Client: City of Clearwater
Market: Government
Solution: Soil Stabilization
Services: Chemical Grout
This case study examines the successful remediation of soil erosion and structural instability surrounding a stormwater manhole in Clearwater, Florida.
The City of Clearwater faced challenges related to infrastructure deterioration due to water infiltration and soil washout, a common problem in areas with fluctuating water tables and aging infrastructure. The City of Clearwater needed a plan to fix both the immediate problems and the underlying issues. A traditional “rip-and-replace” methodology, while technically feasible, would have entailed prolonged road closures, significant cost implications, and a substantial environmental footprint.
Helicon’s application of polyurethane grout injection provided a non-invasive and cost-effective solution.
Soil Erosion and Settlement:
The primary issue was the progressive erosion of soil surrounding the manhole, leading to voids and settlement. This resulted in visible cracks and depressions in the adjacent roadway, posing a safety hazard to vehicles and pedestrians.
Water Infiltration:
Cracks and joints within the manhole allowed groundwater and stormwater to infiltrate the surrounding soil. This water flow caused soil erosion, carrying away fine soil particles and creating voids. The constant exposure to moisture also contributed to the deterioration of the manhole structure itself.
Infrastructure Deterioration:
The combined effects of soil erosion and water infiltration threatened the structural integrity of the manhole and the surrounding roadway. Traditional repair methods, such as excavation and replacement, would have been highly disruptive and costly.
Polyurethane Grout Injection:
Helicon employed polyurethane grout injection, a technique that involves injecting a specialized polymer into the affected soil. The chosen grout, AP700, is a one-part polyurethane permeation grout designed to fill voids, stabilize soil, and create a water-resistant barrier. Injection points were strategically placed in a grid pattern around the manhole, targeting the areas of greatest soil erosion.
Grout Properties and Mechanism:
The polyurethane grout expands upon injection, filling voids and compacting the surrounding soil. It forms a durable, hydrophobic barrier that prevents further water infiltration. The rapid curing time of the grout minimized disruption to traffic and allowed for a quick return to service. Precise drilling and injection techniques were used to ensure the grout reached the targeted areas. The injection process was closely monitored to control the amount of grout injected and to ensure proper distribution. The grout was injected until it could be observed seeping from the cracks in the manhole, showing the grout had filled the voids.
Soil Stabilization:
The polyurethane grout effectively stabilized the soil surrounding the manhole, eliminating voids and preventing further settlement. The roadway surface was restored to a level and stable condition.
Water Intrusion Prevention:
The grout created a water-resistant barrier, preventing further water infiltration and soil erosion. This significantly extended the lifespan of the manhole and reduced the risk of future damage.
Cost and Time Savings:
The polyurethane grout injection method provided a significant cost savings compared to traditional excavation and replacement methods. The rapid curing time minimized disruption to traffic and reduced the overall project timeline.
Long-Term Performance:
The hydrophobic and closed cell properties of the AP700 grout, contribute to the long term stability of the repair. This case study demonstrates the effectiveness of polyurethane grout injection as a solution for stabilizing stormwater manholes and preventing soil erosion. The technique offers a non-invasive, cost-effective, and efficient alternative to traditional repair methods. By addressing the root causes of infrastructure deterioration, this approach contributes to the long-term sustainability of stormwater management systems.
Key Considerations:
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