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jPage 2) MINE ID # OR PROSPECTING ID #: nn_i9gn_ino INSPECTION DATE: con+amFiar 15 ~nn5 INSPECTOR=S INITIALS: A IW OBSERVATIONS This was a full warranty release request inspection conducted by Tony Waldron of DMG along with Ernie Shonts and Bruce Taylor of EI Paso County Road and Bridge. The site is located approximately 9 miles south of Yoder, Colorado. The pit is situated at the head of a sizeable natural drainage just where the contributing watershed begins to drop off of an upland area and cause down-cutting as the actual drainage begins. The pit extends well below the elevation of the original channel bottom thereby causing the pit to capture water prior to its release as it quickly infiltrates. All of the slopes are re-graded at the appropriate grade of 3H:1 V or flatter. The south, east and west sides are exhibiting fairly good geo-technical stability, unfortunately, the north side of the regraded pit is exhibiting some significant erosion features in the form of down-cutting gullies. Contour terraces have been installed oround the inside slopes of the pit. These are demonstrating to be most effective along the east, west and south pit slopes, however, the north slope is cutting through the terraces as water drains across and down these slopes. The revegetation effort across the pit would have to be termed spotty at best. Several areas are exhibiting good grass establishment, however, the northern side in particular is very poor. The operator has attempted to re-seed on more than one occasion; however, this area is just not taking very well. A discussion was held about changing the seed mix to include some species that are more adapted to the sandy soils. Also, it may be necessary to include more aggressive species that will quickly establish but eventually give way to the native grasses. Since the site is not fully stable or fully revegetated, it cannot be released at this time, therefore the request is being denied. There seems to be 2 main problems that may be difficult remedy. The first is that the backfilled material is very sandy and therefore not very resistant to erosion or very suitable for the establishment of vegetation. The second is that water from above the pit is naturally directed to a point above the pit slope will always want to run right down this slope. An upland diversion may help keep water off of the slope until vegetation con become established, however, once water is allowed to drain naturally, it will head right back over the slope and likely cause down-cutting due to the fact that the backfill and topsoil are composed mainly of sand. Even now, the terraces are incapable of holding and properly diverting water off of this north slope. Once the topsoil/sand becomes saturated is simply collapses and allows water to head to the next down slope terrace where the same thing occurs until it reaches the pit bottom. A couple of suggestions that were tossed around on site were to modify the seed mix to a more aggressive mix containing introduced species that may establish more quickly while still allowing the native grasses to come in over a longer period of time. Second, instead of continually fighting the erosion by re-grading and backfilling the down-cut area, the area where water wants to run naturally should be allowed to develop into a permanent drainage. This could be accomplished by accepting the fact that water will droin down the slope in this area in perpetuity. The area could then be widened out and a series of drop structures could be installed with moderate armoring of the channel bottom while trying to get the sides to revegetate. If the runoff velocities could be reduced or better managed, the down-cutting should attain some state of equilibrium that everyone can live with. The critical point in this plan will be the transition point from the relatively level and undisturbed upland area above the pit to where it begins its descent Across the backfilled slope. If this area can be thoughtfully designed and installed the rest of the drainage should develop over time. However, if this area is not properly installed head cutting will continue unabated until the drainage finds its own gradient which will allow for overland transport of water without serious down-cutting and erosion. In any event a technical revision will need to be submitted to the permit application revising the seed mix along with that portion of the reclamation plan dealing with surface water drainage. This will be cited as a problem on page three of this report along with corrective action dates.