Final Environmental Impact Statement

НазваниеFinal Environmental Impact Statement
Дата конвертации28.10.2012
Размер1.55 Mb.
  1   2   3   4   5   6   7   8   9   ...   37
Final Environmental Impact Statement

Elwha River Ecosystem Restoration

Purpose and Need: The Elwha River ecosystem and native anadromous fisheries are severely degraded as a result of two hydroelectric dams (projects) and their reservoirs built in the early 1900s. Congress has mandated the full restoration of this ecosystem and its native anadromous fisheries through the Elwha River Ecosystem and Fisheries Restoration Act (Public Law 102-495). The Department of the Interior therefore finds there is a need to return this river and the ecosystem to its natural, self-regulating state, and proposes removing both dams to accomplish this purpose and fulfill the congressional mandate.

Proposed Action: The U.S. Department of the Interior proposes to fully restore the Elwha River ecosystem and native anadromous fisheries through the decommissioning of Elwha Dam and Glines Canyon Dam and removal of all structures necessary, including all or part of both dams, powerhouses, reservoirs, and associated facilities to achieve this purpose. The proposed action is located in Clallam County, on the Olympic Peninsula, in Washington State.

Lead agency: National Park Service

Cooperating agencies: U.S. Fish and Wildlife Service, U.S. Bureau of Reclamation, U.S. Bureau of Indian Affairs, U.S. Army Corps of Engineers, and the Lower Elwha S’Klallam Tribe

Type of statement: This is a final environmental impact statement. In preparing this, the Department of the Interior has adopted the majority of a draft environmental impact statement titled “Proposed Elwha (FERC No.2683) and Glines Canyon (FERC No.588) Hydroelectric Projects, Washington” as updated and renamed Draft Staff Report in March 1993 prepared by the Federal Energy Regulatory Commission. Also incorporated into the record of this environmental impact statement is the Elwha Report and its appendixes, prepared by the U.S. departments of the Interior and Commerce and the Lower Elwha S’Klallam Tribe (Jan. 1994). This environmental impact statement supersedes both the Federal Energy Regulatory Commission environmental impact statement and the Elwha Report.

Abstract: In addition to the proposed action, four other alternatives are examined. They are: Dam Retention with mitigation measures installed for fish passage, Removing Glines Canyon Dam only and installing fish passage measures at Elwha Dam, Removing Elwha Dam only and installing fish passage measures at Glines Canyon Dam, and No Action (dams are retained without fish passage measures). The proposed action is also the Department of the Interior’s “preferred alternative.” Short term negative impacts from removing both dams could occur from sediment built up behind them. If sediment is allowed to erode naturally, the finer grained particles, such as silt and clay, could temporarily but significantly impact fish or other aquatic organisms. Impacts on water quality, river morphology, native anadromous and resident (i.e., trout and char) fisheries, living marine resources, wildlife, threatened and endangered species, vegetation, cultural resources, land use, recreation, esthetics, socioeconomics and river ecology are also examined in this environmental impact statement. Alternatives other than the proposed action may also have significant impacts on each of these resources.

Difference between the Final and Draft Environmental Impact Statement: Comments were taken both orally and in writing for a period of 60 days on the draft environmental impact statement released in October 1994. The comment period ended December 23, 1994. Substantive comments were responded to both in a question and answer format and/or by making changes, additions or corrections in the text of the draft environmental impact statement. The changed draft is this document, Interior’s final environmental impact statement.

Pg. 2 = pg. 0&i


In the early 1900s, the free-flowing Elwha River on the Olympic Peninsula in Washington State was blocked with two hydroelectric dams (See Figure 1). The Elwha Dam was built 4.9 miles from the mouth of the Elwha River beginning in September 1910. It impounded the reservoir known as Lake Aldwell. Construction on Glines Canyon Dam, 8.5 miles farther upstream, began in 1926, creating the reservoir known as Lake Mills. Although the dams helped in the early development of the peninsula, the presence and operation of the hydropower projects cause severe problems for anadromous fish, the ecosystem, and the Lower Elwha S’Klallam Tribe.

The dams block the migration path for several species of salmon and trout, which, after maturing in the ocean, return to the Elwha to lay their eggs (spawn). Migrating fish such as these are anadromous. The dams also prevent or limit the downstream flow of nutrients, sediment, and woody debris the fish need to successfully spawn and rear juveniles, inundate fish habitat and result in elevated temperatures downstream. The Elwha River was used by 10 runs of salmon and trout before the dams were built. The fish fed more than 22 species of wildlife and were the basis of much of the culture and economy of the Lower Elwha S’Klallam Tribe.

Because of the dams, the flow regime of the river changed from active meandering in many places to less active and more channelized. Reduced sediment supply from the river has caused the eastern edge of the pre-dam Elwha delta to erode, and the barrier beach at Freshwater Bay to recede and steepen. It has also contributed to the erosion of Ediz Hook, the sand spit that protects Port Angeles Harbor.

In recognition of these problems, the Department of the Interior finds, consistent with congressional intent expressed in the Elwha River Ecosystem and Fisheries Restoration Act (P.L. 102-495; see Appendix), a need to fully restore the native anadromous fisheries and Elwha River ecosystem. For the purposes of Elwha River restoration, “full restoration” is interpreted by the Department of the Interior to mean reestablishment of natural physical and biological ecosystem processes, including recovery of the terrestrial and riverine habitat currently inundated by the reservoirs. Since the wildlife habitat and river upstream of the dams are in nearly pristine condition, removing the dams and fully restoring the 10 runs of salmon and trout would fully restore the Elwha River ecosystem. It would also return the cultural and economic focus of the Lower Elwha S’Klallam Tribe, uphold the federal trust responsibility to affected Indian tribes, and provide substantial long term benefits to sport fishing, tourism, and the local economies associated with these activities.

The National Park Service has the lead in preparing this final environmental impact statement, which is a programmatic or policy environmental impact statement. The majority of the March 1993 Federal Energy Regulatory Commission Draft Staff Report was adopted as part of this document. The Elwha Report and its appendixes, prepared by the U.S. departments of the Interior and Commerce and the Lower Elwha S’Klallam Tribe (Jan. 1994), were also incorporated. Material in this document supersedes both that in the Draft Staff Report and in the Elwha Report.

Pg. 3 = pg.ii&iv

If the decision maker, the secretary of the interior; chooses the Proposed Action of removing both dams, the National Park Service will prepare a second environmental impact statement, the “Implementation EIS,” that would examine options for implementing the decision.

Several alternatives for restoring fish habitat are examined in this programmatic impact statement. Only one alternative has the potential to fully restore Elwha native anadromous fisheries—the Proposed Action of removing both the Elwha and Glines Canyon dams. Chances for restoring nine of the ten runs of fish are rated as either “good” or “excellent” if both dams are removed (sockeye salmon suffer from potential stock limitation and habitat problems outside the confines of the Elwha River project and, therefore, have only “poor” to “fair” chances of returning in pre-dam numbers). Removing both dams would also restore natural flow conditions in the Elwha River.

Figure 1. Location Map (Scan)

Because federal agencies examine a full range of reasonable alternatives in an environmental impact statement, the National Park Service also analyzed leaving the dams in place and installing fish passage facilities, as well as removing each dam separately. These alternatives are Dam Retention (with passage facilities installed at both dams), Removal of Elwha Dam, and Removal of Glines Canyon Dam. No Action, or leaving the dams in place without mitigation measures (as they are now), was also analyzed to provide a basis for comparing all action alternatives.

The chances of restoring native anadromous fish drop substantially under each of these alternatives. None of the ten runs has a good or excellent chance of full restoration if fish passage measures are installed (i.e., the Dam Retention alternative) or if Elwha Dam alone is removed. Although there is a good chance that both winter and summer runs of steelhead could be restored if Glines Canyon Dam were removed, the remaining eight runs do not fare as well. For all alternatives except Proposed Action, mortality associated with fish passage and poor habitat is likely to drive the Elwha pink salmon stock to extinction (if it is not already) and chum salmon stock to extremely low levels or extinction.

Anadromous fish populations would return to normal if the dams were removed, and other features of the ecosystem would benefit as well. Natural sediment transport conditions would be reestablished if the dams were removed. This would restore needed spawning gravel and woody debris for fish, and also replace sand missing from the river’s estuary, nearby beaches, and the nearshore environment as far east as Ediz Hook. The estuary would grow to its pre-dam size and once again serve as an important transitional habitat between fresh and salt water for many species of fish and other aquatic organisms. Instead of a stable channel, the Elwha River would return to its active meandering morphology, creating the riffles, pools, and slower moving side channels that many anadromous fish prefer for spawning and rearing.

Draining the reservoirs and returning the river and surrounding land to pre-dam conditions would reduce downstream temperatures in the river; immediately restore more than five miles of stream habitat, and provide access to 70 miles of usable river, greatly benefiting fish. Within three years, revegetation of the reservoir lands would take firm hold; natural succession of a mix of riparian and upland terrestrial habitat would start. Now, 715 acres of potential wildlife habitat are occupied by the reservoirs and dam facilities. If the dams were removed, these acres would return for use by native mammals and other terrestrial species.

Pg. 4 = pg.iv&v

With the reintroduction of salmon and trout throughout the river’s length, wildlife would again benefit from the year-round, stable food source these fish once provided. Threatened or endangered animals such as bald eagles would benefit directly from an increase in available prey, others from the creation of additional habitat. Eventually, restored forest lands would benefit the threatened marbled murrelet and northern spotted owl.

Some negative impacts might occur from the Proposed Action. The dams are considered a historic resource, as they are examples of early hydropower plants. Although important features would be documented and recorded, removal would result in the loss of the dams and power plants. The average annual power produced, 172 gigawatts, or 43% of the power needs for the Daishowa paper and pulp mill in Port Angeles, would also be lost. The reservoirs, which would be drained if the dams are removed, are a recreational resource to flat-water boaters and anglers, as well as winter habitat for the trumpeter swan.

With the dams gone, sediment built up over the last 80 years would be released into the river, though finer sediment could be dredged and removed. If fine sediments (silt and clay) were released uncontrolled, they could kill adult and juvenile fish, their eggs, and other aquatic life. This would be a temporary but severe impact.

Released sediment could also affect surface water users, including the city of Port Angeles and its industrial customers. Several mitigation options are under consideration for analysis in the Implementation EIS, but the Department of the Interior is bound by the Elwha Restoration Act (i.e. the Elwha River Ecosystem and Fisheries Restoration Act; PL 102-495) to ensure that municipal and industrial users are protected from adverse impacts to existing water quality and availability that might occur if the dams were removed.

If the dams were removed and upstream sediment flowed into the middle and lower river, the riverbed itself might rise to pre-dam levels, which has been estimated to be on the order of 1 to 5 feet above the present level. A raised riverbed would raise the water level also, and localized flooding could occur more frequently.

In addition to achieving the congressionally mandated goal of restoring both the native anadromous fisheries and ecosystem, the Proposed Action would have long-term positive impacts on the local economy through increases in tourism, commercial and recreational fishing; river recreational access; improvement of esthetics; uncovering of tribal cultural resources now buried or inaccessible; and aiding the very depressed tribal economy. Any potential safety risk posed by the dams (although now considered safe, earthquake risk is being reexamined) would be eliminated. The volume of water currently available to users, and high flow volumes (i.e., large floods) would remain the same as now, as the dams have a very limited ability to store water.

Pg. 5 = pg.v&vi

The following discussion summarizes environmental problems that each alternative might create for a particular resource (such as water quality). A comparison of impacts, or the extent of these problems, for each alternative is located in chart form beginning on p.22 of this document.

Summary of Issues

Issues are environmental problems which might occur if the Proposed Action or any of the alternatives are undertaken. The expected extent of these problems is called impact. Impact analyses predict how severely a particular environmental resource (i.e., water quality) would be affected with implementation of each alternative. A description of issues follows; impacts are discussed in the chapter titled “Impacts of Each Alternative”.

Geology, River Morphology, Hydrology & Water Quality

The dams have limited coarse-grained sediment and woody debris from flowing downstream of river mile 13.4, the location of Glines Canyon Dam. As a result, cobbles, gravel, and sand have built up in deltas where the river or tributaries enter the reservoirs. Salmon and trout are denied the spawning gravel needed to successfully reproduce. Erosion of coastal features such as Ediz Hook and beaches near the mouth of the river is exacerbated.

Approximately 17 million cubic yards of clay, silt, sand, gravel, and cobbles are now (1994) trapped in the two reservoirs, most behind Glines Canyon Dam. Some portion of this sediment would be released into the river should the Proposed Action or single dam removal alternatives be implemented. The Elwha Report investigates three ways to manage this sediment: (1) eroding the material to the Strait of Juan de Fuca, (2) mechanically removing the material by dredging and slurrying to either a terrestrial or saltwater site, or (3) stabilizing the sediments within the confines of the existing reservoirs.

Any of these options for implementing the Proposed Action would return gravel and help halt erosion of coastal features over time. However, each may have different short-term impacts to both fisheries and water quality.

The erosion option would supply material to the river, but would also have a potentially adverse impact on water quality and on spawning or rearing fish through the release of fine-grained sediment (silt and clay). The stabilization and removal options would not have these impacts to the same degree, but restoring spawning gravel would take longer. Removing only Elwha Dam would allow the release of a relatively small amount of sediment (2 to 3 million cubic yards; or one-half to two-thirds of the total 4 million cubic yards estimated behind Elwha Dam) into a relatively short section (4.9 miles) of river. This material would wash out to the strait and not be replenished since Lake Mills would continue to trap upstream sediment. Removing only Glines Canyon Dam would release a larger volume (7-9 million cubic yards; or one-half to two-thirds of the total approximately 13 million cubic yards behind Glines Canyon Dam) of sediment into the middle river. Until Lake Aldwell filled, this material would be trapped behind Elwha Dam. However, sediment eventually would pass through the penstocks and over the spillways of Elwha Dam and flow into the lower river and nearshore marine environment.

Pg. 6 = pg. vii&viii

Removal of both dams would positively affect native anadromous fish by returning spawning gravels throughout the lower and middle Elwha River, lowering water temperatures, and restoring fish habitat. Returning anadromous fish would also cause changes to river water over the long term through the addition of organic material and nutrients such as phosphorus and nitrogen. Biological productivity would increase as a result.

Water users could be affected by silt and clay for a short time, but the Elwha Restoration Act requires mitigation for adverse impacts to municipal and industrial users.

Water quality may also change over time. Although a portion of suspended sediment now flows over the dams and downstream, removing the dams would result in a larger fraction of this finer material being transported to the middle and lower river and out to sea. However, since elevated turbidity levels from the natural river would generally occur only during high flow periods, there would be little if any noticeable effect during low flow periods.

Releasing stored sediment behind either or both dams would also cause the riverbed to “aggrade” or rise in some places. This would elevate river levels as well, possibly causing more frequent localized flooding.

  1   2   3   4   5   6   7   8   9   ...   37

Добавить в свой блог или на сайт


Final Environmental Impact Statement iconDraft environmental impact statement

Final Environmental Impact Statement iconDraft Environmental Impact Statement

Final Environmental Impact Statement iconDecision Regulation Impact Statement

Final Environmental Impact Statement iconAn Environmental Impact Study of Paddy Cultivation within Katagamuwa Sanctuary

Final Environmental Impact Statement iconImpact of environmental pollution on the preservation of archives and records: a ramp study

Final Environmental Impact Statement iconImpact of wind resources and environmental regulations to future generation portfolio and its capacity factor in ercot

Final Environmental Impact Statement iconEnvironmental impact report no. 97-2 (Continued From September 10, 2002 With Public Hearing Closed) (Parkside Estates)

Final Environmental Impact Statement iconNew real time risk indicators to improve the efficiency, environmental impact and safety of air traffic management

Final Environmental Impact Statement iconFinancial statements Income statement Balance sheet Statement of cash flows Statement of changes in equity Notes to and forming part of the financial report

Final Environmental Impact Statement iconRegulation Impact Statement for the Fuel Standard (Petrol) Determination 2001 and the Fuel Standard (Diesel) Determination 2001

Разместите кнопку на своём сайте:

База данных защищена авторским правом © 2012
обратиться к администрации
Главная страница