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Work Plan for the Former Two 20,000-Gallon USTs Location at Stockton AASF California Army National Guard • Notify Underground Service Alert(USA)a minimum of 48 hours prior to commencement of field activities. The USA phone number is 1-800-227-2600. • Coordinate inspection of decommissioning activities with the San Joaquin County PHS-EHD. • Calculate the approximate volume of grout needed to fill each borehole from the bottom of each well to the ground surface,and mix 10.3 sack slurry mixture(188 pounds sand per 94-pound sack cement[2 parts sand to 1 part cement by weight] and 7 gallons of water)after the boreholes are drilled. • Place tremie pipe at the bottom of the over-drilled borehole and pump the slurry into the borehole through the tremie pipe,bringing the grout slurry to ground surface for each former well. • Record the volume of slurry placed in each well. 6.15 Gregg Drilling,Inc.,has been selected as the subcontractor for this field effort. The contact at Gregg Drilling for this effort is Chris Pruner(telephone number 925-313-5800). 6.16 This decommissioning effort will be scheduled upon completion of the above-described investigation events if warranted,and approved by RWQCB. 6.17 Resuming Quarterly Sampling.The three existing MWs(MW-1 through MW-3)may be redeveloped if it is determined that groundwater beneath the site has been inadequately characterized and site closure cannot be granted until further site characterization is completed. If groundwater sampling indicates that impacts are present,then the items described in the following subsections may be required,to continue the process for site closure. 6.18 This section of the WP summarizes the activities necessary to redevelop and sample the three existing MWs that were installed 15 years ago.All field activities will be conducted in accordance with San Joaquin County regulations and coordinated with the San Joaquin PHD-EHD. 6.19 Redevelopment.The redevelopment procedure will be swabbing and bailing followed by pumping.At a minimum,the following procedures will be performed: • A bailer or similar device will be used to remove sand or fine material from the bottom of the well—the well will be bailed until less than approximately 1 teaspoon of sand or fine material is collected in the bailer. • The well will then be swabbed with a valved surge block appropriately sized for the inside diameter of the well.The swabbing will begin just below the static water line in the casing,with a gentle action,until free movement of water through the screen is assured,at which time surging can progress more actively. • The surge block will then be lowered gradually into the screened area(s). The amount of material drawn into the well will be frequently measured and will be removed by frequent bailing with a sand bailer. • Repeat steps one through three at least three times or until less than 1 teaspoon of sand of fine material is collected in the bailer. KAWprocess\0025 MA ARNG\Stockton AASF WP\FINAL\WP text.doc 10 June 2007