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undisturbed segment of the valley up-gradient from the reclaimed area. On revised <br />Exhibit 20-2, a short designed channel segment (006-S1) is depicted, but the <br />landform is quite different than pre-mining (Exhibit 7-6 Drainage Basins), and does <br />not appear to blend into the adjacent terrain as the approved topography does. In <br />the revised topography, the reclaimed drainage segment is within a very broad, <br />Swale type feature with gentle side slopes. Please provide explanation and <br />justification for this departure from the approved plan, sufficient to demonstrate <br />compliance with applicable provisions of Rule 4.14.1, and 4.14.2, or amend the <br />Exhibit to conform to the original plan. <br />12. On both pre-mine topography and approved topography, there is a prominent valley <br />landform between 006-NE2 and 006-NE1. This valley landform is significantly <br />reduced on the revised topography. On the approved PMT map, the valley feature <br />extends approximately 1500 feet up from the 006 Gulch channel. On the revised <br />PMT map, the valley feature extends less than 400 feet up from the 006 Channel, <br />with uniform hill-slope above. Please provide explanation and justification for this <br />departure from the approved plan, sufficient to demonstrate compliance with <br />applicable provisions of Rule 4.14.1, and 4.14.2, or amend the Exhibit.to conform <br />to the original plan. <br />13. Cross-section S-5 crosses the 006 drainage some distance up-gradient from the oil <br />well pad; Section S-6 crosses the same drainage some distance down-gradient from <br />the oil welt pad, and also crosses a segment of 006-SEi Gulch. in both revised <br />PMT sections, the 006 valley is shallower than approved PMT (by 25 feet) and <br />shallower than pre-mine by approximately 50 feet. Valley shape in the pre-mine <br />topography is a relatively narrow "V" shape with steep side slopes. In the approved <br />topography, the valley is shallower with reduced side slopes, resulting in a broad <br />"V", while the trend (shallower with reduced side slopes) is carried even further in <br />the revised PMT, resulting in a broadly "U" shaped valley cross-section. Please <br />provide explanation and justification for this departure from the approved plan, <br />sufficient to demonstrate compliance with applicable provisions of Rule 4.14.1 and <br />4.14.2, or amend the Exhibit to conform to the original plan. <br />CHANNEL PROFILE COMPARISONS (EXHIBITS 20-5.1, 20-5.2, 20-5.4, AND 20-5.5) <br />On page 10, Tab 20 of the approved permit application (and on the amended page 10), <br />there is a list of seven specifications to be followed in the design, construction, and <br />maintenance of postmining drainage channels. The specifications emphasize geomorphic <br />criteria including concave longitudinal profile and absence of nick-points to ensure long term <br />stability without dependence on artificial structures. We have reviewed the revised <br />drainage profiles with consideration of these specifications, and the applicable geomorphic <br />criteria of 4.05.3 and 4.05.4. <br />Based on the revised profiles and previously discussed amended PMT plans, there appears <br />to have been a general tendency to "over-fill" the drainage valleys, resulting in .valleys that <br />are less deeply incised than planned. Rather than grading as necessary to achieve <br />geomorphically stable channel profiles and gradients, it appears that the channel designs <br />rely heavily on riprap, with a lack of focus on achieving concave drainage profiles, with <br />nick-points eliminated. <br />006 Gulch <br />14.' The over-all shape of the pre-mine profile is concave. There is amid-profile <br />convexity in the revised profile that is not present in the pre-mine. There are a few <br />