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loy~s.3 <br />MEMORANDUM <br />TO: Kathy Welt <br />Mountain Coal Company <br />FROM: Wright Water Engineers, Inc. <br />C. Richazd Dunrud, P.E. <br />DATE: August 28, 1997 <br />RE: Results of Field Investigations on the North Face <br />of Jumbo Mountain (August 6, 1997) <br />The purpose of this memorandum is to sutnmarize my recent field investigation on the north U <br />face of Jumbo Ivfountain. I visited the azea of Jumbo Mountain above longwall Panels 3 and ? <br />9 on August 6, 1997. I was unable to start the field visit as planned on August 5 because rn <br />heavy rains made access impossible, even on four-wheel-drive all-terrain vehicles (ATVs). ~ <br />W <br />Access during August 6 was only possible by ATV because of continued rain. Z <br />Dave Nicewicz, surveyor for MCC, drove me azound on the back of afour-wheel-drive ATV Z <br />to both areas visited. This allowed me to cover 3 or 4 times the azea I could have otherwise W <br />covered. He also located our investigation sites relative to MCC survey control points, W <br />recounted dates the cracks were first observed, provided background information on water ~ <br />conditions relative to the last three years, and also helped with measurements and scale (see 3 <br />included video and still pictures of field sites for detail). ~ <br />2 <br />Panel 8 and 9 Cracks on Jumbo Mountain ~ <br />2 <br />The following observations were made during the visit to the north side of Jumbo Mountain, ~ <br />which, I believe, provide an important framework in which to evaluate the nature and extent I <br />of cracking: <br />Of the three yeazs that Dave had surveyed in the azea, he reported that this yeaz was <br />the wettest. Many of the seep azeas were more extensive and wetter than Dave had <br />ever seen them. Also, I estimate that there has been a three-fold increase in the <br />volume of tlow and azeal extent of the seeps observed when I visited these azeas <br />during USGS mapping in the late 1970s. WWE confirmed that water year 1997 has <br />been unusually wet. <br />2. Unconsolidated clays and silts of the Wasatch Formation locally occur in many of the <br />azeas visited (Dunrud 1989). These clays and silts. which likely range in thickness <br />from a few feet to many tens of feet, are involved in landslides throughout this area <br />and in many nearby areas including the Muddy Creek area. particularly durins <br />periods of increased saturation. <br />