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4.2 IMPACT ASSESSMENT METHODOLOGIES

The following is a brief description of the impact assessment approaches used in this EIS for addressing potential impacts of Pantex Plant continued operations at different activity levels and at candidate pit storage sites.

Changes to plant facilities and infrastructure are assessed by comparing the support requirements of the Proposed Action and the Alternatives to site infrastructure capacities. These assessments focus on transportation, infrastructure, and utility systems.

Land use impacts are assessed based on the extent and type of land that would be affected and potential direct impacts resulting from the conversion or from the incompatibility of land use changes with special status and protected lands.

The geologic setting, structural geology, and the soil and sediment quality are discussed. The geologic setting is composed of the geomorphology and the stratigraphy of the region. Structural geology includes regional geology, seismicity, and subsidence. Potential seismic impacts are assessed based on the locations of capable faults and the history of the seismicity in the region. The section on soil and sediment quality includes discussions on soil types and the current environmental restoration processes at Pantex Plant. Impacts to the soil include any activities which would result in erosion and taking soils out of production, which is discussed in the Land Use section. Impacts from the soil would be contaminated soil potentially impacting human health. Soil types at Pantex Plant Site are described and a qualitative analysis is performed to assess the effects of potential contaminants of concern in soils at Pantex Plant Site.

Surface water impacts are assessed based on wastewater discharges from Pantex Plant activities. The assessment of water quality impacts from wastewater (sanitary and process) and stormwater runoff qualitatively address potential impacts to surface water and groundwater resources at Pantex Plant.

Impacts to floodplains are assessed based on whether any Pantex Plant activities, including construction of new facilities, would be located within floodplains.

Groundwater resource impacts are assessed based on the effects on aquifers, groundwater usage, and groundwater quality within the Pantex Plant ROI. Total groundwater use at Pantex Plant and projections of future usage determine the short- and long-term impacts associated with changing activity levels at Pantex Plant. Impacts of groundwater withdrawals on existing contaminant plumes because of construction and facility operation are also assessed.

The assessment of potential impacts to air quality is based on the comparison of impacts from the Proposed Action and Alternatives with applicable State, local, or National Ambient Air Quality Standards (NAAQS)National Ambient Air Quality Standards or the potential exceedance of Prevention of Significant Deterioration (PSD)Prevention of Significant Deterioration increments. The more stringent standards serve as the comparison criteria. The comparison of project toxic pollutants includes guidelines or standards adopted by the State of Texas. Air quality modeling was performed in order to assess the conservative maximum concentrations of individual pollutants that the workers or members of the public might experience. Air quality monitoring data collected by the Texas Natural Resources Conservation Commission (Texas Natural Resource Conservation Commission (TNRCC)TNRCC) has been used to help benchmark the model. However, the data does not correlate to the modeling on a one-to-one basis, as the placement and operation of air quality monitoring stations do not allow for a comprehensive assessment of the impacts of air emissions to the workers and the public.

Acoustic impacts are assessed qualitatively on the basis of the potential degree of change in noise levels at sensitive receptors with respect to ambient conditions. Blast noise from high explosive(s) (HE)high explosives detonation is calculated using an airblast prediction model called BLASTOBLASTO.

Potential impacts are assessed based on the degree to which various habitats or species could be affected by Pantex Plant operations. Where possible, impacts are evaluated with respect to Federal and State protection regulations and standards.

Impacts to wildlife are evaluated in terms of disturbance, displacement, or loss of wildlife. Results of biouptake of radionuclides are identified from monitoring data. Impacts are assessed based on the proximity of wetlands to Pantex Plant operations. Impacts resulting from wastewater discharge into a wetland are evaluated, recognizing the effluents would be required to meet Federal and State standards. A list of species potentially present at Pantex Plant Site was obtained from the U.S. Fish and Wildlife Service (FWS)U.S. Fish and Wildlife Service and appropriate State agencies, and was used in the process of assessing whether Pantex Plant operations would impact any plant or animal under section 7 of the Endangered Species Act.

Impacts on prehistoric resourceprehistoric and historic resourcehistoric resources are assessed by considering whether continued operations at Pantex Plant could substantially add to existing disturbance of resources in the area, adversely affect National Register of Historic Places (NRHP)National Register of Historic Places-eligible resources, or cause loss of, or destruction to, important prehistoric resources. Impacts on Native American resourceNative American resources are assessed by considering whether Pantex Plant activities have the potential to affect sites that are historically important or have a position in a Native American system of belief. Impact assessments for paleontological resources are based on the numbers and kinds of resources that could be affected, as well as the quality of fossil preservation in a given deposit.

The assessment of impacts on local and regional socioeconomic conditions and factors includes changes in population, employment, and income in the Region of Influence (ROI)ROI. The changes to these factors are projected on an annual basis because an exact schedule for changes in the activity levels are not currently known. The assessment includes bounding cases for activity levels.

The focus of this analysis is on the intrasite transfer and handling of hazardous materials, particularly the radiological effects from the transportation and handling of radioactive materials. Accidents involving the transportation and handling of hazardous materials have the potential of leading to human fatalities, excess cancer fatalities, and serious environmental contamination. Radiological exposures and excess cancer fatalities are calculated for workers handling the material. Impacts to the public outside the Pantex Plant boundaries are not expected from intrasite transfer and handling of radioactive materials.

The analysis addresses the waste types and waste volumes generated from Pantex Plant operations, including environmental restoration activities. Impacts are assessed in the context of site practices for treatment, storage, and disposal; associated capacities for the different waste types; and the applicable regulatory requirements.

Pantex Plant does not have existing onsite low-level waste disposal; the number of shipments required to transport low-level waste (LLW)low-level waste from Pantex Plant to the Nevada Test Site (NTS)Nevada Test Site is thus part of the analysis. The risk associated with additional shipments is addressed in the Human Health section.

The health effects are determined for Pantex Plant operations by identifying the types and quantities of material to which one is exposed, estimating exposures, and calculating the resultant health effects. The impacts on human health for workers and the public during normal operation and postulated accidents from various alternatives are assessed. Computer codes such as Melcor Accident Consequence Code System (Melcor Accident Consequence Code System (MACCS)MACCS) and Explosive Release Atmospheric Dispersion (ERAD) are used to simulate impacts. Atmospheric dispersion modeling using Industrial Source Complex Short-Term ISCST2Model, Version 2 (ISCST2) was performed for the air quality analysis and the results are used in the evaluation of impacts to workers from hazardous chemicals. Data from continuous air monitoring stations are used to assess impacts from radiological emissions.

Public health impacts could result from exposure to radioactive or hazardous chemical materials released during operation. Experience from past and current operations that are similar to future operations is used to estimate the radiological health impacts to workers. Modeling is used to estimate the type and amount of material released and the associated radiological and chemical doses. These doses are converted to health effects using appropriate health risk estimators.

The relative consequences of postulated accidents in the evaluation of each alternative are assessed. The accident analysis involves less detail than a formal Probabilistic Risk Assessment by addressing bounding accidents (relatively low probability/high consequence) and a representative spectrum of possible operational accidents (relatively high probability of occurrence and low consequence). The technical approach for the selection of accidents is consistent with the DOE Office of NEPA Oversight Recommendations for the Preparation of Environmental Assessments and Environmental Impact Statement guidance, which recommends consideration of two major categories of accidents: within design basis accidents and beyond design basis accidents (DOE 1993).

One of the scenarios in the accident risk impact assessment is the potential for an aircraft-induced hazardous material dispersal accident. The likelihood and consequences of this accident scenario have been studied extensively since the start of nuclear explosive operations at Pantex Plant, and studies continue to this day. For purposes of this analysis, new data from a Radar Airspace Monitoring System has been used to determine the amount, type, and frequency of aircraft movements in proximity to Pantex Plant. A Draft DOE standard methodology (see appendix E) is used to estimate the likelihood of an aircraft impacting a critical facility at Pantex Plant. Human health risks from aircraft-induced radiological releases are assessed using the MACCS and ERAD computer codes. The resulting doses are converted to a predicted number of excess cancer fatalities.

The intersite transportation assessment was based on the transport mode, weight of material, curies, proximity dose rates (transport index), type of package, number of shipments, and distance. Health impacts are presented for transportation of pits and other nuclear weapon components. Impacts were evaluated for both incident-free transportation and accident conditions using the Analysis of Dispersal Risk Occurring in Transportation (ADROIT) code developed by Sandia National Laboratories.

The potential for disproportionately high and adverse human health or environmental effects on minority and low income populations are evaluated in accordance with Executive Order 12898, Federal Action to Address Environmental Justice in Minority Populations and Low Income Populations. The environmental justice analysis addresses selected demographic characteristics of the Pantex Plant ROI, defined as an 80-kilometer (50-mile) circle centered on Pantex Plant. Similar analyses have also been performed within the ROI for each of the alternate sites considered for interim storage of pits.

The analysis of environmental justice presented in this EIS is based on the definitions of minority and low income populations as contained in the notice for the EPA Office of Environmental Justice (59 FR 192). These definitions call for identification of Census Tracts where 25 percent or more of the persons in 1990 were either minority group members or below poverty level based on their income in 1989. For comparison purposes, definitions of minority and low income populations as provided by the Council on Environmental Quality (CEQ) in August 1995, and also reported in Guidance for Incorporating Environmental Justice Concerns in EPAs NEPA Compliance Analysis (EPA 1996a), are also applied to the 1990 Census data and results of both analysis are reported in the EIS.

Cumulative impacts include the incremental impacts of the actions (usually the proposed or preferred action) when added to other past, present, and reasonably foreseeable future actions. Although several DOE programs described in section 1.7 of this EIS have the potential to impact the Pantex Plant Region of Influence (ROI), sufficient information for incorporation in this document is currently available for only three programs: the Waste Management (WM), the Stockpile Stewardship and Management (SSM), and the Storage and Disposition of Weapons-Usable Fissile Materials (S&D) programs. Programmatic EISs (PEISs) are being prepared by DOE for each of these programs.

The cumulative impacts associated with the three DOE programs were, in some instances, overestimated in the Draft Pantex Plant EIS. This overestimation was due to conservative assumptions concerning the scope and time period associated with each program. After the Draft PEIS for each program was issued and further coordination among the programs clarified the details of certain alternatives, some assumptions concerning the assessment of the cumulative impacts were modified.

In the Draft Pantex Plant EIS, the cumulative impacts associated with both the waste management program and the storage and disposition program were calculated by adding the impacts from the Pantex Plant EIS Proposed Action (at a 2,000 weapons per year level) to those for the different alternatives discussed in each of the PEISs. However, the cumulative impacts associated with any new mission or facility at Pantex Plant should be placed in the context of the overall impacts at the Pantex Plant Site at the time those new facilities or missions would be implemented.

The Pantex Plant EIS and the SSM PEIS both discuss the operations of the entire Pantex Plant, but over different time frames. The level of operations, and associated impacts, discussed in the Pantex Plant EIS is for an approximately 10-year time frame beginning in the year 1997. The SSM PEIS discusses a lower level of the same kind of operations for the time frame of approximately the year 2005 and later, so that the operational levels discussed in the Pantex Plant EIS Proposed Action will evolve over the next 10 years into the level of operations discussed in the No Action Alternative of the SSM PEIS.

In recognition of this evolutionary process, the Final Pantex Plant EIS has been modified so that the cumulative impacts from potential WM PEIS missions and facilities, which would be implemented during the next five to seven years, are combined with the impacts from the level of operations discussed in the Pantex Plant EIS Proposed Action. However, the cumulative impacts from the potential missions and facilities discussed in the bounding storage and disposition alternatives of the S&D PEIS, which would be implemented during the next seven to 20 years, are combined with the impacts from the level of operations discussed in the SSM PEIS No Action Alternative.

There is one exception to this methodology for presenting cumulative impacts. As discussed in sections 1.4 and 1.7.3 of this volume, the Final S&D PEIS will include an alternative under which pits from the Rocky Flats Environmental Technology Site (RFETS) could be transferred to Pantex for storage in Zone 4 as early as 1997. This alternative would result in impacts occurring at the Pantex Plant sooner than they would occur under the bounding storage and disposition alternative of the S&D PEIS (1997 vs. 2004); however, these impacts would be less than those for the bounding case because substantially less total fissile material would be transferred to Pantex.

Storage of pits from RFETS would have incremental impacts in addition to the storage of pits from disassembled weapons. However, this increase is generally accounted for within the level of activities assumed for the Proposed Action in this EIS. That is, the pits from RFETS would not cause the total number of pits stored in Zone 4 to exceed the storage limit of 20,000 pits analyzed under the Proposed Action. Likewise, the intrasite transport of the RFETS pits would cause cumulative impacts, but these impacts are also accounted for within the transportation necessary to move 20,000 pits into storage. The receipt of RFETS pits would require an additional repackaging operation (from FL containers into AL-R8 containers) prior to intrasite transport into storage, as compared to the handling of pits from disassembled weapons, and this operation would contribute cumulative impacts that would not be accounted for by the Proposed Action, but that are addressed in the cumulative impacts analysis.

Another factor that resulted in the overestimation of some cumulative impacts in the Draft Pantex Plant EIS was the double counting of operations that were assessed in all of the EISs. In the Draft Pantex Plant EIS the cumulative impacts associated with the Waste Management program and the Storage and Disposition program were calculated by adding the impacts from the Pantex Plant EIS Proposed Action (at a 2,000 weapons per year level) to those for the different alternatives discussed in each of the PEISs. Since the impacts detailed in both of these documents included all operations at the site (most of which will not change), this addition of impacts resulted in the impacts from many operations being counted twice.

An example of this double counting is the air emissions associated with the steam plant. When the air quality impacts in the Draft Pantex Plant EIS, which included the emissions from the steam plant, were added to those in the S&D PEIS, which also included the steam plant emissions, these emissions were counted twice. While this double counting of many impacts certainly bounded the cumulative impacts to be expected from these programs, it did not provide the best estimate of the cumulative impacts. In the Final Pantex Plant EIS, the cumulative impacts have been recalculated to more accurately reflect the impacts that could be expected if the decisions discussed in the documents were implemented.

In addition to the DOE programs, information on other Federal, State or local projects, including private developments, was sought through contacts with Federal and State regulatory agencies, the Amarillo Economic Development Corporation, the Panhandle Municipal Water Authority, and the City of Amarillo.

This effort yielded only one project (future closure of the Helium Plant) that would contribute to the cumulative impacts in the Pantex Plant ROI. The U.S. Bureau of Mines has been operating the Helium Plant in the Amarillo area since the early 1940s. On October 9, 1996, the President signed the Helium Privatization Act of 1996, directing helium operations to discontinue production and sale of refined helium no later than 18 months from the date of enactment (by April 1998). The impacts of this action are analyzed in section 4.11.5, because cumulative impacts of closing or downsizing this facility would be limited to socioeconomic impacts.

These workloads were used to determine a reasonably foreseeable impact of operating Pantex Plant. Because the dismantlement of a specific weapon system was not analyzed, a bounding impact per category of operation, i.e., dismantlement, assembly, surveillance (not by weapon type, nor by individual operations) was derived from historical data. Then the total impact was derived by scaling these data by number of weapons or, in some cases, by number of people. This is not a limitation to the number of personnel that can be hired. However, it does mean that the level and type of impacts to individual resource areas must remain within the envelopes as stated in the EIS.

This EIS is focused on determining impacts from full-scale dismantlement or disassembly and assembly of an entire weapon. This imparted a conservative, yet "reasonably foreseeable," estimation as to what the impacts would be from operating Pantex Plant. The use of activity levels for operations on 2,000, 1,000, and 500 weapons was a tool to generate estimates for total emission levels, waste generation, risk, etc. The analysis should therefore envelope the impacts from operating the plant without unnecessarily constraining specific process decisions (see section 2.2).

To restate this conclusion, once impact levels are determined, there may exist several permutations on the number of weapons and impact per weapon that fall within the derived impact levels. Specifically, this EIS does not state what processes are accomplished, or a given ratio of particular processes. If some process is needed whereby work on over 2,000 weapons is necessary, but the impacts remain within the impact envelopes, no supplemental EIS would be required. Ongoing assessments would continue to be necessary to ensure that the level of impacts to the environment have not drastically changed. The total number of weapons operations would be evaluated, because it is a key indicator as to whether or not additional NEPA documentation would be required. However, exceeding these numbers does not, by itself, mandate additional Environmental Assessments or EISs. Understanding whether or not there are additional impacts from specific processes is required, but a simple checklist or screening analysis is typically the only documentation necessary to confirm that no additional impacts would result from a process or set of processes. On the other hand, if the analysis confirmed that impact parameters were surpassed, additional NEPA documentation would be required.