Design-Build Grouting Solution Stops Leakage

The City of San Diego had been plagued for decades by water leakage at an intersection that runs below the water table and located roughly 1.5 miles from San Diego Bay. The problem started to escalate after a five foot deep utility trench was installed by San Diego Gas & Electric (SDG&E) in the five to seven foot thick concrete pavement sections — repairs were attempted, but were unsuccessful.

Formulating a Solution

Representatives from the City of San Diego and SDG&E contacted STRUCTURAL TECHNOLOGIES’ Moisture Control Team to assist in the development of a water leakage solution. Following an initial series of meetings, SDG&E issued a purchase order to STRUCTURAL to develop a design-build solution including: consultation, design, general repair, waterproofing and injection grouting. STRUCTURAL TECHNOLOGIES provided engineering services and material selection.

The result was a below grade waterproofing design solution to repair and seal the utility trenches and the surrounding leaks found in the street. The design consisted of core drilling on a staggered pattern at eight foot centers. The holes through the entire pavement slab cross-section would create a gelled and soil solidified zone immediately beneath the thickened slab. An initial area was selected to test the selected grout and installation procedure for this unique repair. After nearly a year of reviews with SDG&E’s operations and environmental personnel, STRUCTURAL was issued a purchase order to begin resolving the problem for the entire afflicted area.

Repairing the Intersection

With 6,000 square feet of seven-foot-thick concrete that had multiple cracks and joints running horizontally and vertically, the task was to stop the leakage from around the utility trench and create an under-slab seal that pushed leakage water to the curb line, allowing for proper drainage. The utilities had to remain on during the repairs, presenting even more challenges. STRUCTURAL coordinated carefully with SDG&E to safely work around the live high voltage lines during construction.

Over 200 three inch diameter holes were drilled through the thickness of the slab — ranging from five to seven feet. STRUCTURAL installed custom made injection ports to the slab base, which allowed them to pump an acrylamide grout beneath the slab. In addition, all joints and cracks within the 6,000 square feet area were drilled with 5/8-inch diameter drill bits and pumped with an acrylate injection resin. By the end of the project, more than 5,500 gallons of acrylic based grout was pumped on the project.

The key to this repair was using a combination of the proper grouting design and materials along with a properly trained crew. STRUCTURAL’s partnership with STRUCTURAL TECHNOLOGIES, resulted in a collaborative effort to solve a challenging situation for the City of San Diego and SDG&E.