GENERAL51479 - Laserfiche WebLink

Home Browse Search

-27- The third well (LA 264) was designed to provide an assessment of the water bearing capacity of the overburden in addition to that provided by the core permeability tests. The open interval in this well began at a depth of 62 ft. and ended at a depth of 276 ft. During drilling, water inflow was encountered at about 72 ft. The inflow was estimated to be about 15 gpm and no significant increase in discharge was observed over the remainder of the hole. It is probable that a thin fracture zone at the 72 ft, level accounts for most all of the water produced by this w~ll. This well had a permeability of 0.42 ft/d and a transmissivity of 90.7 ft /d. The location and geometry of the Purgatoire River does not appear to be related to the occurrence of fractures, jointing, or faulting. There does not appear to be any direct hydrologic connection through fractures between the stream-alluvial system and the Allen coal seam. The mine workings maps for the Allen Mine do not show fault systems beneath the surface streams. This further supports the contention that surf ace stream valleys are not fault-controlled. Faults located below and adjacent to overlying streams do f / not contribute point source mine inflows. ~~ The Allen and Maxwell seams are confined artesian aquifers in the general U~ area. The coal seams are confined by the shales and silt stones of the overlying Raton Formation and the underlying Raton and Vermejo Formations. Ground water flow in the coal is through coal cleats and minor fractures. The coal seams are recharged by old mine workings and oxidized coal/burn zones along the coal outcrops, and by surface/alluvial systems at the coal subcrops in stream valleys.. The major recharge area for the coal seams adjacent to the mines are located ,lust west and southwest of the existing Allen Mine workings. Both the Allen and Maxwell coal seams lie more than 300 ft. below the Purgatoire River. The coal seams discharge to the center of the Raton Basin. No springs or seeps have been identified which discharge from the coal seams. There are no water wells completed in the coal seams. Water quality data from well LA 221A is believed to be representative of the undisturbed waters in the coal seam. Water pumped from well LA 264 is believed to be produced from a thin fracture zone in the overburden at a depth of approximately 72 feet, as discussed previously. Though the water sample from this well represents a zone high in the overburden, the composition and total concentrations are very similar to the corresponding parameters from well LA 221A completed in the coal. This observation suggests a uniform water quality throughout the profile. Both the coal water and the overburden water show a similar chemistry. The water is a sodium-bicarbonate type water. The coal seam has higher concentrations of carbonate, total iron, total manganese, total zinc, and a slightly higher pH than found in the overburden water. Sulfate concentrations in the coal seam were slightly lower than in the overburden. Data on other trace metal concentrations were not provided. C. Ground Water - Alluvial Aquifers I, Investigation of the alluvial ground water along the Middle Fork and main stem of the Purgatoire River was conducted by drilling eight holes (3 at the Allen ~ Mine, and 5 at the Maxwell Mine) through the alluvium to bedrock and