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j Attachment A to Kennedy/Jenks/Chilton's Kennedy/Jenks/Chilton letter to Mr. Charles Whitworth dated 14 July 1989 Page 3 1 1 and mixed. The grout was then poured through the center of the augers while the augers were at the bottom of the boring. The augers were filled to capacity then withdrawn at one to two-foot intervals, allowing the grout to flow out of the augers and into the boring. This process was repeated until the boring was filled to the ground surface. MONITORING WELL INSTALLATION AND CONSTRUCTION Four borings were completed as monitoring wells (MW-1, MW-2, MW-3, and MW-4) . n Each well was constructed using two-inch outside diameter Schedule 40 PVC well casing material . The well screen and casing were steam cleaned before installation After steam cleaning was completed, the well screen and casing were immediately lowered down the center of the eight-inch augers, the bottom of which was approximately 25 feet below the ground surface in all monitoring wells. Once the casing was at the bottom of the augers, an artificial filter pack was placed between the PVC well casing and the inside annulus of the augers. The artificial filter pack for each well consisted of Monterey No. 1C sand extending approximately one-foot above the top of the well screen. The artificial filter pack sand was emplaced while the PVC well casing was inside of the eight-inch augers. The artificial filter pack sand was allowed to free-fall through the center of the auger between the PVC well casing and the inner annulus of the augers until approximately three feet of sand was inside E of the augers between the PVC casing and the inner annulus of the augers. The auger was then withdrawn at approximately one- to two-foot intervals; this allowed the artificial filter pack sand to flow out of the auger and between the well screen and the boring wall . This process was repeated until the artificial filter pack extended approximately one-foot above the top of the well screen. A one-foot thick bentonite pellet seal consisting of 1/4-inch long bentonite pellets was installed on top of the artificial filter pack. The pellets were moistened with potable water (approximately three gallons) , obtained from a nearby water source, and allowed to hydrate approximately 15 minutes. } A cement/bentonite grout was then emplaced on top of the bentonite pellet seal and extended flush with the original ground surface (grade) . The grout mixture and procedures for the monitoring wells were similar to that described above for the soil borings. However, because the formation soils consisted primarily of firm, lean clays which allowed the boring to stay open, the • augers were withdrawn from the boring before the grout was emplaced. Therefore, the augers were extracted and the grout was immediately emplaced on top of the bentonite pellet seal . r