Storm Water Mitigation Plan

Bioretention facilities are engineered landscape features that provide storm water treatment and mitigate runoff impacts to the downstream habitat.Municipal Permit regulations make it necessary for projects to demonstrate compliance with storm water mitigation requirements prior to project approval or issuance of local permits.  Requirements that apply during the planning phase and prior to project entitlement include minimum standards for the implementation of Low Impact Development (LID) practices and the integration of flow control criteria designed to mitigate storm runoff peaks and durations from development sites. This unified LID approach combines site planning and design measures coupled with engineered, Integrated Management Practices (IMPs), such as bioretention facilities, flow-through planters, dry wells, infiltration basins, and cisterns.

Project applicants are encouraged to coordinate with City Storm Water staff to enable the development a plausible storm water mitigation concept, prior to development and plan submittal.

SUSMP Compliance Process at a Glance

Projects may elect to use the appropriate City Storm Water Mitigation Plan (SWMP) Template  (1.73 MB) as an aid to plan preparation.  In addition, it is suggested the project applicant consult with City Storm Water staff for assistance during each phase of development.   By implementing the unified LID design procedure, projects may develop a single integrated design that demonstrates compliance with Federal, State, and Local storm water regulations.

  • Projects Not Subject to SUSMP Treatment Requirements
  • Standard Development Projects (SDPs)
  • Priority Development Projects (PDPs)
  • SWMP Review Process
  • SWMP Amendment Process

Projects Not Subject to SUSMP Treatment Requirements (Exempt Projects)         

The Municipal Permit provides for limited exclusions from SUSMP Treatment requirements. To qualify, applicants are required to submit a completed Storm Water Quality Assessment form and receive a formal SUSMP Determination indicating the project is not subject to SUSMP Treatment requirements. Determinations are performed on a case-by-case basis.

Projects eligible for a SUSMP exemption may include:

  • Projects not identified as Priority or Standard Development Projects
  • Projects limited to interior remodels, routine maintenance or repair, roof or exterior surface replacement
  • Resurfacing and restriping of surface parking lots
  • Resurfacing of existing roadways
  • Construction of new sidewalk, pedestrian ramps, or bike lanes on existing roads
  • Routine replacement of damaged pavement, such as pothole repair or from pot-holing operations
  • Construction involving limited, or no soil disturbance and deemed not to be a threat to water quality (e.g. addition of cellular antennas/equipment to existing structures and etc.)

Projects that are determined to be exempt from SUSMP Treatment requirements remain obligated to satisfy the Requirements for All Development Projects which include, the implementation of appropriate Source Control BMPs, temporary construction BMPs, and permanent stabilization/erosion control BMPs.

Standard Development Projects (SDPs)   

Development and redevelopment projects that are not identified as Priority Development Projects, or are not determined to be exempt from SUSMP Treatment requirements, and receive a formal SUSMP Determination which identifies the project as a Standard Development Project‖ (SDP) shall address the following:

  • Implementation of Source Control BMPs as identified in Section 2 of the City SUSMP
  • Inclusion of LID features that:
    • Conserve natural topographic features
    • Provide development setbacks from natural water bodies and conveyances
    • Minimize site imperviousness
    • Maximize infiltration
    • Retain and slow runoff

Standard Development Projects are required to implement a Standard Development Project (SDP) – Storm Water Mitigation Plan (SWMP).  The City may also require additional controls for Standard Development Projects, that are appropriate to the project and which may include treatment BMPs and LID IMPs such as infiltration or bioretention.  Should treatment facilities be included in the project design, the plan shall contain provisions to ensure long-term BMP maintenance.

Priority Development Projects (PDPs)                                                                             

Development and redevelopment projects that are identified as Priority Development Projects and receive a formal SUSMP Determination identifying the project as a Priority Development Project‖ (SDP) shall address the following:

  • Implementation of Source Control BMPs as identified in Section 2 of the City SUSMP
  • Inclusion of LID features that:
    • Conserve natural topographic features
    • Provide development setbacks from natural water bodies and conveyances
    • Minimize site imperviousness
    • Maximize infiltration
    • Retain and slow runoff
    • Demonstrate conformance with storm water treatment/IMP requirements
    • Demonstrate conformance with storm water treatment flow attenuation (HMP) requirements
    • Identification of an acceptable long term Operation and Maintenance mechanism

Priority Development Projects are required to implement a Priority Development Project – Storm Water Mitigation Plan (PDP-SWMP).  The RWQCB and the City Engineer will not consider Treatment Control BMPs or Integrated Management Practices (IMPs) as being consistent with the Maximum Extent Practicable standard (MEP), unless the applicant identifies and a specific maintenance mechanism and implements a storm water operation and maintenance plan (O&M Plan) to ensure ongoing long-term inspection and maintenance of all Treatment Control BMPs and IMPs.

Storm Water Mitigation Plan (SWMP) Review Process

Projects which have been formally identified as Priority Development or Standard Development Projects are required to submit a project specific Storm Water Mitigation Plan (SWMP).  Project storm water plans and supporting documents shall be submitted to the Planning Division as part of the project entitlement process, for distribution to Engineering and Storm Water Development Review staff.

The review of project SWMP is an iterative process that entails examination of the SWMP for consistency with SUSMP and Municipal Permit requirements. SWMP reviews also comprise an evaluation the supporting documents that include (at a minimum); the Site Development Plan, Project Description and Justification, Hydrology Study, Geotechnical Report, Biological Study, Slope Analysis, and etc. The general steps to approval of the SWMP from initial submittal to signature approval are as follows:

  • Initial project submittal and formal SUSMP Determination
  • Subsequent submittals – iterative review and revision cycle accompanied by written and redline review comments
  • Issuance of deemed complete status – facilitates approval for administrative projects and enables scheduling of the Public hearing for discretionary projects
  • Public hearing – obtain tentative project entitlement upon Planning Commission approval
  • 10-day entitlement appeal period – the project findings may be appealed to a City Council hearing
  •  City Council hearing (if applicable)
  • Receipt of final entitlement by approved Conditions of Approval
  • Submission of Request for Signature Approval by Storm Water Development Review Staff
  • Final review by the City Development Engineer
  • Final review by the City Engineer
  • Signature approval by City Engineer

The City recognizes project entitlement as “lawful prior approval”.  However, “updated SUSMP and hydromodification requirements shall apply to all priority projects or phases of priority projects which have not yet begun grading or construction activities at the time any updated SUSMP or hydromodification requirement commences.  If a Copermittee determines that lawful prior approval of a project exists, whereby application of an updated SUSMP or hydromodification requirement to the project is infeasible, the updated SUSMP or hydromodification requirement need not apply to the project. Where feasible, the Copermittees shall utilize the SUSMP and hydromodification update periods to ensure that projects undergoing approval processes include application of the updated SUSMP and hydromodification requirements in their plans.”`

Storm Water Mitigation Plan (SWMP) Amendment Process                                      

Changes to an approved due to unforeseen field conditions and site constraints may be formally Amended, provided the amendment is consistent with previously approved SWMP and proposed Treatment Control BMP and/or IMP practices have an equal or greater pollutant removal efficiency for the project Primary Pollutants of Concern.  Amendments to an approved SWMP are required to provide narrative and exhibits that provide the following information:

  1. Title page indicating project name, permit application number (e.g. D-1-01), Amendment No., Engineer of work contact information, stamp, and wet signature
  2. Table of contents
    •  Project Background
    • Proposed Amendment
    •  List of Revised Sections, Figures, Exhibits, or Maps
    • Revised Narrative Sections
    • Revised Figures, Exhibits, or Maps
    • Conclusion
  3. Topics addressed in the Table of Contents will contain the following site specific information:
    • Project Background
      •  Recap/brief site description
      • Original SWMP approval date
      • Description of approved BMPs that will be affected by the proposed Amendment
    • Proposed Amendment
      • State purpose(s) for amending the approved SWMP
      • Provide supporting statements for each revision.  Demonstrate/state how revised practices  will provide equal or better treatment as compared to BMPs in the previously approved SWMP.
    • List of Revise Section
      • List text sections, figures, exhibits, or maps affected by the Amendment
    • Revised Text Sections
      • Apply underline font to revised text
      • Apply strikeout font to original text undergoing revision
      • Provide separate page(s) with a header for each revised text section
    • Revised Figures, Exhibits, or Maps
      • BMP Map or Exhibit in 24”x 36” (D-sheet) format with map pocket – legible scale – “cloud” and label revisions (i.e. SWMP Amendment No._) – BMP Maps will not be accepted in smaller formats
      • Provide title block information in lower left-hand corner of Map
      • Identify all legend items.  Graphic legend items must match scale, line type, and line weight, and shade of items depicted on map
      •  “cloud” and label revisions on remaining figures and etc.
    • Conclusion
      • Provide summary of changes, justification, demonstration of equal or better treatment capability, and meeting MEP standard

Submit SWMP Amendment to Development Services – Engineering Division.  Amendments are subject to an iterative review/revision process prior to approval by the City Engineer.