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Recent Developments in Stormwater Regulation Pose a Threat to Development Industry

By: Mary Lynn K. Coffee

Two recent developments in municipal stormwater regulation in Southern California have the potential to significantly impact the development industry throughout the State. 


First, on December 13, 2006 the San Diego Regional Water Quality Control Board issued a revised tentative order for the San Diego County Public Storm Drain Permit ("Tentative Order") which contains provisions requiring the use of Low Impact Development BMPs ("LID") at sites subject to SUSMP requirements (within three years of adoption of the Tentative Order all sites that are greater than one-acre will be subject to SUSMP requirements).  When adopted, the Tentative Order will be a model for future public storm drain permits (MS4 Permits) throughout the State, and will contain precedent setting provisions that substantially affect development and redevelopment, including small site infill development.  Potentially precedent setting provisions of the Tentative Order include the LID requirements noted above, and other provisions such as infiltration and/or volume reduction requirements, commonly referred to as "hydromodification management" (which also will apply to all sites greater than one-acre within three years), and advanced treatment requirements for construction sites greater than one-acre.


Second, on December 15, 2006 the Los Angeles Regional Board staff, without Board review or consideration, issued a letter "clarifying" provisions of the existing Los Angeles County MS4 Permit and finding that local agency planning and public works departments are not adequately implementing the MS4 Permit requirements.  The "clarifications" essentially result in additional stormwater quality mitigation requirements.


According to this letter of "clarification," the Los Angeles Regional Board staff finds, among other deficiencies, that the co-permittees have inadequately implemented the MS4 Permit provision requiring flow controls and minimization of the volume of stormwater runoff directed to the public storm drain systems.  The staff bases its finding of deficiency on the local agencies' failure to mandate compliance of Priority Development and Redevelopment Projects.1  Several new interpretations of the general requirements to control flow and minimize runoff volume are as follows:


1) Co-permittees must require projects to minimize their effective impervious area to 5% or less of the total project area;


2) Co-permittees must require implementation of low impact development strategies that preserve natural features, and incorporate small scale volume reduction (hydrologic control/infiltration) technologies; and


3) Co-permittees must require implementation of a flow duration control standard such that post-construction discharge rates and durations of flow match the ranges from 10% of the pre-development, 2-year 24 hour peak flow up to the pre-development 10-year 24 hour peak flow, unless an alternative criteria is demonstrated to be equally effective through hydrodynamic modeling.


These "clarifications" have the potential to significantly impact the development of projects within the Los Angeles Region, and are likely to be used as a model for interpretation of other general provisions of MS4 Permits throughout the State, including the San Diego Regional Board's Tentative Order. 


The Los Angeles Regional Board's "clarification" of standards and requirements for new development and significant redevelopment projects, including standards for hydromodification management, LID development, site design BMPs, and environmental review of BMPs, combined with similarly restrictive provisions in the current draft of the San Diego Regional Board's Tentative Order with respect to the San Diego County MS4 Permit create substantial new conditions not just for greenfield development, but also to infill, affordable housing, and redevelopment of relatively small project sites.  Although these developments directly affect the Los Angeles and San Diego Regions, the standards and requirements of these two regulatory documents are likely to affect the development industry throughout the State because in other regions of the State, both the San Diego County MS4 Permit and the Los Angeles Regional Board clarification letter are precedents that put pressure on other Regional Boards to amend their MS4 permits substantially when those permits come up for renewal.  Further, the Advanced Treatment provisions of the San Diego County MS4 Permit will put pressure on the State Water Resources Control Board to follow a similar approach when renewing the statewide General Construction Permit.


The San Diego Regional Board is scheduled to consider the Tentative Order on January 24, 2007 at 9:00 a.m.


Mary Lynn K. Coffee is a partner in Nossaman's Irvine office.  She has extensive experience in compliance with, and permitting and approvals for development projects under local, state and federal resource protection laws, including the federal Clean Water Act (Sections 401, 402 and 404), the California Porter-Cologne Water Quality Act and the state streambed alteration provisions of the California Fish and Game Code.  In this role, she has particular expertise in the development of construction and post-construction surface water quality compliance programs for existing and new real estate developments.  She can be reached at (949) 833-7800 or


Priority Projects include: single family hillside residential developments of one acre or more; new development projects adding 10 or more units, 100,000 or more square feet of industrial/commercial space, or parking lots of 5,000 or more square feet; and redevelopment projects that result in land disturbing activity creating, adding or replacing 5,000 square feet or more of impervious surface on an already developed site.

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