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photography, surface water flow measurements, piezometer water level <br />measurements, and visual inspections. The monitoring frequency for each structure <br />or feature is designed to span the pre-subsidence to post-subsidence time period. <br />XVI. Concurrent Surface and Underground Mining <br />1. This section does not apply to the West Elk Mine. <br />XVII. Operations on Alluvial Valley Floors <br />MCC has performed a detailed reconnaissance investigation for alluvial valley floors <br />(AVFs). During the investigation, MCC identified several areas within or adjacent to the <br />mine plan area which may meet the geomorphic criteria of alluvial valley floors. <br />Alluvial deposits were identified along Minnesota Creek, the Dry Fork of Minnesota <br />Creek, Sylvester Gulch, and the North Fork of the Gunnison River. Based on MCC's <br />reconnaissance, and the Division's field inspections, the Division designates the <br />following three areas as alluvial valley floors: 1) North Fork AVF - North Fork of the <br />Gunnison River downstream from Gribble Gulch, 2) Minnesota Creek Main Stem <br />AVF - The alluvial deposits of the main stem of Minnesota Creek extending from the <br />north section line of Section 17, T14S, R90W, downstream to the North Fork of the <br />Gunnison, 3) Minnesota Creek Lower East Fork AVF - The alluvial deposits on the <br />lower East Fork of Minnesota Creek, extending from the upper limit of mapped alluvial <br />deposits in Section 9, T14S, R90W to the confluence with the main stem of Minnesota <br />Creek. Mining will not occur in these AFVs. <br />MCC's monitoring, as described below, will provide sufficient information for the <br />Division to determine that the requirements of 4.24.4 (1)(a), (b), and (c) are being met. <br />North Fork AVF - Oxbow Mining monitors North Fork surface water <br />immediately downstream from the headgate of the Fire Mountain Canal <br />(site NF-3). This site is within a subirrigated portion of the modern-day <br />alluvial valley, approximately 2 miles upstream from the agriculturally <br />productive North Fork AVF. Data from site NF-3 enables identification <br />of material damage to the quantity and quality of water supplying the <br />North Fork AVF. MCC's contribution to impacts can be identified from <br />MCC's monitoring of its CDPS outfalls, approximately 2.5 miles <br />upstream from NF-3. Significant inputs from the West Elk Mine would <br />occur only from the part of the mine that is upstream from Somerset, as <br />the Lone Pine Gulch area no longer has a pumping site and has been <br />Phase II bond-released. <br />Minnesota Creek Main Stem AVF - MCC financially supports the USFS <br />monitoring station that is located on this AVF. This station and MCC's <br />monitoring upstream from the AVF would enable identification of <br />material damage to the quantity of water supplying the AVF. Material <br />damage to water quality would not be expected because the mine does <br />not propose to discharge mine water to this drainage. <br />52