GENERAL41251

• Permit No: C1980001
• IBM Index Class Name: General Documents
• Doc Date: 5/28/1992
• Doc Name: 1992 EROSION INVENTORY REPORT
• Media Type: D
• Archive: No

EDNA MINE--1992 EROSION INVENTORY REPORT
• cobble in the bottom of the channel is approximately 2 by 3 inches; the channel
appears to be adequately armored. The banks of the channel slope away from
the bottom between 1v:1.Oh and 1v:12.Oh. The channel appears to be reasonably
stable at and above the cross-section, with no visible signs of excessive ongoing
erosion.
In the reach between Cross-Sections 4 and 5, the potential exists for excessive
erosion in the future. This potential is created by the steep drop (40 degrees)
into the closed basin. However, since the amount of water carried in this
channel is relatively small and a significant portion of the regraded spoil
consists of large and medium sized rock, the potential for excessive erosion is
not immediate, and in fact may not manifest itself at all. Therefore, this area
requires close monitoring to assess actual erosion rates, but no corrective
measures are proposed at this time.
Cross-Section 5-This cross-section is located on unbonded land and lies below
the outlet from the closed basin that Feature 1 flows in to. This location was
surveyed to provide a frame of reference with which to evaluate the actual rate
of headcutting, if any, into the bonded reclaimed area. In the immediate
vicinity of this cross-section vegetation has not established in either the sides or
the bottom of the channel. The average size of rock cobble in the bottom of the
channel is approximately 6 by 6 inches; armoring has occurred in varying
• degrees. The banks of the channel slope away from the bottom between 1v:0.8h
and 1v:1.4h. The channel shows signs of active ongoing erosion. The potential
for excessive future erosion exists. No work is currently proposed in this area,
since it is no longer bonded.
Subarea 1 Erosion Condition Classification
South-of--Shop Subarea 1 was evaluated using the methods described in BLM
Technical Note No. 346. The erosion condition composite soil surface factor score
for this site is 10.5, which places it in the Stable erosion class. The tabulated
results for the 1992 survey are contained on Table 1.
Subarea 2 Erosion Condition Classification
South-of-Shop Subarea 2 was evaluated using the methods described in BLM
Technical Note No. 346. The erosion condition composite soil surface factor score
for this site is 20, which places it in the Stable erosion class. The tabulated results
for the 1992 survey are contained on Table 2.
• WRE May 27, 1992