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Sierra-Pacific Groundwater Consultants, Inc Y Y <br /> Geologists, Engineers, and Compliance Specialists <br /> April 17, 1998 <br /> R <br /> David Stavarek, SLIC Unit O 1998 <br /> Central Valley- California Regional Water Quality Control Board pPR 2 <br /> 3443 Routier Road, Suite ATAL HEALTH <br /> Sacramento, California 95827-3098 ENVIR�NMEN VICE <br /> PERMIT 1 SER <br /> S <br /> Subject: First Semi Annual 1998 Monitoring Report and Request For Regulatory Closure, Former <br /> PureGro Molasses Feed Product Facility, 2130 West Washington Street, Stockton,Sierra- <br /> Pacific Project No. 92-033 <br /> Dear Mr. Stavarek: <br /> In 1992, Union Oil Company of California(Unocal)authorized Sierra-Pacific Groundwater Consultants, Inc. <br /> (Sierra-Pacific)to conduct soils and ground-water investigations at a former PureGro Company(PureGro)feed <br /> product facility located at 2130 West Washington Street, Stockton, California. With continuing Regional <br /> Water Quality Control Board(RWQCB)oversight, Sierra-Pacific investigated feed product concentrations in <br /> soils at the facility and subsequently installed several shallow monitoring wells. The wells have been routinely <br /> monitored since 1993. The RWQCB and San Joaquin County Environmental Health Department(SJCEHD) <br /> have numerous Sierra-Pacific work plans and reports which extensively characterize the site. <br /> Ground-Water Monitoring <br /> The First Semi Annual 1998 Monitoring Report is enclosed for your consideration. On the basis of the current <br /> monitoring report, the results of detailed soils investigations, and five years of continuous ground-water <br /> monitoring, Sierra-Pacific requests on behalf of Unocal that no further environmental work be required <br /> at 2130 West Washington Street, Stockton. The situation is as follows: <br /> Ground-water monitoring began in 1993 and has continued since. Ground water was flowing west-southwest <br /> with a gradient of 0.0066 on March 9, 1998. Shallow ground water has flowed generally west since 1993. <br /> Water levels have risen and fallen in response to seasonal precipitation and infiltration of storm water. <br /> Nitrate concentrations detected in water samples from eastern wells have continued to be higher than <br /> concentrations detected in samples from the western wells. The nitrates are derived from off-site (eastern) <br /> sources. Nitrate-as-nitrogen(NO3-N)concentrations detected at MW-8 have fluctuated from 13.7 to 60 mg/1. <br /> NO3-N concentrations detected at MW-2 have attenuated with time from 47.3 mg/1 to 20 mg/1 in three years. <br /> (916)933-1468 <br /> 4911 Windplay Drive,Suite 4 EI Dorado Hills,California 95762 (916)933-3197 FAX <br />