Laserfiche WebLink
PUBLrC HEALTH SERVICES <br /> SAN JOAQUIN COUNTY <br /> JOGI KHANNA M.D.,M.P.H. <br /> Health Officer <br /> C'••. gip' <br /> P.O.Box 2009 • (1601 East Hazelton Avenue) •Stockton, California 95201 <br /> (209) 468-3400 <br /> APR 16 1991 -KYLE CHRISTIE cnQ <br /> ARCO PRODUCTS CO <br /> P O BOX 5811 <br /> SAN MATEO CA 94403 <br /> RE: ARCO Station IN REPLY REFER TO SITE CODE: 2133 <br /> 2908 Benjamin Holt Drive <br /> Stockton, CA 95207 <br /> Third Quarter 1990 Sampling Results <br /> We have completed our review of the Third Quarter, 1990 Sampling Results submitted by Brown and <br /> Caldwell. We have the following comments regarding the contents of the report which are to be addressed <br /> in the next quarterly report submitted. <br /> The report needs to clarify what the depth of water is from the top of the well casing. The tabulated water <br /> level measurements are referenced by water level elevation below sea level. While this reference has merit <br /> for comparison purposes, it is difficult to gauge the water level within the monitoring wells. In addition to <br /> groundwater elevations, calculations used to determine the groundwater gradient should be included. <br /> Sampling results should include temperature, pH and conductivity readings to show that the water has <br /> stabilized before to sampling. Our office must be notified 48 hours prior to any sampling activities. <br /> Monitoring well E-3 was not sampled between the third quarter of 1988 and the fourth quarter of 1989. <br /> Please provide information as to why this well was not sampled during that period. <br /> Furthermore, monitoring well E-3 was not sampled the third quarter of 1990 because it had gone dry. In <br /> 1987, Ton Voster from Central Valley Regional Water Quality Control Board (CVRWQCB) questioned the <br /> integrity of the PVC well casings, because they were exposed to undiluted petroleum hydrocarbons, over a <br /> period of time, and the effects of petroleum hydrocarbons on PVC is not well understood. First quarter 1990 <br /> sample results from E-3 showed relatively high levels of benzene (9860 parts per billion(ppb)),ethylbenzene <br /> (1780 ppb), toluene (2380 ppb) and xylene (8270 ppb). The possibility should be explored that high <br /> petroleum hydrocarbon concentrations have damaged the PVC well casing. The influence of the recovery <br /> well should also be explored. <br /> Monitoring well E-6 was sampled once in 1989 and once in 1990. The results of first quarter 1990 sampling <br /> indicated that there was an increase in benzene,ethylbenzene and toluene while xylene levels had decreased <br /> slightly. An explanation for the increases in the contamination level at monitoring well E-6 should be <br /> provided. <br /> The zero lines for contamination to the west of the station have not been identified. Additional investigation <br /> to the west is required. This investigation should include sampling for TPH-d, metals (Cd, Cr, Pb, Zn and <br /> Ni) and chlorinated hydrocarbons to reflect documented contamination from the 550 gallon waste oil tank <br /> that was removed in 1987. In addition continue sampling for TPH-g and BTEX. Submit a work plan for the <br /> additional investigation by June 3, 1991. <br /> A Division of San Joaquin County Health Care Services 1(> <br />