Remedial action plan and site design for stabilization of the inactive uranium mill tailings site at Falls City, Texas. Remedial action selection report, attachment 2, geology report; attachment 3, groundwater hydrology report; and attachment 4, water resources protection strategy. Final report

Abstract

contaminated by the former mills, and implementation of the remedial action (Subpart C). This RAS describes how the remedial action at Falls City will meet these standards.-1- 5EXISTING GROUND SURFACE---, -1 , aspects of p i l e design; radiological issues (such as design of the radon barrier) ; and protection of groundwater resources.Copies of these documents, as well as supporting data and calculat i o n s , are on f i l e i n the UMTRA Project Office i n Albuquerque, New Mexico. The approach adopted i n the RAS is similar to t h a t adopted by the NRC for s i t e Technical Evaluation Reports (TERs). T h i s RAS is formatted i n accordance w i t h the requirements of the NRC's Stantlard Format and Content (SF&C) guide (NRC, 1989a) for remedial action selection for UMTRA Project sites. The RAS has been compiled t o f a c i l i t a t e the NRC i n preparation of i t s TER. The RAS does not contain design details. The d e t a i l s are available i n supporting documents, reports, drawings, specifications, and calculations. Table 1.2 summarizes the relationship between design d e t a i l s and c r i t e r i a and supporting cal cul a t i ons and reports. Design thickness of 2.0 feet w i l l l i m i t radon f l u x t o meet EPA c r i t e r i a , including 6-inch allowance f o r shrinkage cracking. The site geological characterization should provide estimates of earthquakeinduced ground accelerations that could occur at the site, as well as the potential for other types of tectonic hazards that could affect the performance of the disposal cell. Geological site characterization must also demonstrate that future resource development will not adversely affect the disposal cell's stability for the design life. The TAD (DOE, 1989a) contains additional criteria that form the basis for evaluating the adequacy of the site and regional geology. These criteria also form the basis of the work described here. SCOPE OF WORKDetailed investigations of geologic, geomorphic, and seismic conditions at the site were conducted by the Technical Assistance Contractor (TAC). Geologic investigations were carried out in accordance with the procedures and approaches described in the TAD in order to gather the data specified in the NRC SRP and SF&C (NRC, 1989a). These investigations included compilation and analysis of previously published and unpublished geological literature and data; review and analysis of historical and instrumental seismic data; geological field mapping and observations; review of site-specific subsurface geologic and geotechnical data, including borehole logs and samples from boreholes, test pits, and trenches; aeri a1 reconnaissance and analysis of stereo-pair aeri a1 photographs; geologic interpretation of existing LANDSAT satellite imagery; and studies of previous work. Details of the data gathering and interpretation procedures are provided in the documents referenced in this section.The nearby faults, the proximity of uranium ore, the complexity of the underlying stratigraphy, and the potential for erosion...