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r CAMBRIA Water Sampling Water samples, if they are collected from the boring, are either collected using a driven Hydropunch®type sampler or are collected from the open borehole using bailers. The ground water samples are decanted into the appropriate containers supplied by the analytic laboratory. Samples i are -C,labeled,placed in protective foam sleeves, stored on crushed ice at or below 4 and transported under chain-of-custody to the laboratory. Laboratory-supplied trip blanks accompany the samples t and are analyzed to check for cross-contamination. An equipment blank may be analyzed if non- dedicated sampling equipment is used. Grouting If the borings are not completed as wells, the borings are filled to the ground surface with cement grout poured or pumped through a tremie pipe. i 'r MONITORING WELL INSTALLATION, DEVELOPMENT AND SAMPLING i Well Construction and Surveying i l ` Ground water monitoring wells are installed to monitor ground water quality and determine the ground water elevation, flow direction and gradient. Well depths and screen lengths are based on ground water depth, occurrence of hydrocarbons or other compounds in the borehole, stratigraphy and State and local regulatory guidelines. Well screens typically extend 10 to 15 ft below and 5 ft above the static water level at the time of drilling. However, the well screen will generally not extend into or through a clay layer that is at least three ft thick. i Well casing and screen are flush-threaded, Schedule 40 PVC. Screen slot size varies according to the sediments screened,but slots are generally 0.010 or 0.020 inches wide. A rinsed and graded sand occupies the annular space between the boring and the well screen to about one to two ft above the well screen. A two ft thick hydrated bentonite seal separates the sand from the overlying sanitary surface seal composed of Portland type 1,11 cement. Well-heads are secured by locking well-caps inside traffic-rated vaults finished flush with the ground surface. A stovepipe may be installed between the well-head and the vault cap for additional + security. The well top-of-casing elevation is surveyed with respect to mean sea level and the well is surveyed s for horizontal location with respect to an onsite or nearby offsite landmark. I { Page 2 of 3 �I