Hybrid Low Impact Development/Best Management Practices for DoD Industrial Site Storm Water Runoff
Mr. Gary Anguiano | Naval Facilities Engineering and Expeditionary Warfare Center
The Department of Defense (DoD) is under increasing pressure from regulators and local communities to protect water bodies by reducing the total magnitude and concentration of industrial site pollutants being discharged within storm water runoff into harbors, bays, lakes, and streams. The objective of this project is to demonstrate a small footprint (800 to 1,600 square feet), shallow depth (3 to 6 feet) storm water technology for industrial areas that merges structural Best Management Practice (BMP) and Low Impact Development (LID) principles to decrease the concentration of pollutants such as suspended solids, dissolved and particulate metals, and oil and grease to the most stringent National Pollution Discharge Elimination System (NPDES) permit requirements. The hybrid technology can be applied to new construction of industrial facilities, or to retrofit existing industrial sites that are faced with meeting increasingly stringent NPDES discharge limits.
The storm water technology is a full-scale 240 gallons per minute (gpm) hybrid LID/BMP system designed to decrease contaminant concentrations within runoff to ultra-low NPDES permit limitations (e.g., ≤2.9 μg/L copper). The system’s innovative feature is the merging of a sustainable LID with a structural BMP along with a 10,000 gallon effluent storage system. The LID’s engineered soil and plant matrix mimics the contaminant removal mechanism of a natural swale within a small footprint and exceeds traditional swale percolation rates, while the structural BMP polishes the LID. The accompanying storage tank will hold a portion of the effluent to irrigate LID plants during dry periods, or it can be used for other site-specific applications. Conventional LID systems require a large area of land and long percolation times to process storm water runoff. The small footprint and rapid processing times of this technology are desirable at industrial sites where usable space is at a premium. Success of the project will be measured by meeting the stringent NPDES requirements of Joint Base Pearl Harbor-Hickam for copper and zinc removal.
Successful demonstration of this technology will provide the DoD with a sustainable method for reducing particulate and heavy metal contaminant concentrations within industrial site storm water runoff, thereby complying with NDPES permits and avoiding Notices of Violation (NOVs) from regulating agencies. There are presently no other technologies that are both effective and economical for treating storm water runoff to the new NPDES levels for copper, which can be as low as 2.9 μg/L. The next viable alternative is to contain all of the storm water from the industrial site, and pump to an aboveground storage tank for slow release to a sanitary sewer system. Release must be done after peak sanitary sewer flow so that the receiving wastewater treatment plant is not overwhelmed by the added storm water flow. Typical sanitary sewer cost ranges from $3-5 per 1,000 gallons. This alternative for even a small 1-acre site could cost DoD more than $1 million on initial implementation alone. The technology to be demonstrated is capable of treating industrial storm water to levels below emergent NPDES permit limits at an estimated capital cost less than $100,000 per acre. (Anticipated Project Completion - 2020)