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k_ California Regional Water Quality Control Board Central Valley Region Linda S.Adams Arnold Secrelaryfor Sacramento Main Office Schwarzenegger Environmental 11020 Sun Center Drive 4200,Rancho Cordova,California 95670-6114 Governor Proleclion Phone(916)464-3291 •FAX(916)464-4645 http://www.waterboards,ca.gov/centralvalley 15 December 2006 �RENED Ben Hall, Director DEC 1 9 2006 Environmental Services and Programs SAN JOAQUIN COUNTY Musco Family Olive Company ENVIRONMENTAL HEALTH DEPT. 17950 Via Nicolo Tracy, CA 95377-9767 REVIEW OF GROUNDWATER QUALITY AND HYDROGEOLOGY A T MUSCO FAMILY OLIVE COMPANY, TRACY, SAN JOAQUIN COUNTY 1' Staff recently evaluated the'.groundwater data from the Musco Family Olive Company (Musco) facility and also reviewed Musco's Background Groundwater Quality Report dated �. 30, July 2004 (see enclosed Memorandum dated 12 December 2006). This evaluation was conducted to determine whether the discharge of waste has impacted the quality of the groundwater underlying this facility and to evaluate recommendations made in the 2004 r report. Because on-site monitoring well data was not collected prior to the initiation of land discharge, pre-discharge groundwater quality at the Musca property cannot be established. In the absence of other data, Regional Board staff determined in WDR No. R5-2002-0148 that I Musco's production well should be used for groundwater quality limits. In the 2004 Report, Musco proposed background concentrations based on "ambient concentrations." Staff has reviewed this proposal, but, as described in the enclosed Memo, has determined that the "ambient concentration" method is inappropriate-and that background concentrations outside the influence of the Musco's discharge must be determined. In addition, staff's review finds I that the current groundwater monitoring program is inadequate to properly monitor groundwater quality throughout the entire site or to determine whether there are any off-site impacts. Musco has been land applying high-strength wastewater to upland fields since at least 1991. Currently, Musco uses approximately 200 acres for land application. Staff's review finds that process wastewater storage and application has resulted in increases in groundwater concentrations over time, 'causing degradation or pollution of the underlying groundwater. Although background groundwater concentrations have not yet been determined, the data clearly,shows that the continuation of current discharge loading rates to land is not acceptable. As described in the Memo, staff recommends that Musco install additional wells to further define and delineate the groundwater impacts, and to install additional wells off Musco's property to determine background groundwater concentrations for the shallow and deep zones. Staff also recommends the use of interim background groundwater concentrations for the deep zone using the Regional Well. California Environmental Protection Agency j �d� Recycled Paper