Water Quality Assessment: Urban Runoff Impacts And Economic Implications In Orange County, California.pdf

Key Findings from Multiple Sources (1998-2001)

This summary synthesizes key findings regarding water quality in southern Orange County, California, focusing on impacts from urban runoff. Data originates from various sources including the San Diego Regional Water Quality Control Board, US Army Corps of Engineers (USACE), Grand Jury reports, and Municipal Stormwater Copermittees.

Water Quality Concerns:

Acute Metals: 94% of NPDES stormwater samples exceeded California Toxics Rule (CTR) acute metal limits at point of discharge to receiving waters in the 1999/2000 reporting period.
Bacteria: High levels of total and fecal coliform and enterococcus bacteria were detected throughout the Aliso Creek watershed, exceeding REC-2 standards at all monitored stations except one. Similar elevated levels were observed in a surf zone near Prima Deshecha creek outlet by SERRA.
Historical Contaminants: USACE studies show historical increases in lead, copper, chromium, and nitrates in San Juan Creek, Trabuco Creek, and Oso Creek from 1992-1995.
Urban Runoff Impacts: The USACE Aliso Creek Watershed Management Feasibility Study attributes water quality deterioration primarily to stormwater runoff from urban developments.

Grand Jury Findings:

Despite public education efforts required by the National Pollutant Discharge Elimination System (NPDES), significant amounts of trash still enter County-maintained flood control channels and storm drains, ultimately impacting water quality.
Beach advisory postings for high bacteria levels have remained consistent between 1999 and 2000, indicating little improvement in coastal water quality.

Economic Implications:

Beach closures due to bacterial pollution negatively impact local economies by reducing tourism and recreational activities.

Proposed Solutions:

Several coastal communities are implementing or proposing dry-weather diversions to capture urban runoff before it enters streams and ultimately beaches, aiming to reduce bacteria levels and protect public health.