_INSPECTION - C1981019 ‎(55)‎

• Permit No: C1981019
• IBM Index Class Name: INSPECTION
• Doc Name: Inspection Report
• Inspection Date: 8/13/2008
• Email Name: JRS
• Media Type: D
• Archive: No

IV. ENFORCEMENT ACTIONS
Colowyo C-1981-019
13 August 2008
Page 2/5
storm event for the Prospect Pond is 1 .8 inches and the 25-year, 24 hour storm event is
2.3 inches. The storm event that hit the Colowyo Mine and the Prospect watershed
was less than a 10-year, 24-hour storm event.
The water the flowed into the pond contained a large amount of sediment and
larger rock which has accumulated in most of the pond. Although the pond was
cleaned last fall (approximately 8,000 yards of material was removed) the pond is
now full of sediment again. This includes a large amount of cobble material that has
been deposited at the inlet of the pond.
The inslope of the pond embankment is covered with mud and some debris from the
water that flowed into the pond. The outslope of the pond contains a lot of debris as
well, from the water that topped over the pond. There is also sediment and debris
that has been deposited on the opposite side of Colorado Highway 13. In
information provided by Colowyo, there was also a CDOT snowplow on site moving
mud/water from the road as it flowed out of the emergency spillway and over the
embankment.
The pond embankment appeared to remain stable at the time of the inspection and
no rilling or nick points were noted. The emergency spillway is a grouted, riprapped
channel, which probably helped to stabilize the spillway and embankment as the
water discharged. The trash rack, weep holes and discharge pipe were all cleaned
at the time of the inspection.
In addition to the pond, the drainage to the Prospect Pond was inspected. First, we
walked from the bottom of the drainage at the pond inlet. This portion of the
drainage appeared to be in good condition. Most of this portion of the drainage is
through the natural sandstone and the bottom of the drainage is also natural
sandstone. The high water mark was approximately 10-12 feet high in most areas of
the drainage, as evidenced by the bent-over grass and debris.
The upper portion of the drainage was then walked, beginning with the Prospect
Ditch. He Prospect Ditch is only partially complete. The upper portion of the ditch
has been completed and riprapped while the lower portion of the ditch has not
been riprapped. This ditch has been a concern of the Division for some time, with
questions regarding the ditch being asked in the Permit Renewal 05 adequacy
review. The Prospect Ditch shows signs of erosion in the channel bottom and some
side-cutting has occurred on the channel as well. This erosion helps to contribute
suspended material to the Prospect pond.
Farther down the drainage two large gullies were observed, one on each side of the
Prospect Ditch. The gully on the south side of the ditch went from the top of the slope
all the way to the boundary with the undisturbed drainage. This gully varied in width
and depth from approximately five feet deep and five feet wide to what appeared