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Kenna;ryJenks Ch iiion <br /> Mr. Tom Terrill <br /> Reynolds and Brown <br /> 26 January 1987 <br /> Page Four <br /> 1 <br /> to 11. 5 feet, and drilling continued until two organic vapor- <br /> free samples ( as determined by heaspace monitoring ) were col- <br /> lected. <br /> The drilling for Boring B3 encountered a sandy, saturated , <br /> interval between 16 and 20 feet below ground surface . This <br /> layer appeared more permeable than the overlying silty mate- <br /> rial . Because of this , Boring 14Wl , which was completed as a <br /> groundwater monitor well , was also drilled to a. depth 20 feet so k <br /> that the well screen intersected this permeable zone. <br /> MONITOR WELL CONSTRUCTION, DEVELOPMENT, AND SAMPLING <br /> The boring north .of the underground storage tanks was completed <br /> as a groundwater monitor well . This location was selected to <br /> collect a groundwater sample downgradient of the storage tanks. <br /> Available information from two groan water monitoring systems in <br /> southern Tracy indicates that the hydrologic gradient is north <br /> to northwest in the area. <br /> i <br /> i <br /> The well consisted of 4--inch diameter PVC well screen with 0. 01 <br /> inch machine--cut slots that extended to the highest expected <br /> level of groundwater. The upper part of the well consisted of <br /> four-inch diameter Schedule 40 PVC pipe. All well materials <br /> were steam cleaned prior to use and connected with flush <br /> threaded connections without PvC cement to minimize <br /> ' contamination of samples collected from the monitoring well . <br /> The bottom one-foot of the boring and the annular wellspace was <br /> filled with gravel pack two feet above the well screen. The <br /> annular space immediately above the gravel pack was -filled with <br /> bentonite pellets that were soaked with Tracy municipal tap <br /> water after emplacement to ensure a watertight seal . The upper <br /> portion of annular well space was filled with cement-bentonite <br /> grout. The well extended approximately two, feet above ground <br /> and protected by a six--inch diameter locking steel casing . <br /> The groundwater monitoring well was developed to remove fine <br /> sediment from the vicinity of the well . well development allows <br /> free inflow of groundwater so that a representative sample can <br /> be collected . well development was performed on 7 January 1987 <br /> using a stainless steel submersible pump. <br /> water from well development was periodically monitored for tem- <br /> perature , pH and specific conductivity. The well was developed � <br />