2011-12-06_REVISION - C1981019 - Laserfiche WebLink

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Environmental Scientists and Engineers. LLC are likely to meet the AVF definition and are therefore only potential AVFs. Further study is necessary on a site - specific basis to make the final determination. The OSM study covers the area potentially affected by the Collom lease area. Potential AVFs were identified in Morgan and Collom Gulches and in Jubb and Wilson Creeks in areas similar to those identified in the 1980 D &M report. All of these areas are located downstream of, and not within, the proposed pit limit. The OSM report does not determine if they are or are not significant to farming. Dames & Moore, 1995 Study In 1995, D &M updated their 1980 investigation to cover a large area and to address changes in the guidelines regarding AVF determinations. The study area included portions of Taylor, Wilson and Jubb Creeks as well as Collom, Little Collom, Straight and Morgan Gulches. The 1995 D &M effort was based on a review of existing maps, historical data and 1989 color aerial photography as well as additional field investigations. The extent of the 1995 study area is not clearly delineated on the enclosed map and is not sufficiently described in the text to allow one to be sure which areas have been investigated for AVFs and which have not. If additional areas were investigated, they were not clearly documented. The 1995 D &M study makes the following conclusions: • The historic hay meadow on Morgan Gulch meets the criteria for an AVF but makes no finding as to its significance to farming. The reports states that this AVF is both flood and sub irrigated. • A potential AVF in Collom Gulch of approximately 36 acres was identified as suitable for surface irrigation. However, the development of the necessary infrastructure would be cost prohibitive. • AVFs were identified on Jubb Creek, but are generally considered too small and disjointed to be economically farmed. The historic hay field on West Fork Jubb Creek appears to have soils that are poorly drained and costs associated with improving this problem are prohibitive. • Straight Gulch does not contain any AVFs. • AVFs were identified in Wilson Creek but they are considered too small to support economically viable agriculture. WMC's review of the 1995 D &M report indicates that the study area does not appear to adequately cover the proposed activity at the Collom Mine. A small amount of pit development will occur within the Straight Gulch drainage area above the Upper Straight Gulch monitoring station. While there is little potential for an AVF to be present, those lands within the portions of the Straight Gulch drainage basin that may receive drainage from the area disturbed by pit development should probably be included in the study. As with the original D &M report, additional supporting data are probably needed. Qualitative descriptions of soils, vegetation, and hydrology are discussed; but the maps, measurements, and other data which are required by the regulations are not presented. Pr PROJECTS Colo's ■o'.l IMEA Final•Hk.5I- -EA Collo., 08 0I 4. do, 24