Pump Station Settlement in Clarksville, IN
Problem
In Clarksville, Indiana, a pump station had experienced settlement beneath multiple underground structures and the surrounding ground surface. The station was about 20 years old, with settlement only occurring in the last five years. The wet well was 10’ in diameter, extended 23’ below grade, and was experiencing about 1” of differential settlement. Surrounding the wet well was a transformer pad and a valve pit that had settled as well. After careful consideration, the city called URETEK.
Analysis
A local consulting firm completed a geotechnical exploration to evaluate the condition of underlying soils. Soil borings were conducted at various locations around the site. Weak clay backfill was discovered in some areas, particularly around and beneath the wet well. Based on the soil borings, bedrock was encountered an additional 10’ beneath the wet well. After all necessary testing was completed, URETEK Deep Injection® (UDI) was proposed to bypass the rock and solve the settlement issue.
Solution
UDI was an excellent solution to stabilize the wet well, valve pit, and transformer pad. URETEK crew performed the UDI process using URETEK 486 Star® polymer in a grid pattern beneath all three structures. For the crew to access the floor of the wet well, the sanitary flow had to be diverted, and the well had to be pumped out. This area was also beneath the water table, so the crew was injecting against head pressure while avoiding flooding their workspace.
Result
URETEK successfully stabilized the foundation beneath the transformer pad, valve pit, and wet well. The city was delighted with the results. Due to the wet well’s depth, traditional excavation would have required removing the transformer pad and valve pit while disconnecting all electric connections and plumbing. The 25’ plus excavation in weak clay soils would have needed sheet pile walls or benching. URETEK provided significant savings to time and cost by leaving the underground structures in place and stabilizing the existing soils.
URETEK Deep Injection® (UDI)
Widely referenced throughout the industry, UDI involves the injection of structural polymer into base and subgrade soils to increase the load-bearing capacity. This is achieved by injecting the polymer through small holes drilled directly through the pavement structure to depths determined by site-specific analysis. URETEK 486 Star® material flows easily into voids and weak zones within the soil mass below. Through a controlled chemical reaction, the expanding polymer compacts surrounding soils and applies controlled pressure on targeted areas of the affected pavement above. If needed, a multi-injection design plan is utilized to gently return the pavement to its original grade. The composite material quickly cures into a strong, dimensionally stable, and water-resistant geo-material, providing years of reliable service.
URETEK 486 Star®
URETEK 486 Star® polymer is a two-component, high-density, expanding thermoset polyurethane system. It was developed to be the ideal solution for under-sealing, void filling, lifting of settled pavement, stabilization and stiffening of weak soils, and for encapsulating and sealing buried infrastructure. URETEK 486 Star® is environmentally inert, non-toxic, and resists underground water erosion or weakening due to its industry-leading hydrophobic properties.
