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Well Abandonment Work Plan -4- 16 December 1991 <br /> DDRW, Tracy <br /> the ICP method or with other standard minerals, which are less <br /> expensive than the AA method. <br /> 5. Boron, calcium, iron, magnesium, silica, sodium, alkalinity, chloride, <br /> nitrate, sulfate, and total dissolved solids may be analyzed <br /> collectively, at a much lower cost than individually, as standard <br /> minerals. Analyses for other minerals, such as fluoride, manganese and <br /> phosphate may be added individually to the request for a standard <br /> minerals analysis. <br /> Page 4-5. The Plan lists the analytical methods for the soil and ground water samples <br /> in Appendix A. None of the listed analytical methods are using the EPA 500 <br /> series, which are methods for analyzing samples from drinking water wells. <br /> If Well 4 and 7 are currently used for the on--site drinking water sources, <br /> the samples from these wells should be analyzed using the 500 series. The <br /> 500 series method for VOCs has lower detection limits than the 600 series <br /> methods. <br /> Page 4-6. The Plan indicates that ground water samples will be field filtered for <br /> metals analyses. However, both filtered and non-filtered samples should be <br /> considered for analyses as this information may be needed for the site-wide <br /> Risk Assessment, if representative ground water samples can be collected. <br /> Page 4-6. The Plan indicates that radioactive logs (natural gamma and neutron) and <br /> sonic logs will be performed to help indicate lithology. This may be <br /> unnecessary if the lithology log is considered to have adequate detail and <br /> is correlatable to other well logs (i .e. , the major lithologic intervals <br /> are confirmed through correlation) . <br /> Page 4-7. The Work Plan states that a mills knife will be used to perforate the <br /> casing at regular intervals, but fails to specify the intervals. Because <br /> of the variable lithology and the depth of the Well 1 , it is important that <br /> the intervals are specified to assure an adequate abandonment. As <br /> presented in the Work Plan, it appears that insufficient consideration has <br /> been given in preparation of the abandonment plan and too much planning is <br /> being left for field decisions. This issue needs to be clarified before we <br /> can approve the Work Plan. <br /> Page 4-7. The Work Plan indicates that the Wells 1 and 2 will be abandoned by <br /> incrementally backfilling the casing with cement. However, the Plan does <br /> not provide specific information on the job design such as, what intervals <br /> the increments will be, whether packers will be used to incrementally <br /> backfill the casing and whether or not any pressure will be needed to pump <br /> the cement down-hole. The increments or stages should be based lithology <br /> and not on an arbitrary depth. In addition, little consideration is given <br /> to the design of the cement slurry. Because of the lack of information <br /> provided in the Plan, it appears that too much planning is being left for <br /> field decisions. Further information on the abandonment design and <br /> procedures needs to be submitted prier to our approval . <br /> Page 4-7. The Plan proposes mixing seven sacks of Portland Type I-II cement with one <br /> gallon of water. Based on this mix water ratio, the slurry will not be <br /> pumpable. For a slurry weight of 15.6 pounds per gallon, 5.2 gallons of <br />