2021 Kitsap County Stormwater Design Manual
2021 Kitsap County
Stormwater Design Manual

1.4.3 Construction Stormwater Pollution Prevention Plan

All Construction SWPPPs for large projects that trigger Minimum Requirements #1 through #9 shall be prepared by and bear the stamp of a professional engineer, licensed in the State of Washington. The Construction SWPPP shall address the thirteen required elements per Volume II, Chapter 2.

Construction SWPPPs for small projects that trigger Minimum Requirements #1 through #5 only do not have to be prepared by an engineer unless the specific small project requires engineering. The Construction SWPPP shall address the thirteen required elements per Volume II, Chapter 2.

Plans submitted for review shall include the following narrative and plan elements described below, at a minimum.

1.4.3.1 Narrative

  1. Required elements – Describe how the Construction SWPPP addresses each of the 13 required elements. (See Volume II, Chapter 2) Include the type and location of BMPs used to satisfy the required element. If an element is not applicable to a project, provide a written justification for why it is not necessary.

  2. Project description – Describe the nature and purpose of the construction project. Include the total size of the area, any increase in existing impervious area; the total area expected to be disturbed by clearing, grading, excavation or other construction activities, including offsite borrow and fill areas; and the volumes of grading cut and fill that are proposed.

  3. Existing site conditions – Describe the existing topography, vegetation, and drainage. Include a description of any structures or development on the parcel including the area of existing impervious surfaces.

  4. Adjacent areas – Describe adjacent areas, including streams, lakes, wetlands, residential areas, and roads that might be affected by the construction project. Provide a description of the downstream drainage leading from the site to the receiving body of water.

  5. Critical areas – Describe areas on or adjacent to the site that are classified as critical areas per Title 19 KCC. Critical areas that receive runoff from the site shall be described up to 0.25 mile downstream, or for the distance required by the downstream analysis, whichever is greater. Describe special requirements for working near or within these areas.

  6. Soil – Describe the soil on the site, giving such information as soil names, mapping unit, and erodibility, settleability, permeability, depth, texture, and soil structure.

  7. Potential erosion problem areas – Describe areas on the site that have potential erosion problems. Include a completed Construction Site Sediment Transport Potential Worksheet (see Appendix E).

  8. Construction phasing – Describe the intended sequence and timing of construction activities.

  9. Construction schedule – Describe the construction schedule. If the schedule extends into the wet season, describe what activities will continue during the wet season and how the transport of sediment from the construction site to receiving waters will be prevented.

  10. Financial/ownership responsibilities – Describe ownership and obligations for the project. Include bond forms and other evidence of financial responsibility for environmental liabilities associated with construction.

  11. Engineering calculations – Attach any calculations made for the design of such items as sediment ponds, diversions, and waterways, as well as calculations for runoff and stormwater detention design (if applicable). Engineering calculations shall bear the signature and stamp of an engineer licensed in the state of Washington.

  12. CESCL – A responsible CESCL shall be identified in accordance with Volume II, Chapter 2.

  13. Contact Information – Telephone numbers and email addresses shall be included.

1.4.3.2 Plans

The Construction SWPPP shall follow the format requirements of site improvement plans (see 1.4.2 Site Improvement Plans) and shall contain the following information:

  • Basic site plan requirements – All information required per the basic site plan requirements.

  • Existing topography – Existing topography, as per the requirements for Full Drainage Review.

  • Finished grade

  • Phasing – If the site will be cleared in phases, each phase shall meet all requirements of this chapter. The phasing of any erosion and sedimentation control work shall be clearly indicated on the Plan.

  • CESCL – The name, address, and contact information of the designated erosion control lead as required in Volume II, Chapter 2.

  • Construction sequencing – A detailed listing of the construction sequence.

  • Soil types – The boundaries of and labels for different soil types.

  • Erosion areas – Areas of potential erosion problems.

  • Discharge locations – Locations where stormwater discharges to surface waters during and upon completion of construction.

  • Conveyance systems – Show on the site map the following temporary and permanent conveyance features:

    • Locations for swales, interceptor trenches, or ditches.

    • Drainage pipes, ditches, or cut-off trenches associated with erosion and sediment control and stormwater management.

    • Temporary and permanent pipe inverts and minimum slopes and cover.

    • Grades, dimensions, and direction of flow in all ditches and swales, culverts, and pipes.

    • Details for bypassing offsite runoff around disturbed areas.

    • Locations and outlets of any dewatering systems.

  • Location of flow control BMPs – Show on the site plans the locations of any Flow Control BMPs.

  • Erosion and Sediment Control (ESC) BMPs – Show on the site plans all structural and nonstructural ESC BMPs including:

    • The location of sediment pond(s), pipes and structures.

    • Dimension pond berm widths and inside and outside pond slopes.

    • The trap/pond storage required and the depth, length, and width dimensions.

    • Typical section views through pond and outlet structure.

    • Typical details of gravel cone and standpipe, and/or other filtering devices.

    • Stabilization technique details for inlets and outlets.

    • Control/restrictor device location and details.

    • Stabilization practices for berms, slopes, and disturbed areas.

    • Rock specifications, spacing, sections and detail for rock check dam, if used.

    • The location, detail, and specification for silt fence.

    • The construction entrance location and a detail.

  • Other pollutant BMPs – Indicate on the site map the location of BMPs to be used for the control of pollutants other than sediment (e.g., BMPs for commercial composting; refer to Volume II, Chapter 3).

  • Standard plan notes – Include standard plan notes per Appendix B.