Final Remedial Investigation Report Uravan Uranium Project (Union Carbide) Superfund Site Uravan, Colorado EPA Contract No. EP-W-05-049 Work Assignment No: 354-TATA-0846 Prepared by: CDM Federal Programs Corporation October 2017 CDMlhSm1 RESPONSE ACTION CONTRACT FOR REMEDIAL, ENFORCEMENT OVERSIGHT, AND NON-TIME CRITICAL REMOVAL ACTIVITIES AT SITES OF RELEASE OR THREATENED RELEASE OF HAZARDOUS SUBSTANCES IN EPA REGION VIII U. S. EPA CONTRACT NO. EP-W-05-049 FINAL REMEDIAL INVESTIGATION REPORT Uravan Uranium Project (Union Carbide) Uravan, Colorado Work Assignment No.: 354-TATA-0846 October 2017 Prepared for: U. S. ENVIRONMENTAL PROTECTION AGENCY Region VIII 1595 Wynkoop Street Denver, Colorado 80202-1129 Prepared by: CDM FEDERAL PROGRAMS CORPORATION 555 17th Street, Suite 500 Denver, Colorado 80202 Table of Contents Section 1 Introduction ....................................................................................................... 1-1 1.1 Purpose and Approach ........................................................................................................................................... 1-1 1.2 Site Background and Regulatory Framework .............................................................................................. 1-1 1.3 Report Organization ................................................................................................................................................ 1-3 Section 2 Site Physical Characteristics................................................................................ 2-1 2.1 Demographics, Land Use, and Ownership...................................................................................................... 2-1 2.1.1 Current Ownership and Land Use........................................................................................................ 2-1 2.1.2 Reasonably Likely Future Ownership and Land Use ................................................................... 2-2 2.2 Climate........................................................................................................................................................................... 2-3 2.3 Geology.......................................................................................................................................................................... 2-3 2.3.1 Stratigraphy................................................................................................................................................... 2-3 2.3.2 Structure ......................................................................................................................................................... 2-4 2.3.3 Seismicity........................................................................................................................................................ 2-4 2.3.4 Active Faults..................................................................................................................................................2-4 2.3.5 Geomorphic Processes.............................................................................................................................. 2-5 2.4 Hydrogeology ............................................................................................................................................................. 2-5 2.4.1 Chinle Formation......................................................................................................................................... 2-6 2.4.2 Wingate Sandstone..................................................................................................................................... 2-6 2.4.3 Kayenta Formation..................................................................................................................................... 2-6 2.4.4 Navajo Formation ....................................................................................................................................... 2-7 2.4.5 Entrada Formation ..................................................................................................................................... 2-7 2.4.6 Summerville Formation ........................................................................................................................... 2-7 2.4.7 Morrison Formation .................................................................................................................................. 2-7 2.4.7.1 Salt Wash Member........................................................................................................................ 2-7 2.4.7.2 Brushy Basin Member................................................................................................................. 2-8 2.4.8 Burro Canyon Formation.........................................................................................................................2-8 2.4.9 Dakota Sandstone ....................................................................................................................................... 2-9 2.5 Hydrology..................................................................................................................................................................... 2-9 2.5.1 General............................................................................................................................................................. 2-9 2.5.2 Flood Forecast..............................................................................................................................................2-9 2.5.3 Surface Water Chemistry.........................................................................................................................2-9 2.6 Ecological Setting....................................................................................................................................................2-10 2.6.1 Soils.................................................................................................................................................................2-10 2.6.2 Regional Vegetation .................................................................................................................................2-11 2.6.2.1 Pinon-Juniper Woodland .........................................................................................................2-11 2.6.2.2 Sage-Grass Community.............................................................................................................2-11 2.6.2.3 Riparian Community..................................................................................................................2-12 2.6.3 Threatened, Endangered, and Sensitive Species .........................................................................2-12 Section 3 Remedial Action Objectives................................................................................ 3-1 3.1 Identification of Potential ARARs ...................................................................................................................... 3-1 3.2 Remedial Action Objectives.................................................................................................................................. 3-2 3.3 Preliminary Remedial Goals................................................................................................................................. 3-3 i Table of Contents 3.3.1 Remedial Action Goals for Soil...............................................................................................................3-3 3.3.2 Remedial Action Goals for Groundwater...........................................................................................3-6 3.3.2.1 Remedial Action Goals for Groundwater.............................................................................3-6 Section 4 Previous Investigations and Remedial Actions.................................................... 4-1 4.1 Solids ..............................................................................................................................................................................4-2 4.1.1 Atkinson Creek Disposal Area................................................................................................................4-2 4.1.2 Club Ranch Ponds Area.............................................................................................................................4-3 4.1.2.1 Phase 1 Remediation....................................................................................................................4-4 4.1.2.2 Phase 2 Remediation....................................................................................................................4-5 4.1.2.3 Phase 3 Remediation....................................................................................................................4-5 4.1.3 River Ponds Area.........................................................................................................................................4-8 4.1.4 Tailings Piles...............................................................................................................................................4-10 4.1.4.1 B-Plant Repository..................................................................................................................... 4-13 4.1.5 Club Mesa Area..........................................................................................................................................4-13