Geology topics
G. E. Cordy
Publications and source records attributed to G. E. Cordy.
Hydrology of the L.C. Holding coal-lease tract and adjacent areas, southwestern Utah, and potential effects of coal mining
The U.S. Bureau of Land Management recognized a need for baseline hydrologic data and an understanding of the hydrologic system in the L.C. Holding coal-lease tract in order to determine the potential effects of mining on the water resources of the area. The potential impacts of mining on the hydrology of the area are of concern because Zion National Park is less than 3 miles from the westernmost part of the lease tract. Much of the water that passes through the Park either originates in the lease tract or traverses it. Runoff from melting snowpacks and summer thundershowers contributes most of the flow to perennial streams in the area. Base flow is sustained by spring discharge and diffuse seepage. Regional groundwater movement is southward. Most of the geologic formations in the study area contain aquifers. The water table of the regional aquifer is about 870 ft deep in the Navajo Sandstone. Groundwater issuing from the Navajo Sandstone on the east side of Zion Canyon has specific conductance values several times larger than groundwater from the west side, indicating recharge to the Navajo from the overlying strata, which contain water of larger specific conductance. Potential effects of mining in the area include: (1) increased dissolved-solids concen- trations and decreased pH values in both surface and groundwater; (2) dewatering of aquifers, causing a decrease or cessation of flow to some springs; and (3) land subsidence and associated subsidence fractures.
Hydrology and potential effects of mining in the Quitchupah and Pines coal-lease tracts, central Utah
Bydrologic data were collected for the proposed Quitchupah and Pines coal-lease tracts in Sevier and Bnery Counties, Utah, in order to describe the hydrology and potential effects of mining on the hydrologic system. The Quitchupah and Pines coal-lease tracts are near the Southern Utah Fuel Company coal mine in an area of the central Wasatch Plateau that is characterized by a relatively flat plateau deeply dissected by steep-sided canyons. Surface water in the Quitchupah and Pines study area drains to two perennial streams, Muddy Creek to the north and Quitchupah Creek to the south. Peak streamflow is usually in May and June in response to snowmelt runoff; however, thunderstorms can cause short-term high flows in late summer and fall. The specific conductance of surface water in and near the study area measured during the 1987 water year ranged from 440 (iS/cm to 860 (iS/cm. Suspended-sediment concentrations ranged from 17 to 10,900 mg/L in the Quitchupah Creek drainage and 34 to 312 mg/L in the Muddy Creek drainage. Stable-isotope studies indicate that recharge to aquifers in the study area is by seepage of snowmelt into rock outcrops. Discharge from the aquifers is at springs, seeps, mines, and zones of seepage in streambeds. The chemical quality of ground water is related to the mineralogy of the formations with which the water has contact. Water from the upper part of the Cast legate Sandstone has the smallest concentration of dissolved solids, 61 mg/L, and water from the North Horn Formation has the largest concentration, 1,080 mg/L. Observed effects of underground coal mining at the nearby active mine are considered indicative of the changes that can be expected in the Quitchupah and Pines coal-lease tracts. Subsidence above the mined area could cause dewatering of the Blackhawk Formation and the Star Point Sandstone, changes in the natural drainage patterns, and alteration of both surface- and ground-water quality. Additional studies are needed to gain a better understanding of the hydrologic effects of underground mining in the Quitchupah and Pines coal-lease tracts.