Like most American cities, Gainesville, Florida had a pothole problem and Bob Stone from the Gainesville Department of Transportation was looking for a solution. Bob’s investigation revealed that the potholes were being caused by leaks in the joints of the storm water drainage system under the streets.
Years of high groundwater levels had created pressure on the storm drain and caused many of the joints to fail. Water, flowing in through the failed joints, carried the surrounding soil and silt into the pipe forming voids under the pavement. The traffic load eventually caused the pavement to break up and collapse.
Gainesville needed a cost-effective way to stop the leaks, fix the joints, and fill the voids that had developed around the pipes. When Bob talked to Gainesville Regional Utilities about the storm drain problem, they recommended that he call Prime Resins for advice.
Stephen Barton, of Prime Resins’ Grout Products Division, went to Gainesville to inspect the storm drain sewer system. After seeing the problem, he recommended injecting Prime-Flex 910 around the leaking joints. Stephen explained that he had selected the Prime-Flex 910 because "while all Prime-Flex products will stop leaks, 910 will also fix the voids. When 910 comes in contact with water, it expands rapidly. If it is injected behind a leak, it will mix with the in-flowing groundwater and some of it will be carried back through the crack or failed joint. The rest will migrate and expand into the surrounding soil. As the 910 cures, it will seal the joint, fill the voids, and create a stable, waterproof barrier around the pipes."
When the City of Gainesville wanted to conduct a test, Prime Resins asked for help from Clint Jenkins of Inducon Corporation, a contractor experienced with chemical grouting. Inducon’s crew drilled holes and installed injection ports in the pipe near one of the failed joints and then injected the Prime-Flex 910 through the ports. The expanding foam not only sealed the test joint, but also traveled ten feet under the pipe and sealed the next joint as well. The city engineers were so pleased with the results of this one test that they decided to proceed with the repair of joints in 1,500 linear feet of pipe. Inducon was selected to do that work and Chris NeSmith supervised the job.
Chris directed his crew to drill injection holes three to four feet from the joints. Based on his experience, he determined that this distance would give the 910 time to fill the voids around the pipe and migrate through the joint before it cured. This technique reduced the cost of the project as very little uncured material was lost through the joints. Since most leaks were in the bottom of the pipes, holes were drilled at the four and eight o’clock positions. Where joints leaked all the way around, additional holes were drilled at the ten and twelve o’clock positions.
Inducon used Prime Resins Bang-In Injection Ports in the holes and a single component airless sprayer to pump the Prime-Flex 910. They added a catalyst to give the 910 a two-minute set time. To stop gushing leaks, they increased the amount of catalyst to speed up the set time to 45 seconds.
This project was so successful that Gainesville is planning to repair more sections of pipe this year. We salute the City of Gainesville for their aggressive approach to solving their infrastructure problems and to everyone at Inducon for a job well done!
