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. Kenned�IJenks�Chil� Mr. Tom Terrill Reynolds and Brown 26 January 1987 Page Four to 11. 5 feet, and drilling continued until two organic vapor- free samples (as determined by heaspace monitoring) were col- lected. The drilling for Boring B3 encountered a sandy, saturated, interval between 16 and 20 feet below ground surface. This layer appeared more permeable than the overlying silty mate- rial. Because of this, Boring MW1, which was completed as a groundwater monitor well , was also drilled to a depth 20 feet so that the well screen intersected this permeable zone. MONITOR WELL CONSTRUCTION, DEVELOPMENT, AND SAMPLING The boring north of the underground storage tanks was completed as a groundwater monitor well. This location was selected to collect a groundwater sample . downgradient of the storage tanks. Available information from two groundwater monitoring systems in southern Tracy indicates that the hydrologic gradient is north Lto northwest in the area. The well consisted of 4-inch diameter PVC well screen with 0. 01 inch machine-cut slots that extended to the highest expected Llevel of groundwater. The upper part of the well consisted of four-inch diameter Schedule 40 PVC pipe. All well materials were steam cleaned prior to use and connected with flush threaded connections without PVC cement to minimize ``---contamination of samples collected from the monitoring well . The bottom one--foot of the boring and the annular wellspace was filled with gravel pack two feet above the well screen. The annular space immediately above the gravel pack was filled with bentonite pellets that were soaked with Tracy municipal tap L water after emplacement to ensure a watertight seal. The upper portion of annular well space was filled with cement-bentonite grout. The well extended approximately two feet above ground and protected by a six-inch diameter locking steel casing. The groundwater monitoring well was developed to remove fine L sediment from the vicinity of the well. Well development allows free inflow of groundwater so. that a representative sample can be collected. Well development was performed on 7 January 1987 using a stainless steel submersible pump. Water from well development was periodically monitored for tem- perature, pH and specific conductivity. The well was developed L L