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Small lot required an underground system to accommodate a parking lot
Montgomery, Ala., was slated to get a new 28,000-sq-ft. Looking Good store, offering men's clothing and sportswear to local residents. The engineers at Larry Speaks and Associates joined the design team to create a storm water system to detain runoff onsite and release it slowly into a municipal system, as required by the local regulations.
As it often happens in urban areas where land is at a premium, the 4.5-acre site did not have enough space to fit both a detention pond and a parking lot. The engineers took the only possible option–designing an underground storm water system.
“If the engineers used an aboveground detention system, the site would have lost 22,000 sq ft., which would have cost the owner about $166,000,” said contractor Danny Clements of Danny Clements Builders. “Instead, an underground system is conveniently located under the parking lot, taking up no usable space.”
The storm water system for Looking Good was provided by CULTEC Inc. Clements said he preferred CULTEC’s system to a competitor’s product because it allowed him to get the job done more cost-effectively. The system’s unique internal manifold design eliminated the need for a costly external pipe header, and allowed the company to offer a competitive price. Additionally, the system’s quick and straightforward installation helped further reduce costs.
While the city of Montgomery requires local storm water systems to handle 25-year storms, Looking Good’s system was designed for a 50-year storm. The Department of Transportation in Montgomery requires storm water systems to have increased capacity when they discharge runoff into a state right-of-way. CULTEC’s chambers detain parking lot runoff that is piped along Highway 80 into a drainage swale. Originally, the engineers designed the system to send 15% of the runoff into a 4,200-ft. underground concrete pipe that would have released it to a municipal sewer. However, as the local sewer had already reached its capacity at the time, Looking Good’s system was later redesigned to increase the bed size by 25% and send all runoff into CULTEC’s chambers. Clements worked with CULTEC to revise the system’s layout to garner additional storage volume.
From CULTEC’s nine chamber sizes, the engineers selected the Recharger 150, a lower-profile chamber typically used for installations with depth restrictions or when a larger infiltrative area is required. The unit is 8.5 ft long, 33 in. wide and 18.5 in. high, with a storage capacity of 19.88 ft per unit.
About 460 units of the Recharger 150 were installed in a 14,580-sq-ft bed of crushed limestone, providing 21,175 cu ft of storage.