San Diego County Water Authority to build 100-mgd Water Treatment Plant
The San Diego County Water Authority board of directors took action at a special meeting today to approve construction of a 100-mgd water treatment plant. The plant will help alleviate the growing need for additional treated water capacity that has strained the Water Authority’s ability to meet demands over the last three summers.
The water treatment plant, the first to be built and operated by the Water Authority, will be located in Twin Oaks Valley north of San Marcos.
"The completion of the water treatment plant in 2008 will provide additional treated water capacity needed to address the ever-increasing demand for drinking water in San Diego," said Board Chairman James Bond. "The selection of membrane technology will ensure a consistently reliable operation as well as the highest quality treatment."
The board certified that the environmental impact report for the water treatment plant was completed in compliance with CEQA, the California Environmental Quality Act. An EIR evaluates a proposed project's impacts on the environment and recommends mitigation measures to reduce or eliminate those impacts. The board uses information in an EIR to help determine whether or not to approve a project.
The board awarded a contract to CH2M Hill Constructors, Inc. to design and construct the treatment plant and operate it for 15 years. The contract includes $159 million to design and build the treatment plant and a base operation and maintenance fee of $6 million per year.
The water treatment plant is part of the Water Authority’s $3.2 billion Capital Improvement Program to reduce over reliance on a single supplier and improve water reliability by diversifying the region’s water supply portfolio. The CIP includes the development of seawater desalination, increasing regional water storage capacity and construction of new and rehabilitating existing facilities to increase operational flexibility and capacity to deliver water. Construction of the treatment plant will begin in early 2006 with completion scheduled for spring 2008.
In awarding the design-build-operate contract to CH2M Hill, the board selected the submerged membrane treatment process over two other proposed conventional treatment processes. It was determined that the membrane treatment process will produce a higher quality water and be less expensive then the conventional processes and will be more environmentally friendly.
With membrane treatment, untreated water is forced through very fine holes, or pores, in membrane fibers. The pores are large enough for water molecules to pass through, but small enough to reject contaminants and particles, achieving a high removal rate. As long as water moves through the membranes, the contaminants are removed making it extremely efficient and reliable.
While conventional treatment is also safe and effective, it is more susceptible to quality changes and does not reach as high a degree of contaminant removal as membrane treatment.