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First Flush: Rain's Effect on Ocean Water Quality

San Luis Obispo received its first significant rainfall the night before we collected samples on the morning of January 4th,  so we got a good picture of what effect early season runoff had on creek and ocean water quality.

Numbers along San Luis Obispo Creek were from 3X to 140X the maximum state standard to safe contact with the water with the water at Avila Beach, where San Luis Obispo Creek enters the ocean,  at the lower end of the readings but still exceeding the maximum safe levels by 3 times.

Even more serious were the conditions at Sewers, a very popular surfing spot in Shell beach. The water out along the reef was OK but the discharge from the storm sewer that empties into the ocean at the base of the reef posted a number of 17,329, v.s. 106, which is the maximum number for safe water contact.

This photo is of the two samples from Sewers. The samples are prepared, sealed into a tray, incubated for 24 hours and then exposed to UV light. The cells that fluoresce are counted and converted to the reading. The tray on the left with almost all of its cells lit is the sample from the storm sewer while the tray on the right is the sample from the water off of the reef.

The Chapter’s Blue Water Task Force volunteers go out every Thursday morning and collect samples from San Luis Obispo creeks and beaches that are then tested for enterococcus bacteria, which is the EPA’s lead indicator for the presence of human waste.  Our results are posted mid-day every Friday at