ARCHIVED REPORTS XR0001633 - Laserfiche WebLink

Home Browse Search

AM dOL low KLEINFELDER • The wells will be generally screened from 30 feet to 55 feet below subgrade If an apparent aquntard is encountered, the well is usually terminated 1 to 2 feet into the aquitard Effort is made not to screen across two aquifers If confined aquifer conditions or high vadose zone contamination is encountered, the well screen in usually not set above the depth of first encountered groundwater Wells are usually not set in areas of suspected significant soil contamination * The PVC pipe and end caps will be steam cleaned prior to installation • The annular space between the screen and the wall of the boring is backfilled with the appropriate clean Lone Star Industries 0/30 or 2/12 Monterey sand to approximately 2 feet above the top of the perforated sections Based on soil logs or a sieve test, modifications may be made regarding the size of sand to be used Installation of the 0/30 sand may require that the sand be tremmied, using clean water In this event, a sample of the tremie water is collected, unless the source is thought to be clean • A 3- to 5-foot bentonite plug is placed above the sand pack to provide an annular seal against surface water infiltration and to reduce the potential for cement grout to infiltrate into the water • The-remaining annular space is filled to the surface with-tremmned cement bentonite grout(surface seal)to the surface • The wells will be secured in a below-ground locking stovepipe and the well heads enclosed in a water-tight cement utility box set flush to the ground surface A-3 2 Monitoring Well Development The wells are developed to reduce the effects of drilling on the formation and to increase the effective hydraulic radius of the well Monitoring wells are generally developed 24 to 48 hours after installation to allow the grout to set Each well is first sampled with a clear acrylic bailer to visually inspect for hydrocarbon layer or sheen If no product layer of sheen is observed on the water, the well is developed by surging, pumping, or balling Surging along the screened interval of the well is performed to draw the sediment from the formation into the filter pack and the well and to set the sand pack The sediment-laden water is purged from the well at a rate of between 0 75 to 10 gallons per minute (gpm) depending on recharge rate and casing size Development continues until the discharge runs relatively clear of fines Approximately 5 to 10 well volumes generally are removed from each monitoring well Discharge water is stored in 55-gallon drums and left on site for later discharge or disposal by the client, depending on laboratory results ETH and WC/94 f S 3 oS e Copyright 1994 Kleinfelder, Inc Pa