LID treatment measures are harvesting and re-use, infiltration, evapotranspiration, or biotreatment. Require each Regulated Project to treat 100% of the amount of runoff identified in Provision C.3.d for the Regulated Project’s drainage area with LID treatment measures onsite or with LID treatment measures at a joint stormwater treatment facility. A properly engineered and maintained biotreatment system may be considered only if it is infeasible to implement harvesting and re-use, infiltration, or evapotranspiration at a project site. Conditions which may result in infeasibility to implement LID treatment measures are detailed in Provision C.3.c.

NPDES Provision C.3 Forms, Checklists & Worksheets
Infiltration Feasibility Worksheet Required for C.3 Regulated Projects with onsite soils suitable for infiltration.
Rainwater Harvesting and Use Feasibility Worksheet Required for C.3 Regulated Projects with non-potable water demand that exceeds the screening thresholds in the Project Applicant Stormwater Checklist.
Special Projects Worksheet Required for transit oriented, high density, and/or infill projects that may meet the MRP criteria for Special Projects.
Hydromodification Management Appicability Form The HM applicability form should be completed by municipal staff for projects that create and/or replace 43,560 sq. ft. or more of impervious surface, in order to determine whether the HM requirements apply.
Guidance Documents
C.3 Stormwater Technical Guidance The Handbook for developers, builders, and project sponsors regarding post-construction stormwater controls for regulated projects, in order to meet local municipal requirements.
Stormwater Review Process Flowchart Flowchart prepared by Regional Stormwater Program outlining the process of determining treatment requirements for C.3 regulated projects.
Flow Chart of County NPDES Review (County of San Mateo only) Flowchart outlining permitting process for Regulated Projects for projects located in the Unincorporated areas of San Mateo County.
Operation & Maintenance Documents
Operation & Maintenance (O&M) Template Agreement (County of San Mateo only) Applicant shall customize Template Agreement (using tracked changes) for County review and execution prior to final of the building permit for a Regulated Project.
Other NPDES Forms, Checklists & Worksheets
Stormwater Treatment Measure Maintenance Plan Templates The O&M Agreement template requires the applicant to attach Maintenance Plan Template(s) for the appropriate Stormwater Treatment Measure. A variety of Maintenance Plan Template(s) are available in Appendix G of the C.3. Technical Guidance (link as provided).