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HomeMy WebLinkAboutSHR2021-00016 Lake Cushman Debris Removal Ramp - HMP Habitat Managment Plan - 8/27/2021 3628 South 351h Street Tacoma,Washington 98409-3192 R� TACOMA POWER TACOMA PUBLIC UTILITIES , O TACOMA PUBLIC UTILITIES 40 August 19, 2021 Ms. Julie Lewis Mason County Community Services PO Box 279 Shelton, WA 98584 SUBJECT: Habitat Management Plan for the Lake Cushman Debris Removal Ramp Project Dear. Ms. Lewis Per Mason County Code, this Habitat Management Plan has been prepared for the proposed Debris Removal Ramp project along the southern shoreline of Lake Cushman, (see attached project vicinity map). The proposed project is located on property currently owned and managed by Tacoma Power. The site is located in the southwest quarter of Section 5, Township 22 North, Range 4 West, W.M. The proposed construction area is part of Mason County parcel #422050060000. This assessment is required per Mason County Code, Title 8.52.170, fish and wildlife habitat conservation areas. This analysis is required because the project is adjacent to and within a regulated habitat conservation area (Lake Cushman). The intent of Title 8.52.170 is to: • Protect critical habitat features to support genetically viable populations of fish and wildlife species and allow for commercial and non-commercial uses; • Protect the biological, physical, and chemical components of water quality for the benefit of aquatic and terrestrial resources, as well as human consumptive uses; • Ensure that natural stream and marine shoreline functions such as flow patterns, production of sediment and large woody debris are maintained with minimal interference of impact to private property; • Protect habitat for federal or state listed endangered, threatened or sensitive fish and wildlife; • Encourage non-regulatory methods of habitat retention whenever practical, through education, and the Open Space Tax Program; • To supplement the Shorelines Master Plan for Mason County to preserve and protect critical fish and wildlife habitat pursuant to (WAC 365-190-080(5)). It is the intent that the ordinance codified in this chapter will compliment and supplement the Shorelines Master Plan; and • To implement the Mason County comprehensive plan and to achieve these purposes consistent with the comprehensive plan. In addition to being located adjacent to a habitat conservation area, several species of importance that are listed under Title 8.52 are potentially present in the project area. These include: Puget Sound Chinook Salmon, Bull Trout, Northern Spotted Owl, and Marbled Murrelet. Ms. Julie Lewis August 19, 2021 Page 2 The National Marine Fisheries Service lists the Puget Sound Chinook Salmon Evolutionarily Significant Unit (ESU) as threatened. Bull Trout, Northern Spotted Owl, and Marbled Murrelet are all listed as threatened by the United States Fish and Wildlife Service. Lake Cushman provides critical habitat for Chinook Salmon and Bull Trout. Project Description Tacoma Power is proposing the installation of a Debris Removal Ramp along the southern portion of Cushman Dam No. 1 Reservoir (Lake Cushman). The ramp will be approximately 170' long (including upper graveled portion) and 40' wide with the top of the ramp being at approximate elevation 744' and the lower end of the ramp extending down into the reservoir to approximate elevation 730'. The toe of the precast concrete block bulkhead will extend down to approximate elevation 720'. Ordinary high water (OHW or full pool) for Lake Cushman is elevation 738'. The structure will be comprised of precast concrete blocks, precast concrete interlocking panels, a pour in place concrete anchor section (located above OHW) and fill/dressing material. The purpose of the project is to facilitate the removal (and hauling) of debris from the Cushman No.1 reservoir. Construction of the ramp is intended to reduce or eliminate ground disturbance and turbid discharges associated with dragging material up and along the shoreline. Following construction, the ramp will mitigate discharges of material and disturbances to the shoreline. Construction of the ramp will facilitate the removal of intact Large Woody Debris (LWD). Removal of larger pieces of LWD and eliminating or decreasing the need to cut LWD into more manageable sizes will ultimately result in more availability of LWD suitable for local restoration projects. Project construction is anticipated to occur between October 2022 and March 2023, during annual reservoir drawdown. Work will be performed outside the wetted perimeter of the reservoir both above and below OHW. Project equipment will likely include excavators, heavy trucks, hand tools, and possibly a crane to place the precast concrete blocks and precast concrete interlocking panels. Some minor excavation and associated grading will be required to establish appropriate grades and elevations for construction. Project Area Setting Land use in the vicinity of the project is mainly low to moderate density residential development, as well as recreational uses. The area around and in the vicinity of the project site is managed as a hydroelectric dam and associated infrastructure. The area around the project site consists of forested sloping areas to the south and west, and residential development east of Cushman #1 Dam. Lake Cushman extends north of the project site. Cushman #1 Dam spillway is directly east of the project site. The location where work will be completed is currently being used as a debris removal site, along gently sloping shoreline. Existing shoreline substrate in the vicinity of the project consists of lake sediment, gravel and cobble. Vegetation along the shoreline east and west of the site is dominated by grasses, forbs, brush and a few trees. Species observed include: Douglas fir, black cottonwood, red alder, ocean spray, bracken fern, salal and trailing blackberry. Ms. Julie Lewis August 19, 2021 Page 3 Mason County Code Requirements Mason County Code, 8.52.170, Table 3, outlines required fish and wildlife habitat conservation buffer widths for streams, lakes, and shorelines. Lakes over 20 acres in size require a 100 foot buffer from the ordinary high water mark. However, Mason County may decrease the buffer after consultation with other agencies and interest parties, and approval of a habitat management plan and public hearing. Mitigation for a given project must be adequate to preserve or enhance the functions and values of the critical area. The Code states that "this means that a finding must be made that the net effect of the proposal is equal or better than applying the standard buffers." Allowable mitigation measures listed in the Code include: the establishment of buffer areas, preservation of critically important plants and trees, limitation of access to the habitat area, seasonal restriction of construction activities and other potential measures. Impacts to Fish and Wildlife Habitat Conservation Areas As previously stated, limited vegetation will be removed as part of the project. Work will be completed during the fall and winter months, during the drawdown period of the reservoir, so no surface water will be present during project construction. Erosion and prevention control measures in concurrence with a Water Quality Protection Plan (WQPP) filed with the Department of Ecology will be implemented to prevent impacts to the reservoir. The main impact to the riparian area will be the loss of natural shoreline area that will be replaced with a concrete debris removal ramp. The shoreline habitat that will be lost is gently sloping, mostly unvegetated and is inundated for a limited period annually. Bald Eagles are present in the vicinity, but the habitat in the area of the project is marginally suited for eagles. The project is not anticipated to affect eagles, as there is no significant nesting or foraging habitat which will be impacted. Project work may temporarily produce elevated noise levels and activity at the site, but the surrounding area is already developed as a residential community and dam and is regularly subjected to disturbance. Extensive nesting and foraging habitat for eagles is present in other areas around the Lake Cushman Shoreline. Marbled Murrelet and Northern Spotted Owl are potentially present in the general area, but are not known to occur within a mile of the project site. No suitable nesting habitat for these two species occurs within one mile of the site as determined from a nesting habitat evaluation and mapping conducted for the Cushman Project by Meridian Environmental in 2013. No suitable foraging or dispersal habitat is present in the vicinity of the site. No impacts to these species are anticipated as a result of the project. Bull Trout and Puget Sound Chinook Salmon are both present in Lake Cushman. Both species are landlocked and confined to Lake Cushman and its tributaries. Bull Trout (and to a much lesser extent, Puget Sound Chinook) are known to spawn in the North Fork Skokomish River between the lake and Staircase Rapids. Both of these species would mainly utilize Lake Cushman as rearing habitat, and would show preference for the deeper water areas of the reservoir. The only exception would be juvenile Puget Sound Chinook, which may use the nearshore areas for rearing. However, the Chinook population within the lake is limited, its usage of these habitats is not well documented, and work will be completed during the drawdown period in the fall and winter. It is possible that the project could have an effect on Ms. Julie Lewis August 19, 2021 Page 4 the juvenile migration patterns of Chinook Salmon, but this effect is likely negligible as these fish are already likely not utilizing the project area as discussed above. Mitigation Proposed mitigation for the project will include: completing work during the fall and winter months during the drawdown period of the reservoir so no surface water will be present during project construction, and implementing erosion prevention and control measures in concurrence with the WQPP, and limiting the area of disturbance to the minimum required to accomplish project tasks. Additionally, limited vegetation will be removed, as the project will be constructed at the already existing debris removal location within the drawdown zone. Additional mitigation, consisting of adding woody debris to the shoreline of the reservoir has been developed in consultation with the Washington Department of Fish and Wildlife (WDFW) and is discussed below. The main impact to the riparian area will be the loss of natural shoreline area that will be replaced with a concrete debris removal ramp. The shoreline habitat that will be lost is gently sloping, mostly unvegetated and is inundated for a limited period annually. Due to the above factors, limited aquatic habitat will be lost. Based on consultation with WDFW, large woody debris will be placed in a specific location within the reservoir below full pool elevation. This will provide mitigation for the area of impact, and will result in no net loss (and potentially a net gain) of aquatic habitat and functions. The area where woody debris will be placed is equal to or greater in total shoreline impact area than the area where the ramp will be constructed. The mitigation area presently consists of unvegetated gravel and cobble. Large woody debris will be partially embedded in the substrate to prevent washout or loss of debris material. The location and specifications of the proposed mitigation activities are shown on the attached project plan. Because the project mitigation is limited to placement of large woody debris, little maintenance and monitoring would be useful or required. Periodic (at least twice a year) monitoring of the placed debris will be completed for the first five years following placement to make sure it is still in place. No other recommended performance standards outlined in 8.52.170(J)(5)(d)(iii) would be applicable to the proposed mitigation. Based on these factors, we believe the project meets the habitat conservation requirements and the intent and goals of this section of the Mason County Code. As outline in this letter report, mitigation measures consistent with this Title will be implemented where possible, and no impact to any species listed in 8.52.170, Table 3 are anticipated. Consistent with 8.52, Appendix C, outlines best management practices (BMP's) that need to be adhered to throughout the construction phase: • Appropriate erosion control devices, such as silt fencing, mulch berms, and erosion control matting should again be used if needed during all aspects of the construction phase to mitigate potential erosion and runoff in the stream. • The most important goal during the construction phase is to consolidate the time period in which heavy earthmoving machinery is used. Earthwork activities should be implemented during the driest season of the year to minimize the risk of erosion-relate impacts to the stream. Any work requiring use of this type of equipment(such as site Ms. Julie Lewis August 19, 2021 Page 5 grading, road building, grubbing, cutting and filling) should also be implemented over short periods or events. This should avoid continued and prolonged disturbance of the environment with heavy equipment, as would be the case if the work occurred over multiple and/or unconsolidated events. • Construction activities should be confined to discrete areas of the site to minimize disturbance to native vegetation in the buffer • No construction debris or supplies should be placed in existing forested areas or anywhere along the stream bank. • Coinciding with, or immediately subsequent to the completion of the construction work, the restoration and stabilization of bare ground should occur. Restoration and stabilization phases include the application of a native seed mix and landscape stabilization of any cut and filled areas. Native species of plants should be used in transition zoned between the construction area and undisturbed native vegetation. The suggested BMP's focus on reducing increases in impervious surfaces, preserving hydrologic functions, and controlling potential adverse impacts to water quality. • Clearly mark clearing limits with orange construction fencing; • Install silt fencing at the clearing limits to prevent surface runoff, erosion, and water quality degradation; • Cover or mulch bare areas to prevent surface erosion • Hydroseed disturbed areas with a slurry of native grass seed, mulch, and tackifier as soon as possible following completion of construction and at a minimum before the onset of fall rains; Tacoma Power plans to adhere to and implement the above BMP's and additional BMP's in concurrence with the WQPP during and following construction, as well as during installation of the large woody debris as part of project mitigation. Although project work needs to occur during the later fall and winter months (to coincide with the lower water levels in the reservoir), it will be done during a period of forecasted dry weather. We understand that Mason County has final authority in granting approval of this habitat management plan, and any required mitigation measures for the project. If you have any questions, please contact me at 253-208-2814 or email at mpeterca-,)cityoftacoma.orq. Sincerely, Matt Peter Natural Resources Biologist Attachments: Project Plans