Restoration of Groundwater Quality Following Pilot-Scale Acidic In-Situ Uranium Leaching at Nine-Mile Lake Site Near Casper, Wyoming
- William H. Engelmann (USBM) | P.E. Phillips (Rocky Mountain Energy) | Daryl R. Tweeton (USBM) | Kent W. Loest (Rocky Mountain Energy) | Michael T. Nigbor (USBM)
- Document ID
- Society of Petroleum Engineers
- Society of Petroleum Engineers Journal
- Publication Date
- June 1982
- Document Type
- Journal Paper
- 382 - 398
- 1982. Society of Petroleum Engineers
- 4.1.2 Separation and Treating, 4.1.5 Processing Equipment, 2.2.2 Perforating, 6.5.4 Naturally Occurring Radioactive Materials, 6.5.3 Waste Management, 4.3.4 Scale, 5.8.2 Shale Gas
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The results of the first restoration effort for a pilot-scale acidic leaching of a uranium ore body in the U.S. are given. The project was performed under a cooperative agreement between the USBM and a joint venture consisting of Rocky Mountain Energy, Mono Power Co., and Halliburton Co. The leaching phase is described only briefly; it was reported earlier by Tweeton et al. Leaching was done with H2SO4 (pH range of 1.6 to 3.9) and H2O2 (80 to 1,000 ppm) over an 11-month period.
The restoration phase begun in September 1978 and was completed in 11 months. Water samples were taken from observation wells located between injection and production wells while the leaching solution was decreased in strength. Groundwater quality in the leached ore zone was restored by diluting and neutralizing effects of injecting native groundwater and treated water produced from recovered solution. Recovered water was purified by a combination of chemical precipitation and reverse osmosis. In situ measurements of pH, Eh, dissolved oxygen, conductivity, and temperature were made by a downhole probe in one of the wells. Water samples were taken and analyzed for U. V, Na, K, Ca, Mg, SO4, P, Cl, F, Fe, Mn, Si, Zn, As, and Se.
The USBM and the companies listed previously entered into a cooperative agreement aimed at modeling in situ leaching (ISL) of uranium with sulfuric acid at the venture's Nine-Mile Lake test site near Casper. WY (Fig. 1). Acid leaching of uraniferous ores is relatively unproved because most earlier ISL systems involved use of alkaline leachants. This report describes the first restoration of a pilot-scale acidic-leached ore body in the U.S. The results of an 11-month leaching phase conducted on a five-spot pilot test area (Pattern 2, Fig. 2) were previously reported by the Bureau of Mines. The study presented here consisted of weekly in situ determination of water quality parameters within the ore zone being restored plus additional water analysis in the laboratory.
The uranium mineralization occurs in Teapot sandstone members of the Upper Creataceous Mesaverde formation. The project site is located approximately 15 km (9 miles) north of Casper in Natrona County. The leached uranium ore (and aquifer) restored to baseline in this study was a bedded deposit ranging from 155 to 165 m (508 to 541 ft) deep. The sandstone contains quartz, feldspar, and minor amounts of mica, black (organic-containing) minerals, glauconite, carbonaceous fragments, blue to earthy clay inclusions, and disseminated argillaceous materials. The deposit is amenable to acidic leaching because of the relatively low carbonate content. The mineralization is typical of a roll-front type deposit. The principal uranium mineral is uraninite (UO2), with minor amounts of coffinite U(SiO4) 1-X (OH) 4X. Further de tails are found in the operators environmental report to the U.S. Nuclear Regulatory Commission (NRC).
The Teapot sandstone is an artesian aquifer confined by the overlying Lewis shale and the underlying Pumpkin Buttes shale. The formation dips to the east-northeast at about 7 with groundwater movement in that direction at about 4 m/a (14 ft/yr). The aquifer is recharged at the outcrop approximately 3 km (2 miles) west of the test area. Groundwater in the project area is marginally acceptable for livestock watering or industrial use.
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