SCH Number 2015091060

Project Info

Title

Carlsbad Desalination Plant Intake and Discharge Facility Modifications

Description

The proposed CDP modifications to facilitate permanent stand-alone operation of the CDP consist of construction and operations of a new screening/fish-friendly pumping structure, a fish return system, and auxiliary facilities. Additional processing improvements could potentially increase annual average production from the existing 50 mgd to 55 mgd in the future. As a permanent stand-alone facility, a maximum of 299 mgd of seawater would be withdrawn from the Agua Hedionda Lagoon: up to 127 mgd for processing by the CDP, up to 198 mgd for flow augmentation used for brine dilution, and approx. 1 mgd for screen wash and fish return. The flow rates for processing and flow augmentation are interrelated such that to total flow rate, inclusive of processing, flow augmentation, screen wash and fish, return will not exceed 299 mgd. Up to 60 mgd of the diverted seawater would be converted to fresh water that is delivered to the Water Authority at the CDP property line. The remaining flow (up to 67 mgd) and treated backwash water from the pretreatment filters (up to 7 mgd). The salinity of the discharge prior to dilution is approx. 64 ppt (67 ppt with no backwash water included), whereas the average salinity of the seawater in the vicinity of the discharge tunnel is 33.5 ppt. Poseidon is proposing an initial dilution of the brine to 42 ppt or less prior to discharge to the ocean. This is accomplished by mixing the CDP discharge with the flow augmentation seawater. The combined CDP discharge, flow augmentation and fish return system flow rate is up to 244 mgd. As compared to the existing project operations, the modified CDP operations described above would achieve a potential 10% average annual increase in fresh drinking water production while reducing the total quantity of seawater required for processing and brine dilution purposes.

7 documents in project