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Photo: Seattle Public Utilities

A popular concept among municipal separate storm sewer systems (MS4s) implementing stormwater regulations—as well as their regulators, the environmentally concerned, forward-thinking engineers, developers, and other stakeholders—is that stormwater runoff should be treated using natural practices or means that mimic natural practices, so that the natural hydrology of a developed site is maintained. This concept is often called low-impact development (LID), but it is also referred to under a newer, broader heading, green infrastructure. In the stormwater world these days, it is impossible to go far without running into these terms, whether in a discussion about how a city will implement LID concepts through a new ordinance or at a national conference on green infrastructure research.

LID is poised to become an even more ubiquitous term and to be implemented on a more-widespread basis. A decision in a Washington state lawsuit over National Pollutant Discharge Elimination System (NPDES) permit language illustrates the increasingly important role of LID. Issued in August 2008, the ruling concludes that the Washington “Phase I Permit must be modified to require the use of LID where feasible, as it is necessary to meet the MEP [maximum extent practicable] and AKART [all known and reasonable technology] standards of federal and state law, respectively” (PCHB 2008). The permit provision that was overturned by this decision simply encouraged LID. Because of the ruling, Phase I permittees in Washington will now require new developments to implement LID where feasible.

The Phase I ruling is the first decision that directly requires LID to be implemented through means of an NPDES permit. Many see the decision as an important event in the evolution of the NPDES permitting program. The country will watch as the decision is implemented, both as an example of how a mandatory LID program works and how several important matters left unresolved by the decision will be handled.

Another decision, affecting the Western Washington Phase II permit, was issued in February 2009. While it is less radical, it too will drive the implementation of LID in Washington.

A History of the Decisions
Washington State’s newest NPDES permits. The Washington Department of Ecology, the NPDES regulator for the state, issued the new Phase I and Phase II permits on January 17, 2007. The permits took effect on February 17, 2007. The Phase I permit covers the cities of Seattle and Tacoma, Clark County, King County, Pierce County, and Snohomish County, as well as a number of secondary permittees, including the Ports of Tacoma and Seattle. There are two Phase II permits, one for the eastern and one for the western part of the state.

The Environmental Hearings Office in Washington state is an “independent quasi-judicial state agency” housing several hearing boards: Pollution Control Hearings Board (PCHB), Shorelines Hearings Board, Forest Practices Appeals Board, Environmental and Land Use Hearings Board, and Hydraulic Appeals Board. The PCHB hears “appeals from decisions and orders made by” the Department of Ecology, local and regional air boards, and other agencies as specified by state law.

Immediately upon the issuance of the new permits, a variety of groups appealed them to the PCHB, including municipalities subject to the permits, environmental groups, and utilities. The appeals were consolidated into several cases, one of which concerned the issues associated with the Phase I permit.

One of these Phase I permit issues: Does the permit fail to require maximum onsite dispersion and infiltration of stormwater through the use of LID techniques, basin planning, and other appropriate technologies, and, if so, does that failure unlawfully cause or contribute to violations of water quality standards? And, if so, does that failure unlawfully allow permittees to discharge pollutants that have not been treated with all known AKART, and/or fail to reduce the discharge of pollutants to the MEP? The decisions issued on the Phase I and II appeals included the Board’s rulings on LID.

The Phase II permit issues were heard by the PCHB separately from the Phase I issues. Although the same LID issue was also raised for the Phase II permit, hearings on the Phase II issues were not concluded until October 2007. The Phase II ruling was issued February 2, 2009.

The Phase I Decision
As stated in the decision, “the Board concludes that the Phase I Permit fails to require that the municipalities control stormwater discharges to the maximum extent practicable, and does not require application of all known, available, and reasonable methods to prevent and control pollution, because it fails to require more extensive use of low-impact development techniques” (PCHB 2008). The board’s line of reasoning is woven over nearly 20 pages in the decision. Essentially, the board found, from evidence presented at the hearings, that LID is a “known and available technology” (ibid). That is, LID is a well-developed technology as evidenced through guidance, design standards, and other documents. In addition, the board found that LID is “technologically and economically feasible and capable of application at the site, parcel, and subdivision level at this time” (ibid). As an available and feasible technology, LID has become part of the techniques to control stormwater to the “maximum extent practicable,” according to the board (ibid).

In accordance with its findings, the board directed the Department of Ecology to make specific changes to some provisions in the permit, including its direction to Ecology “to require the permittees to develop methods for use of low-impact development at parcel and subdivision levels in their jurisdictions” (PCHB 2008). As stated earlier, the board concluded that the “Phase I Permit must be modified to require use of LID where feasible” (ibid).

At the “basin and watershed level,” the implementation of LID presents some feasibility challenges that the board did not feel could be overcome immediately. Therefore, the board directs the Department of Ecology to ready itself to require LID at the basin and watershed level in the future.

The Phase II Decision
The board’s decision on LID for Phase II communities applies to the Phase II permit for the western part of the state only. While resting on the findings of the Phase I decision concerning the availability and feasibility of LID, the recent decision draws a distinction between how quickly Phase I and Phase II communities will be required to implement LID, because Phase II communities vary widely in technical and financial resources. The decision “concludes that the current language of the Phase II permit, which requires adoption of ordinances or other enforceable mechanisms to allow for LID, is permissible, but requires Ecology to define in the Permit further steps to advance LID by the Phase II jurisdictions. The Board concludes that Ecology must modify the permit to require permittees to identify barriers to implementation of LID and identify actions taken to remove those barriers, to establish goals regarding the future use of LID, and to require other specific actions on reasonable and flexible time frames, both during this permit cycle and in anticipation of future permits” (PCHB 2009).

LID and Its Integration Into Stormwater Regulations
LID is defined in the Washington Phase I permit as “stormwater management and land development strategy applied at the parcel and subdivision scale that emphasizes conservation and use of onsite natural features integrated with engineered, small-scale hydrologic controls to more closely mimic pre-development hydrologic functions” (PCHB 2008). LID was pioneered in Prince George’s County, MD, in the 1990s (EPA 2000). Its goals and principles focus on protecting receiving waters through improved stormwater treatment technology and encouraging environmental stewardship through environmentally sensitive development (Prince George’s County 1999). The county’s LID manual describes practices and design elements to implement LID, such as reduced impervious surfaces, functional grading and open channel sections, disconnection of hydrologic flowpaths, bioretention/filtration landscape areas, microstorage, functional landscaping, increased runoff travel time, and so forth.

While local governments struggle with the implementation challenges that come with encouraging stormwater solutions that touch individual lots in subdivisions, more and more regulations and design standards encourage or require LID. The trend is found at the national, state, and local levels.

At the top of the NPDES permitting chain, the EPA is moving toward LID. The Washington decision itself notes that the EPA has not required LID, but is increasingly supporting it through publications, fact sheets, and its Web site (PCHB 2008). In addition, through its Green Infrastructure Initiative, the EPA is undertaking concrete steps to promote development that uses natural practices. The EPA signed an agreement in April 2007 to “promote green infrastructure as an environmentally preferable approach to stormwater management,” along with four other groups (EPA 2008). Early in 2008, the groups published their Action Strategy for Managing Wet Weather with Green Infrastructure, which outlines a comprehensive set of objectives and strategies to further research, acceptance, and implementation of green infrastructure. Among the objectives under the “Clean Water Act Regulatory Support” area is the objective: “Develop model permit language for MS4 permits that will specifically incorporate green infrastructure management practices into municipal stormwater programs. Conduct pilot tests of the model language in permits, as appropriate.” The model permit language is to focus “on processes of infiltration, reuse and evapotranspiration, and simultaneously consider both site design and community design/regional issues.” According to the strategy document, pilots are underway with the Tennessee and Virginia permit language. Because the EPA directs the NPDES program carried out at the state permitting and local level, the EPA’s focus on this manner of stormwater treatment is significant. The EPA’s direction will be felt at the state and local levels.

In other quarters, LID appears in manuals and regulations as either a mandatory or preferred approach. At the state level, Washington’s own manuals are just one example. The Puget Sound Action Team’s manual, published in 2005, is a “comprehensive, technical guidance manual for the use of LID in the Puget Sound area” (PCHB 2008). In Maryland, LID is the preferred stormwater management approach. Among local governments, the city of Salinas, CA, published its Development Standards Plan: LID Practices for Urban Storm Drainage Management, in 2005, in accordance with the California State Water Resources Control Board’s policy that sustainability be considered in all policies, guidelines, and regulations. And Warsaw, VA, requires LID as the standard stormwater management method. In the Washington state decision, the preponderance of guidance and technical information that is available, like the guidance mentioned here, was used as part of the board’s argument that LID is MEP (PCHB 2008).

The Definition of Maximum Extent Practicable
By specifying that the MEP standard is not met without a requirement for LID, the PCHB made an important impact upon the definition of MEP for stormwater. A guidance document on NPDES permit writing states, “MEP has not been defined by EPA, but is intended to be flexible to allow the development of site-specific permit conditions based on the best professional judgment of the permit writer” (Gentile et al. 2003). The MEP standard has been described as a “flexible technology-based standard” (Debo 2003).

Through this decision, LID makes the leap from its innovative roots to become standard stormwater management. If this kind of change becomes widespread, as the EPA’s path indicates it will, the response of regulators and the regulated community will be fascinating to watch. How will permitting and regulation change to focus on parcel-level treatment? What new methods for treating stormwater may emerge?

Unresolved Issues
Because the decision contains language that is yet to be interpreted, the implementation of the permit will also be of interest. For instance, one attorney pointed out that the definition of the term “where feasible” will have a significant impact upon the eventual LID standards in Phase I communities (Kray 2008).

The Phase II decision sheds some light upon how issues are being addressed. The Department of Ecology is working on defining detailed LID requirements and possibly a performance standard. Ecology is considering convening a workgroup that “would attempt to reach consensus on aspects of LID” (PCHB 2009). According to the decision, the details will be worked out in the next 12 to 24 months, nearing the end of the permit term.

The implementation of mandatory LID in the revised Phase I permit will pioneer the concept among NPDES permits. The country will watch with interest as the Department of Ecology, permittees, and stakeholders work through the details.