Significant Facts

• Repaired 400 linear feet of earthen dam
• First concrete labyrinth weir installed in Connecticut
• Installed concrete sluiceway
• Installed drainage at toe of dam

Project Summary

True Blue Environmental Services was hired by a confidential client to provide design and construction services for the restoration of an early 1900’s surface water impoundment.  This restoration of the earthen dam and creation of a labyrinth weir was mandated by the Connecticut Department of Energy & Environmental Protection.

The first step was to lower the exiting lake water level to allow for an inspection of the upstream portion of the dam.  The inspection was used to design a solution to the exiting leakage through the earthen portion of the dam and possible undermining which could have resulted in a catastrophic dam failure.  The inspection was also key in determining and selecting a design replacement weir and outlet structure.

True Blue Environmental Services was required to thoroughly evaluate potential areas of drain failure hydrologic conditions and wetlands impacts. Based on the results of this evaluation, a storage capacity and engineering design was presented.  A 40-mil geotextile liner system, including an upstream burial of the liner into the clay layer to minimize flow beneath the new system, was installed.  The liner was covered with clay and riprap was added to stabilize the surface.  The existing out flow structure was demolished and replaced with a labyrinth weir and outlet structure.  The labyrinth weir was designed to allow for 100-year flood flow events over a narrow channel. The system was the first of its kind to be installed in the state of Connecticut.