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<br />1'~//1~//»~~ <br />~ " N III IIII IIIIIIIIIIII <br /> ~cconer <br />2 <br />9 <br />, <br />1990 <br /> C <br />\~\~~ <br />( <br />! <br />l <br />Mr. Jerry L. Kidci <br />U. S. Department of the Interior ~; : , ~ ~ 19ym <br />Bureau of Land Management <br />455 Emerson Street Nlfn@tl Ld~ftl <br />Craig, Colorado 81625 RQCI8R12t10~ UIVISIOII <br />Subject: Comprehensive Montoring Plan for Commercial-Scale <br />Solution Mining of Nahcolite - Update <br />Dear Mr. Kidd: <br />Enclosed please find updated monitoring plan for the NaTec <br />Minerals, Inc. nahcolite solution mine. Please replace the <br />monitoring plan delivered to your office on October 15, 1990 <br />with this plan. The new plan changes the format, with the <br />monitoring plan first followed by a summary of EPA and BLM <br />stipulations/requirements at the end of the document. Per my <br />discussion with Mr. Ralph Costa of your staff, subsidence <br />monitoring monuments have been established and a location map <br />(Plate 4, Map 4) has been developed illustrating relation to <br />the solution mining wells. The revised subsidence monitoring <br />plan should address concern in paragraph 1 of Mr. Ken Smith's <br />letter dated October 26, 1990. <br />` In regard to mapping cavities, the monitoring plan presents <br />three methods to determine and develop accurate surveys or maps <br />of cavities. Daily calculation of cavity volume, periodic use <br />of leaching simulation model and periodic cavity surveying with <br />sonar caliper tool are practical, commercially available <br />techniques utilized in the solution mining industry. NaTec <br />will meet with your staff to present details and technological <br />methodologies for mapping cavities if you feel a need. 43 CFR <br />3592.2 requires accurate surveys, not "actual surveys" <br />referenced in Mr. Ken Smith's letter dated October 26, 1990. <br />NaTec nor their mining consultants, are not aware of. methods to <br />"actually" .survey solutiOA mina caviti4~ in-situ. 43 CFR <br />3592.2 states that vertical projections and. cross sections --• <br />shall accompany plan view (when require!! by the authorized <br />officer) , this statement infers cavity shape and size will be ` <br />"projected". NaTec plans to use the best,. commercially <br />available methods to accurately map the cavities and that is <br />what is presented in the monitoring pkan. It there is a <br />practical, commercially available nlternativa which is used in <br />the solution mining industry pleaso advise; we also will <br />co~.inue to search for new developments in this area. <br />NQ~e Mln~nb Inc. <br />201 Wesl Third Street <br />P.O. Drawer T2 <br />Rifle, Colorado 61650 <br />303 625-7544 <br />Fax 303 625-3036 <br />