Barker Lemar, a Midwest environmental services firm, works with clients on many environmental engineering projects, including stormwater management, municipal infrastructure, solid waste management, sustainable design, and planning and information technology solutions. When they had a stormwater issue at their own West Des Moines, Iowa, office, they turned to fellow stormwater management experts at the U.S. government agency typically known for providing technical assistance to farmers—the Department of Agriculture’s Natural Resources Conservation Service (NRCS).
NRCS works with farmers and other landowners to address natural resource concerns. Formerly known as the Soil Conservation Service, Congress formed NRCS in 1935 to fight Dust Bowl soil erosion. Adapting with change, NRCS is now also known as a source for urban stormwater management ideas and information while it continues serving its primary customer base of farmers and ranchers.
Barker Lemar’s West Des Moines office is adjacent to Jordan Creek, a small stream that starts in Dallas County and meanders eastward through West Des Moines before emptying into the Raccoon River, an important drinking water source for Des Moines. The firm saw an environmental problem because its parking lot and building roofs shed unfiltered stormwater runoff directly into Jordan Creek. Vice President Tracy Lemar, P.E., and Senior Project Engineer John Franklin decided to stop that direct discharge by slowing and filtering the runoff before it entered Jordan Creek.
They turned to NRCS employees Paul Miller and Linda Appelgate for help with their problem. Miller is a district conservationist with 25 years of experience as a soil conservationist, manure management specialist, and urban conservationist. Appelgate is a resource conservationist and coordinator for Iowa Heartland Resource Conservation and Development (RC&D), which builds partnerships to protect our natural resources.
Lemar and Appelgate originally thought the solution was to replace the firm’s traditional parking lot with a pervious pavement system. Using a concrete paver system or porous asphalt, a pervious pavement system allows water to go through it and into the soil. Engineers saw this as an effective, but costly, solution.
After further discussion, Barker Lemar decided to install an underground stormwater detention chamber between its parking lot and main office building. Looking at many options and the costs involved, Lemar and Franklin reconfigured their plans and designed a 60-foot-long, 5-foot-deep stormwater detention chamber. The plan called for the structure to handle a 3/4-inch-per-hour rainfall from their acre and a half of surface area. The runoff infiltrates into the ground where it can be slowed and filtered before entering the creek or water table.
A 60-foot long, 5-foot deep, stormwater detention chamber is ready for backfill on the West Des Moines campus of engineering firm Barker Lemar. Designed and built by the firm, with technical assistance from USDA’s Natural Resources Conservation Service, the structure captures stormwater runoff from their parking lot and keeps pollutants from entering a nearby stream. Built in 2006, the detention chamber is so successful that Barker Lemar engineers adapted the design to other uses including geothermal applications. (Barker Lemar photo)
For storms of higher intensity, the detention structure fills up and the balance of this flow is discharged directly into Jordan Creek.
Installed in the summer of 2006 for $30,000, with technical and financial assistance from NRCS, Franklin says the detention chamber is working better than they thought it would. "It appears to take an inch or more of runoff," said Franklin. "We’ve had a few heavy storms where we’ve had a direct discharge to the creek, but the first flush of water off the parking lot with its pollutants, debris, anti-freeze, and silt enter the infiltration chamber. The pollutants then enter the detention chamber instead of the creek, improving water quality."
Barker Lemar engineers like the detention chamber design so much they are using it in other applications. "For example," said Franklin, "we adopted this technology for a geothermal application in downtown Des Moines. There, water is pumped from the alluvial aquifer and used for heating and cooling and then infiltrated back into the alluvial aquifer. This saved the client money because the design eliminates the need for burying a more conventional geothermal cooling system."
They are using the design in two or three other applications as well. "As a design team," said Lemar, "we have to have a number of tools in our arsenal. The more alternatives you can find that have the ability to work for the client, the better the design you can put together and the more cost effective you can make it."