National Program for Inspection of Non-Federal Dams. Mystic Reservoir-South Dam (CT 00613), Connecticut Coastal Basin, Stonington, Connecticut. Phase I Inspection Report

摘要

Mystic Reservoir South dam is a 500 foot long combination earthfill and concrete gravity structure. The earthfill section is 200 feet long, has a varying cross section, contains a concrete core wall, and has a crest width of 7 feet. The concrete gravity section is 300 feet long, has a varied cross section and contains the spillway. The spillway is made up of the main spillway and the emergency spillway. the main spillway is a 50 feet long ogee weir with 1 foot high flashboards. The emergency spillway is a 75-ft ogee weir. The maximum spillway capacity is equal to 3,080 CFS which represents 86% of the test flood outflow. Based on a visual inspection at the site, the dam is considered to be in FAIR condition. However, these are several areas of concern which must be corrected to assure the long-term performance of this dam. It is recommended that the owner engage the services of a registered engineer experienced in the design of dams to accomplish the following: (1) Perform a detailed hydrologic/hydraulic investigation to assess further the need for and the means to increase project discharge capacity and the ability of the dam to withstand overtopping; (2) Recommend methods to rehabilitate the low level outlet to provide a means to draw down the reservoir for emergencies or for maintenance; (3) Investigate seepage into the well at the downstream toe of the embankment, at the toe of the spillway, and at concrete gravity section at Station 3+04; (4) Investigate the cause of the depression located on the downstream slope of the embankment at Station 1+30 and its relationship to the seepage into the well.