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removing an estimated 638 tons of gasoline contaminated soils from above and below the water
<br /> table(maximum depth of excavation 30 feet below surface).
<br /> The property owner originally installed five onsite monitoring wells(MW 1,MW2,MW3,MW4
<br /> and MW5). Two additional cluster wells(R1A and RIB)and four piezometers(PZ1A,PZ1B,
<br /> PZ2A and PZ2B)were installed to aid in the investigation of soil and groundwater conditions at the
<br /> site. Prior to over-excavation, monitor well MW I was destroyed by over drilling and during
<br /> excavating cluster wells RIA and RIB along with piezometers PZIA, PZIB, PZ2A and PZ2B were
<br /> removed by excavating,removing all well materials. At the current time the following are the
<br /> remaining active groundwater monitoring wells for this site: MW2, MW3,MW4, MWS, MW6A,
<br /> MW6B,MW7A,MW7B,MWBA,MWBB,MW9A and MW9B. The following is the remaining
<br /> groundwater recovery well: MW 10 and the following are the remaining soil gas sampling wells:
<br /> SG-1, SG-2, SG-3, SG-4 and SG-5, see Figure 3,Table I and Appendix A—Well Construction
<br /> Logs.
<br /> WELL DESTRUCTION
<br /> San Joaquin County Public Health Services, Environmental Health Division (SJCPHS, EHD) -
<br /> Well Standards does not indicate how monitor wells should be destroyed. In conversation with
<br /> SJCPHS, EHD monitor well destructions are site specific. The following methods have been
<br /> approved in the past.
<br /> 1) Drill out casing and well construction material,tremie grout boring to surface.
<br /> 2) If no soil contamination exists, remove any slough/debris from well, pressure grout
<br /> tremie method to surface, over drill upper five feet, place cement cap, backfill boring with
<br /> soil and replace surface to match like.
<br /> 3) Remove debris from well, knock out bottom plug (Popsicle). Place tremie pipe to
<br /> bottom of well, while pulling casing from well, tremie grout to surface, match surface to
<br /> like.
<br /> Based on the review of the above mentioned well destruction methods, the following wells will,,be
<br /> destr yed by method 2 — Pressure rout; MW3, MW4, MW5, MW7A, MW7B, M A, U
<br /> M 8B,MVA,MW9B and �!'),�Nl ,
<br /> fvo ff No
<br /> �l Pressure Grout Monitor Well MW10.
<br /> / MwlO was installed into the over-excavation clean backfill(pea gravel). To remove the well or to
<br /> pull the casing would cause undermining of the excavation area. The well is situated in a 3 foot by
<br /> 3 foot square traffic box, four feet deep. The 4 inch casing will be cut off at the base of the traffic
<br /> �1b ` box and tremie pipe pressure grouted, allowing the grout to fill the bottom foot of the traffic box,
<br /> the remainder of the box will be backfilled and compacted with clean road base,the lid and lid ring
<br /> will be removed and the surface will be resurfaced with asphalt. /V
<br /> The two buried 2 inch PVC laterals, two 1 inch electrical PVC laterals and one 4 inch PVC conduit
<br /> (housed I inch groundwater recovery hose) servicing well MW 10 will be filled with cement and
<br /> 2 Sanchez site restoration WP 1-2012
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