Small MS4 Coalition v. Dept. of Environment

Maryland Small MS4 Coalition, et al. v. Maryland Department of the Environment, No. 1865, September Term 2019. Opinion by Harrell, J. 1. ADMINISTRATIVE LAW AND PROCEDURE - County permittee was entitled to remand of a decision of the Department of the Environment which designated areas outside of the county’s actual urbanized area for coverage under a federal stormwater discharge permit where objections to the Department’s decision were not ascertainable reasonably during the public comment period but arose after the comment period closed. Md. Code, Environment Article § 1-601(d). 2.

ENVIRONMENTAL LAW – Federal stormwater discharge permit issued to a small municipal separate storm sewer system (“small MS4”) must contain water quality based effluent limitations consistent with assumptions and requirements of the applicable wasteload allocation established in the Chesapeake Bay Total Maximum Daily Load (“TMDL”) and allocated to regulated stormwater sources in the Maryland Watershed Implementation Plan. 40 C.F.R. § 122.44 (d)(1)(vii)(B). 3. ENVIRONMENTAL LAW – The Department of the Environment is authorized to include terms and conditions in a permit issued to a regulated small MS4 that are more stringent than federal regulations require, where such terms and conditions are based on an approved TMDL or equivalent analysis, and the Department determines that such terms and conditions are needed to protect water quality. 40 C.F.R. § 122.34 (c)(1). 4. ENVIRONMENTAL LAW – The Department of the Environment did not exceed its authority under the Clean Water Act when it directed small permittees to calculate impervious surface restoration requirements using total impervious acreage within the urbanized area as a baseline. Impervious surface restoration requirement represents a valid reallocation of pollutant loads from nonpoint sources to point sources, in order to achieve water quality standards based on the Chesapeake Bay TMDL. 5.

ENVIRONMENTAL LAW – The Department of the Environment did not act arbitrarily or capriciously in establishing permit provisions for federally-required control measures designed to detect/eliminate illicit discharges into the MS4 and prevent or reduce pollutant runoff from land owned or operated by the county. The administrative record reveals a rational basis for and/or substantial evidence to support the Department’s decision to include the permit requirements. Circuit Court for Queen Anne’s County Case No. C-17-CV-18-000162 REPORTED IN THE COURT OF SPECIAL APPEALS OF MARYLAND No. 1865 September Term, 2019 ______________________________________ MARYLAND SMALL MS4 COALITION, ET AL. v. MARYLAND DEPARTMENT OF THE ENVIRONMENT ______________________________________ Beachley, Wells, Harrell, Glenn T., Jr. (Senior Judge, Specially Assigned), JJ. ______________________________________ Opinion by Harrell, J. ______________________________________ Filed: April 29, 2021 Pursuant to Maryland Uniform Electronic Legal Materials Act (§§ 10-1601 et seq. of the State Government Article) this document is authentic. 2021-04-29 * Kehoe, J., did not participate in the Court’s 11:44-04:00 decision to report this opinion pursuant to Maryland Rule 8-605.1. Suzanne C. Johnson, Clerk “Letting the days go by, let the water hold me down Letting the days go by, water flowing underground Into the blue again, into the silent water Under the rocks and stones, there is water underground.” Lyrics from “Once in a Lifetime” from the album “Remain In Light” by The Talking Heads (Sire Records, 1981).

This appeal flows from a petition, filed in the Circuit Court for Queen Anne’s County, requesting judicial review of a final determination of the Maryland Department of the Environment (“Department”), appellee, to issue a conditional general stormwater discharge permit to a number of operators of “small” municipal separate storm sewer systems (MS4s) (we shall do a deeper dive explaining this term shortly), including Queen Anne’s County (“the County”), appellant. The circuit court affirmed the Department’s final determination. The County noted an appeal from the decision of the circuit court, presenting the following questions for our consideration: 1. Has [the Department] acted unlawfully by designating geographic areas outside of the urbanized area for regulation under the General Permit? 2.

Has [the Department] unlawfully made the County responsible for discharges from independent third parties and nonpoint source runoff that does not flow into or discharge from the County’s MS4? 3. Has [the Department] unlawfully imposed requirements beyond the maximum extent practicable in the General Permit? For the following reasons, we shall vacate, in part, the judgment of the circuit court and remand to that court with instructions to remand the matter to the Department for further proceedings consistent with this opinion. We shall affirm otherwise the judgment.

BACKGROUND A. Statutory and Regulatory Scheme The permit here was issued by the Department pursuant to authorization under the federal Clean Water Act, 33 U.S.C. § 1251 through § 1388 (“CWA”). Congress enacted the CWA in 1972 to “restore and maintain the chemical, physical, and biological integrity of the Nation’s waters.” 33 U.S.C. § 1251 (a). One of the core provisions of the CWA is § 1311(a), which “generally prohibits ‘any person’ from discharging pollutants from a point source into a waterway.”1 Maryland Department of the Environment v. County Commissioners of Carroll County, 465 Md. 169, 184 (2019) (quoting 33 U.S.C. § 1311 (a)) (footnotes omitted), cert. denied sub nom. County Commissioners of Carroll County, Maryland v. Maryland Dep’t of the Env’t, 140 S. Ct. 1265 (2020). “Through the National Pollution Discharge Elimination System (“NPDES”), 33 U.S.C. § 1342 , either the Environmental Protection Agency (“EPA”) or an EPA-approved state, such as Maryland, may issue permits exempting a discharger from this prohibition.” Maryland Department of the Environment v. Anacostia Riverkeeper, 447 Md. 88, 96 (2016) (footnote omitted).

The Department is authorized by the EPA to administer the NPDES program in Maryland. Id. (citing Code of Maryland Regulations (“COMAR”) 26.08.04.07). 1 “‘[P]erson’ means an individual, corporation, partnership, association, State, municipality, commission, or political subdivision of a State, or any interstate body.” 33 U.S.C. § 1362 (5). “The term ‘point source’ means any discernible, confined and discrete conveyance, including but not limited to any pipe, ditch, channel, [or other types of conveyance], from which pollutants are or may be discharged.” 33 U.S.C. § 1362 (14). 2 Maryland’s NPDES permit program must be consistent with the CWA and with EPA guidelines. 33 U.S.C. § 1342 (c)(2). “To achieve water quality standards, the [CWA] requires that discharge permits include pollution controls for point sources.” Carroll County, 465 Md. at 186 (citing 33 U.S.C. § 1311 (b)). “‘Generally speaking, the NPDES requires dischargers to obtain permits that place limits on the type and quantity of pollutants that can be released into the Nation’s waters.’” Anacostia Riverkeeper, 447 Md. at 96 (quoting S. Fla. Water Mgmt.

Dist. v. Miccosukee Tribe, 541 U.S. 95, 102 (2004)). “These limits are called effluent limitations.”2 Id. At issue in this appeal is a permit for a type of “point source” discharge known as a municipal separate storm sewer system, commonly referred to as an MS4. “An MS4 is a network of conveyances (including storm drains, gutters, and other drainage systems) designed to carry only stormwater (as opposed to a ‘combined sewer system’ that conveys both sanitary sewage and stormwater).” Carroll County, 465 Md. at 188 (citing 40 C.F.R. § 122.26 (b)(8)). “Stormwater” is the “rain and snowmelt that filters through the soil and courses over surfaces – collecting pollutants along the way – before passing through the municipal storm sewer systems and into waterbodies.” Anacostia Riverkeeper, 447 Md. at 97 (footnote omitted). 2 An “effluent limitation” is defined as “any restriction established by a State or the [EPA] on quantities, rates, and concentrations of chemical, physical, biological, and other constituents which are discharged from point sources into navigable waters, the waters of the contiguous zone, or the ocean, including schedules of compliance.” 33 U.S.C. § 1362 (11). 3 MS4s differ from other “point sources” of water pollution, such as a discharge pipe from a factory, in that the quantity and quality of stormwater that is conveyed by an MS4 into a waterway varies, depending on weather and land use practices. Carroll County, 465 Md. at 188-89 . In addition, it is “difficult to discern the amount of pollutant that any one [MS4] discharger contributes to a waterbody because municipalities have so many outfalls, or discharge points, leading into the waters.” Anacostia Riverkeeper, 447 Md. at 98 .

Accordingly, instead of numerical effluent limitations, “an MS4 permit generally requires the permittee to implement flexible management programs designed to reduce the pollution introduced into stormwater, thereby limiting the amount of pollution discharged into the waterway.” Carroll County, 465 Md. at 189 (footnote omitted). Under the CWA, municipal stormwater permits must require “controls” that will “reduce the discharge of pollutants to the maximum extent practicable[.]” 33 U.S.C. § 1342 (p)(3)(B)(iii). The required “controls” include “management practices, control techniques and system, design and engineering methods,” as well as “such other provisions as the [EPA] or the State determines appropriate for the control of such pollutants.” Id. “Best management practices,” or, as they are commonly referred to, “BMPs,” “have been a long-standing control or effluent limitation in MS4 permits.” Anacostia Riverkeeper, 447 Md. at 99 (citing 40 C.F.R. §§ 122.44 (k)(2) and (3)). EPA regulations define BMPs as “[m]ethods, measures or practices selected by an agency to meet its nonpoint source control needs.” 40 C.F.R. § 130.2 (m). “BMPs include but are not limited to structural and nonstructural controls and operation and maintenance procedures.” Id.

The EPA has defined BMPs more specifically, stating that “BMPs can be either 4 nonstructural (good housekeeping practices, pollution prevention, contour plowing, cover crops) or structural (wet or dry detention ponds), and can include treatment requirements, operating procedures, and practices to control site runoff, spillage, or leaks.”3 The NPDES discharge permit program for MS4s has been put into operation in two phases, beginning with systems serving larger and denser populations. Phase I included “large” MS4s, which serve populations of 250,000 or more, and “medium” MS4s, which serve populations of 100,000 to 249,999. Carroll County, 465 Md. at 243-44 .4 Phase II extended the permit requirement to “small” MS4s, such as those operated by the County, which serve fewer than 100,000 people. Id. at 245 .

The permit at issue here is a Phase II general permit issued to a group of small MS4 operators.5 Significantly, not all small MS4s are subject to regulation under the NPDES program. Operators of small MS4s, including, but not limited to, systems operated by federal, state and local governments, require a permit to discharge stormwater only if: (1) 3 EPA, Introduction to the Clean Water Act at 81, available at https://cfpub.epa.gov/watertrain/pdf/modules/introtocwa.pdf (last visited 25 March 2021). 4 Also included in Phase I were MS4s that were “determined by the EPA or a state to be significant contributors of pollutants, regardless of the size of the population served by those MS4s.” Maryland Dep’t of the Env’t v. County Commissioners of Carroll County, 465 Md. 169, 243-44 (2019), cert. denied sub nom. County Commissioners of Carroll County, Maryland v. Maryland Dep’t of the Env’t, 140 S. Ct. 1265 (2020). 5 A general permit sets forth required terms and conditions applicable to all eligible small MS4s, although additional terms and conditions may be established for individual small MS4 operators. 40 C.F.R. § 122.28 (d). A permittee complies with permit application requirements by submitting a notice of intent. 40 C.F.R. § 122.28 (d)(2)(i). 5 the small MS4 is located within an “urbanized area,”6 40 C.F.R. § 122.32 (a)(1); (2) the Department determines that storm water discharge from the small MS4 “results in or has the potential to result in exceedances of water quality standards, including impairment of designated uses, or other significant water quality impacts, including habitat and biological impacts” 40 C.F.R. 123.35(b)(1); or (3) the Department determines that stormwater discharge from the small MS4 “contributes substantially to the pollutant loadings of a physically interconnected municipal separate storm water sewer that is regulated by the NPDES storm water program.” 40 C.F.R. 123.35(b)(4).

Only the first two conditions are relevant here. To determine whether small MS4s that are located outside of an urbanized area should be subject to regulation, the Department must first “[d]evelop criteria to evaluate whether a storm water discharge results in or has the potential to result in exceedances of water quality standards, including impairment of designated uses, or other significant water impacts, including habitat and biological impacts.” 40 C.F.R. § 123.35 (b)(1)(i). The permitting authority then must apply that criteria to small MS4s located outside of an urbanized area.7 40 C.F.R. § 123.35 (b)(2). Any small MS4 that meets the criteria must be designated for regulation and issued a discharge permit. 40 C.F.R. § 123.35 (b)(3), (d). 6 For purposes of the NPDES permit program, an “urbanized area” is “determined by the latest Decennial Census by the Bureau of the Census.” 40 C.F.R. § 122.32 (a)(1). “If [a] small MS4 is not located entirely within an urbanized area, only the portion that is within the urbanized area is regulated[.]” Id. 7 The regulations require that the criteria be applied “at a minimum, to any small MS4 located outside of an urbanized area serving a jurisdiction with a population density (continued) 6 Under certain conditions, the Department may waive or phase-in the requirements applicable to regulated small MS4s. 40 C.F.R. § 122.32 (d) and (e); § 123.35(d).

Where a general permit is issued, an owner or operator of a small MS4 may request to be excluded from the coverage of the general permit by applying for an individual permit. 40 C.F.R. § 122.28 (b)(3)(iii).8 The procedure the Department must follow in issuing a permit is set forth in the Environment (“EN”) Article. It requires “published notice of permit applications (EN § 1- 602), informational meetings (EN § 1-603), and publication of [the Department’s] tentative determination (EN § 1-604(a)).” Potomac Riverkeeper, Inc. v. Maryland Department of the Environment, 238 Md. App. 174, 204 (2018). “If the tentative determination is to [issue the permit], EN § 1-604(a)(3) requires [the Department] to prepare a draft permit and ‘publish a notice of the tentative determination’ that provides 30 days for public comment, and, if requested, hold a public hearing pursuant to EN § 1-604(a)(4).” Id. If, during the notice and comment period, the Department receives comments adverse to its tentative determination, the Department is required to prepare and publish a notice of the final determination. EN § 1-604(b).9 “[T]he final version of the permit of at least 1,000 people per square mile and a population of at least 10,000[.]” 40 C.F.R. § 123.35 (b)(2). 8 The County has not tested these waters. 9 “If the Department is not required to prepare a final determination . . . the tentative determination is a final decision by the Department when the permit is issued or denied.” EN § 1-604(b)(3). 7 adopted in the final determination need not be identical to the one previously made available for public comment.” Potomac Riverkeeper, 238 Md. App. at 204 .

As we have observed, “[a]n alternative requirement precluding amendments could lead to a never- ending cycle of comments and revisions.” Id. Moreover, there is no provision for additional public comment on the Department’s final determination and revised final permit. Id. A final determination of the Department to issue a discharge permit is subject to judicial review in the circuit court.

EN § 1-601(c). The decision of the circuit court may be appealed to this Court. EN § 1-601(e)(2). B. Tentative Determination On 22 December 2016, the Department notified the County and 34 other counties and municipalities of its tentative determination to issue an NPDES general permit for discharges from small MS4s.

The County was one of 13 newly designated for coverage under the Phase II permitting process. A draft of the permit was made available for review. The Department advised that a public hearing concerning the tentative determination would be held on 6 February 2017, and that written comments concerning the tentative determination would be accepted through 30 March 2017. Pertinent to this appeal, the Department’s tentative determination was that all MS4s throughout the County were subject to regulation under the general permit.

The Department’s stated justification was that the County as a whole “is located within an urbanized area.” 8 Also relevant is a proposed condition of the permit that requires permittees to initiate efforts to restore twenty percent of the total impervious surface area within the urbanized area of the MS4 jurisdiction that has little or no stormwater management.10 Permittees are required to perform watershed assessments, identify water quality improvement opportunities, secure appropriate funding, and develop an implementation schedule to demonstrate that the twenty percent impervious area restoration requirement will be achieved by 2025. C. Comment Period The County participated in the public hearing. Todd Mohn, the County’s Director of Public Works, gave brief comments in which he questioned the County-wide designation based on location within an urbanized area. Mr. Mohn stated that the tentative determination was still under review and that the County reserved the right to provide further comment.

In written comments submitted on 30 March 2017, the County maintained that the scope of the proposed permit was overbroad, as less than four percent of the County fell within an urbanized area as defined by statute and regulation. The County commented further that the draft permit should be clarified to state that the twenty percent restoration 10 An “impervious surface” is an area that has “been paved or otherwise developed, as opposed to natural, undeveloped areas.” Carroll County, 465 Md. at 195 . “To ‘restore’ an impervious surface is to make it function more like a natural terrain that absorbs and filters rain water.” Id. Examples of restoration efforts listed in the general permit include environmental site design, structural stormwater controls, retrofitting, and stream restoration. 9 requirement applied only to the impervious coverage within the legitimate urbanized area that is served by the County’s MS4. The County expressed support for the joint comments submitted by the Maryland Association of Counties, the Maryland Municipal League, and the Maryland Municipal Stormwater Association (collectively, “Associations”).

One of the concerns articulated in the Associations’ comments was that the Department had stated and applied improperly the criteria for designating small MS4s for coverage: [t]he Draft [general permit] appears to designate an entire jurisdiction if only a part of the jurisdiction is within an [urbanized area]. This is manifestly improper. [The Department] should clarify in the final [general permit] and Fact Sheet that, for any small MS4 owned or operated by a jurisdiction identified on Table A.1 as “within an urbanized area,” the permit’s requirements apply only to portions of the MS4 within the [urbanized area]. For these reasons, the Associations object to the designation of any jurisdiction on Table A.1 unless that jurisdiction owns or operates an MS4 within an [urbanized area]. And among the potential designees based on the [urbanized area] criterion, if a particular jurisdiction provides information that its MS4 is located outside of the [urbanized area], it should not be required to obtain permit coverage, and should be dropped from Table A.1 (unless the locality voluntarily elects to accept the designation.) In addition, the Associations asserted that the baseline impervious area assessment used to calculate the twenty percent restoration requirement should not include any impervious area not served by the MS4.

The Associations maintained that “a permittee is not responsible for nonpoint sources (properties with sheet flow from the parcel[s] into streams, creeks, etc.) and third-party direct dischargers (properties with their own discharge points into streams, creeks, etc.) that do not enter into and are not discharged from the permittee’s MS4.” 10 A third concern raised by the Associations is that the twenty percent restoration requirement and other terms of the permit exceeded the “maximum extent practicable” (“MEP”) standard for many potential permittees and was therefore unlawful. D. Final Determination On 27 April 2018, the Department issued a final determination to issue the general permit, together with a document entitled “Basis for Final Determination” that provided an explanation for its actions and responded to public comments addressed to the tentative determination. The Basis for Final Determination included information regarding a process and criteria used to designate MS4s located in non-urbanized areas. The Department also addressed comments regarding impervious area restoration requirements and concerns about permit conditions in excess of the MEP, into which we shall delve in greater detail later in this opinion.

Contemporaneous with the final determination, the Department sent a letter to the County, stating a different rationale than in the tentative determination for designating the entire geographic area of the County. In lieu of justifying inclusion of the County as a whole, based on a finding that it was located within an urbanized area, the Department explained, apparently for the first time, that it had evaluated MS4s outside of the urbanized areas and determined that the “County’s stormwater discharges result in or have the potential to result in exceedances of water quality standards or other significant water quality impacts,” and therefore were subject to regulation pursuant to 40 C.F.R. § 123.35 (b)(1)(i). The Department described the designation process and criteria as follows: 11 The Department’s water quality criteria for evaluating MS4s in non- urbanized areas are based on the State’s TMDL program and the Maryland Biological Stream Survey (MBSS).[11] Maryland’s TMDL program includes water quality assessments found in the Integrated Report of Surface Water Quality [ ] which identifies waters that meet water quality standards, and waterways that are impaired or threatened and require TMDLs. Documentation includes watershed assessments, water quality data, and mapping of impaired waterways.

These water quality analyses are reviewed by the Department to determine whether MS4 discharges may contribute to stream impairments or exceedances of water quality standards. The MBSS data are a comprehensive compilation of local water quality conditions throughout the State of Maryland. The data are based on field protocols that evaluate stream impairments and water quality through fish and habitat indicators. The MBSS data show that streams receiving stormwater runoff from urban development often have degraded biological communities.

Results of these field surveys provide ratings of “good”, “fair”, “poor”, or “very poor” indicating overall stream health. The MBSS data are reviewed by the Department to determine whether MS4 discharges have the potential to impact biological and habitat conditions in local streams. The Department stated that, in accordance with that process and criteria, it had evaluated MS4s in the County that are located outside the urbanized area and made the following findings: • The majority of local TMDLs in Queen Anne’s County are located outside of the urbanized area, and significant urban land use exists outside of the Centreville Urban Cluster. Local TMDLs include impairments for bacteria in Corsica River, Lower Choptank River Mainstem, Eastern Bay, Wells Cove, Wye River, and Lower Chester River; mercury in Tuckahoe Lake; nutrients in Corsica River and Middle Chester River; polychlorinated biphenyls (PCBs) in Corsica River; and phosphorus in Southeast Creek. 11 TMDL is an acronym for “total maximum daily load,” which is “a measure of the total amount of a pollutant from point sources, nonpoint sources and natural background, that a water quality limited segment can tolerate without violating the applicable water quality standards.” Potomac Riverkeeper, Inc. v. Maryland Dep’t of the Env’t, 238 Md. App. 174, 185 (2018) (citation omitted). 12 • 26 MBSS stations located outside of the urbanized area indicate a score of poor or very poor stream health for numerous streams and watersheds.

Many of these are located in unnamed tributaries in the Corsica River watershed and streams in the Chester River watershed including Red Lion Branch and Andover Branch. • The 2016 Integrated Report documented that Rosin Creek and an unnamed tributary to the Upper Chester River are impaired due to total suspended solids (TSS), indicating that these streams do not meet water quality standards. • Tributaries draining into the Centreville Urban Cluster and the Corsica River are impaired by an unknown source affecting aquatic life. After setting forth its findings, the Department concluded that: [s]tormwater discharges inside and outside of the County’s urbanized area contribute to these water quality impairments and future MS4 discharges have the potential to cause significant water quality impacts.[12] Because of the link between the County’s MS4 discharges and water quality impairment, the geographic area under the authority of Queen Anne’s County has been designated by the Department for coverage under the general permit. Subsequently, the County must submit a Notice of Intent (NOI) in accordance with the general permit and obtain coverage under the NPDES MS4 program. The County did not submit a Notice of Intent, but filed instead a petition for judicial review of the Department’s final determination.

The circuit court affirmed the Department’s decision to approve and issue the general NPDES discharge permit. This appeal followed.13 Additional facts will be introduced later in this opinion. 12 In a footnote, which we have omitted, the Department provided a link to the water quality documentation referred to in the letter. 13 The appeal was filed originally by the Maryland Small MS4 Coalition, representing Queen Anne’s County and Cecil County, and by Queen Anne’s County as a separately named party. Cecil County dismissed its appeal. 13 STANDARD OF REVIEW “In an appeal of the circuit court’s review of an agency action, an appellate court reviews the agency’s action itself rather than the decision of the circuit court.” Carroll County, 465 Md. at 201 (citing Hollingsworth v. Severstal Sparrows Point, LLC, 448 Md. 648, 654 (2016)). “Our role is ‘limited to determining if there is substantial evidence in the record as a whole to support the agency’s findings and conclusions, and to determine if the administrative decision is premised upon an erroneous conclusion of law.’” Richardson v. Maryland Dep’t of Health, 247 Md. App. 563, 569 (2020) (quoting Milliman, Inc. v. Md. State Ret. and Pension Sys., 421 Md. 130, 151 (2011)), cert. denied sub nom. Richardson v. Md. Dep’t of Health, 472 Md. 17 (2021). “The standards for judicial review of a discharge permit – and their corresponding levels of deference to the agency – vary depending on whether the court is reviewing an agency’s fact findings, discretionary decisions, or legal conclusions.” Carroll County, 465 Md. at 201 (citing Anacostia Riverkeeper, 447 Md. at 118-21 ).

The Court of Appeals summarized these varying standards as follows: Review of Fact Findings For fact findings, a reviewing court applies the “substantial evidence” standard, under which the court defers to the facts found and inferences drawn by the agency when the record supports those findings and inferences. Anacostia Riverkeeper, 447 Md. at 120 , 134 A.3d 892 . In particular, with respect to factual issues that involve scientific matters within an agency’s area of technical expertise, the agency is entitled to “great deference.” Id. Review of Matters Committed to the Agency’s Discretion With respect to matters committed to agency discretion, a reviewing court applies the “arbitrary and capricious” standard of review, which is “extremely deferential” to the agency.

Harvey v. Marshall, 389 Md. 243 , 14 296-99, 884 A.2d 1171 (2005); Spencer v. Md. State Bd. of Pharmacy, 380 Md. 515, 529 , 846 A.2d 341 (2004). This standard is highly contextual, but generally the question is whether the agency exercised its discretion “unreasonably or without a rational basis.” Harvey, 389 Md. at 297 , 884 A.2d 1171 ; Arnold Rochvarg, Maryland Administrative Law, § 20.1 at 255 (2011). Under this standard, a reviewing court is not to substitute its own judgment for that of the agency and should affirm decisions of “less than ideal clarity” so long as the court can reasonably discern the agency’s reasoning. Bowman Transp., Inc. v. Arkansas-Best Freight System, Inc., 419 U.S. 281, 285-86 , 95 S.Ct. 438 , 42 L.Ed.2d 447 (1974).

Review of the Agency’s Legal Conclusions With respect to an agency’s legal conclusions, a reviewing court accords the agency less deference than with respect to fact findings or discretionary decisions. Anacostia Riverkeeper, 447 Md. at 122 , 134 A.3d 892 . In particular, a court will not uphold an agency action that is based on an erroneous legal conclusion. Id.

However, in construing a law that the agency has been charged to administer, the reviewing court is to give careful consideration to the agency’s interpretation. Id. at 201-03 . Our review of the Department’s final determination to issue the permit is based on the administrative record before the Department. EN § 1-601(d).

We limit our review to objections raised during the public comment period. Id. If, however, the petitioner seeking judicial review demonstrates that “(i) [t]he objections were not reasonably ascertainable during the comment period; or (ii) [g]rounds for the objection arose after the comment period[,]” we must remand to the Department for consideration of such objections. Id.

Remand is not required “if the proffered new objections are not materially different from objections that were already considered” by the Department. Potomac Riverkeeper, 238 Md. App. at 205 . 15 ANALYSIS The County identifies two provisions of the permit as relevant to this appeal. The first is the designation of the area subject to regulation. The County argues that the Department’s designation of areas outside of the actual urbanized area of the County (1) exceeded the Department’s authority, (2) was procedurally deficient, and (3) was not supported by substantial evidence.

The second provision the County challenges is the requirement that it commence restoration efforts for twenty percent of impervious acreage within the urbanized area. The County asserts that this condition unlawfully makes it responsible for third-party and nonpoint source stormwater discharges. The County further asserts that the Department lacks authority to impose conditions that exceed the “maximum extent practicable” standard, and, therefore, the restoration requirement and any other permit conditions that exceed that standard are invalid. We shall address the County’s contentions in turn.

I. Designation of Area Subject to Permit The County concedes that the portion of its MS4 that is located in the actual urbanized area is subject to regulation under the CWA. The County asserts, however, that the Department’s designation of MS4s outside of the urbanized area, based on purported links to broader and perhaps non-contemporary water quality impairments, was contrary to federal and State law because (1) the Department did not provide notice of the process or criteria used in the designation process until after the opportunity for public comment expired, and (2) the Department’s finding of a causal or potentially causal connection 16 between waterbody impairment and discharge from County-operated MS4s outside of the urbanized area was not supported by substantial evidence. The Department maintains that the County had ample opportunity to raise concerns regarding the area of designation because the County participated in informal discussions regarding the designation criteria in the federal regulations and their applicability to the County. The Department asserts further that, based on data showing impairments in water quality in rivers and streams flowing through the County, it was reasonable for the Department to find that County-operated MS4s located outside of the urbanized area at least contributed potentially to excesses in water quality standards or resulted in other significant water quality impacts in the County.

Based on our review of the administrative record, we conclude that, pursuant to EN §1-601(d), remand is required because the grounds for the Department’s ultimate determination that there was a link between the County’s MS4s and water quality impairments were not reasonably ascertainable during the comment period, but were evident only when the final determination was issued, after the comment period expired. We explain. When the Department issued its tentative determination and published the draft general permit for public comment, the justification for designating all County-operated MS4s for regulation under the general permit was they were “located within an urbanized area.” The County objected to that justification on grounds that only a small area of the County was actually an urbanized area. In the Department’s final determination, however, it revised its justification for designating all MS4s in the County, asserting that, based on 17 criteria which apparently had not been made public previously, the Department had determined that “[s]tormwater discharges inside and outside of the County’s urbanized area contribute to [ ] water quality impairments[,] and future MS4 discharges have the potential to cause significant water quality impacts.” The Department’s contention that the County had an opportunity to object to the Department’s designation of MS4s outside of the urbanized area prior to the issuance of the final determination is not supported by the record.

The email correspondence that the Department highlights in support of this contention was sent prior to the tentative determination and explains the designation of the entire County pursuant only to the urbanized area criteria in 40 C.F.R. § 122.32 (a)(1). The Department points also to documentation that demonstrates generally that the County participated in informal meetings regarding the Department’s tentative determination. We can find nothing in that documentation, or elsewhere in the record, however, demonstrating that, prior to the expiration of the comment period, the County was put on notice of the Department’s determination that MS4s outside of the County’s actual urbanized area were subject to regulation based on a purported link to water quality impairments, pursuant to 40 C.F.R. § 123.35 (b)(1)(i). Nor does it appear that such a determination was a foreseeable response to the comments made during the public comment period.

Cf. Potomac Riverkeeper, 238 Md. App. at 211 (holding that interested parties had adequate opportunity to anticipate and comment on terms of final permit as such terms were a reasonably foreseeable response to public comments). We conclude that the County’s objections to the final determination 18 regarding the area of designation were not “reasonably ascertainable” during the comment period, but were evident only upon issuance of the final determination. Consequently, pursuant to EN § 1-601(d), remand is required to allow the County an opportunity to comment on the Department’s determination that MS4s outside of the urbanized area of the County are subject to regulation under the NPDES, and so that the Department may consider the County’s objections.

To those ends, we shall vacate the circuit court’s judgment affirming the Department’s final determination as it pertains to the area of the County that is subject to regulation under the general permit and remand to the circuit court with instructions to remand to the Department for further proceedings consistent with this opinion. Because the County concedes that the portion of its MS4 located within the actual urbanized area is subject to the permitting requirements of the Clean Water Act, we shall consider the remaining issues as they may apply to whatever the permit area turns out to be.

II

Responsibility for Nonpoint Source Runoff and Third-Party Discharge? The County contends that the Department exceeded its jurisdictional authority by imposing permit conditions that assign responsibility to the County to remediate pollutants in stormwater that does not enter the County’s MS4, such as nonpoint source runoff or third-party discharge. In support of this contention, the County relies on 40 C.F.R. § 122.26 (a)(9)(i)(A), which, as it applies to small MS4s, provides that “for discharges composed entirely of storm water . . . operators shall be required to obtain a NPDES permit 19 only if . . . [t]he discharge is from a small MS4 required to be regulated pursuant to [40 C.F.R.] § 122.32.” (emphasis added). On this point, the County focuses primarily on the requirement to restore twenty percent of all untreated impervious surface within the urbanized area.

Because the entire urbanized area of the County is not served by the County’s MS4, requiring restoration of twenty percent of the total impervious surface area within the urbanized area makes the County responsible for nonpoint source runoff that does not enter and therefore is not discharged from its MS4. Similarly, the County claims that the total impervious surface in the urbanized area includes privately-owned industrial, residential, and commercial developments that often have their own stormwater drainage systems and, therefore, the requirement to restore twenty percent of the total impervious surface area in the urbanized area assigns