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t <br /> CLEARWATER <br /> G R O EJ P I N C <br /> 1 <br /> 3.0 FIELD ACTIVITIES <br /> tAll work was performed in accordance with Clearwater Field Procedures (previously <br /> submitted) and under the directives and guidelines established by the PHS/EHD and <br /> ' the Regional Water Quality Control Board The monitoring wells were gauged and <br /> sampled on June 30, 1995 Prior to sampling, all wells were purged of a nur mum <br /> ' of three saturated well volumes Well purging information is presented in <br /> Appendix A <br /> Groundwater samples were collected from the monitoring wells using dedicated <br /> polyethylene bailers The appropriate well numbers were written on sample labels <br /> and documented on a chain-of-custody form The samples were then placed in a <br /> ' cooler for transport to American Environmental Network (AEN), a DHS-certified <br /> laboratory located in Pleasant Hill, California All groundwater samples were <br /> analyzed for total petroleum hydrocarbons as gasoline (TPHg) by EPA Method 8015 <br /> ' (5030/GCFID), and for benzene, toluene, ethylbenzene and total xylenes (BTEX) by <br /> EPA Method 8020 <br /> 4 0 RESULTS AND CONCLUSIONS <br /> 4.1 Water Level Monitoring Data <br /> ' On June 30, 1995, the depths to ground water in the five monitoring wells ranged <br /> from 2229 to 2361 feet below grade. Groundwater flow was 'estimated to be , <br /> ' northwesterly'at an approximate gradient of 1.7% (0 017 feet/foot) across most of the <br /> site In the northwestern portion of the site, adjacent to the former tank excavation, <br /> the groundwater flow,was to the northwest at an approximate gradient of 0 4% <br /> 1 I 1 ' <br /> ' Plotted on the Groundwater Contour Map (Figure 3) this change in gradient appears <br /> as a slight flattening of the water table west of the former USTs The same <br /> configuration of the water table was apparent during previous gauging events <br /> Because the site is unpaved, it is possible that groundwater recharge through the <br /> vadose zone into the porous excavation backfill material is affecting the local <br /> ' groundwater gradient ! } <br /> r <br /> 4.2 ,Groundwater Sample Analytical Results h <br /> + TPHg and ,benz'ene were detected in',samples collected'from all, monitoring ,wells! <br /> <i i except MW-3 and MW-4' The highest' defected concentration's'of TPHg and benzene <br /> , "1 ! ,,i 1 ! I '1 1 , 1, ! 1, l L'I i l' I , e <br /> were, 47,000 parts, per billion)1'(p pb) sand!' 310 Ppb,,, respectively', in';MW-2 <br /> !! , Concentrations of TPHg and-benzene4 `were,12,000 ppbi'land�,110 ppb; respectively, in <br /> downgradient well MW-5 A,summary of groundwater elevations,and analytical i <br /> E <br /> D2101 2Qpp95 2 August 3,1.995 <br />