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MZNMA <br /> Working to Restore Nature <br /> 1710 Main Street <br /> Escalon, CA 95320 May 8, 1992 <br /> Phone (209)838-3507 <br /> FAX (209)838-3509 �` � <br /> Ms Mary Meays <br /> San Joaquin County Public Health Services MAY 11 1992 <br /> P O. Box 2009 ENVIRONMENTAL HEALTH <br /> Stockton, CA 95201PERMiT/SE"v.�r5 <br /> RE: Quarterly Monitoring Report, January through March 1992, Site Code 1864, <br /> 26056 Thornton Road, Thornton, CA <br /> Dear Ms Meays <br /> This letter report details RESNA Industries' (RESNA) groundwater monitoring activities during <br /> the first quarter of 1992 at 26056 Thornton Road, Thornton, California Activities during the <br /> quarter included monitoring of groundwater, sampling for dissolved hydrocarbons from the six <br /> monitoring wells on-site, and evaluating the petroleum hydrocarbon concentrations in the <br /> groundwater at the site <br /> Groundwater Monitoring and Sampling <br /> RESNA personnel performed quarterly groundwater monitoring and sampling on March 4, 1992 <br /> Field work consisted of measuring the depth-to-water (DTW) and subjectively analyzing the <br /> water from wells MWl through MW6 for the presence of sheen and floating product <br /> Groundwater was monitored again on March 16, 1992 The water table elevation has risen <br /> approximately 2 3 feet since October, 1991. The rise in the water table is likely due to seasonal <br /> fluctuations The groundwater monitoring data is summarized in Table 1 <br /> The groundwater gradient beneath the site flows southwest under a gradient of approximately <br /> 0 0007 ft/ft, or 3 8 feet per mile Groundwater gradient maps for two monitoring episodes <br /> (March 4 and 16, 1992) are shown on Figures 1 and 2 Due to an anomalous data point at <br /> MW4 on March 4, 1992, the wellheads were resurveyed and groundwater monitored on March <br /> 16, 1992. The figures reflect the resurveyed/wellhead elevations <br /> On March 4, 1992, groundwater samples were collected from the site wells, after stabilization <br /> of pH, electrical conductivity (EC), and temperature The monitoring wells were purged and <br /> sampled according to RESNA's Quality Assurance/Quality Control Plan Well purge logs are <br /> included in Attachment 1 <br /> QR032692 7PL <br />