By Scott Kelly, Technical Consultant

Prime Resins would like to send our congratulations to Foundation Professionals of Florida, a division of Cal Tech Testing, for achieving the "APWA Project of the Year 2011" in the category of "Emergency Repair". Well done! Prime Resins is grateful to have the opportunity to work with Foundation Professionals on this unique application. A combination of Prime Fles 900 XLV and Prime 910 were utilized to complete this very successful project. Prime Resins also provided on-site support technical support. Below is a project overview written by the Engineers on the project:

Culvert and Weir Repair Park Avenue at Black Swamp Tallahassee, Florida

Submitted by: City of Tallahassee and Environmental and Geotechnical Specialists, Inc.

After several significant rainfall events, a depression in the surface of Park Avenue was noted, which grew to a point that it became a traffic hazard. The City of Tallahassee's crew attempted to stabilize the depression on several occasions with multiple methods, including removing and reconstruction a portion of the pavement structure and subgrade, and chemically grouting the culvert joints with an epoxy based grout. These repair options proved ineffective and the subsidence of the roadway continued. The option to remove the roadway and expose the box culvert was discussed; however, this option would be very expensive and difficult since there are active utilities over and around the culvert, and the south headwall of the culvert has a control weir used to regulate the water elevation within a protected wetland.

The City of Tallahassee contracted with Environmental and Geotechnical Specialists, Inc. (EGS) to determine the cause of the subsidence and provide emergency design and repair services in lieu of reconstructing the roadway, if practical, EGS conducted a subsurface investigation which included installing soil borings and temporary piezometers along the centerline of the roadway. Based on a series of groundwater measurements in the piezometer, it became clear that groundwater was leaking through the joints in the culvert and the joints in the control weir.

Because of the presence of the active utilities within the work zone, the importance to maintain traffic on the roadway, and the need to control the elevation of water in the adjacent wetland, EGS and the City of Tallahassee developed a plan to seal the leaking joints and fill the voids along the culvert and weir sidewalls from the inside.

The remediation program consisted of a two phased approach. The first phase was to install a series of equally spaced holes at each joint through the culvert flange into the seal. In each injection hole, a small injection port was installed and sealed. Through each injection port, Prime Flex 900 XLV was installed under pressure until it was observed exiting the adjacent injection port. The process was repeated until all the injection ports at each joint were grouted. After all the joints were grouted, small holes were installed through the culvert sidewalks to identify and map the voids. Injection ports were then installed in the culvert and weir sidewalls and the voids filled with Prime Flex 910 Hydrophobic Polyurethane grout.

Following completion of the grouting program, groundwater levels were measured in the piezometers to identify if a depression in the groundwater table at the culvert or weir was still present. No depression in the groundwater was detected.

After it was determined that the leaks had been repaired, the injection ports were ground flush with the culvert sidewall, the inlet of the culvert was blocked, and the sidewalls of the culvert and weir were pressure washed to remove the previous stains. Thirty days after the field program was completed, the culvert and weir were inspected for visible signs of leakage. Only four minor seeps were detected and these were grouted closed. The culvert and weir were reinspected after another 30 day period with no visible signs of seepage or staining in either the culvert or the weir. As a direct result of the City of Tallahassee's willingness to entertain both new construction products and methods, the following benefits were realized:

- Significant cost savings (over $75,000) compared to excavating the roadway and weir backfill

- Work was performed in the wet, therefore, no impact to the wetlands or construction dewatering was needed

- Traffic was maintained throughout the work process; therefore, no disruption of traffic was needed for reconstruction of the roadway or for a traditional compaction grouting method

- No interference with active utilities was required

- The grout was installed at the locations of the voids; thus reducing grout waste and unintended grout flow.

In the four months since the project was completed there has been no significant seepage of water through the joints of either the culvert or weir and the subsidence of the roadway has stopped.

Information provided by: Foundation Professionals of Florida