Deep Water Current Profiling by LACSD

July 2002 - The Los Angeles County Sanitation Districts (LACSD) began a study of water currents and vertical temperature stratification over the Palos Verdes shelf in October 2000. The purpose of the study is to gain long-term information on the normal patterns, seasonal variability, and short duration variability in currents and temperature in the vicinity of the LACSD's ocean outfalls.

LACSD continuously evaluates cost-effective and environmentally-sound methods for wastewater conveyance, treatment, and reclamation/disposal. The extensive data set being produced from this study is expected to support ongoing and future efforts to optimize the discharge of treated wastewater from the LACSD's largest treatment plant, the Joint Water Pollution Control Plant.

LACSD currently has 13 sites off the Palos Verdes/San Pedro shelf, all with SonTek 0.5-MHz ADPs with a Janus, 4-transducer design. Each ADP has an external, 3-battery pack canister and a special integrated pinger option that outputs the operational status of the system. This feature permits the status of the system to be determined without recovery - especially when there is no immediate need to service the system.

The inshore sites are located in 35 m of water; the offshore sites are in 65 m. All the arrays are sampling for a 3-minute average, every 15 minutes. The arrays are serviced every three months, but have gone for as long as 5+ months without any loss of data.

• ADP