Rain Brings Urban Runoff

December 12, 2011 | 5:07pm

The storm that blew into the county Monday has prompted a general advisory for local beaches.

The Department of Environmental Health warns swimmers, surfers, and other ocean users that rain can significantly raise bacteria levels in ocean and bay waters, especially near storm drains, creeks, rivers, and lagoon outlets that discharge urban runoff. Urban runoff may contain large amounts of bacteria from a variety of sources such as animal waste, soil, and decomposing vegetation.

While many coastal storm drains within San Diego County are permanently posted with white metal warning signs, additional temporary warning signs are not posted for general advisories. Activities such as swimming, surfing and diving should be avoided in all coastal waters for 72 hours following rain. This includes all coastal beaches and all of Mission Bay and San Diego Bay.

Elevated bacteria levels can persist after a rainstorm depending upon the intensity of the storm, volume of runoff and ocean and current conditions.