Carters Dam and Lake, Coosawattee River, Georgia
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FINAL NVIRONM NTAL STAT M NT CART RS DAM AND LAK COOSAWATT RIV R, G ORGIA Prepared by U. S. Army ngineer District, Mobile Mobile, Alabama April 1974 s t a t e m e t o f f i d i g s Carters Dan and Lake Coosawattee River, Georgia As District ngineer, Mobile District, Corps of ngineers, it is my duty as the responsible Federal Official to prepare plans and specifications and an nvironmental Statement for the completion of the construction and operation of Carters Dam and Lake, Coosawattee River, Georgia. In this respect, I have reviewed and evaluated, in light of the overall public interest, the documents concerning the proposed action; the pertinent data contained and referenced in the nvironmental Statement describing the effects of the proposed activity; and the stated views of other interested agencies and the concerned public. In evaluation, I have studied and analyzed the plan for the Carters Dam and Lake project. I have considered the engineering problems, the social and economic factors involved and the environmental consequences of the action. The adopted plan for Carters Dam and Lake project is believed to be the best alternative from an engineering point of view. Completion of the construction and future operation of the project will provide both social and economic benefits to the people of the area. The nvironmental Impact Statement has been prepared and coordinated with appropriate Federal and State agencies in compliance with the spirit and intent of the National nvironmental Policy Act of 1969. As indicated in the statement, completion of construction of the dam and lake will result i In the loss of 4,250 acres of agricultural and forest land and associated wildlife habitat, plus the loss of a section of free-flowing stream and its inhabitants. These adverse effects are more than offset by the beneficial aspects of flood control, a peaking hydroelectric power plant, and improved recreational opportunities that will result from the operation of the project. Based on the above criteria and evaluation, I find that the adverse effects of the project are outweighed by other considerations of social and eco nomic benefits; that the recommended action is consonant with National policy, statutes, and administrative directives; and that the total public interest should best be served by construction of the project. Date DRAK WILSON Colonel, C District ngineer I have reviewed the Statement of Findings and concur with the recom mendations of the District ngineer. /Date f CARHDLL ij. LeT LLI R . Brig^die/ General, USA Division ngineer I concur with the preceding Statement of Findings. Da ik J. W> M O R R I S ' /lajor General, USA 'Director of Civil Works Carters Dam and Lake, Coosawattee River, Georgia ( V Draft (X) Final nvironmental Statement Responsible Office; U. S. Army ngineer District, Mobile, Alabama 1. Name* of Action; (X) Administrative ( ) Legislative 2. Description of Action: Complete construction and place in opera tion an authorized multipurpose reservoir project on the Coosawattee River in Murray, Gilmer, and Gordon Counties, Georgia. Hie project is being constructed for the purposes of flood control, hydroelectric power and recreation. 3a. nvironmental Impacts: Conversion of 4,250 acres of agricultural and forest lands to a lake environment; loss of free-flowing stream habitat; provide flood protection; produce peaking'hydroelectric power; and provide high quality recreation. b. Adverse nvironmental ffects: Loss of 4,250 acres of agricultural and forest land and its associated wildlife habitat, plus loss of a section of free-flowing stream and disruption of its inhabitants. 4. Alternatives; Terminate construction. 5. Comments Received; State Coordinator, State of Georgia Department of the Interior Department of Agriculture Department of Transportation Department of Housing and Urban Development nvironmental Protection Agency Office of conomic Opportunity University of Georgia, Department of Anthropology 6. Draft statement to C Q 30 November 1972 . *DEC 19 4 7. Final Statement to C Q __________________ . FINAL NVIRONM NTAL STAT M NT CART RS DAM AND LAK COOSAWATT RIV R, G ORGIA Table of Contents Section Subject Page No. 1 Project Description ---------------- \ 2 . nvironmental Setting Without the Project ----- 5 3 The nvironmental Impact of the Proposed Action — 13 4 Any Adverse nvironmental ffects Which Cannot be Avoided --------------------- 20 5 Alternatives to the Proposed Action -------- 21 6 The Relationship Between Local Short-term Uses of Man's nvironment and the Maintenance and nhancement of Long-term Productivity ------ 23 7 Any Irreversible and Irretrievable Commitment of Resources Which Would Be Involved in the Proposed Action ------- -- --— 24 8 Coordination with Others ------------- 25 List of Tables Table No. Subject Page No. 1 Pertinent Data on Carters Dam Project ------- 4 List of Plates Plate No. Title Follows 1 Location Map of Carters Dam, Georgia ------- Page 35 2 Project Location Map -——— - -------- — Plate 1 List of Appendices APP NDIX A Review Comments on Draft Statement APP NDIX B Water Quality and Biological Changes Following Impound ment APP NDIX C Temperature Simulation Study Lake Carters, Georgia APP NDIX D Bibliography FINAL NVIRONM NTAL STAT M NT CART RS DAM AND LAK COOSAWATT RIV R, G ORGIA 1.01 Project Description. The development of the Coosawattee River was authorized as a part of the ultimate plan for the Alabsma-Coosa River System by the River.and Harbor Act adopted 2 March 1945. This portion of the overall development consists of the construction and operation of a multiple purpose dam on the Coosawattee River, 26.8 miles above its juncture with the Conasauga River, near Carters, Georgia. The site is approximately 60 miles north of Atlanta, Georgia, and 50 miles southeast of Chattanooga, Tennessee. Portions cf Murray, Gilmer, and Gordon Counties are included in project implementation. A map showing the location of the project is attached (Plate 1). 1.02 Construction at Carters began in April of 1S62 and as of 28 Febru ary 1974 the overall project was about 82 percent complete. The main rockfill dam, the penstocks, the intake structure, the emergency spillway, and the reregulation dam are essentially complete. Construction of the emergency low level sluice and the powerhouse are 78 and 61 percent complete, respectively, as of 28 February 1974. The project is presently scheduled to be fully operational by October 1975. 1.03 The primary project purposes are flood control, hydroelectric power and recreation. The project has a benefit-to-cost ratio of 3.5 to 1 as of 1 January 1974. 1.04 The structures at Carters Dam will consist of the following princi pal features: (a) Main rock-fill dam, (b) gated emergency spillway, (c) powerhouse, (d) intake structures, (e) four penstocks, (f) emergency low level sluice, (g) reregulating dam, and (h) three saddle dikes. 1.05 The main dam is a rolled-rock and earth fill structure. It has a length of 1,955 feet along the arch of the axis with a radius of 2,100 feet. The height of the dam is 455.3 feet. The 40-foot-wide crest was constructed to elevation 1,112.31/ which is to provide a 5-foot freeboard above the spillway design flood. The upstream slope is 1 vertical to 1.9 horizontal and the downstream slope is 1 vertical to 1.8 horizontal. Seepage control is provided by curtain grouting. Impervious fill was placed on a clean firm rock foundation. A roadway will be provided across the dam for access to the power intake structure and the public overlook areas. 1.06 The gated emergency spillway is a concrete gravity-type structure 262 feet long, consisting of five gate bays 42 feet wide, four intermedi ate piers 8 feet wide, and two end piers 8 feet wide. The spillway crest is at elevation 1,070. Flow will be controlled by five tainter gates. 1.07 The powerhouse will be located on the right bank about 200 feet below the downstream toe of the main dam and 700 feet northward from the river channel. It will be a reinforced concrete structure 117 feet wide and 331 feet long. The powerhouse will be equipped with four 125 MW (two 172 Khp and two 173 Khp) turbine-generators; two of these will have pump capability (4,435 c.f.s. each). The switchyard will be located adjacent to the power house. 1.08 Four reinforced concrete Intake structures are located about 400 feet northwest of the main dam with the top at elevation 1,112.3, the same as the crest of the dam. These structures include four headgates which will be operated by fixed hoists, trash racks and stop logs. Four 18-foot- diameter, steel lined penstocks will connect the intakes to the powerhouse. 1.09 The emergency low level sluice will be located in the left abutment and will consist of an intake structure, an upstream tunnel, a gate struc ture and shaft, a downstream tunnel, and an exit channel. 1.10 The reregulating dam consists of earth dikes on each side of a con crete structure. The concrete structure includes four gated-spillway bays, non-overflow sections for dike wrap-around and a control house. A spillway bridge over the vpillway bays provides for placement of stop- logs. Flow will be controlled by four 42-foot-wide end 36.5-foot high tainter gates. The sill is at elevation 662.5. 1.11 Three earthfill dikes with a total length of about 900 feet were required on the left bank rim of the main reservoir about 6,000 feet upstream from the main dam. The dikes, with a maximum height of about 40 feet will have a top width of 25 feet at elevation 1,112.3 and side slopes of 1 on 2.5.