ARCHIVED REPORTS XR0011041 - Laserfiche WebLink

Home Browse Search

Wm. J. Hunter & Associates 2220 Loma Vista Dr Registered Geologists sC-��N"E :TA ) �'T#i Sacramento, CA 95825 Petroleum & Mineral Appraisers i r �i (916) 972-7941 j: r `#" FAX (9 16) 972-1683 51 C' i September 10, 1996 r Steven Sasson, Sr REH5 San Joaquin County Health Department Environmental Health Division P O Box 388 Stockton, CA 95201-0388 Ref Twelveth Quarterly Groundwater Monitoring Reports for 814 E Charter Way, Stockton, Site Code 1061 We am enclosing a copy of the field report, laboratory analyses, and maps showing groundwater gradients and lines of equal concen- trations of benzene, toluene, ethylbenzene, xylene, & TPHg The field work was performed on July 1, 1996 by Del-Tech Geotechnical Support Services as directed by our office . The attached EXHIBIT A, shows the contours on the top of the water table on July 1, 1996 ; the gradient is to the east/north- east at about . 00371 /ft . , slightly steeper than the last event EXHIBIT B summarizes the thirteen (13) hydraulic gradients measured to date on the property. Except for the July 1995 sampling, all of the data indicate a rather stable gradient to the east/northeast The reason for the reversal .in the potentio- metrac surface in July, 1995 cannot be explained based on the data available at the time this report was prepared We have not received any data concerning activities at the Darpetro property since January, 1995 EXHIBIT C shows the approximate contours based on lines of equal concentration of benzene from the July 1, 1996 sampling event MW-1 continues to below detection limits ; the only event that revealed any benzene was in February, 1994 Levels in MW-2 increased from 177 ug/L in 2/96 to 532 ug/L in July, the latest sampling is the highest measured in that well since monitoring began MW-3 continues to show relatively low levels; no discernable trend or pattern is apparent PLATES D, E, & F show lines of equal concentration of toluene, ethylbenzene, & xylene based on the 8/96 sampling All of the maps show an increase in levels of those components to the east/ northeast, which is the predominant direction of ground water flow PLATE G shows lines of equal concentration of THPG from the July, 1996 sampling Levels in MW--1 decreased from 275 ug/L in February, 1996 to 118 ug/L in July. However, levels in MW--2 increased from 645 ug/L in 2/96 to 1520 ug/L in July MW-3 1