Pipe Abandonment Under Dam

Pipe Abandonment Through Dam in Fayetteville, NC Using Cellular Concrete

Problem:

6″ PVC pipe was discovered to cross the length of a low dam during rehabilitation.  The pipe was not known to exist during the project’s planning phase.  Due to the location of the pipe within the dam, it was not possible to access the pipe anywhere but at each end.  

The repair had to be completely quickly, as the discover of the pipe stopped other work on the job.

Constraints: 

At 1600 LF, with a single access point, the material used for the pipe abandonment had to be able to travel the full length of the pipe without packing, plugging or segregating.

Due to the location of the pipe within the dam, it wasn’t possible to excavate intermediate access points for placing material.  

pipe abandonment of small diameter pipe running through a dam in North Carolina

Pipe abandonment through dam using cellular concrete

Solution:

Lightweight cellular concrete was chosen for the pipe abandonment.  Cellular concrete is extremely flowable; it’s self-leveling to within a few inches in 100 feet.  This allows it to be pumped exceptionally long distances at very low pressure.  

This high ability to be pumped removed any need for intermediate placement locations.  

Result:

CJGeo abandoned the pipe in place using lightweight cellular concrete.  Complete fill was verified by uniform material coming out other end of pipe on opposite side of the dam.  The peak pumping pressure for this job was less than 20psi, which confirms the excellent pumpability of cellular concrete.

All that was required for preparation by the contractor was a small lay-down area on one side of the dam.  The pipe was cut and a valve assembly added.  Material was placed from the single end of the pipe, with a person monitoring on the other end of the dam.  When material showed up on the other side, the valves were closed and the project completed.