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All field and office work, including exploratory boring logs, are prepared <br /> under the direction of a registered professional engineer. <br /> Monitorin Well Installation <br /> Monitoring well casing and screen will be constructed of Schedule 40 flush- <br /> joint threaded polyvinylchloride (PVC). The well screen will be factory ' <br /> mill-slotted unless additional open area is required (e.g. conversion to an <br /> extraction well in a low-yield aquifer). The screen Iength will be placed t <br /> adjacent to the aquifer material to a minimum of 2 feet above encountered <br /> water. No screen shall be placed in a borehole that potentially created <br /> hydraulic interconnection of two or more aquifer units. Screen slot size and <br /> well sand pack will be compatible with encountered aquifer materials as <br /> confirmed by sieve analysis. <br /> Monitoring wells will be completed below grade (Figure 2) unless special <br /> conditions exist that require above-grade completion design. In the event a <br /> monitoring well is required in an aquifer unit beneath an existing aquifer, <br /> the upper aquifer will be sealed off by installing a steel conductor casing <br /> with an annular neat cement or cement-bentonite grout seal. This seal will <br /> be continuously tremie pumped from the bottom of the annulus to ground <br /> surface. <br /> The monitoring well sand pack will be placed adjacent to the entire screened <br /> interval and will extend a recommended minimum distance of 2 feet above <br /> the top of the screen. No sand pack will be placed that interconnects two or <br /> more aquifer units. A minimum 2 foot bentonite pellet or bentonite slurry <br /> seal will be placed above the sand pack'. Sand pack, bentonite, and cement . <br /> seal levels will be confirmed by sounding the annulus with a calibrated <br /> weighted tape. The remaining annular space above the bentoniteseal will be <br /> grouted with a bentonite -cement mixture and will be tremie-pumped from <br /> the bottom of the annular space to the ground surface. The bentonite <br /> content of the grout will not exceed S percent by weight. A field log of <br /> boring and a field well completion form will be prepared by Enviros for <br /> each well installed. <br /> Decontamination of drilling equipment before drilling and between wells <br /> will consist of steam cleaning, and/or Alconox wash. <br /> Well Surveying t <br /> Monitoring wells will be surveyed to obtain top of box elevations to the <br /> nearest±0.01 foot. Water level measurements will be recorded to the <br /> nearest-1-0.01 foot and referenced to Mean Sea Level (MSL). If additional <br /> well are required, existing and newly installed wells are surveyed relative to <br /> MSL. <br /> C <br /> I <br /> en viros o <br /> i <br />