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NBPL WQ-Based NPDES Storm Water Toxicity Specification Study Update

	Aerial view of Naval Submarine Base San Diego. (U.S. Navy photograph)

On September 11, 2002, the Regional Water Quality Control Board San Diego Region (SDRWQCB) adopted an NPDES permit covering Naval Base Point Loma (primarily Naval Submarine Base San Diego) that included language that "undiluted storm water runoff associated with industrial activity shall not produce less than 90% survival, 50% of the time, and not less than 70 percent survival 10% of the time, using standard test species and protocols" within two years of the permit's adoption.

The same conditions were also adopted in the Naval Base San Diego and Naval Base Coronado NPDES permits, thus imposing these conditions on all major Navy facilities on San Diego Bay. Failure to meet these standards would result in the requirement that the Navy capture and treat the first ¼-inch of rainfall at a capital cost estimated at $100 million. The Navy was able to convince the SDRWQCB to allow the Navy to evaluate its storm water discharges and provide a scientific basis for proposing an alternative toxicity standard that would potentially be less stringent but still protective of the receiving environment. (see Marine Environmental Update, Vol. FY02, No. 4).

The sampling methodology consisted of a combination of onshore sampling, offshore sampling and laboratory analysis. Onshore measurements were made using an American Sigma™ automated water sampler upgraded with a rain gauge, conductivity and turbidity sensor, and an area-velocity flow meter. Offshore measurements were made using the Navy's Marine Environmental Survey Capability (MESC). MESC surveys were performed before, during and after storm events to map storm water plumes and quantify spatial and temporal impacts to the receiving water body. Discrete water samples were collected at the location where the outfalls discharged into the receiving water before, during, and after the storm event to serve as a comparison with samples collected directly from the outfall pipe.

Results to date have revealed the following:

• Storm water plumes from SUBASE San Diego are short lived and were confined to the inner pier area;
• While the proposed 90% toxicity requirement in storm water was usually exceeded, there was no toxicity observed in any receiving water sample;
• Copper and zinc were elevated in the storm water discharge but water quality criteria were never exceeded in the receiving water;
• Copper and zinc were the contaminants causing toxicity in all samples; and
• Measures of receiving water chemistry and toxicity suggest that the bay can assimilate storm water from SUBASE San Diego without impacts to beneficial uses.

Future efforts include a field-deployed toxicity laboratory study at Naval Base San Diego (full-storm characterization of receiving water toxicity at point of discharge using flow-through bioassays) and a toxicity field study at Naval Base Coronado in 2004-2005. The results of these studies will be presented to the SDRWQCB prior to the 2006 permit review date.

Volume FY04, Number 4