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19-102396-Addendum to Wetland_Stream & Delineation Report & Buffer Averaging Plan-05-21-2020-V1 Beaver Creek Environmental Services, Inc. POB 731695 • Puyallup WA 98373 (253) 732-6515 MHeckert@Q.com May 20, 2020 Mr. Vitaliy Shablevskiy 92 SW 354th Street Federal Way, WA 98023 (253)228-4867 dimaconstruction@yahoo.com RE: Federal Way File #19-102396-UP Parcel 3021049079 & 3021049007 922 SW 356th St., City of Federal Way, Washington Addendum to Wetland and Stream Evaluation and Delineation Report & Buffer Averaging Plan, BCES, January, 2020 Dear Mr. Shablevskiy, Following City of Federal Way review of Critical Areas Assessment – Shablevskiy Residence, this is an addendum to the report to address required deficiencies. REVIEW: 5) LAI requests evaluation of the proposed buffer averaging plan to demonstrate that the proposed plan satisfies FWRC 19.145.440(5)(b): The buffer is increased adjacent to the higher functioning area of habitat or more sensitive portion of the wetland and decreased adjacent to the lower functioning or less sensitive portion. Evaluation of habitat functions provided in the buffer area impacted by the house construction and buffer area proposed for increase is not provided in the report. RESPONSE: The buffer reduction area (fig. 1), located south of the proposed house placement, is a mixed mature forest, predominantly Douglas-fir and Red alder overstory. The shrub layer is reduced, perhaps by brushing. The low shrub layer is Salal. Vegetation indicates this is a drier area of the site. This area slopes to the south, and offers limited wetland recharge through surface flow. Soils are Alderwood. The buffer addition area is in the northeast corner of the site (fig. 2). This area has a deciduous overstory of Red alder, approximately 30 years old. The understory is predominately salmonberry. This area also appears to have been subject to selective logging and brushing. The area has a depression which apparently drains east then south into the wetland on the project site. The vegetation indicates the addition area to be more hydric than the redu ction area. Soils are Alderwood. 2 Shablevskiy FW Addend. Response REV 1 Table 1. Functional Comparison buffer reduction area & buffer add area. ENVIRONMENTAL FUNCTION Buffer Reduce Area Buffer Add Area Hydrological Support Function Moderate Moderate Shoreline Protection Function n/a n/a Stormwater Storage Function Low Moderate Floodwater Storage Function Low Moderate Water Quality Function Moderate Moderate Groundwater Recharge Function Low Low Natural Biological Functions Moderate Moderate Education and Recreational Opportunities Low Low Threatened and Endangered Species Low Low (Adamus et al. 1987: Reppert et al. 1979) Figure 1. Buffer Reduction Area; from NE corner looking SW 3 Shablevskiy FW Addend. Response REV 1 Figure 2. Buffer Add Area; N. Central boundary looking SW Findings & Conclusion: The buffer reduction area and the buffer addition area, as proposed in the Buffer Averaging Plan, have similar characteristics and functional qualities. The functional value is diminished in the reduced area and enhanced in the addition area to a comparable level. The areas provide roughly equivariant functions. Therefore, the buffer averaging scenario is adequate and justified. REVIEW: 8) LAI requests clarification on the 150-foot Splash Blocks shown on the site plans. It is not clear if these are existing or proposed features. If proposed features, please include a discussion of the impacts within the wetland buffer in the critical areas report. RESPONSE: The project design calls for three (3) 150-ft. splash blocks to be installed to convey roof drains away from development. These will convey approximately 150 cu. ft. of rainfall annually to the wetland. The water diverted would come from roof drains, relatively free of contaminants. The location of the drained area slopes towa rd the wetland. The roof drains are expected to change the quantitative regime minimally, only increasing flow conveyance and increasing the periodic 4 Shablevskiy FW Addend. Response REV 1 intake to the wetland. The wetland drains to the City storm system. The splash blocks will not cause additional erosion in the wetland buffer due to design . Due to the design of the splash blocks and the house footprint size, the addition of this flow will have a minimal impact on the functions of the wetland and the buffer. Thank you for your attention. Respectfully, Mark Heckert Pres.