National Program for Inspection of Non-Federal Dams. Lancaster Millpond Dam MA 00887, Merrimack River Basin, Clinton, Massachusetts. Phase 1 Inspection Report

摘要

Lancaster Millpond Dam is a stone-masonry structure with stone abutments. It is 490 feet long and has an estimated hydraulic height of 24.5 feet. The spillway is 190 feet long and discharges to the Nashua River. As a result of the visual inspection and a review of available data, Lancaster Millpond Dam is considered to be in fair condition. Major concerns are: erosion of the soil near the right abutment on the downstream side; trees growing on the soil of the right abutment and on the field nearby; a tree growing out of the stone masonry at the intersection of the dam and the left training wall; seepage through the spillway; and the lack of controls on diversion and discharge structures. The test flood inflow was estimated to be 14,800 cubic feet per second (cfs) and resulted in an outflow discharge estimated to be 14,800 cfs, which would overtop the dam crest by about 13 feet. This would result in the water rising to within about 1 foot of the bridge at State Routes 62 and 70 immediately upstream of the dam.