10200 19TH AVE SE COSTCO FUEL STATION 2016-01-01 MF Import

Wetland issues: The �r�etlands that were initially filled were analyzed in the draft EIS, Appendix F. The original mitigation plan had to show that the water quality function of the mitigation wetland would be enhanced as compared to the wetlands that would be flled. Hydraulic residence time and vegetation type and density were the primary wetland characteristics that were I�nked to water quality function. The analysis showed that the propos;:d mitigation wetland, if it were constructed and functioned as designed, would function more effectively to improve water quality than the existing wetlands. (That were proposed to be filled, and which have now been filled.) Additional filling of wetlands is proposed as a part of the parking lot modification and gas station improvements. A new analysis is needed that includes the additional wetland impacts and that documents the existing wetland's water quality function. A wetland mitigation plan must be developed that shows that the mitigation wetland will have an enhanced water quality function as compared to the wetland that will be altered. In addition, a plan must be developed that will bring the original mitigation wetland into compliance with the criteria that were originally set for that wetland. These criteria are hydraulic residence time (influenced by the volume of dead storage and wetland bottom contours) and vegetation type and density. Requirement to move forward: Wetland alteration is permissible only if the criteria in EMC 19.37.100.6.5 are met. A wetland mitigation plan must be prepared by the applicant and appr,�ved by the City that demonstrates that the final mitigation wetland will function mora� effectively to treat stormwater runoff than did/do the wetlands that have been ano those that are now proposed to be filled. Other requirements of the City'� wetland regulations must also be met. For example, the proposed service station will reduce th� required buffer along the southwest corner of the existing mitigation wetland, and could potentially expose more phosphorous containing soil. The conceptual wetland m t�gation plan must identify how those issues will be addressed. A detailed contingency plan must also be developed, with sufficient funds set aside to address the poteritial failure of the mitigation wetland to meet the mitigation performance goals. The original mitigation wetland had the following designed increases in water quality function characteristics: � . Doubled dead storage (to 44,300 cubic feet) • 50% mora liv� storage (49,190 cubic feet). . Tripled hydraulic residerce time (tripled to 10.7 days). • Greatly enhanced emergent vegetative cover 2