2.2 Site Design Considerations

To manage stormwater effectively and efficiently, site design for both construction and the post-development condition must be done in unison with the design and layout of the stormwater infrastructure. Efforts should be made, as required and encouraged by Kitsap County development codes, such as Titles 12, 16, and 17, to conserve natural areas, retain native vegetation, reduce impervious surfaces, and integrate stormwater controls into the existing site drainage patterns to the maximum extent feasible. With careful planning, these efforts will not only help achieve the minimum requirements contained in the Stormwater Code, but can also reduce impacts from development projects and reduce the costs of runoff treatment and flow control.

Before designing the site and stormwater infrastructure, consider the following:

• Stormwater:

  • Identify the approved point(s) of discharge and conveyance system flow path(s) based on both piped conveyance and natural topography.
  • Using LID/GSS principles, manage stormwater runoff (quantity and quality) as close to the point of origin as possible.
  • Minimize the use of conventional stormwater collection (catch basins) and piped conveyance infrastructure.
  • Use LID/GSS BMPs (e.g., dispersion, infiltration, and reuse) where feasible.
  • Fit development to the terrain to minimize land disturbance and loss of natural vegetation, especially mature coniferous forest.

• Landscaping:

  • Maintain and use natural drainage patterns.
  • Preserve natural features and resources, including trees.
  • Create a multifunctional landscape using hydrology as a framework for landscape design.
  • Confine and phase construction activities to minimize disturbed areas and minimize impacts to environmentally critical areas and their associated buffers.
  • Plant new trees in proximity to ground level impervious surfaces for on-site stormwater management and/or flow control credit.
  • Minimize or prevent compaction of and protect soils.
  • Amend landscape soils to promote infiltration.

• Impervious and Pervious Surfaces:

  • For sites with varied soil types, locate impervious areas over less permeable soil (e.g., till). Minimize development over more porous soils. Use porous soils by locating bioretention, permeable pavement, or other approved infiltration methods over them.
  • Cluster buildings together.
  • Minimize impervious surfaces (e.g., buildings, sidewalks, etc.).
  • Minimize pollution-generation hard surface (PGHS) (e.g., areas subject to vehicular use such as driveways and parking strips).
  • Minimize pollution-generating pervious surfaces (PGPS) (e.g., fertilized lawns, flower beds, etc.). Consider landscaping with native vegetation.