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time. I made a couple attempts to repair with bentonite but this fix did not <br />last. I subsequently dug out the riser to expose the defective gate. My <br />concern is that if the structure is left "as is ", a gully headcut will develop <br />(since the defect is at least two feet below sediment level in the pond), and a <br />gully will eventually migrate upstream through the pond and up the <br />ephemeral channel. <br />2) A second concern with the pond is that the open channel emergency <br />spillway located on the north end of the pond embankment is fractions of an <br />inch higher in elevation than the top of the embankment at the south end <br />(verified by laser survey). So, if the riser defect were repaired, and at some <br />point the primary discharge culvert became clogged, impounded water could <br />potentially spill out over the embankment at the south end, causing <br />significant erosion of the embankment. <br />The basic plan Paul and I had in mind was to seal off the defective gated <br />dewatering orifice, reduce the height of the riser pipe (or cut a large "V" <br />notch in the riser a couple feet or so above current sediment level), reduce <br />the elevation of the open channel spillway by 18" or so (ensure that primary <br />riser outlet remains at least a food lower than open channel), and riprap the <br />lowered open channel spillway. I think I have a diagram I made of the <br />various critical elevations (current open channel spillway invert, top of <br />primary riser pipe, etc.). <br />When I heard we might be getting additional funds, I thought we might want <br />to consider eliminating the pond altogether, and reconnecting the drainage <br />channel along the original channel alignment (based on extent of vegetation <br />cover, we have made the demonstration to show that a sedimentation pond is <br />no longer required to treat mine site runoff). I now think it would be better <br />to undertake the basic repairs originally envisioned, which would allow for <br />retention of a pond that would hold a small pool of water during at least <br />some periods of the year, and would benefit wildlife in the immediate area. <br />Pond removal was not anticipated in the originally approved reclamation <br />plan. I think it would be a better use of remaining funds to address erosion <br />concerns in various locations. <br />Erosion Concerns <br />Erosional features of varying severity, and presenting varying degrees of <br />challenge with respect to access and remediation have developed on the site. <br />