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Wade Cornwell February 21, 2006 Page 2 backfill volumes should be 45 and 60 cubic feet of grout for wells KS-7 and KI-7, respectively. b. Grout used to backfill the casing and filter pack should consist of the following recipe (see Comment 1 below): 1 94-pound sack of Portland cement, 5 percent bentonite, and 4.5 to 6.5 gallons of potable water. c. Kearney-KPF should submit a letter report describing the actual decommissioning activities. The report should be supported by field documentation of the decommissioning (including actual pressures achieved and volume of grout injected). d. Kearney-KPF should comply with all applicable local, county, and State requirements during well decommissioning. BACKGROUND The Workplan proposes to decommission the wells, following San Joaquin County well standards, by removing the downhole equipment, removing the top 1.5-feet from each well, and pressure grouting with a tremie pipe until the well casing and filter pack pore space is filled with neat cement. A hole approximately one-foot larger than the diameter of the original borehole will be excavated to a depth of at least 1.5 feet below ground surface to allow for a six-inch thick grout cap over the decommissioned well. The excavated hole will be repaired according to County requirements. COMMENTS 1. The Workplan proposes to grout the wells under a pressure of 20 to 40 pounds per square inch until the casing and filter pack pore space is backfilled with the estimated well casing and filter pack grout volume. The Workplan estimates the backfill volumes to be approximately 15 and 20 cubic feet for wells KS-7 and KI-7, respectively. Because it is frequently difficult to achieve and/or maintain the grout pressure cited in the Workplan when decommissioning monitoring wells, GSU recommends that DTSC specify a minimum volume of grout to be tremied into the wells during decommissioning. A common industry practice is to inject a grout volume that is three times the estimated casing and filter pack pore volume. 2. The Workplan does not provide the grout recipe. According to a February 7, 2006 electronic mail message from Dudek & Associates, the grout recipe will consist of one sack of Portland cement (94 pounds), 5 percent volclay grout, and 4.5 to 6.5 gallons of clean water. 3. The Workplan does not discuss how the decommissioning activities will be documented and reported to DTSC. 4. If possible, a DTSC representative should be present to observe the well decommissioning activities.