SITE INFORMATION AND CORRESPONDENCE FILE 2

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W ENVIRONMENTAL HEALTH DEPARTMENT SAN JOAQUIN COUNTY Unit Supervisors Donna K. Heran, R.EILS. 3.04 East Weber Avenue, Third Floor Carl Bergman, R.E.H.S. < Director Mike Huggins, R.E.H.S., R.D.I. Al Olsen, R.E.H.S. Stockton , California 95202-2708 � ..,_. Douglas W. Wilson, R.E.H.S. o` .rP ProgronManager Telephone: (209) 468-3420 Margaret Lagorio, R.E.H.S. 9Cj - Laurie A. Cotulla, R.E.H.S: Fax: (209) 464-0138 Robert McClellon, R.E.H.S. Progrmn Manager Mark Barcellos, R.E.H.S. APR 2 7 2004 RODGER LISTON DARPETRO INC USA SERVICE STATION 3450 EL CAMINO CERES CA 95307 RE : DARPETRO, INC Site Code: 1060 749 E CHARTER WAY STOCKTON, CA 95202 As was discussed with you on 23 April 2004, San Joaquin County Environmental Health Department's (EHD ) letter of 16 April 2004 omitted mention of the technique utilized to obtain depth to water ( DTW) measurements observed during the 14 April 2004 monitoring event at the above-noted site, necessitating this additional letter. During the 14 April 2004 monitoring event, EHD noted that there was no consistent method utilized to obtain DTW measurements. Sometimes the field technician measured the DTW from the east side of the casing , sometimes from the west, often seemingly from whatever convenient point the technician could reach from where he approached the well . The tops of the well casings often had several hundredths of a foot relief of elevation across the top due to how the casing sits in the original boring or how the casing was cut, which is usually done by hand after the well is set. Without a procedure in place to ensure accurate collection of DTW data, the resulting ground water elevations may be in error — and the inferred ground water flow directions would be in doubt. To address these problems , a point on the top of the well casing should be consistently utilized to take the DTW measurements . This point may be a mark, a notch , the lowest point on the top of the casing , the north side (if apparent), or some other consistently chosen point. The well elevation must be surveyed to that point. It would be a good practice to permanently mark the surveyed point at the time of the survey. Your consultant should review the survey results currently used and ensure that the points on the well casings surveyed are known , otherwise the casing elevations may need to be resurveyed . The techniques utilized to obtain the DTW measurements must be part of your written ground water monitoring plan . Please have your consultant address this issue , as well as the other issues noted in the EHD letter of 16 April 2004 , in the ground water monitoring plan due in this office no later than 21 June 2004. It is EHD's intention to have this monitoring plan in effect before the next quarterly ground water monitoring event.