1. INTRODUCTION
This Environmental Baseline File (EBF) contains information on soil resources that may be useful to the U.S. Department of Energy (DOE) during the development of the Environmental Impact Statement (EIS) for the construction, operation, and eventual closure of a geologic repository (hereafter called the proposed action) at Yucca Mountain, Nye County, Nevada (60 FR 40164 - 40170, 1995). It summarizes the best available information describing soils in the areas to be affected and evaluates the impacts of the proposed action on soil resources. It also summarizes reports containing information that may be useful during development of the EIS for evaluating the suitability of soils for construction and other activities. Regions of influence considered in this EBF are Yucca Mountain and the transportation corridors and intermodal transfer facilities where land clearing and grading may occur. Soil resources in these regions may be affected (e.g., erosion, compaction) by construction of the repository, rail and heavy haul routes, and intermodal transfer facilities. Information on soil properties in these regions may be needed during development of the EIS to evaluate design criteria for those facilities. Section 2 of this report is a review of information on soils in and near the regions of influence. Section 3 is a summary description of soils at Yucca Mountain. Appendix A is a description of the soil series that may occur at Yucca Mountain. Appendix B lists limitations related to construction and engineering projects and physical and chemical properties of these soils series. The information summarized in this EBF should be sufficient for conducting the analysis of impacts on soil resources needed for the EIS. In addition, there are no opposing views concerning soil resources at Yucca Mountain; thus, sections on data needs and opposing views, which have been included in many other EBFs prepared for this project, are not included in this EBF for soil resources.2. INFORMATION ON SOILS
Subsection 2.1 summarizes information on the characteristics of soils at Yucca Mountain, soil contaminants at that site, the reclamation program conducted for site characterization, and disturbances that have occurred at Yucca Mountain. Information on the soils in the region surrounding Yucca Mountain that may be useful for development of the EIS is described in Subsection 2.2, and information on soils within transportation corridors and facilities is summarized in Subsection 2.3. Regulatory requirements related to the use, management, and conservation of soil have been summarized by DOE (1996a, Section 2.0) and are not discussed in this report.2.1 YUCCA MOUNTAIN
2.1.1 Soil Characteristics
Information on soils at Yucca Mountain is available from several soils, geological, engineering, and environmental studies conducted during site characterization. A third-order soil survey was conducted during 1989 on an 18-km2 area that included Midway Valley and the ridges west of Midway Valley. This area included most of the sites at Yucca Mountain where soil-disturbing activities for the proposed action are planned. Seventeen soil series were identified and grouped into seven map units, or associations (Table 1). The report summarizing this survey (Resource Concepts, Inc. 1989) describes the soil series and map units and lists some physical and chemical properties of the common series. Appendix A of this EBF includes detailed descriptions of these series. Appendix B describes limitations related to construction and engineering projects and physical and chemical properties of the series. The information in the appendices was obtained from the U.S. Department of Agriculture, Natural Resources Conservation Service (NRCS), Southern Nevada Resource Area Office, Las Vegas, Nevada. The appendices contain information from an unpublished soil survey of southwestern Nye County, south and west of Yucca Mountain. The descriptions, interpretations, and limitations from this survey should be characteristic of the soil series at Yucca Mountain. A more general, fourth-order soil survey and map has also been prepared for the entire Yucca Mountain area (Guertal and Davies 1997). The only soil orders found in this survey and in the third-order survey (Resource Concepts, Inc. 1989) were aridisols and entisols. Aridisols, the most extensive soil order at Yucca Mountain, are very dry soils with well-developed horizons that develop under conditions of low moisture. Consequently, some of these soils have lime-cemented hardpans. They occur most often on mesa tops, peidmont remnants, and old alluvial fans. Entisols are generally found on steep slopes and areas of more recent alluvium. They are young soils consisting of unconsolidated mineral materials lacking horizon development. Soil pits were dug at four locations in Midway Valley in 1985 to evaluate the suitability of soils for supporting foundations for proposed surface facilities (Ho et al. 1986). Soils at the four sites were similar. Index and engineering properties (e.g., permeability, compressibility, and shear strength), recommended bearing capacity, and estimated settlement of footings were presented. The soil was described as:"The alluvial material at the potential surface facility sites varies from about 35 to 150 feet in thickness. Generally, the soil in the top 1.5 to 2 feet contains a high percentage of fine sand and silt, and is quite loose. Below this layer, to a depth of about 8 feet, is a soil horizon (termed the K horizon) that is partly to wholly cemented with well-developed secondary calcite. The remaining alluvium to the top of bedrock is a gravel-sand mixture with little or no cementation." (Ho et al. 1986, p. 1)Geotechnical investigations were conducted in 1992 at 73 test pits located at, or near, the then-proposed location of the North Portal Facility in Midway Valley (Bureau of Reclamation 1992). Detailed descriptions of physical properties of soils from 46 of the test pits were presented, and recommendations were made for design bearing capacities and slopes. Soils were described as:
"Topsoil typically ranges from 0 to three feet of silty sand (SM), silty sand with gravel (SM), poorly graded gravel with sand, (GP-GM), and silty gravel with sand...The [underlying] soil at the site is primarily colluvium and alluvium generally composed of silty sand (SM) and silty gravels (GM, GP-GM) with fines ranging from 4 to 30 percent. Some clayey sand (SC) and clayey gravel (SC, GC) with fines ranging from 29 to 40 percent are present but in very limited amounts." (Bureau of Reclamation 1992, p. 13)Geotechnical investigations were also conducted near the Exploratory Studies Facility (ESF) in 1995 to assess facility design recommendations for the proposed muck conveyor (SNL 1995). Five test pits were dug in native soil; standard-penetration-test boreholes and plate-load tests were conducted on both native soil and fill material at the ESF pad. Information on the texture, compaction, bearing capacity, and the estimated settlement of native soil and fill material was presented, and recommendations for construction of foundations and footings were made. The native soil was described as:
"2 to 6 feet of moist [samples were conducted soon after rain], dark brown to brown, dense, cobbly to silty gravel soil with occasional boulders. The native soil overlies a slightly moist, light brown to whitish, partially to well calcium carbonate cemented conglomerate of cobbles and gravel with boulders, which essentially extended to the maximum trench depth which ranged from 19 to 20 feet deep." (SNL 1995, pp. 3 - 4)Guertal et al. (1994) characterized and measured horizons in the exposed soil of a cliff face in Fortymile Wash and calculated soil water retention parameters for each horizon. Guertal et al. (1994) also conducted a ponding experiment at the site to evaluate water infiltration. An equivalent of 30 years of precipitation (50,000 liters) was allowed to infiltrate into the soil. The maximum infiltration depth was 7.4 m. Petrocalcic horizons appeared to slow the vertical flow of water and caused water to flow horizontally. Soil samples were collected during 1989 - 1997 from 94 soil profiles at sites that were to be disturbed due to site characterization activities. The samples were collected to assist in formulating site-specific reclamation requirements (e.g., depth of salvageable soils and management of stockpiled soil) and to determine if soils had properties that would hinder reclamation (e.g., salinity, limited nutrients, etc.). The following parameters were measured for each sample: percent organic matter; percent sand, silt, and clay; water retention at –1/10, –1/3, and –15 bars; pH; electrical conductivity; extractable calcium, magnesium, sodium, and potassium; bicarbonate; bulk density; cation exchange capacity; and plant available nitrogen, phosphorus, iron, manganese, sulfur, and zinc. Hansen et al. (1997) conducted a wetlands assessment of the Nevada Test Site (NTS). The area closest to Yucca Mountain that contained hydric soils was at Cottonwood Springs, 6 km northeast of the ESF near the top of the western ridge of Fortymile Canyon. No springs, seeps, or other sites that may have hydric soils are known to occur on Yucca Mountain or to the west in Crater Flat.
2.1.2 Soil Contaminants
The Civilian Radioactive Waste Management System Management and Operating Contractor (CRWMS M&O) Environmental Protection Division tracks contaminated soils (hydrocarbon and other contaminants) at Yucca Mountain, and the Yucca Mountain Site Characterization Project adheres to the Spill Prevention, Control and Countermeasure Plan for Site Activities (CRWMS M&O 1998) which outlines the policies and practices for preventing, cleaning, and reporting soil contamination. PRO-EP-002, Nonhazardous Waste Management, describes the current policy for identification, excavation, accumulation, sampling, analysis, and transport to an off-site contractor of soils contaminated by hydrocarbons. CRWMS M&O (1999a) summarizes information on the levels of natural and man-made radionuclides in the soil at Yucca Mountain. These data were obtained from 98 surface soil samples collected within 16 km of the ESF. The naturally-occurring radionuclides uranium-234 and thorium-232 were found at low levels relative to published data from other areas around the world; however, the levels of potassium-40 and the progeny of uranium-234 (radium-226, lead-210, and polonium-210) and thorium-232 (radium-238 and thorium-228), all of which are naturally occurring, were relatively high. High levels of these radionuclides may be present because soil derived from igneous rocks (i.e., soils at Yucca Mountain) have higher concentrations of these radionuclides than soils derived from parent materials such as limestones and sandstones. The man-made radionuclides strontium-90, cesium-137, cesium-134, europium-155, and plutonium-239 were also detected in the soil samples, but generally at much lower levels than samples from the north and northeast of the ESF on the NTS (CRWMS M&O 1999a). There are no locations at Yucca Mountain known to have high concentrations of radionuclides resulting from atmospheric testing or other activities on the NTS; however, some areas in Area 25 (12 - 18 km east of the ESF) contain soils contaminated during nuclear rocket testing (DOE 1996b, Section 4.1.4.3).2.1.3 Reclamation Program
The goal of reclamation at Yucca Mountain is to return lands disturbed by site characterization activities to a form and productivity similar to the pre-disturbance state (DOE 1989, p. 1). Re-establishment of native vegetation on disturbances will minimize soil erosion, provide food and cover for native wildlife, and improve aesthetics. Some site characterization activities occur on lands administered by the Bureau of Land Management (BLM) and the BLM has stipulated in Right-of-Way Reservations and Plans of Development (BLM correspondence, E.F. Spang to C.P. Gertz, N-47748, January 6, 1988, MOL.19980529.0167; and E.F. Spang to DOE, N-48602, June 28, 1994, MOL.19971030.0184) that DOE must reclaim BLM lands disturbed by site characterization activities. The Reclamation Program Plan (RPP) (DOE 1989) defines the reclamation policy for the Yucca Mountain Site Characterization Project. The RPP directed the development of two additional plans: the Reclamation Feasibility Plan (DOE 1990) and the Reclamation Implementation Plan (RIP) (DOE 1995). The Reclamation Feasibility Plan (DOE 1990) addresses the technical data needs for reclamation and describes studies initiated to determine which reclamation techniques would be most successful at Yucca Mountain. The RIP describes reclamation activities planned at Yucca Mountain following disturbances and the steps to be taken to implement policies outlined in the RPP. The RIP further describes methods for topsoil salvage and stockpiling, interim and final reclamation, reclamation success standards, and post-reclamation monitoring. As part of the reclamation program at Yucca Mountain, topsoil has been salvaged and stockpiled since 1991 at most disturbed sites. Prior to disturbing a site, site-specific information is gathered to determine depth of salvageable topsoil and soil profile characteristics. After topsoil is stockpiled, it is stabilized with a chemical stabilizer (e.g., Hydroshield or Soil Master) to reduce wind and water erosion, and large stockpiles are revegetated. In 1993, a study was initiated to determine the effects of stockpile depth and duration of stockpiling on soil viability (i.e., soil microbial populations and soil physical and chemical properties). Data collected for this study have been analyzed, and a report is being prepared. Preliminary results indicated that there were no significant differences in soil microbial activity (i.e., bacteria and fungi) at different depths, microbial biomass in stockpiled soil was different from undisturbed topsoil, and microbial biomass in the stockpile generally was different from undisturbed soil during the second year. It was conducted that topsoil stockpiling was not detrimental to soil viability and that current management practices for topsoil stockpiling at Yucca Mountain should continue. Reclamation studies have been conducted at Yucca Mountain to determine the feasibility of using soil amendments (e.g., fertilizers, water absorbing gels, etc.), mulches, water harvesting techniques, transplants, soil stabilization agents, fill materials as topsoil replacement, and irrigation to improve reclamation success. Initial results of these studies have been reported (CRWMS M&O 1999d), and many of the study plots will be monitored to determine long-term effects of the various treatments. As described in the RIP, interim reclamation was conducted on several disturbed sites and topsoil stockpiles where activities are ongoing. The primary objective of interim reclamation is to stabilize soils and minimize erosion until final reclamation is implemented. As of January 1998, interim reclamation had been conducted on approximately 14 ha at Yucca Mountain. After activities are completed at a site, final reclamation is conducted using techniques developed from the reclamation feasibility studies. The primary objectives of final reclamation are erosion minimization and establishment of a stable vegetative cover similar to the adjacent plant community. As of January 1998, final reclamation had been conducted on an additional 14 ha. Post-reclamation monitoring is being conducted to determine whether reclamation success standards have been met. Parameters monitored include plant cover, plant density, species richness (number of species present per unit area), animal use, and soil erosion. Reclamation success standards and specific post-reclamation monitoring methods will be addressed in the revised RIP.2.1.4 Soil Disturbances at Yucca Mountain
The amount of land disturbed by site characterization activities is measured quarterly by the CRWMS M&O Environmental Sciences Department and reported to DOE. As of March 30, 1998, approximately 1.26 km2 had been disturbed at or near Yucca Mountain for site characterization activities (CRWMS M&O correspondence, M.W. Harris to W.R Dixon, May 11, 1998, MOL.1998.01717.0009). An additional 3.1 km2 were disturbed prior to the initiation of site characterization activities in 1991. Almost half of the disturbances that occurred during site characterization were at four sites: The Fran Ridge borrow pit (18 ha), ESF (16 ha), mine-spoil storage area (12 ha), and topsoil storage area (9 ha). The remainder of the disturbances were smaller and were scattered throughout the Yucca Mountain area (CRWMS M&O 1999c).2.2 REGION SURROUNDING YUCCA MOUNTAIN
A brief, general description of soils at the NTS can be found in an EIS by the DOE (1996b, Subsection 4.1.4.3). This EIS also discusses soil contaminants, primarily radionuclides, their location, extent, and movement potential in the soil. During the 1980s, the NRCS conducted a third-order soil survey in southwestern Nye County, including the region south and west of the NTS. The results of that survey have not been published, but information is available from the NRCS, including information on the suitability of soils in this region for farming, mining of fill material, and other uses. None of the series identified are considered prime farmland. The CRWMS M&O (1999b) report reviewed data from the NRCS soil survey of southwestern Nye County. This report also summarized data from 8 cultivated and 23 uncultivated sites in the Amargosa Valley (located 5 - 26 km south of Yucca Mountain) that were sampled to determine if the soils in these sites were suitable for farming. That report includes detailed information on the morphology and chemistry of soils at the sites sampled. It also contains a map of soil types in the region and appendices describing the soil series there. Soils that were suitable and unsuitable for farming were found in the area south of Yucca Mountain.2.3 TRANSPORTATION CORRIDORS AND FACILITIES
The best available information on soils within transportation corridors and facilities comes from soil surveys conducted by the NRCS. Soil surveys of specific interest due to their proximity to rail corridors are:3. DESCRIPTION OF SOILS AT YUCCA MOUNTAIN
A third-order soil survey was conducted on an approximately 18-km2 area centered on Midway Valley and the ridges to the west (Resource Concepts, Inc. 1989). A more general soil survey was also conducted of the entire Yucca Mountain area (Guertal and Davies 1997), and the NRCS has conducted, but not published, a third-order soil survey of southwestern Nye County, south and west of the NTS. Seventeen soil series and seven associations, or map units (Table 1), were identified at Yucca Mountain (Resource Concepts, Inc. 1989). None of these series are classified as prime farmlands. Based on a wetlands assessment of the NTS (Hansen et al. 1997), there are no hydric soils at Yucca Mountain. Soils at Yucca Mountain are derived from underlying volcanic rocks and mixed alluvium dominated by volcanic material. They generally have a low water-holding capacity. The shallow soils on ridge tops at Yucca Mountain often consist of a thin hardpan on top of bedrock and are well to excessively drained. The soils have A horizons typically less than 15 cm thick, and a B horizon from 5 to 30 cm thick may be present. Soil textures are gravelly to cobbly, loamy sands to sandy loams. Soils are calcareous, with lime coatings on the underside of rocks in the B horizon. They are moderately to strongly alkaline with a pH ranging from 8.0 to 8.6. Rock fragments ranging in size from gravel to cobbles dominate approximately 45 to 65 percent of the surface. Soils on fan piedmonts and within steep, narrow canyons are moderately deep to deep and well drained. These soils developed from volcanic residuum, with a component of calcareous eolian sand. Soils that formed in volcanic residuum range from moderately shallow to moderately deep over a thin duripan on top of bedrock. The A horizons are generally less than 25 cm thick, with a B horizon between 25 and 50 cm thick. Mixed soils containing volcanic residuum and calcareous eolian sand are often deep or moderately deep with a well-cemented duripan or petrocalcic horizon. The A horizons are less than 15 cm thick, with a C horizon up to 150 cm deep. Soil textures are gravelly, sandy loams with 35 to 70 percent rock fragments. Soils are calcareous and moderately to strongly alkaline. Soils on alluvial fans and within stream channels are very deep and well to excessively drained. The A horizons are generally less than 20 cm thick, with C horizons up to 150 cm deep. Soil textures are very gravelly, with fine sands to sandy loams with abundant rock fragments. The soils are calcareous and moderately alkaline.4. REFERENCES
4.1 DOCUMENTS CITED
Bureau of Reclamation 1992. Soil and Rock Geotechnical Investigations Field and Laboratory Studies, North Ramp Surface Facility, Exploratory Facility, Yucca Mountain Project, Nevada. TM36109235. Denver, Colorado: U.S. Department of Interior, Bureau of Reclamation. TIC: 208867. CRWMS M&O (Civilian Radioactive Waste Management Systems Management and Operating Contractor) 1998. Spill Prevention, Control, and Countermeasures Plan for Site Activities. BAB000000-01717-4600-00009 REV 00. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.19990223.0249. CRWMS M&O 1999a. Distribution of Natural and Man-Made Radionuclides in Soil and Biota at Yucca Mountain, Nevada. Las Vegas, Nevada: CRWMS M&O. ACC: MOL. 19990218.0217. CRWMS M&O 1999b. Evaluation of Soils in the Northern Amargosa Valley. B00000000-01717-5705-00084 REV 00. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.19990224.0268. CRWMS M&O 1999c. Land Surface Disturbances Documented Prior To and After June, 1991. Las Vegas, Nevada: CRWMS M&O. DTN: MO9902LANDSURF.000. CRWMS M&O 1999d. Reclamation Feasibility Studies at Yucca Mountain, Nevada: 1991-1995. B00000000-01717-5700-00003 REV 00. Las Vegas, Nevada: CRWMS M&O. ACC: MOL.19990127.0399. DOE (U.S. Department of Energy) 1989. Draft Reclamation Program Plan for Site Characterization. DOE/RW-0244. Washington, DC: Office of Civilian Radioactive Waste Management. ACC: NNA.19890717.0031. DOE 1990. Draft Reclamation Feasibility Plan. DOE/YMP-90-10. Las Vegas, Nevada: Nevada Operations Office/Yucca Mountain Site Characterization Project Office. ACC: NNA.19900302.0052. DOE 1995. Reclamation Implementation Plan. YMP/91-14, Rev. 1. Las Vegas, Nevada: Office of Civilian Radioactive Waste Management. ACC: MOL.19960222.0218. DOE 1996a. Yucca Mountain Site Characterization Project Environmental Field Activity Plan for Soils. YMP/90-11, Rev. 0. Las Vegas, Nevada: U.S. Department of Energy. ACC: MOL.19960722.0066. DOE 1996b. Final Environmental Impact Statement for the Nevada Test Site and Off-Site Locations in the State of Nevada. Volume 1. DOE/EIS 0243. Las Vegas, Nevada: DOE Nevada Field Office. TIC: 226875. Guertal, W.R. and Davies, W.J. 1997. Preliminary Surficial Materials Properties Map: Soils of the Yucca Mountain Area, NV. Las Vegas, Nevada: Yucca Mountain Site Characterization Project. DTN: GS960408312212.005. Guertal, W.R.; Flint, A.L.; Hofmann, L.L.; and Hudson, D.B. 1994. "Characterization of a Desert Soil Sequence at Yucca Mountain, Nevada." High Level Radioactive Waste Management, Proceedings of the Fifth Annual International Conference, Las Vegas, Nevada, May 22-26, 1994, 5, 2755-2763. La Grange Park, Illinois: American Nuclear Society. TIC: 234753. Hansen, D.J.; Greger, P.D.; Wills, C.A.; and Ostler, W.K. 1997. Nevada Test Site Wetlands Assessment. DOE/NV/11718-124. Las Vegas, Nevada: Bechtel Nevada Corporation. TIC: 242338. Ho, D.M.; Sayre, R.L.; and Wu, C.L. 1986. Suitability of Natural Soils for Foundations for Surface Facilities at the Prospective Yucca Mountain Nuclear Waste Repository. SAND85-7107. Albuquerque, New Mexico: Sandia National Laboratories. TIC: 202804. NRCS (National Resources Conservation Service) 1998. National Soil Data Access Facility: Official Soil Series Description (Soil Attribute Database). [Accessed November 6, 1998]. Available: http//www.statlab.iastate.edu/soils/nsdaf. TIC: 241713. Resource Concepts, Inc. 1989. Soil Survey of Yucca Mountain Study Area, Nye County, Nevada. NWPO EV00389. Carson City, Nevada: Resource Concepts, Inc. TIC: 206227. SNL (Sandia National Laboratories) 1995. Geotechnical Engineering Investigation for the Proposed Muck Conveyor Foundations at the ESF. Albuquerque, New Mexico: SNL. ACC: MOL.19950815.0024.4.2 STANDARDS & REGULATIONS CITED
60 FR (Federal Register) 40164-40170. Preparation of an Environmental Impact Statement for a Geologic Repository for the Disposal of Spent Nuclear Fuel and High-Level Radioactive Waste at Yucca Mountain, Nye County, Nevada. 1995. TIC: 239036.4.3 PROCEDURES
PRO-EP-002, Nonhazardous Waste Management