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III. COMMENTS -COMPLIANCE <br />Below are comments on the inspection. The comments include discussion of observations made <br />during the inspection. Comments also describe any enforcement actions taken during the inspection <br />and the facts or evidence supporting the enforcement action. <br />E to D (006-S7 confluence down to 006-E1 confluence) <br />This 500' channel segment extends from the 006-S1 confluence down to the 006-E1 confluence. <br />Design profile depicts an average 9% grade, Design specification for slope gradients up to 7% is a <br />vegetated "V" channel, 2.4' deep and 14.4' wide. Design for segments with grade between 8% and 15% <br />is trapezoid channel, 2' bottom width, 0.9' deep, 7.4' wide, with 6" D50 riprap. <br />• There are several hillslope gullies that enter the channel from the east, near the <br />northwest corner of the fenced plot, that will need to be repaired. <br />• The channel appears to be in reasonable conformance with approved gradient (measured at <br />10%) and the trapezoidal channel is wider and deeper than required, properly shaped and <br />riprapped. The channel is stable along most of the reach, with the only exception being some <br />minor scour at the lower end just above the confluence with 006-E1, that will need to be <br />monitored. <br />D to C (006-E1 confluence down to 006-NE2 confluence) <br />This 1800'+/-segment runs from the 006-Et confluence down to the NE-2 confluence. A strip of <br />undisturbed land runs along the right (NE) side of the channel through the segment. Design profile <br />shows alternating segments of steeper and flatter grade, ranging between 3.3% and 12.8%. Design <br />specifications are for a trapezoid channel, with dimensions and liner varying depending on grade. <br />Design for grades up to 5% is 5' bottom width, 2' depth, 17' top width, vegetated channel. For grades <br />from 6% to 14%, design is 5' bottom width, 0.9' depth, 10.4' top width, 6" D50 riprap. For grades 15% to <br />20%, design is 5' bottom width, 0.8' depth, 9.8' top width, 9" D50 riprap. <br />• Initial 150'+l_ section is low gradient, measured at 2%. The channel is trapezoidal, with <br />dimensions approximating design configuration. The substrate is gravelly overburden, not yet <br />stabilized by vegetation, minor scour along the segment. Vegetation establishment may not be <br />likely until upland portions of the watershed are stabilized. Monitoring of the segment is <br />warranted to determine if further measures are warranted. <br />Below the low gradient segment described above, there is a steep segment approximately 200' <br />+f- in length, measured at 16% grade (somewhat steeper than depicted on the design profile, <br />but within the design grade limits of Figure 20-1.1). There was side-cutting along both sides of <br />the channel through this section. Erosion along the right bank has resulted in bank material <br />slumping into the channel, and vertical cut banks up to 10' high along one 40' channel segment <br />(Digital Image 2582). Maintenance grading and riprap placement as necessary to protect <br />the banks and prevent further erosion and sloughage (right bank), and flow outside of <br />riprap (left bank) is warranted. <br />• Downstream from the riprapped segment, there is a several hundred foot lower gradient <br />segment (measured at 6%), that apparently was not riprapped. The segment extends down to <br />the 006-NE2 confluence. The channel was severely eroded (gutlied 2' to 4' deep), and the <br />entire segment will need to be regraded to design configuration and riprapped (Digital <br />Image 2583). <br />• There is a long gully along the toe of the reclaimed slope south of the 006 Channel, and <br />parallel to it, near the NE-2 confluence that will also need to be repaired. <br />8 <br />