S

Permitting Green Infrastructure

Katie Rousseau Associate Director, Clean Water Supply Program

2013 Healing Our Waters

Great Lakes Restoration Conference

Background

National Research Council (NRC) 2009 report “Urban Stormwater Management in the United States”

S  The stormwater permit program’s over-reliance on general permits, most of which contain vague, subjective, and unenforceable permit terms

S  The relative lack of permits that require stormwater management practices that will actually reduce runoff volume rather than simply convey or detain it

EPA’s Response

2010 MS4 Permit Improvement Guide

S  Objective performance standard that control volume and mimic pre-development hydrology

S  Explicit requirements for green infrastructure measures

S  Establishing limits or ceilings on the amount of impervious area

Permits need specific, objective language

Objective Performance Standards •  1” of rainfall

•  Runoff from a 2 year-24 hour storm event

•  85th percentile storm

Photo credit: Meliora Designs

California Phase II Permit

E.12.e(ii)(c) Numeric Sizing Criteria for Storm Water Retention and Treatment

The Permittees shall require facilities designed to evapotranspire, infiltrate, harvest/use, and biotreat storm water to meet at least one of the following hydraulic sizing design criteria:

(a)  Volumetric Criteria

(1)  The maximized capture storm water volume for the tributary area, on the basis of historical rainfall records, determined using the formula and volume capture coefficients in Urban Runoff Quality Management, (that is, approximately the 85th percentile 24-hour storm runoff event); or

(2)  The volume of annual runoff required to achieve 80% or more capture using local rainfall data.

California Phase II Permit

(b) Flow-based Criteria

(1) The flow of runoff produced from a rain event equal to at least 0.2 inches per hour intensity; or

(2) The flow of runoff from a rain event equal to at least 2 times the 85th percentile hourly rainfall intensity as determined from local rainfall records.

Boise, Idaho Draft Phase I Permit

B.2.a(i) The ordinance/regulatory mechanism must include site design standards for all new and redevelopment that require, in combination or alone, storm water management measures that keep and manage onsite the runoff generated from the first 0.6 inches of rainfall from a 24-hour event preceded by 48 hours of no measurable precipitation. Runoff volume reduction can be achieved by canopy interception, soil amendments, evapotranspiration, rainfall harvesting, engineered infiltration, extended filtration, and/or any combination of such practices that will capture the first 0.6 inches of rainfall.

Thank You

Katie Rousseau American Rivers

krousseau@americanrivers.org 419-936-3759

Permitting Green Infrastructure: A Guide to Improving Municipal Stormwater Permits and Protecting Water Quality by Jeff Odefey

(http://www.americanrivers.org/newsroom/resources/permitting-green-infrastructure-a-guide-to-improving-municipal-stormwater-permits-and-

protecting-water-quality/)

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