National Program for Inspection of Non-Federal Dams. Nash Pond Dam (CT 00060), Southwestern Coastal Basin, Westport Connecticut. Phase I Inspection Report PDF Download
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Author: CORPS OF ENGINEERS WALTHAM MA NEW ENGLAND DIV.
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Category :
Languages : en
Pages : 83
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Book Description
The dam at Nash Pond is constructed of stone masonry, is approximately 105 feet long, 25 feet high and has a top width of 5 to 7 feet. There have been no significant modifications to the dam since the dam was completed in 1879. The impounded water is primarily used for recreation. The present owner of the dam could not be determined during this report and it is recommended that the State of Connecticut ascertain the ownership of the dam. Based on the visual inspection and past operational performance, the dam is judged to be in FAIR condition. Slight seepage from the masonry joints was noted on the downstream face and some of the joints need repointing. The valve controlling discharge to the 30 inch pipe outlet self-opened in the Summer of 1978 and was subsequently reclosed. A low-level blowoff is believed to exist through the base of the dam. This dam is classified as SMALL in size and a HIGH hazard potential structure in accordance with recommended guidelines established by the Corps of Engineers. The impoundment storage at the top of the dam is 114 ac.-ft. and the maximum height of the dam is 25 feet. Failure of the dam would result in the loss of more than a few lives and excessive economic loss to the downstream urbanized area, two commercial buildings, 2 - 3 residential homes, and an apartment building. The test flood for this dam is 1/2 the Probable Maximum Flood (PMF). The test flood has an inflow equal to 2650 cfs and an outflow discharge equal to 2570 cfs with a stillwater elevation of 64.0 which will overtop the dam by 3.8 feet in a stillwater condition. The maximum outflow capacity of the spillway under stillway conditions is 250 cfs which is 10 percent of the test flood.
Author: CORPS OF ENGINEERS WALTHAM MA NEW ENGLAND DIV.
Publisher:
ISBN:
Category :
Languages : en
Pages : 83
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Book Description
The dam at Nash Pond is constructed of stone masonry, is approximately 105 feet long, 25 feet high and has a top width of 5 to 7 feet. There have been no significant modifications to the dam since the dam was completed in 1879. The impounded water is primarily used for recreation. The present owner of the dam could not be determined during this report and it is recommended that the State of Connecticut ascertain the ownership of the dam. Based on the visual inspection and past operational performance, the dam is judged to be in FAIR condition. Slight seepage from the masonry joints was noted on the downstream face and some of the joints need repointing. The valve controlling discharge to the 30 inch pipe outlet self-opened in the Summer of 1978 and was subsequently reclosed. A low-level blowoff is believed to exist through the base of the dam. This dam is classified as SMALL in size and a HIGH hazard potential structure in accordance with recommended guidelines established by the Corps of Engineers. The impoundment storage at the top of the dam is 114 ac.-ft. and the maximum height of the dam is 25 feet. Failure of the dam would result in the loss of more than a few lives and excessive economic loss to the downstream urbanized area, two commercial buildings, 2 - 3 residential homes, and an apartment building. The test flood for this dam is 1/2 the Probable Maximum Flood (PMF). The test flood has an inflow equal to 2650 cfs and an outflow discharge equal to 2570 cfs with a stillwater elevation of 64.0 which will overtop the dam by 3.8 feet in a stillwater condition. The maximum outflow capacity of the spillway under stillway conditions is 250 cfs which is 10 percent of the test flood.
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Category : Science
Languages : en
Pages : 540
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Author: CORPS OF ENGINEERS WALTHAM MA NEW ENGLAND DIV.
Publisher:
ISBN:
Category :
Languages : en
Pages : 73
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Lee's Pond Dam is a stone masonry dam approximately 200 feet long and 17 feet high. The overflow spillway is 180 feet long and is 5 feet below the top of the dam. A 6'x9' sluice gate is located 50 feet from the west abutment. Adjacent to the sluice gate is a fish ladder. Both the sluice gate and the fish ladder were added after the dam was constructed. The drainage area is 77.5 square miles and the pond has 152 acre-feet of available storage. The assesement of the dam is based on the visual inspection, available drawings, past operational performance and hydraulic/hydrologic computations. The dam is judged to be in poor condition with several areas that require attention. These areas include seepage through both abutments and the stone masonry and the undermining and advanced stage of deterioration of the spillway apron and the scour hole at the end of the sluice gate outlet. The dam is classified as small and has a low hazard potential in accordance with guidelines established by the Corps of Engineers. The test flood outflow for this dam is 8,460 cfs and corresponds to the 100-year flood. The test flood outflow will not overtop the dam.
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Category : Government reports announcements & index
Languages : en
Pages : 1152
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Author: CORPS OF ENGINEERS WALTHAM MA NEW ENGLAND DIV.
Publisher:
ISBN:
Category :
Languages : en
Pages : 121
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The entire structure is 235 feet long and consists of a 90-foot-long, 14-foot-high earth embankment extending from the right abutment, a 25-foot-long, 10-foot-high concrete broad-crested spillway weir, and a 120-foot-long 14-foot-high embankment span between the spillway and the left abutment. The top of the embankment is approximately 14 feet wide and is 4 feet above the spillway crest elevation of 327 NGVD. The outlet facilities consist of a 24-inch gated conduit at the base of the concrete spillway and an 18-inch ungated conduit in the left embankment. Visual inspection of the dam indicated that the dam is in poor condition. The inspection revealed considerable spalling and efflorescence of the spillway training walls, an inoperable low-level outlet, heavy vegetation on the dam, and evidence of seepage along the toe of the embankments. The test flood outflow is approximately 1,670 cfs; and the capacity of the spillway, with the water surface at the top of the dam, is 620 cfs or 37 percent of the routed test flood outflow. Therefore, the dam will be overtopped by about 1.2 feet.
Author: CORPS OF ENGINEERS WALTHAM MA NEW ENGLAND DIV.
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ISBN:
Category :
Languages : en
Pages : 113
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Park Pond Dam, located at the eastern end of the pond, consists of an earth embankment with a maximum height of 20 feet and a top width which varies from 8 feet to 15 feet. The dam is 420 feet long and has a 19.9 foot concrete spillway at the left end. A diversion channel from an adjacent watershed connects to the spillway approach channel. The impoundment has a maximum storage capacity of 1,100 Acre-Feet. The dike, located at the northwestern end of the pond, consists of an earth embankment with a paved roadway along the crest. The dike has a maximum height of 7 feet, a top width of 21 feet, and a length of about 80 feet. Based on the visual inspection, the dam is judged to be in poor condition and the dike in fair condition. Features which could affect the future integrity of the dam are trees and brush on the embankment; seepage through the embankment; erosion of the downstream slope; deterioration of the spillway approach channel wall and the spillway weir; the accumulation of debris in the spillway and approach and discharge channels; the location of the low level control valve downstream of the dam and lack of erosion protection on the dike. The spillway capacity with water level at the top of the dam and the dike is 310 cfs or 58 percent of the Test Flood routed outflow. The Test Flood would overtop the dam and dike by 0.3 feet.
Author: CORPS OF ENGINEERS WALTHAM MA NEW ENGLAND DIV.
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ISBN:
Category :
Languages : en
Pages : 112
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This dam is an earth embankment structure with a steel sheet pile core. It is approximately 650 feet long, 24 feet high with a top width of 15 feet and has a centrally located 200 foot long spillway. The original dam was built about 1890 and was substantially expanded to its present configuration in 1965. The official name of the impoundment created by the dam is Pope's Pond, although it is also known as Streets Pond as shown on the USGS maps. Based on the visual inspection, review of construction plans and past operational performance, the dam is judged to be in FAIR condition. Minor seepage was noted on the downstream face of the east embankment. Some vegetation was noted in the joints of the spillway. The single control valve for the by-pass pipe is on the downstream side of the dam. The test flood for this dam is the Probable Maximum Flood (PMF). The test flood has an inflow equal to 4575 cfs and an outflow discharge equal to 4475 cfs at a stillwater elevation of 371.5 which will not overtop the dam (1.5 feet freeboard). The maximum outflow capacity of the spillway under a stillwater condition is 7600 cfs, which is 170 percent of the test flood.
Author: CORPS OF ENGINEERS WALTHAM MA NEW ENGLAND DIV.
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ISBN:
Category :
Languages : en
Pages : 88
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The Thurston Pond Dam, also known as the New Dam, consists of an earth embankment with a stone masonry overflow spillway located at the right end of the dam, and outlet works located at the right abutment. The total length of the dam, including the spillway section, is 510 feet and the maximum height is 20 feet. The stone masonry overflow spillway section has an upstream earth embankment of unknown section, a concrete cap and a batter of 6 inches per vertical foot on the downstream face. The outlet works consist of a concrete intake structure with inlet and outlet gates which can discharge water through a 24-inch concrete pipe to downstream locations or through an 18-inch concrete pipe into the stream below the dam. The dam impounds Thurston Pond, which is used for industrial water supply. Based on the visual inspection, the dam is judged to be in poor condition. Features that could affect the future integrity of the dam are continued erosion of the earth embankment, the presence of trees on the dam, the deterioration of the stone masonry overflow spillway, and inadequate spillway capacity to pass the Test Flood Outflow. The spillway capacity is 2,500 cfs or 37 percent of the Test Flood Outflow.
Author: CORPS OF ENGINEERS WALTHAM MA NEW ENGLAND DIV.
Publisher:
ISBN:
Category :
Languages : en
Pages : 67
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Parks Pond Dam is a cyclopean masonry/earth embankment that is approximately 180 feet long and 12 feet high. The earth embankment is on the downstream side and has a 2:1 slope. The upstream face is cyclopean masonry with a vertical face. The spillway is located on the southern half of the dam and consists of a 30.5 foot long weir. There is a lower gate house for the control of a discharge pipe that passes through the base of the dam. The size of the pipe is unknown. The valve for the operation of the discharge pipe is inoperable. The drainage area is 0.5 square miles and the reservoir has 100 acre-feet of available storage. The assessment of the dam is based on the visual inspection, past operational performance and hydraulic/hydrologic computations. The dam is judged to be in poor condition with several areas that require attention. These areas include seepage through the dam and around the spillway's west training wall, deteriorated concrete of the spillway and upstream face of the dam, vegetation on the embankments and along the toe of the dam and the nonoperating status of the blowoff. The dam is classified as small and has a significant hazard potential in accordance with guidelines established by the Corps of Engineers. The test flood for this dam is 1/2 the Probable Maximum Flood (PMF). The test flood inflow is 625 cfs and the routed test flood outflow is 473 cfs. The test flood outflow will overtop the dam by 0.55 feet.
Author: CORPS OF ENGINEERS WALTHAM MA NEW ENGLAND DIV.
Publisher:
ISBN:
Category :
Languages : en
Pages : 82
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The Whist Pond Dam consists of an earth embankment with a maximum height of 9 feet, and a total length of 1,100 feet including a 17.7 foot long overflow spillway located at the right end of the dam. The outlet works consist of a 12-inch cast iron low level diversion outlet pipe through the dam, controlled by a downstream gate valve. The dam impounds Whist Pond, a storage reservoir for public water supply of the Torrington Water Company. Based on the visual inspection and a review of all available pertinent data, the dam is judged to be in fair condition. The future integrity of the dam can be affected by continued slumping of the rip-rap, roots through the embankment, continued deterioration of the spillway weir and training walls, the lack of a defined spillway discharge channel, and the downstream location of the low level diversion outlet valve. The calculated Test Flood inflow of 175 cfs results in a routed outflow of 65 cfs and 0.4 feet of freeboard. The spillway has a capacity of 100 cfs and is capable of discharging 154 percent of the Test Flood routed outflow.
