Скачать 3.38 Mb.
|Part of dam removal would involve taking down transmission lines. The lines extend approximately 7 miles from Glines Canyon Dam to Elwha Dam (line 3), approximately 6 miles from Elwha Dam to the Daishowa America paper mill in Port Angeles, Washington (line 1), and approximately 8 miles from Elwha Dam to the Bonneville Power Administration/city of Port Angeles substation (line 2). However, only a portion of transmission line 3 from Glines Canyon Dam to the Elwha Ranger Station is proposed for removal. This is to maintain power to the site.|
Final Site Restoration. Final site restoration would include revegetation and may include the installation of recreation, public safety, and interpretive facilities. Details are presented below and in the appropriate appendixes.
Sediment Monitoring and Management
Natural river processes would be, for the most part, allowed to erode the reservoir areas. Sediment management actions that would be taken include the seeding of native grasses and forbs and strategic placement of large woody debris after the dams were removed. Additional details about the movement of sediment during erosion are presented in the Impacts section.
The rate and amount of reservoir sediment erosion would depend on the dam notching rate, river and tributary flows, and the frequency and intensity of rainfall. The amount of river sediment transport would mostly depend on the river discharge and phase of the notching cycle. Monitoring of channel aggradation conditions, water quality, and fisheries restoration needs would guide some adjustments to the dam removal rate and subsequent sediment levels from Lake Mills, and is considered integral to the project (see table 5). An estimated 50% of the fine sediments in Lake Mills are expected to be removed; the remainder lies outside the floodplain or is buried in coarse delta sediment.
The sediment monitoring plan includes:
Pg. 57 = 59
The stream gauge immediately above Lake Mills at the mouth of Rica Canyon would be phased out and a new one established at Goblin Gates, the upstream entrance to Rica Canyon. The new gauge would be operated concurrently with the existing gauge above Lake Mills for approximately one year before beginning dam removal. The gauging station above Lake Mills would be removed upon the commencement of dam removal.
Although the gauge above Lake Mills is presently at a good location, it would be a poor quality measurement site during dam removal because of a continually eroding stream bed and difficult access. The location at Goblin Gates would be necessary to monitor the natural sediment supply during dam removal and to help guide operation of the pre-treatment facility for the industrial water supply.
The Lower Elwha Federal Flood Control Levee on the east side of the river near its mouth would be raised and strengthened with riprap to maintain the existing 200-year flood protection. Other flood control mitigation, specified in the Impacts section on flooding, is proposed, although not required by the Elwha Restoration Act.
The recovery of Elwha River salmon and anadromous trout involves protection of stocks during dam removal and implementation of a restoration plan after removal is complete. The timelines for principal restoration options are presented in table 6.
The fish restoration plan (appendix 2) provides management guidelines for fully restoring all runs of Elwha River native anadromous fish. The plan describes actions for assessing fish stocks, developing hatchery brood, reintroducing fish by outplanting, managing harvest, and evaluating restoration efforts. Timelines and costs also are included. The 10 anadromous fish stocks that historically used the Elwha River before dam construction are addressed, including winter and summer steelhead, searun cutthroat trout, and native char (Dolly Varden and bull trout), spring and summer/fall chinook, coho, pink, chum, and sockeye salmon.
The plan emphasizes protection of lower river stocks during and immediately following dam removal. Because coho salmon and winter steelhead rear in freshwater for one and two years, respectively, outplanting of these species would begin from one to two years prior to dam removal. Outplanting of chinook and coho salmon and winter steelhead in the middle and upper river would begin when fish passage and water quality were acceptable, and continue for 10 years, depending on the stock. Pink and chum salmon would be outplanted in the middle and lower river. Sockeye salmon (from Lake Sutherland kokanee), summer steelhead (from upper river resident rainbow trout), searun cutthroat trout, and char would be allowed to restore naturally.
TABLE 6 Restoration Actions for Elwha River Anadromous Fish Stocks (SCAN)
Outplanting methods would vary by location (see appendix 2). Above river mile 16 fish stocks would be outplanted by helicopter because of lack of road access. Below river mile 16 outplanting would be done by conventional tank truck and from the hatchery facilities.
Hatchery support would be necessary to develop broodstock for juvenile outplanting and to maintain existing fish production levels during the rebuilding period. The hatchery and rearing channel in the lower river and out-of-basin facilities (Sol Duc and Dungeness hatcheries) would be used to produce juvenile fish for outplanting. Modifications to the Elwha facilities would include improvements to water supplies and upgrades in incubation, rearing, and support capabilities. These would incorporate innovative hatchery practices that simulate natural rearing conditions and potentially improve survival in the wild. The use of the Washington Department of Fish and Wildlife facility in the lower river would be precluded by high sediment concentrations for about two years during dam removal. A rock check dam now used to divert surface water to industrial users (mills) would be removed to ensure full passage.
Pg. 58 = 61&62
For those species and stocks for which there are no viable populations in the Elwha system, other fish stocks are being assessed to identify and develop the most promising sources of broodstock for restoration. This assessment is now being done so that sources would be available for outplanting at the first opportunity.
Adaptive management would be employed. Adult returns would be monitored and reintroduction strategies modified as appropriate. During the reintroduction period, in-river harvest of the recovering stocks would be curtailed only if necessary to meet adult escapement goals.
Summaries of restoration activities for each fish stock are presented below.
Spring Chinook Salmon – Outplant eggs and young-of-the-year progeny of early returning summer/fall chinook salmon during early spring above Carlson Canyon. Over time, spring return characteristics would be exhibited.
Summer/Fall Chinook Salmon – Release fry, fingerling, and smolt from the Washington Department of Fish and Wildlife rearing channel, and outplant the same in the middle river.
Coho Salmon – Release coho smolts from the tribal hatchery and outplant eggs and young-of-the-year or pre-smolts in the upper river. The resident upriver rainbow population (believed to be remnant Elwha steelhead) currently produces smolts that migrate downriver. These fish would return as adults and contribute to steelhead restoration.
Summer Steelhead – Rely on natural recolonization by upriver rainbow trout stock (believed to be remnant Elwha steelhead).
Pink Salmon – Assist in the recovery of the nearby Dungeness River stock, and outplant as fry and/or place eggs in remote site incubators in the middle and lower river.
Chum Salmon – Develop brood from existing lower river stock. Outplanting would be the same as for pink salmon.
Pg. 59 = 62&63
Sockeye Salmon – Rely on natural recolonization by Lake Sutherland kokanee after dam removal.
Searun Cutthroat and Char – Rely on natural recolonization by remnant lower and upriver stocks.
The revegetation goal for the Lake Mills and Lake Aldwell lake beds would be to restore the areas to the conditions and processes that existed prior to the construction of the dams. Krause Bottom, upstream from Rica Canyon, provides a model of plant communities similar to those believed to have occurred within the former lake beds. Sweets Bottom, located between the two dams, also provides a visual model of an open, flat, terraced community, although it has been modified by settlement and clearing. The distribution and composition of native plant species within these two areas, as well as the plant communities on the slopes above the reservoirs, were used in the development of the revegetation plan.
The lake beds would be revegetated through a combination of natural recolonization and a moderately intensive program of planting native species. The dispersal of seeds from upslope and upstream areas would result in a natural reseeding of the lake beds. To accelerate succession, achieve a structurally complex forest ecosystem in a shorter time period, and limit invasion of non-native species, a variety of planting schemes would be used (see appendix 3). Methods would include seeding, use of cuttings, and planting trees of different ages. Fertilizer would be applied with selected individuals to encourage rapid stand development, and species composition would be varied to reflect plant communities on a landscape scale. Additional treatments may include placement of large organic debris and inoculating planting stock with mycorrhizal fungi. Plant materials would be collected only from the Elwha valley to maintain genetic integrity of the ecosystem; planting stock would be propagated prior to dam removal. Nonnative plant species that colonize the lake beds would be controlled or eradicated. The success of natural recolonization and planting would be evaluated annually to determine necessary modifications or remedial measures. Such measures could include the replanting of areas where survival was poor, or manipulating stand density to better achieve goals.
The revegetation program would use a wide variety of native ferns, grasses, forbs, shrubs, and tree species including, but not limited to, vanilla leaf, sedge, sword fern, salmonberry, salal, Oregon grape, willow, bigleaf maple, red alder, western hemlock, Douglas-fir, and western red cedar. Individual site conditions would dictate the mix of plant species used. In wetter areas sedges, lady fern, salmonberry, black cottonwood, willow, red alder, grand fir, bigleaf maple, and western red cedar would be seeded or planted. Upslope forest species would include sword fern, native roses, huckleberry, Oregon grape, salal, western hemlock, western red cedar, and Douglas-fir. Additional details of the revegetation plan are in appendix 3.
Water Quality Protection
The river erosion alternative would result in periods of very high suspended sediment (silt and clay-sized particles) and bedload transport of sand and gravel. As a part of the Elwha Restoration Act, actions are to be considered to protect water quantity and quality for municipal and industrial water users.
Pg. 60 = pg. 63&64
Surface water quantity below Glines Canyon would not be altered by the proposed action, with the exception of a few high flow months during year one of the project. Flood flows would be somewhat moderated below Glines Canyon for two to three months to reduce flooding during construction of the diversion channel at Elwha Dam. Groundwater yield from some near-river wells might be altered in the short term by increases in fine sediment within the aquifer.
To provide for existing water supplies various repairs, upgrades, and short-term treatments are proposed for the existing water systems (table 7). The facilities would be in place and operating before dam removal begins.
Disposition of Lands
Lands acquired at the Glines Canyon Damsite would become part of Olympic National Park and be managed in accord with park policies. The majority of the area would be classified as a natural zone, managed under backcountry/wilderness guidelines. It is expected that this area would be designated wilderness in the future in Opportunity Class IV, or Pristine. This means that wilderness conditions, including ecosystem processes and use-related impacts, would be restored to as pristine a level as practicable. Class III, or a Primitive designation, would be limited to a trail corridor between Boulder Creek and Cat Creek and the area at the mouth of Cat Creek, where camping would be permitted on the gravel bars. The West Lake Mills Trail would be retained, with two to four campsites at the trail’s end restored to wilderness standards. Some of the hydropower facilities at Glines Canyon would be left intact (see below) to provide interpretive opportunities or preserve important historic structures.
The Elwha Act specifies that Aldwell lands should be studied for inclusion in the national wildlife refuge system or the national park system or for transfer in trust to the tribe “for tribal housing, cultural or economic development purposes in accordance with a plan developed by the Tribe in consultation with the Secretary,” or for “development and use by the State.”
The US Fish and Wildlife Service has indicated that the Aldwell land area would be too small to support a wildlife refuge and is not interested in managing the lands for that purpose. The park has stated that the lands qualify for inclusion in the park; adding them would require an act of Congress. The Washington Department of Natural Resources has stated that it is not interested in acquiring the exposed lands if adequate provisions for public assess are made (DOI 1995, comment letter). The department may pursue a possible cooperative management effort with the tribe.
Pg. 61 = 64&65
Table 7. Water Quality Mitigation Measures
The Lower Elwha Klallam Tribe is interested in acquisition of the lands. They have prepared a preliminary land use plan that leaves the river and floodplain protected as a conservation area with suitable uplands managed for natural resources, residential use, and/or economic development. A primary tribal objective is to restore the river’s fishery and ecosystem – any use of project lands must be compatible with this objective. Activities on conservation lands would include fishing, hiking, hunting, and gathering of traditional cultural resources, as well as restoration efforts. In natural resource areas, activities may include riparian and viewshed protection, primitive recreation, selective timber harvest on long rotations, vegetative management for cultural resources, and wildlife management. Residential and economic development areas may include tribal housing and businesses.
Creating interpretive opportunities at both damsites is being investigated as part of possible mitigation for removal of the historic hydroelectric structures. Interpretation would include parts of the Glines Canyon project left in place, wayside exhibits explaining key physical and biological (revegetating areas) features, and documentation of dam removal and ecosystem restoration.
Within the park, each piece of the Glines Canyon project has been evaluated for its value as an interpretive historic resource. Several structures would be left standing, including the powerhouse, spillway, penstock, and gatehouse. A concrete thrust block on the east side of the dam would provide an excellent view of the project area, and would be retained.
The spillway provides significant historical mitigation and interpretation opportunities. Long-term maintenance would be minimal. Some modifications would be necessary for visitor safety, such as improved guardrails (e.g., wire mesh to prevent children from climbing through the guardrails) and measures to prevent people from reaching the spillway chutes by climbing over the spill gates.
The penstock offers significant historical mitigation and interpretation opportunities, with minimal maintenance costs. To provide interpretive opportunities and be included in an interpretive trail, the wooden stairway on top of the penstock would need to be replaced with a low-maintenance, metal stairway. The penstock would probably need to be painted.
The gatehouse offers historical mitigation and interpretation opportunities. If retained, the windows and door would be removed to prevent vandalism and the wooden stairway replaced with a low-maintenance metal stairway. Electrical wiring and wooden power poles would be removed. The guardrail would need modification to increase visitor safety. A final decision whether to retain this structure would require further review.
Although the boathouse offers no retention benefits and would be removed, the two houses and maintenance shed could provide needed office and storage space during deconstruction; they might remain for a short time.
Pg. 63 = pg. 66
The powerhouse offers significant historical mitigation and interpretation opportunities. The windows would be replaced with wire mesh and all hazardous wastes, if any, removed. The metal shed at the site would be removed.
Lower Elwha Klallam sites would be made accessible for the first time in 80 years. Two historic dams would be removed. There would be an increased threat of loss for archeological sites, and historic sites such as the Elwha Ranger Station Historic District. The cultural resource mitigating measures listed in table 8 would be implemented in compliance with Section 106 requirements of the National Historic Preservation Act.
Costs are presented in table 9. Costs of recommended mitigation are included in these totals.
Numerous federal, state, and local permits and review processes are required to implement the proposed action. This document is part of one of those processes, the National Environmental Policy Act of 1969. Required permits are presented in appendix 6. Project permitting costs are included in the final design costs.
The Washington State Department of Ecology regulates water quality under the Clean Water Act. The Department of Ecology also regulates water quantity with water rights for water withdrawals and permits temporary modifications of water quality criteria. The Safe Drinking Water Act and Washington Administrative Code 173-201A also set drinking water standards. The proposed action would be in compliance with these requirements.
The Elwha River Restoration Act authorizes the secretary of the interior to implement actions to protect municipal and industrial water supply and quality. The proposed action would mitigate the increased levels of turbid waters with water treatment facilities and upgrades to water intakes where appropriate. These facilities and upgrades would meet appropriate water quality standards for water supplies, providing protection from the turbid waters during and following dam removal.
Table 8. Mitigation Measures Required under the Interagency Programmatic Agreement and Section 106 of the National Historic Preservation Act
Pg. 64 = pg. 67
The Clean Water Act, Section 404, and the Rivers and Harbors Act, Section 10, address project dredge and fill areas, specifically for excavation in streams or wetlands, which includes structure removal and water intake upgrades. Construction in and near the Elwha River is reviewed under the State Shoreline Management Act and requires a Hydraulic Project Approval from the Washington State Department of Fish and Wildlife. The proposed action would be in compliance with these requirements.
Dredge and Slurry Alternative
Summary of Actions
Features of the Dredge and Slurry alternative include: