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2o r...� February 18, 2014 so? 2•µm� /'�r� c•- 3.' ,�fLi2 q) �6`y �J✓'/ J � Ms. Vicki McCartney Sp Page 2 of 4 Reference: Work Plan for Well Destruction 7-Eleven Store #19976 Weld Destruction-The following wells will be destroyed: �rr3 A-J"r 11.S, - ;6 • MW-1, MW1A(onsite nested groundwater monitoring wells); �, ..' • MW-5, MW-5A(onsite nested*groundwater monitoring wells); A�4 /� L- �,, > • MW-4, MW-4A(offsite nested*groundwater monitoring wells); /H �*- - i A 50 • " k 30 - /J;33 - / W M S g• • MW-2, M -3, W-6, and MW-8 (onsite groundwater monitoring wells); �, � • MW-7(offsite groundwater monitoring well); 3. S� SP-1, SP-1A(onsite nested oxygen injection wells); .rs-ty- as,�-• • SP-2, SP-3 (onsite oxygen injection wells), and; • SG-12 through SG-16 (onsite soil-gas probe wells). _ * Although wells MW-5/MW-5A, and MW-4/MW-4A have been referred to as nested wells, the well logs, report text, and site photos indicate they were each constructed within their own eight-inch diameter boreholes approximately four feet apart. The wells will be destroyed according to the following program, based on SJCEHD requirements (except where noted) and the most recent groundwater and soil analytical data. The top five feet of native material surrounding nested wells (MW-1, MW1A and SP-1, SP-1A) will be removed using air-knife and vacuum equipment, and hand tools to ensure the absence of any underground utilities, in accordance with Stantec standard health and safety procedures. The resulting excavation will then be backfilled with native material or sand to help keep the auger bit over the well during over-drilling. Nested wells will then be destroyed by over-drilling using hollow stem augers of sufficiently-large diameter, and a guide rod inside the deepest casing, to ensure removal L- of all well contents-both well casings, screens,filter pack,grout sealant. Groundwater monitoring well MW-:9 wild be destroyed in a similar manner to remove the entire well due to the presence of methyl tertiary butyl ether (MtBE) detected during the final groundwater monitoring event in the first quarter 2013. Soil-gas probes SG-12 through SG-16 will be destroyed using air-knife and vacuum equipment,-a> -1 1-1 tools because of their shallow depth (five feet). d I(- G= Wells MW-3, MW-4, MW-41, MW-5; 5A W-�7, MW-B, SP-2, and SP-3 will be pressure grouted in the following manner. Eac well will be sounded to ensure the casing is free of h{L obstructions to its total depth and a neat Portland cement grout will be mixed and umpe—e - through a tremmi i e from the well bottom to the surface. Any groundwater displace — Al surface will be cap ured and contained in properly labeled Department of Transportation (DOT) 55-gallon drums f r disposal, or depending on the quantity, it may be used to mix additionkl-- grout. After the tr mmie pipe is removed, a pressure fitting and gauge will be attached to the top of the well casing nd a pressure of approximately©pounds per square inch will be applied for f e minutes. The ressure fittingwill then be remov d and the rout level will be observed inside g Design with community in mond