WORK PLANS - Laserfiche WebLink

Home Browse Search

GR Field Methods and Procedures Construction of Monitoring Wells Monitoring wells are constructed in the exploratory soil borings with Schedule 40 polyvinyl chloride (PVC) casing. All joints are thread joined;no glues,cements,or solvents are used in well construction. The screened interval is constructed of machine-slotted PVC well screen which generally extends from the total well depth to a point above the groundwater. An appropriately-sized sorted sand is placed in the annular space adjacent to the entire screened interval. A bentonite transition seal is placed in the annular space above the sand, and the remaining annular space is sealed with neat cement or cement grout. Wellheads are protected with water-resistant traffic-rated vault boxes placed flush with the ground surface. The top of the well casing is sealed with a locking waterproof cap. A lock is placed on the well cap to prevent vandalism and unintentional introduction of materials into the well. Measurement of Water Levels The top of the newly-installed well casing is surveyed by a California-licensed Land Surveyor to mean sea level (MSL). Depth-to-groundwater in the well is measured from the top of the well casing with an electronic water- level indicator. Depth-to-groundwater is measured to the nearest 0.01-foot,and referenced to MSL. i Well Development and Sampling The purpose of well development is to improve hydraulic communication between the well and the surrounding aquifer. Prior to development,each well is monitored for the presence of floating product and the depth-to-water is recorded. Wells are then developed by alternately surging the well with a vented surge block,then purging the well with a pump or bailer to remove accumulated sediments and draw groundwater into the well. Development i continues until the groundwater parameters(temperature, pH, and conductivity) have stabilized. Storing and Sampling of Drill Cuttings I Drill cuttings are stockpiled on and covered with plastic sheeting and samples are collected and analyzed for disposal classification on the basis of one composite sample per 100 cubic yards of soil. Stockpile samples are composed of four discrete soil samples, each collected from an arbitrary location on the stockpile. The four discrete samples are then composited in the laboratory prior to analysis. I Each discrete stockpile sample is collected by removing the upper 3 to 6 inches of soil, and them driving the stainless steel or brass sample tube into the stockpiled material with a hand,mallet,or drive sampler. The sample tubes are then covered on both ends with Teflon sheeting or aluminum foil,capped,labeled,and placed in a cooler with blue ice for preservation. A chain-of-custody form is initiated in the field and accompanies the selected soil samples to the analytical laboratory. Stockpiled soils are covered with plastic sheeting after completion of sampling. I I