Pipe abandonment under dam using cellular concrete.
Annular space grouting under dam using cellular concrete.

Dam Outfall Abandonment & Annular Grouting

Challenge:

Cellular concrete placement for abandonment of RCP culvert under a dam.

Pipe abandonment using cellular concrete.

Two pipes passing through a dam needed to be grouted.  A single CMP pipe was being slip lined with HDPE, and required annular space grouting.  The second pipe, which was approximately 170′ long, with a 15′ riser on it (all RCP), needed dam outfall abandonment.  Both situations required pumping more than 100′ down the embankment of the dam, and then material travel back uphill through the pipes being grouted.

Limits:

Material had to be easily pumped more than 100 feet.  It also had to be flowable enough to ensure that all voids were filled around the pipes.  This was important to ensure no piping of water around the pipes, and stability of both, as well.  

For the pipe which was lined, the material had to be placed at low pressure to ensure no damage to the slipped in pipe.  For the pipe being abandoned had to be completely filled with uniform material from one end to the other.

Solution:

Cellular concrete grouting is ideal for both abandonments and annular space grouting applications.  Cellular concrete is easily pumped long distances at low pressures.  This allows for placement in remove locations that aren’t easily accessible by pumping equipment.  

Since material had to be pumped 100+ feet to reach the placement bulkheads, and then up to 185 feet from the placement bulkheads, cellular was the only choice for ensuring complete fill.

Result:

Annular space grouting using cellular concrete.

Annular space grouting.

CJGeo successfully grouted both pipes over a few hours.  Due to the small nature of the placements, truck batching was used to generate the cellular concrete.  During the dam outfall abandonment, cellular concrete was pumped 185 feet from a single access point.  Work was done against 25VF of fall.  At the completion of the cellular concrete placement for the abandonment, cellular concrete was present at the top of the RCP riser.