Document b8v59Yg9q0DYLK8nL3bOvjvZ

Industrial User Facility Inspection Report U.S. EPA, Region 8 Name of industry and location: CWS Colorado, LLC 7675 Dahlia St. Commerce City, CO 80022 IU - NPDES ID Date of visit: January 29, 2025 Name(s) / Affiliation / email of inspector(s): U.S. EPA: Al Garcia, garcia.al@epa.gov Monica Crosby, crosby.monica@epa.gov Control Authority / NPDES Permit No. South Adams County Water and Sanitation District NPDES Permit No. CO-0026662 COPIU0013 Approximate Time of visit: 11:00 a.m. - 12:00 p.m. South Adams County Water and Sanitation District: x Gary Bassett, gbassett@sacwsd.org x Zach Shellum, zshellum@sacwsd.org General Facility Information: Representatives at Inspection: x Jack Hagaman, jack@ateccolorado.com Type of Business Operations: x Treatment and neutralization of concrete washout water and solids. Facility Information: x 5 employees x Monday-Friday x 5 a.m. - 3 p.m. Inspection Description: Al Garcia and Monica Crosby from the U.S. Environmental Protection Agency (EPA) and Gary Bassett and Zach Shellum from the South Adams County Water and Sanitation District (District) conducted a significant industrial user (SIU) inspection of the CWS Colorado facility (facility) located at 7675 Dahlia St., Commerce City, CO 80022. The SIU inspection was conducted as part of the EPA Pretreatment Audit of the District's Publicly Owned Treatment Works (POTW) and EPA-approved Pretreatment Program. The inspection of the facility provides current conditions of the facility's unit operations and consisted of an evaluation of the waste streams generated from the unit operations, and the management of these waste streams, including potential for spills and slug discharges. The facility discharges to the sewer collection system leading to the District's POTW. Page 1 of 5 Upon arriving at the facility on January 29, 2024, at approximately 11:00 a.m., Al Garcia and Monica Crosby of the EPA presented credentials to the facility representative and explained the purpose of the inspection. The inspectors then explained the general purpose and procedures of the inspection. During the opening conference, the facility representative provided an overview of the facility's operations, focusing on the handling/storage of materials and processes that generate wastewater. Following the opening conference, the facility representative accompanied the group of inspectors on a facility walk-through. The EPA conducted a closing conference with the facility representatives, where the EPA communicated preliminary findings and recommendations. The EPA and District representatives left the facility at approximately 12:00 p.m. Process Description: The facility located at 7675 Dahlia St., Commerce City, CO treats and neutralizes concrete washout water and solids. The facility has about 5 full-time employees and operates one 8-hour shift, Monday through Friday. The building is made up of three shop bays. The two westernmost bays are occupied by a separate company, American Transportation and Equipment Company (ATEC). CWS uses the third bay for minimal truck maintenance activities. The Google Earth view of the facility is shown in Figure 1. Figure 1 - CWS Colorado -Google Earth Pro View Chemical and Raw Materials Storage - The facility provides prefabricated metal bins to construction sites for the collection of concrete washout. Once full, the facility will travel to the construction site and either collect the collection bin or pump out the contents and reuse the bin. The facility then hauls the collection bins to their facility for treatment and neutralization. The facility employs &2ZKLFKLVsupplied in bulk cylinders, for neutralization. About four or five cylinders of CO2 are stored at the facility at one time. The facility houses propane to run the pressure washer. Any used oil generated from either CWS or ATEC is used for heating in the shop. The facility does not house any other chemicals. Wastewater Treatment - Upon delivery from construction sites, the collection bins are placed to the west of a 32' x 80' concrete pad. Wastewater is pumped from the collection bins into a 3,000-gallon roll-off box (Tank No. 1), which is located outside, on the south end of the property. The facility's trucks are outfitted with vacuums for the times when the building site retains the collection bin. The material is then pumped out by the trucks directly onto the concrete pad. All remaining aggregate material is hauled to a nearby aggregate recycler, Allied Recycled Materials. The facility representative explained that the concrete pad has a sump pit for accidental spills. Any Page 2 of 5 wastewater collected on the concrete pad is sent to Tank No. 1 via the sump pump. The concrete pad is slanted to keep water from running into the parking lot, and the south side is surrounded with containment curbing. According to the facility representative, wastewater settles in Tank No. 1 for 24-48 hours. The supernatant wastewater is pumped into a 2,200-gallon tank (Tank No. 2), and the settled solids are removed and hauled by Allied Recycled Materials. Wastewater in Tank No. 2 settles for an additional 24-48 hours and is then pumped to a 2,200-gallon pH neutralization tank (Tank No. 3). Tank Nos. 3 and 4 are kept inside a shed located on the south end of the property. Settled solids in Tank No. 2 are also removed and hauled by Allied Recycled Materials. Within Tank No. 3, CO2 is pumped into the wastewater and continuously mixed with a jacuzzi pump IRUDPLQLPXPRIILYHKRXUV7KHGLVWULEXWLRQRI&2LVGHWHUPLQHGZLWKDJDXJH2QFHWKHS+LVQHXWUDOL]HG between 7 or 8 s.u., the wastewater settles for 12-24 hours and is then discharged to the District's sanitary sewer at a rate of ten gallons a minute. With regard to cleaning, it was explained that the collection bins are pressure-washed with city water on top of the concrete pad. The sump pump will collect any water on the concrete pad, and it is manually pumped to Tank No. 1. According to the facility representative, this used to be an automatic pump, but the pump filled with too much sediment. It was further explained that Tank Nos. 2 and 3 are cleaned once a month. The tanks are pressure-washed, and any sediment that collects is vacuumed out and put into Tank No. 1. Once Tank No. 1 becomes full, the facility pushes the supernatant back through the treatment system. Discharge - At the time of the inspection, the facility representative stated that the number of batch discharges depends on business. In the winter months, the facility will only batch discharge three or four times a month; in the summer, when business is more active, the facility will batch discharge three or four times a week. Wastewater is discharged from Tank No. 3 at a constant rate, with each batch discharging an average of 1,500 gallons and taking about two to three hours to complete. It was explained that the facility cannot drain the tanks completely because the piping could block with sediment, so they leave 100-200 gallons remaining after each batch discharge. The facility has one outfall, Outfall 001. This outfall is the sampling port, which conveys process water from Tank No. 3 to the District's sanitary sewer. The outfall is located inside the shed with Tank Nos. 2 and 3. EPA Classification of the Industrial User Based on observations and information received during the inspection, the facility is categorized as a Significant Industrial User, as defined in 40 CFR Part 403.3(v)(ii)). Page 3 of 5 Summary of Findings CWS Colorado, LLC NPDES ID# COPIU0013 January 28, 2025 Pretreatment Inspection Findings Follow up Action Items 1. At the time of the inspection, the inspectors observed a water meter to the east of the treatment shed to be leaking city water. Recommended Action It is recommended that the facility work with the District to repair this water meter and ensure that water doesn't continue to leak. Page 4 of 5 Report Review and Signature Drafter Name MONICA CROSBY Monica Crosby Digitally signed by MONICA CROSBY Date: 2025.02.26 13:31:24 -07'00' Address/Phone Number U.S. EPA Region 8 1595 Wynkoop Street 8ECA-W-NW Denver, Colorado 80202 303-312-6196 Date 02/19/25 Reviewer Name Address/Phone Number Date Al Garcia U.S. EPA Region 8 1595 Wynkoop Street 8WD-CWW Denver, Colorado 80202 303-312-6382 02/20/2025 Supervisor Signature/Name Address/Phone Number Date EMILIO Digitally signed by EMILIO LLAMOZAS LLAMOZAS 16:32:05 -07'00' Date: 2025.02.26 Emilio Llamozas U.S. EPA Region 8 1595 Wynkoop Street 8ECA-W-NW Denver, 80202 303-312-6407 Colorado 02/26/2025 Page 5 of 5