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Post-it• Fax Note 7671 <br />MEMO T( Iraxa(770-= <br />Date: Mav 11, 2000 <br />//~~ ~ <br />Specialist: Allen Sorenson Signed: G" "~~~ <br />SubjecUOperator/Operation/File No. Ground Water Samyling. AmerAlia, Inc.. <br />Rock School Lease. File No. M-99-051 <br />Type of Interaction: Meeting Phone Other <br />Person(s) contacted and affiliation: Paul Daggett. BLM-Meeker <br />Summary and Resolution of Interaction: <br />This memo documents discussion of concerns the BLM has with air-lift ground water sampling at the <br />Rock School Lease. BLM FAXed me the completion diagrams for the monitoring wells. One of the <br />concerns is that the end of the air tube is between 900 and 1200 feet above the bottom of the dissolution <br />swface wells and the B-groove well. This results in a step-wise procedure during well purging. If the <br />wells recover relatively quickly during purging, it is likely that the removal of three casing volumes <br />through step-wise air lift pwging will result in fresh formation water filling the well bore, and a <br />representative sample may then be collected. If the well recovers slowly, there may be mixing of <br />stagnant well bore water and fresh formation water during step-wise pwging due to the fact that the <br />entire well bore cannot be evacuated at one time. The mixture including stagnant water would not yield <br />a representative sample. For low yielding monitoring wells it may be necessary to purge more than three <br />casing volumes. The sampler should monitor pH, temperature, and conductivity and consider the well to <br />be flushed when these parameters no longer change. Even if the indicator parameters stabilize, the <br />minimum purge volume should by three casing volumes. <br />BLM is further concerned that air-lift sampling will result in non-representative samples for BTEX analysis. <br />This concern is justified. The air-lift method is not appropriate for collection of samples that will be tested <br />for any volatile organics (ASTM D 4448). <br />