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Whetstone' <br />Associates <br />9. ATTACHMENTS <br />Attachment 1. Monitoring Well Drilling Locations <br />Technical Memorandum <br />Water levels may take a long time to stabilize after drilling and well development, so the initial <br />water levels measured in the wells may not be representative of the system. <br />Low -flow, passive sampling, or micropurge® methods may be required to prevent overpumping of <br />the wells. It is believed that overpumping of bedrock well MW 11 while purging the traditional three <br />well volumes may have contributed to the intrusion of bentonite into the well screen. Passive (or <br />"no- purge ") groundwater sampling methods have gained acceptance with technical personnel and <br />regulatory agencies over time. Five passive sampling methods, including sampling devices such as <br />the GORETM Module (formerly referred to as "Gore- Sorber "), HydrasleeveTM, regenerated- cellulose <br />dialysis membrane sampler, rigid, porous polyethylene sampler, and Snap SamplerTM are documented <br />by ITRC (2006). <br />Low -flow sampling is preferred for bedrock wells capable of producing at least 0.1 L /minute flow <br />without drawdown. If bedrock wells meet this minimum flow requirement, dedicated sample pumps <br />would be set within the screened zone and the wells would be sampled using standard environmental <br />methods of low -flow sampling (EPA, 2000; ASTM, 2003). <br />8. REFERENCES <br />ASTM, 2003. D 6771 Standard Practice for Low -Flow Purging and Sampling for Wells and <br />Devices Used for Ground Water Quality Investigations. <br />Interstate Technology & Regulatory Council (ITRC), 2006. Evaluating, Optimizing, or Ending <br />Post - Closure Care at Municipal Solid Waste Landfills Based on Site - Specific Data <br />Evaluations, Technical /Regulatory Guideline prepared by the Interstate Technology & <br />Regulatory Council Alternative Landfill Technologies Team, September, 2006. 58 pp plus <br />appendices. <br />EPA, 2000. Environmental Technology Verification Report: Groundwater Sampling Technologies, <br />QED Environmental Systems, Inc. Well Wizard® Dedicated Sampling System. EPA -VS- <br />SCM-41, August 2000. <br />4109C.120309 10 <br />