Annular Space Grouting Case Study

Pipeline 4 Relining

San Diego County

Installed over 2000 cubic yards of Geofoam SNP™ in 2006

In San Diego County, a large diameter transmission pipeline was found to need either replacement or repair. Ultimately, due to the cost savings to the City of San Diego and in an attempt to minimize disruption to the community, repairing the pipeline was chosen.

San Diego Water District opted to repair the carrier pipe by inserting a steel liner in the existing concrete pipe. This saved the San Diego residents from having their water service interrupted, and meant considerable tax savings as well. For this project, and this particular application, the area between the host pipe and the carrier pipe had to be grouted to avoid movement and corrosion of the liner.

In order to maximize the pipe capacity for water transportation, the San Diego Water Authority used the largest diameter carrier pipe to fit into the existing concrete host pipe, resulting in a very minimal annular space, approximately 1.5 inches. This required an extremely pumpable and fluid grout to be placed over 5500 lineal feet with a pumping pressure of less than 3 PSI.

Geo-Cell Solutions's dry mix equipment produced Geofoam SNP material averaging 50 PCF and 500 PSI. The Geofoam SNP annular space grouting backfilled approximately 21,500 feet of relined pipeline with only six access shafts.