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URS <br /> ' Ms.Kathy Amani Page 2 of 3 <br /> Regional Water Quality Control Board-Central Valley Region <br /> ' May 6, 2011 <br /> PROJECT HEALTH AND SAFETY <br /> URS prepared a site-specific HASP and made it available on site during field activities.All field <br /> personnel reviewed the HASP before the start of field activities. <br /> UTILITY CLEARANCE <br /> ' Well locations were clearly marked and Underground Service Alert was notified at least 48 hours before <br /> field activities begin. <br /> ' WELL ABANDONMENT (MW-23-SP) <br /> Woodward Drilling of Rio Vista, California, decommissioned MW-23-SP under the direction of a URS <br /> geologist on April 19, 2011. The well location is presented on Figure 1. <br /> MW-23-SP was abandoned by over-drilling to its total depth of 21 feet bgs with 10-inch OD hollow- <br /> stem augers,then backfilled using tremie pipe with Portland cement grout containing less than 5% <br /> ' bentonite powder to the surface. Appendix A presents the well construction diagram. <br /> MONITORING WELL INSTALLATION (MW-23R) <br /> URS installed one groundwater monitoring well(MW-23R-SP) on April 19,2011,to replace the <br /> abandoned well MW-23-SP. This replacement well was installed approximately 10 feet from the original <br /> well location. <br /> The monitoring well was drilled using a 8.25-inch OD hollow-stem auger rig and was constructed using <br /> 2-inch-diameter, flush-threaded, schedule 40 polyvinyl chloride well casing(Attachment B).Fifteen feet <br /> ' of 0.010-inch,machine-slotted well screen was set from approximately 6 feet to 21 feet bgs.A Monterey <br /> #2/12 silica sand filter pack was installed from the bottom of the boring to I foot above the top of the <br /> well screen. Eight inches of#0/30 transition sand was installed above the filter pack of each well. A <br /> 1-foot bentonite seal was placed above each sand pack, and neat cement was used to seal the remaining <br /> annular space to the surface. The well was completed with a 3-foot stove-pipe monument and traffic <br /> bollards. Soil cuttings were logged by a URS geologist in accordance with the Unified Soil <br /> ' Classification System. Except for one for waste characterization,no soil samples were collected for <br /> laboratory analysis. <br /> ' WELL DEVELOPMENT <br /> MW-23R-SP was developed using a 1.5-inch OD steel bailer by continuously surging and bailing over <br /> the entire screened interval for approximately 40 minutes. Well development was completed by purging <br /> ' a maximum of 10 well casing volumes or until stabilization of water parameters (i.e. conductivity and <br /> H\Wp ms\RESMDVI-Bum Pit=IV W-23RSP Well DesemOon and Reinstallation Rpt doc <br />