Pipe Abandonment–Dam

Cellular Concrete Pipe Abandonment, Loudon, Virginia

Problem:

The outfall pipe of a golf course pond corroded below the designed water level, causing the pond level to drop significantly.  The pipe was installed at the base of the earthen dam, so removal would have been costly, and disruptive.  

The 18″ pipe was corrugated metal, had significantly corroded below the spring line, and had constrictions from vandals dropping riprap down the inlet riser.  Due to the known debris in the pipe and the deteriorated bottom, the pipe could not be video inspected.  There was slight seepage at the toe adjacent to the pipe.

Because the pipe invert was so severely corroded, it wasn’t possible to video inspect the pipe.  Video inspection would have to be done to line the pipe.  Since lining was ruled out, abandonment was chosen, along with building an upgraded outfall structure.

Constraints:

Equipment could only get to within 350 feet of the downstream bulkhead.  The bulkhead was approximately 75 feet below the truck location elevation.  The golf course was in use, so work could not disrupt normal operations.  

The rip-rap which had been dropped into the riser couldn’t be removed.  Therefore, the pipe abandonment material had to be able to flow around/through the rip-rap to completely fill the pipe.  

Solution:

Due do the pumping distance required and the constrictions within the pipe, cellular concrete was chosen for the pipe abandonment.  Cellular concrete is easy to pump long distances, and easily flows around constrictions.

The mix design was 30PCF wet cast density cellular concrete.  While a relatively low-strength mix, 30PCF wet cast density still provided greater than a 5x safety factor for calculated loads.

Results:

CJGeo cellular concrete crew successfully placed 10 cubic yards of cellular concrete to abandon the pipe.  After the pipe was abandoned, the site work contractor installed a new outfall and overflow structure.