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Ms.Margaret Lagorio Page 3 San Joaquin County Environmental Health Department January 13, 2004 UNDERGROUND UTILITY LOCATION All proposed drilling locations will be marked, and Underground Service Alert(USA)will be notified a minimum of 48 hours prior to commencement of any field activities for each phase of work. A private utility locator will also be contracted to survey proposed boring locations for private utilities prior to commencement of field activities. In addition,the first 5 feet bgs in each boring will be cleared with an air or water knife to a diameter of 8.25 inches. PHASE I - SOIL AND GROUNDWATER GRAB SAMPLING URS proposes to drill four vertical soil borings at the locations shown on Figure 2. The boring locations were selected to laterally define 1,2-DCA in the groundwater at the site. To better define the lateral extent of the contaminant plume between the city municipal well and the site,the location of the proposed soil boring between the plume and city well may be adjusted in the field. The borings will be drilled using a hollow stem auger(HSA) equipped drill rig with 8.25-inch outside- diameter(OD)augers. The total depth of each boring will be approximately 75 feet bgs. Groundwater at the site is expected between approximately 56 to 65 feet bgs. "s-t 7 d ', a-14 p'sr�blr ki s vei l-,t4 e c%d,,� ed X4— /1" e I.CT "➢ A URS geologist will collect samples of the subsurface soils at 10-foot intervals beginning at 10 feet bgs. 75'J,y 'J5a 37+1 A portion of each sample will be used for headspace screening with a photoionization detector(PID)and y for lithologic logging. A portion of each sample will also be retained and be submitted to the laboratory ' for possible analysis. The borings will be logged using the samples collected from 10-foot intervals (and from drill cuttings)by the URS geologist according to the Unified Soil Classification System. Each soil sample retained for possible chemical analysis will be collected in brass liners,capped with Teflon®tape and plastic end caps,labeled, and placed in a cooler on ice for delivery to Sequoia Analytical Laboratory(Sequoia)in Petaluma,California under chain of custody. Soil samples showing visible staining or elevated PID readings will be analyzed by the laboratory. If staining or elevated PID readings are not encountered the sample collected in the capillary fringe just above first water will be analyzed. At least one soil sample from each boring will be analyzed for gasoline range organics(GRO) by EPA Method 8015B (preparation EPA Method 5030),benzene,ethylbenzene,toluene,xylene, (BTEX),methyl tert-butyl ether(MtBE),tert butyl alchohol(TBA),di-isopropyl ether(DIPE),ethyl tert- butyl ether(ETBE),tert-amyl methyl ether(TAME), 1,2-DCA,and ethylene dibromide(EDB),by EPA Method 8260B (preparation EPA Method 5030). Groundwater Grab Sampling Groundwater samples will be collected from first groundwater encountered in each boring using a new disposable bailer for each boring. Groundwater samples will be analyzed for GRO by EPA Method 8015B (preparation EPA Method 5030),BTEX,fuel oxygenates (MtBE,TBA,TAME,DIPE,EtBE),and KAWprocessV5 BP ARCO\00760\2004 Assessment\760 GW Workplan 04.doc