A major retailer identified a persistent stormwater problem at one of its stores in northern Missouri, and Environmental Works, Inc. (EWI) was called in to permanently fix the problem do a full-scale stormwater replacement.
The crux of the problem was a concrete curb designed to catch stormwater flowing off the back of the building. The builders did not install downspouts when the store was constructed decades ago, causing water to simply roll off the back roof and onto the curb. The curb spanned the length of the store, and ran gradually downhill from both east and west ends of the building to a concrete channel in the middle.
Over five weeks in September and October 2019, EWI’s stormwater field services team replaced the outdated concrete curb, as well as a storm drain designed to catch stormwater flowing from the store’s parking lot.
The stormwater replacement project was split into two phases, said Willie Vance, Stormwater Operations Manager and on-site project manager.
The first phase involved the demolition of the curb, the excavation of the work space and the installation of over 700 feet of High Density Polyethylene (HDPE) piping. To better direct the stormwater from the roof, the stormwater team, which included two heavy equipment operators, two field technicians and Vance as supervisor, installed all new down spouts tied directly into the piping. The team also installed a catch basin to the piping to reduce the amount of trash and pollutants flowing from the store down into the wet weather creek to which the pipe drains.
Catch basins are used to capture sediment, debris and associated pollutants, and act as pretreatment for other treatment practices by capturing large sediments, according to the Environmental Protection Agency (EPA).
During the second phase, the team replaced an aging storm drain with a triple catch basin running to a junction box.
Junction boxes interconnect storm sewers and other piping together, and provide change-in-direction or joining of piping of different sizes.
The team then installed a pipe from the first junction box to a second junction box. Finally, the team installed piping from this second box out into a rock check dam. The dam, made up of quarried limestone rocks, was installed by the team using Best Management Practices and then inspected according to standard stormwater regulations.
David Lewis, senior project manager for the site, said the dam, as well as silt fencing installed during both phases, will help “mitigate the effect of exposed sediment runoff during the project.”
At the conclusion of the project, erosion control matting and seed was placed throughout the work site in order to stabilize the disturbed earth and establish native vegetation.
In total, the team installed four pre-cast structures (two catch basins and two junction boxes). All piping and structures were installed in accordance with engineer-designed specifications, said Lewis.
The project took four and a half weeks, with a few rain days sprinkled in, said Vance. He added that EWI being a full-service environmental company with so many different capabilities and service lines helps his stormwater replacement projects move along at an efficient pace.
“From people to equipment, we can do almost everything in-house,” said Vance. “It’s one of the easiest parts of getting projects done, and one of the best things about working at EWI.”