In lieu fee mitigation plan


Elliott Bridge Reach Mitigation Credits



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Elliott Bridge Reach Mitigation Credits


The EBR Mitigation Project is designed to achieve mitigation credit in excess of the WSDOT, KC SWSS, and NW Pipeline mitigation obligations. Mitigation Credits achieved at the EBR Mitigation Project will be assigned first to the WSDOT obligations, second to compensate for the KC SWSS and NW Pipeline impacts, and third to compensate for onsite wetland impacts of the EBR Mitigation Project. Any additional mitigation credit, once the IRT determines the WSDOT, KC SWSS, and NW Pipeline credits have been fulfilled, may be assigned to other mitigation obligations (beyond the SR 520, May Creek Drainage Improvement, and NW Pipeline impacts), in coordination with the IRT. The EBR Mitigation Project needs, credits, and anticipated remaining credits are detailed in Table 8.

Using an area based credit system, quantified with ratios; the EBR Mitigation Project anticipates 7.06 credits to be generated by year 10. All wetland establishment areas are calculated using a 1:1 ratio. Enhancement areas are calculated using a 3:1 ratio. Riparian Upland Enhancement is calculated using a 4:1 ratio as shown in Table 8. Since the EBR Mitigation Project was previously approved for use as permittee responsible mitigation for WSDOT, WSDOT’s wetland buffer impacts may be offset using portions of the non-credit generating regulatory buffer on the right bank (1.18 of the 1.97 credits needed). The remaining 0.79 credits are generated by the riparian upland enhancement area. The right-of-way vacation on the left bank accounts for 0.37 credits. If the right-of-way vacation does not occur within the 10 year monitoring period, a 100 foot regulatory buffer will be implemented and this will remove 0.37 credits. The credit release schedule reflects the need to vacate the right-of-way prior to the release of 0.37 of the final 1.16 credits. Remaining potential surplus credits will be generated using the ratios in Table 8. Any impact project that uses credits from EBR Mitigation Project to offset impacts will purchase credits based on acreage and not using the credit/debit method.



Table 8 EBR Anticipated Credits, Mitigation Obligations and Anticipated Surplus

  1. Performance Standards


The performance standards for the EBR Mitigation Project were developed based on the objectives and performance standards included in the ILF Use Plan and WSDOT’s Final Mitigation Plans and include those performance standards that were revised in consultation with the IRT. The performance standards have also been updated to reflect and be consistent with the revised King County designs. These performance standards address the methods used to document performance and are intended to both document project performance as well as be a practical way to manage the project site over the performance period.

Objective 1.1. Protect Aquatic Ecosystem Functions

Performance Standards for Administrative Functions

Documentation

1.1.1. Complete development of an approved mitigation plan.

Mitigation plan has been approved by the IRT and appended to the Instrument.

1.1.2. Protect ecosystem functions on the site by placing IRT-approved restrictive covenants on the right bank.

Provide IRT with a copy of the recorded restrictive covenants.

1.1.3. Protect ecosystem functions on the site by placing IRT-approved restrictive covenants on the left bank.

Provide IRT with a copy of the recorded restrictive covenants.

Objective 2.1. Build project elements according to IRT approved plans

Performance Standards for Construction

Documentation

2.1.1. Grading and earthwork complete according to IRT approved plans.

As-built drawings showing completed grading and earthwork are approved by the IRT.

2.1.2. Planting of site completed according to IRT approved plans.

As-built planting plan showing completed planting is approved by the IRT.

2.1.3 At a minimum, snags1, jams, Type C logs2, spanner logs3, and debris logs with branches4 are installed per approved plan drawings.

As-built drawings showing the location of each listed feature are approved by the IRT.

2.1.4. An ELJ or similar wood structure is constructed according to IRT approved plans.

As-built drawings showing completed ELJ or similar wood structure are approved by the IRT.

Objective 3.1. Establish a minimum of 2.51 acres of wetlands and dynamic floodplains

Performance Standards for Dynamic Floodplains and Wetlands in all Mitigation Credit Areas

Documentation

3.1.1. By Year 10, establish a minimum of 2.51 acres of wetlands and/or dynamic floodplains in the mitigation areas. To accommodate natural river processes, wetland areas5 and floodplain areas6, all count toward the 2.51-acre target (see p. 101, 103, and 111 in ERDC/EL TR-10-3), though the ratios of each may change. There will be a minimum of 1.0 acres of wetland present on the entire site encompassing both banks.

Monitoring reports documenting the combined area of wetlands and floodplain areas, as defined below. These areas will be documented in Years 5 and 10.

Wetland Areas: Delineate wetland boundaries on both left and right banks in Years 5 and 10. Use soil pits to validate soil saturation. Assess hydrophytic vegetation according to the Regional Supplement to the Delineation Manual (ERDC/EL TR-10-3)



Objective 3.2. Provide wetland wildlife habitat by establishing new wetland areas with a diverse native wetland plant community.

Performance Standards for Native Vegetation in Wetland Establishment and Riparian Enhancement Areas

Documentation

3.2.1. At Year 1, the average density of planted and volunteer native shrubs and trees will exceed 1,740 per acre (4/100 ft2 or 5 feet o.c.).

Monitoring reports documenting native shrub and tree density. Plant density per planting area will be recorded for Year 1.

3.2.2. Crown cover of native shrubs and trees will be a minimum of 10% at Year 3, 35% at Year 5, 50% at Year 7, and 70% at Year 10.

Monitoring reports documenting measurements of native crown cover per planting area. Crown cover of native shrubs and trees will be measured in Years 3, 5, 7, and 10.

Objective 3.3. Provide wildlife habitat features –snags, downed logs, and brush piles– to improve the quality of the constructed habitat.

Performance Standards for Wildlife Habitat Features in All Mitigation Credit Areas

Documentation

3.3.1. Retention of snags, ‘jams’, Type C, and ‘spanner’ large wood will be a minimum of 80% in Year 3, 60% in Year 5, and 50% in Year 10. Though the intent is for wood to remain stable, incidental loss or fragmentation of Type C wood as specified here is acceptable. There is no retention standard for brush piles.

Document the number of snags, ‘jams’, Type C, and ‘spanner’ large wood that remain in their original location, based on approved as-built. Count the number of Type C pieces in Years 3, 5, and 10. Pieces obscured by vegetation may be assumed to have been retained. Secured and recruited wood (at least as large as Type C wood) will qualify toward the final 50% retention target.


Objective 4.1. Improve upland wildlife habitat by converting formerly developed residential yards into a native forested community.

Performance Standards for Native Vegetation in Riparian Upland Enhancement Areas on the Right bank (only) and the Wetland Enhancement Areas on the Left bank

Documentation

4.1.1. At Year 1, the average density of planted and volunteer native shrubs and trees will exceed 1,740 per acre (4/100 ft2 or 5 feet o.c.).

Monitoring reports documenting native shrub and tree density per planting area. Native plant density will be recorded for Year 1.

4.1.2. Crown cover of native shrubs and trees will be a minimum of 10% at Year 3, 30% at Year 5, 40% at Year 7, and 50% at Year 10.

Monitoring reports documenting measurements of native crown cover per planting area. Crown cover will be measured in Years 3, 5, 7, and 10.

Objective 5.1. Provide channel margin habitat for salmonids along the mainstem Cedar River.

Performance Standards for River Margin Habitat for Juvenile Salmon

Documentation

5.1.1. A minimum of 0.19 acres of mainstem channel will have surface velocities less than 0.15 meters per second at 800-1200 cfs (USGS 12119000; Renton) by Year 3 and remain present through Year 10.


Monitoring report documenting the area and location of “river margin”. Planform maps of wetted channel areas meeting velocity criteria will be created in Years 3, 5, 7, and 10.

5.1.2. In Years 1, 3, 5, 7, and 10, the Type B large wood structures7 will be hydraulically engaged with the river.

Photo document Type B structures within specified flow range. Type B structures are ‘hydraulically-engaged’ when some portion of the structures or racked wood contacts the wetted channel at 800-1200 cfs (USGS 12119000; Renton).

Hydraulic engagement will be documented in Years 1, 3, 5, 7, and 10.



Objective 5.2. Provide an engineered log jam (ELJ) or similar structure to form a scour pool suitable for adult salmon holding habitat; wood should be exposed to normal range of flows and withstand 100-year floods.

Performance Standards for the ELJ Structure on the Right Bank of the Mainstem

Documentation

5.2.1. The ELJ forms an eddy scour pool8 or lateral scour pool9 (Bisson et al. 2006, p. 35) with a minimum residual depth of 1.31 feet, a minimum area of 53.8 ft2 (TFW, 199910) and more than 20 ft2 of over-water woody cover. At a minimum, this condition exists following a 5-year flood (4,299 cfs at Renton (USGS 12119000; Renton)) or by Year 10, whichever is sooner.

Measure the scour pool dimensions. Also measure two existing reference pools for comparison11. Monitor in Years 1, 3, 5, 7, and 10.

5.2.2. The ELJ structure is hydraulically engaged within the wetted portion of the channel (as measured during the late summer or early fall low-flow period).

Photo-document the ELJ structure at low flow. The ELJ is ‘hydraulically-engaged’ if some portion of ELJ or racked wood contacts the wetted channel when discharge is at least 200 cfs (USGS 12119000; Renton), unless the low-flow channel has migrated away from the ELJ or a gravel bar forms beside the ELJ. Neither outcome constitutes a failure to meet this standard. Photo-document in Years 1, 3, 5, 7, and 10.


5.2.3. No key logs—those necessary for structural integrity— in the ELJ are missing or broken.

Photo-document the ELJ structure and inspect key logs. Monitor in Years 1, 3, 5, 7, and 10.

5.2.4. Adult salmon are observed in the ELJ-formed scour hole, unless they are also absent from the two reference pools.

Video-document daytime use of the ELJ-formed scour hole and two reference pools by adult salmon with an underwater video camera. Monitor in Years 1, 3, 5, 7, and 10.

Objective 6.1. Create a backwater channel to provide off-channel rearing and high-flow refuge habitat for salmonids, with appropriate flow, depth, and slope to provide habitat functions throughout the year.

Performance Standards for Aquatic Habitat Characteristics in the Backwater Channel

Documentation

6.1.1. In Years 5 and 10, a minimum of 0.51 acres of ‘off-channel habitat’ is present on the left bank.

Monitoring report documenting off-channel habitat area measured as the total area of left-bank off-channel features below the OHW elevation, as measured in the mainstem channel adjacent to the backwater channel along a transect from the mainstem to the off-channel area oriented perpendicular to the mainstem thalweg.

6.1.2. In Years, 1, 3, 5, 7, and 10, the connection point between the backwater channel and the mainstem is at least 0.5 feet deep at 800 cfs (USGS 12119000; Renton).

Measure the depth of the connection point when discharge is approximately 800 cfs (USGS 12119000; Renton). Document in Years 1, 3, 5, 7, and 10.

6.1.3 In Years 1, 3, 5, 7, and 10, below the confluence of the two upper lengths of backwater channel, the backwater channel will be passable for juvenile salmonids (at least 2-inches deep), and contain residual pools at least 6-inches deep when discharge exceeds 200 cfs ((USGS 12119000; Renton)typical of low-flow conditions in late summer).

Monitoring report documenting off-channel habitat channel length, based on approved as-built. At low-flow conditions, document fish use of the backwater channel and in any closed depressions, if present, during summer low-flow conditions. Document wetted length in Years 1, 3, 5, 7, and 10.

Objective 7.1. Establish diverse native wetland and upland plant communities

Performance Standards for Invasive Species in All Mitigation Credit Areas

Documentation

7.1.1. In Years 1-10, the following weeds are absent from the project site: Washington State-listed or King County-listed Class A weeds designated for control by the County Weed Board; Non-native knotweeds identified on the King County noxious weed list.

Monitoring reports documenting presence or absence of listed weeds at Years 1, 3, 5, 7, and 10.

In Years 1-10, the combined ground cover (total cover of the target vegetation on an area of ground; Bonham (2013)) of the following plants does not exceed 10% in each mitigation area:

  • Non-native blackberries (Rubus armeniacus and R. laciniatus),

  • Scotch broom (Cytisus scoparius)

  • Thistles (Cirsium arvense, C. vulgare, Carduus nutans, and Onopordum acanthium),

  • Purple loosestrife (Lythrum salicaria),

  • Yellow-flag iris (Iris pseudacorus),

  • English and Atlantic ivy (Hedera helix and H. hibernica),

  • Butterfly bush (Buddleia davidii),

  • Field bindweed (Convolvulus arvensis) and morning glory/hedge bindweed (Convolvulus sepium),

  • Any other Class B or C weeds designated for control by King County.




Monitoring reports documenting non-native invasive species cover. Document percent cover of listed invasive plants in each mitigation area at Years 1, 3, 5, 7, and 10. Monitor conditions each year.




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