PACIFIC GROVE, CA, Dec. 30, 2013 -- Data collected from an ongoing investigation of geotechnical boreholes across the central California coast shows positive results for subsurface slant wells proposed for the Monterey Peninsula Water Supply Project's desalination plant.
The program, conducted by California American Water, comprises the drilling of eight geotechnical boreholes in three areas along the Monterey coast to study preferred sites for a desalination plant subsurface intake. Borehole studies were conducted at Moss Landing, Potrero Road and further south down the coast at property owned by Cemex U.S., Inc.
Boreholes are used to collect deep soil samples to evaluate the geological and water quality aspects of subsurface soil layers. Two of the three sites (Potrero Road and Cemex properties) show highly favorable conditions for locating the subsurface slant wells. The Cemex boreholes indicated an almost continuous layer of sands and gravels to a depth of 240 feet. The Potrero Road boreholes revealed a thick layer of clay at a depth of approximately 140 feet, indicating a separation between the proposed ocean intake zone above from the lower aquifers also known as an aquitard.
"At the northern site near Potrero Road, we have a nice, deep layer of sand filled with salt water with a well-formed aquitard below, which, if drawn from, would likely avoid impacts to the Salinas Basin," said California American Water Director of Engineering Rich Svindland. "At the Cemex site, we have a very thick sand layer below the ocean floor which will work nicely for the subsurface slant well sea water supply. Unfortunately, the Moss Landing sites have not been as promising. There we found intermittent clay layers mixed with silt and fine sand, without enough continuous sand layers to use any type of subsurface intake system efficiently."
The results were welcomed by the Monterey County Farm Bureau, which has been a working closely with California American Water in its goal to protect the Salinas River basin. "We are encouraged by these borehole drilling results, particularly at the Potrero Road site, indicating that the Salinas River groundwater basin may not incur harm from the source water intakes," said Norm Groot, executive director of the Bureau. "These results are an important part of the hydrogeologic testing and modeling that Cal-Am is performing at the request of Salinas Valley agricultural interests."
Although Moss Landing was not chosen as one of the preferred intake locations, the company had agreed to drill boreholes there as part of a settlement agreement to study alternative sites proposed by private developers. "We agreed to study Moss Landing because we wanted to conclusively demonstrate to the community we have explored all options in our quest for the best potential sites for this project," Svindland said. "Now that we have affirmed sufficient geological conditions, we will install a test slant well under the ocean floor to assure we have suitable water flow and quality for a fully operational desalination plant."
At the same time the test slant well is constructed, additional onshore monitoring wells will be drilled in and around the test slant well site to monitor the well's effects on surrounding groundwater aquifers. Data from the test slant well will provide detailed information on water quality conditions and flow rates at the site, which will be essential for the plant's final design. The North Marina Groundwater Model will be updated using the new data from exploratory borings, monitoring well data and test slant well testing. The updated model will then be used to evaluate future basin conditions in response to full-scale project operations.
California American Water has proposed a variable sized desalination facility as part of its three-pronged project to address the Monterey Peninsula's impending water supply shortage. The proposal includes aquifer storage recovery and recycled water projects that are presently advancing in planning and development. The desalination facility, however, will be the primary water producer of the three and is an indispensable component of the proposal.
The test well permit is pending review before the city of Marina. California American Water hopes to begin the construction of the well by December of 2014. For more information, visit www.watersupplyproject.org.
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 6,700 dedicated professionals who provide drinking water, wastewater and other related services to an estimated 14 million people in more than 30 states, and parts of Canada. More information can be found by visiting www.amwater.com.