Data being collected from California American Water’s ongoing geotechnical borehole investigation shows promising results for the subsurface slant wells it has proposed for the Monterey Peninsula Water Supply Project’s desalination plant. The company will post a work plan for the borehole and test well program on its project website, www.watersupplyproject.org. The plan is the result of numerous meetings and analysis by hydrogeologic experts assembled as part of the project’s settlement agreement. Over the last four months, California American Water has drilled eight geotechnical boreholes in three areas along the Monterey coast in its study of 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. “The results thus far are very promising,” said California American Water Director of Engineering Rich Svindland. “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. 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 Monterey County Farm 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 one of California American Water’s 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. “The borehole study so far, appears to clearly address the question of whether we can engineer and build this without impacting the deeper aquifers,” said California American Water president Rob MacLean. “From the project’s outset, we have been focused on the most expeditious path to regulatory approval and one that is most cost-effective for our customers. These results affirm what our initial studies had projected and should be welcome news to our customers and the area’s farming interest whom we have worked very closely since we filed the project’s application.”
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.In proposing the facility, California American Water faced several potential legal and environmental roadblocks. The first was concern over environmental impacts to sea life, which the company addressed through a slant well design that will feed water to the plant using slant wells below the ocean floor, thereby avoiding the potential for biological entrainment all together. The second largest obstacle was posed by agricultural interest over possible seawater intrusion into the Salinas Valley Aquifer, which is a major irrigation source for farmers. California American Water preliminary modeling showed they could potentially draw from the sea water zone above these deeper aquifers. Data from the borehole sites confirmed the anticipated geological conditions on which these findings were based and now provides field data and scientific conclusions that support the company’s planned sites. “The Salinas Valley Water Coalition is pleased that the technical team's work plan has been completed consistent with the settlement agreement,” said Salinas Valley Water Coalition President Nancy Isakson. “The coalition relies on science and law as the foundation of their positions and we are pleased that our hydrologic consultants were part of the technical team preparing the work plan. This work plan is the basis by which the data and various hydro-investigations, including the test well results, will be analyzed in order for Cal-Am to prove no harm to the Salinas River Groundwater Basin and its water right holders. The boring's to date appear to be encouraging, but they are one tool in the suite of tools to prove no harm and we look forward to the final report and analyses.”
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 on this and other news and updates about this project, please visit the project website at www.watersupplyproject.org. 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.