Cutoff Wall Connections to Existing Large Diameter Pipes-Paper

Paper

Pdf Summary

The Herbert Hoover Dike Rehabilitation project required a seepage cutoff wall to connect to three existing pipes at pump station S-131: one 96-inch corrugated metal pipe (CMP) and two 48-inch steel pipes. Contract documents specified jet grouting around all pipes. However, the nearly 60-year-old CMP had corrosion and minor leaks, and the aggressive jetting required posed a risk of damaging it.<br /><br />BAUER Foundation Corp. proposed an alternative, approved through a value engineering proposal, that avoided jet grouting directly around the CMP. The team excavated and removed a 10-foot section of the pipe, installed jet-grout cutoff wall beneath it, then reconnected the CMP with a replacement section and concrete collars. The two steel pipes remained in place and were incorporated into the jet-grout works.<br /><br />The operation required a temporary retaining structure, dewatering, and a 24/7 bypass pumping system to maintain water transfer between Lake Okeechobee and the L-50 canal. Asbestos was discovered in the CMP wrapping, requiring specialist abatement. Jet grouting was performed from within the excavation, and controlled low-strength material (CLSM), or flow fill, was placed in staged lifts to reconnect the CMP, jet-grout wall, and adjacent conventional cutoff wall. The conventional wall was installed using cutter soil mixing, with specially shaped panels to improve its connection to the other cutoff-wall elements.<br /><br />The CLSM backfill formed the central connection between the pipe and the cutoff-wall components. The work was completed within budget and on schedule, to the client’s satisfaction. The project demonstrates an alternative to direct jet grouting where a large, deteriorated pipe could be vulnerable to installation damage.

Keywords

Herbert Hoover Dike

seepage cutoff wall

jet grouting

corrugated metal pipe

value engineering

bypass pumping

asbestos abatement

controlled low-strength material

cutter soil mixing

pipe rehabilitation