GENERAL39079

• Permit No: M1977211
• IBM Index Class Name: General Documents
• Doc Date: 6/25/2001
• From: US DEPT OF AGRICULTURE
• Media Type: D
• Archive: No

Pikeview t~uarry Environmental Assessment Page 28
and they have moderate permeability, low available water capacity, medium to rapid runoff,
and moderate hazard of water erosion.
3.2.3 Hydrology '
The Pikeview Quarry is located within a small drainage that starts northwest of the '
quarry, on National Forest land. This unnamed drainage originates at approximately 8,360
feet and is a tributary to Douglas Creek which joins Monument Creek to the east of ,
Interstate 25 about one mile south of Garden of the Gods Road. The stream flows in this
drainage aze t}Pically small, less than 0.5 cfs, and most of the flow disappears into the
ground west of the quarry permit boundary, except during higher flows associated with
snowmelt runoff and rainstorm events. The stream then reappeazs at a small spring located ,
within the quarry above Collection Basin #2. The path it takes underground is unknown,
but no evidence of it has ever been found in drilling or mining, suggesting that it must be
quite deep +ind probably follows fault lines and joints.
Near'the eastern boundary of the quarry the creek flows into a sediment collection
basin (Collection Basin #4) and is then released into a riprap-lined channel that extends for '
about 50 feet downstream to the quarry property boundary. From the quarry boundary
downstreant to Allegheny Drive (about 600 to 700 feet), the stream channel has become
deeply incised as a result of channel degradation caused primarily by storm event runoff ,
from the quarry. The amount of stream channel degradation through this reach varies from
about 5 feet to more than 20 feet. This channel degradation process is continuing as

evidenced by ongoing sloughing of the channel banks. During the field inspections it was '
evident that the sediment retention facilities located within the quarry function quite
effectively and very little sediment is leaving the site.
Above where the stream crosses Allegheny Drive, a second channel has been
constructed to convey a portion of the flow during storm events to a small sediment
retention basin located on the west side of Allegheny Drive to the south of the main stream ,
channel. During normal flow conditions, the creek flows in the constructed channel,
bypasses the sediment basin and follows Allegheny to the north where it joins the historiclrl
channel and flows underneath Allegheny Drive through a concrete box culvert. During ,
storm events, water flowing into the sediment basin is conveyed under Allegheny Drive
through a corrugated steel culvert into a channel that joins the main channel approximately
400 feet to the east of Allegheny Drive.
The section of the drainage below the box culvert under Allegheny Drive appears to be
relatively stable with a healthy riparian community downstream to where it receives storm
flows from the small sediment basin on the west side of Allegheny Drive. From this point
down stream for about 0.3 mile, the channel again becomes severely incised due to the
erosive force of clean storm event flows originating primarily from within the quarry. ,
Channel degradation throughout this reach is ongoing as indicated by active sloughing of
vegetation and stream banks into the channel. In some azeas the channel has become incised
by 20 to 30 feet below the elevation of the natural channel, resulting in the loss of much of ,
the riparian community. At the lower end of this 0.3 mile reach, the drainage flows into a
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