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All field and office work, including exploratory boring logs, are prepared ' under the direction of a registered professional engineer. F Monitoring Well Installation Monitoring well casing and screen will be constructed of Schedule 40 flush- joint threaded polyvinylchloride (FVC). The well screen will be factory mill-slotted unless additional open area is required (e.g. conversion to an extraction well in a low-yield aquifer). The screen length will be placed adjacent to the aquifer material to a minimum of 2 feet above encountered water. No screen shall be placed in a borehole that potentially created hydraulic interconnection of two or more aquifer units. Screen slot size and well sand pack will be compatible with encountered aquifer materials as confirmed by sieve analysis. Monitoring wells will be completed below grade (Figure 2) unless special conditions exist that require above-grade completion design. In the event a monitoring well is required in an aquifer unit beneath an existing aquifer, the upper aquifer will be sealed off by installing a steel conductor casing with an annular neat cement or cement-bentonite grout seal. This seal will be continuously tremie pumped from the bottom of the annulus to -round. surface. The monitoring well sand pack will be placed adjacent to the entire screened interval and will extend a recommended minimum distance of 2 feet above the top of the screen. No sand pack will be placed that interconnects two or more aquifer units. A minimum 2 foot bentonite pellet or bentonite slurry seal will be placed above the sand pack. Sand pack, bentonite, and cement . seal levels will be confirmed by sounding the annulus with a calibrated 1 weighted tape. The remaining annular space above the bentonite seal will be grouted with a bentonite -cement mixture and will be tremie-pumped from the bottom of the annular space to the ground surface. The bentonite ;€ content of the grout will not exceed 5 percent by weight. A field log of boring and a field well completion form will be prepared by Enviros for each well installed. Decontamination of drilling equipment before drilling and between wells will consist of steam cleaning, and/or Alconox wash. Well Surveying Monitoring wells will be surveyed to obtain top of box elevations to the nearest±0.01 foot. Water level measurements will be recorded to the nearest±0.01 foot and referenced to Mean Sea Level (MSL). If additional well are required, existing and newly installed wells are surveyed relative to MSL.