It takes planning and good leadership to decide on an effective solution to problems associated with a building asset. Recently, a large wholesale warehouse facility in Cincinnati began to experience large sinkholes across a significant portion of their customer parking lot. Unable to determine the problem at that time, store management was forced to close a portion of the parking lot, inconveniencing their customers. This particular parking lot is unusual in that a drainage system is located directly under the parking lot, consisting of a network of pipes spanning 250 feet in length and 12” in diameter. Joint separations in the underground drainage piping had caused enough soil erosion to create sinkholes in the asphalt. Engineers were concerned that other unknown sinkholes could cave in anytime, resulting in further costly damage, and potentially posing safety hazards to customers.
Needing to accurately identify the location of the voids and weak soils, URETEK utilized a ground penetrating radar system. As a quality control measure, URETEK also used a dynamic cone penetrometer to confirm the findings and establish the depth of the problem. A visual can be seen (see picture to the right) of actual soil seepage into one of the 12’ diameter pipes that caused the sinkholes. The assessment of the situation indicated 17,000 square feet of the parking lot required stabilization and/or sealing of underground joints.
After gathering all possible data collected by URETEK and the GPR contractor, a solution was designed and approved by the customer. URETEK first sealed 26 separated joints identified in the detention basin system. Many joints required sealing the entire circumference of the joint. URETEK used small, 5/8 inch injection holes drilled from the inside of the pipe to the soil surrounding pipe to deploy the patented, moisture resistive , structural grade polymer. The polymer, which has an expansion ratio of 20:1.0, effectively sealed the pipe while also stabilizing the eroding soil around the pipe (see below). Secondly, URETEK stabilized the base soils beneath the parking lot using a grid pattern for injection. The injection probes used were placed 3.5’ into the soil to inject the weak strata shown by the GPR unit. This effectively increased the load bearing capacity of the soil to support customer traffic and delivery trucks. The total project was completed in six days with three of those days dedicated to surface work. Downtime was kept to a minimum and the customer was very pleased with the results which included a fully functional underground drainage system. URETEK was ultimately chosen as the ideal solution due to the minimal disruption to customer traffic, the speed at which the solution could be implemented, and the cost effectiveness of the overall solution.