the use of groundwater, what you’re talking about is the alleged loss of safe yield[?] A When you talk of the loss of on an annual basis, that’s correct. (Id. at 2555:1-6.) 2. Defendants’ Rule 702 and Relevancy Objections The Defendants object that the analysis and opinions of Dr. Dennis E. Williams proffered at the December 9 evidentiary hearing “are irrelevant to the elements 'of injury and damages and cannot assist the trier of fact in resolving these issues.” (Supplemental Memorandum of Defendant General Electric Company in Support of Motion to Exclude Expert Testimony of Dennis Williams, David- Brookshire and Stephen Johnson, filed January 9, .2004 (dkt. no. 1058) (“GE Supp. Mem”), at 1.) General Electric argues that Dr. Williams avoids the question “whether — and to what extent — the presence of contamination in excess of drinking water standards has deprived the State of the opportunity to make water available for appropriation by others,” the “sole question that the Court has found to be relevant.” (Id. at 3.) In other words, Dr. Williams has not framed his opinions in terms of the ultimate “injury” issue. GE also objects that Dr. Williams’ opinions “are neither supported by sufficient facts or data, nor are they the product of reliable principles and methods reliably applied to the facts of this case,” and should therefore be excluded under Rule 702. (Id. at 2.) ACF Industries, Chevron and Texaco similarly contend that Dr. Williams’ opinions “are not the product of reliable methods,” are “based ... on mistaken assumptions and improper calculations,” are not rehable “because they do not reflect reality;” and are “not relevant to the case because they fail' to' comply ' with the Court’s rulings on the measure of injury, which is limited to contamination above the federal and state drinking water standards.” (Defendants’ Supplemental Brief in Support of Motions to Strike the Testimony of Dennis Williams, Stephen Johnson and David Brookshire, filed December 29, 2003 (dkt. no. 1044) (“Defs.Supp.Br.”), at 2, 3.) In particular, Defendants argue, Dr. Williams erroneously opines that “hundreds of thousands of acre feet of uncontaminated water are lost,” apparently referring to Williams’ projected “buffer zone” volume. (Id. at 4.) Not only do Williams’ opinions fail to meet Rule 702 standards, the Defendants continue, they should be excluded under Fed.R.Evid. 403 because they may confuse and mislead the jury, citing In re TMI Litigation, 911 F.Supp. 775, 798-99 (M.D.Pa.1996), and C.A. As-socs. v. Dow Chemical Co., 918 F.2d 1485 (10th Cir.1990). See also Fed.R.Evid. 401, 402. The Defendants challenge the relevance and reliability of each step of Dr. Williams’ analysis. See Dodge v. Cotter Corp., 328 F.3d at 1222 (“Under Daubert, ‘any step that renders the analysis unreliable ... renders the expert’s testimony inadmissible. This is true whether the step completely changes a reliable methodology or merely misapplies that methodology.’ Mitchell, 165 F.3d at 782 (quoting In re Paoli R.R. Yard PCB Litigation, 35 F.3d 717, 745 (3d Cir.1994)).”). 3.Dr. Williams’ Qualifications The first question under Rule 702 is whether the proposed witness is a qualified expert in the area in which he is being offered as an expert, viz., “geohydrology” (or “hydrogeology”) and groundwater hydrology, including modeling techniques useful to groundwater hydrology. Dr. Williams is a Research Professor at the University of Southern California, has taught courses in the subject since 1980, and serves as director of the university's geohydrologic laboratory; he is a registered geologist and certified hy-drogeologist in the State of California and a member of the American Institute of Hydrology, and has authored thirty publications. (See Tr. 12/9/2003, at 2389:11-2394:11 (testimony of Dr. Williams).) His groundwater consulting company, GEOSCIENCE Support Services, has conducted business for more than 25 years, mainly working with municipalities and water districts in California and elsewhere. (Id. at 2394:12-2395:21.) Dr. Williams has performed groundwater analyses and modeling in order to define plumes of contaminated water for various clients. (Id. at 2395:22-2396:25, 2422:17-2431:14, 2445:14-2446:3.) The computer-assisted groundwater modeling tools he uses are widely known and well recognized. (Id. at 2431:20-2437:11, 2449:21-2456:8.) Based upon the written materials and testimony in the record, the court is satisfied that based upon his knowledge, education, training and experience in the field, Dr. Williams is a qualified expert in the area in which he is being offered. 4. Groundwater Flow/Contaminant Transport Modeling Assuming relevance, the next question under Rule 702 is whether the proposed expert testimony “is the product of reliable principles and methods.” Fed.R.Evid. 702. The Defendants contend that Dr. Williams’ groundwater flow and contaminant transport modeling “does not reflect reality,” and involve the “use of flawed software” with a starting point “based on incomplete data and unreliable kriging,” viz., the 1992 plume model. (Defs. Supp. Br. at 6.) According to General Electric, Dr. Williams’ modeling predicts a plume volume of 15,000 acre-feet by 2003, yet “the actual groundwater quality data for the same period shows that vast areas within Williams’ predicted plume are either entirely uncontaminated or have chemicals at concentrations below the maximum contaminant levels for drinking water,” suggesting that ‘Williams’ massive plume does not exist in the real world.” (GE Supp. Mem. at 10.) “Consequently, both the model and the Williams opinions based on the model should be excluded from evidence at trial as not accurate and therefore not reliable.” (Id. at 13.) 5. Reliability, Uncertainty & “Krig-ing” “Kriging” serves as a method for estimating specific values of data where the actual values have not been measured. Kriging involves interpolation of known (measured) values to infer the missing values for adjacent data points or locations where no measurement was made. (See Tr. 12/9/2003, at 2645:18-21 (testimony of Dr. Williams).) Kriging necessarily is rooted in knowledge and/or statistical assumptions concerning the nature, properties, and behavior of the subject matter-in this case, groundwater containing dissolved traces of several organic chemicals that may migrate through the heteroge-nous geological constituents of an aquifer, depending upon the effect of various hydraulic forces over time. Moreover, “All interpolation methods are based on a rather intuitive idea, namely that the concentrations of a contaminant are more ‘similar’ for a pair of locations that are close together and less ‘similar’ for locations that are far apart.” That is, the degree of correlation between concentration values for a pair of values is a function of distance and direction. One crucial problem is how to quantify this correlation and in particular how to do it for a particular application, i.e., how to use the data for this purpose. There is seldom ever sufficient information available ... that would allow a mathematical derivation of the spatial correlation function. Instead it must be estimated and modeled from the data.... Kriging thus yields estimated values — estimates that are themselves rooted in estimates. Geostatistical methods, and kriging in particular, are recognized and accepted estimation techniques that find useful application in various contexts. These methods prove to be inescapably uncertain: Absent complete information on the deposition process and absent detailed information on the geohydrological parameters (such as hydraulic conductivity, dispersivity, permeability, etc.) for the subsurface it will not be possible to perfectly determine the concentrations at non-sampled points. Therefore any interpolation method will incorporate some degree of uncertainty, hence the emphasis on the word “estimate” or “predict”.... Geostatistics and the various forms of kriging incorporate uncertainty in the methodology.... Plaintiffs’ experts concede that Dr. Williams’ approach is not the only valid method for estimating the location and volume of a plume of contaminated groundwater, and that other geostatistical methods may be applied to the available data to perform the same task, with varying results. To some extent, the Defendants’ experts have used alternate estimation techniques in evaluating Dr. Williams’ results, and have tested and compared Dr. Williams’ projected plume volume and estimated concentrations against “real-world data” — actual field measurements at corresponding data points collected since the last quarter of 1992. These analyses and comparisons suggest that Dr. Williams’ projections overestimate the plume volume, predicting above-MCL groundwater contamination in 2003 at locations where such contamination did not exist in 2003, (Tr. 12/10/2003 PM, at 2916:6-2925:4 (testimony of Steven Larson)), and understate the effectiveness of the ongoing remediation, which Defendants’ experts opine will eliminate any above-MCL contaminant plume by the year 2016, even using Williams’ model as a basis. (See id. at 2946:14-2948:5; cf. Transcript of Hearing, dated December 11, 2003 P.M. Session (“Tr. 12/11/2003 PM”), at 3445:14-21, 3447:11-3448:21 (testimony of John A. Connor).) 6. Reliability, Helpfulness & Relevance By definition, Dr. Williams’ estimates and projections of plume volume, location and movement over time cannot produce a result with mathematical certainty. Yet they need not promise mathematical certainty in order to be “helpful to the trier of fact” — the third essential query under Rule 702. While expert opinions “must be based on facts which enable [the expert] to express a reasonably accurate conclusion as opposed to conjecture or speculation, ... absolute certainty is not required.” Gomez v. Martin Marietta Corp., 50 F.3d 1511, 1519 (10th Cir.1995) (quotation omitted). In the context of this civil action, we are concerned with facts proven by a preponderance of the evidence, that is, with things more likely than not; we make findings as to that which is probable, though still uncertain. Statistical techniques address facts, values and quantities in terms of probabilities, not certainties — varying shades of grey rather than bold contrasts of black and white. The geostatistieal language of probability meshes with the legal language of preponderance, and an analysis expressed in one may assist in resolving an issue expressed in the other. Or it may not. “Trained experts commonly extrapolate from existing data. But nothing in either Daubert or the Federal Rules of Evidence requires a district court to admit opinion evidence that is connected to existing data only by the ipse dixit of the expert.” General Electric Co. v. Joiner, 522 U.S. 136, 146, 118 S.Ct. 512, 139 L.Ed.2d 508 (1997). As to admissibility of expert opinion, the question is whether “there is simply too great an analytical gap between the data and the opinion proffered.” Id. The court has heard and considered in some detail the Defendants’ experts’ critique of the analyses performed by Dr. Williams in formulating his proffered opinions. The arguments concerning GEOS-CIENCE’S “kriging” analysis re-emphasize the inherent difficulty of quantifying empirical values where those values have not in fact been measured in the field. Indeed, where the accuracy and precision of stated quantities of hazardous substances are important, “ ‘[t]here is no substitute for measurement.’ ” Allen v. United States, 588 F.Supp. 247, 380 (D.Utah 1984), rev’d on other grounds, 816 F.2d 1417 (10th Cir.1987), cert. denied, 484 U.S. 1004, 108 S.Ct. 694, 98 L.Ed.2d 647 (1988). One area of vulnerability of Williams’ projected plume is its apparent conflict with actual below-MCL or “non-detect” measurements obtained from samples collected in the field. (Compare Tr. 12/9/2003, at 2615:11-2616:20, 2651:18-2652:18 (testimony of Dr. Williams) with Tr. 12/10/2003 PM, at 2916:6-2925:4 (testimony of Steven Larson); Tr. 12/11/2003 AM, at 3066:22-3067:17 (testimony of Mr. Grisak); Tr. 12/11/2003 PM, at 3407:5-3408:19 (testimony of Mr. Connor).) Defendants’ experts criticize the calibration of Dr. Williams’ modeling, asserting that Williams and his associates used the wrong method for “relative error” calculation (Tr. 12/10/2003 PM, at 2925:5-2929:2, 2930:18-2933:7 (testimony of Mr. Larson); Tr. 12/11/2003 PM, at 3401:11-3407:4 (testimony of Mr. Connor)), and that sufficient measurement data is available to render modeling unnecessary. (Id. at 3446:3-13.) Plaintiffs respond that Dr. Williams’ modeling was properly calibrated, that the relative error comes well within the “industry standard” of ten percent, and need not be calculated using the logarithms of concentration, or the standard deviation. (See Pltfs’ Joint Resp. (Williams), at 9-10.) They point to Well P83-22D-2, which when drilled in February 2002, detected contaminants as predicted by the Williams modeling. (Id. at 10.) “Does the model predict what happened in the real world from the measured ... data?” (Tr. 12/9/2003, at 2456:13-15 (testimony of Dr. Williams).) From the facts currently in this record, it appears that Dr. Williams’ analysis gives some rough estimate of the nature, extent, and location of contaminated water beneath the South Valley Site based upon selected data, and the relationship between model and measurements in this instance is something more than purely ipse dixit. Defendants’ criticisms of Dr. Williams’ methods of analysis — including the GEOSCIENCE kriging and calibration exercises — are themselves based upon statistical probabilities and estimation techniques, and go to the weight and credibility that the trier of fact should afford to Dr. Williams’ opinions. The statistical tools and methods used by Dr. Williams and his associates in making estimates appear to have “ ‘a grounding in the methods and procedures of science’ based on actual knowledge, not ‘subjective belief or unsupported speculation.’ ” Dodge v. Cotter Corp., 328 F.3d at 1222 (quoting Daubert, 509 U.S. at 590, 113 S.Ct. 2786). His estimates appear to have ‘“a reliable basis in the knowledge and experience of [the relevant] discipline,’ ” Kumho Tire, 526 U.S. at 148, 119 S.Ct. 1167 (quoting Daubert, 509 U.S. at 592, 113 S.Ct. 2786), and appear to be “applicable to a particular set of facts” as required by Rule 702. Daubert, 509 U.S. at 593, 113 S.Ct. 2786. Dr. Williams’ estimates do not fall “outside the range where experts may reasonably differ, and where the jury must decide among the conflicting views of different experts, even though the evidence is ‘shaky.’ ” Kumho Tire, 526 U.S. at 153, 119 S.Ct. 1167. But to be admissible, those estimates must also prove to be relevant to the triable issues in this case. 7. Plume Volumes & Contaminants Attributable to Non-Parties To be relevant to the issues of injury and damages in this case, Dr. Williams’ estimate of plume volumes must encompass chemical contaminants that allegedly may be traced to the conduct of the Defendants named in this action. At least to the extent that it may be distinguished, contamination that is known or believed to be identifiable to non-party sources, e.g., the Univar Edmunds Street facility, has no bearing upon the issues to be tried in this case, and should form no part of any expert analysis of the nature, location or volume of contaminated groundwater to be proffered at trial. Dr. Williams acknowledges that his projected plume volume includes contaminants attributed to the Univar Edmunds Street facility: Q You would agree, would you not, that there is a plume of contamination known as the Univar plume that is separate and distinct from the GE plume, the GE-managed plume? A Yes. Q You included contamination data from the Univar site in your model; isn’t that correct? A Yes. (Tr. 12/9/2003, at 2585:8-12, 2586:2-5 (testimony of Dr. Williams).) According to Steven Larson, one of the Defendants’ experts, Dr. Williams’ projected 2003 plume volume of approximately 15,000 acre-feet incorporates significant non-party contamination: “The plume associated with the Univar monitoring wells was a little over 50 percent of that total calculated contamination exceeding drinking water standards.” (Tr. 12/10/2003 PM, at 2946:3-6 (testimony of Steven Larson).) Benzene contamination accounted for nearly 25 percent of Dr. Williams’ projected 2003 plume volume, (id. at 2945:21-25), but benzene is concentrated under the Univar site. (Tr. 12/9/2003, at 2649:4-14 (testimony of Dr. Williams).) To the extent that Dr. Williams current plume volume projection takes into account identifiable, distinguishable non-party source contamination (e.g., the “Univar plume”), that projection must be excluded because it is not applicable to the facts properly before the court, i.e., not relevant, and likely would be confusing, misleading and needlessly prejudicial. Fed. R.Evid. 401, 403. 8. “Buffer Zone” Volume &.Loss of Extractive Services The Defendants also assail Dr. Williams’ estimated “buffer zone” (and “alternate buffer zone”) volumes, arguing that his projected buffer zone is comprised of potable groundwater that has not been lost to use because of contamination, and cannot be deemed to be part of any alleged injury to the State’s interest. Plaintiffs respond that the buffer zone is necessary to prevent migration of the plume of “above-MCL” contaminated groundwater through the aquifer, which could threaten to taint existing or future supply wells. In this case, Dr. Williams’ estimated “buffer zone” volume is relevant the Plaintiffs’ claims only if the contaminated plume volume is treated as totally and permanently lost and the remedy chosen to address the resulting public health risks is the passive containment of the chemical contaminant plume. By definition, Dr. Williams’ “buffer zone” volumes fall beyond the boundaries of the estimated “above-MCL” contaminant plume, and are usable as drinking water. {See Tr. 12/9/2003, at 2565:7-23, 2567:11-17, 2568:14-19 (testimony of Dr. Williams).) In light of this court’s rulings on the appropriate measure of damages in light of Plaintiffs’ failure to raise a triable issue as to total and permanent loss, {see Memorandum Opinion and Order, filed April 6, 2004 (dkt. no. 1067), 335 F.Supp.2d at 1217-22, 1259-62, 2004 WL 2073976, at *18-22, 51-53), Dr. Williams’ original and alternative “buffer zone” estimates are not relevant to the issue of injury to the State’s interests in groundwater caused by contamination attributable to the defendants. 9. Estimated Plume Volume & the Ongoing EPA Remediation To be helpful to the trier of fact, Dr. Williams’ plume volume modeling must predict the quantity and location of persistent above-MCL groundwater contamination outside the scope of the existing EPA/GE remediation, excluding contaminated water within its reach. To some extent, at least, Dr. Williams’ projected plume volume predicts persistent contamination beyond the reach of the existing remedial system. In the Declaration of Dr. Dennis E. Williams, dated August 30, 2002, he observed that based upon his groundwater flow and transport modeling of the contaminant plume, “the GE pump and treat system does not remediate contaminants outside the capture radius of its extraction wells, which leaves a significant amount of the total contaminant plume unremediated.” {Id. at 7 Í! 20.) “Consequently,” Dr. Williams continues, “the contaminants will persist in the groundwater for at least two hundred years, or even longer, after the remediation efforts have ceased in year 2020.” (Id.) By the time of his testimony on December 9, 2003, Dr. Williams had softened this estimate somewhat, predicting that the contaminant plume would persist for “at least 100 years, and probably longer,” taking into consideration the EPA/GE remediation system, (Tr. 12/9/2003, at 2541:9-10, 2542:1-2543:3), but he observed that there are “deep hits that are below the depth of the deepest GE extraction well,” (id. at 2650:11-12): “the deep zone [remediation system] doesn’t go much below 4,600 feet, [and] there’s some known contamination quite a bit deeper,” (id. at 2542:17-19), as reflected in data gathered in connection with the EPA/GE remediation. (Id. at 2465:24-2466:22, 2467:3-2470:2, 2491:18-2492:1, 2493:10-2494:25, 2531:21-2541:10, 2542:12-2548:22.) Part of that persistent contamination appears to be attributable to the Univar Ed-munds Street facility, as discussed above, and to be helpful to the trier of fact, Dr. Williams’ plume volume estimates must explicitly address only the contamination attributable to the Defendants, and then only to the extent that it persists beyond the scope of the EPA/GE remediation. 10. Reliability of Dr. Williams’ Methods and Application At this stage, having reviewed and considered the testimony proffered at the evi-dentiary hearing, as well as the memoran-da submitted by counsel and references cited by the witnesses, the court is persuaded that the groundwater flow and solute transport modeling tools used by Dr. Williams and his associates at GEOSCIENCE, including the interpolation of data values using “kriging,” are generally accepted in the field of geostatistics and are generally considered to be reliable as tools to be used to arrive at an estimate, recognizing at the same time that an estimate proves inescapably uncertain. More problematic is the question whether Dr. Williams and his associates “applied the principles and methods reliably to the facts of the case,” Fed.R.Evid. 702, in performing their analyses and preparing their estimates. As his opinions have evolved in this proceeding, Dr. Williams has acknowledged errors in his original analyses in light of certain critiques of his work by the Defendants’ experts. (Tr. 12/9/2003, at 2601:21-2603:2.) Other criticisms appear to reflect differing preferences in approach to geostatistical analysis, e.g., hand-contouring v. kriging of estimated values, or use of various functions in calibrating models and computing relative error. Each approach has its advocate, and Dr. Williams’ geostatistical preferences have their own advocate as well. (See Transcript of Hearing, dated January 7, 2004 P.M. Session (“Tr. 1/7/2004 PM”), at 3762:6-3776:21 (testimony of Dr. Donald E. Myers).) Looking to the Daubert factors, (1) Dr. Williams’ modeling analysis is susceptible to, and has been subject to testing by Defendants’ experts; (2) Dr. Williams recounts some minimal peer review of his groundwater flow modeling, (Tr. 12/9/2003, at 2624:6-2627:12, 2643:5-2645:14), and Plaintiffs proffer the opinions of another geostatician, Dr. Donald E. Myers, concerning the validity of Williams’ methods; (3) the relative error rates of Dr. Williams’ modeling vary depending on how they are calculated, (id. at 2630:22-2634:9), but it is evident that “there are standards controlling the technique’s operation” about which there is substantial agreement; and (4) as noted above, the modeling tools and krig-ing techniques used by Dr. Williams and his associates are known and generally accepted in the geostatistical. community as being reliable, at least as a means of visualizing bodies of water as yet unseen and estimating data values as yet unmeasured. Daubert instructs that Rule 702 admissibility is governed by Fed.R.Evid. 104(a): Faced with a proffer of expert scientific testimony, then, the trial judge must determine at the outset, pursuant to Rule 104(a), whether the expert is proposing to testify to (1) scientific knowledge that (2) wili- assist the trier of fact to understand or determine a fact in issue. This entails a preliminary assessment of whether the reasoning or methodology underlying the testimony is scientifically valid and of whether that reasoning or methodology properly can be applied to the facts in issue. 509 U.S. at 592-93, 113 S.Ct. 2786 (footnotes' omitted).. In this setting, “it is plain that the proponent must make more than a prima facie showing ... that a technique is reliable.” United States v. Downing, 753 F.2d 1224, 1240 n. 21 (3d Cir.1985). “This does not mean that plaintiffs have to prove their case twice — they do not have to demonstrate to the judge by a preponderance of the evidence that the assessments of their experts are correct, they only have to demonstrate by a preponderance of the evidence that their opinions are reliable.” In re Paoli Railroad Yard PCB Litigation, 35 F.3d at 744 (emphasis in original & footnote omitted). On a preliminary basis, then, the court finds that, more likely than not, geostatis-tical principles and methods were applied to the facts of this case by Dr. Williams’ analyses of projected plume volume, composition, and location in a sufficiently reliable fashion to be of some assistance to the trier of fact. Based upon the record now before this court, it appears Dr. Williams’ projected contaminant plume gives some indication of how much above-MCL water exists and where it may be found. Defendants’ experts are free to propound their own analyses and estimates using tools they choose, and their criticisms of Dr. Williams’ approach go to its weight and credibility. See Fed.R.Evid. 104(e) (“This rule does not limit the right of a party to introduce before the jury evidence relevant to weight or credibility.”) In their current form, however, Dr. Williams’ estimates of contaminant plume volume and “buffer zone” volume are not admissible for reasons of relevance under Fed.R.Evid. 401, 402, 403 and 702, apart from the questions of Rule 702 reliability raised by the Defendants. Estimation of volumes of contaminated groundwater attributable to nonparty sources does not advance the inquiry in this case; nor does any portion of the projected plume volume that falls within the scope of the ongoing EPA/GE remediation. And where Plaintiffs’ remedy is to be measured by the cost of restoration, a “buffer zone” 'volume based upon a passive “containment” remedy simply does not fit. Similar problems plague Dr. Williams’ estimate of “lost safe yield.” 11. Dr. Williams’ Estimated “Lost Safe Yield” Relying on his estimated plume and buffer zone volumes, Dr. Williams also prepared an estimate of “lost safe yield” from his model area of the aquifer beneath the South Valley Site. Defendants insist that Dr. Williams’ current estimate of the “lost safe yield” must be excluded for being neither relevant nor reliable. First, there appears to be a lack of practical correspondence between the safe yield hypothesized by Williams for his model area at South Valley and the safe yield of the entire Middle Rio Grande Basin aquifer as borne out by existing hydrological data. The Defendants object that Dr. Williams’ analyses “treat the South Valley as if it were a discrete and separate source of drinking water subject to no legal or administrative constraints,” (Defs. Supp. Br. at 7), and fail to take into account the existing legal and administrative constraints on groundwater extraction in the Middle Rio Grande Basin, starting with the Rio Grande Compact. Dr. Williams acknowledges that he did not evaluate the hydrology of the entire Middle Rio Grande Basin aquifer in developing his opinions, and has explained that he “assumed that the safe yield of the South Valley area is equivalent to the total amount of recharge to the model area which includes boundary flows and river recharge, less the evapotranspiration and drain outflow,” yielding an “average safe yield from 1992 to 2005 for the South Valley area of 19,200 acre-ft/year.” Even treating his model area in isolation, however, Defendants submit that Dr. Williams’ estimated “lost safe yield” fails to take into account the volume of ongoing extraction through wells within or impacting his South Valley model area: Q And this summary of the Geoscience model water budget shows that within the area of your model, which includes the South Valley, total pumpage currently exceeds the safe yield for that area. A No, I don’t agree with that. Q It shows that safe yield is 19,152 acre-feet a year; is that correct, Doctor? A That’s right. Q And what is the total pumpage from that area? A The total pumpage I think is around 20,000, if I remember. (Tr. 12/9/2003, at 2584:16-2585:3 (testimony of Dr. Williams).) On cross-examination at the evidentiary hearing, Dr. Williams acknowledged that volume of Middle Rio Grande Basin groundwater is already being diminished by pumping to serve existing uses, primarily by the City of Albuquerque: Q Do you know what the total pum-page is for the Middle Rio Grande Basin? A I don’t. I know the total pumping for the City of Albuquerque is over 100,-000 acre-feet a year. Q And do you agree that the City of Albuquerque and other water rights holders’ pumpage from the Middle Rio Grande Basin is mining the Middle Rio Grande Basin? A I know that from the most recent report of the City of Albuquerque, there has been a change in storage and the groundwater levels.... [T]he water levels are going down maybe from one to three feet per year.... [W]e also know that there is a future plan to replenish this area of the Albuquerque — by bringing in San Juan-Chama water, 47,000, treating part of the Rio Grande, bringing in water for artificial recharge. Q ... Do you understand that the total pumpage from the Middle Rio Grande Basin annually now is decreasing the water table in that basin? A There has been a slight decline and we took that into account in our model. But even again, this is what I term temporary surplus. (Tr. 12/9/2003, at 2582:10-2583:15 (testimony of Dr. Williams).) Dr. Williams’ testimony suggests that existing “extractive services” account for all of his estimated “safe yield,” and more, thus reducing the water level in the Middle Rio Grande Basin aquifer by one or more feet per year. Concerning any additional “safe yield” at South Valley purportedly lost due to contamination, it appears that Dr. Williams and Mr. Johnson (relying on Williams) are labeling as “lost safe yield” a quantity of groundwater that Williams characterized as “temporary surplus”: Q Let’s talk about it this way. Is it recognized from a hydrogeologic standpoint that you can pump more out of an aquifer without causing, for instance, subsidence problems, over and above safe yield? A That’s correct. We have a term that’s called temporary surplus. For example, if we’re in a period of drought, like we are in California, we can pull our water levels down. We can rely on the storage to help meet our demands. But we also then have to eventually allow the aquifer to recover or replenish. We do that by several ways. We can bring in alternative water, allow the pumps not to pump so much. We can bring in artificial recharge to replenish it. So this temporary surplus is a term that — it is part of the best management practices, which does allow us to pull water levels down below, and for example, there have been studies shown in New Mexico that you can deplete — you can pull down as much as 400 feet without causing any subsidence. Q 400 feet of what? A 400 feet of water level. Q And that’s what I want to make sure. You know, you have talked a little bit about safe yield, that is, where pumping out equals pumping in, or recharge equals— A Inflow, look at the bottom of the equation. Inflow is outflow over change in storage. If I need more outflow, I can pull on my change in storage. I can allow — I can pump some brown water from storage to help meet that demand. (Tr. 12/9/2003, at 2515:13-2516:19 (emphasis added).) Counsel in turn labels Williams’ “temporary surplus” as “working reserve”: Q All right. So you could have a safe yield, which is basically an equalization of what’s going in and what’s coming out. You can have a working reserve that is where you can actually extract more in a given year or series of years for whatever the purposes you need it for drinking water? A That’s right. Q Maybe it’s drought? A Well, or also maybe its pulling the water levels down, like we do a lot in anticipation of large-scale artificial recharge programs.... Q The concept of being able to take more than just the safe yield — is that also recognized in hydrogeology as a scientific principle that is applied day in, day out? A Yes. It’s a best management practice, but keep in mind you have to eventually have programs for recharging or allowing the water levels to recover. You can’t just keep draining the aquifer. (Id. at 2517:9-2518:12 (emphasis added).) Dr. Williams’ testimony lends support to Plaintiffs’ view that there exists a volume of in situ groundwater in the Middle Rio Grande Basin aquifer that would be available for future extraction as “working reserve,” “drought reserve,” or “temporary surplus” — however Plaintiffs may choose to label it — and that the future use of at least a portion of that “temporary surplus” volume may be impaired by chemical contamination. However, the volume thus impaired does not equate with “loss of safe yield.” Okay. How we calculated the loss of safe yield? The 11,000-model acre area, which has a safe yield of about 19,000— we looked at the area, the footprint of the contaminant plume including the buffer zone, the MCL plume, and we did the ratio of the area of that water divided by the total model area times [th]is 19,000. (Id. at 2520:24-2521:5.) Calculated in this fashion, Dr. Williams’ estimate of “lost safe yield” at South Valley does not tend “to make the existence of’ a volume of unappropriated groundwater that the State could otherwise have made available for appropriation from the aquifer’s safe yield any “more probable or less probable than it would be without the evidence.” Fed.R.Evid. 401. Dr. Williams acknowledges that existing pumping from the Middle Rio Grande Basin is already drawing on what he calls “temporary surplus,” thus reducing the total volume of groundwater over time: SUMMARY OF GEOSCIENCE MODEL WATER BUDGET Yet his estimate as to “lost safe yield” does not appear to take this existing burden on the resource into account, and in fact treats part of the volume of current pumping (21,351 acre-ft/yr.) as extractive services “lost” in direct proportion to the surface area of his projected plume. Whether Dr. Williams’ estimate of the volume of. “lost safe yield” will be helpful to the trier of fact on the ultimate issue of the injury to Plaintiffs’ interests in South Valley groundwater {viz., lost “extractive services”) also depends upon legal and administrative considerations beyond the scope of Williams’ analysis. From his proffered testimony, it does not appear that Plaintiffs have asked Dr. Williams to take into consideration any restrictions on further extraction of groundwater from the Middle Rio Grande Basin aquifer resulting from the State of New Mexico’s obligations under the Rio Grande Compact. Dr. Williams testified that he had not taken legal restrictions into account: Q Now, among other things, Doctor, that you did not do is that you did not consider whether legal or administrative constraints limit or prohibit the use of allegedly lost groundwater, regardless of the level of contamination. A I didn’t look at that, no. Q So for example, you didn’t consider the existence of any restrictions that would otherwise prevent or limit the pumping of the allegedly lost groundwater in the South Valley. A You mean legal or otherwise? I did not look at that, no. Q ... In other words, it makes no difference to you that the water w