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r' FOOTHILL • �,-•.�; F�NGINEERING 112793_PAbDVjCREEK LANE LOM, CA 95240 PH. (2&9) 368-9381 FAX (209) 367-1163 Ms. Carol Oz December 17, 1999 Szn 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. 1. Monitoring Well Information and Results of Sample Analytical Testing of 11/2.4199 2. Preliminary Report of CPT#1 and CPT#2 Dear Ms. Oz: Please find below the procedure and results of quarterly monitoring well groundwater samples. PROCEDURE On 11/24/99, 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 extracted using the tube with check valve pump system. Purge volumes and the physical properties of the ground water are attached in the Del-Tech field log. The replacement monitoring wells were sampled for analysis and the original monitoring wells were used to establish groundwater elevation.Future horizontal elevation surveys will tie the original and the replacement wells to the same City of Stockton datum. All samples were transported under chain of custody to Sherwood Labs of Hilmar, California for analysis by EPA methods 602 and 5030/8015 . Samples from each monitoring well were transported under chain of custody from Sherwood Labs to Entech Analytical Labs,Inc.for oxygenates analysis by EPA method 8260M. All water sample analysis and groundwater elevations are summarized in the attached tabular recap sheet. Original data sheets from laboratories are attached. FINDINGS The groundwater elevation in all of the wells has lowered +/- 1.1' from the last sampling date (7/19/99). The direction of groundwater flow is to the Northeast (see attached map). MW-IR and MW-2 R were analyzed to have the highest concentration of gasoline contamination at 152000 ppb &83300 ppb. MW-I Rand MW-2R produced groundwater samples with lower levels ofTPHg than the samples of 7/19199 from the same well. MW-3R had lower concentrations of TPHg than the 7/19/99 sample. The groundwater hydraulic gradient was calculated at S=0.003 with the down slope in the Northeast . direction. 1 _ � s