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5^ t 8, 1991ai bruy GAcCO Gasoline Station Fepage 3 Project No. 3-30054-31 the slotted screen section. The screened interval wilt bee within the first encountered wwater and approximately 35 feet in length. The long screen interval is due to Targe fluctuations in groundwater levels known to occur at the site. Approximately 1/2 to 1 foot of bentonite pellets will be placed on top of the sand pack and hydrated to act as a seal. The remaining portion of the annular space will be sealed with cement grout. The top of the well will be set in concrete in a water-tight, traffic-rated vault box at grade. A PVC locking expansion plug will be used to seal the wellhead and provide security. Typical groundwater monitoring well details are shown in Figure 3. Well Development After construction, each well will be developed to improve the hydraulic conductivity between the well and the natural formation. Development will be conducted by a surge and purge method. A surge block will be used to surge the water in and out of the screen and sand pack. Sediment brought into the well will then be manually bailed. Development using this method will continue until tips well produces sediment-free water or until no further improvement is observable. After development, each well will be allowed to recharge for approximately 24 hours prior to sampling. Any liquids removed from the wells during their development will be stored in DOT-approved 17E drums. The drums will be left at the site until laboratory analytical results are known. At that time, the drums will be properly disposed of by Darpetrol. Groundwater Sampling .� Prior to sampling, each well will be checked for free-phase hydrocarbons. Wells with ons will not be sampled; however. detected free-phase Erre-phase hydrocarb hydrocarbons will be hailed from the well. The hydrocarbon thickness and volume removed will be recorded. Each well will be purged of stagnant water prior to collection of a sample. Normal field measurements, including pH, conductivity, and water temperature, will be periodically recorded during the purging process. A sample will be collected when these parameters stabilize to within 10 percent of each other, ^� provided a minimum of four well-casing volumes of water has been removed. If the well is evacuated before four well volumes are removed, the sample will be taken when the water level in the well recovers to approximately 80% of its initial water level. The samples will be collected with a clean bailer and transferred to the appropriate laboratory-supplied bottles. Samples will be labeled, logged on chain-of- custody fours, and placed in a chilled ice chest for transport to a state-certified laboratory for analysis.