Case Study: Boatyard
Southern California Boatyard Faces Challenges with Copper and Zinc NAL Exceedances
A leading boatyard in Southern California engaged Storm Water Systems to manage a heavy amount of TSS (total suspended solids) and unexpectedly high levels of copper and zinc in its storm water run-off.
While the boatyard is permitted to discharge 30,000 gallons per month to the sanitation department, it could not discharge into it harbor unless absolutely necessary. Also, due to its proximity to an impaired water body, the boatyard had to prepare its storm water compliance measures to meet future TMDLs that will eventually apply to its TAL exceedances.
In the first year of operation, our StormPROOF™ Treatment System experienced unexpectedly high levels of copper and zinc when sampling. Further complicating matters, the TSS levels were so high that – during rain events – the solids media bags had to be changed every 30 minutes to prevent exceedances.
The Storm Water Systems’ engineering team evaluated different materials that limit the mobility of copper and zinc, and developed a proprietary mix of media to apply to the problem. Initial results demonstrated pH levels that exceeded NAL requirements. In short order though, we found the right combination of media using an innovative approach to reduce copper and zinc levels, while not risking excess pH levels.
In conjunction with the copper and zinc management, we enhanced our StormPROOF™ Treatment System modules with an auto-backwashing screen filter and additional bag filters to increase solids-handling capacity and dramatically increase the filter-service-interval time from 30 minutes to as high as eight hours, depending on the amount of pollutants in the water intake.
Success was realized when year-two benchmark studies of the newly developed media package demonstrated that TSS levels were reduced by 98.6 percent, copper by 99.9 percent, and zinc by 93.3 percent. Interestingly, even a 99.9-percent reduction in copper was still not sufficient to get the facility below an NAL exceedance, which led the Storm Water Systems’ engineering team to further modify the media package.
Ultimately, these three pollutants were brought well below NAL (and projected TAL) exceedance levels. And, despite one of the rainiest seasons in years, there were no unintended discharges into the boatyard’s harbor.