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i:. 4ol %W/ w- SOP 3 - GROUNDWATER MONITORING WELL CONSTRUCTION Drilling and well completion will be observed by a geologist or engineer under the �- supervision of Licensed Engineer or Geologist. Monitoring-Well Locations and Depths Monitoring-well locations, depths and screened intervals will be proposed in a Workplan Addendum. Monitoring-Well Materials and Specifications Monitoring wells will be constructed with Schedule 40, two-inch (inside diameter), poly vinyl chloride (PVC) casing. Flush-joint well casing will be utilized, and no chemical cements or solvents will be used in the construction of the wells. The top of each well casing will be covered with a locking watertight plug, and a threaded PVC plug will be installed at the low bottom of each well. The screened interval of each well will consist of Schedule 40, machine-slotted PVC well screen, with 0.020-inch slots. The well screen will extend from approximately 5 feet above the observed groundwater level to the maximum depth of each monitoring-well boring (10 feet below the groundwater surface) to accommodate expected fluctuation in water levels. �., The annular space of each well will be packed with a No. 2/12 size sand to approximately two feet above the perforations. A two foot thick bentonite seal will be placed above the sand and hydrated with potable water to provide a filter media between the well pack and r►. surface seal. The remaining annulus will be backfilled with neat cement grout to within approximately one foot of the existing grade. Well casing, sand, and bentonite will be placed through the center of the hollow-stem auger. Grout backfill will be placed through the center �- of the augers or tremmied from the bentonite seal to within one foot of the ground surface. The exception would be for those wells where the total depth of grout is less than 25 feet and where grout will not be placed in groundwater. In this case, the grout will be allowed to free-fall from the top of the well-boring. Water and dust-resistant steel utility boxes with either PVC or galvanized steel skirting will be placed over the well casing. The boxes will be set in place with concrete approximately 1/2-inch above the surrounding grade. The top of each well casing will be surveyed relative to a local USGS or temporary benchmark, as appropriate. Monitoring-Well Development Prior to development, water levels will be measured in each well. Water from each well will be sampled for odor, color and clarity by lowering a clear Teflon bailer partially through the groundwater interface. Wells will be developed using bailers, surge blocks, and pumps to WorWan SOPc-014MB-May.1995 SOP 3 —1 &Associates