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.r Wright Environmental Services, Inc. Monitoring Well Construction 1. The proper permits will be obtained from the appropriate agency or water district, scheduling a Well Inspector as required to be present to witness the installation of the annular seal Soil borings will be drilled with a continuous-flight hollow-stem auger of nominal 8 inches outside diameter (to leave 2-inch annular space for well construction). All augers will be thoroughly steam-cleaned prior to arriving at the site The augers will be steamed cleaned between bonngs at a location well away from the proposed borings or adequate clean auger will be available to complete all of the wells without reusing auger sections 2. The borings will be advanced to the uppermost water bearing zone (or a depth of 45 feet if a saturated zone is not encountered and in absence of other exploration depth specifications). If a saturated zone is encountered, the boring will advance no further than 15 feet below first encountered groundwater or 5 feet into the underlying clay aquitard If entered, a seal will be placed in the overdnlled portion of the aquitard 3. During the drilling operations, 55-gallon drums will be on site to contain potentially contaminated soils, drilling muck and rinse water to minimize surface contamination 4. Where borings are completed as groundwater monitoring wells, 2-inch ID schedule 40 PVC blank pipe will be used Well screen selection will be 2 inch ID Schedule 40 PVC pipe with 0 020 inch machine slot (in absence of other specifications) Sections will be threaded and screwed flush together, glues will not be used Screens will extend 3-5 feet above first encountered groundwater The annulus of the perforated section will be packed with clean #3 or #4 Monterey Sand, Lonestar 2/12 Sand or equivalent, to a level about 2-feet above the screen interval (field experience has shown this monitoring well design has worked well in stratified alluvial and fine grained environments, if special well designs supersede this design, a specification will be attached) Final well design will be adjusted in the field to site specific subsurface conditions observed in the borehole, and well screens or slots will be placed so as not to interconnect two possible aquifers or uncontaminated vadose zone strata Screens will extend a nominal length (up to 5 feet) above first encountered unconfined groundwater for floating product detection where needed A 1-2 foot thick bentonite seal will be placed on top of the sandpack A cement grout annular seal which extends to the surface will be placed by tremie line from the bottom to top of the remaining annular space above the bentonite Sealing can be modified as regulatory input requires 6. The top of the well casing will be locked to prevent contamination and tampering An above-grade or at-grade well completion will depend upon well location At-grade completions require traffic rated boxed set in concrete or cement grout dust above grade Above-grade completion will require a 6-inch diameter locking, steel protective "stovepipe" casing and a Christy, or equivalent, traffic box and concrete pad and surface poles or barriers to mark the location WES Sampling Protocols last rev 5/96 Page 4