The Job
This spillway undersealing project is located at a dam in Tuckahoe, Virginia. The dam is owned and maintained by a home owner association, and is approximately 45 years old.
The Challenge
The lake, which is is approximately 7.5 acres, drains through a 24′ RCP pipe that maintains the lake at the lip of a large concrete spillway that only occasionally sees flow. The lake dropped about two feet, which was an immediate cause for concern. A consulting engineer specializing in dams inspected the structure, and determined that a flowpath had opened under the spillway. This flowpath allowed water to drain under the structure at an elevation below the primary outlet.
This obviously caused concerns about the stability of the earthen structure. The consultant recommended that the owner work with CJGeo to perform polyurethane grouting to address the voids and restore flow to its designed routes.
The Solution
CJGeo worked with the consultant to design a polyurethane grouting program to address two different problems:
- water piping along the outside of the concrete-encased 24″ RCP outfall
- bulk voids under the 6″ thick concrete secondary spillway structure
To address the piping along the pipe, CJGeo proposed injecting CJGrout 22SHV geotechnical polyurethane grout along the entire pipe alignment using driven sacrificial tubing. Because the pipe was relatively shallow and the soils relatively soft and uniform, percussion installation of tubing was sufficient, and no sonic drilling was needed.
To address the voids under the larger surface spillway structure, CJGeo also proposed grouting with CJGrout 22SHV geotechnical polyurethane grout. Here, grout installation was through mechanical packers installed in 5/8″ holes drilled through the concrete.
A three person polyurethane grouting crew took less than a day to perform all of the grouting. Confirmation of fill was grout extruding from numerous points at the top and bottom of the spillway, as well as cross-hole communication.
Speak With An Expert
Facing a similar challenge to this spillway undersealing project? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.
