National Program for Inspection of Non-Federal Dams. Old Grist Mill Pond Dam (MA 00668), Blackstone River Basin, Upton, Massachusetts. Phase 1 Inspection Report.

摘要

The dam is an earthfill embankment 90 feet long and 24 feet high with concrete headwalls on the upstream and downstream slopes. There is a concrete outlet structure located on the upstream face of the dam. The structure contains three weirs and a grated outlet. The following are visible signs of distress which indicate a potential hazard at the site: erosion and spalling of the concrete on the outlet structure; slight seepage at the top of the outlet gate; slight seepage at the toe of the dam; a small tree growing at the toe of the dam; erosion of the embankment slopes near the west abutment; accumulation of rock debris in the floor of the box culvert; and minor efflorescence, cracking and seepage in the walls of the box culvert. In addition, the channel downstream of the dam contains heavy overgrowth of trees and brush, an accumulation of rock and soil 2 feet above the floor of the box culvert, and pieces of rock fallen from the side walls. The outlet structure can only discharge 29 percent of the test flood before overtopping the dam occurs. In the event flow overtops the dam, complete failure of the dam is unlikely to occur. The highway pavement and concrete headwalls will serve to protect the dam under flood conditions. However, erosion of the dam could occur, resulting in a breach and partial failure of the dam.