Sammamish Unified Development Code

Environment & Sustainability | Low Impact Development

21.03.030 Low Impact Development A. Intent and goals

B. Applicability

All new development subject to drainage review shall be required to comply with the adopted Surface Water Design Manual (SWDM). The SWDM requires low impact development (LID) flow control best management practices (BMPs) to mitigate the impacts of storm and surface water runoff generated by new impervious surfaces, new pervious surfaces, existing impervious surfaces, and replaced impervious surfaces. In addition to the use of these required BMPs, new development may also have the option to incorporate LID site planning approaches described in SDC 21.03.030C. into project design in order to accumulate sufficient technique points to allow the applicant to take advantage of the incentives identified in SDC 21.03.030.D. The City of Sammamish shall apply this chapter to all City projects and encourage other governmental entities to utilize LID in accordance with this chapter in their projects.

Low impact development (LID) is an approach to land use planning and project design that seeks to: 1. Increase the ability of a developed site to effectively emulate predevelopment hydrologic conditions, including without limitation, storm water retention, water quality treatment, and infiltration functions; 2. Minimize overland storm water runoff from a developed site; 3. Maximize the retention of trees, native vegetation, understory plants, and native soils;

4. Minimize soil disturbance;

5. Minimize the conversion of site surfaces from vegetated to nonvegetated surfaces; and 6. Maximize the quantity and use of appropriate native plants on site. The purpose of this chapter is to encourage development proposals to incorporate LID planning and design approaches into project development by providing incentives tied to LID’s use. This chapter seeks to guide land use planning decisions only and does not replace any federal, state or local storm water flow control and water quality treatment regulations. Applicants are responsible for ensuring that their project proposal complies with all applicable regulations.

C. Low impact development approaches

The following list identifies preferred LID approaches that may be proposed within any zoning designation and the technique points associated with the successful use of each approach. Whether the implementation of any LID approach is sufficient to earn technique points shall be subject to the review and approval of the director. 1. Retention of Existing Forested Condition – Up to 25 Technique Points. a. The applicant may earn up to 25 technique points for retaining up to 50 percent of the subject site’s remaining

124 | Title 21: Sammamish Development Code

Effective | January 1, 2022

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