Sammamish Unified Development Code

Environment & Sustainability | Environmentally Critical Areas

2, individually, have whole-lake total phosphorus concentrations of 36 (±2) micrograms/liter and 20 (±1) micrograms/liter, respectively; ii. Whole-lake total phosphorus concentration, chlorophyll a, and Secchi depth indicate that the Beaver Lake system is bordering on eutrophic conditions; iii. Modeling of the Beaver Lake system’s future trophic status indicates that the lake will become hypereutrophic with a whole-lake total phosphorus concentration predicted to be 36 micrograms/liter without additional phosphorus removal via storm water treatment; and iv. Maintaining existing trophic status is a management plan goal. To maintain existing trophic status, an 80 percent total phosphorus annual loading removal goal was established for new impervious surface development prior to storm water discharges to Beaver Lake. d. The Pine Lake watershed is generally identified in the City of Sammamish Comprehensive Plan (Figure IV-1 in the Comprehensive Plan or as updated). All appropriate Beaver Lake specific water quality regulations shall be extended to the Pine Lake drainage basin. i. These regulations shall only be in effect until such time that a customized Pine Lake water quality strategy is developed and development regulations are adopted based on approved findings of the study.

ii. An applicant for development within the Pine Lake drainage basin may apply for a variance from the standards specified in subsection g. of this section if it can be proven that conditions are clearly different than at Beaver Lake. e. The standards specified in subsection g. of this section shall apply to all development proposals located within the Beaver Lake and Pine Lake watersheds which require drainage review as specified in the adopted surface water design manual and SDC 21.03.050, Surface Water Management. f. Development proposals within the Beaver Lake or Pine Lake watersheds may be exempt from management plan requirements if they demonstrate to the satisfaction of the community development department that on-site surface and storm water runoff drainage does not in fact drain into the basin in question.

g. Phosphorous Control Required.

i. Applicability. Unless the conditions identified in subsection f. of this section are documented to the satisfaction of the department, the following development proposals are subject to the conditions and standards contained in subsections g.ii. through g.iv. of this section: a) Projects that create greater than 5,000 square feet of new impervious surface subject to vehicular use in the Beaver Lake or Pine Lake watersheds; or

Errata Revisions | November 17, 2022 Effective | January 1, 2022

122 | Title 21: Sammamish Development Code

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