Western Washington Phase II Stormwater Manuals
Program options for Western WA Phase II Municipal Stormwater Permittees using “equivalent manuals.”
The Phase I Municipal Stormwater Permit (special condition S5.C.5.a) and the Western Washington Phase II Municipal Stormwater Permit (WWA Phase II Permit) (special condition S5.C.4.a) require permitted cities and counties to establish enforceable programs to manage stormwater from new development, redevelopment, and construction activities. There are two parts to the enforceable program requirement.
The first part of the program must describe the minimum technical requirements, thresholds,
definitions, adjustments, and variance criteria to be used for new development, redevelopment,
and construction sites. From S5.C.4.a.i of the WWA Phase II Permit, an ordinance or other
enforceable mechanism must include:
Both permits contain an identical Appendix 1, including a basin planning option (Section 7), which Permittees may use (with Ecology’s approval) to tailor certain minimum requirements or demonstrate an equivalent level of protection through the use of regional facilities.
The second part of the program requirement included in both permits is the implementation
of site planning requirements; BMP selection, design, and infeasibility criteria;
BMP limitations; as well as LID competing needs criteria. These components work together
to protect water quality, reduce the discharge of pollutants to the Maximum Extent
Practicable (MEP) and satisfy Washington State requirements for applying AKART.
From S5.C.4.a.ii of the WWA Phase II Permit:
The primary distinction between the two permits is that Phase I permittees must submit their draft enforceable requirements, technical standards and manuals to the Department of Ecology (Ecology) for review and approval, whereas Phase II Permittees are not given the option to do so. The Phase I process is generally referred to as an “equivalency review.” During this review, Ecology evaluates each Phase I program for its functional equivalency to the requirements described in Appendix 1 and the relevant portions of Ecology’s Stormwater Management Manual for Western Washington (SWMMWW). Ecology does not have the capacity to review Phase II programs in detail, and thus relies on the Phase II Permit and Appendix 1 to ensure the minimum requirements; thresholds and definitions are consistently applied to projects in Phase II coverage areas.
Western WA Phase II cities and counties essentially have three compliance pathways for implementing the relevant requirements of S5.C.4.a.i:
Special Condition S5.C.4.a.ii requires Permittees to develop site planning requirements, BMP selection, design and infeasibility criteria, BMP limitations, and LID competing needs criteria (see S5.C.4.a.ii.(a)-(f)) that when used to implement the minimum technical requirements of Appendix 1, protect water quality, reduce the discharge of pollutants to the MEP, and satisfy AKART prior to discharge. Permittees must document that their programs meet these objectives through one of the following compliance pathways:
Combining Different Manuals
It is important to keep in mind that a Phase II Permittee may only establish alternative requirements to the minimum technical requirements, thresholds, and definitions contained in Appendix 1 (S5.c.4.a.i) through adoption of an Ecology-approved basin plan (Section 7 of Appendix 1) or through the adoption of a single Ecology-approved Phase I program. Some Phase II Permittees have expressed interest in selecting specific components of several different Phase I equivalent programs and/or the SWMMWW, and combining these requirements into a unique local program.
Ecology expects that Phase II Permittees adopting an Ecology-approved Phase I program for S5.C.4.a.i requirements (i.e., in lieu of Appendix 1) are also adopting the associated site planning requirements, BMP selection, design, infeasibility criteria and limitations, and LID competing needs criteria (S5.C.4.a.ii) from that same Ecology-approved Phase I program. If a Phase I program has received Ecology’s approval for alternatives to the minimum technical requirements, thresholds, definitions, adjustment and variance criteria in Appendix 1, such alternatives are only appropriate when implemented with the requirements, limitations and criteria addressing S5.C.4.a.ii.(a)-(f) that are part of that Ecology-approved program, and any additional conditions that Ecology places on such an approval.
If a Phase II Permittee chooses to select different BMP limitations or criteria, or site planning requirements (S5.C.4.a.ii.(a)-(f)) from several different Phase I programs, the onus is on the Permittee to document how this composite manual meets the permit requirements as described above. This approach is essentially a version of the third compliance pathway listed above for S5.C.4.a.ii. In this case, a Permittee cannot rely on Ecology’s determination of equivalency associated with the Phase I programs because Ecology’s equivalency determination is based on a review of the individual Phase I program as a whole.
It is incorrect to assume that individual elements of approved equivalent Phase I programs can be isolated, recombined, and still be equivalent to Appendix 1 and the SWMMWW. Permittees are cautioned that this practice may create potential liability. (Furthermore, it may be inappropriate to adopt a Phase I program designed to address specific general conditions in a Phase I community [e.g., highly urbanized, fully built-out city] in a jurisdictions with significantly different characteristics [large-lot suburbs at the fringe of an urbanized area].) A few examples of how this may happen are listed below.
Without Ecology’s approval and an associated determination of equivalency of a local code and manual, the local jurisdiction must rely on its own justification and documentation that the local program meets the permit requirements. Ecology, EPA, or a third party may review such documentation to evaluate compliance with the permit.
Ecology encourages any Permittee who is considering using some element(s) of an Ecology-approved equivalent Phase I program to review the comments and resolution documentation associated with that Phase I program review. These materials will be available on the Phase I equivalent manual page when they are completed. Note that a Phase I program is not considered “equivalent” until after Ecology has modified the Phase I permit (Appendix 10) following public review and comment. Ecology may consider the program “approvable” until such time as the permit modification is completed and the determination of “equivalent” can be made.
Washington Department of Transportation’s Highway Runoff Manual (HRM)
Ecology has determined the HRM to be equivalent to both of Ecology’s western and eastern Stormwater Management Manuals for minimum design requirements and best management practices for public road projects. Permittees may adopt and employ these equivalent sections (only) for use within their jurisdictions. It should be noted that there are additional provisions (or exemptions) in the HRM that apply only to WSDOT and are not appropriate for local governments to follow and implement. The HRM was revised and updated on March 6, 2014; the conditions of equivalency for the HRM will be described in the Phase I Municipal Stormwater Permit, Appendix 10, and on the website cited above.
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