_INSPECTION - C1994082 ‎(41)‎

• Permit No: C1994082
• IBM Index Class Name: INSPECTION
• Doc Name: Inspection Report
• Inspection Date: 7/15/2009
• Email Name: DTM
• Media Type: D
• Archive: No

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III. COMMENTS-COMPLIANCE
Below are comments on the inspection. The comments include discussion of observations made during the
inspection. Comments also describe any enforcement actions taken during the inspection and the facts or
evidence supporting the enforcement action.
steep tributary that enters the valley drainage from the east. It is a relatively stable TRM lined
channel, although vegetation along much of the channel is mostly weedy annuals. (Photo#521).
Vegetation cover is dominated by annual weedy species on the hillslopes in the upper YPM-19
watershed, with a high density of rills (Photo #520). Reseeding with contour drilling or tillage
operations is warranted in the small YPM-19 upper watershed area, due to the poor initial
establishment and extent of rill erosion. This would be considered erosion repair
maintenance. The primary cause of the rill erosion appears to be poor initial establishment
of seeded vegetation, and not improper grading or drainage design/installation. On the
hillslope west of the YPM 1-3 channel, there is a circular feature 30-40 feet in diameter, visible
in the left upper quadrant of Photo #521. This is the location of a"sinkhole"type failure, which
was backfilled a couple years previously. There has been some recent settling of the remedial
backfill, evidenced by minor settling cracks around the perimeter. The settling does not appear
to be sufficient to warrant remedial measures at present, but does warrant continued monitoring.
YPM 6-1 Drainage
YPM 6-1 is a continuation of the main valley drainage downstream of the YPM-19 confluence.
It extends down to an undisturbed native aspen stand; the drainage downstream of YPM-19 runs
through the aspen stand for several hundred feet, and has been lined with TRM to prevent erosion
of the undisturbed channel reach. YPM 6-1 includes both TRM and riprapped segments. During
the SL-2 inspection on 7/16/09, numerous maintenance issues were noted along the channel.
Problems included holes along the upper TRM segment with associated scour beneath the TRM
liner in a few locations, inadequate riprap placement along the channel side-slopes in some
sections (Photo#527 and #528), and minor slumping and rilling parallel to the channel along
some segments (Photo #524). A dozer was grading a steep hillslope northeast of of the lower
segment of YPM 6-1 during the inspection on 7/16 (visible in background of Photos #525, 526,
and 527). On a prior inspection, it had been noted that the slope had not been topsoiled, that the
slope was poorly vegetated, and that the slope included a fairly pronounced convexity. The July
dozer work reduced the convexity to more closely blend with adjacent terrain and reduce erosion
potential, and topsoil was spread over the slope.
The drainage was re-inspected on 8/12/09. Grading and repairs had been conducted along the
entire YPM 6-1 segment; riprap had been properly installed to extend up channel sideslopes,
areas of bank slumping and rilling had been properly graded, and the steep valley sideslope
grading/topsoiling project had been completed and re-disturbed areas had been seeded. Photos
#630 and#635 through#638 show the channel and valley sideslope areas from various vantage
points. The valley sideslope was measured at 46%through the steepest segment, which is
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