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CLEARWATER G R O L! P. I N C. All wells will be surveyed to',the.north side of the top of casing for elevations to the.nearest '±0.01 foot. Elevations will be, referenced either .to mean. sea- level'or to a project datum. -A project datum is typically chosen for 'its location such that it will remain'unchanged in the event of site construction or other- site .disturbances. .Where requiredE, the wells will be surveyed by a : : licensed land surveyor, relative to`the neare4st benchmark. .Well Development AlI newly installed wells will be developed prior to sampling to remove fine: grained.sediments from the well and stabilize the filter pack-and the disturbed aquifer- materials. Well development consist of surging with a surge ` block and removing water-from the well ith either a.pump or bailer, until the well is'. free of sediment, or after 10 well._casing volumes have been removed. Where appropriate, temperature, pH, specific conductance and turbidity will be monitored' during well development. ,-.-All development. .. . equipment .will be cleaned rior to use an between wells with an Alconox.. P . solution, then rinsed in clean water. ' All data-collected during development FIF will be presented on the.well''development data.sheet. r Ground Water Sampling . Prior to the start of work, a 'decontamination area will be established. This will be in a secured area and.:consist of an Alconox solution wash, a first rinse and a second rkise. Any down hole equipment will be decontaminated prior to use. . -r Prior, to purging and sampling any well, the static water level will be measured with an electronic water sounder or an oil/water interface probe to the nearest ±0.01 foot. If.floating product is detected, interface probe results will be confirmed by lowering a clear disposable polyethylene bailer down the well and measuring the product thickness to the nearest ±0.01 foot, in the bailer. . Any monitoring well containing detectable- amounts of floating product- ,will not.be purged, or sampled. Field observations such as well integrity as well - as water level measurements and floating product thicknesses will be noted on the gauging data/purge calculations,form. All monitoring wells to be sampled shall be purged using either a PVC bailer or a submersible pump. : Physical parameters (pH,- temperature and conductivity) of the purge water will be monitored for stabilization during r CLEARWATER GROUP,INC. 3 April 28, 1995 k '