Coastal Water Quality

The Sanitation Districts' ocean water quality monitoring program has two components: nearshore/offshore water quality monitoring and a nearshore light energy survey. The results of these monitoring efforts can be found in the Coastal Water Quality chapter of the JWPCP Biennial Receiving Water Monitoring Report.

1. Nearshore/Offshore Water Quality Monitoring:

The purpose of Nearshore/Offshore Water Column Monitoring is to assure that California Ocean Plan limits for dissolved oxygen, pH and light transmission are being met in the area near the outfalls, and to assure that nutrients from the discharge are not causing objectionable aquatic growth or otherwise degrading the receiving water biota. The data from this monitoring are also intended to contribute to a regional understanding of seasonal patterns in nearshore water column structure.

For the Nearshore/Offshore Monitoring program, monitoring is conducted at
48 stations on a quarterly basis. At each station, continuous profiles from surface to bottom (or to a maximum depth of 100 m) for dissolved oxygen, temperature, salinity, light transmissivity, chlorophyll-a, and pH (hereafter referred to as a CTD profile or sample) are measured. Concurrent with the CTD sampling, water samples are collected at a subset of 24 stations and analyzed for ammonia nitrogen at the surface, 15, 30 and, where depth allows, 45 m below the surface to identify the location of the effluent plume.

The Sanitation Districts conduct the Nearshore/Offshore Monitoring program cooperatively with monitoring groups from four neighboring agencies, including the City of Los Angeles, the Orange County Sanitation Districts, City of San Diego and the City of Oxnard. All five agencies sample along similarly arranged transect lines, with equivalent spacing of stations both along the coast, and from the shore to offshore. The Nearshore/Offshore Monitoring program data collected by the Sanitation Districts are incorporated with data from the other participants to produce a regional data set which includes over 300 CTD profiles collected between Ventura and San Diego Counties. The regional data sets produced by the five agencies are provided to the Southern California Coastal Ocean Observing System (SCCOOS) group, which makes selected data available on its web site.



Map of Offshore CTD Sampling Sites

2. Nearshore Light Energy Surveys:

The purpose of the Nearshore Light Energy Survey is to assure that the discharged effluent does not reduce natural light below levels sufficient to ensure protection of benthic algal communities, such as the giant kelp beds so prominent in the Palos Verdes coastal waters.

For the Nearshore Light Energy Survey, the OMRG monitors light energy at seven nearshore stations on a monthly basis. The stations are located along the 18 m isobath around the Palos Verdes headland. At each station, profiles of light energy are made from surface to bottom and compared with ambient light levels.



Map of Nearshore Light Energy Monitoring Sites