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Forming the sedimentary floor of the basin is the Pierre Shale, an olive-gray, clayey silty <br />shale that contains bentonite and marine fossils. The Pierre Shale is characterized by <br />very low hydraulic conductivity and is considered to be an impermeable unit relative to <br />the regional ground water system. Total thickness is approximately 3,900 feet. <br />Overlying the Pierre Shale are the sandstone beds of the Trinidad Formation. This <br />sandstone is a prodeltaic deposit in it's lower section and progresses upward into <br />tributary channel sands in the upper section. Total thickness is about 50 feet. <br />Overlying the delta deposits of the Trinidad sandstone are the complex deposits of <br />mudstones, siltstones, sandstones, and coal of the Vermejo Formation. These <br />sediments were deposited in a vast fluvial delta prograding eastward on the Trinidad <br />delta. Regional subsidence concurrent with deposition allowed moderate thicknesses <br />of coal to develop in river swamps of the delta plain. In ascending order, the coal <br />horizons of significance include the Rockvale, Canon City, Ocean wave, Royal Gorge, <br />Chandler, Wolf Park, and Brookside seams. Total thickness of the Vermejo is <br />approximately 700 feet. <br />Uncomformably overlying the Vermejo is the Raton Formation. This unit consists of two <br />members, a basal sandstone and an overlying sequence of interbedded mudstone and <br />sandstone. The basal sandstone is massive, cross-stratified and white to light-gray in <br />color with benonitic cementation and extensive rounded to sub-angular conglomerate <br />inclusions. The Raton Formation outcrops in the general area including most of Section <br />14 and the west portion of Section 13 west of Chandler Creek. Patches of the Poison <br />Canyon Formation overlie the Raton Formation in Section 14 and along the Fawn <br />Hollow bluffs in the western portion of the permit area. This formation consists of <br />mudstones and sandstones with a basal conglomerate sandstone. Depositionally and <br />physically it is similar to the Raton and it is difficult to distinguish between the two <br />formations. <br />The permit area is drained by Chandler Creek, a direct tributary to the Arkansas River. <br />Chandler Creek generally bisects the southeast portion of the permit area, parallel to <br />County Road 79. Chandler Creek is ephemeral in nature, flowing only in response to <br />infrequent rainfall and snowmelt in the early Spring. <br />Groundwater occurs as alluvial water, mostly toward the mouth of Chandler Creek at <br />the Arkansas River. Bedrock groundwater is isolated and limited, as evidenced by low <br />production in nearby domestic wells. Due to discontinuous lateral continuity of <br />sandstones and low hydraulic conductivities, no regional aquifers have been identified <br />in the general area. Minimal groundwater was encountered when drilling down to the <br />level of the Ocean Wave seam during exploration and monitoring well installation. <br />Groundwater quality is generally alkaline with dissolved solids in the range of 1100- <br />1600 mg/I and quality may have been altered due to past mining activities. <br />The semi-arid region receives an average of about 13 inches of precipitation on an <br />annual basis, generally from intense summer thunderstorms and occasional heavy <br />9 <br />