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C LEARWA-TR C .R. .O U. P, I N C.. : The monitoring`wells were sampled ori May,26, 1995 under the ,supervision of Mr. Ron Rowe of the PHS/EHD., Prior to.sampling, all wells were gauged to the nearest hundredth.:of a -foot and then purged,..of a minimum` .of three well: volumes. Temperature; pH and conductivity 'of the purged :water were monitored to ensure collection ,of a representative groundwater- sample. ' Groundwater samples were collected.from the monitoring wells using.dedicated polyethylene bailers and placed. .n appropriate sample containers. 'Samples were.-labeled, documented on a chain-of- custody form,., and stored in a cooler for transport to °PACE, Inc. (PACE), a state-. certified laboratory located nr Petaluma; California. Well . gauging; purging and sampling data is presented in'A endix A. All groundwater-sam les.were analyzed i PP g P . Y for TPHg and TPHd by EPA Method 8015 (modified), and for BTEX by EPA Method 8020 (modified). .4.0 RESULTS AND DISCUSSION = 4.1 Water Level 'MonitoringData On May 26; 1995, the depth to ground water'in' 4he three wells ranged-from 17.87 to 19.14 feet b . Groundwater flow was estimate d t gs a o. be northerly •at an approximate gradient of 0.06%; the estimated groundwater ,elevation contours are shown on ; Figure 3. The groundwater flow .direction is approximately .the reverse of .that measured during-the previous quarter.' One .possible explanation is that water levels on the.Stanislaus`River were sufficiently high curing this gauging event -to cause a loss of water. from. the river to .the aquifer,- producing a groundwater gradient sloping awa -from the river. U:S. Geological p g . y Geo og e Survey discharge ,data for ,the Stanislau5 River (Appendix B) : indicate that the river discharge rate was �. approximately four.times higher during the May sampling. event than during the February event. F4.2 Groundwater.Sample Analytical Result§ Neither' TPHg-nor BTEX compounds were detected in concentrations exceeding method detection limits in arty of the collected samples. TPHd was detected in' samples from .all-three wells in .concentrations ranging. from 100 to 530 ppb. A' E summary -of groundwater .elevations and analycal results is resented ori'Table ;1. Hydrocarbon concentrations are`displayed.graphically on Figure 4. A copy of the laboratory.reports,and chain-of-custody forms are attached as Appendix C. D-104 2Q95 2 Judy 14,1995 r