SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

TECHNICAL MEMORANDUM CH2MHILL Potential Groundwater Impacts Associated with the LEC Potable Supply Well PREPARED FOR: Catherine Lambert PREPARED BY: Torii Pezzetti,PG, CHG COPIES: Sarah Madams DATE: August 18,2008 A potable groundwater supply well is planned for installation at the Lodi Energy Center (LEC),located adjacent to the White Slough Water Pollution Control Facility (WPCF),off of North Thornton Road and just west of Interstate 5. The NCPA Combustion Turbine Project STIG #2 (STIG plant) is also located adjacent to the planned LEC. The LEC will obtain its potable water from an onsite groundwater well. Potable water will be used for eye-wash stations, drinking fountains, and sanitary facilities, as needed. The potable well is planned to produce approximately 450 gallons per day,Monday-Friday, and 90 gallons per day on Saturday and Sunday. The overall volume of potable water to be used by the facility is less than 0.4 acre-feet per year,with a maximum pumping rate of less than 1 gallon per minute. The LEC potable well will draw from the Eastern San Joaquin Subbasin within the highly productive San Joaquin Valley Groundwater Basin. Irrigation well yields in the fresh water- bearing formation underlying the subbasin range from approximately 650 to 1,500 gallons per minute (DWR,2006). Domestic wells in the Eastern San Joaquin Subbasin range from approximately 25 to 993 feet in depth, averaging approximately 242 feet (DWR,2006). Irrigation wells in the subbasin range from approximately 75 to 780 feet in depth, averaging approximately 349 feet (DWR,2006). Groundwater in the LEC vicinity flows generally from west to east (City of Lodi,2006). To the east of the facility, groundwater use for irrigation is higher than it is to the west (City of Lodi,2006). Therefore,the local gradient is consistently to the east. Regionally,the hydrologic gradient and groundwater movement are controlled by a pumping cone depression around the City of Stockton that persists throughout the year,and the groundwater moves in an east-southeasterly direction(City of Lodi,2006). The proposed LEC potable well is planned to be screened several hundred feet below ground surface below the known area of low-quality shallow groundwater. The target aquifer is the Laguna Formation,which has average irrigation well yields of 900 gallons per minute in the subbasin(DWR,2006). The well will be screened at a sufficient depth to be unaffected by the existing shallow low-quality groundwater. Several actions are proposed to provide extra surety regarding groundwater protection of the new potable well. 1. 75 feet of cemented surface casing will be installed instead of the required 50 feet at the well to provide extra protection GROUNDWATER TECHNICAL MEMO 1