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t ` <br /> P <br /> C L E A kWATE R <br /> G a o o r <br /> En orron mtnlal StrdiCt3 <br /> GROUNDWATER MONITORING AND SAMPLING RESULTS <br /> Depth to groundwater 8 06 (MW-1) to 10 95 (MW-8) feet below top of casing <br /> Flow direction Southeast at 0 018 ft/ft <br /> TPI-Ig concentration range < 50 Rg/L (MW-2, MW-4) to 1,800 Rg/L (MW-5B) <br /> Benzene concentration range <0 50 gg/L (MW-2, MW4, MW-7) to 330 Rg/L (MW-5B) <br /> MTBE concentration range <5 0 Rg/L (MW-2, MW-3, MW4) to 23 Rg/L (MW-5B) <br /> Remarks MTBE was detected by EPA 8020 in the groundwater sample collected from <br /> monitoring wells this quarter Previously MTBE has been confirmed as "non-detectable" by EPA <br /> 8260B in all monitoring wells sampled at the site Monitoring well MW-2 and MW-4 were omitted <br /> from the Groundwater Elevation Contour Map <br /> PROJECT STATUS & RECOMMENDATIONS <br /> The contaminant plume is currently delineated and being monitored on a quarterly basis <br /> Based on review of historical analytical data, Clearwater recommends to study subsurface <br /> conditions for natural attenuation by biodegradation and the acceptability oxygen releasing <br /> compounds to enhance this process To review this possiblity, Clearwater recommends collecting <br />• additional groundwater samples from monitoring wells MW-2, MW-5B and MW-8, and have them <br /> analyzed for the following <br /> • Dissolved oxygen (infield meter, all wells) <br /> • Biological oxygen demand by Standard Method 5210 <br /> • Chemical oxygen demand by Standard Method 5220 <br /> • Total organic carbon by Standard Method 5310 <br /> • Bio available Nitrogen by Standard Method 4500NH3 <br /> is Bio available phosphorus by Standard Method 4500P <br /> • Total heterotrophs count(Cyto-Culture, Inc Method) <br /> is Total hydrocarbon-degrading bacteria count (Cyto-Culture, Inc Method) <br /> Clearwater recommends collecting these samples during the second quarter, when groundwater <br /> levels are at their highest <br /> ATTACHMENTS <br /> • Site Vicinity Map(Figure 1) <br /> • Site Plan (Figure 2) <br /> • Groundwater Contour Map - 2/13/01 (Figure 3) <br /> • Hydrocarbon Distribution Map - 2/13/01 (Figure 4) <br /> • Groundwater Elevations and Analytical Results (Table 1) <br /> • Clearwater Gauging Data/Purge Calculations and Well Purging Data <br /> • Certified Laboratory Reports and Chain-of-Custody Form <br />. • Clearwater Groundwater Monitoring and Sampling Protocols <br /> CGI-ZB178C-1QT01 3 February 23, 2001 <br />