ACT was the Prequalified Specialty Contractor awarded the sewer rehabilitation contract by the Metropolitan St. Louis Sewer District. The rehabilitation specified to stabilize the 10 ft x 10 ft horseshoe shape concrete sewer consisted of consolidation grouting of voids behind the sewer and shotcrete repairs to delaminated areas. To facilitate the void grouting, chemical grout rings were installed every 100 feet in the sewer to provide containment bulkheads during grouting. Radial grout holes were drilled through the concrete sewer and into the surrounding rock using a custom built wagon style drill. Grouting was performed in sequence from sewer invert to the top of crown in order to allow venting and consolidation of the existing voids behind the sewer and in the surrounding rock.

Delaminated concrete was removed and replaced with silica fume enhanced shotcrete at isolated areas throughout the tunnel. The rehabilitation was performed across a working zone of 7,245 lineal feet.

All personnel, equipment and materials were lowered down a 50 foot deep shaft in order to access the work areas and all work was completed in a confined space environment.