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Case Study

Storm Filter Replacement and Oil/Water Separator Cleaning in Gaithersburg, MD 

Gaithersburg, MD

Gaithersburg, MD

Commercial

Stormwater Systems

A commercial property in Gaithersburg, Md., received a notice of violation (NOV) tied to two stormwater treatment systems. Oil, sediment and debris had accumulated in both, and an underground filtration chamber held 153 spent filter cartridges. AQUALIS was contracted to clean both structures, replace all 153 cartridges and return the systems to full working order. 

The Challenge

A Notice of Violation NOV is a formal notice that a stormwater system isn’t meeting maintenance or performance requirements set by the city, and owners must correct the issue within a set timeframe. The violation for this property was issued because the stormwater filtration devices were no longer filtering runoff. 

As rainwater runs across parking lots, it can pick up sediment, debris, motor oil, tire particles and other pollutants and carry them toward the drainage system. Stormwater treatment systems are designed to capture those pollutants before they leave the property.

This property relied on two different types of treatment. The first was an oil/water separator, a type of best management practice (BMP) that holds runoff long enough for oil to float to the top while heavier sediment settles out. As these materials accumulate, the separator has less capacity to treat incoming runoff. At this property, the structure needed to be cleared of accumulated oil, sediment and debris.

Site overview filters before cleaning technician cleaning filter Technician disassembling filters empty filer chamber filter re-installed into chamber Filters after repair

The second was an underground storm filter chamber. Inside, rows of cartridges filled with filter media capture fine sediment and other pollutants as stormwater passes through. Like an air filter, the media collects material over time and eventually needs to be replaced. All 153 cartridges in the chamber required replacement. 

Access and safety added another layer of complexity. The chamber sat beyond the edge of the parking lot, requiring the jet/vac truck and other equipment to cross a landscaped grass area. Concrete traffic barriers also blocked the access route. Once the chamber was cleared of accumulated sediment, technicians would need to enter the underground structure to replace the cartridges, requiring trained personnel and confined space procedures.

 

The Solution 

AQUALIS first established a controlled work area with barricades and signage to separate the work zone from customers and staff. 

To provide equipment access without damaging the landscaped area, crews installed approximately 45 feet of track mats between the parking lot and storm filter chamber. The mats distributed the weight of the jet/vac truck and provided a stable route across the grass. A skid steer, a compact loader, used to move heavy materials in tight spaces was used to relocate the concrete traffic barriers and transport filter media and equipment around the site. 

The crew cleaned the oil/water separator using a jet/vac combination truck. High-pressure water loosened accumulated oil, sediment and debris while the vacuum removed the material from the structure, clearing the buildup that had reduced the separator’s treatment capacity. 

Before confined space entry, a jet/vac truck was used to remove accumulated sediment from the storm filter chamber. Trained technicians then entered the chamber under confined space protocols to remove and disassemble all 153 spent cartridges. Each replacement 18-inch cartridge was assembled onsite and installed with a new quarter-turn adapter to create a secure connection within the treatment system. 

After installation, technicians inspected and documented conditions inside the chamber, establishing a baseline for future maintenance and compliance reporting. All material removed from the systems was transported to an appropriate offsite disposal facility before the crew cleaned the work area and demobized.

 

The Results 

With the oil/water separator cleaned and all 153 storm filter cartridges replaced, AQUALIS returned both treatment systems to working order and addressed the maintenance deficiencies associated with the NOV. 

The final inspection also documented conditions inside the chamber, giving the property owner a record of the completed work and a baseline for future maintenance and compliance reporting. By restoring the systems’ treatment components, the property can once again capture oil, sediment and other pollutants from stormwater runoff as designed. 

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