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a r ' a •b r fa+/ V� j R� 3.0 FIELD METHODS 3.1 WELL DESTRUCTION Destruction of monitoring well RW-2 was performed by Spectrum Exploration, Inc. and IT, The well was drilled out to a depth of 30.0 feet using 12-inch outside diameter, hollow-stem augers, which contained a casing cf- tering device. White PUC casing scraps and a medium sand (well filter pack) were brought to the surface during drilling. A split-spoon sampler was driven from 29 feet below grade and confirmed that native material (a grey-brown mottled i # hard clay or silt) had been reached. a The apparent discrepancy between- constructed well depth.(30 feet) and the ;�. depth at which native material was confirmed (29 feet) exists because s' approximately one foot of material (pavement and subgrade) was removed from the site before well destruction. This means that the true well depth of 30 feet was equivalent to about 29 feet after both the pavement and subgrade had been removed. After the well was drilled out, it was sealed to a depth of 13 feet below grade by tremieing a cement-bentonite mixture in through a pipe inserted through the augers, frim the bottom of the hole up. The hole was not sealed above 13 feet because it lay within an area to be excavated to a depth of 14 feet the following day. The extra foot of grout was placed to allow for grout . infiltration and settlement. This procedure was performed in the presence of ' San Joaquin County Public Health Services Department personnel. ' When this area was excavated and sampled (February a), the excavator operator i ; reported encountering the cement plug near the bottom of the excavation, indicating that well MW-2 had been properly destroyed. Cuttings and sand produced during well destruction were placed with materials excavated from the fuel UST excavation for subsequent sampling and disposal. The-We.]_l-.Destruct'ion-.Perm it-is--shorn--in-App end ix-A: ------_- - - -- 3 +mA:ENG:9199/041591 t -