11415 AIRPORT RD 2023-11-28 - Laserfiche WebLink

7.0 Water Quality The on -site unnamed tributary of Swamp Creek is rated a Category 5, a 303(d) listed stream for water quality. Swamp Creek and the tributaries of Swamp Creek have significant water quality issues. Water quality parameter that have been tested and do not meet state water quality standards are dissolve oxygen and bacteria. Homeless people living on the property have probably contributed to fecal coliforms. There is a plan to improve water quality in the Swamp Creek subbasin, see Swamp Creek Fecal Coliform Bacteria TMDL, Water Quality Improvement Report & Implementation, June 2006. hM2s:Hfortress.wa. og v/ecy//publications/documents/0610021.pdf 8.0 Invasive Plants The wetland and critical area buffer have Himalayan blackberry throughout much of the understory. A portion of the east critical area buffer is vegetated with grasses, weeds, and Scot's broom (Cytisus scoparius). All invasive plants will be removed, and sparsely vegetated areas will be replanted with native plants. 9.0 Animals Wildlife observations were incidental to the critical area delineation and data collection. Observed wildlife species include American robin and Northwestern crow. Habitat fragmentation and urban development limit species use. There are no documented priority species present on or near the site, see PHS map. 10.0 Description of Proposed Actions The proposed action is to reduce the wetland and stream buffers to 75% of the full buffer width and mitigation for wetland reduction area at a 2:1 ratio. Wetland buffer encroachment for the required street improvements will be replaced at a 1:1 ratio along on -site wetland buffer. 11.0 Assessment of Probable Cumulative Impacts to Wetlands and Buffers The cumulative impact to critical areas and their buffers will be an improvement in overall functions and values. The wetland reduction area will be replaced by creating wetland on -site and in -kind at a 2:1 ratio. Wetland and stream buffer reductions are allowed by code when general mitigation measures are applied. These measures include removal of invasive plants, enhancement of sparsely vegetated areas, and blocking and directing exterior lighting from buffer. Cumulative Impacts & Mitigation Wetland Reduction Area 2,148 sf Wetland Creation Area 4,551 sf Wetland Mitigation Ratio 2:1 Wetland Buffer Encroachment 3,772 sf Wetland Buffer Replacement 3,772 sf Buffer Mitigation Ratio 1:1 2