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7 <br />t , <br />C <br />J <br />BACKGROUND <br />•^_ <br />Basin Resources Inc. mined out maxwell seam near 0 through Section 1 <br />North of Golden Eagle Mine using room and pillar mining th no retreat mining <br />( see map 1). The mining height in this area averages 6 feet and depth 640 feet. The pillazs <br />are 80 feet X 80 feet and all entries 18 feet wide. This section was stopped due to water <br />trouble and sealed in 1990. The roof and floor in this area consist of interlaminated <br />sandstone and siltstone. <br />METHODOLOGY <br />Holland-Gaddy and Bieniawsld formulas to estimate the stability of pillars at Section 1 North <br />which are 350 feet from Tatum House are used. The calculated safety factors of 2.0 and 4.2 <br />aze found using Holland-Gaddy and Bieniawsld formulas respectively. For stable pillazs <br />Holland-Gaddy require a safety factor of 2.0 and Bieniawsld 1.75. Therefore, pillazs in <br />Section 1 North near Tatum House are stable using Holland-Gaddy and Bieniawsld approach. <br />The pillar strength used to calculate the safety factor is reduced by 30 percent to account for <br />strength reduction due to flooding which is given by several authors (1,2). The roof and <br />floor are stronger than coal pillars, as such these are not considered. <br />COMMENTS ON CARL GERTI'Y REPORT <br />Carl Gerity incorrectly applied_SDPS model (see page 9) where extraction ratio of 90 <br />percent-is used when the actual extraction ratio is 36 percent. The SDPS model is not <br />recommended to be used for subsidence prediction in room and pillar mining when the <br />extraction ratio is less than 75 percent and is clearly stated in the manual. <br />CONCLUSION <br />Based on the information provided, site visit, data analysis, and going through several <br />referenceis'e damage to Tatum House is not caused by underground mining of maxwell <br />seam thr h Section 1 North at Golden Eagle Mine. <br />DRAFT <br />