Brookshire Brothers, a Texas and Louisiana based employee-owned grocery store, and Texas A&M University identified an opportunity for a public-private partnership adjacent to a student housing development. The project called for the development of a 48,000 square foot grocery store concept on a 4.9-acre site.
Although the site was an ideal location for a grocery store concept, it did not have sufficient area to allow for above-ground stormwater detention. Engineers needed an underground detention solution to detain over 50,000 cubic feet of runoff. By providing underground detention, the majority of the site would remain available for above-ground amenities such as site access, on-site parking, the building, and an outdoor venue planned on the property.
One of the site's unique characteristics was the amount of natural slope that existed from the street frontage to the rear of the site, where a natural creek ran along the backside of the property. The site also had an existing sanitary sewer line that created conflicts for an underground stormwater system. Also, the project required a loading dock designed at grade at the rear of the building. The design team was able to take advantage of the slope to accommodate the loading dock while still providing a substantial amount of depth for the underground storage system at the front of the store on the higher side of the site.
The detention system was made from a combination of 36" and 84" diameter corrugated metal pipe (CMP). The system was configured using six, 194 Iinear feet sections of 84" diameter pipe providing 46,850 cubic feet of storage and one, 264 linear feet section of 36" diameter pipe providing an additional 1,865 cubic feet of storage. Utilizing large diameter 84" CMP allowed 100% of the storage volume to be captured in the pipe. It also reduced the detention systems footprint, keeping construction and material costs at a minimum. The detained stormwater was conveyed to the rear of the site, where it was discharged into the creek.
With Contech's guidance, the design team designed the system to provide gaps between the CMP to leave space for light pole footings and cost-effectively routing the discharge to avoid conflicts with the existing sanitary sewer line.
"This site provided a great opportunity for creativity in the design of the underground detention system," said Melissa Thomas, Project Manager for Gessner Engineering. "By using the Contech system, we were able to utilize a combination of 84" and 36" CMP to achieve the detention volume required, as well as cross underneath existing sanitary sewer piping on-site. The collaborative process and quick communication with Contech's team was vital to the projects' success as changes were made to the site design after the system was ordered, which affected the tie-in locations."
- 1,485' of 36" and 84” Aluminized Steel Type 2
- 250' of 24" and 30” ULTRA FLO® Conveyance Pipe