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Mr.Michael Oliphant—CEMC Well Vault Replacement Work Plan August 1,2011 Alden Park Page 2 of 3 • Obtain well-head repair permits from San Joaquin County Environmental Health Department. • Obtain an encroachment permit from the City of Tracy. • Retain Cornerstone Environmental Contractors, Inc. (Cornerstone)to perform casing repair and well vault replacements. Cornerstone is a California State Licensed Contractor#722253. • Perform maintenance on well vaults MW-20 and MW-21. Maintenance will include removal of existing bolts, re-dieing threads, installation of new 5/8-inch bolts with rubber washers, cleaning the lid O-ring seat, and installing a new O-ring. Note that vegetable oil will be used as a lubricant. • Remove and replace well vaults for 10 4-inch-diameter monitoring wells, located within the park area(Figure 1) and surrounding greenbelts, with 12-inch-diameter Emco-Wheaton monitoring well vaults (model number A0721-101; see Attachment B for vault specifications). Cornerstone will remove the concrete aprons (if present) and well vaults using a combination of digging and demolition. The new boxes will be installed at grade with a 4-inch concrete apron around each well box. • Remove and replace well vaults for four 4-inch-diameter monitoring well vaults, located on sidewalks (Figure 1) along with the adjoining sidewalk panel,with Emco-Wheaton monitoring well vaults (model number A0721-101; Attachment B). A saw cutting tool will be utilized to remove the well vaults and sidewalk panels. Once saw cutting is complete, the concrete and well vaults will also be removed using a combination of digging and demolition. The new boxes will be installed at grade along with a new concrete panel around each well box. • Repair the damaged MW-6 well casing by excavating approximately 2 feet below ground surface to expose the casing, cutting and installing a new coupling and pipe extension, and encapsulating the repaired coupling in concrete. A new Emco-Wheaton monitoring well vault will then be installed using the procedures described above. • Re-survey the MW-6 well top-of-casing following rehabilitation activities. • Place investigation-derived waste in United States Department of Transportation- approved containers pending disposal. • Document well vault replacement activities in the annual 2012 groundwater monitoring report. SCHEDULE Field work will commence on execution of necessary permitting and is anticipated to last 1 week.