The County of Santa Clara - SCC Public Portal

SEARCH SCCgov

AGENCIES & DEPTS

SANTA CLARA COUNTY CODE OF ORDINANCES: Sec. B11 1/2-17. Permanent storm water pollution prevention measures required for certain development projects located within the San Francisco Bay Watershed.

Copyrighted by SANTA CLARA COUNTY CODE & Municipal Code Corporation, 1998.

Previous heading / Next heading / Table of Contents

__________

Sec. B11 1/2-17. Permanent storm water pollution prevention measures required for certain development projects located within the San Francisco Bay Watershed.

A. Site Design and Source Control BMP Requirements. The projects shall include, where practicable as determined by the Development Services Office, appropriate site design and source control BMPs in order to reduce the water quality impacts of storm water runoff from the site, for the life of the project.

B. Requirements and Effective Dates for Storm Water Treatment BMPs.

1. In addition to site design and source control BMPs, Group 1, Group 2A, and Group 2B project applicants are required to design and implement permanent storm water treatment measures sufficient to reduce the water quality impacts of storm water runoff from the site for the life of the project.

2. Any Group 1 defined project for which a land use application to the County was deemed complete by the Planning Office prior to October 15, 2003, is not required to implement storm water treatment measures.

3. Any Group 2A defined project for which an application to the County was deemed complete by the Planning Office prior to October 20, 2005 is not required to implement storm water treatment measures. Group 2A is superseded by Group 2B effective August 15, 2006.

4. Any Group 2B defined project for which an application to the County was deemed complete by the Planning Office prior to August 15, 2006 is not required to implement storm water treatment measures.

5. When a project application or building permit has expired, even when previously deemed complete, any re-application or new application must conform to the provisions of this ordinance that are in effect at the time of re-application. This section shall not apply to applications that are extended under the provisions of a county ordinance, prior to the land use application expiration date.

C. Hydromodification Management Plan (HMP) BMP Requirements and Exemptions.

1. In accordance with the County's NPDES Municipal Storm water Discharge Permit, all Group 1 Projects are required to implement permanent Hydromodification Management BMPs, except for the following projects:

a. Projects that do not create an increase in impervious surface over pre-project conditions.

b. Transit-oriented developments located within a one-half mile radius of existing or planned transit stations and/or major transfer points.

c. Projects located in sub-watershed areas that are 90 percent or more built-out relative to zoning and have more than 65 percent impervious surface. (Please see red colored area on HMP Map, on file with the Developments Services Office.)

d. Projects that are less than 50 acres in total project size that are located in sub-watershed areas that are 90 percent or more built-out relative to zoning and have less than 65 percent impervious surface. (Please see yellow colored area on HMP Map, on file with the Developments Services Office.)

e. Projects located within areas that drain to stream channels within the tidally influenced area, projects located within areas that drain to non-earthen stream channels that are hardened on three sides and extend continuously upstream from the tidally influenced area, and projects draining to an underground storm drain that discharges directly to San Francisco Bay. (Please see purple colored area on HMP Map, on file with the Developments Services Office.)

f. Projects that demonstrate, through stream-specific modeling studies consistent with the HMP that there will be no increase in erosion potential or other adverse impact to the beneficial uses to any waters of the State of California.

2. HMP projects that are located on sites less than or equal to 20 acres in size (small site projects) that are not part of a larger phased development shall comply with the HMP requirements through the use of appropriate site design, source control, and treatment control measures with flow control benefits to the maximum extent practicable. In addition, where available, off-site and/or in-stream controls should be considered in meeting the management standard.

To demonstrate compliance with the maximum extent practicable criterion, small site projects may use small-scale, distributed storm water management techniques such as bio-retention facilities, infiltration trenches, filter strips, vegetated swales, and multi-functional landscape areas to achieve treatment and flow reduction. Runoff volume reduction and time of concentrations for small-scale facilities can be computed using a discrete storm event approach until other simplified tools based on continuous simulation modeling are available for sizing flow control BMPs. Small site projects may demonstrate that this performance criterion is being met by matching pre- and post-project runoff volume and time of concentration (based on the two- and ten-year storms) to the maximum extent practicable.

3. Determination of impracticability. Meeting the HMP requirements will be considered impracticable if the combined construction cost of both required storm water treatment and hydromodification management BMPs exceeds two percent of the project construction cost, excluding land costs, soil disposal fees, hauling, contaminated soil testing, mitigation, disposal, or other normal site enhancement costs such as landscaping or grading that are required for other development purposes.

If a developer demonstrates that the total cost to fully comply with the HMP and other storm water treatment requirements will exceed this cost threshold, a determination may be made by Manager of the Development Services Office or designee that the project shall comply with the HMP requirements by either (1) implementing hydromodification management controls on-site to the maximum extent practicable, or (2) by contributing to an in-stream or off-site solution, if available, up to a maximum cost for all controls of two percent of the project cost. (The in-stream or off-site solution may be located within another jurisdiction or on land controlled by the Santa Clara Valley Water District.)

D. Group 1, Group 2A, and Group 2B projects that result in an increase of, or replacement of, more than 50 percent of the impervious surface of a previously existing development shall include permanent BMPs sufficient to reduce water quality impacts of storm water runoff from the entire site for the life of the project. These permanent BMPs should include site design, source control, storm water treatment measures, and if applicable, hydromodification management measures.

E. Group 1, Group 2A, and Group 2B projects that result in an increase of, or replacement of fifty (50) percent or less of the impervious surface of a previously existing development shall include permanent BMPs sufficient to reduce water quality impacts to storm water runoff from the increased or replaced portion of the site, for the life of the project. These permanent BMPs should include site design, source control, storm water treatment measures, and if applicable, hydromodification management measures.

(Ord. No. NS-517.74, § 1, 10-17-06)