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,SETif BY~ 7-21-95 9~48AM 0 S M-~ 303 832 8106:# 4/ 7 .. . „• - - ~ 2 - 1lElHOiDO~OLiY - The Tatum house is located approxiaately 350 feet beyond the mina varkings of north 1 section. The Holland-Gaddy and aianiawski formulas were used to estimate the stability of pillars for these '. . workings using cosputer wftvare included in the Surface .. Deforaation Prediction Systrm (sDPS) nodal. salaty factors of 2.2 and 4.7 wore determined. (See attached computer output). The laboratory coal strength of 3450 psi vas reduaad by zs percent to account for the atrsngth reduction due to flooding • as suggested by several authors. Tha roof and Yloor are stronger than coal pillars at this~aite; tAerelore, iailurr of roof. and ficor vas not analyzed. COIOIBai'FB OF CaitL GBiITT RBPOR'P ~ `. This investigation determined that the•actual extraction ratio - vas 34'parevnt and that no subsidence would occur beoauce of an ~~ adequate salaty !actor o! pillars. •• Gerity arbitrarily used an sXtraetion ratio of 9o percent ie the ~ ~ ' ' sDPS model to predict subsidence near the Tatum house; therefore ;.. ~. these Yesults are erroneous. The BOPS aodel viii net run to et•subsidene~ unless the extraction ratio is 75 percent or •, greater. ";. _ (r~:~ >> . . OWOfaRY 1~ OpIPCLOBION ~ ' t The pillars in the workings of north 1•section near t]se Tatum , house have a salaty factor o! 1.2 using the rioiland-Gaddy formula;, :. and 4.7 using the eleAiavski formula. For stable pillars, the ' Holland-Gaddy method requires a safety !actor of 2.0; the 8ieniawaki method requires a 1.75 safety factor. 8acause the pillars in the north 1 section near the Tatum house fall within tt-e saf®ty guidelines of both formulas; three pillars are conaidsred to be stable. Railroad tracks located above the mine workings of north i. - ' section (see nap) are active and haws not experianaed any subeidonaa maintenanar probleas Iinco 1990. This information was provided to 1[ike Rosenthal of OBl1 by the railroad company, which indicate that these giliars are stable. A concrete driveway vas built in 1980 in front o! the garage to the .south aide of the house and closer to the mine workings of north 1 section. The driveway does not exhibit any dnmage; which also indicate that these pillars are stable.