Trash Talk

Jensen Precast system captures stormwater regulators’ attention

The California Water Resources Control Board recently certified the Jensen Deflective Separator (JDS) as a Full Capture System Device for Trash Treatment Control. Certification of the technology from Sparks, Nev.-based Jensen Precast dovetails revised water quality control plans—collectively known as the “Trash Amendments”—that the agency adopted in 2015 for drainage infrastructure serving public and private retrofit or new development projects.

JDS Offline unit plus diversion structure with a high-flow bypass weir.

The Los Cerritos Channel Sub-Basin 4 Stormwater Capture Facility is installed at the southeast corner of the Long Beach Airport. Jensen Precast tailored a flow splitting structure (center) flanked by JDS Hydrodynamic Separator units housed in 16-ft. diameter structures. PHOTOS: Jensen Precast
JDS iiJDS iii
The Jensen Deflector System Hydrodynamic Separator functions as a full-capture, swirl-concentrating stormwater treatment assembly. Absent moving parts, it can screen trash and debris from stormwater flows without blockage. Jensen Precast sizes the stainless steel cylinders’ metal screens with 2,400- to 4,700-micron (0.095- to 0.185-in.) openings. Screening capacity exceeds a target the California State Water Resources Control Board stipulates as part of the Full Capture System Device for Trash Treatment Control certification.

“Our stormwater customers in California will enjoy full compliance with all trash control stormwater regulations at both state and regional levels,” says Jensen Precast Stormwater Systems Division Manager Walter Stein, P.E. “We are helping reduce and, in most cases, eliminate 100 percent of trash discharged from our stormwater drainage systems. We believe performance of the JDS System to capture trash is unmatched.”

Along with requirements to meet certification standards, Jensen Precast engineers provided additional JDS System research findings with their State Water Resources Control Board application, including results of:

  • Full scale and repeatable trash removal efficiency testing;
  • Full scale testing with materials smaller than the required 5-mm particles; and,
  • Scour testing verifying 100 percent retention of previously captured solids during flow bypass events.

Stormwater treatment remains a key research and product development area for Jensen Precast, which continues to commit the necessary resources for system verification and performance tests. “No other technology being offered has verified the bypass retention efficiency,” Stein affirms. “Once trash and debris go into a JDS System, they’re not getting out until properly cleaned. Jensen Precast is an innovator in this area of stormwater treatment, providing a proven system superior to all others.”


Full Capture System Device certification came on the heels of a successful JDS installation aimed at protecting southern California’s 17,700-acre Los Cerritos Channel Freshwater Watershed. Through dry weather runoff and first flush stormwater flows, the urbanized, commercial, and industrial watershed was prone to eclipsing the U.S. Environmental Protection Agency total maximum daily load (TMDL) limit for total suspended solids and several heavy metals.

Seven cities in the watershed were bound by an EPA mandate to bring TSS and heavy metals below the TMDL levels. Bellflower, Cerritos, Downey, Lakewood, Long Beach, Paramount, and Signal Hill each needed a solution to manage and monitor water quality in their respective areas. Installing multiple stormwater treatment systems to eliminate the pollutants would be more costly and perhaps not as efficient as a single large diversion, treatment, and infiltration station on the Los Cerritos Channel—at the bottom of the entire watershed.

The cities formed the Los Cerritos Channel Watershed Group to streamline the infrastructure; instead of each addressing stormwater treatment individually, one large regional system would be built to collectively remove pollutants and curb costs. The Los Cerritos Channel Sub-Basin 4 Stormwater Capture Facility eliminates most polluted dry weather runoff while diverting, treating, and infiltrating first flush stormwater flows impacting the watershed.

Jensen Precast engineers worked on the project with consulting firms Tetra Tech Inc., Long Beach, and GHD, San Diego, plus design-build contractor Mike Bubalo Construction Co., Baldwin Park, Calif. The producer designed, fabricated, and delivered a flow splitting structure and dual JDS Hydrodynamic Separator units deployed inside two 16-ft. diameter precast concrete structures to capture suspended solids, trash and debris. The Los Cerritos Channel Sub-Basin 4 Stormwater Capture Facility, notes Mike Bubalo Construction Vice President Dave Sorem, “Takes in 166 cubic feet per second through the transition structure, then into two hydrodynamic separators, then into an infiltration gallery. I don’t know of any other system that could do that.”

“Our goal is to provide the best forward thinking solution for every customer every time,” affirms Jensen Precast President Eric Jensen. “Certification of the JDS System is a great example. By streamlining state and regional compliance expectations, our engineering and contractor customers can complete their projects faster and more cost effectively.”