In February, the San Francisco Bay Regional Water Quality Control Board adopted new measures for San Mateo, Alameda, and Contra Costa counties to control stormwater runoff. Such runoff causes significant erosion and has become a major source of pollutants like mercury, copper, petrochemicals, and other poisons that are either trapped in the soil from past contamination or generated from such things as spilled motor oil, lawn and garden pesticides like diazinon, or copper dust from brake pads.
“Stormwater is the biggest problem mainly because we spent the last 40 years controlling point sources [like factories and refineries],” said Water Board spokesman Wil Bruhns. “It’s the second largest source of mercury in the Bay. In every urban creek we’ve looked at, we’ve found diazinon and other things at toxic levels.”
Stormwater runoff includes all the water that runs off lawns, streets, and parking lots into curbside drains. As a source of mercury, it far outstrips all current industrial emissions. Runoff also erodes creeks, turning them into bare gullies with increasingly erratic flows.
Under the new regulations, starting in 2005, new developments with one acre or more of impermeable surface (roof or pavement) must include measures to reduce runoff. The threshold will drop to 10,000 square feet of roof or pavement in 2006. According to Bruhns, runoff mitigation measures could be as simple as a grassy swale to absorb rain running off a parking lot, or as complex as an underground drainage and filtration system.
Leo O’Brien, executive director of the watchdog group Waterkeepers Northern California called the new provisions “a modest step forward.” But he said much more must be done, including requiring the retrofit of existing development — even if those retrofits involve little more than many grassy swales. “If we developed and designed and built our cities appropriately, and retrofitted our urban landscape,” O’Brien said, “we could reduce the effects of things like dioxin, copper, and mercury.”
