Manhole Sealing in St. Louis, Missouri


In St. Louis, Missouri, officials were dealing with significant inflow and infiltration (I&I) issues that they suspected were caused by extensive voids around a manhole and its connection to the storm water pipe system below. The St. Louis Metropolitan Sewer District (STLMSD) contacted URETEK to come take a look at the situation.


The STLMSD showed URETEK camera footage from the storm water pipe that pinpointed the exact locations of the leaks. With this footage, URETEK identified several locations within the manhole and lateral pipe joint as the sources of the I&I. It was agreed that erosion in proximity to the leak sites had created several voids in the surrounding soil that, over time, had contributed to the I&I problems.


URETEK employed its URETEK Deep Injection® (UDI) process to both seal the leaking joints and stabilize the soils around the manhole. Based on observations from the camera footage, a pattern of injection locations was laid out to address each identified point of ingress. Small diameter (5/8-inch) holes were then drilled through the manhole wall according to the pattern. URETEK’s patented 486 STAR® polymer resin was then precisely injected through each of the drilled holes. The resin expanded and cured within minutes, sealing the manhole, filling any voids in the adjacent soil created by previous infiltration, and stabilizing the manhole and surrounding soils. Most importantly, the expanded material formed a dense hydrophobic seal which effectively blocked future I&I from occurring on the exterior side of the manhole wall.


In just one day of work, URETEK sealed the manhole and sewer line joints. This prevented future I&I issues for St. Louis officials, all with zero-excavation, while maintaining the structural integrity of the storm pipe. URETEK is known for its cost-effective, fast, clean, and long-lasting repair solutions, and this job was another example of our crews doing what they do best.

URETEK Deep Injection® (UDI)

Widely referenced throughout our 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. Our 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 a 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.

Yellow tube emerging from hatch
Before and after of manhole at night


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