6th Edition

Stormwater C.3 Guidebook

CCCWP Management CommitteeFebruary 15, 2012

Brief Guidebook History Key Changes from 5th Edition Ongoing Issues Recommended Action

Topics

Edition

Date Major Changes

1st January 2005 Implemented new C.3 requirements with Low Impact Development approach

2nd March 2005 Incorporated design guidance for bioretention, other features and facilities;added O&M guidance

3rd October 2006 Implemented HMP requirementsIntroduced IMP Sizing Calculator

4th October 2008 Organized and Improved LID Design Guidance

January 2009October 2009

Soils, Planting, and Irrigation GuidanceAdded 2 additional IMPs

5th October 2010 Implemented MRP RequirementsAdded IMP Construction Checklist

December 2011 “C.3 Update” to implement amendment

Guidebook History

Special Projects Table 4-14 on Page 60 Narrative Analysis of Feasibility of LID on

Special Projects (Instructions are in Guidebook but need to reference these instructions in template)

Technical Criteria for non-LID Facilities (in preparation; to be posted to website)

6th Edition

Harvesting and Reuse Feasibility Screening Procedure on Page 40-42 Background on Page 17 Underdrain discharge located at top of gravel

layer unless infiltration must be prevented

6th Edition

Soils, Plants, and Irrigation Updated Appendix B Incorporates MRP “Attachment L”

6th Edition

Follows organization and content of guidance in Chapter 3

Annotated with explanations and prompts

Prompts Harvesting and Use Feasibility Calculations

Prompt for feasibility narrative to be added

Supports presentation of sizing calculations in Chapter 4

Substitute for, or check, results of IMP Sizing Calculator

Includes a project data summary to facilitate compilation of reports

Template

Hydrograph Modification Management Report and proposal due April 2013

a. Present model verification monitoring results demonstrating that the IMPs are sufficiently overdesigned and perform to meet the 0.1Q2 low flow design criteria; or

b. Present study results of Contra Costa County streams geology and other factors that support the low flow design criteria of 0.2Q2 as the limiting HMP design low flow; or

c. Propose redesigns of the IMPs to meet the low flow design criteria of 0.1Q2 to be implemented during the next permit term.

Awaiting news on Prop. 84 grant application Data will also be relevant re: infiltration

and evapotranspiration requirements

Ongoing Issues

Feasibility/Infeasibility of Infiltration, Evapotranspiration, and Harvesting/Reuse

Response to Water Board staff comments on BASMAA submittal is pending BASMAA Board approval

Report on implementation experience is due December 1, 2013

Documenting harvesting/reuse projects is important

Ongoing Issues

Approve the Stormwater C.3 Guidebook 6th Edition and direct staff to publish it and the template on the Program website.

Direct staff to prepare and publish a new 2-page “Stormwater C.3 Update” summarizing policy changes

Recommendations

Annual and “Special Projects”

Provision C.3 Reporting

CCCWP Management CommitteeFebruary 15, 2012

Provision C.3 Reporting—Annual and Special Projects

REPORTING REQUIREMENT TEMPLATE

MRP Attachment A (C.3.b.)

Table 3.1 (C.3.e.) Table 1 In Plan

Project Name and Address Project Name and Address

Application Date

Project Description Project Description

Site Total Area, Disturbed Site Total Acreage

New & Replaced Impervious

Pre/Post-Project Impervious

Density (DU/Acre and/or FAR)

Special Project Categories

LID Credits Available

Percent LID and Non-LID

Status of Project

Source Control Measures

Site Design Measures

Treatment Systems/Criteria LID & Non-LID Treatment Used

Feasibility of LID Treatment

O&M Mechanism

Alternative Compliance

Hydromodification Controls

Narrative discussion of onsite LID feasibility Infiltration, evapotranspiration, harvesting/reuse

per Stormwater C.3 Guidebook 6th Edition

Description of site and DMAs

Need for pavement where proposed

Why any landscaped areas can’t be bioretention

Narrative discussion of offsite LID feasibility Owner owns land in same watershed?

In-lieu program exists?

Technical Criteria for Non-LID Facilities Reference an existing certification program, or

Prepare our own minimum design criteria?

Special Projects Reporting