Old room and pillar workings extend under Hometown where the strata roll to the horizontal (depth = 1,750 ft, 533 m) and where additional protection in the form of river-run sand fill is placed hydraulically through boreholes. The extraction ratio in this area is estimated to be about 40%. Once in place, the fill is grouted for additional strength. Laboratory test data from 4-in. (10.2 cm) diameter samples, 4 in. (10.2 cm) long (not grouted) are given in Table 7.7. Estimate the hydraulic conductivity of the fill(in./h).

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Table 7.7 Fill test data Time (min) Head (in.) (cm) 1.90 4.22 114 0.0 7.22 36.0 30.0 24.0 61.0 18.0 45.3 12.0 91.4 76.2 30.5 Note The standpipe inside diameter is 0.5 in. (1.27 cm).