Honorable Mention: Water Systems Category

Point Loma Digester Corewall Penetration Repair

San Diego, California

Submitted by DYK Incorporated

This project involved two existing prestressed concrete digesters at the Point Loma Wastewater Treatment Plant in San Diego, California. The owner wished to add several pipe penetrations through both corewalls, which required cutting the existing prestressing strands.

The existing protective shotcrete coating was chipped off the strands in and around the repair areas, and the existing strands were attached to the corewall on either side of the new penetrations by means of several pairs of clamping plates held in place with expansion anchors. The existing strands were then cut just inside of the clamp locations and the strand in between the cuts was removed.

Prestress was reapplied to the portions of the corewall affected by the new pipe penetrations by using a combination of two reinforced pilasters and two high strength prestressing threadbars on each digester. A shotcrete layer was then applied for protective and aesthetic purposes. This method avoided complete excavation and reduced completion time, at a substantial cost savings to the owner.