CA desalination slant wells prove promising in collecting seawater

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PACIFIC GROVE, CA, July 10, 2014 -- Recent data gathered from boreholes drilled along California's Central Coast indicates that an alternative way of collecting seawater for desalination may be feasible. California American Water (CAW) has proposed subsurface intakes wells that are to be drilled close to the coastline at a diagonal angle and will collect sufficient ocean water to produce nearly 10 million gallons of potable water per day to supply to the Monterey Peninsula.

Subsurface intakes have become the preferred technology for desalination plants among state regulators and environmental groups because they do not trap and harm marine life, unlike an open pipeline to the ocean. While the technology has been used in Europe and tested in the U.S., it is still considered a relatively novel approach. Near the Monterey Peninsula, where CAW's water supply project is proposed, it is being considered what slant wells will produce in terms of quantity and quality of ocean water and what their impacts will be, if any, on the underlying inland groundwater aquifer.

The company and key stakeholders of the affected area of the Salinas Valley groundwater basin convened a team of hydrogeological experts to research and help provide answers to these questions. The group studied the results of 13 boreholes that were drilled at several locations along the coast from Marina to Moss Landing area.

Boreholes are narrow shafts drilled into the ground that can be used to gather soil and water samples. In this case, data from the boreholes is being analyzed to see if subsurface slant wells can physically be drilled and to see what portion of the water underground is ocean water or groundwater. Agricultural interests in the Salinas Valley have supported the investigations in an effort to determine if the project will impact the groundwater supply on which they rely for irrigation.

While the tech memo does not conclusively answer that question, it shows promising results for the feasibility of slant wells, both in terms of geologic conditions and water quality. Data from the borehole study is being used to create groundwater models to further inform key environmental studies on the project. These studies are scheduled to be released in draft form later this summer. Simultaneously, CAW is seeking approval for a test slant well at the sand plant site in Marina that will also provide further data for the project.

In addition to the six boreholes drilled at the sand plant in Marina, seven other boreholes have been drilled at sites north of Marina, up to Moss Landing. The site near Salinas River State Beach at Potrero Road was considered the most favorable alternative to the sand plant site in Marina. The other Moss Landing locations showed mixed results and were determined to be far less favorable.

CAW's water project proposal, called the Monterey Peninsula Water Supply Project, is needed to replace water currently being drawn from the Carmel River, home to threatened fish and frog species. The Monterey Peninsula community, which is served by the river, faces water rationing of 35 gallons per person per day, compared to a national average consumption of around 100 gallons per person per day, and little to no water left over for commercial use, if an alternative water source is not developed in time to meet state-ordered river restrictions.

See also: "CA borehole investigation shows positive results for desalination project"


About California American Water

California American Water, a subsidiary of American Water Works Company, Inc. (NYSE: AWK), provides high-quality and reliable water and/or wastewater services to approximately 600,000 people. Founded in 1886, American Water Works Company is the largest publicly traded U.S. water and wastewater utility company. With headquarters in Voorhees, N.J., the company employs approximately 6,600 dedicated professionals who provide drinking water, wastewater and other related services to an estimated 14 million people in more than 40 states, and parts of Canada. For more information, visit www.amwater.com.

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