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August 6, 2014 Page 3 of 10 Reference: Well Destruction Work Plan ARCO No. 2130 Prior to pressure-grouting activities, the well casing will be inspected for obstructions; if obstructions are found, they will be removed prior to grouting . These four wells (MW-7, MW-14, MW- 19, and MW-21 ) will be destroyed by pressure grouting, which consists of filling the well and filter pack with neat cement grout through a tremie pipe from total depth to top of well casing . Grout will be allowed to settle and then topped off before pressure is applied to the wells at 25 pounds per square inch for ten minutes. Following pressure grouting, the top 3 feet will be cleared with an airkhife and vacuum truck, creating a hole at least one foot wider than the auger originally used to install the well. In tic addition, the well box, concrete apron, and well casing from 2.5 feet below around surface to , +7`tic grade will be removed . After the well box, concrete apron, and length of well casing are 01p removed, grout sealant will be placed to spill out of the top of the well casing to form a (wire^t, 4- mushroom cap seal to 2 feet b . The remaining void will be filled with native soil or engineered �"r� fill and the surface will be completed to match the existing grade. A profile diagram of the top Af three feet of these wells is included in Attachment C . t /4*w ^4$&4� g/ L3/ I I Wells Scheduled for Over-drill but requesting Pressure Grout with County Variance • Fifteen additional wells (MW-5, MW-6, MW-13, MW- 16, MW-20, AS-2, AS-3, VW-3, VW-6, P6 ak VW-8 through VW- 12, and MS-3A /B) will require a variance from the SJCEHD to be '✓ / t k� l pressure grouted with a limitedmushroom cap within the borehole diameter due to AN+v , fy srt of this ork Pl n These fifteen wells would re*y� °� ya typically require over-drilling as part of the well abandonment process. However, during �drtennt . the hazard analysis of each well abandonment method and evaluation to site hazards, Stantec has determined that a county variance is a safer approach and is discussed in detail below. Details of utilities with associated proximities and depths to these nearby wells share illustrated on Figure 3, Wells AS-2 AS-3 VW-3 VW- &lS-AB are located in the current UST backfill or immediately adjacent . Over-drillin_ a these i��^ns runs the risks countering the UST S direr^fly and ootenticilv ca ieinq a new product release or encountering pea gravel that would make their removal challenging and would require a much larger advancement of an outer casing . AS-2 and AS-3 have 12 inch diameter PVC well casings as well . The four wells (AS-2, AS-3, VW-6 a0d YW- I1 ) located io the tank pit have a very large vault/we oxaround them and it appears that it will be oossiblelo airvac the pea gravel out of this area and pressure grout the well . Wells MW-5, MW- 13, MW-20, VW-8, and VW- 10 are located between 7-28 inches from operating product lines . MW-5 is 20 inches from the underground product lines, MW- 13 is 7 inches from the underground product line, MW-20 is 28 inches from underground product lines and 5 feet (ft) from underground water utility main for the station, VW-8 is 19 inches from the underground product lines, and VW- 10 is 28 inches from the underground product lines. Over-drilling these locations runs the risks of encountering the product lines directly and potentially causing a new product release. Design with community in mind