Conoco Phillips Company (State of Texas)
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1.0 Site Identification
|Type of Site:||Unknown|
|Location:||Falls City, TX|
2.0 Site Status Summary
The Conquista Project was developed and operated as a mill to process uranium bearing ore from conventional surface mines in the Karnes County area of Texas. A radioactive material license was issued to Continental Oil Company (predecessor to Conoco, Inc. and ConocoPhillips) in September of 1971 authorizing the processing into uranium concentrate. The Conquista Project consisted of a mill complex and a tailings impoundment of approximately 250 acres adjacent to the mill complex. In addition to the waste from the mill operation, the licensee was also authorized to accept and place in the tailings impoundment for disposal up to 10 milligrams of radium-226 per year of contaminated solution from the Flatonia municipal water decontamination project, radioactive waste from other uranium processing facilities, by-product material from Rhone-Poulenc of Freeport, Texas (a rare earth extraction processing facility), and by-product material from Conoco, Inc.'s Trevino Project (an in situ leach uranium extraction project in Texas).
The authorization for processing was changed to (possession) incidental to reclamation activities in 1989 to reflect the licensee's decommissioning of the mill site. The structures and features of the mill complex were dismantled and placed in the tailings impoundment. The tailings impoundment has been capped and a vegetative cover established and is being monitored for performance. Since all structures and equipment have been removed from the site, there will be no release of equipment and materials to unrestricted use. The criteria for release of the site/termination of the license includes demonstration that the tailings impoundment does not exceed the radon flux limit of 20 pCi/m2-sec; gamma levels are indistinguishable from background; radium-226 concentration in soil does not exceed 5 and 15 pCi/g of radium-226 in the first 15 centimeters, and subsequent 15 centimeter soil horizons, respectively; natural uranium in soil does not exceed 30 pCi/g; demonstration that the tailings impoundment and disposal cell have stabilized; and either demonstration that the groundwater does not exceed the limits specified in a table that is comparable to Paragraph 5C in 10 CFR 40, Appendix A, or does not exceed alternate concentration limits, if so established.
3.0 Major Technical or Regulatory Issues
Groundwater contamination remains an outstanding issue. The licensee has yet to develop a plan satisfactory to the regulatory agency to determine the extent of groundwater contamination. The issue is confounded by the presence of a Title I site in the vicinity that is up-dip of the Conquista Project site and that possible contributor will be built into the model. The impoundment has experienced some settlement in previous years. A study to determine the cause of the settlement was conducted. The Licensee is currently devising a plan to remediate the settlement.