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ealo ccdTechnicsI" Page 4 <br /> G g g <br /> Additional Investigation Work Plan <br /> Cardoza(Main St) <br /> Project No 662 2 <br /> October 8,2001 <br /> ' The wells will be constructed using two inch (2") schedule 40 PVC casing with flush <br /> threads Before installing the bentonite seal the well will be surged using a clean surge <br /> block to achieve maximum filter pack density A granular bentonite transition seal will be <br /> installed above the sand filter pack and hydrated with clean tap water The transition seal <br /> on the deeper well will consist of weighted bentonite pellets A surface seal will be <br /> achieved by pumping a neat cement grout (augmented with < 4% bentonite) through the <br /> ' augers, as they are withdrawn to ensure that an integral grout seal is achieved The wells <br /> will be secured with locking watertight caps encased in flush mounted traffic rated well <br /> boxes Well construction details are illustrated in Figure 3 <br /> 2.6 Monitoring Well Development <br /> After the well sealing materials have set (>24 hours) all of the new wells will be developed <br /> (using mechanical surging and pumping methods) until a clear stream of water is obtained <br /> The wells will be purged and groundwater samples collected after well development All <br /> development and purge water will be containerized in 55 gallon DOT approved containers <br /> and stored on site until their disposition can be arranged <br /> 3 0 GROUNDWATER MONITORING <br /> ' The new wells will be incorporated into the current quarterly sampling/monitoring schedule <br /> The schedule will be augmented with monthly depth to groundwater measurements to better <br /> define groundwater direction gradient trends <br /> 3.1 Groundwater Sampling Procedure <br /> ' Before sampling is attempted the wells will be sounded for depth to water and then a clear <br /> disposable bailer will be used to determine if floating product is present The wells will be <br /> purged of at least 3 well volumes of stagnant water using either a submersible pump, a <br /> dedicated Waterra pump or a stainless steel bailer Purging will continue until the <br /> ' temperature, conductivity, and pH of the groundwater has stabilized (<10% variation <br /> between three readings) indicating that formation water representative of aquifer conditions <br /> entering the well is being sampled These water quality parameters are measured at <br /> intervals of each well volume purged <br /> A stainless steel bailer, disposable plastic bailer or dedicated Waterra pump will be used to <br /> collect each sample Care will be taken to minimize sample agitation from the initial filling <br /> ' of the bailer to the transfer of the sample to the VOA vial and glass amber liter bottles <br /> Once the sample container is filled and capped, the bottle will be inverted, tapped, and <br /> checked for headspace bubbles The sample container is identified and labeled with a <br /> ' unique designation, inserted into foam holders and placed in an ice chest cooled to 4°C for <br /> transport to the laboratory <br /> All non-disposable sampling equipment will be decontaminated using a steam cleaner <br /> before and between uses The effectiveness of the decontamination procedure is ensured by <br /> using the following quality control measures <br /> • Disposable gloves will be used by the technician to collect all samples and will be <br /> changed with each sampling event <br /> 1 <br />