Full opinion text
MEMORANDUM OPINION ROYCE C. LAMBERTH, Chief Judge. I. INTRODUCTION 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 Civic 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. II. BACKGROUND A. Statutory Framework 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, 114 S.Ct. 1900, 128 L.Ed.2d 716 (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). 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, 114 S.Ct. 1900 (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. 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 NPDÉS 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 dis-chargers.”). 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 Proffitt 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.2d 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 nongovernmental 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(0)(l)-(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), 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 Sec-chi 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 “[wjhere 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 TMBL On remand, the district court stayed the vacateur at the request of all parties while the Agency and the District developed a new sedimenf/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”), 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],” (8) 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”). 4. This Litigation New 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 [l]. 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 [8]. Plaintiffs consented, Response to Motion to Intervene, Apr. 22, 2009 [9], and the Court granted permissive intervention under Federal Rule of Civil Procedure 24(b). Order, Apr. 28, 2009 [14]. Less than two months later, a group of local water authorities (the “Municipal Intervenors”) requested intervention as well. Motion to Intervene, June 8, 2009 [16]. Plaintiffs again consented, Response to Motion to Intervene, June 19, 2009 [19], 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 [21] (“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 [27] (“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 [28] (“WASA Cross-Mtn”); Municipal Intervenors’ Cross-Motion for Summary Judgment 5-10, Sep. 18, 2009 [29] (“Municipal CrossMtn.”). The parties concluded subsequent briefing on all the issues by November 2009. 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. III. STANDARD 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, 106 S.Ct. 2505, 91 L.Ed.2d 202 (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, 91 S.Ct. 814, 28 L.Ed.2d 136 (1971), overruled on other grounds by Califano v. Sanders, 430 U.S. 99, 105, 97 S.Ct. 980, 51 L.Ed.2d 192 (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, 103 S.Ct. 2856, 77 L.Ed.2d 443 (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, 103 S.Ct. 2856). 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, 103 S.Ct. 2856 (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, 106 S.Ct. 2101, 90 L.Ed.2d 584 (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, 95 S.Ct. 438, 42 L.Ed.2d 447 (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.” Coeur Alaska Inc. v. Se. Alaska Conservation Council, 557 U.S. 261, 129 S.Ct. 2458, 2469, 174 L.Ed.2d 193 (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, 65 S.Ct. 1215, 89 L.Ed. 1700 (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 express — of the lower court’s conclusions on other issues before it. Judge Urbina’s opinion, just as that of any other district court, is not binding on this Court. J.S. v. Dist. of Columbia, 533 F.Supp.2d 160, 162 n. 3 (D.D.C.2008). Accordingly, while the Court will consider the decisions reached in Friends I when evaluating the issues before it, it is not bound to the conclusions reached in Friends I. IV. ANALYSIS Plaintiffs’ objections to EPA’s decision approving the Final TMDL can be broadly grouped into three categories. First, plaintiffs assert that the Final TMDL is insufficient under the CWA because it (1) does not set load limits necessary to achieve all water quality standards under DC and Maryland law, (2) improperly permits periodic violations of those standards, and (3) relies on the wrong water quality criteria. Second, plaintiffs content that the WLAs for MS4s are improperly aggregated to include a single load allocation for the entire MS4 instead of providing limits for each individual point source within that MS4. Finally, plaintiffs argue that the margin of safety adopted by the Final TMDL and approved by EPA is inadequate. The Court discusses each of these objections in turn. A. Achievement of Applicable Water Standards 1. TMDLs Must Implement All Water Quality Standards Made Applicable to a Water Body under State Law Before the Court can review EPA’s conclusion that the Final TMDL is sufficient to attain water quality standards applicable to the Anacostia, a predicate issue must be resolved: what are these standards? The CWA instructs that a TMDL must establish pollutant load restrictions “at a level necessary to implement the applicable water quality standards with seasonal variations and a margin of safety.” 33 U.S.C. § 1313(d)(1)(C) (emphasis added). And under the Act’s implementing regulations, each water quality standard “defines the water quality goals of a water body, or a portion thereof, by designating the use or uses to be made of the water and by setting criteria necessary to protect the uses.” 40 C.F.R. § 130.3; see also Nat’l Wildlife Fed’n v. Adamkus, 127 F.3d 1126, 1127 (D.C.Cir.1997) (explaining that water quality standards “include ... designated uses for each body of water, such as recreational, agricultural, or industrial uses [and] specific limits on the levels of pollutants necessary to protect those designated uses”). Reading these provisions together, then, the CWA requires a TMDL that sets load limits on a pollutant sufficient to reduce contamination to levels necessary to satisfy the narrative and numeric water quality criteria and protect all designated uses applicable to the water body. See Costle, 657 F.2d at 294 (stating that TMDLs set “the maximum amount of a pollutant which can be contributed into a stream segment without causing a violation of the water quality standards ”) (emphasis added). This understanding is also consistent with the Supreme Court’s rejection of an argument, set forth by owners of a dam that was interfering with certain uses of a water body covered by the CWA, that because the operation of the dam did not cause water quality to violate applicable criteria they were not in breach of the Act. PUD No. 1, 511 U.S. at 714, 114 S.Ct. 1900. Observing that “the language of § 303 [of the CWA] is most naturally read to require that a project be consistent with both components, namely the designated use and the water quality criteria.,” id. at 714-15, 114 S.Ct. 1900, the Supreme Court concluded that, “under the literal terms of the statute, a project that does not comply with a designated use of the water does not comply with the applicable water quality standards” — even where water quality criteria are met. Id. at 715, 114 S.Ct. 1900. In this same sense, a TMDL that is not protective of the designated uses is in violation of the requirement to establish load levels “for all .pollutants preventing or expected to prevent attainment of water quality standards.” 40 C.F.R. § 130.7(c)(1)(h). Under DC and Maryland law, the Anacostia River is designated for uses related to recreation, aesthetic enjoyment, and protection of aquatic life, and the States have promulgated water quality criteria to protect each such use. Supra Section II. B.l. The Final TMDL, however, expressly focuses on the propagation of plant and animal life and — as plaintiffs correctly observed in comments on the draft TMDL— “studiously avoids mentioning or otherwise addressing any other designated uses.” Earthjustice Comments at 3. Given this focus, the Final TMDL’s declared purpose is “to determine what reductions in suspended sediment loads to the tidal Anacostia result in water clarity improvements sufficient to support growth of SAV,” id. at 28 (emphasis added), and the modeling and analytical methods used “are designed to be protective of aquatic life in the non-tidal waters of the Anaeostia River, to meet MD’s and DC’s sediment-related [water quality standards] that support aquatic life in the tidal waters, and to meet DC’s numeric criterion for water clarity.” Id. at 26 (emphasis added). WASA and Municipal Intervenors, while joining the positions staked out by EPA in support of its approval of the Final TMDL, also raise separate arguments defending the Final TMDL’s narrow focus on aquatic life. On the one hand, WASA insists that the scope of a TMDL is dictated by the specification of use-impairments in a State’s 303(d) list. Thus, WASA argues, because the 303(d) lists submitted by the District and Maryland identify sediment and TSS pollution as detrimental only to plant and animal life, the Final TMDL is required to remedy only these effects. WASA Cross-Mtn. at 12-15. On the other hand, the Municipal Intervenors urge that under the CWA, a TMDL need not target all designated uses or water quality criteria, but may focus its attention — as the Final TMDL did — on a subset of water quality standards. Municipal Cross-Mtn. at 5-10. The Court discusses each of these arguments in turn. a. The Scope of a TMDL is Not Limited by Impairment Reports in a 303(d) List The need to develop TMDLs for a particular water body is prompted by the placement of that waterway on a State’s 303(d) list. Both the identification and creation stages of this process are governed by section 303 of the CWA, which provides, in relevant part: (A) Each State shall identify those waters within its boundaries for which the effluent limitations required by section 301(b)(1)(A) and section 301(b)(1)(B) are not stringent enough to implement any water quality standards applicable to such waters.... (C) Each state shall establish for the waters identified in paragraph (1)(A) of this subsection, and in accordance with the priority ranking, the total maximum daily load, for those pollutants which the Administrator identifies under section 1314(a)(2) of this title as suitable for such calculation. Such load shall be established at a level necessary to implement the applicable water quality standards with seasonal variations and a margin of safety which takes into account any lack of knowledge concerning the relationship between effluent limitations and water quality. 33 U.S.C. § 1313(d)(1). WASA argues that these two subsections are linked, and that subsection (l)(C)’s direction to set load limits that will protect “applicable” water quality standards restricts establishment of TMDLs to only those uses and criteria in identified waters “that have first been listed as impaired pursuant to subsection (1)(A).” WASA Cross-Mtn. at 12. Recent 303(d) lists submitted to EPA by the District and Maryland list sediment and TSS pollution as impairing aquatic life in the Anacostia, but say nothing about recreational and aesthetic enjoyment of the watershed. DC, 2006 Integrated Report to the EPA and U.S. Congress app. 3.5, at 8, Ex. 1 to WASA Cross-Mtn., Sep. 18, 2009 [28-1] (“2006 DC 303(d) Report”); Maryland, 2006 List of Impaired Surface Waters and Integrated Assessment of Water Quality in Maryland 58, Ex. 3 to WASA Cross-Mtn., Sep. 18, 2009 [28-3] (“2006 MD 303(d) Report”). Accordingly, WASA maintains that “since the Anacostia has not been listed as impaired for the recreational and use designations due to sediment and TSS,” the “applicable” water quality standards to be addressed by the Final TMDL include only those related to aquatic life. Id. at 12-13. WASA’s understanding of the interaction between a 303(d) list and the obligation to develop TMDLs cannot be squared with the CWA’s plain text. First, WASA’s reading of the listing requirements confuses the CWA’s instruction to identify impaired waters with an extra-textual obligation to distinguish among water quality standards applicable to such waters. A return to basic grammar is instructive. Subsection (1)(A) is a single independent clause that includes a subject, a verb, and a direct object. Here, the clause directs the “State” to “identify” those “waters.” Two prepositional phrases then follow and clarify which “waters” should be identified. The first — “within its boundaries” — limits the waters to those found inside a State’s borders, while the second — “for which the effluent limitations ... are not stringent enough to implement any water quality standards applicable to such waters” — specifies only impaired waters. Obviously, a State must review applicable standards to determine whether a water body is impaired, just as it must review its boundaries to determine whether a water body is within its borders; but as part of the prepositional phrase, “standards” are not another direct object to be identified, but merely modify those direct objects to be identified — in this case, only those “waters” that are impaired. This focus on waters rather than standards is also underscored by the fact that the clause classifies a water body as impaired if any water quality standard is violated; in other words, whether one, some, or all of the water quality standards are not met, the water body is impaired and therefore must be listed. In short, the clause instructs a State to identify those waters for which water quality standards are not met — not to identify those standards. Second, even if subsection (1)(A) could be read to require identification of particular water quality standards, nothing in this provision can be read to imply that where a water quality standard is not “impaired,” it is no longer “applicable” to the water body. Indeed, subsection (1)(A) references all water quality standards “applicable to such waters.” Id. (emphasis added). A water quality standard is “applicable” to a particular water body if the particular designated uses and water quality criteria that form that standard apply to the water body under state law. Nowhere is it written that once a water quality criterion is attained and a designated use protected, that water quality standard is no longer “applicable.” Third, subsection (1)(C) requires the creation of TMDLs “for the waters identified in paragraph (1)(A) ... [and] at a level necessary to implement the applicable water quality standards.” 33 U.S.C. § 1313(d)(1)(C). This provision mirrors the language of subsection (1)(A), as the direct objects for the action — here, development of TMDLs — are “waters” identified in subjection (1)(A) and not particular water quality standards. Also similar is the use of “applicable” rather than “impaired” — load levels must be set to satisfy “applicable water quality standards.” In this context, the proper function of the term “applicable” is to narrow designated uses and water quality criteria from all possible standards to those specified as applicable to the water body under state law. The TMDL provision thus requires the development of pollutant limits for identified waters that satisfy applicable water quality standards, rather than TMDLs for particular standards. Fourth, WASA’s tortured interpretation of “applicable” in subsection (1)(C) is unsupported by any link between subsections (1)(A) and (1)(C). As an initial matter, the suggestion that “applicable” water quality standards in subsection (1)(C) are only those identified in subsection (1)(A) presupposes that subsection (1)(A) requires identification of the particular water quality standards that are impaired — which is incorrect. Supra. And to the extent that “applicable water quality standards” in subsection (1)(C) should be understood in reference to subsection (1)(A), as WASA urges, subsection (1)(A) does not distinguish between impaired and non-impaired water quality standards, but specifies “any water quality standards applicable to such waters.” 33 U.S.C. § 1313(d)(1)(A) (emphasis added). Reading these provisions together clarifies that subsection (1)(C)’s direction to develop TMDLs incorporates a requirement to protect any water quality standards that, under state law, are applicable to the water body in question. This reading is not only consistent with the parallel language employed in the two subsections’ mandates to identify impaired “waters” and then develop TMDLs for those identified “waters,” see Martini v. Fannie Mae, 178 F.3d 1336, 1345 (D.C.Cir. 1999) (explaining that statutes should be interpreted by reference to language and entire structure), but is also in line with the CWA’s “ambitious and comprehensive” scope. Kingman Park, 84 F.Supp.2d at 1. By contrast, WASA’s cramped reading of § 303(d) — which transforms the requirement to identify waters and develop TMDLs for waters into a requirement to identify and develop TMDLs for particular water quality standards — is antithetical to the Act’s holistic “goal of restoring and maintaining the chemical, physical and biological integrity of the nation’s waters.” Am. Coke & Chem. Inst. v. EPA, 452 F.3d 930, 943 (D.C.Cir.2006). Finally, even if WASA were correct that subsections (1)(A) and (1)(C) only obligate a State to identify impaired water quality standards and develop a TMDL to address those specific standards, its proposed interpretation would still fail because it improperly substitutes “designated uses” for “water quality standards.” The term water quality standard encompasses all designated uses of a water body and all water quality criteria that define pollutant levels necessary to protect those uses. Supra Section IV.A.1; see also 33 U.S.C. § 1313(c)(2)(A) (including “designated uses” as part of water quality standards). In this sense, designated uses are not equivalent to water quality standards, but are instead components of such standards. Cf. NRDC v. EPA, 16 F.3d 1395, 1400 (4th Cir.1993) (“To adopt these [water quality] standards, States must first classify the uses for which the water is to be protected, such as fishing and swimming, and then each State must determine the level of water quality necessary to protect those uses.”). The definition of water quality standard promulgated by EPA could not be clearer on this point: “A water quality standard defines the water quality goals of a water body, or portion thereof, by designating the use or uses to be made of the water and by setting criteria necessary to protect the uses.” 40 C.F.R. § 130.3 (emphasis added). And the principle enunciated in PUD No. 1 is equally instructive. In that case, the defendants attempted to sidestep an impaired designated use, arguing that the satisfaction of relevant water quality criteria is sufficient to meet applicable water quality standards. The Court rejected that position, concluding that water quality standards encompass “both components, namely the designated use and the water quality criteria.” PUD No. 1, 511 U.S. at 714-15, 114 S.Ct. 1900. Thus, subsection (1)(C)’s instruction to develop a TMDL protective of water quality standards is an instruction to determine the pollutant load level necessary to safeguard all designated uses. Had Congress intended otherwise, it could easily have worded the CWA to require identification of designated uses or water quality criteria that are not being met and to mandate development of TMDLs for such impairments; instead, Congress directed a State to identify “those waters” in which “any water quality standard applicable to such waters” is impaired and create TMDLs for “the [identified] waters.” 33 U.S.C. § 1313(d)(1)(A) & (C). The Court’s rejection of WASA’s argument thus echoes Judge Urbina’s identical conclusion in Friends I: “Of course, the TMDLs must achieve the [water quality standards] for all the designated uses of the Anacostia River.” 346 F.Supp.2d 182, 195 (D.D.C. 2004) (emphasis added). The Court’s interpretation of the CWA is also consistent with regulations concerning the creation of 303(d) lists and the development of TMDLs for waters identified on such submissions. EPA regulations governing the listing of impaired waters provide: Each State shall identify those water quality-limited segments still requiring TMDLs within its boundaries for which (i) Technology-based effluent limitations ... (ii) More stringent effluent limitations (including prohibitions) required by either State or local authority ... and (iii) Other pollution control requirements ... are not stringent enough to implement any water quality standards (WQS) applicable to such waters. 40 C.F.R. § 130.7(b)(1). Mirroring the language of subsection (1)(A), this provision requires a State to identify the waters that do not meet “applicable” standards. Id. Nothing in this provision, however, requires a State to further subdivide its 303(d) list by identifying particular designated uses that are impaired. Quite the contrary, § 130.7 explains that, “for purposes of listing waters,” the term “water quality standard applicable to such waters” means “those water quality standards established under section 303 of the Act, including numeric criteria, narrative criteria, waterbody uses, and antidegredation requirements.” Id. § 130.7(b)(3) (emphasis added). Consistent with the CWA, this provision references water quality standards “established” under § 303 of the Act — not standards identified as impaired on a State’s 303(d) list. And under § 303, water quality standards incorporate by definition all designated uses of a particular water body. 33 U.S.C. § 1313(c)(2)(A). WASA, however, points to EPA regulations stating that “TMDLs shall be established at levels necessary to attain and maintain the applicable narrative and numerical WQS,” id. § 130.7(c)(1), to support its contention that there is no regulatory requirement “that TMDLs address all designated uses.” WASA Reply in Support of Cross-Mtn. for Summary Judgment 7-8, Oct. 28, 2009 [41] (“WASA Reply”). As an initial matter, this interpretation of EPA’s regulation is inconsistent with the CWA’s plain meaning, which requires a TMDL to address all “applicable water quality standards,” 33 U.S.C. § 1313(d)(1)(C) — meaning “any water quality standard applicable to such waters,” id. § 1313(d)(1)(A) (emphasis added), inclusive of all designated uses. Id. § 1314(c)(2)(A). As the Supreme Court made clear, “under the literal terms of the statute, a project that does not comply with a designated use of the water does not comply with the applicable water quality standards.” PUD No. 1, 511 U.S. at 715, 114 S.Ct. 1900; see also Friends I, 346 F.Supp.2d 182, 195 (D.D.C.2004). Thus, to the extent WASA properly interprets this regulation as permitting TMDLs that do not address all applicable designated uses, the provision is contrary to the CWA and invalid. See Orion Reserves Ltd. P’ship v. Salazar, 553 F.3d 697, 703 (D.C.Cir.2009) (“[A] regulation contrary to a statute is void.”). WASA’s attempt to read out designated uses from water quality standards as used in § 130.7(c)(1) also ignores EPA’s instruction — in this same provision — that “[d]e-terminations of TMDLs shall take into account critical conditions for stream flow, loading and water quality parameters.” 40 C.F.R. § 130.7(c)(1) (emphasis added). In contrast to WASA’s conflicting and unduly narrow reading of § 130.7(c)(1), the Court finds that the phrase “applicable narrative and numeric WQSs,” 40 C.F.R. § 130.7(c)(1), is easily harmonized with the CWA and its implementing regulations by reference to EPA’s explanation elsewhere that “water quality criteria” are “based upon” designated uses. Id. § 130.2(d). As EPA regulations make clear: “When criteria are met, water quality will generally protect the designated use.” Id. § 131.3(b). Because water quality criteria are measurable baselines — compared to less-tangible concepts such as designated uses — a State is apt to focus on these criteria when developing pollutant load limits for a TMDL, comforted in the knowledge that attaining these criteria will generally ensure protection of the designated uses. Thus, the use of the phrase “narrative and numeric WQSs” is best understood to instruct the State to consider all water quality criteria — narrative or numeric — to ensure that all designated uses are preserved. Finally, WASA quotes a single sentence from 65 pages of EPA guidance stating that a State may sub-categorize its 303(d) list to “show that some designated uses of a water are being attained and some designated uses are not.” EPA, Memorandum: Guidance for 2006 Assessment, Listing and Reporting Requirements Pursuant to Sections 303(d), 305(b) and 314 of the Clean Water Act, July 29, 2005, available at http://www.epa.gov/owow/tmdl/2006IRG/ reporty2006irg-report.pdf (“2006 Guidance”). According to WASA, this guidance permits a State to list pollutants as only affecting certain designated uses, “thereby limiting their TMDL obligations and those of EPA to the listed use impairments.” WASA Reply at 9. This is incorrect. As an initial matter, to the extent WASA’s reading of this guidance is proper, its interpretation would be inconsistent with the CWA’s plain language and therefore unworthy of deference. Adams v. Bell, 711 F.2d 161, 184-85 (D.C.Cir.1983). Moreover, even a cursory review of the 2006 Guidance negates the implications divined by WASA. Perhaps most critically, the very sentence at issue states that sub-categorizations in the 303(d) list are optional. 2006 Guidance at 6. The Court will not hold that a one-line description of an “optional” categorization in a 303(d) list authorizes a State — at its own discretion— to fundamentally alter its burdens in developing TMDLs under the CWA. Cf. Interstate Natural Gas Ass’n of Am. v. FERC, 285 F.3d 18, 59 (D.C.Cir.2002) (explaining courts’ reluctance to review “tentative agency positions” because they lack “present binding effect”). WASA’s argument is further undermined by a related footnote in the 2006 Guidance emphasizing that States “determine their section 303(d) list ... consistent with 40 C.F.R. § 130.7(b)(3).” Id. at 6 n. 2. That regulatory provision defines applicable water quality standards as those developed under § 303 of the Act, which includes all designated uses. 40 C.F.R. §§ 130.7(b)(3) & 131.3. In addition, the 2006 Guidance goes on to explain that States should list waters in one of five categories, including Category 4, which consists of waters where “at least one designated use is not being supported ... but a TMDL is not needed,” and Category 5, which includes waters where “at least one designated use is not being supported ... and a TMDL is needed.” 2006 Guidance at 7. Here, Category 5 may be applicable; however, nothing in EPA’s discussion of how to create a Category 5 listing so much as suggests that a State that lists only a particular designated use as impa