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NOV C-005-95 -COMMENTS. SUPPLEMENTAL INFORMATION AND REQUEST FOR VACATION OF NOV, GENERAL COMMENTS The general area around Colowyo and specifically associated with the West Pit Pond area are typical examples of areas found throughout northwest Colorado exhibiting landslides and other such natural surficial failures. Such landslide features are a natural geologic erosional process and are often caused by shallow, perched water zones that saturate outcropping shales, sandstones, coal seams and other debris. When conditions are just right and the material is sufficiently saturated, landslides and slip failures can unexpectedly occur in unpredictable areas. Colowyo has operated in the region for 18+ years, both as a mine operator and an operator of extensive ranch properties (50,000 + acresl. During that time every drainage we conduct operations in within the Danforth Hills has experienced natural landslides and hillside failures. Specific locations of such hillside failures are impossible to predict as they simply occur without advance warning in response to the site specific moisture conditions occurring in the underlying strata. Such is the case with the slide area associated with the West Pit Pond. Whil__~_do not intend to discount the importance of the slide with respect to issues. of pond integrity the occurrence of this slide area is in reality simply just another slide area! In a historical perspective, dealing with landslides is not completely unknown at Colowyo. The Division will recall that on June 5, 1985 Colowyo submitted a TR request to modify a segment of the paved haulroad due to the occurrence of a similar debris slide caused by abnormal perched groundwater conditions. The abnormal groundwater conditions resulted from the above average precipitation occurring during 1984 and 1985. What is important to note is the precedent set by the Division and Colowyo working together to repair the haulroad ~~lie. conducting maintenance) without the need for unnecessary enforcement actions on the part of the Division. ~~kl IIJLI Called ua I Ui~iICA iLkSf ~~f-3UrP.(~s -!Fi*. ~N The attached information and photographs support our contention that this latest l~"~~ ~ landslide event was also a naturally occurring geologic event. We believe the slide occurred j!'t hu~ not as a result of negligence on the part of Colowyo but rather on unpredictable and ,, ,!'{ uncontrollable natural forces. To confirm this we had a CTL/Thompson Inc, representative inspect the site to 1) determine if the West Pit pond was in jeopardy and 2) determine the probable cause of the slide. They concurred that the pond does not appear in to be in UI'+~ jeopardy. They further concurred that the likely cause of the slide resulted from the influence rr,-r•+ z k~ of shallow, perched groundwater very similar in source to the springs flowing from the hillside '~ y' `~} located immediately to the east and also flowing from the West Pit Fill subdrain laterals. A copy of the CTL/Thompson report would be available to the Division if so desired. Colowyo believes that, just as the 1985 haul road slide did not warrant the issuance } `"P-~iof a NOV, this slide area does not warrant an NOV. When the topsoil stockpile was o1~'I' ~ constructed (fall, 1993) using photographs we will show it was clearly located and placed on ~rV~~~. . ' ~ a stable surface area. We will also show why the instability of the topsoil stockpile one and ~' ~ one-half years after construction could not have been predicted and was not a result of any } ~OP,,;, ~, negligence on the part of Colowyo. ' 1