ARCHIVED REPORTS XR0008192 - Laserfiche WebLink

Home Browse Search

R604 -UPDATE 20 7-16--1993 INTRODUCTION This report includes the results of events occurring at this site since the 19th Update Status Report, from May 14, to July 7, 1993 During this time San Joaquin County Health had completed a review of the Update Status Reports through #16, dated February 25, 1993 and Results of Sampling of the Vapor Extraction System through the April 30, 1993 report, see Appendix A. SAN cTOAQUIN COUNTY REVIEW ANSWERS (COMMENTS) Groundwater Groundwater samples collected from monitoring wells, MWI, MW4, MW5 and MW7 on December 7, 1992 Monitoring wells MW2, MW3 and MW6 did not contain enough water to sample. Samples collected from MWI and MW4 were not analyzed for TPG-gasoline. Only the sample collected from MW5 contained detectable petroleum hydrocarbon contamination, 160 ppb TPH-gasoline, 1 . 2 ppb ethylbenzene, and 35 ppb xylene. As of May 21, 1993 PHS/EHD has not received the sample results from the samples obtained on March 30, 1993 PHS/EHD does not recommend the destruction of monitoring wells at this time. COMMENTS : Since the December 7, 1992 sampling round the site has been undergoing recharge and samples have been collected from all wells during the March 30 and June 16, 1993 sample rounds Samples collected from MW1 and MW4 during the December 7, 1992 sampling round were analyzed for TPH--gasoline, both were below detection limits of <0 05 mg/L. SOIL VAPOR EXTRACTION The results indicated that hydrocarbons continue to be removed from the soil at a rate of 8. 65 lbs per day PHS/EHD recommends the continued operation of the vapor extraction system with consideration given to pulsing the system to allow equilibration of soil vapor concentrations CONTENTS: The pounds per day rate of hydrocarbon removal is greatly influenced by flow rate The concentration of the vapor stream is more apparent to the results of the vapor extraction system. Figures 7A, 7B, 7C, 7D, 7E and 7F are charts- of the TPH- gasoline range concentrations as compared to hours operational for the influent, VSB3, VSB5, MW5, VSB9 and VSB11 respectively. These charts show a steady decline in concentration with time and all concentrations as of June 18, 1993 , are less than 1 0 mg/L vapor. These newly installed vapor extraction wells (July, 1992) , show a dramatic decline in the concentrations since originally started on the vapor extraction system The total influent concentrations, Figure 7A at 2700 hours of operation (addition of VSB3 , VSB5, VSB9 and VSB11 into extraction system) 8 53 mg/L to June 18, 1993, 10562 hours of operation = 0 . 82 mg/L vapor. This is a 90 . 4%r reduction in the vapor stream concentration. Figure 7A also shows percent CO2 being removed page 1