SSD-BMP Tool and Project Example

The County of San Diego has released a new tool for Significant Site Design BMPs (SSD-BMPs), such as Tree Wells and Dispersion Areas.

Site Design BMPs used, individually or in combination, to fully retain the volume required to satisfy pollutant control and hydromodification management, within a drainage management area, are classified as SSD-BMPs.

The tool includes an Introduction Tab, a Design Capture Volume (DCV) Tab, a Dispersion Areas Tab, and a Tree Wells Tab. To illustrate the use of the tool, an example project for a PDP SWQMP has been included. The SSD-BMP Tool and the example project can be found in the Development Resources website within www.sandiegocounty.gov/stormwater under “Calculators and Modeling Software”.

Upcoming Changes to the County BMP Design Manual and Future Virtual Public Information Session

The next update to the County BMP Design Manual will be posted in mid-September, and will include the following revisions:

• New Appendix I for SSD-BMPs Sizing Methods and Calculations, as well as other applicable Chapters and Appendices to reflect SSD-BMPs
• New Appendix C for Baseline BMP Fact Sheets for Site Design and Source Control, as well as applicable Chapters and Appendices to reflect Baseline BMPs. Tables 1 and 2 of the Standard and PDP SWQMP will also be updated to reflect the new Baseline BMP Fact Sheets.
• Miscellaneous edits for consistency between chapters and appendices

The 2020 County BMP Design Manual will be posted in the Development Resources website within www.sandiegocounty.gov/stormwater under “Manuals”. A virtual public information session highlighting the 2020 County BMP Design Manual to be held in late October will be announced soon.

Expiration date for projects with Prior Lawful Approval Exception

The use of the Prior Lawful Approval exception (also known as grandfathering) of stormwater development planning requirements under the 2007 Municipal Separate Storm Sewer System (MS4) Permit will be ending on February 16, 2021. Previously excepted PDP Projects may include multi-phased project with future grading permits or those that constructed on-lot Structural BMPs that will come back for a building permit. Under these scenarios, no additional permits (Grading, Building, etc.) will be issued under the 2007 MS4 Permit after February 16, 2021 and those projects will be required to comply with the BMP Design Manual. A sample letter describing more specifics can be found here.

Please contact your PDS Project Manager for more information and assistance in complying with these updated requirements.

SDHM 3.1 software update

SDHM 3.1 software was updated in April 2020 to include updates to bioretention elements and incorporate bug fixes. The County of San Diego will continue to accept submittals for all versions of SDHM 3.1 (original SDHM 3.1 dated 6/26/17 and updated SDHM 3.1 dated 4/7/20) until further notice.