United States: EPA Region III Issues Most Stringent MS4 Permit in the Nation to the District of Columbia

Amy L. Edwards is a partner and Tori B. Gordon an associate in our Washington, D.C. office

On October 5, 2011, the United States Environmental Protection Agency (EPA) Region III issued the long-awaited final Municipal Separate Storm Sewer System (MS4) Permit (DC0000221) ("Final Permit") for the District of Columbia. The latest version of the District's MS4 permit1 generated a lot of questions and concerns when first proposed in draft form in April 2010.2 The Final Permit is the most stringent MS4 permit in the nation and is likely to serve as a model for MS4 permits elsewhere. It imposes the following requirements:

  • a stringent on-site stormwater retention standard (1.2") for all new development and redevelopment disturbing 5,000 square feet or more of land
  • a requirement for an offset program involving off-site mitigation and/or a fee-in-lieu program
  • numeric requirements for retrofits
  • numeric requirements for tree plantings (over 4,000/year) and green roofs (350,000 square feet during the permit term)
  • enhanced site plan reviews, and increased inspection and monitoring requirements
  • operations and maintenance requirements
  • low impact development (LID) requirements

According to EPA, it is now using flow volume as the management parameter in its policies, with the goal of replicating pre-development hydrology.

EPA acknowledged in the fact sheet accompanying the Final Permit that implementation costs will be "significant" and stated that a dedicated source of funding (such as the District's impervious area fee) will be essential in ensuring compliance with the permit. EPA also acknowledged concerns expressed by the public about the need for flexibility through off-site mitigation and payment-in-lieu mechanisms, which is offered in the Final Permit. In addition, given EPA's statements about "staged implementation," it is clear that future iterations of the permit are likely to contain even more stringent requirements. This Final Permit provides the "foundation" for these future actions.

The Final Permit adopts a number of measureable performance standards for newly developed and redeveloped sites. EPA selected a numeric performance standard (retention of a 1.2" rainfall event on-site) because it established a clear and enforceable requirement. EPA also required the District to determine whether its codes and policies are consistent with the Final Permit, to have a verification process after construction and to track volume reductions from all projects. Compliance with all of the performance standards and provisions contained in the Final Permit will, according to EPA, constitute adequate progress toward compliance with the District's Water Quality Standards (WQS) and Waste Load Allocations (WLAs) under applicable Total Maximum Daily Loads (TMDLs), including the Chesapeake Bay TMDL.3

The Final Permit became effective on October 7, 2011.

Differences From the Draft Permit

The Final Permit maintains many of the stringent requirements found in the April 2010 Draft Permit. However, it also allows for greater flexibility by allowing the development of off-site mitigation plans and creating more opportunities for public notice and comment and EPA oversight.

Compliance Schedules and Deadlines

EPA made revisions to address comments regarding requirements in the Draft Permit that lacked clear compliance schedules or deadlines, or where the deadlines did not correspond well with others in the permit. In the Final Permit, EPA changed the requirement that deficiencies in legal authority be remedied "as soon as possible" to a 120-day requirement for deficiencies that can be addressed through regulation and two years for deficiencies that require legislative action (§ 2.1.1)). EPA also increased the compliance schedule for updating the District's stormwater regulations (21 DCMR 5, Water Quality and Pollution) from 12 months to 18 months. The District will have two years to develop a Consolidated TMDL Implementation Plan, which will become an enforceable part of the Final Permit
(§ 4.10.3). It must also develop a Revised Monitoring Program within two years
(§ 5.1).

Stormwater Management Program (SWMP) Plan

The Final Permit clarified that any written study, strategy, plan, schedule or other element, existing or new, will be part of the District Stormwater Management Plan (SWMP or Plan). To address accessibility concerns, EPA is requiring that the most current version of the Plan be posted on the District's website. Additionally, EPA is requiring that public notice of the fully updated Plan be provided within three years of the effective date of the Final Permit, and that the Plan be submitted to EPA within four years of the effective date of the Final Permit. These requirements will give both EPA and the public an opportunity to review program elements that will become major components of the SWMP.

Single Performance Retention Standard

The Draft Permit contained one retention standard for Federal facilities (1.7") and another for all other, non-federal facilities (1.2"). The Final Permit establishes a uniform performance standard of retention of a 1.2" rainfall event for all new development or redevelopment projects that disturb 5,000 square feet or more of land – regardless of who owns or operates the property (§ 4.1.1).4 This requirement will go into effect 18 months after the effective date of the Final Permit. The Final Permit exempts District transportation right-of-way projects from having to seek off-site mitigation or pay a fee-in-lieu (see paragraph below) if they cannot meet the 1.2" retention standard. It is important to note, however, that federal facilities must still comply with the 1.7" retention standard under the federal Energy Independence and Security Act (EISA). The District can track the performance of federal development projects and document those achieving greater than 1.2'' retention, but it will not be authorized to enforce the more stringent 1.7" retention standard under the EISA.

Off-Site Mitigation (Offset Program)

The Final Permit requires the District to develop an alternative means of compliance for new development and redevelopment projects that cannot meet the on-site 1.2" performance standard because of physical site conditions (e.g., tight soils or contamination) that preclude the use of extensive LID practices. Section 4.1.3 of the Final Permit, Off-Site Mitigation and/or Fee-in-Lieu for all Facilities, requires the District to establish a program for off-site mitigation and/or fee-in-lieu payment within 18 months of the Permit's effective date. The Final Permit provides the District the flexibility to develop a program with either one or both of those elements. Specifically, the Final Permit requires that the Off-Site Mitigation and/or Fee- in-Lieu Program include:

  • establishment of baseline requirements for on-site retention and for mitigation projects; on-site volume plus off-site volume must equal no less than 1.2''
  • specific criteria for determining when compliance with the baseline requirement for on-site retention cannot technically be met based on physical site constraints, or a rationale for why this is not necessary
  • for a fee-in-lieu program, establishment of a system or process to assign monetary values at least equivalent to the cost of implementation of controls to account for the difference in the performance standard, and the alternative reduced value calculated
  • the necessary tracking and accounting systems to implement this section, including policies and mechanisms to ensure and verify that the required stormwater practices on the original site and appropriate required off-site practices stay in place and are adequately maintained

EPA expects the District to explain these elements in its proposed implementation plan and EPA will be placing substantial emphasis on accountability measures.

Retrofit Program

EPA is requiring the District to include a retrofit element in its SWMP to address past undesirable stormwater management practices (§ 4.1.5). The District must develop performance metrics, but can allow variances from the performance standards that otherwise apply to new development. The performance metrics for retrofits will be subject to substantial scrutiny:

  • The Final Permit requires public notice of the proposed protocols to achieve the performance standards for retrofits, and those protocols must be submitted to EPA for review and approval within two years of the effective date.
  • The community will have the opportunity for input and an ability to shape the program.
  • The District must work with federal agencies to document federal commitments to retrofit their properties.
  • The District must make pollutant load and volume reduction estimates for all retrofit projects and for the Anacostia River, Rock Creek and Potomac River watersheds.

The Draft Permit provided that there would be 18 million square feet of retrofits, of which 3.6 million square feet would come from retrofitting impervious surfaces in transportation rights-of-way. The total square footage of retrofits remains unchanged (18 million square feet) in the Final Permit, but the percentage that comes from transportation rights-of-way has been reduced 60 percent, to 1.5 million square feet. This change could place a heavier burden on the private sector to achieve the Permit's retrofit requirements.

Finally, in perhaps one of the biggest surprises under the Final Permit, the District is required to adopt and implement stormwater retention requirements for properties where less than 5,000 square feet of land is being disturbed, but where the buildings or structures have a footprint that is greater than or equal to 5,000 square feet and the buildings or structures are undergoing substantial improvement as defined by 12J DCMR § 202. Substantial improvement is defined as any repair, alteration, addition or improvement that equals or exceeds 50 percent of the market value of the structure before the improvement or repair. EPA's goal is to promote retrofits on smaller sites.

Monitoring Program

The District must submit its Revised Monitoring Program to EPA for review and approval within two years of the effective date (§ 5). EPA has reduced the number of pollutant analytes which must be monitored from 120 to 9 (E. coli, total nitrogen, total phosphorus, total suspended solids, cadmium, copper, lead, zinc and trash). This change should be helpful to property owners who need to obtain a permit to discharge into the MS4 system. In the past, the District Department of the Environment has been known to require months of sampling for hundreds of analytes before it will grant the water quality certification needed in order to obtain an EPA permit. The shorter list of pollutants that must be monitored under the Final Permit should keep all parties focused on the true pollutants of concern.

Increased Oversight and Communication

The Final Permit includes construction site inspection frequency requirements to ensure compliance with the District's erosion and sediment control regulations. EPA revised this section to require more rigorous oversight of construction stormwater controls. The Final Permit imposes reporting requirements that are designed to efficiently increase and improve communication between EPA Region III and the District. The District will now be able to submit monitoring data through NetDMR, a national tool for regulated Clean Water Act permittees, allowing them to submit discharge monitoring reports electronically to EPA via a secure Internet application (§ 6). The District will also be required to post each Annual Report on its website at the same time that the report is submitted to EPA.

Implications for the Development Community and Next Steps

Building owners are now in the cross hairs of the LID movement. The Final Permit is the foundation for this movement and the EPA and the environmental community will be pressing for more when this Permit expires in five years. Property owners can no longer afford to be complacent but must become actively engaged in the stormwater rulemakings that will occur over the next 12 to 18 months. Stormwater controls will be costly, therefore those costs must be factored into project costs.

Property owners will need to persuade the District and EPA that the 1.2" retention standard frequently cannot be met on-site and help the District shape cost-effective alternatives. Environmentalists are not yet convinced that the on-site retention standards cannot be attained, so they will be pressing for rigorous tests before a property owner can qualify for off-site mitigation or a fee-in-lieu payment. In addition, property owners need to be aware that retrofits may be required on smaller projects where the value of the improvements is increased by 50 percent or more. Site plan reviews, inspections and enforcement of stormwater controls during construction will become more vigorous. Long-term maintenance of stormwater controls will also become an issue. And, if the Chesapeake Bay TMDL is re-opened during the Permit term, the Permit can be re-opened to require even more rigorous stormwater controls (§ 8.19). The development community needs to be prepared to engage in this long-term battle over LID and stormwater controls in the built environment.


1 The District's first MS4 permit was issued in 2000 and a second permit was issued in 2004. A Modified Letter of Agreement was negotiated in 2008. There have been 10 years of legal challenges and negotiations associated with these permits. The Final Permit replaces the 2004 permit.

2 The Draft Permit is discussed in our May 21, 2010 Environment Alert.

3 EPA used the information in the District's final Phase I Watershed Implementation Plan (WIP) in establishing the Chesapeake Bay TMDL and expects the District to comply with the WLAs used in the WIP.

4 In other words, stormwater management facilities must be designed, constructed and maintained in order to prevent stormwater runoff from all rainfall events equal to or less than the 90th percentile rainfall event.


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