ARCHIVED REPORTS_XR0004525 - Laserfiche WebLink

Home Browse Search

CAMBRIA Water Sampling Water samples, if they are collected from the bonng, are either collected using a driven Hydropunch D 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 are labeled, placed in protective foam sleeves, stored on crushed ice at or below 4',C, and transported under chain-of-custody to the laboratory Laboratory-supplied trip blanks accompany the samples 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 MONITORING WELL INSTALLATION, DEVELOPMENT AND SAMPLING Well Construction and Surveying 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 hydrocarbon% 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 Well casing and screen are flush-threaded, Schedule 40 PVC Screen slot size vanes 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 LH 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 for horizontal location with respect to an onsite or nearby offsite landmark Well Development Wells are generally developed using a combination of ground water surging and extraction Surging agitates the ground water and dislodges fine sediments from the sand pack After about ten nunutes of surging,ground water is extracted from the well using bailing, pumping and/or reverse air-lifting through an eductor pipe to remove the sediments from the well Surging and extraction continue until at least ten well-casing volumes Of ground water are extracted and the sediment volume in the ground water is negligible This process usually occurs prior to in5tallmg the sanitary surface seal to ensure sand pack stabilization If development occurs after surface seal installation, then development occurs 24 to 72 hours after seal installation to ensure that the Portland cement has set up correctly �y Page 2of3