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Dan Hernandez <br />June 3, 2013 <br />Page 6 <br />mudstones and siltstones located above and below the coal act as aquicludes and greatly restrict <br />vertical groundwater movement. According to records at the State Engineers' Office, existing <br />wells in the Vermejo generally have low yields ranging from 1 to 10 gallons per minute. <br />Ascending upward on the stratigraphic column from the Vermejo Formation is the Raton <br />Formation, a unit consisting of two members- a basal sandstone and muddy -sandy layer. The <br />Raton averages 650 feet in thickness. The erosional base of this unit marks the top of the <br />Vermejo Formation in the Southfield mine area. There are no coal- bearing units found in the <br />Raton. Unconformably overlying the Raton Formation are the sediments of the Poison Canyon <br />Formation. Similar in composition and character to the Raton, the Poison Canyon Formation <br />does not contain coal and is 200 feet in thickness of alternating beds of mudstone and sandstone. <br />Covering most of the topographic ridges in the Southfield mine area are a series of Pleistocene <br />boulder /colluvial /alluvial deposits. Most of the boulders consist of gneiss, schist and sandstones <br />derived from erosion and mass wasting of the Wet Mountain uplift to the south and west. <br />Depositional thicknesses range from 5 to 100 feet in places near the mine site, with 20 feet <br />recorded in the loadout area of the mine. <br />Groundwater Occurrence and Use <br />Essentially all of the lithologic units in the mine and loadout areas can function as aquifers under <br />favorable conditions. However, only the Trinidad Sandstone and colluvial /alluvial terrace and <br />valley deposits can be considered as potential aquifers for water supply purposes. The Trinidad <br />Sandstone is approximately 300 -400 feet below the interval to be affected by mining, while <br />colluvial /alluvial deposits are approximately 300 -600 feet above this interval in the mine area <br />and occur as surficial deposits in the loadout area. The extent and location of these units are <br />shown on the Regional Hydrogeology Map, (Map 5), the Mine Area Surface and Groundwater <br />Hydrology Map, (Map 12) and the loadout Area Surface and Groundwater Hydrology Map, <br />(Map 13). <br />The Trinidad Sandstone can serve as a marginal aquifer in this area, however it outcrops <br />approximately two (2) miles east of the mine area and within the mine area is approximately <br />three to four hundred feet below the interval mined at Southfield. The Trinidad Sandstone is <br />separated from the interval mined by a stratigraphic sequence consisting primarily of interbedded <br />and cross - bedded siltstones and shales which appear to have very low vertical permeabilities. <br />Given this vertical separation and limited permeabilities, the Trinidad Sandstone is effectively <br />isolated from any potential groundwater effects which might result from the Southfield mining <br />operations. <br />Within the mine area, the colluvial /alluvial deposits are located well above the interval to be <br />mined in the stratigraphic sequence. These deposits are exposed on the surface and are <br />intersected by many small ephemeral drainages. As a result, any water which may be stored in <br />the terrace deposits discharges to the surface water system along down gradient outcrops, and <br />terrace deposits in the mine area do not represent a significant or consistent source of <br />groundwater." <br />