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the last soundings The hydraulic gradient of the water table has changed slightly The original direction of flow gradient was South 75 degrees East,where as on 10/19/98 it was almost due East The 4/1/99 gradient is down slope North 80 degrees East with S=0 002 The 9/09/99 soundings show the down slope gradient to be North 79 degrees East with S-0 0016 Soundings for 12/21/99 indicate the down slope gradient was at North 83 degrees East with S=0 0023 For the event of 3/31/2000 the soundings resulted in a gradient with a bearing of South 88 degrees East with S=0 002 For this event the groundwater gradient is North 50 degrees East Pump rates for purging continue to be between 1 0 gpm and 2 0 gpm WATER SAMPLE ANALYSIS FINDINGS In general, monitoring well samples taken on 8/31/2000 were very similar to previous samples Analysis by EPA Test Method 8260 was not repeated,as the 4/l/99 samples were non-detect MW- 3S is the only monitoring well with BTIX compounds determined by EPA method 8021B This is the same BTEX result as the other sample events of the same fall time period For this event,compound 1,2-Dichloroethane is only present in low concentrations in wells MW-1 and MW-2S (see recap of data attached) CONCLUSIONS BETX compounds for this event in the MW#3S remain near the same concentrations as samples from other late summer or fall events This monitoring well is receiving the highest impact of all the wells due to TANK#1 (the Stoddard's Solvent tank), which is up gradient and Northwest of MW#3S Halocarbon compounds are present in low concentrations in all but MW#4S and MW#4D In general, Halocarbon concentrations in all water samples are the same as the last sampling period Only MW-3S exceeds National Primary Drinking Water Regulation for 1,2- Dichlorethane at 5 8 ug/L The present 5 8 ug/L is considerably lower than 28 ug/1 found in the sample extracted on 6/11/98 RECOMMENDATIONS The author requests that all monitoring wells continue to be sampled in semiannual events to conserve financial resources In response to your verbal request for the installation of a new monitoring well on the East side of California Street,this author will develop a work plan to install the new monitoring well in the city owned right of way Please contact this office at 209/368-9381 if any questions arise from this report Respectfully submitted, �,FF6S10 RIF�,ye Foothi n eeri c No 1875 Ervin Ri enburg, ' cc Mrs Helen Higgins, 5815 Mor ace #16, Stockton CA 95219 2