Coal in the Ferron Sandstone Member of the Mancos Shale of Cretaceous age has traditionally been mined by underground techniques in the Emery Coal Field in the southern end of Castle Valley in east-central Utah. However, approximately 99 million tons are recoverable by surface mining. Ground water in the Ferron is the sole source of supply for the town of Emery, but the aquifer is essentially untapped outside the Emery area.
The Ferron Sandstone Member crops out along the eastern edge of Castle Valley and generally dips 2 ? to 10 ? to the northwest. Sandstones in the Ferron are enclosed between relatively impermeable shale in the Tununk and Blue Gate Members of the Mancos Shale. Along the outcrop, the Ferron ranges in thickness from about 80 feet in the northern part of Castle Valley to 850 feet in the southern part. The Ferron also generally thickens in the subsurface downdip from the outcrop. Records from wells and test holes indicate that the full thickness of the Ferron is saturated with water in most areas downdip from the outcrop area.
Tests in the Emery area indicate that transmissivity of the Ferron sandstone aquifer ranges from about 200 to 700 feet squared per day where the Ferron is fully saturated. Aquifer transmissivity is greatest near the Paradise Valley-Joes Valley fault system where permeability has been increased by fracturing. Storage coefficient ranges from about 10 .6 to 10 -3 where the Ferron sandstone aquifer is confined and probably averages 5 x 10 -2 where it is unconfined.
The largest source of recharge to the Ferron sandstone aquifer in the Emery area is subsurface inflow from the Wasatch Plateau to the west (about 2.4 cubic feet per second during 1979), most of which moves laterally through the more permeable zone along the Paradise Valley-Joes Valley fault system. Little water is recharged to the aquifer by the 8 inches of normal annual precipitation on the outcrop area. Natural discharge from the aquifer is mainly leakage to alluvium along streams in the outcrop area and leakage to the enclosing shales in the Tununk and Blue Gate Members. Discharge from wells that tap the Ferron in Castle Valley averaged about 0.3 cubic foot per second during 1979. Discharge from the underground Emery Mine averaged about 0.7 cubic foot per second during 1979 and was the largest manmade discharge from the aquifer.
The largest quantities of water are available from the Ferron sandstone aquifer within about 2 miles of the Paradise Valley-Joes Valley fault system in the Emery area. Most wells in this area naturally flow at the land surface at rates less than 100 gallons per minute, but yields could be increased by pumping. Wells that fully penetrate the aquifer in this area could be expected to produce 100 to 500 gallons per minute if pumped. In the northern two-thirds of Castle Valley the Ferron would probably not yield more than 10 gallons per minute to individual wells.
The concentration of dissolved solids in water from the Ferron sandstone aquifer in the Emery area increases eastward from the Paradise Valley-Joes Valley fault system toward the outcrop area of the Ferron, in the general direction of ground-water movement. Dissolved-solids concentrations also increase upward in the aquifer in
areas downdip from the outcrop. In the Emery area, dissolved-solids concentrations in water from the Ferron ranged from less than 500 to more than 8,000 mg/L (milligrams per liter) during 1979. Deterioration in water quality in the Emery area usually is due to increased concentrations of dissolved sodium and sulfate. In the northern two-thirds of Castle Valley, dissolved-solids concentrations usually exceed 3,000 rag/L, and several test holes and gas wells have yielded water from the Ferron with chloride concentrations greater than 10,000 mg/L and dissolved-solids concentrations greater than 20,000 mg/L.
Quitchupah Creek, near the underground Emery Mine, and Christiansen Wash, downstream from a propos
Additional Publication Details
USGS Numbered Series
Hydrology of the Ferron sandstone aquifer and effects of proposed surface-coal mining in Castle Valley, Utah; with a section on Stratigraphy and Leaching of overburden