ARCHIVED REPORTS_XR0011958 - Laserfiche WebLink

Home Browse Search

;S Y . Additional Groundwater Investigation and Remediation Feasibility Evaluation Work Plan Stockton Center Site Authority-University Park January 25,2005 1 Page 8 l� The drill cuttings and steam cleaning efflucnt will be placed in DOT-approved 55-gallon drums, sealed, A labeled, and left on-site pending laboratory analyses. Condor can assist the SCSA with removal of the soil J and water, if requested. 5.5 SHALLOW MONITORING WELL CONSTRUCTION The shallow monitoring well located in the source area will be constructed with 15 feet of 4-inch outside diameter, Schedule 40, flush-threaded, machine-slotted PVC screen (slot size 0.020). The two down gradient monitoring wells, located east and southeast of the source area, will be constructed with 15 feet of 2-inch outside diameter, Schedule 40, flush-threaded, machine-slotted PVC screen (slot size 0.020). Flush-threaded PVC bottom caps will be placed at the bottom of the screen sections. Blank PVC casing k will be installed above the screens to the ground surface. A filter pack of#3 Monterey sand will be placed in the annular space to approximately two feet above the screen while the augers are in place. The depth of the sand in the well annulus will be monitored with a Y weighted tape measure while the sand is being placed and the augers are being gradually retracted to avoid bridging. To form a protective seal, approximately three feet of bentonite chipswill be installed above the sand. The depth of the chips in the well annulus will be monitored with a weighted tape t measure while the chips are being placed and the augers are being gradually retracted to avoid bridging. . The bentonite chips will be hydrated with potable water. The chips will be allowed to hydrate for at least 20 minutes, and a surface seal grout mixture of Type I/H neat cement containing less than 5% bentonite �p4 solids will be pumped via a tremie pipe into the annulus and will extend from the bentonite to the ground surface. Depending on the stability of the boreholes, the augers may be removed before or during emplacement of the grout. The tremic pipe will remain near the top of the bentonite seal until the pumped grout is forced to the surface. The monitoring wells will be completed with locking traffic boxes. 5.6 MONITORING WELL SURVEYING,DEVELOPMENT,AND SAMPLING k Condor's licensed land surveyor will determine the location and relative elevation of the well.collars following the installation of the monitoring wells. The well collars will be surveyed with a vertical accuracy of 0.01 foot and horizontal accuracy of 1.0 foot. The measuring point for water-level measurements will be marked on each well collar. The groundwater gradient will be estimated using the survey information and the depth to water measurement in each well. At least 48 hours following construction, the monitoring wells will be'developed by surging and bailing the groundwater in each well until the discharge water is relatively free of sediment (clear to the unaided { eye). The monitoring wells will be purged until the temperature, electrical conductivity and pH of the water has stabilized. All well-development equipment.will be cleaned prior to use in each well by washing in a solution of laboratory-grade, non-phosphate detergent and de-ionized water, and double rinsing with de-ionized water. The purge water discharged from the wells during development will be # placed in 5 5-gallon,drums, sealed, labeled, and left on-site pending results of laboratory analyses. Groundwater samples will be collected at least 48 hours following development of the monitoring wells. Prior to .sample collection, the static water level in each well will be measured to the nearest 0.01-foot with a battery-operated, flat tape water level meter. A disposable bailer will be lowered into each well to check for floating product,petroleum odors, and/or sheen. If floating product is present,the thickness will be measured. Laboratory samples will not be collected from wells that contain floating product. � The monitoring wells will be purged using a clean, disposable bailer until the temperature, electrical conductivity, and pH of the water has stabilized.. At least three casing volumes of water will be purged �«1 CONDOR 4. .