SITE INFORMATION AND CORRESPONDENCE

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r t f Y � Mr. Dan Moe Page 2 December 9, 19$7 As the anticipated depth to water is 40 feet, a 4 inch diameter well will be re- quired in order to accommodate a 4 inch submersible pump. If possible, the well will be installed by the use of a 6 inch hollow stem auger drilling rig. However, the bottom of the well screen is expected to be at a depth of about 60 feet which may be about the depth limit of the larger diameter hollow stem augers. It may be beneficial to make a preliminary boring with a 3 3/4 inch hollow stem auger to find the depth to water and the presence of any underlying confining layer, and then drilling with the larger diameter hollow stem auger to install the well. The well casing and screen will be made from flush jointed schedule 40 P.V.C. pipe. The well will be completed with a clean silica sand pack around the well screen to a height of 3 feet above the top of the well screen. A one foot thick bentonite seal will be placed on the sand pack and the well annulus sealed to the surface with a 4% bentonite cement grout. As the area does have a large volume of truck traffic, some of the wells may be completed in a pavement level vault. A survey marker will be imbedded in the surface of the cement grout seal, and the relative elevation of each well will be determined. The wells will be developed by a combination of swabbing, air surging, and pumpage. Development will continue until the well discharge water is sediment free, or until a total of 2 hours of development time has elapsed. During well development, the pumping rate of each well will be determined. This pumping rate will then be used in designing the sampling program for each well. Following development, the wells will remain idle for a week prior to sampling. Prior to sampling, a standardized well sampling log will be prepared and used to record pertinent data collected dur- ing sampling. At the time of sampling, the wells will first be checked for the existence of a floating product layer by the use of a clear acrylic product bailer. If no product is found, then the depth to water will be measured and recorded. Using the depth to water measurement, the volume of water in the well and the required purge volume will be calculated and recorded. It is proposed to purge three (3) well casing storage volumes prior to collection of the water samples. The well will be purged with a 4 inch submersible pump. The pump will be thoroughly cleaned prior to use, and will also be cleaned after each well is purged. Well yield will control place- ment of the pump during purging. If the well yield is greater than the pump dis- charge rate, then the pump will be placed at the top of water column in the well. If the pump discharge rate is greater than the well yield, then the pump will be placed about mid-height in the well water column, such that, the water level in the well is drawn down to the pump intake. For low yield wells, it may be necessary to install a flow control valve on the pump discharge line. A record of the purging activities will be kept in the sampling log book. In the last moments of well purging, the pH, temperature, and conductivity of the water will be measured and recorded in the sampling log. Once the wells have been purged, the pump will be pulled from the well. The volume of water purged, the pump discharge rate, depth of pump setting, and the start and finish time of purging will be recorded in the sample log. Water samples will be collected by a point source sampling device as soon as practicable after purging. Samples will be stored in the appropriate container, and promptly chilled to 4 C. ' Water samples will be delivered to the laboratory within 24 hours after sample collection. The depth of sample collection,