In passing the Nuclear Waste Policy Act in 1982, Congress affirmed that the Federal Government is responsible for the permanent disposal of spent nuclear fuel and high-level radioactive waste. In the 1987 amendments to the Act, Congress directed the Secretary of Energy to determine whether to recommend that the President approve the Yucca Mountain site for development of a repository for the permanent disposal of these materials.

S.2.2 BACKGROUND

When the DOE production reactors were operating, they used a controlled fission process to irradiate nuclear fuel and produce materials for nuclear weapons. After the spent nuclear fuel was removed from the reactors, chemical processes extracted the weapons-usable materials from the spent nuclear fuel. This is called reprocessing. [MATERIALS EVALUATED IN THIS EIS]

The byproduct remaining after reprocessing is high-level radioactive waste. High-level radioactive waste also resulted from the reprocessing of naval reactor fuels and some commercial reactor fuels, some DOE test reactor fuels, and some non-DOE research reactor fuels.

The Proposed Action includes disposal of spent nuclear fuel and high-level radioactive waste. In addition, DOE is responsible for the disposal of other waste types, referred to as Greater-Than-Class-C and Special-Performance-Assessment-Required wastes. These waste types are low-level radioactive wastes that have high radionuclide concentrations. They could become eligible for disposal in a geologic repository in the future, so DOE has analyzed the cumulative environmental impacts associated with the potential disposal of these wastes in a repository at Yucca Mountain.

S.2.2.1 Legislative History

The site characterization program consists of scientific, engineering, and technical studies and activities. Site investigations and evaluations include the construction of the Exploratory Studies Facility, which is a large underground laboratory consisting of a long tunnel or main drift and side tunnels and rooms inside the mountain; investigations of the hydrology and geology of the site; studies of socioeconomics, cultural resources, and terrestrial ecosystems; and monitoring of air quality, meteorological, radiological, and water resource data. [SITE CHARACTERIZATION OF YUCCA MOUNTAIN]

S.2.2.2 Related Activities and Decisions

If the Secretary recommends the Yucca Mountain site to the President, the NWPA requires that a comprehensive statement of the basis for the recommendation, including the Final EIS, accompany the recommendation. Since issuing the Draft EIS and the Supplement to the Draft EIS, DOE has issued several publicly available documents that would form part of this comprehensive statement. These documents address such topics as:

• Baseline postclosure models for Total System Performance Assessment

• Preliminary engineering specifications, including definitions of repository operating modes

• Preclosure safety analysis

• Sensitivity studies using alternative models and data

• Analyses of unquantified uncertainties

• Updates of scientific information and analysis of long-term performance of the lower-temperature repository operating mode

• Preliminary evaluation of the suitability of the Yucca Mountain site for a repository

• Yucca Mountain Science and Engineering Report: Technical Information Supporting Site Recommendation Consideration, May 2001

• Preliminary Preclosure Safety Assessment for Monitored Geologic Repository Site Recommendation, July 2001

• FY01 Supplemental Science and Performance Analysis, July 2001

• Yucca Mountain Preliminary Site Suitability Evaluation, August 2001

• Total System Performance Assessment-Analyses for Disposal of Commercial and DOE Waste Inventories at Yucca Mountain-Inputs to Final Environmental Impact Statement and Site Suitability Evaluation, August 2001.

Decision Process for U.S. Nuclear Regulatory Commission Licensing. If the Yucca Mountain site is approved, DOE will submit a License Application to the Nuclear Regulatory Commission for authorization to construct a geologic repository. The NWPA directs the Commission to adopt the Final EIS to the extent practicable in its decision on whether to issue a construction authorization and license for such a repository.

The Nuclear Regulatory Commission has issued requirements governing its licensing of DOE to construct a geologic repository and to receive and possess nuclear material at that repository (10 CFR Part 63). As mandated by law, these requirements are required to be consistent with the final standards for Yucca Mountain issued by the Environmental Protection Agency (40 CFR Part 197). Figure S-2 shows the sequence of past disposal decisions and projected activities.

S.3 Proposed Action and No-Action Alternative

DOE would dispose of spent nuclear fuel and high-level radioactive waste in the repository using the natural geologic features of the mountain and engineered barriers as a total system to help ensure the long-term isolation of the materials from the accessible environment. DOE would build the repository inside Yucca Mountain, at least 200 meters (660 feet) below the surface and at least 160 meters (530 feet) above the present-day water table. Figure S-3 shows the location of the proposed repository at Yucca Mountain.

In addition, the Proposed Action would include the use of active institutional controls (controlled access, inspection, and maintenance, etc.) through the end of the closure period, and the use of passive institutional controls (markers, engineered barriers, etc.) after the completion of closure. The purpose of the passive institutional controls would be to prevent inadvertent intrusion by and exposures to members of the public.

S.3.1.1 Repository and Waste Package Design

The Draft EIS evaluated the preliminary design concept described in the 1998 Viability Assessment of a Repository at Yucca Mountain. DOE recognized when it published the Draft EIS that plans for a repository would continue to evolve during any development of a final repository design and as a result of any licensing review of the repository by the Nuclear Regulatory Commission. Later, DOE issued the Supplement to the Draft EIS that evaluated the repository design described in the Yucca Mountain Science and Engineering Report: Technical Information Supporting Site Recommendation Consideration, which it issued in May 2001. The flexible design analyzed in the Supplement includes an improved understanding of the interactions of potential repository features with the natural environment, the addition of design features for enhanced waste containment and isolation, and evolving regulatory requirements. Rather than analyzing the three thermal load scenarios (high, intermediate, and low thermal loads) as in the Draft EIS, the Final EIS analyzes a range of operating modes (higher- to lower-temperature) for the flexible design. Because (1) thermal load is no longer the descriptive parameter for specifying thermal management scenarios for the proposed repository, and (2) an effort was made in the Final EIS to avoid confusion and to clarify the impacts of the Proposed Action, DOE has not carried the earlier thermal load scenarios through to the Final EIS. (A comparison between the thermal load scenarios and the repository operating modes for the flexible design is provided in the Supplement to the Draft EIS.) [FLEXIBLE DESIGN]

DOE would receive materials at the repository in one of three configurations: uncanistered fuel (spent nuclear fuel placed directly in a shipping cask), dual-purpose canisters (containers designed to store and transport commercial spent nuclear fuel), or disposable canisters (canisters for spent nuclear fuel or high-level radioactive waste with multiple specialized overpacks to enable their storage, transportation, and emplacement in a repository). All DOE materials (spent nuclear fuel and high-level radioactive waste) would be received in disposable canisters. Commercial spent nuclear fuel would be received in any of the three packaging configurations. DOE cannot predict the particular combination of uncanistered fuel, dual-purpose canisters, or disposable canisters it would receive at a repository because the managers of the commercial sites would determine the canister type, if any, they will use. For that reason, in the Draft EIS the Department analyzed two fuel packaging scenarios [mostly uncanistered and mostly canistered (including dual-purpose canisters and disposable canisters)] that cover the possible range of repository and transportation impacts to human health and the environment. DOE's analysis shows that the mostly uncanistered fuel packaging scenario would result in the highest short-term impacts, with the exception of (1) the empty dual-purpose canisters that some commercial sites could use that would require disposal or recycling, and (2) some attributes of offsite manufacturing of disposable canisters. To simplify the presentation in this Final EIS, the impacts throughout this document include those associated with the mostly uncanistered fuel packaging scenario, plus the impacts of the waste management and offsite manufacturing impacts, which are also included to represent potential impacts associated with the canistered scenario. This approach ensures that the impacts presented in this Final EIS would bound the impacts of any packaging scenario ultimately selected. [DEFINITIONS OF PACKAGING TERMS]

Material received at the repository would be unloaded from the shipping casks and placed in disposal containers called waste packages. To control the heat generation of the waste packages, the flexible design includes thermal blending of commercial spent nuclear fuel assemblies. Remote-controlled transporters would place the waste packages in emplacement drifts.

DOE considered waste packages containing two layers—a corrosion-resistant Alloy-22 shell on the outside and a stainless-steel inner shell to provide structural support. The highly corrosion-resistant outer material of the waste package would protect the underlying structural material from corrosive degradation, while the extremely strong internal structural material would support the thinner corrosion-resistant material. A drip shield of titanium (also extremely corrosion-resistant) with a nominal thickness of 1.5 centimeters (0.6 inch) would be placed over the waste packages during the closure phase. With the titanium drip shield and the Alloy-22 outer cylinder, there would be two different corrosion barriers protecting the waste from contact with water. Further, the use of two distinctly different corrosion-resistant materials would reduce the probability that a single mechanism could cause failure in both materials. The waste packages, together with the titanium drip shields, would be the primary part of an engineered barrier system in the repository. This system would, in combination with the natural features of this site, help slow the release of radioactive material to the accessible environment for long periods. [NATURAL AND ENGINEERED FEATURES]

Under the Proposed Action, DOE would emplace approximately 11,000 to 17,000 waste packages containing no more than 70,000 MTHM of spent nuclear fuel and high-level radioactive waste in the repository. Of that amount, 63,000 MTHM would be spent nuclear fuel assemblies that would be shipped from commercial sites to the repository. The remaining 7,000 MTHM would consist of about 2,333 MTHM of DOE spent nuclear fuel and the equivalent of 4,667 MTHM of high-level radioactive waste, currently estimated to be approximately 8,315 canisters, that DOE would ship to the repository from DOE sites. The inventory includes surplus weapons-usable plutonium. At present, DOE expects two-thirds of the plutonium would be converted into mixed-oxide fuel, which is included as part of the commercial spent nuclear fuel inventory. DOE expects the remaining third of the plutonium to be immobilized and included in the high-level radioactive waste inventory.

Figure S-5 shows potential waste package designs for commercial spent nuclear fuel. Figure S-6 shows waste packages in an emplacement drift.

S.3.1.2 Preconstruction Testing and Performance Confirmation, Construction, Operation and Monitoring, and Closure

Preconstruction Testing and Performance Confirmation. The preconstruction Testing and Performance Confirmation Program would continue many of the same types of activities performed during site characterization and would include tests, experiments, and analyses that DOE would conduct to evaluate the long-term performance of the repository. Before the start of repository construction, this program would assume responsibility for activities now being performed as part of site characterization. Those activities would continue until closure of the repository.

Construction. The construction of repository surface and subsurface facilities could begin after the receipt of construction authorization from the Nuclear Regulatory Commission. For analytical purposes, DOE assumed that construction would begin in 2005. The Department would build the repository surface facilities, main drifts, ventilation system, and initial emplacement drifts in about 5 years, from 2005 to 2010. Construction of the emplacement drifts would continue after emplacement began.

Surface facilities would receive, prepare, and package spent nuclear fuel and high-level radioactive waste for emplacement, and would support the construction of subsurface facilities. The primary surface facilities would be the North Portal Operations Area (including the Waste Handling Building and a surface aging facility if DOE employed aging of commercial spent nuclear fuel in conjunction with the lower-temperature repository operating mode), the South Portal Development Area (supporting subsurface facility development), and a 3-megawatt solar power generating facility that DOE would use to meet some of the electrical energy requirements of the repository.

Subsurface facilities would include the drifts developed during site characterization activities. During construction, additional underground excavation would occur. Excavation in the subsurface facilities would include gently sloping access ramps for the movement of construction and waste package vehicles, main drifts for the movement of construction and waste package vehicles, emplacement drifts for the placement of waste packages, exhaust mains to transfer air in the subsurface area, and ventilation shafts to transfer air between the surface and the subsurface. The higher-temperature repository operating mode would require three emplacement intake shafts, one development intake shaft, and three exhaust shafts to support the full emplacement of 70,000 MTHM. The lower-temperature repository operating mode could require three to seven emplacement intake shafts, one development intake shaft, and five to nine exhaust shafts. Performance confirmation drifts would contain instrumentation to monitor emplaced waste packages.

Operation and Monitoring. Repository operations would begin after the Nuclear Regulatory Commission granted a license to "receive and possess" spent nuclear fuel and high-level radioactive waste. For planning purposes, DOE assumed that the receipt and emplacement of these materials would begin in 2010. Based on a total emplacement of 70,000 MTHM at approximately 3,000 MTHM each year, waste emplacement would end after approximately 24 years.

Under the lower-temperature repository operating mode, DOE could place commercial spent nuclear fuel on a surface aging pad in Nuclear Regulatory Commission-licensed storage casks. This aging was assumed to occur during a 50-year period and would allow the heat generated by radioactive decay to be reduced before emplacing the waste packages into the repository.

The construction of emplacement drifts would continue for approximately 22 years during operation and monitoring. The repository design would enable simultaneous construction and emplacement operations, but it would physically separate construction or development activities from emplacement activities. Ventilation barriers would create airlocks to separate the emplacement and development sides of the repository, and the ventilation system would be designed to maintain the emplacement side at a lower pressure than the development side. This would ensure that no air leakage would occur from the emplacement side to the development side.

Monitoring and maintenance activities would begin with the first emplacement of waste packages and would continue until repository closure. The monitoring period, as defined for analytical purposes, would begin after the completion of emplacement. During the monitoring period, DOE would maintain the repository facilities, including the ventilation system and utilities (air, water, electric power) that would enable the continued monitoring and inspection of waste packages, continued investigations of long-term repository performance, and the retrieval of waste packages, if necessary. Immediately after the completion of emplacement, DOE would decontaminate and close the nuclear facilities on the surface to eliminate potential radioactive material hazards. However, the Department would maintain the Waste Handling Building for the possible retrieval of waste. [RETRIEVAL]

Closure. For the higher-temperature operating mode, the EIS analysis assumed repository closure would begin 100 years after the start of emplacement (76 years after the completion of emplacement) and would take 10 years. Repository closure for the lower-temperature operating mode would begin 125 to 300 years after the completion of emplacement and would take between 11 and 17 years, depending on the waste package spacing. The longer time required for the lower-temperature operating mode would ensure that the repository temperature would remain below boiling after closure.

Repository closure would occur after DOE received a license amendment from the Nuclear Regulatory Commission. Closure activities would include installing the titanium drip shields and closing the subsurface facilities, decommissioning the surface facilities, sealing openings into the mountain (access ramps, ventilation shafts, boreholes), performing reclamation activities at the site, and establishing institutional controls such as permanent monuments to mark and identify the area.

S.3.1.3 Transportation

The mostly legal-weight truck scenario assumes that DOE would transport most of the spent nuclear fuel and high-level radioactive waste to the repository by legal-weight truck. The trucks would travel from the 77 sites to the Yucca Mountain site primarily on the U.S. Interstate Highway system, as shown in Figure S-10. An exception to this scenario would be the naval spent nuclear fuel, which the Navy would transport from the Idaho National Engineering and Environmental Laboratory to Nevada by rail, as decided in the Record of Decision for a Dry Storage Container System for the Management of Naval Spent Nuclear Fuel.

The mostly rail scenario assumes that DOE and the Navy would transport most of the spent nuclear fuel and high-level radioactive waste to Nevada by rail, with the exception of material from commercial nuclear generating sites that initially would not have the capability to load large-capacity rail shipping casks. Those sites would use legal-weight trucks to ship material to the repository. Commercial sites with the capability to load the rail shipping casks but that did not have rail access could use heavy-haul trucks or barges to ship spent nuclear fuel to the nearest rail line. Figure S-11 shows the commercial and DOE sites and Yucca Mountain in relation to the U.S. railroad system over which the railcars could travel. [DEFINITIONS FOR TRUCK TRANSPORTATION]

In the State of Nevada, waste that traveled from the commercial and DOE sites by legal-weight truck would continue to the repository in the same manner. Figure S-12 shows the southern Nevada highways over which the legal-weight trucks could travel. Potential routes for legal-weight truck shipments in Nevada comply with U.S. Department of Transportation regulations (49 CFR 397.101) for selecting "preferred routes" and "delivery routes" for motor carrier shipments of Highway Route-Controlled Quantities of Radioactive Materials. Based on these regulations, those shipments would arrive in Nevada on Interstate-15, travel over the planned Las Vegas Beltway, and then proceed north on U.S. Highway 95 to Yucca Mountain. The State of Nevada could designate alternative routes as specified in 49 CFR 397.103. [REPOSITORY ANALYSIS]

At this time there is no rail access to the Yucca Mountain site. This means that material traveling by rail would have to continue to the repository on a new branch rail line or transfer to heavy-haul trucks at an intermodal (that is, from rail to truck) transfer station in Nevada and then travel on existing highways that could need to be upgraded. DOE is considering implementing alternatives for the construction of either a new branch rail line or an intermodal transfer station with associated highway improvements. The Department has identified five alternatives for rail corridors, each of which has alignment variations (Figure S-13), and three alternative locations for an intermodal transfer station and five associated highway routes for heavy-haul trucks (Figure S-14). Figure S-15 shows how the national and Nevada transportation scenarios relate.

S.3.1.4 Costs

S.3.2 NO-ACTION ALTERNATIVE

• Scenario 1 assumes that spent nuclear fuel and high-level radioactive waste would remain at the 72 commercial and 5 DOE sites under institutional control for at least 10,000 years.

• Scenario 2 assumes that spent nuclear fuel and high-level radioactive waste would remain at the 77 sites in perpetuity, but under institutional control for only about 100 years. This scenario assumes no effective institutional control of the stored spent nuclear fuel and high-level radioactive waste after 100 years. [INSTITUTIONAL CONTROL]

DOE recognizes that neither scenario would be likely if there were a decision not to develop a repository at Yucca Mountain; however, they are part of the EIS analysis to provide a basis for comparison to the Proposed Action. There are a number of possibilities that the Nation could pursue, including continued storage of the material at its current locations or at one or more centralized location(s); the study and selection of another location for a deep geologic repository; development of new technologies; or reconsideration of other disposal alternatives to deep geologic disposal. One such centralized storage possibility, the proposed Private Fuel Storage Facility for commercial spent nuclear fuel in Utah, is currently in the Nuclear Regulatory Commission licensing process. The Commission issued a Final EIS in January 2002, however, that document was unavailable for use during the preparation of this Final EIS. The Commission has yet to issue a decision on whether to grant a license. Under any future course that would include continued storage, both commercial and DOE sites have an obligation to continue managing the spent nuclear fuel and high-level radioactive waste in a manner that protects public health and safety and the environment.

S.3.2.1 Reclamation and Decommissioning at Yucca Mountain

Figure S-16 shows conceptual timelines for activities at the commercial and DOE sites for Scenarios 1 and 2.

S.4 Issues Raised by the Public

S.4.2 Issues Raised on the Draft EIS and the Supplement to the Draft EIS

• Nuclear Waste Policy Act - Why is Yucca Mountain the only site that DOE is studying?

  The Nuclear Waste Policy Act of 1982 provided for a process for selecting sites for technical study as potential geologic repository locations. In accordance with this process, DOE identified nine candidate sites, the Secretary of Energy nominated five of the nine sites for further consideration, and DOE issued environmental assessments for the five sites. DOE recommended three of the five sites, of which Yucca Mountain was one, for possible study as candidate repository sites. In 1987, Congress amended the Nuclear Waste Policy Act of 1982, directing the Secretary of Energy to perform site characterization activities only at the Yucca Mountain site, and, if the site was found suitable, to make a determination whether to recommend that the President approve the site for development of a repository.

• DOE's site suitability guidelines - Why did DOE change its guidelines for determining the suitability of the Yucca Mountain site?

  The Nuclear Waste Policy Act of 1982 directed the Secretary of Energy to issue general guidelines for the recommendation of sites for characterization, in consultation with certain Federal agencies and interested governors, and with the concurrence of the Nuclear Regulatory Commission. These guidelines (issued in 1984 at 10 CFR Part 960) included factors related to the comparative advantages among candidate sites located in various geologic media, and other considerations such as population density and distribution.

  In 1987, amendments to the Nuclear Waste Policy Act specified Yucca Mountain as the only site DOE was to characterize. For this reason, DOE proposed in 1996 to clarify and focus its 10 CFR Part 960 guidelines to apply only to the Yucca Mountain site. In 1999, DOE proposed further revisions to these guidelines principally to reflect the then-proposed regulations and criteria of the Environmental Protection Agency (40 CFR Part 197) and the Nuclear Regulatory Commission (10 CFR Part 63), and to provide a technical basis to assess the performance of a geologic repository at Yucca Mountain to isolate spent nuclear fuel and high-level radioactive waste from the environment.

  In 2001, DOE promulgated its final guidelines (10 CFR Part 963), establishing the methods and criteria to determine the suitability of the Yucca Mountain site for the location of a geologic repository. The Final EIS describes these final guidelines.

• Repository design - Why design a repository that would release radioactive materials into the environment?

  Given the current state of technology, it is virtually impossible to design and construct a geologic repository that would provide a reasonable expectation that there would never be any releases of radioactive materials. DOE would design and construct a repository that would meet public health and safety radiation protection standards and criteria established by the EPA and the NRC. In part, the EPA standards (40 CFR Part 197) and NRC criteria (10 CFR Part 63) prescribe radiation exposure limits that the repository, based on a performance assessment, must be designed not to exceed during a 10,000-year period after closure.

  In the EIS, DOE has evaluated the environmental impacts of the proposed repository's natural and engineered barrier system, which is designed to isolate radioactive materials from the environment for thousands of years. As a result of this evaluation, DOE would not expect the repository to result in impacts to public health beyond those that could result from the prescribed radiation exposure and activity concentration limits during the 10,000-year period after closure.

• Public participation process - Commenters stated that the public comment processes for scoping, the Draft EIS, and the Supplement to the Draft EIS were inadequate.

  DOE's public involvement process during the development of the EIS is consistent with Council on Environmental Quality and DOE regulations implementing NEPA, and reflects DOE guidance on public participation during the preparation of EISs.

  For the scoping process and in advance of the Notice of Intent, DOE notified its stakeholders of its plans to prepare the EIS and its approach to the scoping process. When the Notice of Intent was published in the Federal Register, DOE mailed a series of information releases to stakeholders, sent press releases and public service announcements to the media, and provided information on the Internet and in its reading rooms. Fifteen public scoping meetings were held during a 120-day public scoping period.

  In August 1999, DOE distributed the Draft EIS to more than 3,400 stakeholders and held 21 public hearings across the Nation during a 199-day public comment period. DOE placed advertisements in local newspapers and distributed public service announcements and press releases to more than 175 local and national stakeholder and media outlets to publicize information about the Draft EIS and public comment process.

  In May 2001, DOE distributed the Supplement to the Draft EIS to more than 4,000 stakeholders and held three public hearings in Nevada during the 57-day public comment period. During this period, the Department discovered that it had inadvertently not sent the Supplement to about 700 stakeholders who had requested and received a copy of the Draft EIS. DOE acknowledged this oversight, provided copies of the Supplement to the Draft EIS, and provided a separate 45-day comment period for these stakeholders.

  In Volume III of this EIS, DOE has presented and responded to all comments on the Draft EIS and the Supplement to the Draft EIS received by August 31, 2001.

• Need for another Draft EIS or a Supplemental EIS - The Draft EIS did not provide sufficient information or analysis and, thus, was deficient and should be withdrawn.

  The level of information and analyses, the analytical methods and approaches used to represent conservatively the reasonably foreseeable impacts, and the use of bounding assumptions to address incomplete or unavailable information or uncertainties provide an assessment of environmental impacts consistent with all applicable requirements.

  The EIS, which DOE prepared using the best reasonably available data, analyzes a variety of implementing alternatives and scenarios. These alternatives and scenarios reflect potential repository design and operating modes, waste packaging approaches, and transportation options for shipping spent nuclear fuel and high-level radioactive waste to the Yucca Mountain site. DOE included a No-Action Alternative that analyzed two scenarios to provide a basis for comparison with the Proposed Action and to reflect the range of impacts that could occur.

  In the Draft EIS, DOE discussed ongoing site characterization activities and design evaluations, and the potential for resulting changes to repository design. Since the publication of that document, DOE improved its understanding of the interactions of potential repository features with the natural environment, and the advantages of a number of design features to enhance waste containment and isolation. DOE published the Supplement to the Draft EIS to address the most recent design enhancements, including various operating modes to manage heat generated by emplaced spent nuclear fuel and high-level radioactive waste.

  This Final EIS evaluates the Proposed Action based on the design considered in the Supplement to the Draft EIS.

• Range of alternatives - DOE should have considered a range of alternatives, such as other sites, treatment technologies, and alternatives to geologic disposal.

  In 1980, DOE evaluated alternatives to mined geologic disposal in an EIS, and decided in 1981 in the subsequent Record of Decision to develop mined geologic repositories for the disposal of spent nuclear fuel and high-level radioactive waste. Furthermore, the NWPA provides that DOE need not consider in this EIS the need for a geologic repository and alternatives to isolating spent nuclear fuel and high-level radioactive waste in a repository. The NWPA also provides that this EIS does not have to consider any site other than Yucca Mountain for development as a repository. For these reasons, DOE did not analyze alternatives other than the Proposed Action and the No-Action Alternative.

• The Proposed Action - DOE has failed to define its Proposed Action clearly.

  In response to this concern, DOE has modified the EIS to promote an improved understanding of the potential environmental impacts from a more specifically defined Proposed Action. DOE has identified its preferred alternatives, simplified aspects of the Proposed Action, and modified its analyses and presentation of information to illustrate the full range of potential environmental impacts that could occur under any reasonably foreseeable repository design and operating mode or mode of transportation.

• Preferred alternative - DOE should identify its preferred alternatives and scenarios.

  In the Draft EIS, DOE indicated its preferred alternative was to proceed with the Proposed Action to construct, operate and monitor, and eventually close a repository for the disposal of spent nuclear fuel and high-level radioactive waste at Yucca Mountain. In this Final EIS, DOE has identified mostly rail as its preferred mode of transportation, both nationally and in the State of Nevada.

  DOE has not identified a preference among the five candidate rail corridors in Nevada. If the Yucca Mountain site was approved, DOE would issue at some future date a Record of Decision to select a mode of transportation. If, for example, mostly rail was selected (both nationally and in Nevada), DOE would then identify a preference for one of the rail corridors in consultation with affected stakeholders, particularly the State of Nevada.

  DOE has not identified other preferences under the various scenarios presented in this Final EIS. Specific details of operating the repository and related features would be resolved only in the context of developing a License Application for review by the NRC.

• No-Action Alternative - Why did DOE evaluate a No-Action Alternative that includes unreasonable scenarios?

  If the Yucca Mountain site was not approved, DOE would, as required by the NWPA, prepare a report to Congress, with the Department's recommendations for further action to ensure the safe, permanent disposal of spent nuclear fuel and high-level radioactive waste, including the need for new legislative authority. In this event, the generator sites, commercial utilities, and DOE would have to continue managing spent nuclear fuel and high-level radioactive waste in a manner that protected public health and safety and the environment. However, the future course that Congress, DOE, and the commercial utilities would take is uncertain, and a number of possibilities could be pursued.

  In light of these uncertainties, DOE decided to illustrate the range of potential environmental impacts by analyzing two No-Action Alternative scenarios that could occur without additional legislation—long-term storage of spent nuclear fuel and high-level radioactive waste at the current sites with effective institutional control for at least 10,000 years, and long-term storage with no effective institutional control after about 100 years. Although the Department agrees that neither of these scenarios is likely, it selected them for analysis because they provide a basis for comparison to the impacts of the Proposed Action and because they reflect a range of the impacts that could occur.

• Decisionmaking - DOE cannot base decisions on this EIS.

  DOE believes that the EIS adequately analyzes the potential environmental impacts that could result from the Proposed Action. This belief is based on the level of information and analysis, the analytical methods and approaches used to represent conservatively the reasonably foreseeable impacts, and the use of bounding assumptions where information is incomplete or unavailable, or where uncertainties exist.

  For the same reasons, if the site was approved, DOE believes that the EIS provides the environmental impact information necessary to make certain broad transportation-related decisions, namely the choice of a national mode of transportation outside Nevada (mostly rail or mostly legal-weight truck), the choice among alternative transportation modes in Nevada (mostly rail, mostly legal-weight truck, or heavy-haul truck with use of an associated intermodal transfer station), and the choice among alternative rail corridors or heavy-haul truck routes with use of an associated intermodal transfer station in Nevada. However, follow-on implementing decisions, such as the selection of a specific rail alignment in a corridor, would require additional NEPA reviews.

• Premature decisionmaking - DOE has decided to recommend the Yucca Mountain site in advance of the Final EIS and other documentation.

  At the time DOE prepared this Final EIS, it had not made a decision on the proposed repository at Yucca Mountain. The Secretary of Energy will make a determination on whether to recommend the site to the President on the basis of a number of different types of information, including that contained in the Final EIS. Any recommendation would be accompanied not only by the Final EIS, but also by other information designated in the NWPA.

• Population data - Why does DOE use outdated population data?

  When DOE prepared the Draft EIS, it based the Nevada population estimates on the then-most-recently available information (1996-1997) from the U.S. Bureau of the Census. The Department used these data in its economic and demographic forecasting model to project population growth in the regions of influence and to evaluate socioeconomic impacts from the Proposed Action. For its transportation health and safety analyses, however, DOE relied on 1990 population data, which were the then-most-recent data incorporated in the standard models used for such analyses.

  In response to comments and recently available information, DOE has updated its population estimates in the regions of influence to reflect the most recent state and local information, as well as the Bureau of the Census 2000 population summary data for Nevada. To update the health and safety analyses associated with transportation in Nevada, DOE used the baseline population for each county in the region of influence and forecast the population to 2035 and scaled the impacts accordingly. To update the health and safety analyses on a national basis, DOE scaled the 1990 population-based impacts upward to reflect the relative state-by-state population growth to 2035. The projections are based on 2000 Census data.

• Risk perception and stigma - Why didn't DOE analyze the impacts associated with the negative perceptions attached to a potential repository at Yucca Mountain?

  During scoping for the EIS, DOE received comments saying the EIS should analyze perception-based and stigma-related impacts. Perception-based impacts would not necessarily depend on the actual physical impacts or risks from repository operations or transportation. Further, people do not consistently act in accordance with negative perceptions, and thus the connection between public perception of risk and future behavior would be uncertain or speculative at best. For these reasons, DOE determined that including analyses of perception-based and stigma-related impacts in the Draft EIS would not provide meaningful information.

  Nevertheless, in light of the comments received on the Draft EIS, DOE commissioned an examination of relevant studies and literature on perceived risk and stigmatization of communities to determine whether the state of the science in predicting future behavior, based on perceptions, had advanced sufficiently to allow DOE to quantify the impact of public risk perception on economic development or property values. Based on this examination, DOE has concluded that:

  1. While in some instances risk perceptions could result in adverse impacts on portions of a local economy, there are no reliable methods whereby such impacts could be predicted with any degree of certainty,

  2. Much of the uncertainty is irreducible, and

  3. Based on a qualitative analysis, adverse impacts from perceptions of risk would be unlikely or relatively small.

  While stigmatization of southern Nevada can be envisioned under some scenarios, it is not inevitable or numerically predictable. Any such stigmatization would likely be an aftereffect of unpredictable future events, such as serious accidents, which are not anticipated to occur. As a consequence, DOE did not attempt to quantify any potential for impacts from risk perceptions or stigma in this Final EIS.

• Native American viewpoints – DOE did not adequately consider Native American viewpoints or incorporate these viewpoints in the analyses and resulting conclusions.

  DOE believes that it appropriately considered Native American viewpoints by incorporating in the EIS the Native Americans' own identification of potential impacts to historic and other cultural resources important to sustaining and preserving their cultures. During the preparation of the EIS, DOE supported the American Indian Writers Subgroup of the Consolidated Group of Tribes and Organizations in its preparation of a separate report, the results of which are included in the EIS.

  Based on the results of the report, DOE acknowledges in the EIS that people from many Native American tribes have used the area proposed for the repository as well as nearby lands; that the lands around the site contain cultural, animal, and plant resources important to those tribes; and that the implementation of the Proposed Action would continue restrictions on free access to the area around the repository site. Furthermore, the presence of a repository would represent an intrusion into what Native Americans consider an important cultural and spiritual area. These concerns notwithstanding, DOE and the Consolidated Group of Tribes and Organizations recognize that restrictions on public access to the area have been generally beneficial and protective of cultural resources, sacred sites, and traditional cultural properties.

• Ruby Valley Treaty - DOE should honor the Ruby Valley Treaty of 1863 with the Western Shoshone Nation.

  The Western Shoshone people maintain that the Ruby Valley Treaty of 1863 gives them rights to 97,000 square kilometers (37,000 square miles) in Nevada, including the Yucca Mountain region. In 1977, the Indian Claims Commission granted a final award to the Western Shoshone people, who dispute the Commission's findings and have not accepted the monetary award for the lands in question. In 1985, the Supreme Court ruled that even though the money has not been distributed, the United States has met its obligations with the Indian Claims Commission's final award and, as a consequence, the aboriginal title to the land has been extinguished.

• Approach to environmental justice transportation analysis - DOE's two-staged assessment process masks significant impacts to minorities and low-income populations, and its failure to identify either specific locations or specific characteristics of affected communities demonstrates the inadequacy of the analysis.

  The approach to environmental justice analysis in this EIS is consistent with the Council on Environmental Quality guidance. The goal of this approach is to identify whether any high and adverse impacts would fall disproportionately on minority and low-income populations. The approach first analyzes the potential impacts on the general population as a basis for comparison. Second, based on available information, the approach assesses whether there are unique exposure pathways, sensitivities, or cultural practices that would result in high and adverse impacts on minority and low-income populations. If high and adverse impacts on a minority or low-income population would not appreciably exceed the same type of impacts on the general population, no disproportionately high and adverse impacts would be expected.

  In response to comments, DOE has reevaluated available information to determine whether the Draft EIS overlooked any unique exposure pathways or unique resource uses that could create opportunities for disproportionately high and adverse impacts to minority and low-income populations. Although DOE identified additional unique pathways and resources, none revealed a potential for disproportionately high and adverse impacts.

  DOE also updated and refined information germane to its environmental justice analysis. Based on the additional information and resulting analysis, DOE has concluded that disproportionately high and adverse impacts from the construction and operation of a rail line or intermodal transfer station would be unlikely.

• Rail and highway routes - Why didn't DOE identify the specific rail and highway routes that would be used to ship spent nuclear fuel and high-level radioactive waste?

  Because it is impossible to predict which highway routes or rail lines DOE could use in advance of actual shipments, the Department selected potential highway routes for analysis in accordance with U.S. Department of Transportation regulations, which require the use of preferred routes (typically highways and bypasses that are part of the Interstate Highway System). The Department based its selection of potential rail routes on current rail practices, because there are no comparable Federal regulations applicable to the selection of rail routes for the shipment of radioactive materials.

  In response to public comments, DOE has included maps of the representative highway routes and rail lines it used for analysis in the Final EIS. It also included potential health and safety impacts associated with shipments for each state through which shipments could pass.

• Transportation public health and safety impacts - The transportation-related health and safety analysis was inadequate because DOE did not consider community-by-community population characteristics.

  DOE does not believe that it is necessary or appropriate to consider population characteristics on a community-by-community basis to determine potential public health and safety impacts from the transportation of spent nuclear fuel and high-level radioactive waste. The use of widely accepted analytic tools, latest reasonably available information, and cautious but reasonable assumptions if there are uncertainties, offer the most appropriate means to arrive at conservative estimates of transportation-related public health impacts.

  In this EIS, DOE used computer models it has used in previous EISs and other studies. These models, such as RADTRAN 5, are widely accepted by the national and international scientific and regulatory communities.

  In addition, DOE has either incorporated information that has become available since the publication of the Draft EIS or modified existing information to accommodate conditions likely to be encountered over the life of the Proposed Action. For example, in this Final EIS DOE has scaled impacts upward to reflect the relative state-by-state population growth to 2035, using 2000 Census data.

  Not all aspects of incident-free transportation or accident conditions can be known with absolute certainty, and so DOE has relied on conservative assumptions that tend to overestimate impacts. For instance, DOE assumed that a hypothetical individual, the "maximally exposed individual," would be a resident living 30 meters (100 feet) from a point where all truck shipments would pass (this individual would receive a dose of about 6 millirem). Although it can be argued that individuals could live closer to these shipments, it is highly unlikely that an individual would be exposed to all shipments over the 24-year period of shipments to the repository, even though DOE incorporated this highly conservative assumption in the analysis.

  In response to comments, DOE has considered locations at which individuals could reside nearer the candidate rail corridors and heavy-haul truck routes in Nevada as a way of representing conditions that could exist anywhere in potentially affected communities. For example, an individual residing as close as 4.9 meters (16 feet) to a potential heavy-haul truck route would receive an estimated dose of about 29 millirem if exposed to all shipments.

  The doses from these exposures would be well below those received from natural background radiation and would not be discernible even if the doses could be measured.

• Transportation accident conditions - Why didn't DOE analyze a range of accidents that reflect real-life conditions?

  "Real-life conditions" that would involve various types of collisions, various natural disasters, specific locations (such as mountain passes), or various infrastructure accidents (such as track failure) in effect constitute a combination of cask failure mechanisms, impact velocities, and temperature ranges, which the EIS does evaluate. Accident scenarios are modeled in this fashion to accommodate the almost infinite number of variables that any given accident could involve. In the Draft EIS, for example, DOE evaluated the ability of large aircraft components (engines and engine shafts) to penetrate shipping casks. DOE considered both small military aircraft and commercial aircraft at velocities representative of takeoffs and landings and at higher velocities. DOE found that, at lower velocities, these aircraft components would not penetrate a shipping cask sufficiently to cause a release of radioactive materials. Recent analysis of this event at higher velocities, however, indicate an increased potential for seal failure of the shipping casks. If seal failure were to occur, impacts to an urban area would be less than 1 latent cancer fatality in the exposed population.

  Based on its revised analyses, DOE has concluded in the EIS that casks would continue to contain spent nuclear fuel fully in more than 99.99 percent of all accidents (of the thousands of shipments over the last 30 years, none has resulted in an injury due to release of radioactive materials). This means that of the approximately 53,000 truck shipments, there could be 66 accidents, each having less than a 0.01-percent chance that radioactive materials would be released. The chance of a rail accident that would cause a release from a cask would be even less. The corresponding chance that such an accident would occur in any particular locale would be extremely low.

• Cask testing - Will DOE conduct full-scale testing of transportation casks?

  The NWPA requires DOE to use casks certified by the NRC when transporting spent nuclear fuel and high-level radioactive waste to a repository. A cask's ability to survive the tests prescribed by the regulations (10 CFR Part 71) can be demonstrated either through component analysis or through scale-model and full-scale testing to demonstrate and confirm the performance of the casks. The NRC would decide which level of physical testing or analysis was appropriate for each cask design submitted.

• Repository design - Why didn't DOE analyze the latest design in the Draft EIS?

  In the Draft EIS, DOE evaluated a preliminary design that focused on the amount of spent nuclear fuel (and associated thermal output) that DOE would emplace per unit area of the repository (called areal mass loading). Areal mass loading was represented in the Draft EIS by three thermal load scenarios. The purpose of these scenarios was not to place a limit on the choices among alternative designs because, as stated in the Draft EIS, DOE expected the repository design to continue to evolve in response to ongoing site characterization and design-related evaluations. Rather, DOE selected these analytical scenarios to represent the range of foreseeable design features and operating modes, and to ensure that it considered the associated range of potential environmental impacts.

  Since issuing the Draft EIS, DOE has continued to evaluate design features and operating modes. The result of the design evolution process was the development of the flexible design (which the Supplement to the Draft EIS called the Science and Engineering Report Flexible Design). Although this design focuses on controlling the temperature of the rock between the waste emplacement drifts (as opposed to areal mass loading), the basic elements of the Proposed Action to construct, operate and monitor, and eventually close a geologic repository at Yucca Mountain remain unchanged since the Draft EIS.

• Hydrologic setting - DOE lacks an understanding of the hydrologic setting and should continue to study the site and surrounding region before making any decisions.

  DOE believes that it has sufficient information and understanding of the hydrologic setting to make an adequate determination of the potential environmental impacts from the Proposed Action. DOE, the U.S. Geological Survey, and others have been evaluating and assessing the hydrologic setting and associated characteristics at the Yucca Mountain site and nearby region for more than two decades. During this time, DOE has modified its site characterization program to reflect new information and assessments and to accommodate reviews by independent parties. Nevertheless, DOE recognizes that additional information would refine its understanding of the regional groundwater flow system, and would reduce uncertainties associated with flow and transport in the alluvial, volcanic, and carbonate aquifers.

  To obtain additional information, DOE has supported Nye County in the Early Warning Drilling Program to characterize further the saturated zone along possible groundwater pathways from Yucca Mountain as well as the relationships among the volcanic, alluvial, and carbonate aquifers. DOE also has installed a series of test wells along the groundwater flow path between the Yucca Mountain site and the Town of Amargosa Valley as part of an alluvial testing complex.

  After completion of site characterization, DOE would institute a Testing and Performance Confirmation Program, elements of which would address the hydrologic system. The program would continue through closure of the repository.

• Site disqualification - The Yucca Mountain site should be disqualified under 10 CFR Part 960 because subsurface fracturing would allow contaminated groundwater to reach the environment in less than 1,000 years.

  DOE's original 1984 site suitability guidelines (10 CFR Part 960) have been superseded by Yucca Mountain-specific guidelines (10 CFR Part 963) promulgated by DOE in 2001. In any event, information and analyses do not support a finding that the site would have been disqualified under the groundwater travel time disqualifying condition at 10 CFR 960.4-2-1(d). Under that condition, a site would be disqualified if the expected groundwater travel time from the disturbed zone (the area in which properties would change from construction or heat) to the accessible environment would be less than 1,000 years along any pathway of likely and significant radionuclide travel. The definition of groundwater travel time in 10 CFR 960.2 specifies that the calculation of travel time is to be based on the average groundwater flux (rate of groundwater flow) as a summation of travel times for groundwater flow in discrete segments of the system. As a practical matter, this definition provides for consideration of the rate at which most of the water moves.

  DOE estimates that the median groundwater travel times would be about 8,000 years, and average groundwater travel times would be longer. These models indicate that small amounts of water potentially moving in "fast paths" from the repository to the accessible environment could do so in less than 1,000 years. However, the models and corroborating physical evidence indicate that most of the water would take more than 1,000 years to reach the accessible environment. Given this, DOE believes that the site would not have been disqualified under the groundwater travel condition at 10 CFR 960.4-2-1.

• Repository performance - How can DOE possibly predict repository performance given data uncertainties, untested computer models, and the chaotic nature of the long-term processes?

  DOE acknowledges that it is not possible to predict with absolute certainty what will occur thousands of years into the future. The NRC regulations (see 10 CFR Part 63) acknowledge that absolute proof is not to be had in the ordinary sense of the word, and the EPA has determined (see 40 CFR Part 197) that reasonable expectation, which requires less than absolute proof, is the appropriate test of compliance.

  DOE has designed its performance assessment to be a combination of mathematical modeling, and natural analogs. Performance assessment explicitly considers the spatial and temporal variability and inherent uncertainties in geologic, biologic, and engineered components of the disposal system. In this way, DOE is confident that its approach to performance assessment addresses and compensates for various uncertainties, and provides a reasonable estimation of potential impacts over thousands of years.

• Disruptive natural phenomena - Commenters stated that earthquakes and volcanoes will cause releases of radioactive waste.

  DOE has analyzed the potential public health and safety impacts that could arise from natural events such as earthquakes and volcanic activity. The disruptive natures of earthquakes and volcanic activity differ materially, both in terms of probabilities (likelihood of occurrence) and the possible disruptive nature of the events themselves. Volcanism over the long-term life of the repository, with eruptions and magma flow, would be highly unlikely, while seismic activity and its consequent ground motion would be more likely to occur.

  While the occurrence of events cannot be predicted exactly, risks can be estimated statistically. Computer simulations allow DOE to estimate risks from natural events. Thus, the EIS contains an analysis of the probabilities and effects of such events on radionuclide release, and the resultant potential human health impacts to the public.

  Although DOE would design repository structures to withstand the ground movement associated with severe earthquakes, it estimated the impacts that could result from a "beyond-design-basis" seismic event that would result in the collapse of the Waste Handling Building and consequent damage to spent nuclear fuel assemblies. DOE determined the resulting impacts associated with this scenario would be small (primarily due to the physical form of the assemblies, reduced releases due to the building rubble, and distance to the nearest population). The underground engineered barriers would be far less susceptible to damage.

  DOE also estimated the impacts of volcanic eruptions that could result in the release of volcanic ash and entrained waste into the atmosphere. DOE estimated the potential impacts on the nearest population, conservatively assuming (tending to overestimate) the direction and speed of wind transport of an ash plume, and determined that the potential for public health and safety impacts would be very small. DOE also determined that magma flows would have minimal impacts on the long-term performance of the repository.

S.4.3 Changes Made in the Final EIS

• More information regarding potential impacts, particularly impacts associated with transportation of spent nuclear fuel and high-level radioactive waste within Nevada

• Use of a "representative" fuel assembly in the accident analysis

• Use of updated data, particularly population data in the impact analyses

• A more detailed discussion of the issue of potential impacts associated with negative perceptions about the repository project

• Use of updated versions of computer models for assessing human health and transportation impacts

• Corrections or editorial changes for accuracy and clarity

• Addition of an appendix that contains general information about transportation of radioactive materials not specifically used in the analysis, but provided for public information

• Addition of the U.S. Fish and Wildlife Service Biological Opinion as an appendix to the Final EIS

• Addition of a Readers Guide to help readers understand the Final EIS

As stated in the Supplement to the Draft EIS, "The fundamental aspects of the repository have not changed." The differences in environmental impacts due to the changes noted above were minor. In most environmental resource areas, the impacts either stayed the same or were smaller than those presented in the Draft EIS or the Supplement to the Draft EIS. In those cases where the impacts were larger than previously presented (generally driven by the larger population used for analysis in the Final EIS), the increases were not materially larger.

S.5 Environmental Consequences of the Proposed Action

DOE conducted a broad range of studies to obtain or evaluate the information needed for the assessment of Yucca Mountain as a geologic repository. These studies have provided in-depth knowledge about the Yucca Mountain site and vicinity and provide sufficient information to aid in DOE decisionmaking. The Department used the information from these studies in the analyses described in this EIS. However, because some of these studies are ongoing, some of the information is incomplete. Further, the complexity and variability of the natural system at Yucca Mountain, the long period evaluated (10,000 years), and incomplete information or the unavailability of some information have resulted in uncertainty in the analyses and findings. Throughout the EIS, DOE notes both the use of incomplete information if complete information is unavailable, and the existence of uncertainty, to enable the reader to better understand EIS findings.

The following paragraphs describe the potentially affected resources at the Yucca Mountain site and vicinity and a summary of the extent to which the Proposed Action could affect those resources.

S.5.1 YUCCA MOUNTAIN SITE and vicinity

The Yucca Mountain site is on Federal land in a remote area of the Mojave Desert in Nye County in southern Nevada, about 160 kilometers (100 miles) northwest of Las Vegas, Nevada. The Yucca Mountain region is sparsely populated and receives only about 170 millimeters (7 inches) of precipitation each year. The Yucca Mountain Repository land withdrawal area would occupy about 600 square kilometers (230 square miles or 150,000 acres) of land currently under the control of DOE, the Department of Defense (U.S. Air Force), and the Department of the Interior (Bureau of Land Management).

Surface repository facilities would occupy as much as 6.0 square kilometers (2.3 square miles or 1,500 acres) of the Yucca Mountain site. The remainder of the site would be used to locate support facilities, and for continued performance confirmation and testing activities (for example, wells) and to separate repository facilities from other human activities. Performance confirmation and testing activities would take place on and in the vicinity of the site. The existing environment at the site includes the structures and physical disturbances from DOE-sponsored activities that took place from 1977 to 1988 related to the selection of Yucca Mountain for site characterization, and continuing site characterization activities that began in 1989 to determine the suitability of the site for a repository.

S.5.1.1 Land Use and Ownership

State-owned lands are limited in the vicinity of the proposed repository. There are scattered tracts of private land in and near communities such as Beatty and Indian Springs in Nevada. There are larger private tracts in the agricultural areas of the Las Vegas Valley, near Pahrump, and in the south-central portion of the large area that makes up the Amargosa Valley community. The closest year-round housing is at the location formerly known as Lathrop Wells, about 22 kilometers (14 miles) south of the site. This location is now part of the unincorporated Town of Amargosa Valley. There are farming operations about 30 kilometers (19 miles) south of the proposed repository. Figure S-17 shows the land use and ownership in the Yucca Mountain region.

Only Congress has the power to withdraw Federal lands permanently for the exclusive purposes of specific agencies. If the Yucca Mountain site was approved for development as a repository, a permanent land withdrawal would be necessary to isolate the land designated for the site from public access to satisfy Nuclear Regulatory Commission licensing requirements. The EIS analysis assumed the use of an area of approximately 600 square kilometers (150,000 acres) on Bureau of Land Management, U.S. Air Force, and DOE lands in the vicinity of the proposed repository. Figure S-18 shows the land withdrawal area that DOE used for analytical purposes. Proposed Action activities would require the use of as much as about 6.0 square kilometers (1,500 acres) of noncontiguous areas within the 600-square-kilometer (150,000-acre) area. These activities would not conflict with land uses on adjacent lands.

S.5.1.2 Air Quality

Radiological Impacts. Radiological air quality impacts were evaluated as the radiation doses that could occur from airborne releases of radionuclides. The primary radionuclide released from Yucca Mountain would be naturally occurring radon-222 and its radioactive decay products. Releases of very small quantities of manmade radionuclides (krypton-85 and other noble gases) would occur only during the operations period, when spent nuclear fuel assemblies would be removed from transportation casks in the Waste Handling Building. [RADIATION]

The maximum annual dose to the maximally exposed individual member of the public would range from about 0.73 millirem per year to 1.3 millirem per year, depending on the operating mode. The range in dose is due primarily to the varying size of the repository, with a larger repository having higher radon release and resulting in higher dose. Greater than 99.99 percent of the annual dose would be from radon-222 and radon decay products. The preclosure Public Health and Environmental Standard found at 10 CFR 63.204 is 15 millirem per year to a member of the public. Maximum annual doses from repository activities would range from about 5 to 9 percent of this standard. The average individual in the United States receives 200 millirem per year from exposure to naturally occurring radon and its decay products, so Yucca Mountain releases would be expected to add less than 0.7 percent to the natural background dose from radon.

Radiation doses from radionuclides released to air were also estimated for the general population within 80 kilometers (50 miles) of the site, the maximally exposed noninvolved worker, and the noninvolved worker population at Yucca Mountain. There are no applicable air quality standards for these exposure groups and individuals. However, these radiation doses are used to estimate the potential human health impacts presented in Section S.4.1.7. Estimates of health impacts to members of the public are converted directly from these air quality dose estimates. The doses to noninvolved workers from airborne exposures would be very small compared to other occupational doses; therefore, the doses estimated here would contribute minimally to the estimates of health impacts to noninvolved workers presented in Section S.4.1.8.

S.5.1.3 Geology

DOE would build the proposed repository and emplace the waste packages in a mass of volcanic rock (welded tuff) known as the Topopah Spring Tuff. This formation was formed by a volcanic ash-flow from the calderas north of Yucca Mountain 12.8 million years ago and has not been disturbed by volcanic activity since then. The volcanic activity that produced these rocks is complete and, based on the geology of similar volcanic systems in the region, additional silicic volcanic activity would be unlikely. (Younger, small-volume basaltic volcanoes to the south, west, and northwest of Yucca Mountain have been the focus of extensive study by DOE.) DOE chose the Topopah Spring Tuff as the potential repository emplacement area because of (1) its depth below the ground surface that would protect nuclear materials from exposure to the environment, (2) its extent and characteristics that would enable the construction of stable openings and the accommodation of a range of temperatures, (3) its location away from major faults that could adversely affect the stability of underground openings and could provide pathways for water flow, eventually leading to radionuclide release, and (4) its location well above the present water table. [VOLCANISM]

North-trending seismic faults are the characteristic geological structural elements at Yucca Mountain. The Solitario Canyon Fault along the west side of Yucca Mountain and the Bow Ridge Fault along the east side are the major block-bounding faults that bracket the area under consideration for the proposed repository. The proposed repository has been configured such that there would be no block-bounding faults in the emplacement zone. Between the major north-trending, block-bounding faults there are intrablock or subsidiary faults. One intrablock fault, called the Ghost Dance Fault, is in the area of the proposed repository and one relatively short, northwest-trending subsidiary fault, the Sundance Fault, transects the area of the proposed repository. Studies at Yucca Mountain indicate that individual faults have very long recurrence intervals between the types of earthquakes that would be powerful enough to cause surface displacements. Strain can accumulate on these faults over long periods between surface-rupturing earthquakes. Little or no seismic activity might occur during this long strain buildup. [EARTHQUAKES]

DOE has monitored seismic activity at the Nevada Test Site since 1978. In 1992, an earthquake measuring 5.6 on the Richter scale occurred at Little Skull Mountain, about 20 kilometers (12 miles) southeast of Yucca Mountain. It caused no detectable damage in tunnels or characterization facilities at the Yucca Mountain site, but did cause some minor damage at the Field Office Center in Jackass Flats about 5 kilometers (3 miles) north of the epicenter.

S.5.1.4 Hydrology

Groundwater. The groundwater flow system of the Death Valley region is very complex, involving many groundwater basins, as shown in Figure S-20. Over distance, aquifers and confining units in the groundwater flow system vary in their characteristics or even their presence. In some areas, confining units allow considerable movement between aquifers; in other areas confining units are sufficiently tight to support artesian conditions (where water in a lower aquifer is under pressure in relation to water in an overlying aquifer).

Groundwater in aquifers below Yucca Mountain and in the surrounding region flows generally south toward discharge areas in the Amargosa Desert and Death Valley. This broad area is called the Death Valley regional groundwater flow system. The area around Yucca Mountain is in the central subregion of the Death Valley regional groundwater flow system, which has three groundwater basins: (1) Pahute Mesa-Oasis Valley, (2) Ash Meadows, and (3) Alkali Flat-Furnace Creek. [GROUNDWATER]

There is scientific uncertainty about the exact locations of the groundwater flow boundaries between the three groundwater basins in the central Death Valley subregion. All interpretations of the available data, however, place the aquifers below Yucca Mountain in the central Alkali Flat-Furnace Creek groundwater basin. In the region of influence for hydrology, the primary sources of groundwater recharge are infiltration on Pahute Mesa, Rainier Mesa, Timber Mountain, and Shoshone Mountain to the north, and the Grapevine and Funeral Mountains to the south. Recharge in the immediate Yucca Mountain vicinity is small in comparison and consists of water reaching Fortymile Wash as well as precipitation that infiltrates the surface. DOE studies indicate that the quantity of water that might move through a repository area of 10 square kilometers (2,500 acres), assuming 4.7 millimeters (0.2 inch) of infiltration per year, would be about 0.2 percent of the estimated 23.4 million cubic meters (19,000 acre-feet) that moves from the Amargosa Desert to Death Valley on an annual basis.

To pose a threat to groundwater during the construction, operation and monitoring, or closure phase of the Proposed Action, a contaminant such as a hazardous material would have to be spilled or released and then carried down either by its own weight or by infiltrating water. The depth to groundwater [at least 160 meters (530 feet)] and the arid environment would combine to reduce the potential for contaminant migration during the preclosure period of repository operations.

The most likely way to affect infiltration rates and, thus, groundwater recharge would be as the result of a land disturbance that caused additional runoff from the facilities to accumulate in areas like Fortymile Wash. That is, the additional runoff could increase groundwater recharge. However, given the dry climate and relatively small amount of potentially disturbed area in relation to the surrounding unchanged areas, the net change in infiltration would be small. After closure, the implementation of soil reclamation and revegetation would accelerate a return to more natural infiltration conditions.

DOE would meet the water demand for the Proposed Action by pumping from the groundwater in the Jackass Flats area. Estimates of perennial yield of the aquifer (the quantity of groundwater that can be withdrawn annually without depleting the reservoir, also referred to as safe yield) in the Jackass Flats area ranges from 1.1 million to 4.9 million cubic meters (880 to 4,000 acre-feet). The highest demand during the repository construction phase and the operation and monitoring phase [as high as 360,000 cubic meters (290 acre-feet) per year], added to the demand from ongoing Nevada Test Site activities, would be below the lowest estimate of the area's perennial yield.

Maximum repository water demands would occur during emplacement and development activities and, when combined with the baseline demands from Nevada Test Site activities, would approach (but still be below) the lowest perennial yield estimate. None of the water demand estimates would approach the high estimates of perennial yield.

S.5.1.5 Biological Resources and Soils

S.5.1.6 Cultural Resources

Studies have described several Native American sites, areas, and resources in or immediately adjacent to the analyzed land withdrawal area. DOE recognizes that Native Americans have concerns about protecting traditions and the spiritual integrity of the land in the Yucca Mountain region, and that these concerns extend to the propriety of the Proposed Action. The Consolidated Group of Tribes and Organizations in the area surrounding the Yucca Mountain site value the cultural resources in the area, viewing them in a holistic manner. They believe that the water, animals, plants, air, geology, sacred sites, and artifacts are interrelated and dependent on each other for existence. Because of the general level of importance attributed to the land by these Native Americans, and because they regard the land as part of an equally important integrated cultural landscape, these Native Americans consider the intrusive nature of the repository to be an adverse impact to all elements of the natural and physical environment. The establishment of the land withdrawal boundary and construction of the repository would continue to restrict their free access to these areas. Figure S-21 shows traditional boundaries and locations of tribes in the region.

S.5.1.7 Socioeconomics

S.5.1.8 Occupational and Public Health and Safety

Impacts to Workers from Industrial Hazards. Workers would be subject to industrial hazards during all phases of the Proposed Action. Examples of the types of industrial hazards that could present themselves include tripping, being cut on equipment or material, dropping heavy objects, and catching clothing in moving machine parts. Most impacts would be the result of fuel handling in the Waste Handling Building during the operations period. The next biggest component of industrial hazards would be the result of the subsurface excavation.

The estimated number of workplace fatalities from industrial hazards over the project life would range from 2.0 for the higher-temperature repository operating mode to between 2.2 and 3.3 for the lower-temperature operating mode.

Nonradiological Impacts to Workers and the Public. DOE would use engineering controls during subsurface work to control exposures of subsurface workers to dust that might contain cristobalite, a form of crystalline silica. If engineering controls could not keep dust concentrations below established limits, administrative controls such as respiratory protection would be used until engineered controls could reduce concentrations. Similar controls would be applied for surface workers if necessary. DOE expects that exposure of subsurface and surface workers to cristobalite would be well below applicable regulatory limits and that potential impacts to these workers would be low. Cristobalite concentrations at the site boundary would be small and unlikely to pose impacts to the public. [HEALTH AND SAFETY IMPACTS (AFFECTED INDIVIDUALS)]

Radiological Impacts to Workers. Radiological impacts to workers are reported both in terms of the increase in likelihood of a latent cancer fatality for an individual, and the increase in the total number of latent cancer fatalities for the total worker population. The probability of the maximally exposed worker incurring a latent cancer fatality from repository-related radiation exposure would range from about 0.0072 to 0.012 (7 to 12 chances in 1,000) for a 50-year working lifetime. The total estimated number of latent cancer fatalities that could occur in the repository workforce from the radiation dose received over the entire project would be about 4.0 for the higher-temperature repository operating mode. For the lower-temperature operating mode, the number of latent cancer fatalities would range from 4.4 to 6.8 for the project duration, depending on the length of time before closure. [LATENT CANCER FATALITIES]

About 70 percent of the radiological impacts to workers for the Proposed Action would occur during the operations period. The principal contributor to these operations impacts would be surface facility operations, which would involve receipt, handling, and packaging of spent nuclear fuel and high-level radioactive waste for emplacement. The second largest contributor to worker impacts would be subsurface monitoring, which would increase proportionately with the length of time monitoring would be carried out.

Preclosure Radiological Impacts to the Public. Short-term radiological health impacts to the public for Yucca Mountain construction, operation and monitoring, and closure would be small. (Impacts from transportation are discussed in Section S.4.2.) More than 99.9 percent of the potential health impact would be from naturally occurring radon-222 and its decay products released in exhaust ventilation air. The highest annual dose would range from 0.73 to 1.3 millirem, less than 1 percent of the annual 200-millirem dose that members of the public in Amargosa Valley would receive from ambient levels of naturally occurring radon-222 and its decay products.

The maximally exposed individual would have an increase in the probability of incurring a latent cancer fatality ranging from about 0.000016 to 0.000031 (from 16 to 31 chances in 1,000,000) from exposure to radionuclides released from repository facilities over a 70-year lifetime. The total estimated number of latent cancer fatalities in the potentially exposed population would range from 0.46 for the higher-temperature operating mode to 0.97 to 2.0 for the lower-temperature repository operating mode.

For the sake of comparison, statistics published by the Centers for Disease Control indicate that, during 1998, 24 percent of all deaths in the State of Nevada were attributable to cancer of some type and cause. Assuming this mortality rate would remain unchanged for the estimated population in 2035 of about 76,000 within 80 kilometers (50 miles) of the Yucca Mountain site, about 18,000 members of this population would be likely to die from cancer-related causes unrelated to the Proposed Action. During the time the project was active (100 to 324 years), the number of cancer deaths unrelated to the project would range from 30,000 to 89,000 in the general population. Estimated project-related impacts (0.46 to 2.0) would be a very small increase (0.007 percent or less) over this baseline.

Long-Term Radiological Health Impacts. DOE considered potential long-term human health impacts for 10,000 years from the start of emplacement. The analysis estimated potential human health impacts due to processes and events such as corrosion of waste packages, dissolution of waste forms, seismic events, and changing climate. In addition, it considered the effects of such disturbances as exploratory drilling or volcanic events. [UNCERTAINTY IN LONG-TERM PERFORMANCE]

The heat generated by spent nuclear fuel and high-level radioactive waste could affect both the short-term (before repository closure) and the long-term performance of the repository (that is, the ability of the engineered and natural barrier system to isolate the emplaced waste from the accessible environment for long periods). The temperature of the repository after emplacement of spent nuclear fuel and high-level radioactive waste could have a direct effect on the corrosi