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ATTACHMENT TO CHANGE ORDER <br />Purchase Order No. PD PKA 95000000009 <br />Justification <br />Dutch Creek flows through an approximately 13 feet wide by four <br />feet tall concrete channel for approximately 300 feet above the <br />confluence with Coal Creek. Mid - Continent Resources had placed a <br />9 feet diameter steel culvert into the concrete channel in 1993 as <br />a repair measure. On Tuesday, June 6, 1995, it was observed that <br />the flow of Dutch Creek above the confluence with Coal Creek was <br />increasing due to snow melt run off. The increased velocity of <br />Dutch Creek resulted in an increase of bedload transport. Rock to <br />a diameter of over three feet were observed to be transported down <br />the concrete channel. <br />As a result of the flow becoming constricted as it transitioned <br />from the 13 feet wide concrete channel to the 9 feet diameter <br />channel, the bedload fell out and accumulated at the entrance to <br />the channel. There were two results of this occurrence: The <br />effective depth of the concrete channel was reduced by up to two <br />feet; a standing wave developed within the concrete channel. The <br />wave and accumulated rock had been observed to extend the length of <br />the concrete channel. The potential consequence of these results <br />was that a possibility of Dutch Creek overflowing the concrete <br />channel and diverting into either the facilities area or the Old <br />Refuse Pile existed. Loss of the flume supports was a subsidiary <br />concern as a result of an overtop. <br />It was determined that action to minimize the threat of an overtop <br />was warranted. On June 7, the Division directed Bogue Construction <br />to sweep the accumulated rock through the steel culvert using the <br />416 backhoe previously mobilized to the site. This equipment was <br />not sufficient in size to maintain the channel. Therefore, it was <br />determined that a John Deere 690 tracked backhoe would be mobilized <br />to the site. An operating price of $80.00 per hour for the <br />equipment was agreed upon ($28.00 per hour for standby time). This <br />equipment was mobilized to the site on June 9, 1995. <br />Due to the continued high flows, on June 12 it was agreed that an <br />operator would be present at the site from approximately 2:00 pm <br />until flows receded at approximately midnight. On June 22, it was <br />agreed that an operator would visit the site only to clear the <br />channel of rock in the early evening and depart the site. This was <br />done as the flows had diminished and then remained fairly constant. <br />Also on June 8, it was determined to increase the effective depth <br />of the concrete channel by placing Type 4 (Jersey) barriers along <br />the top of the channel. Subsequently, 310 linear feet of barriers <br />were placed in this location. A rental price of $6.00 per linear <br />