Laserfiche WebLink
The PHC specifies that only shallow alluvial / colluvial groundwater has the potential to be affected at the <br />loadout. Since there are no groundwater monitoring locations at the loadout it will not discussed further in <br />this section. <br />Three formations remain under discussion: The Poison Canyon, the Raton and the Vermejo. In the <br />PHC section the prediction is made that groundwater impacts will be confined to "the interval <br />disturbed by mining extending up to and including abandoned mine workings in the Vento Seam <br />within the mine area'. Referring to figure 1, this interval is entirely within the Vermejo formation, <br />which is described elsewhere in the PAP as: <br />"... approximately 900 feet thick. Lithology of the Vermejo formation is highly variable with <br />significant cross - bedding and inter - bedding, and lithotypes varying from well cemented <br />sandstones to fine grained indurated siltstones. While many of the sandstones and coal seams <br />within the Vermejo formation are capable of storing and transmitting groundwater, the lenticular <br />nature and significant cross - bedding and inter- bedding which characterize this formation <br />effectively limit lateral continuity and consequent groundwater transmission capabilities." (Page <br />2.04.7 -2) <br />This description of the subsurface is consistent with the information gleaned from the Division's <br />analysis of drill logs (Exhibit 8 of the PAP). It is to be expected that multiple zones of perched <br />groundwater may exist within the interval expected to be affected by mining, (as well as in the Poison <br />Canyon and Raton formations, and the strata of the Vermejo formation above the Vento seam). To the <br />best of our knowledge, no attempt has been made to systematically locate, map or characterize these <br />perched zones; certainly such information does not exist with the Southfield mine PAP. Although more <br />detailed information may now be considered desirable, the subject was addressed at the time the mine was <br />permitted: <br />"Given the lenticular nature of the Vermejo Formation, there is a potential for occurrence of small <br />perched groundwater reservoirs where favorable lithologic and recharge characteristics exist. Any <br />such reservoirs which exist are expected to be limited in size and areal extent. Given the <br />uncertainties relative to the capacity and location of perched groundwater reservoirs, <br />beneficial use is unlikely and has not been attempted to date" (page 2.04.7 -4). <br />The empirical evidence of the drill logs is summarized by text on pages 2.04.6 -8 to -9: <br />"The only significant subsurface water encountered within the strata to be affected by current and <br />proposed mining activities is associated with abandoned mine workings. <br />Numerous perched groundwater reservoirs have been encountered throughout the Raton and <br />Vermejo Formations. Perched groundwater has been found in various locations and at varying <br />elevations throughout the permit area <br />Perched groundwater reservoirs appear to be limited in areal extent and storage capacity, <br />generally producing temporary flows of less than Sgpm when intercepted by drilling." <br />The Division finds no reason to refute the conclusions made at the time the mine was permitted: the <br />potential hydrogeologic effects of the Southfield Mine disturbance are restricted to an interval <br />bounded by the roof of the Vento seam above, and the floor of the Red Arrow seam below; and the <br />groundwater resources within this interval are limited in extent. <br />4 <br />