In lieu fee mitigation plan
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- Navigate this page:
- Impacts Being Mitigated
- Credit Generation
- Transfer of Obligations
- Goals and Objectives
- Wetland (Riparian/Floodplain Type) Mitigation Objectives
- Aquatic (In-Water Mitigation Type) Mitigation Objectives
IntroductionOverviewThe purpose of this Mitigation Plan is to describe the details of the Elliott Bridge Reach Off-Channel Habitat and Floodplain Reconnection Project (EBR Mitigation Project), which will create and enhance wetland and aquatic habitat and restore floodplain functions within the Elliott Bridge Reach (EBR) of the Cedar River. The EBR Mitigation Project will be implemented under King County’s In-Lieu Fee (ILF) Program, the Mitigation Reserves Program (ILF Program or KC MRP) by King County to provide compensatory mitigation for unavoidable impacts associated with permitted projects elsewhere in the Cedar River/Lake Washington Service Area. This Mitigation Plan, in its entirety, will be appended to the King County Mitigation Reserves Program In Lieu Fee Program Instrument.
The majority of mitigation credit generated by the EBR Mitigation Project will offset a portion of the Washington State Department of Transportation’s (WSDOT) State Route (SR) 520, I-5 to Medina: Bridge Replacement and HOV Project (SR 520 Bridge Replacement Project or WSDOT Impact Project), permitted by the US Army Corps of Engineers (Corps) and multiple other regulatory agencies (Corps permit # NWS 2008-1246). Mitigation at the EBR Mitigation Project will also offset a portion of impacts associated with the King County Stormwater Services Section’s (KC SWSS) May Creek Drainage Improvement Project (Corps permit # NWS 2010-158) and Northwest Pipeline, LLC’s (NW Pipeline) South Seattle Lateral Expansion Project (Corps Permit # NWS-2012-574). Impacts are further described in Section VII of this plan. Credit GenerationThe EBR Mitigation Project’s credit generating elements include 2.65 acres of wetland establishment, 0.62 acres of wetland enhancement, 0.90 acres of riparian enhancement, 1.02 acres of side channel aquatic area, 0.28 acres of river margin and 3.33 acres of riparian upland enhancement. In addition, an engineered log jam (ELJ) or similar wood structure and multiple habitat elements such as large wood, snags, and brush piles will be constructed and/or placed. These project elements, along with the perpetual protection of 11.5 acres will produce 7.06 credits determined by an area based method using ratios to calculate quantities. The intent of the credit generation at the EBR Mitigation Project is to offset impacts associated with WSDOT, KS SWSS, and NW Pipeline, however, surplus credits generated by the site may be used to offset other impacts in the service area. Attribution of surplus mitigation credit to impact projects will be coordinated with the Interagency Review Team (IRT). Responsibility for completing the mitigation has been transferred to King County via agreements with WSDOT, KC SWSS, and NW Pipeline through King County’s federally and state authorized ILF Program. WSDOT, KC SWSS, and NW Pipeline are also implementing other permittee-responsible mitigation, which is outside the scope of this Mitigation Plan; WSDOT has multiple other mitigation sites in the Lake Washington watershed, KC SWSS completed other permittee-responsible mitigation at the May Creek impact site, and NW Pipeline restored disturbed wetland and buffer areas after temporary impacts. King County issued a Statement of Sale for ILF purchases to WSDOT on June 24, 2013, KC SWSS on June 27, 2014, and NW Pipeline on July 24, 2013. Statements of Sale are on file with the KC MRP, as well as regulatory agencies. Goals and ObjectivesThe EBR Mitigation Project is designed to meet the following objectives specifically outlined in WSDOT’s In Lieu Fee Use Plan. The Mitigation Objectives are specified separately for wetland (riparian/floodplain type) and the aquatic area (in-water mitigation type). Wetland (Riparian/Floodplain Type) Mitigation ObjectivesThe wetland objectives include criteria for both the wetland and buffer areas, as detailed in the mitigation obligations. The wetland mitigation objectives are: Excavate to establish a floodplain wetland complex down to elevations that will support wetland hydrology. Increase vertical and horizontal habitat complexity by creating new, interspersed forested and scrub-shrub wetland areas. Provide soil amendments as necessary to create a suitable growing medium. Integrate habitat features appropriate to the native plant communities, wildlife species, hydrogeomorphic setting, and other site conditions into the mitigation design. These features will include all of the following: Downed logs Standing snags Brush piles Due to dynamic nature of the Cedar River floodplain, it is expected that the EBR Mitigation Project may experience significant change in substrate or vegetation during the monitoring period. Change of this type is consistent with the nature of existing wetlands in this system, and is consistent with the overall intent of the design. The wetland buffer mitigation objectives are: Provide planting densities higher than similar wetland areas to reduce intrusion and provide additional protection for the resources. Increase plant diversity by replanting with native tree species and native shrub species. Reduce prevalence of invasive species. Install additional habitat features such as downed logs, standing snags, and brush piles. Aquatic (In-Water Mitigation Type) Mitigation ObjectivesThe aquatic area objectives includes off-channel habitat, channel margin and riparian/ floodplain components. As addressed in the WSDOT ILF Use Plan the same wetland mitigation areas satisfy these riparian floodplain components. The off-channel mitigation objectives are: Provide off-channel rearing and high-flow refuge salmonid habitat with appropriate baseflow, depth, and other habitat features to provide quality habitat function for salmonids throughout the year. Create a channel profile to minimize potential for fish stranding and maintain positive drainage to the Cedar River. Plant native vegetation to provide adequate shade and overhanging cover along the backwater channel. The channel margin mitigation objectives are to: Provide channel margin habitat along the right bank of the main stem of the Cedar River with suitable substrate for chinook rearing and refuge. Provide an engineered log jam (or similar wood structure) to form a scour pool(s) suitable for adult salmon holding habitat. Wood should be exposed to the normal range of flows including low flows and withstand 100-year flow conditions. The riparian/floodplain mitigation objectives are to: Grade as necessary to create desired floodplain or wetland conditions. Provide stable large woody debris (LWD) features for floodplain roughness. Preserve existing natural vegetation to the extent practical; trees or other vegetation removed during construction will be incorporated in design. Download 7.62 Mb. Share with your friends:
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