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- -. <br /> <br />MEMORANDUM <br />TO: Kathy Welt <br />Mountain Coal Company <br />FROM: Wright Water Engineers,lnc. <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 />~o4Ss.3 - <br />The purpose of this memorandum is to summarize my recent field investigation on the north <br />face of Jumbo Mountain. I visited the area of Jumbo Mountain above longwall Panels 8 and <br />9 on August 6, 1997. I was unable to start the field visit as planned on August 5 because <br />heavy rains made access impossible, even on four-wheel-drive a[I-terrain vehicles (ATVs). <br />Access during August 6 was only possible by ATV because of continued rain. <br />Dave Nicewicz, surveyor for MCC, drove me azound on the back of afour-wheel-drive ATV <br />to both azeas visited. This allowed me to cover 3 or 4 times the area I could have otherwise <br />covered. He also Located our investigation sites relative to MCC survey control points, <br />recounted dates the cracks were ftrst observed, provided background information on water <br />conditions relative to the last three years, and also helped with measurements and scale (see <br />included video and still pictures of field sites for detail). <br />Panel 8 and 9 Cracks on Jumbo Mountain <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 <br />of cracking: <br />1. Of the three years that Dave had surveyed in the azea, he reported that this year 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 flow and areal extent of the seeps observed when I visited these azeas <br />during USGS mapping in the late 1970s. WWE confirmed that water yeaz i997 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, aze involved in landslides throughout this area <br />and in many nearby areas including the Muddy Creek area, particularly during <br />periods ofincreased saturation. <br />