ARCHIVED REPORTS XR0000251 - Laserfiche WebLink

Home Browse Search

' California Department of Transportation June 9, 1999 Stockton Maintenance Station, Stockton, California Project No 103872-02 2. INTRODUCTION AND SCOPE OF SERVICES ' This report summarizes the results of the First Quarter 1999 groundwater monitoring activities I conducted on March 31, April 1 and 2, 1999 at the Stockton Maintenance Station, located in ' Stockton, California (Figure 1) The work conducted by Ninyo & Moore was in accordance with Task Order No 10-911175-NB and Caltrans Contract No 43AO012 Our scope of services in- clude 1) attendance of a prework site visit, 2) preparation of a site safety plan, 3) measurement of the depth to static groundwater at selected wells, 4) purging of a minimum of three well vol- umes to labeled reconditioned 55-gallon drums, 5) collection and chemical analysis of groundwater samples, and 6) preparation of this report documenting our field activities and ' findings 3. SINCE BACKGROUND According to a report entitled, Draft Report, Fourth Quarter 1998 Groundwater Monitoring Re- port by Professional Service Industries (PSI), dated February 19, 1999, one 5,000-gallon diesel ' underground storage tank (UST) and one 10,000-gallon unleaded gasoline UST, two pump is- lands and associated product piping were removed from the site in 1989 Subsequent to the ' removal, soil samples were collected to determine the extent of soil contamination Analytical results of soil samples collected indicated maximum concentrations of total petroleum hydrocar- bons as gasoline (TPH-g) to be 2,000 milligrams per kilogram (mg/kg) and total petroleum hydrocarbons as diesel (TPH-d) to be 58 milligrams per kilogram (mg/kg) Twelve groundwater monitoring wells and two vapor extraction wells have been installed at the site The approximate locations of the monitoring and vapor extraction wells are shown in Figure 2 Quarterly groundwater monitoring has been conducted at the site on wells MWA, MW-2, and 1 MW-3 since April 1992 Wells MW-4 through MW-8 and VW-I have been monitored since May 1995 Wells MW-9 through MW-12 and VW-2 have been monitored since February 1996 His- torically, high concentrations of TPH-g, TPH-d, and benzene, toluene, ethylbenzene, and total xylenes (BTEX) have been detected in the on-site monitoring wells