Jefferson River at Three Forks, Montana
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FINAL ENVIRONMENTAL STATEMENT JEFFERSON RIVER AT THREE FORKS, MONTANA Prepared by U.S. ARMY ENGINEER DISTRICT, OMAHA, NEBRASKA December 1971 Jefferson River at Three Forks, Montana ( ) Draft (X) Final Environmental Statement Responsible Office: U.S. Army Engineer District, Omaha, Nebraska 1. Name of Action: (x) Administrative ( ) Legislative 2. Description of Action: The proposed project would consist of the construction of an earth filled levee and a drainage collector ditch approximately lU ,700 feet in length along the northwest side of a small community. The location is at Three Forks in Gallatin County, Montana. 3. a. Environmental Impacts; Flood protection would be provided for a flood having a frequency of occurrence of once in a 100 years. A 28 acre loss of alternate land use would be required for levee alignment. A possibilit would exist for pollutants from adjacent land to accumulate in the collector ditch. A potential would exist for the collector ditch to develop aquatic growth. Five hundred feet of shelterbelt would be lost to levee construction. b. Adverse Environmental Effects: Construction would effect the removal of 28 acres of land from alternative land use; collector ditch could act as a collector of pollutants; and construction of the levee would necessitate the removal of 500 feet of shelterbelt. Alternatives; Floodplain zoning, evacuation, flood proofing, reservoir construction, channel improvement, and ”no development” were considered. 5• Comments Received: City of Three Forks Bureau of Sport Fisheries & Wildlife, USDI Montana Department of Fish Bureau of Reclamation, USDI and Game Bureau of Outdoor Recreation, USDI Montana Department of Health Environmental Protection Agency, USEPA Montana Highway Commission Bureau of Mines, USDI Soil Conservation Service, USDA Montana Water Resources Board National Park Service, USDI 6. Draft statement to CEQ 22 March. 1211. Final statement to CEQ I. Project description. The proposed Jefferson River flood control project at Three Forks, Montana was studied tinder authority of Section 205 of the Flood Control Act, approved 30 June 191*8, as amended by Section 205 of the Flood Control Act, approved 23 October 1962. The proposed project would consist of a compacted earth fill levee with a 10-foot top width and one on three side slopes. It would be approximately lU,700 feet long and be constructed on the northwest side of Three Forks to protect the town against over'oank flows from the Jefferson River. Project location and features are shown on plate 1. The levee would average 6 to 7 feet in height, including 3 feet of freeboard above the design water surface for a flood having an average frequency of occurrence of once in a 100 years. A small portion of the material for the construction of this levee would be obtained from the excavation of a collector ditch along the landside of the levee. The bulk of the random materials necessary for preparation of the levee core would be obtained from either young alluvium in the river valley or older allivium deposits on the valley slopes nearby. The collector ditch would traverse practically all of the levee alignment and would average 15 feet in width and 1 1/2 feet in depth. It would serve as a collector for runoff occurring on the landside of the proposed levee. The town of Three Forks has a borrow pit in proximity to the proposed levee, and severed other borrow pits, opened for construction of Interstate Highway 90, are available nearby. The proposed flood control project for Three Forks, Montana is under review by higher authority. The benefit-cost ratio for this project was estimated to be 1.1) to 1. It was amortized over a 50 year period at an interest rate of U.875 percent. II. Environmental setting without the project. The entire town of Three Forks lies between the Jefferson and Madison Rivers. This is about 3.5 miles upstream from the confluence of the Jefferson, Madison and Gallatin Rivers, which marks the beginning of the Missouri River. Historically, the town has not been subjected to frequent flooding from the Jefferson River, but because of the broad, flat natui**“Of the floodplain, the threat of flooding exists. The floodplain lands surrounding the town are agricultural, consisting mostly of hay and pasture lands. The area is semiarld which requires some of the agricultural land in the valley to be irrigated by a system of canals and ditches drawing water from the Jefferson River. The water table throughout a large portion of this basin lies within 8 to 10 feet of ground surface; seeps and springs are a common occurrence. The Jefferson River, like most of the streams in the area, supports a good trout fishery. Major fish species found along this stretch of the Jefferson River include rainhov and brown trout, mountain whitefish, suckers, dace, carp and mottled sculpin. The channel banks and adjacent lowlands abound in excellent vegetation which provides cover and needed shade to maintain cold water temperatures necessary for the protection and perpetuation of this fishery. Major plant types found in this area consist primarily of snowberry, willow, cottonwood, red dogwood, wild rose and buffalo-berry. Grasses of significance include cheatgrass, Junegrass, western wheatgrass and needlegrass. As a composite, these vegetative communities provide prime ■* feeding, resting, nesting and escape cover areas for deer, rabbits, marsh furbearers, pheasants and other species of upland game birds and song birds indigenous to the project area. The town of Thr«e Forks is currently discharging untreated sewage into the Jefferson River via Jefferson Slough. This is the result of an inadequate sewage lagoon constructed in 1962. A new treatment facility is in the planning stage. Other forms of environmental pollutants are evident. A large livestock feeding operation is located adjacent to the proposed levee in the northwest part of town. No facilities have been provided for disposal of associated animal wastes. Obnoxious odors originate from this facility and from an egg production plant adjacent to it. Large dust plumes are evident as they discharge from the stacks of a talc plant located in the town of Three Forks and from a cement plant located at Trident which lies five miles to the east. The town garbage dumo lies adjacent to the livestock feeding operation and adjacent to the proposed levee site. Although garbage is presently being burned here, this site is to be converted to a sanitary landfill in the future. Three Forks is surrounded by scenic and historic sites, although none fall within the immediate boundaries of the proposed flood control project. Ill. The environmental impact of the proposed action. A. Impacts Identified. 1. Flood control provided for a 100-year frequency flood. 2. A potential for establishing wildlife habitat along collector ditch. 3. Alternative land use vonld be lost on the 28 acres required for levee alignment. U The collector ditch could transfer a portion of the existing pollution problems to the Jefferson Slough. 5. There would be 500 feet of recently planted shelterbelt lost. B. Beneficial impacts discussed. 1. The project would control a 100-year frequency flood, thereby reducing the undesirable effects of flooding. These undesirable aspects go beyond the monetary losses of property and include deposition of water, silt, debris and waste which, in turn, create conditions favorable to the increased propagation of mosquitoes, flies and other pests and associated disease carriers. They also include psychological factors such as the anxiety created by the threat of flooding and the despair of seeing homes and property damaged or destroyed. In addition to reducing the undesirable effects, the project should provide added incentive to the local citizenry to maintain and improve their properties, and provide the impetus necessary to further improve the existing environment of the area by control of air and water pollutants. 2. A potential for wildlife habitat exists along the collector ditch. Under dry conditions the replanted vegetative growth would be readily available for gallinaceous birds. However, in the event a portion of the collector ditch develops a wet condition, in the form of a seepage or permanent flow, then the possibility exists for an aquatic habitat to develop that would favor marsh animals. The hydrological study indicated a wet condition is highly improbable. Nevertheless, many of the existing road ditches, borrow sites and lowlands in the immediate area are saturated with groundwater and support aquatic plant growth. The collector ditch would, even with water in the ditch, reduce mosquito reproduction by draining a number of existing puddles along the area of levee alignment. C. Detrimental impacts discussed. 1. The levee and collector ditch would remove 28 acres from alternative land use. The area currently provides medium grade pasture. 2. The collector ditch along the landside of the levee would serve as a vector for concentration of pollutants originating along the project alignment. This could result in concentrated pollution discharges into the Jefferson Slough downstream of the project. A review of the hydrological study indicated that very little runoff would occur behind the levee, so that the volume of polluted water entering the river via the slough would most likely be small. In any event, the proposed project would cause little change in the total volume of polluted water ultimately reaching the river. Groundwater pollution at a depth that would affect the town’s potable water supply has not been recorded to date by the Montana Health Department. Since the proposed project would most likely result in the faster transport of drainage water from the area, groundwater pollution should not be a problem. In fact, it is possible that less groundwater pollution would occur. However, with or without the project, pollution sources will remain until control action is taken locally.