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A. The City allows and encourages low impact development (LID) best management practices (BMPs), as an alternative to conventional stormwater management systems that rely on detention ponds and closed conveyance. Low impact development is intended to manage runoff close to the source of generation and to mimic the predeveloped hydrologic condition of a site.

B. Low impact development is accomplished first through minimizing the impervious surface coverage and second by managing runoff through dispersion, infiltration, evapo-transpiration, or a combination of these approaches. Use of LID BMPs may reduce or eliminate the need for conventional detention facilities but does not remove the obligation to comply with the minimum requirements of the Stormwater Manual.

C. A variety of BMPs to minimize impervious surfaces and to manage stormwater have been developed and tested for use in Western Washington. These BMPs and the overall LID approach are described in the LID Technical Guidance Manual for Puget Sound (LID Manual).

D. The menu of LID BMPs identified in the LID Manual are accepted by the City for use in stormwater site plans to address the minimum requirements for flow control and runoff treatment in this chapter, subject to the specifications, performance standards, and design criteria in the LID Manual and review and approval under this chapter.

E. A covenant or easement shall be recorded with the Snohomish County Auditor’s office for each lot containing or served by bioretention facilities in a form approved by the City Attorney. The covenant shall identify requirements and liability for preservation and maintenance of low impact development facilities approved under this chapter and privately held in individual or undivided ownership or intended for public ownership, shall restrict conversion of LID facilities, and shall grant the City access to low impact development facilities on private property to allow inspection, maintenance, and repair.

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