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SLE ARWATER G a o U P t ,1\1 C Environmental Services screen size and filter pack on the basis of general site stratigraphy, and specifically the finest significantly thick layer of sediment to be screened Commonly selected grades are Lone Stare 3, 2/12 or 2/16 (or equivalent) with 0 020-inch slotted screen and Lone Star® 1/20 with 0 010- inch slotted screen Well eat and Completion A muumum two foot seal of bentonite is placed above the sand pack The bentonite seal is hydrated by either formation water or potable water Neat cement or a cement/bentonite grout mixture seals the remaining annular space to the surface If bentonite is used in the grout mixture, it does not exceed 5% by weight The grout is placed using a tremae pipe, if the top of the bentonite is more than 20 feet below grade, or if water is present in the boring above the bentonite seal A watertight locking cap and protective traffic-rated vault box is installed on top of each well Well construction details are presented on the Field Exploratory Soil Boring Log Following completion of a well, Clearwater completes and submits, or ensures that the driller has sufficient information to complete and submit, the state-required Well Completion Report or equivalent document Well Development All newly installed wells are developed prior to sampling to remove fine grained sediments from the well and stabilize the filter pack and the disturbed aquifer materials Development takes place prior to or at least 24 hours after setting the seal on the well, unless otherwise directed by a local oversight agency Well development consists of surging with a surge block and removing water from the well with either a pump or bailer, until the well is free of sediment, or until, at least 10 well casing volumes have been removed Depth to bottom is measured to determine casing volume If the well is sampled immediately following development, temperature, pH, specific conductance and turbidity (qualitative) are monitored durmtg well development (see section "Groundwater Sampling") All development equipment is cleaned prior to use and between wells with an Alconox®solution, then rinsed in potable water All data collected during development are recorded on the Well Development Data Sheet and, if necessary, the Purging Data Sheet Well Surveying All well elevations are surveyed at the north side of the top of casing to the nearest ±0 01 foot The exact survey pount (at the center of the survey rod or, if the casing stub is uneven, the point of contact between casing and rod) is clearly marked and maintained on the casing rim Elevations are referenced either to meati sea level or to a protect datum A project datum is typically chosen so as to mirurnize the possibility of its' later disturbance For instance, fire hydrants are commonly selected Where required, the wells are surveyed by a licensed land surveyor, relative to mean sea level Groundwater Sampling ouzndwater Monntorin Pnor to beginrung, a decontamination area is established Decontamination procedures consist of scrubbing downhole equipment in an Alconox® solution wash (wash solution is pumped through any purging pumps used), and rinsing in a first rinse of potable water and a second rinse of potable water or deionzzed water if the latter is required Any non-dedicated down hole equipment is decontaminated pnor to use CLEARWATER GROUP,INC 3 August 26, 1996