WORK PLANS_CASE 1 - Laserfiche WebLink

Home Browse Search

GeologicalTecknics Inc. Page 3 U.S. Can Company Soil and Groundwater Investigation Work Plan Project No. 397.2 August 9, 1996 2.3 Monitoring Well Installation One of the borings will be advanced into the saturated zone and a groundwater monitoring well will be installed. We propose to continuously sample this boring and retain cores for future evaluation. The monitoring well will be constructed using 2.0 inch diameter schedule 40 PVC casing with flush threads. The screened interval will extend from (5) feet above the water table to (10) feet below the water table. Groundwater is expected to be located between 10-30 feet below grade. If a significant clay unit is encountered while drilling the well boring, the well may be seated no greater than (3) ft into that fine grained unit. A #3 sand filter pack will surround and extend two feet above the 0.020" screened interval. Before installing the bentonite seal the well will be surged using a clean surge block to achieve maximum filter pack density. A granular bentonite transition seal will be installed above the sand filter pack and hydrated with clean tap water. A surface seal will be achieved by pumping a neat cement grout (augmented with < 4% bentonite) through the augers as they are withdrawn to ensure that an integral grout seal is achieved. The well will be secured with a locking watertight cap encased in flush mounted traffic rated well box or above grade monument which ever is appropriate. After the well sealing materials have set (>24 hours) the well will be developed (using mechanical surging and pumping methods) until a clear stream of water is obtained. The well will be purged and groundwater samples collected after well development. All development and purge water will be containerized in 55 gallon DOT approved containers and stored on site until their disposition can be arranged. 2.4 Groundwater Sampling Procedure The following is a procedure for the sampling of groundwater from the well: Before sampling is attempted the well will be sounded for depth to water and then a clear disposable bailer will be used to determine if floating product is present. The well will be purged of at least 3 well volumes of stagnant water using either a submersible pump or a stainless steel bailer. Purging will continue until the temperature, conductivity, and pH of the groundwater has stabilized (<10%variation between three readings) indicating that formation water representative of aquifer conditions is entering the well. These water quality parameters are measured at intervals of each well volume purged. A stainless steel or disposable plastic bailer will be used to collect each sample. Care will be taken to minimize sample agitation from the initial filling of the bailer to the transfer of the sample to the VOA vial and glass amber liter bottles. Once the sample container is filled and capped, the bottle will be inverted, tapped, and checked for head space bubbles. The sample container is identified and labeled with a unique designation, inserted into foam holders and placed in an ice chest cooled to 4°C for transport to the laboratory. All non disposable sampling equipment is decontaminated using a steam cleaner before and between uses. The effectiveness of the decontamination procedure is ensured by using the following quality control measures: • Disposable gloves will be used by the technician to collect all samples and will be changed with each sampling event.