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--state of California <br />Memorandum <br />To :Wade Cornwell, F.E., <br />Senior Engineer <br />From : Richard D. McJunkin <br />Certified Engineerirx Ge gist (#1280) <br />Department of Health Services <br />Date February 9, 1987 <br />Subject : Forward Work <br />Plan Dated January <br />30, 1986 by Beta <br />Associates. <br />Department of Health Services (DHS) comments for the Forward Inc. <br />work plan dated January 30, 1986 are provided. The report is <br />acceptable to DHS and represents a detailed Phase 1 approach for <br />satisfactory subsurface characterization and ground water <br />monitoring at the Forward, Inc. landfill. DHS comments are <br />referenced to specific sections of the work plan by page number. <br />These comments should be incorporated to become a part of the work <br />plan by Forward, Inc. <br />Monitoring Well Abandonment: <br />Page 1. Wells to be abandoned should not be perforated throughout <br />the entire length of casing. Rather, sections of casing should <br />ONLY be perforated where the casing intersects impermeable zones <br />(i.e. clay and silt horizons). Abandonment will then effectively <br />grout (seal) these horizons and preclude potential cross <br />contamination. Perforating the entire casing will effectively <br />allow grout to take the path of least resistance and migrate into <br />permeable horizons; this will not provide for sealing impermeable <br />strata. <br />Page 1. Forward, Inc. did not reference specific types of grout <br />or mixing ratios in the work plan. For this reason, DHS <br />recommends that grout be mixed to Halliburton cementing <br />specifications. If type A -B cement is used, Halliburton <br />recommends that quantities of ingredients are 5.2 to 6.0 gallons <br />of water per sack (94 pounds) of cement. If bentonite is used in <br />the mix, an additional 0.65 gallon of water per pound of bentonite <br />needs to be added to the mix. In addition, using bentonite in <br />cement requires that the dry ingredients are thoroughly blended <br />and then added to water using a "jet or venturi" mixer. However, <br />if Forward, Inc. desires to use another commercially produced <br />cement -additive bentonite (e.g. Volclay, etc.), it would be <br />acceptable to DHS providing manufacturer recommended ratios for <br />mixing the ingredients are followed. <br />New Monitoring Wells -Phase 1. <br />Page 1. The purpose of instil' ng 25 foot -long well screens is to <br />always intersect the water + with the well screen regardless <br />