A dry cleaning facility was discharging cleaning solution containing perchloroethylene (PCE) contaminant that infiltrated the soil and aquifer through a leak in a storm drain. The U.S. Environmental Protection Agency (EPA) was called in to evaluate the site and determined that a major excavation of a city block, 28 ft down to the bedrock, would be necessary. The project required bypassing both an 18-in. sewer main and 30-in. storm drain for the duration of the excavation and rebuild of the site. The EPA also required treatment of the groundwater that would be dewatered during the excavation.
Rain for Rent, Montana, was able to supply a system to handle both the sanitary and storm discharges including monitoring the systems from 7 p.m. to 7 a.m. The sanitary bypass system consisted of two DV-150i 6-in. Power Prime pumps. The storm system was designed with three Power Prime pumps (one DV-300 12 in., one DV-200c 12 in. x 8 in. and one DV-100 4 inch for backup in case of major weather events) manifold into a 12-in. HDPE pipe for discharge. The sanitary system ran 24/7; the storm system ran during rain and storm events as needed.
Both systems, installed side by side, were piped through a 12-ft road crossing to allow dump trucks access to the dig site, back to the disposal area, and 300 ft down the street to the discharge points.
To meet EPA requirements, the groundwater had to be tested and filtered to applicable permit requirements of less than 5 ppb before discharge. The groundwater was pumped into two 21,000-gal frac tanks to allow settling of the solids and testing before and after filtration. A DV-100 4-in. Power Prime pump was used to pump the groundwater from the frac tanks through a 48-4 sand media filter, BF-200 filter, and two 5,000-lb activated carbon units. The clean water was batched again into a 21,000-gal frac tank to be tested prior to discharge into the city's sanitary sewer system.
For three-and-a-half months, Rain for Rent bypassed both the storm and sanitary systems to allow for excavation and reconstruction of the contaminated site. During that time, more than 120,000 gal of contaminated groundwater were treated and discharged into the city's sanitary sewer system with a non-detect reading for contaminant.
