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FOOTHILL ENGINEERING 12793 PADDY CREEK LANE LODI, CA 95240 PH. (209) 368-9381 FAX (204) 367-1163 Mr. Ronald Rowe January 25, 1999 San Joaquin County Public Health Services Environmental Health Division P. O. Box 388 Stockton, CA 95201 Site Code #1038 Subject: Michael D. & Sharon Olivarez, 300 S. California St. Stockton, Ca. Monitoring Well Information and Results of Sample Analytical Testing Dear Mr. Rowe: On 12/29/98,Del Tech Geotechnical Support Services secured water samples from the monitoring wells on the above stated property. The work was supervised by Foothill Engineering. All monitoring wells were in good condition and samples were taken using the standard recommended procedures. All samples were taken with a 1" stainless steel bailer after purging each well. Purge volumes and the physical properties of the ground water are attached in the Del-Tech field log. All samples were transported under chain of custody to Sherwood Labs of Hilmar, California. Samples from each monitoring well were transported from Sherwood Labs to BSK Laboratories for oxygenate analysis under chain of custody. All water sample analysis and groundwater elevations are summarized in the attached tabular form. FINDINGS The groundwater elevation in all of the wells has risen more than seven feet from the January 24, 1997 sampling date. The direction of groundwater flow is to the Northeast. MW-1 was analyzed to have highest concentration of gasoline contamination at 197,000 ppb. . MW-2 and MW-3 produced groundwater samples with lower levels of TPHg than previous samples from the same well. All monitoring wells showed higher groundwater elevations than previously recorded. The groundwater hydraulic gradient was calculated at S=0.004 with the slope in the Northeast direction. No free gasoline product or gasoline sheen was found in any of the groundwater samples. This was .:most likely due to the over screen condition that exists in all of the monitoring wells. CONCLUSIONS The groundwater elevation in all of the wells is approximately seven feet higher than last sampled. The raise in groundwater the calender year of 1998 is typical of all areas in the City of Stockton. All of the-monitoring wells have groundwater levels above the top of the monitoring well screens. This =may produce a sample condition that is not typical at the ground water surface.- All urface:All up gradient monitoring wells (MW-2 & MW-3) have produced samples with lower concentrations of TPHg than previously tested. The down gradient monitoring well (MW-1) has a higher concentration of TPHg than previously tested.