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covered with plates and/or backfilled <br /> The minimum hole clearance depths are 4 feet below ground surface (bgs) outside the critical <br /> zone and 8 feet bgs within the critical zone and are conducted as follows <br /> • 0 to 4 bgs The area to be cleared exceeds the diameter of the largest tool to be <br /> advanced and is sufficiently large enough to allow for visual inspection of any <br /> obstructions encountered The first I to 2 feet is delineated by hand digging to <br /> remove the soil, then the delineated area is probed to ensure that no obstructions <br /> exist anywhere near the potential path of the drill auger or push-type sampler <br /> Probing is extended laterally as far as possible Hand augering or post-hole <br /> digging then proceeds, but only to the depth that has been probed If subsurface <br /> characteristics prohibit effective probing, a hand auger is carefully advanced past <br /> the point of probing In this case, sufficient hand augering or post-hole digging is <br /> performed to remove all the soil in the area to be delineated For soil borings <br /> located outside of the critical zone, an attempt should be made to probe an <br /> additional 4 feet <br /> • 4 to 8 bgs For the soil borings located inside the critical zone, probing and hand <br /> clearing an additional 4 feet is performed If probing is met with refusal, then <br /> trained personnel advance a hand auger without excessive force An alternate or <br /> additional subsurface clearance procedures may also be employed, as required by <br /> clients, permit conditions, and/or anticipated subsurface conditions (for example, <br /> near mayor utility corridors or in hard soils) Alternate clearance techniques may <br /> include performing a geophysical investigation or using an air knife or water <br /> knife If subsurface conditions prevent adequate subsurface clearance, the drilling <br /> operation is ceased until the client approves a procedure for proceeding in writing <br /> If any portion of the UST system is encountered, or if there is any possibility that <br /> it has been encountered, the work ceases, and the client is notified immediately If <br /> there is reason to believe that the product system has been damaged, the <br /> emergency shut-off switch is activated The client will decide if additional <br /> uncovering by hand is required If it is confirmed that the UST system has been <br /> encountered, tightness tests are performed The hole is backfilled only with client <br /> approval <br /> Main\D\Envuonmental\ParmarTexaco\Workplan\D42003 wpd 2 <br />