The opinion of the court was delivered by: Signed by Royce C. Lamberth, Chief Judge,
This action is brought by plaintiffs Anacostia Riverkeeper, Inc. and Friends of the Earth, Inc., two DC-based non-profit corporations, to challenge defendant Environmental Protection Agency's ("EPA" or the "Agency") approval of a pollution control plan for the Anacostia River jointly submitted by the District of Columbia and Maryland in accordance with the Federal Water Pollution Control Amendments of 1972, commonly known as the Clean Water Act ("CWA" or the "Act"), 33 U.S.C. § 1251 et seq. Under the CWA, a State (including the District) is obligated to develop water quality standards for each navigable water body within its jurisdiction. These standards generally consist of expected uses of the water body and criteria defining the maximum level of pollution allowable to protect such uses. The CWA requires each State to monitor its waters for compliance with such standards following the implementation of technology-based pollution controls under separate provisions of the Act. A determination that a particular water body is not meeting applicable standards triggers a State's obligation to develop and submit for EPA approval total maximum daily loads ("TMDLs") for the pollutants in that water body. Relying on limits set by these TMDLs, federal permit programs, along with state and local actors, implement water-pollution controls to achieve contamination levels necessary to attain and maintain water quality standards. This suit involves a challenge to a TMDL for the Anacostia River developed by the District and Maryland and approved by EPA in 2007.
The Anacostia River is, in a word, dirty. Its waters are frequently turbid, resulting in an opaque and muddy appearance. This condition results from an excess of sediments and total suspended solids ("TSS") in the river. The polluted state of the Anacostia render it unfit for the uses that the District and Maryland have designated the watershed to support, including contact recreation (e.g., swimming), secondary contact recreation (e.g., boating), and the protection and propagation of plant and animal life. The sullied state of today's Anacostia is no surprise: Despite the existence of similarly turbid conditions since the inception of the CWA, neither the District nor the Agency lifted a finger to address any concerns, whether related to excess sediments and TSS or other contaminants, for nearly two decades-in contravention of statutory obligations to act as early as 1979. In plain disregard of its duties as set forth in the Act, the District did not begin to own up to its responsibilities under the CWA until being compelled by a district court ruling. Kingman Park Civil Ass'n v. EPA, 84 F. Supp. 2d 1 (D.D.C. 1999). And a few years later, the first attempt by the District and EPA to develop a sediment/TSS TMDL for the Anacostia was invalidated by the D.C. Circuit as contrary to the plain text of the CWA. Friends of the Earth, Inc. v. EPA, 446 F.3d 140 (D.C. Cir. 2006) ("Friends II"). After this ruling, EPA coordinated a joint effort between the District and Maryland to develop a single TMDL for both jurisdictions to address excessive sediment and TSS pollution in the Anacostia River. The resulting sediment/TSS TMDL, which was submitted to EPA in June 2007 and approved one month later, is the subject of this suit.
The Clean Water Act "is a comprehensive water quality statute designed to 'restore and maintain the chemical, physical, and biological integrity of the Nation's waters.'" PUD No. 1 of Jefferson Cty. v. Wash. Dep't of Ecology, 511 U.S. 700, 704 (1994) (quoting 33 U.S.C. § 1251(a)). A core element of the CWA is its two-step approach to improving water quality, which delegates certain responsibilities to EPA and others to the States in furtherance of the Act's stated purpose of promoting cooperation between federal and state governments. 33 U.S.C. § 1251(b).*fn1 The first step requires EPA, "among other things, to establish and enforce technology-based limitations on individual discharges into the country's navigable waters from point sources." PUD No. 1, 511 U.S. at 704 (citing 33 U.S.C. §§ 1311 & 1314). A point source is "any discernable, confined and discrete conveyance . . . from which pollutants are or may be discharged," 33 U.S.C. § 1362(14), such as an industrial pipe or sewage drain. Am. Paper Institute, Inc. v. EPA, 996 F.2d 346, 348--49 (D.C. Cir. 1993). Because point sources are identifiable locations where pollutants enter a water body, they constitute ideal starting points for the monitoring and regulation of water contamination. Section 301 of the CWA directs EPA to develop effluent limitations that cap the maximum allowable discharge at each individual point source. 33 U.S.C. § 1311(b)(1). Such restrictions incorporate "the best available technology economically achievable for a particular class of waters," id. at § 1311(b)(2), and evolve over time with the growth of technological means to limit contamination. Once promulgated, the effluent limitations are incorporated into the National Pollutant Discharge Elimination System ("NPDES"). The NPDES is a permit program through which individual entities responsible for covered point sources receive permits setting the maximum discharges of particular contaminants via these sources. See generally id; see also Sierra Club v. Meiburg, 296 F.3d 1021, 1024 (11th Cir. 2002) ("The statute gives EPA the authority to issue permits for point sources, and those permits are to establish technology-based effluent limitations that incorporate increasingly stringent levels of pollution control technology over time.").
Point sources, however, are not the only manner in which pollutants enter a water system. Sediments and other biological materials can easily accumulate in rivers through normal ecological processes, such as drainage from wooded areas or erosion of the river bank. Many toxins are also capable of entering water systems through run-off from agricultural land. And overflows from insufficiently drained urban areas-particularly during extreme weather-often lead to a massive influx of sediments, TSS and other pollutants. To capture these and similar effects-all of which are difficult to monitor or regulate-the CWA aggregates large-scale sources of water contamination into categories of "non-point source" pollution. At the most general level, non-point source pollution is the entry of contaminants into the water body by any means other than a discrete point source.
Non-point source pollution is often so extensive that it continues to impair water bodies even after technology-based effluent limitations have been fully implemented. But "[u]nlike point source pollution, EPA lacks the authority to control non-point source discharges through a permitting process." Defenders of Wildlife v. EPA, 415 F.3d 1121, 1124 (10th Cir. 2005). To address water quality concerns that linger after implementation of effluent limitations, the CWA's second step in its approach to water cleanup requires each State to develop water quality standards for interstate waters within its borders. Id. In keeping with the interactive process envisioned in the CWA, a State must submit these standards to EPA for review and approval. Meiburg, 296 F.3d at 1025. Under EPA regulations, these submissions must contain (1) designated uses for the water body, (2) information concerning the methodology for choosing these uses, (3) water quality criteria sufficient to protect the designated uses, (4) an antidegradation policy to prevent clean waters from slipping below applicable standards, (5) a certification that the water quality standards were properly adopted in a manner consistent with state law and (6) general information useful in aiding the Agency's review. 40 C.F.R. § 131.6(a)--(f). The "designated uses of the navigable waters involved and the water quality criteria for such waters" are the heart of these water quality standards. 33 U.S.C. § 1313(c)(2)(A); see also 40 C.F.R. § 130.2(d) (defining water quality standard as "a designated use or uses for the waters . . . and water quality criteria for such waters").
A designated use is exactly as it sounds: after considering "the use and value of water for public water supplies, protection and propagation of fish, shellfish and wildlife, recreation in and on the water, agricultural, industrial, and other purposes including navigation," 40 C.F.R. § 131.10(a), a State must catalogue the manner in which each of its covered waters are to be utilized by governments, persons, animals and plants.*fn2 Examples of designated uses include drinking or reservoir purposes, primary (e.g., swimming) or secondary (e.g., boating) recreation, and the preservation and support of plant and animal life. Id. § 131.3(f).
Water quality criteria, on the other hand, are measures of the conditions of a water body and "come in two varieties: specific numerical limitations on the concentration of a specific pollutant in the water . . . or more general narrative statements applicable to a wide set of pollutants." Am. Paper, 996 F.2d at 349. Numeric criteria articulate specific, measurable quantities of pollutants that can be readily monitored, while narrative criteria are general descriptions of water quality, such as "free from visible waste" or "sufficient clarity for aesthetic purposes." Whether numeric or narrative, the key aspect of water quality criteria is that they are dependent upon designated uses associated with them; as EPA regulations explain: "States must adopt those water quality criteria that protect the designated use." 40 C.F.R. § 131.11(a).
After promulgating water quality standards, States are responsible for monitoring their covered waters and, when necessary, identifying those waters for which current pollution controls "are not stringent enough to implement any water quality standard applicable to such waters." 33 U.S.C. § 1313(d)(1)(A). Every two years, a State must submit to EPA a list of waters that do not currently attain, and based on current pollution controls are not expected to attain, applicable water quality standards. 40 C.F.R. § 130.7(b)(3) & (d). Under governing regulations, this submission-known as a "303(d) list"-contains all waters for which (1) technology-based effluent limitations, (2) more stringent effluent limitations imposed by State or local authority, and (3) other pollution controls required by State law are "not stringent enough to implement any water quality standards applicable to such waters." Id. § 130.7(b)(1).
The inclusion of a water body on a State's 303(d) list triggers a statutory obligation to develop total maximum daily loads, or TMDLs, which specify the absolute amount of particular pollutants the entire water body can take on while still satisfying all water quality standards. 33 U.S.C. § 1313(d)(1)(C). As EPA explains: "A TMDL sets the quantity of a pollutant that may be introduced into a water body without causing an exceedance [sic] of the applicable water quality standard." EPA Decision Rationale: Total Maximum Daily Loads for Anacostia River Basin Watershed 1, July 24, 2007, Ex. 2 to EPA Cross-Mtn., Sep. 18, 2009 [27-2] ("DR"). States submit proposed TMDLs to EPA for review, at which time the Agency can either approve or reject such proposals. 33 U.S.C. § 1313(d)(2). Rejection of a submitted TMDL triggers EPA's duty to develop a substitute TMDL for the water body in question. Id.
In addition to setting a maximum daily level of pollution, EPA regulations require TMDLs to allocate contaminant loads among point and non-point sources of pollution. Point source pollution is then further subdivided into wasteload allocations ("WLAs"), which are the portions of the water body's pollutant discharges "allocated [under the TMDL] to one of its existing or future point sources of pollution." 40 C.F.R. § 130.2(h). Similarly, the total predicted non-point source pollution is separated into load allocations ("LAs"), which are the portions of a water body's contaminant inflow "attributed either to one of its existing or future non-point sources of pollution or to natural background sources." Id. § 130.2(g). Along with a statutorily-mandated margin of error, the total TMDL is thus the "sum of individual WLAs for point sources and LAs for non-point sources and natural background." Id. § 130.2(i); see also DR at 1 ("EPA's regulations define a TMDL as the sum of [WLAs] assigned to point sources, the [LAs] assigned to non-point sources, and natural background, and a margin of safety.").
TMDLs are not self-implementing instruments, but instead serve as informational tools utilized by EPA and the States to coordinate necessary responses to excessive pollution in order to meet applicable water quality standards. Pronsolino v. Nastri, 291 F.3d 1123, 1129 (9th Cir. 2002). "TMDLs are central to the Clean Water Act's water-quality scheme because . . . they tie together point source and non-point source pollution issues in a manner that addresses the whole health of the water." Meiburg, 296 F.3d at 1025. On the federal side, the LAs and WLAs that make-up the TMDL are incorporated into the NPDES system through permit-based regulation of point sources. See EPA, Water Quality Planning and Management, 50 Fed. Reg. 1774, 1774 (Jan. 11, 1985) ("Once a TMDL has been completed, a wasteload allocation or load allocation (WLA/LA) for that TMDL forms the basis for permit limitations for individual dischargers."). Incorporated in this manner, WLAs provide a "supplementary basis [for permit limits] so that numerous point sources, despite individual compliance with effluent limitations, may be further regulated to prevent water quality from falling below acceptable levels." Raymond Proffit Found. v. EPA, 930 F. Supp. 1088, 1090 (E.D. Pa. 1996). This process also ensures that the flows of contaminants from point sources are adjusted to account for non-point source pollution, which is inherently more difficult to monitor, control, or reduce. Am. Littoral Soc'y v. EPA, 199 F. Supp. 2d 217, 229 (D.N.J. 2002). On the state side, the maximum levels and allocations of pollutants in a TMDL are incorporated into the State's water quality management plan. EDF v. Costle, 657 F.3d 275, 294 (D.C. Cir. 1981); see also Am. Littoral Soc'y, 199 F. Supp. 2d at 229 ("Any EPA-approved TMDLs must be incorporated by the State into its continuing planning processes."). Through these plans, States coordinate among agencies, local authorities, and non-governmental organizations to further reduce both point and non-point source pollution. In sum, a TMDL provides crucial information for federal, state and local actors in furtherance of the cooperative efforts to improve water quality envisioned in the CWA.
B. Factual and Procedural History
1. Applicable Water Quality Standards
Both the District and Maryland have promulgated water quality standards under the CWA applicable to sediment and TSS pollution in the Anacostia River. Maryland, for its part, designates its sections of the Anacostia as suitable for Uses I-P and II, which include "water contact recreation" and "support of estuarine and marine aquatic life." MD. CODE REGS. 26.08.02.08(O)(1)--(2) & 26.08.02.03-3(B)--(C). To achieve and protect these uses, Maryland provides both numeric and narrative water quality criteria applicable to sediment and TSS pollution. These metrics include numeric criteria of 50 Nephelometer Turbidity Units ("NTUs") monthly average and seasonal Secchi depths of .4 meters, id. at 26.08.02.03-3(A)(5)(b) & (B)(1) & (C)(9)(b),*fn3 as well as a narrative criterion that turbidity resulting from excessive sediment and TSS pollution must "not exceed levels detrimental to aquatic life." Id. The District, for its part, designates its sections of the Anacostia for Class A, B, C, D, and E uses, which include, inter alia, contact and secondary contact recreation, aesthetic enjoyment, and protection of plant and animal life. D.C. MUN. REGS. tit. 21 § 1101.2. The District has also promulgated both narrative and numeric criteria in order to achieve and maintain these designated uses. Included among its narrative criteria are requirements to keep the Anacostia free from "objectionable odor, color, taste, or turbidity," maintain the watershed's "aesthetic qualities," and ensure that it can "support aquatic life." Id. §§ 1104.1(c) & 1104.4. As for its numeric criterion, the District lists 20 NTUs and .8 meters Secchi depth as necessary to meet its water quality goals. Id. § 1104.8.
2. Prior Attempts to Develop a Sediment/TSS TMDL for the Anacostia
The development of a sediment/TSS TMDL is a story of excessive negligence and unnecessary delay. Though at its inception the CWA obligated each State to begin submitting 303(d) lists and developing TMDLs by June 28, 1979, 33 U.S.C. § 1314(a)(2)(D), the District did nothing before that deadline-or for the 18 years that followed. Kingman Park, 84 F. Supp. 2d at 2. Eventually, a number of organizations joined to bring what has come to be known as a "constructive submission" suit. The theory underpinning such a suit is that a State's inaction in the face of its obligations under the CWA constitutes the legal equivalent of a "submission" of a 303(d) list that includes no waters and requires no TMDLs. Id. at 4--5. Treating a State's silence in this manner is critical because a submission to EPA triggers its responsibility to review that proposal and-if it disagrees with the State's conclusions-list appropriate waters and develop TMDLs for those waters. Where successful, these suits have become critical tools for organizations and interest groups to prompt action under the CWA.
As had many courts before it, the district court adopted the constructive submission theory over EPA's objection. See id. at 5 ("Like the majority of courts that have confronted this quandary, this Court holds that if a State fails over a long period of time to submit proposed TMDLs, this prolonged failure may amount to 'constructive submission' by that State of no TMDLs.") (quotations omitted; collecting cases). Emphasizing the District's "silence and intransigence" in the face "of its Section 303(d) obligations," the Kingman Park Court held that "[w]here a State has made a decision that would otherwise trigger EPA review, the State may not evade such review by simply refusing to reduce its decision to a formal submission." Id. at 6. Consistent with this holding, the court denied EPA's motion to dismiss.
In the wake of the Kingman Park decision, EPA, the District and the plaintiffs entered into a consent decree under which the District agreed to regularly submit 303(d) lists to EPA and begin developing TMDLs for its waters. The Anacostia River was included on the initial 303(d) list, and in 2002 the District submitted and EPA approved a TMDL to address excess sediment and TSS pollution in the Anacostia that relied upon annual, rather than daily, load limits, Friends of the Earth v. EPA, 346 F. Supp. 2d 182 (D.D.C. 2004) ("Friends I")-despite the CWA's instruction to develop a "total maximum daily load." 33 U.S.C. § 1313(d)(1)(C) (emphasis added). The same plaintiffs before the Court in this case subsequently brought a challenge under the CWA and APA raising several concerns with that TMDL-including the use of maximum annual loads. In a 2004 opinion, Judge Urbina rejected plaintiffs' challenges and upheld EPA's approval of the proposed TMDL. See generally Friends I, 346 F. Supp. 2d at 188--203 (granting summary judgment for EPA). On appeal, the D.C. Circuit reversed the Friends I decision, focusing solely on the question of whether a TMDL can be expressed in annual, rather than daily, limits. Friends II, 446 F.3d at 143--44. The D.C. Circuit rejected the district court's deference to EPA's own interpretation, concluding that the statutory language unambiguously commands the development of TMDLs expressed in daily load limits. See id. at 144 ("Nothing in this language even hints at the possibility that EPA can approve total maximum 'seasonal' or 'annual' loads."). Without addressing any other issues on appeal, the Friends II Court remanded the action "to the district court with instructions to vacate EPA's approvals." Id. at 148.
3. Development of the Current Sediment/TSS TMDL
On remand, the district court stayed the vacateur at the request of all parties while the Agency and the District developed a new sediment/TSS TMDL. DR at 10. Recognizing that the Anacostia is a multistate water body and that efforts to reduce pollution in the river necessarily require coordination between multiple jurisdictions, EPA brought the District and Maryland together to collaborate on a new, system-wide sediment/TSS TMDL for the river. See id. An advisory group made up of representatives from the District, Maryland, EPA and the Washington Area Sewer Authority ("WASA") developed models for certain aspects of the Anacostia and used these analyses to create a sediment/TSS TMDL for the watershed. A draft TMDL was then published and made subject to public comment from April 6, 2007 to May 7, 2007. Id. at 33.
Plaintiffs, through counsel Earthjustice, submitted a series of comments in response to the draft TMDL. See Earthjustice Comments to Maryland and the District of Columbia Draft Total Maximum Daily Loads for the Anacostia River Basin, May 7, 2007, Ex. 6 to EPA Cross-Mtn., Sep. 18, 2009 [27-6] ("Earthjustice Comments"). Plaintiffs' comments raised several general concerns, including that the draft TMDL failed to (1) implement all applicable water quality standards, (2) provide an adequate margin of safety under the CWA, (3) include properly subdivided wasteload allocations, and (4) provide assurance of proper implementation. See generally id. The District and Maryland subsequently submitted a joint response to objections raised by both plaintiffs and other commentators. See DC & Maryland Comment Response Document Regarding the TMDL of TSS in the Anacostia River Watershed, June 21, 2007, Ex. 3 to EPA Cross-Mtn., Sep. 18, 2009 [27-3] ("DC/MD Cmt. Response").
One day later, the District and Maryland submitted their proposed TMDL to EPA for review. See Final Total Maximum Daily Load of TSS for the Anacostia River Basin, June 22, 2007, Ex. 1 to EPA Cross-Mtn., Sep. 18, 2009 [27-1] ("Final TMDL"). The Final TMDL's stated objectives are to ensure (1) that "aquatic life is protected in the tidal and non-tidal waters of the Anacostia," (2) that "MD's and DC's sediment-related water quality standards that support aquatic life are met in their respective portions of the watershed," and (3) "in particular that the numeric criteria for water quality are met in the tidal waters." Id. at vi. Consistent with these goals, the Final TMDL focuses almost exclusively on determining pollutant load limits for the protection of submerged aquatic vegetation ("SAV") and other plant and animal life. To this end, the Final TMDL lists only those designated uses and water quality criteria related to aquatic life. Id. at 21--23. Similarly, though the Final TMDL concludes that the relevant "endpoint of the TMDL (the most stringent reduction in sediment loads) is DC's tidal Anacostia clarity criterion," id. at 24, it does not evaluate whether that criterion is more stringent than criteria tied to recreational or aesthetic uses of the Anacostia under the District or Maryland law. To evaluate its proposed reductions in sediment and TSS pollution, the Final TMDL employs a series of models to predict, inter alia, non-point source pollution entering the Anacostia, the hydrological and sediment erosion along the water body, the sediment loads required to meet water quality standards in the river, and flows and clarity conditions in the river basin. See generally id. at vi--vii. Using data collected between 1995 and 1997, the Final TMDL relies on these models to conclude that annual reductions in sediments and TSS to 7097.6 tons/year and 3396.1 tons/growing season (defined as the period from April 1 to October 31) are necessary for the protection of aquatic life in the Anacostia. Id. at vii. These totals are then broken down into daily maximum loads distributed among three sources: WLAs for point sources and municipal separate storm sewer systems ("MS4s"),*fn4 LAs for forests and other underdeveloped lands, and an implicit margin of safety incorporated into the Final TMDL's modeling process. Id. at vii--xi. Together, the total proposed reduction represents an approximately 85% decline in the amount of sediment and TSS pollution in the Anacostia. Id. at vii. The Final TMDL then summarizes the process for incorporating the maximum loads into NPDES permits, state regulations, and plans for state and local agencies and organizations, id. at xiv--xv, and closes by explaining that "the required reductions [are] to be implemented in an iterative process." Id. at xv.
A month after the District and Maryland submitted the Final TMDL for review, EPA issued a written Decision Rationale approving the terms of the proposal. The summary of EPA's decision echoes the three purposes articulated in the Final TMDL-to ensure protection of aquatic life, meet water quality standards related to aquatic life, and meet water quality criteria- and indicates that the numeric target for the proposal is .8 meters Secchi depth, which is the District's water quality criterion for Class C uses. DR at i. The Decision Rationale also notes that EPA concurs with Maryland and the District that the proposed load levels will lead to an 85% reduction in sediment and TSS pollution in the Anacostia, id. at ii, and sets forth seven regulatory conclusions. See id. at ix (finding that Final TMDL (1) is "designed to implement the applicable water quality standards," (2) includes "a total allowable load as well as individual [WLAs] and [LAs]," (3) considers "the impacts of background pollutant contributions, (4) accounts for "critical environmental conditions," (5) evaluates "seasonal environmental variations," (6) includes "a margin of safety," and (7) was "subject to public participation").*fn5
Few changes were made to the proposed TMDL after public comment, and plaintiffs- believing that the Final TMDL fails to account for the alleged shortcomings raised in their comments to the draft TMDL-filed this suit in early 2009 to contest the validity of EPA's approval. Complaint, Jan. 15, 2009 .*fn6 Plaintiffs' action is brought under the CWA and the Administrative Procedure Act ("APA"), which prohibits agency action that is "arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law." 5 U.S.C. § 706(2)(A). The Complaint identifies five purported deficiencies that, according to plaintiffs, render EPA's approval of the Final TMDL arbitrary and capricious: (1) failure to set load limits on sediment and TSS pollution sufficient "to implement the District's and Maryland's applicable water quality standards"; (2) reliance on water quality criteria that will not "provide for attainment" of all relevant narrative and numeric water quality criteria; (3) failure "to take into account critical conditions . . . to protect water quality during high flow events"; (4) improper allocation of pollutant loads "to individual point sources"; and (5) omission of "an adequate margin of safety that takes into account any lack of knowledge." Compl. at ¶ 26(a)--(e). Based on these alleged shortcomings, plaintiffs ask the Court to vacate EPA's approval of the Final TMDL and direct the Agency to develop a new sediment/TSS TMDL for the Anacostia, retain jurisdiction to ensure compliance with such an order, and award costs and fees. Id. at 11--12.
A few months after this suit was filed, WASA- the District's sewer authority and an advisory group participant-moved to intervene as a matter of right or through permissive intervention. Motion to Intervene, Apr. 13, 2009 . Plaintiffs consented, Response to Motion to Intervene, Apr. 22, 2009 , and the Court granted permissive intervention under Federal Rule of Civil Procedure 24(b). Order, Apr. 28, 2009 . Less than two months later, a group of local water authorities (the "Municipal Intervenors")*fn7 requested intervention as well. Motion to Intervene, June 8, 2009 . Plaintiffs again consented, Response to Motion to Intervene, June 19, 2009 , and the Court granted the motion. Minute Order, Aug. 6, 2009.
Plaintiffs subsequently moved for summary judgment. Plaintiffs' Motion for Summary Judgment, July 17, 2009  (Ps' Mtn."). In their motion, plaintiffs advance three theories as to why EPA's approval of the Final TMDL is in violation of the CWA: first, for a variety of reasons, the Final TMDL sets load levels that will not achieve water quality standards applicable to sediment and TSS pollution in the Anacostia River under Maryland and DC law, id. at 9--17; second, the Final TMDL improperly assigns WLAs on a system-wide basis for the MS4s along the watershed, id. at 17--20; and third, the margin of safety incorporated into the Final TMDL is factually unverifiable and thus legally insufficient. Id. at 20--22. EPA subsequently cross-moved for summary judgment, arguing that its decision-making was supported by a reasonable review of the evidence, EPA's Cross-Motion for Summary Judgment 14--21, Sep. 18, 2009  ("EPA Cross-Mtn."), that plaintiffs' concerns are unfounded and impose requirements outside the text of the CWA, id. at 21--26, that system-wide WLAs for MS4s are appropriate under applicable law, id. at 26--30, and that the margin of safety implicit in the models used to develop the Final TMDL is sufficient. Id. at 30--34. At the same time, both WASA and the Municipal Intervenors cross-moved for judgment on behalf of EPA. While both cross-motions parrot positions set forth by EPA, each also advances its own argument, both discussed in greater detail below, concerning what water quality standards are applicable in this context. WASA's Cross-Motion for Summary Judgment 12--17, Sep. 18, 2009  ("WASA Cross-Mtn"); Municipal Intervenors' Cross-Motion for Summary Judgment 5--10, Sep. 18, 2009  ("Municipal Cross-Mtn."). The parties concluded subsequent briefing on all the issues by November 2009.*fn8 Having reviewed the parties' briefings, the record, and applicable law, the Court, for the reasons set forth below, rejects the majority of plaintiffs' challenges but also holds that EPA's finding that the Final TMDL will attain applicable water quality standards is insufficient under the law and unsupported by the evidence, and thus the Agency's approval of the Final TMDL is arbitrary and capricious. The Court therefore grants in part plaintiffs' motion for summary judgment, and will vacate EPA's approval of the Final TMDL.
Summary judgment is properly granted where there is "no genuine issue of material fact." Anderson v. Liberty Lobby, Inc., 477 U.S. 242, 247--48 (1986). Here, the facts consist of the record relied upon by EPA to approve the Final TMDL, and the parties do not dispute any of the relevant matters in that record. Accordingly, review of EPA's action is subject only to the APA's command that the Court "review the whole record or those parts of it cited by a party," 5 U.S.C. § 706, and the related requirement to evaluate that record as it was when EPA published its Decision Rationale. Citizens to Preserve Overton Park, Inc. v. Volpe, 401 U.S. 402, 420 (1971), overruled on other grounds by Califano v. Sanders, 430 U.S. 99, 105 (1977).
A. Review of Agency Action
EPA's approval of the Final TMDL is an act taken pursuant to the CWA and thus is subject to challenge under the APA and the "indulgent" standards applicable to such review. Chem. Mfrs. Ass'n v. EPA, 28 F.3d 1259, 1263 (D.C. Cir. 1994). The APA requires that a reviewing court "hold unlawful and set aside agency action, findings and conclusions found to be arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law." 5 U.S.C. § 706(2)(A); see also Motor Veh. Mfrs. Ass'n v. State Farm Mutual Auto. Ins. Co., 463 U.S. 29, 41 (1983). This standard is narrow and does not permit a court to substitute its policy judgment for that of the agency. Bluewater Network v. EPA, 370 F.3d 1, 11 (D.C. Cir. 2004). Indeed, the principal concern on review is solely whether "EPA has 'examined the relevant data and articulated a satisfactory explanation for its action including a rational connection between the facts found and the choice made.'" Id. (quoting Motor Veh. Mfrs., 463 U.S. at 43). Even an agency "decision of less than ideal clarity" should be upheld "if the agency's path may be reasonably discerned." Motor Veh. Mfrs., 463 U.S. at 43 (quotations omitted). At the same time, it is "an axiom of administrative law that an agency's explanation of the basis for its decision must include a rational connection between the facts found and the choice made." Bowen v. Am. Hosp. Ass'n, 476 U.S. 610, 626 (1986). A court will therefore "not supply a reasoned basis for the agency's action that the agency itself has not given." Bowman Trans., Inc. v. Arkansas-Best Freight Sys., Inc., 419 U.S. 281, 285--86 (1974); see also Friends I, 346 F. Supp. 2d at 196 ("Courts frown on post-hoc rationalizations of discretionary agency behavior because such rationalizations prevent proper judicial review.") (citations omitted).
With respect to interpretation of the CWA, courts apply the familiar Chevron framework. First, a court looks to the statutory language to determine whether Congress's intent is clear. "If the intent of Congress is clear, that is the end of the matter; for the court, as well as the Agency, must give effect to the unambiguously expressed intent of Congress." Bluewater Network, 370 F.3d at 11. If the language of the statute is ambiguous, however, a court will instead "look first to the agency regulations, which are entitled to deference if they resolve the ambiguity in a reasonable manner." Couer Alaska Inc. v. Se. Alaska Conservation Council, 129 S. Ct. 2458, 2469 (2009). And where those regulations are ambiguous, a court should "next turn to the [agency's] subsequent interpretation of those regulations," id. at 2469, which is given "controlling weight unless it is plainly erroneous or inconsistent with the regulation." Bowles v. Seminole Rock & Sand Co., 325 U.S. 410, 414 (1945).
B. Effect of the Friends I Decision
A secondary issue concerning the appropriate legal standard is the extent to which the Court is bound or should otherwise be persuaded by prior rulings on similar issues in Friends I. This is particularly important here, as a number of disputes in this case closely mirror objections raised by these same plaintiffs before Judge Urbina. See, e.g., Friends I, 346 F. Supp. 2d at 200-- 01 (concluding that proposed sediment reductions were sufficient to protect all designated uses under DC law); id. at 201 (upholding permissible daily variations in maximum inflow of pollutants); id. at 201--02 (finding that reliance on numerical criteria satisfied narrative water quality criteria); id. at 203 (affirming EPA's decision to permit WLAs on jurisdiction-wide basis for MS4s). In this case, the Court concludes that it need not give more or less weight to the decision in Friends I than it would to any other opinion by another court in this district. EPA correctly points out that the Friends II opinion did not reverse Judge Urbina's conclusions in Friends I on questions relevant here, and thus that opinion remains a statement of law with respect to those issues. Action Alliance of Senior Citizens v. Sullivan, 930 F.2d 77, 83 (D.C. Cir. 1991). While technically correct, this is not an instance-as is often the case-where the Circuit Court upheld a number of the lower court's rulings and reversed others. Here the D.C. Circuit discussed only the necessity of daily load limits under the CWA, and thus Friends II can be read as neither a confirmation nor rejection-tacit or ...