Mr. Wurster founded Wurster Engineering & Construction Company in 1997 to provide design/build services in the geotechnical construction field. A large portion of their work was soil nail walls. Government and private specifications called for “drain grates” to be placed at the base of the drainboard to convey collected water to a pipe, that could then transfer the water though the face of the shotcrete.
After consultation with various ADSC contractor members, it was determined that many contractors were making their own drains out of various plumbing and roofing products and duct tape. Most involved pinning or taping their drains to the face of the drainboard, and we tried this ourselves. The force of the shotcrete in most cases would dislodge the drainage connection. Others cut a slice in a piece of PVC pipe and tried slipping it over the bottom edge of the drainboard.
Mr. Wurster set out to find a better way to connect a pipe to drainboard in soil nail walls. He realized that it was better to cut a hole in the drainboard and connect to the drainboard from both sides, thus making a strong connection. In the words of a fellow contractor when he saw the prototype, “You figured it out! I wish I had thought of that”.
Additionally, he sought to increase the drainage area to improve flow, thus a retainer ring much larger than the pipe itself was incorporated into the design. Tests were run on the DrainGreat at a local laboratory (see lab tests) and a flow rate of up to 80 gallons per minute was achieved with about 2 ft water pressure head, well in excess of what we would expect a drain grate to discharge. Flow rates any higher are typically handled by horizontal drains drilled into the face of the soil nail wall.
DrainGreat connects to standard 3” diameter PVC pipe, and we felt that was about the right size pipe for the application. When specifications require a 2” PVC pipe, a standard 3” to 2” reducer can be used, however, the discharge rate may be reduced. When specifications require a 4” PVC pipe, a standard 3” to 4” adaptor can be used, however, the larger pipe will not result in better discharge rate.
One of the many advantages of using DrainGreats, is that they are less susceptible to vandalism. When a pipe is connected to the face of drainboard, someone could make a hole in the drainboard by just pushing a stick or piece of rebar through the weep drain. As a result, soil from behind the drainboard could erode through the face of the soil nail wall. With DrainGreat, that portion of the drainboard is removed and the only thing that is exposed is the back half of the DrainGreat, which is nearly impossible to puncture.
DrainGreats have been installed all over the United States and as far away as Canada and New Zealand. DrainGreats are manufactured in Spartanburg, South Carolina, USA.