1995-09-22_GENERAL DOCUMENTS - C1981017

• Permit No: C1981017
• IBM Index Class Name: GENERAL DOCUMENTS
• Doc Date: 9/22/1995
• Doc Name: Bid Documents ‎(IMP)‎
• Permit Index Doc Type: General Correspondence
• Media Type: D
• Archive: No

AUG 2Djjc 9
ATTACHMENT TO CHANGE ORDER MINERALS GEpL�G Y UP
Purchase Order No. PD PKA 95000000009
Justification
Dutch Creek flows through an approximately 13 feet wide by four
feet tall concrete channel for approximately 300 feet above the
confluence with Coal Creek. Mid-Continent Resources had placed a
9 feet diameter steel culvert into the concrete channel in 1993 as
a repair measure. On Tuesday, June 6, 1995, it was observed that
the flow of Dutch Creek above the confluence with Coal Creek was
increasing due to snow melt run off. The increased velocity of
Dutch Creek resulted in an increase of bedload transport. Rock to
a diameter of over three feet were observed to be transported down
the concrete channel.
As a result of the flow becoming constricted as it transitioned
from the 13 feet wide concrete channel to the 9 feet diameter
channel, the bedload fell out and accumulated at the entrance to
the channel. There were two results of this occurrence: The
effective depth of the concrete channel was reduced by up to two
feet; a standing wave developed within the concrete channel. The
wave and accumulated rock had been observed to extend the length of
the concrete channel. The potential consequence of these results
was that a possibility of Dutch Creek overflowing the concrete
channel and diverting into either the facilities area or the Old
Refuse Pile existed. Loss of the flume supports was a subsidiary
concern as a result of an overtop.
It was determined that action to minimize the threat of an overtop
was warranted. On June 7, the Division directed Bogue Construction
to sweep the accumulated rock through the steel culvert using the
416 backhoe previously mobilized to the site. This equipment was
not sufficient in size to maintain the channel . Therefore, it was
determined that a John Deere 690 tracked backhoe would be mobilized
to the site. An operating price of $80.00 per hour for the
equipment was agreed upon ($28 . 00 per hour for standby time) . This
equipment was mobilized to the site on June 9 , 1995.
Due to the continued high flows, on June 12 it was agreed that an
operator would be present at the site from approximately 2 :00 pm
until flows receded at approximately midnight. On June 22, it was
agreed that an operator would visit the site only to clear the
channel of rock in the early evening and depart the site. This was
done as the flows had diminished and then remained fairly constant.
Also on June 8, it was determined to increase the effective depth
of the concrete channel by placing Type 4 (Jersey) barriers along
the top of the channel. Subsequently, 310 linear feet of barriers
were placed in this location. A rental price of $6. 00 per linear