COST OF HYDRO-ELECTRIC POWER PLANTS 731 



ESTIMATE OF 72,000-Kw. GENERATING STATION AT GREAT FALLS, 

 POTOMAC RIVER, FOR SUPPLYING LIGHT AND POWER FOR THE 

 USE OF UNITED STATES AND THE DISTRICT OF COLUMBIA 



(From H. R. Document No. 1400) 



This proposed project provides for a dam across the Potomac 

 River at Great Falls, creating a lake or reservoir of some 3000 acres 

 area and an operating head of 111 feet. The dam is in two 

 parts, a spillway dam and an intake dam. The former is of 

 the arched type, somewhat similar to the spillway section of the 

 Gatun dam, at Panama, and comprises eighteen openings sepa- 

 rated by piers and provided with Stoney gates. A gatehouse is 

 arranged for on top of the intake dam, from which nine pen- 

 stocks convey the water to the turbines. These are of riveted 

 steel from f to J-inch thickness, the inside diameter being 13 feet 

 and the length 140 feet. 



When completed the equipment will comprise nine 12,500- 

 H.P. single-runner vertical turbines operating at 150 R.P.M. 

 under a head of 111 feet. These will drive nine 10,000-Kv.A. 

 (8000 Kw. .8 P.F.) 3-phase, 60-cycle, 13,209-volt generators, with 

 direct-connected exciters. Provision is further made for com- 

 plete switching equipment and station auxiliaries. 



The allowance in the original estimate for relocating the Ches- 

 apeake and Ohio Canal has been omitted in the following: 



ESTIMATED COST 

 Spillway dam : 



Piers, superior concrete, 7540 cubic yards, at $9.00 $67,000 



Piers concrete, 27,800 cubic yards, at $8.00 222,000 



Water-flow guides, concrete, 1850 cubic yards at $8 15,000 



Dam, superior reinforced concrete, 37,400 cubic yards, at $9 337,000 



Dam, cyclopean superior concrete, 36,200 cubic yards, at $5.50*. . 200,000 



Dam, cyclopean concrete, 233,550 cubic yards, at $4.50 * 1,050,000 



Total masonry $1,891,000 



Excavation, rock, 115,400 cubic yards at $2.50 289,000 



Stoney gates, 18, erected, weight 1,162,000 pounds, at $0.08 130,000 



. Stoney gates, fittings and machinery, etc., 18 sets at $6500 117,000 



Floating caisson ' 5,000 



Foot bridge, erected, weight 833,000 pounds, at $0.08 65,000 



Railing, 2850 feet, at $1.75 5,000 



Total spillway dam ,. . . $2,502,000 



