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S I n I I r)1 CUI 7~.Al u'i yu ~innli II i nr/.'A ~... v,..... ~~ III III III III IIII III <br />DEPARTMENT OF NATURAL RESOURCES 999 <br />D. Monte Pascoe, Executive Director <br />1111N1?.U LAND 1{ECLA119A'I'ION <br />423 Centennial Building, 1373Sherman Street' <br />Denver, Colorado 80203 Tel. (300) 839-3567 <br />September 9, 2980 David C. Shelton <br />Director <br />T0: Marion Dodson/Paul <br />FROM: Jim Pendleton <br />SUBJECT: Western S pe C 's Subsidence Control Program For the <br />Hawksnest Mine ~ '~ <br />I have reviewed the brief subsidence control plans submitted by Western <br />Slope Carbon for its Hawksnest Mine in Somerset, Colorado. I forward the <br />following comments for your consideration. <br />(1) The first component of the subsidence control plan, described in Section <br />~2.05.6(6)(a), is an inventory of existing structures and renewable resource <br />Lands. On page 98 WSC states that the only effected structures would be State <br />Highway 133 and the mines proposed intake shaft. However, WSC limits its <br />definition of effected to those areas overlying the "E" seam coal. The <br />rags require consideration of structures within the influence of the angle of <br />draw. WSC should clarify its statement appropriately. If additional structures <br />_are thereby affected, they w_'ll have to be included within the control plan. <br />A sixty degree angle of draw utilized by WSC in preparing Section ii (B) on page <br />51 of their application is acceptable for this determination of subsidence _ <br />influence at the ground surface. ~~ <br />(2)~~ WSC states on page 48 that it "has noted no renewable resource lands". <br />~I will have to depend upon your evaluation of that statement. Adequate infor- <br />mation is not included within the materials you forwarded to me with which to <br />evaluate its accuracy. <br />(3) ~A map, as required in Section 2.05.6(6)(a)(ii)(8), showing structures and <br />renewable resource lands must be included within the application. <br />~- <br />' (4)~~ WSC responds to the requirements of Section 2.05.6(6) by electing to submit <br />~a formal "subsidence control plan", as defined in Section 2.05.6(6)(f),~ WSC <br />`has monitoring results from approximately one year's observations which indicate <br />minor subsidence with immaterial damages have occurred to date. They propose <br />to supplement their existing monitoring monument system by the addition of <br />subsidence monitnrif~g monuments along State Highway 133 and to the north and <br />east of their proposed intake shaft. Additional points will be necessary along <br />the intermittent stream channel described as subject to possible subsidence <br />damage in Section ii (C) of their application. <br />' (5) The entire monitoring program will have to be surveyed quarterly and the <br />results of that survey reported to the Division at least semi-annually. <br />1 <br />~ (6 J A map showing all monitoring monuments and structures to be monitored will <br />have to be prepared and submitted as described in Section 2.05.6(G)(c)(ii). <br />In summary,~the above inadequacies are fairly minor in nature. The subsidence <br />control plan, prepared prior to the final regulation's promulgation, appears to <br />~~n1~7 .'r,~~ose to 'satisfying the i-ci}ili}~elfietits of t11e i:oloiado Fbi-iNahc:it tegulatdi(r <br />I . rr i <br />