A regional survey of the microbiological water quality along the shorelineof the Southern California Bight

A regional survey of the microbiological water quality along the shoreline of the Southern California Eight (SCB), from Point Conception south to Ense nada, Mexico, was conducted during August, 1998, by 36 agencies under the c oordination of the Southern California Coastal Water Research Project (SCCW RP). Microbiological water quality was assessed by calculating the percenta ge of shoreline-mile-days that exceeded bacterial indicator thresholds for total and fecal coliforms, total/fecal ratios, and enterococci. Sample site s were selected using a stratified random sampling approach, with the SCB r ecreational shoreline divided into six strata: high- and low-use sandy beac hes, high- and low-use rocky shoreline, and perennial and ephemeral freshwa ter outlets. Samples were collected on a weekly basis at a total of 253 sit es, beginning on August 2nd, 1998 and continuing for five weeks. Samples we re analyzed by 22 participating labs using their normal methods (multiple t ube fermentation, membrane filtration, Colilert(R) and/or Enterolert(R)). A ll labs met testing criteria established through intercalibration exercises and quality control check samples distributed during the sampling period. Nearly 95% of the shoreline-mile days did not exceed daily and monthly bact erial indicator thresholds, demonstrating good bacteriological water qualit y along the SCB shoreline. Freshwater outlets, comprised mainly of storm dr ains, had the poorest water quality with 60% and 40% of the shoreline-miles exceeding monthly and daily thresholds, respectively. Freshwater outlets w ere also more likely to demonstrate exceedances by multiple indicators at a single site, and repeat exceedances at sites over the five-week period. Co mpared with the southern California beaches, Mexican beaches had nearly 5 t imes the number of exceedances for total and fecal coliforms, and neatly 8 times the number of exceedances for total/fecal ratios.