4.7 Air Quality
4.7.1 Affected Environment
The following sections describe the affected environment at Pantex Plant and surrounding region for meteorology and climate, atmospheric dispersion, air quality, and atmospheric radiological environment.
4.7.1.1 Meteorology and Climate
Pantex Plant is located in the Texas Panhandle, approximately 27 kilometers (17 miles) northeast of Amarillo, at an elevation of approximately 1,085 meters (3,560 feet).
Regional ClimateThe climate at Pantex Plant and the surrounding region is characteristically that of middle latitude steppe. It is typified by large variations in temperature and precipitation from year to year, with summers that are hot and dry and winters that are mild. A high percentage of sunshine and a rather low humidity prevail over the region. The region is subject to rapid and large temperature changes, especially during the winter when cold fronts from the northern Rocky Mountains and Plains move across the region at speeds up to 64 kilometers (40 miles) per hour. In the spring, moving low-pressure systems produce high winds, with March and April having the strongest. Severe local storms are infrequent, though a few thunderstorms, with damaging hail, lightning, and wind in very localized areas occur most years, usually in spring and summer. These storms are often accompanied by very heavy rain, which produces local flooding.
Local ClimateThe nearest representative station with long-term climatological data (30 years) is 16.1 kilometers (10 miles) west of Pantex Plant at the Amarillo International Airport. Meteorological data have been recorded at the airport over a period of more than 60 years (1931 to present).
The annual average temperature in the area is 13.6 ûC (56.4 ûF); average daily temperatures vary from a minimum of -5.7 ûC (21.8 ûF) in January to maximum of 32.8 ûC (91.1 ûF) in July and August. The average annual precipitation is 49.7 centimeters (19.56 inches). Seventy-five percent of the total annual precipitation falls between April and September. The average annual snowfall is 42.9 centimeters (16.9 inches). The snow usually melts in a few days (Pantex 1996:6.2).
Pantex Plant is located in an area with a relatively high frequency of tornados. Fifty-three tornados were recorded in Carson County between 1950 and 1994 (Pantex 1996:6.3). The estimated probability of a tornado striking a point at Pantex Plant is 2.3 x 10-4 per year (DOE 1995q).
Average wind speeds at Amarillo are relatively high. For the period 1944 through 1993, the average speed was 22 kilometers (14 miles) per hour. Calms occur about 1 percent of the time. The wind blows predominantly from the south from May to September and from the southwest the remainder of the year (Pantex 1996:6.2). Figure 4.7.1.11 is a wind rose for the Amarillo International Airport (EPA 1995a).
Figure 4.7.1.1-1.--Distribution of Wind Speed and Direction at the Amarillo International Airport.
4.7.1.2 Atmospheric Dispersion
Once pollutants are emitted into the atmosphere, the prevailing weather conditions determine their dispersion. Atmospheric stability controls the dispersion of pollutants in the vicinity of a source. This factor is especially important to the assessment of primary pollutant impacts. Stability is affected by thermal and mechanical turbulence of the atmosphere and wind velocity of the layer of air closest to the ground. When the atmosphere is unstable, usually during daytime, dispersion of airborne particulates increases. Data collected at the Amarillo National Weather Service station for 1988 indicated that unstable conditions occurred approximately 16 percent of the time, neutral conditions approximately 60 percent, and stable conditions approximately 24 percent, on an annual basis (DOE 1995q:B17). Thus, relatively good vertical dispersion occurs about 76 percent of the time in the vicinity of Pantex Plant.
Another meteorological element that influences dispersion is the mixing height. The mixing height is the height above the ground through which relatively vigorous vertical mixing occurs. The mixed layer dilutes pollutants released in it. Annual average mixing heights over the Amarillo area range from about 328 meters (1,076 feet) in the morning to about 1,973 meters (6,473 feet) in the afternoon (Pantex 1996:6.4). Therefore, based on stability and mixing height considerations, atmospheric dispersion at Pantex Plant and vicinity is, in general, quite good.
4.7.1.3 Ambient Air Quality
Ambient air quality is determined by the emission of pollutants and their interaction with atmospheric conditions. Air quality is described in terms of concentrations of pollutants. If these concentrations in the ambient air are high enough to cause health concerns or effect visibility in visual resource areas then emissions are regulated to bring the concentrations down. Ambient air quality is assessed by the monitoring of pollutant levels in the air and modeling of emissions' interactions with atmospheric conditions. This subsection discusses the regulation and control of air pollutants, the air quality monitoring at Pantex Plant, and the modeling performed to evaluate potential impacts of the Proposed Action and the Alternatives.
Regulation of Air QualityConcentrations. Air quality in a given location is described by the concentration of various pollutants in the atmosphere expressed in units of parts per million or in micrograms per cubic meter. The standards and limits set by regulations on air quality are listed in concentrations averaged over certain time limits (e.g., 30 minutes, 1 hour, 3 hours). The averaging times listed in the tables in this section correspond to the regulatory averaging times for the individual pollutants. Ambient air is defined as that portion of the atmosphere external to the buildings to which the general public has access. Ambient air quality standards specify upper limits of concentrations and durations of pollutants in the ambient air that are consistent with the goal of preventing harmful effects.
The impact of exposure to ambient contaminants is a function of the pollutant involved, the duration of the exposure, and the concentrations reached during the exposure. The significance of pollutant concentrations is determined by comparing the concentrations with appropriate Federal or State ambient air quality standards. These standards represent the allowable pollutant concentrations at which public health and welfare are protected and include a reasonable margin of safety.
Another determining factor in the significance of pollutant concentrations is whether the area is in attainment or nonattainment for that pollutant. An area is designated by the U.S. Environmental Protection Agency (EPA) as being in attainment for a pollutant if ambient concentrations of that pollutant are below the National Ambient Air Quality Standards (NAAQS) and nonattainment if exceedances of NAAQS occur. Areas where insufficient data are available to make an attainment status designation are listed as unclassified. Unclassified areas are treated as attainment areas for regulatory purposes.
The NAAQS were established by EPA. The State of Texas implements and enforces the NAAQS, plus TNRCC has placed regulations on additional pollutants. NAAQS have been established for ozone (O3), carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO2), particulate matter (fine dust) of aerodynamic diameter less than 10 micrometers (PM10), and lead (Pb). These NAAQS pollutants are sometimes referred as "criteria" pollutants. TNRCC has also set net ground level limitations for total suspended particulate matter, inorganic fluoride compounds calculated as hydrogen fluoride (HF), hydrogen sulfide, sulfuric acid, and beryllium. NAAQS and the Texas Air Quality Standards are presented in Table 4.7.1.31 (TNRCC 1993a).
The EPA has granted to TNRCC the authority to implement regulations to prevent the significant deterioration of air quality in areas that are designated as attainment or unclassifiable. The Prevention of Significant Deterioration (PSD) program is implemented in large part through the use of "increments" and area classifications that effectively define what "significant deterioration" is for individual pollutants. The Clean Air Act's area classification scheme for PSD establishes three classes of geographic areas (Class 1, 2, and 3) and applies increments of different stringency to each class. Air quality impacts, in combination with other PSD sources in the area, must not exceed the maximum allowable increments presented in Table 4.7.1.32 (TNRCC 1993a).
Visibility. Class 1 areas are those of special National concern where any appreciable deterioration in air quality is considered significant. Consequently, the most restrictive increments apply in Class 1 areas. Class 1 areas include all international and National parks, wilderness areas, and memorial parks that exceed certain sizes.
The Clean Air Act (CAA) (42 U.S.C. 7401) requires a visibility analysis for any new or modified major stationary sources, in an attainment or nonattainment area, whose emissions would affect the visibility in a Class 1 area. The nearest PSD Class 1 areas to Pantex Plant are the Salt Creek Wilderness, in New Mexico, approximately 274 kilometers (170 miles) to the southwest, and the Wichita Mountains Wilderness, in Oklahoma, approximately 290 kilometers (180 miles) to the east-southeast (40 CFR 81.421 and 81.424). Since these Class 1 areas are approximately 274 kilometers (170 miles) from Pantex Plant, pollutant emissions from Pantex Plant facilities would not have an adverse impact on the air quality in these areas and no additional analyses would be required. No public recreational areas are located within 16 kilometers (10 miles) of Pantex Plant.
Less restrictive increments apply in areas designated as Class 2 or Class 3. Class 2 areas are all PSD areas that are designated as attainment or unclassifiable with respect to the NAAQS and are not classified in CAA as Class 1 areas. Individual states have the authority to redesignate Class 2 areas to Class 3 areas to allow for higher levels of industrial development and emissions growth. There are as yet no designated Class 3 areas.
PSD requirements apply to major stationary sources. CAA specifies 26 categories of stationary sources which are considered major sources if they emit or have potential to emit 90.7 metric tons (100 tons) per year or more of any pollutant subject to CAA regulation (40 CFR Section 52.21). Any other stationary source which emits or has the potential to emit 226.8 metric tons (250 tons) per year or more of any air pollutant subject to regulation under CAA is considered a major source and is subject to PSD requirements.
Pantex Plant stationary sources do not fall within the 26 categories of stationary sources. Also, plant stationary sources emit less than 226.8 metric tons (250 tons) per year of any regulated pollutant (see Tables 4.7.1.33 and 4.7.1.36). Pollutant emissions from future Pantex Plant operations would also be less than 226.8 metric tons (250 tons) per year (see Tables 4.7.2.13 and 4.7.2.14). Therefore, Pantex Plant would not be subject to PSD requirements.
Table 4.7.1.3-1.--National Ambient Air Quality Standards and Texas Limitations (.pdf)
Assessment of Air QualityAssessment Parameters. Existing ambient air quality in the region is defined by air quality data and emissions information. Air quality data were obtained from air quality monitoring stations maintained by TNRCC (TNRCC 1993c; TNRCC 1994a). Information on pollutant concentrations measured for short-term (24 hours or less) and long-term (annual) averaging periods were extracted from the monitoring station data to characterize the existing air quality background of the area. The emission inventory for the region was obtained from EPA and Pantex Plant. Inventory data are separated by pollutant and reported in pounds and tons per year to describe the baseline conditions of pollutant emissions in the area (EPA 1988). Since the TNRCC air quality monitoring stations do not operate continuously and are not placed at the borders of Pantex Plant, the monitoring data do not indicate the impacts to the public from plant air emissions.
Identifying the Region of Influence (ROI) for an air quality assessment requires knowledge of the pollutant types, source emission rates and release parameters, the proximity relationship of project emission sources to other emission sources, and local and regional meteorological conditions. For inert pollutants (all pollutants other than SO2, O3, and its precursors NO2 and volatile organic compounds [VOCs]) the ROI is generally an area extending a few miles downwind from the source. The ROI for O3 may extend much farther downwind than the ROI for inert pollutants. For the purpose of this air quality analysis, the ROI is defined as Carson County and its eight surrounding counties: Potter, Randall, Armstrong, Donley, Gray, Roberts, Hutchinson, and Moore.
The windrose in Figure 4.7.1.11 indicates that pollutants from Pantex Plant might be transported into any of these surrounding counties. As mentioned previously, the ROI for O3 extends farther downwind than the ROI for inert pollutants. This greater distance occurs because in the presence of solar radiation, the maximum effect of precursor emissions on O3 levels usually occurs several hours after they are emitted and therefore, many miles from the source.
The ROI and Pantex Plant are located in the Amarillo-Lubbock Intrastate Air Quality Control Region (AQCR) 211. AQCR 211 is designated by EPA as "better than national standards" for SO2, "unclassifiable/attainment" for CO and O3, "cannot be classified or better than National standards" for NO2, "unclassifiable" for PM10, and "not designated" for lead (40 CFR 81.344).
Air Monitoring Results. TNRCC operates six air quality monitoring stations in the ROI, one at Amarillo and five at Pantex Plant. The Amarillo station only monitors PM10. The monitoring report issued by the TNRCC for the year 1992 indicated that concentrations of this pollutant in Amarillo were within the NAAQS (Pantex 1996:6.5).
TNRCC, through a grant from DOE, established five air quality monitoring stations at Pantex Plant in September 1992. Locations of these stations are shown in Figure 4.7.1.31. In August 1995, one of these monitoring stations (Site No. 3) was repositioned to a new location (Site No. 6). The first annual report on this program covered the period January 1 to December 31, 1993 (TNRCC 1994a). Twenty-four hour sampling is conducted once every six days. The TNRCC measures inorganic pollutants as PM10 and HF. Organic pollutants are measured as VOCs in parts per billion by volume (ppbv). A few samples have been analyzed for metals, but this is not done on a regular basis. At two sites, wind speed, wind direction, temperature, and relative humidity are measured.
A Fourier Transform Infrared (FTIR) continuous monitor has also been installed at the Masterson Pump station located two miles north of Pantex Plant. The data collected with this sampler is considered developmental data since the TNRCC is still developing procedures (including quality assurance procedures) for this method. Initial screening of the data, however, does not indicate levels that might be harmful to public health and/or welfare. The first annual report on this program covered the period from January 1, 1993 to December 31, 1993 (Pantex 1996).
During 1993, only one 24-hour PM10 measurement exceeded the NAAQS while, in 1994, the standard was exceeded on one day in January and one day in June. From July 6, 1993, through December 31, 1994, TNRCC air sampling coincided with Pantex Plant burn days on 57 occasions. Of those 57 days, all had valid PM10 samples at one or more sites; however, the exceedance of the standard on the January day was a non-burn day and TNRCC stated that windblown dust particles are strongly suggested as a major contributor to that exceedance (TNRCC 1995c; Pantex 1996:6.5).
Two compounds, methylene chloride and 1,2-dibromoethane, exceeded the TNRCC Effects Screening Levels (ESLs) once each during 1993. Methylene chloride was measured at 213.7 ppbv on July 6, 1993 (TNRCC 1993c). The concentration was approximately seven times the ESL (30 ppbv) established by TNRCC. In 1994, the maximum concentration of methylene chloride was measured at 11.75 ppbv, which is lower than the ESL (TNRCC 1995c).
The TNRCC ESLs are "tools" the Toxicology and Risk Assessment Staff of TNRCC use to evaluate the impacts of air pollutant emissions. They are not ambient air standards. If predicted or measured airborne levels of a certain chemical do not exceed its screening level, it would not be expected to have any adverse health or welfare effects. If ambient levels of air contaminants exceed the screening levels, it does not necessarily indicate a problem. It is just a trigger for a more in-depth review. Therefore, TNRCC sets the ESL at levels where TNRCC would not expect adverse effects. These levels are sometimes below the limit of detection for a pollutant.
Figure 4.7.1.3-1.--Air Quality Monitoring Stations at and Residences near Pantex Plant Site.
In 1995, 1,2-dibromoethane was detected at 0.23 ppbv (TNRCC 1993b), which exceeded the ESL (0.2 ppbv). In 1994, the concentration of 1,2-dibromoethane (0.72 and 0.51 ppbv) exceeded the ESL on two occasions (TNRCC 1995c). In 1995, the concentration (0.29 ppbv) of 1,2-dibromoethane exceeded the ESL once (TNRCC 1996d).
The TNRCC concluded that in the 1993 and 1995 case of the 1,2-dibromoethane, it was not certain the compound was actually present at the reported concentration. In the case of the 1993 methylene chloride exceedance, the TNRCC Toxicology and Risk Assessment Section staff stated that the one exceedance was not expected to result in any long-term health effects. Monitoring in the last quarter of 1995 indicated that all organic compounds were measured below their respective ESLs, concentrations of HF were measured below the TNRCC Regulation III Standard, and measured concentrations of PM10 were below the NAAQS. The October-December 1995 TNRCC Ambient Air Monitoring Report for Pantex Plant is the last quarterly report the TNRCC will produce; however, quarterly data summaries will be accessible via the Internet, at the following address:
http://www.tnrcc.state.tx.us/air/monops
Annual reports will continue to be published (Pantex 1996).
Air Quality ModelingSince the onsite air quality monitoring network cannot be used to evaluate the effect of Pantex Plant pollutant emissions on offsite ambient concentrations, air dispersion models were applied to assess the maximum pollutant concentrations that could occur on or near the Pantex Plant boundary. Modeling was performed with EPA preferred Industrial Source Complex Models (ISCST2 and ISCLT2). Hourly surface and upper air data from the Amarillo International Airport were used in the ISCST2 model. The meteorological data were for the year 1988. This year's data is the only data with mixing heights approved by TNRCC. For the ISCLT2 model, the joint frequency distribution of wind speed, wind direction, and stability contained in the stability array program output, based on 1985 through 1989 Amarillo International Airport data, were used.
Discrete receptors with a spacing of 100 meters were established along the northern, eastern, and western boundaries of the site. The southern line of receptors were located on an east-west line south of the Pantex Plant boundary, but generally north of the site boundary along U.S. Highway 60 (see Figure 4.7.1.31).
The emission rates used in the Industrial Source Complex models were provided by Pantex Plant personnel (PC 1994b). These emission rates are consistent with the submittal to TNRCC. Emissions from the Burning Ground, where high explosive(s) (HE) are burned, were confined to particular hours of the day. For all explosives that emitted HF, the burning hours were limited to the period 11:00 a.m. to 6:00 p.m., while all other explosives could be burned during the period 7:00 a.m. to 6:00 p.m.
Two scenarios were assumed for the Burning Ground. One scenario assumed that 363 kilograms (800 pounds) of explosives were burned while the second scenario assumed a 45.4-kilogram (100-pound) burn. The 360 kilograms (800 pounds) of HE was assumed to consist of a mixture of 90.7 kilograms (200 pounds) of LX17 and 272.1 kilograms (600 pounds) of PBX9404, while the 45.5 kilograms (100 pounds) of HE consisted of 11.4 kilograms (25 pounds) of LX17 and 34.1 kilograms (75 pounds) of PBX9404. The different kinds of HE are mixed to maximize the heat produced by the burning and keep the amount of HF emitted below the regulatory limits. In order to be conservative, the HE mixes modeled in this EIS were chosen for the lowest heat output and highest emission of HF allowed by regulation.
Modeling Results. Four criteria air pollutants, 36 air pollutants that are listed in CAA, and 50 air pollutants that are listed by the TNRCC have been identified that are emitted from existing Pantex Plant operations (Pantex 1996:6.6). All 90 air pollutants were modeled. The Pantex Plant chemical air emissions inventory is summarized in Table 4.7.1.33. The maximum estimated fence line concentrations of these pollutants are presented in Tables 4.7.1.34 and 4.7.1.35. Table 4.7.1.34 presents the results for the criteria pollutants CO, NO2, PM10, and Pb. The NAAQS for each pollutant is also presented in Table 4.7.1.34. As shown in the table, none of the pollutant concentrations exceeded standards at the Pantex Plant boundary.
The results for the rest of the chemical air pollutants emitted by Pantex Plant are presented as two groups. The first group includes those chemical air pollutants emitted by Pantex Plant that are listed in CAA, as amended, plus those pollutants with estimated concentrations above the appropriate ESL. Only alcohols, modeled as a group, were estimated to exceed an ESL. The second group includes those chemical air pollutants emitted by Pantex Plant that are listed in State of Texas regulations (except for alcohols as mentioned above). Both groups were originally modeled for the current status of the plant (i.e., Affected Environment) and the potential future impacts related to the alternatives.
The maximum estimated fence line concentrations for both groups are presented in Table 4.7.1.35 in comparison with the appropriate TNRCC ESLs. The first group, including alcohols, was also modeled for the maximum estimated concentrations at eleven of the residences near the boundaries of the Pantex Plant Site. These results are presented in Table B.4.11 in appendix B. All of the air pollutants except alcohols were estimated to be below their respective ESLs at the Pantex Plant boundary.
The group of alcohols consisted of those alcohols used by Pantex Plant for which there were no individual emission rates. TNRCC does not have an ESL for the family of alcohols, but rather chose in their modeling of Pantex Plant to use a conservative ESL equal to 100 mg/m3 as the ESL for the group of alcohols. The group of alcohols exceeded the conservative 1-hour ESL at and near the Pantex Plant boundary. The maximum estimated fence line concentration for alcohols (195 mg/m3) was almost twice the conservative ESL. As explained earlier, the exceedance of an ESL does not necessarily indicate a problem. It is just a trigger for a more in-depth review.
A subsequent review of the inventory of the amounts of the individual alcohols present at the Plant showed that the ESL used in the modeling was excessively conservative (PC 1996b). Since the emission rates for the individual alcohols in the group were not speciated in the original emissions inventory, a second inventory was obtained to determine quantities of individual alcohols maintained on-hand at the plant. An estimation of the maximum fence line concentration for each of the alcohols was then calculated based on the ratio of the amount of each alcohol to the total inventory of the group of alcohols present at Pantex Plant (see Table B.4.12 in appendix B). None of the individual alcohols were found to exceed their respective ESLs at or near the plant boundary.
Table 4.7.1.3-3.--Estimated Pantex Plant Chemical Air Emissions Inventory (.pdf)
HF is a pollutant regulated by TNRCC. The modeling results predicted a maximum 3-hour average concentration of 1.52 mg/m3. This concentration is below the standard of 4.90 micrograms per cubic meter. This concentration resulted from a 45.4-kilogram (100-pound) burn of HE. For a 363-kilogram (800-pound) burn of HE, the 3-hour average maximum concentration was also below the standard (see Table 4.7.1.35).
The maximum pollutant concentrations which were predicted to occur at 11 residences that are located near the plant boundaries are all below respective NAAQS. Appendix B presents tables of these concentrations for each of the 11 residences.
In summary, the modeling results presented in this document are the highest concentrations predicted by the model. The modeling results suggest that existing short-term air quality may be slightly degraded on or near the boundary of Pantex Plant by alcohol emissions. However, subsequent review of specific alcohol concentrations indicates that this degradation would not occur and that the regional and long-term air quality is good.
Emissions. The amount of pollutants entering the atmosphere (from all sources) in a given time period is used by EPA to determine the overall emissions in an area. This definition facilitates the identification of the sources that can be defined as the major sources whose control can lead to a considerable reduction in the pollutant levels for the area. There are various other sources that contribute to overall pollutant emissions, including mobile sources, point (stationary) sources, and area emissions.
Mobile sources include conventional motor vehicles (including Safe Secure Tractor Trailers) and others such as boats, trains, planes, and off-road motor vehicles. Point sources include most industrial and energy-producing facilities that have stacks, vents, or flues from which emissions discharge. Area sources are groups of similar emission sources that do not individually contribute significant amounts of air pollutants, but that do contribute collectively.
CAA, as amended in August 1977 and November 1990, dictates that project emission sources must comply with ambient air quality standards and regulations that have been established by Federal, State, and county regulatory agencies. These standards and regulations focus on the maximum allowable ambient pollutant concentrations resulting from project emissions, both separately and combined with other surrounding sources, and the maximum allowable emissions from the project.
The primary emission sources of criteria pollutants at Pantex Plant are steam plant boilers, the explosives burning operation, diesel and gasoline engines and motor vehicles. Potential emission sources of chemical air pollutants include the HE synthesis facility, the explosive burning operation, miscellaneous laboratories, and other small operations. Table 4.7.1.36 presents a summary of the 1993 criteria pollutant emission inventory for stationary and mobile sources at Pantex Plant (Pantex 1996: 6.6.1). The mobile source emissions were developed using emission factors from the EPA mobile sources emission factor model MOBILE 5a and estimates of the traffic volumes on Pantex Plant (EPA 1994; Pantex 1996: 9.5).
The 1990 CAA amendments established a new control standard for air toxics called Maximum Achievable Control Technology (MACT), which will have as its foundation the maximum level of control achieved in practice within industry. TheMACT standard must be achieved by sources with the potential to emit 9.08 metric tons (10 tons) per year of any single hazardous air pollutant (HAP), or more than 22.7 metric tons (25 tons) per year of any combination of HAPs. Since, as shown in Table 4.7.1.33, none of the emissions of the individual HAPs at Pantex Plant exceed 9.1 metric tons (10 tons) per year and the combined emissions of all the HAPs are less than 22.7 metric tons (25 tons) per year, MACT standards are not applicable.
A summary of the criteria pollutant emissions for the nine counties in the ROI is shown in Table 4.7.1.37. These emissions include both stationary and mobile source emissions and were obtained from the EPA National Emissions Data System. Pantex Plant emissions are also shown in the table for comparison with ROI emissions.
Pantex Plant emissions contribute a small portion of pollutants to the overall pollutant burden in the ROI. Because of good atmospheric dispersion and relative low emissions over the region, the existing air quality in the ROI is generally very good.
4.7.1.4 Atmospheric Radiological Environment
The population of the Texas Panhandle is exposed to environmental radiation from both natural and manmade sources. This section summarizes the sources and levels of radiation exposure in this geographical region, including sources of airborne radionuclide emissions from Pantex Plant. Estimates of radioactivity levels and radiological doses from current Pantex Plant operations are provided and discussed (DOE 1995b).
Sources of RadioactivityThe major source of radioactive exposure in the Texas Panhandle is natural background radiation. Sources of radioactivity related to Pantex Plant operations contribute a negligible amount of additional exposure.
Background radiation includes sources such as cosmic rays; radioactivity naturally present in soil, rocks, and the human body; and the airborne radionuclides of natural origin (such as radon). Radioactivity still remaining in the environment as a result of atmospheric testing of nuclear weapons also contributes to the background radioactivity level, although in very small amounts. The natural background dose for residents of the Texas Panhandle is about 95 millirem per year. For comparison, the average annual dose equivalent to any citizen of the U.S. is about 160 millirem, excluding exposure to radon (NCRP 1987).
Potential sources of radioactivity at Pantex Plant from weapons activities include radioactive materials that may be present in the components of weapons and in radiation-generating devices. The radioactive materials in weapons include tritium, various isotopes of plutonium and uranium, and thorium. Gamma radiation is produced by equipment that contains sealed gamma sources (e.g., cobalt-60 and cesium-137), Van de Graaf generators, and linear accelerators.
In normal operating situations, little potential exists for exposure to Pantex Plant personnel, the public, or the environment from release of radioactive materials. Small amounts of tritium escape as a gas or vapor during normal operations, and some tritium residual is present onsite as a result of an accidental release in 1989. Recent amounts of tritium released in 1993 and 1994 were 0.312 curie and 0.446 curie, respectively (DOE 1994b: 4-4; DOE 1995b:7-2). On May 17, 1989, an unplanned release of tritium occurred in Cell 1 in Zone 12 during a routine disassembly operation. The accidental release of tritium in 1989 was conservatively estimated as 40,000 curies (Pantex 1996:16.1).
Existing Radiological ConditionsMonitoring and assessment activities are conducted to characterize existing radiological conditions at Pantex Plant and the surrounding environment (DOE 1995b:8-6 to 8-7). Results of these activities show that exposures resulting from airborne radionuclide emissions are well within applicable standards and are a small fraction of the dose from background sources. These results are discussed separately below for onsite and offsite environments.
Onsite Doses. An indication of onsite radiological conditions is obtained by comparing measured onsite concentrations with those from Pantex Plant nearby locations and a distant location. Results from onsite and nearby locations include contributions from background conditions and Pantex Plant emissions, while the distant location represents background conditions beyond the influence of Pantex Plant emissions. Pantex Plant has 10 offsite, 7 onsite, and 17 perimeter air sampling locations for the air monitoring program for airborne radioactive emissions only. Nine of the 10 offsite units are located within an approximately 8-kilometer (5-mile) radius of the plant. A control site, used to collect background air data is located 48 kilometers (30 miles) west of Pantex Plant at the Bushland Agricultural Research Station (Pantex 1996:16.1).
The data show that 1994 average airborne radioactivity and radiation exposure levels within and around Pantex Plant were only slightly different than those at the control station. The average annual dose (as measured by thermoluminescent dosimeters during 1994) was 97 millirem onsite, 95 at the nearby offsite locations and 93 at the control station (DOE 1995b).
Offsite Doses. The offsite population may receive a very small radiation dose as a result of radiological conditions directly attributable to Pantex Plant operations. The dose associated with baseline radiological emissions is assessed for a maximally exposed individual. The maximally exposed individual is a hypothetical person whose habits and proximity to Pantex Plant are such that the person would receive the highest dose projected to result from site-wide radiological emissions.
The dose calculated for the maximally exposed individual for 1994 was 5.8 x 10-5 millirem per year. The offsite radiation doses from onsite sources were calculated using the CAP88/PC model and 1994 meteorological data in accordance with 40 CFR 61, Subpart H (Pantex 1996). This value was obtained for tritium, the only radionuclide that was released in 1994. The maximally exposed individual dose was well below the National Emissions Standards for HAPs dose limit (10 millirem per year) and the dose received from background sources (95 millirem per year).
The collective dose to the surrounding population as a result of Pantex Plant emissions, assessed using the total population residing within a circular area with an 80-kilometer (50-mile) radius extending from the plant, was 1.37 x 10-4 person-rem in 1994. This population dose was distributed over a population of about 267,000. This population dose is very small when compared with the dose received by the same population from background sources (over 26,000 person-rem).
Results of fence line monitoring for oxidized tritium, elemental tritium, uranium-234, uranium-238, plutonium-239, plutonium-240, and gross alpha and beta were compared to the Derived Concentration Guidelines (DCG) for inhalation listed in DOE Order 5400.5 "Radiation Protection of the Public and the Environment." The measured concentrations of these radionuclides were found to be several orders of magnitude below the DCG levels (DOE 1995b).
Health risks associated with maximum potential exposure levels in the onsite and offsite environments are described in section 4.14, Human Health.
4.7.2 Impacts of Proposed Action
4.7.2.1 Impacts of Continued Operations
Weapons-Related ActivitiesAmbient Concentrations. The estimation of air quality impacts for continued operations was made using the following assumptions:
- Continued operations cover the 10-year period examined.
- Three weapons levels are representative of the range of likely levels:
2,000 weapons per year.
1,000 weapons per year.
500 weapons per year.
The term "weapons level" includes activities related to the assembly and disassembly of nuclear weapons, certain maintenance and monitoring activities regarding the nuclear weapons stockpile, modification of nuclear weapons, production of HE, and the open burning of HE.
Air quality modeling was performed for each level of continued operations using the ISCST2 and ISCLT2 models to estimate ambient concentrations. The modeling methodology was the same as outlined in section 4.7.1.3 (Ambient Air Quality) and more fully described in appendix B.
The emissions inventory used for the 2,000 weapons level was the same as that used for the Affected Environment (section 4.7.1.3 and appendix B), except that the Burning Ground Upgrade emissions were added and the HE explosive mixture that was burned included LX04 and PBX9404 rather than LX17 and PBX9404. Information from Pantex Plant personnel indicated that LX17 would not be burned in the 1997 to 2007 period.
The Burning Ground Upgrade project would replace the current methods of removing HE contamination from equipment and parts. The upgrade would consist of a covered three-sided structure with a fan to exhaust emissions through an elevated stack. The wood currently used as an auxiliary heat source for the burns would be replaced by natural gas. The modeling results are presented in Tables 4.7.2.11 and 4.7.2.12.
Table 4.7.2.11 presents the maximum criteria pollutant concentrations that were obtained at or near the Pantex Plant boundary. The NAAQS for these pollutants are also shown for comparison. Table 4.7.2.12 presents the maximum chemical pollutant concentrations that were obtained at or near the Pantex Plant boundary. The applicable State of Texas ESL is also shown for comparison. Table 4.7.2.12 presents the concentrations calculated for the continued operations at the 2,000, 1,000, and 500 weapons levels for those pollutants that are listed in CAA (plus alcohols) and the 2,000 weapons level for those pollutants that are listed by TNRCC.
The tables show that, except for alcohols, all criteria pollutant and chemical air pollutant concentrations are below their respective ambient air quality standards or their respective ESLs for continued operations at all three levels. For those pollutants listed by TNRCC, the estimated concentrations are low enough for the 2,000 weapons level that the results for the reduced operations levels (i.e. 1,000 and 500 weapons levels) were not calculated.
The maximum concentrations of criteria pollutants and CAA listed air pollutants estimated to occur at the 11 residences located near the Pantex Plant boundary are below their respective ambient air standards or their respective ESLs. Appendix B presents tables of these concentrations for each of the 11 residences.
Alcohols exceeded the ESL at the boundary and at residence 10. These alcohols were modeled as a group and compared with the conservative ESL used by TNRCC. However, subsequent review of the inventories of the types of alcohols and quantities on hand at the plant showed that the use of the conservative ESL for the group of alcohols was excessively conservative. When the total concentrations of the individual alcohols were prorated, none of the individual alcohols exceeded their respective ESLs at or near the fence line. Table B.4.12 in appendix B shows the prorated concentrations of these alcohols.
Since ambient concentrations of all criteria pollutants and HAPs do not violate any of the ambient standards or ESLs beyond the Pantex Plant boundary, the air quality impacts from continued operations under the Proposed Action would be minor and would not be considered significant.
Criteria and VOC Pollutant Emissions
A summary of criteria and VOC pollutant emissions for the 2,000, 1,000 and 500 weapons levels are presented in Tables 4.7.2.13, 4.7.2.14, and 4.7.2.15, respectively. Emissions for the 2,000 weapons level would be about the same as those shown in Table 4.7.1.36 with the addition of emissions projected for the Burning Ground upgrade. In general, emissions for 1,000 and 500 levels are less than those for the 2,000 weapons. However, emission reductions are not directly proportional to weapons level reductions. This result occurs because some facility emissions would not be reduced when weapons levels are reduced (e.g., heating of buildings).
Criteria pollutant emissions resulting from continued operations at Pantex Plant would contribute about 1 percent or less to the overall pollution burden in Carson and Potter Counties (see Table 4.7.1.37 for county emissions). Since this represents such a small impact on the two closest counties, emissions from Pantex Plant would be expected to have a negligible impact on the regional air quality.
Radiological EmissionsThe radiological emissions that were discussed for the Affected Environment (section 4.7.1.4) were assumed for the 2,000 weapons level. The impacts from these emissions would also be the same as those discussed in the Affected Environment above. The impacts from these emissions are several orders of magnitude below the DCGs and National Emissions Standards for Hazardous Air Pollutants (NESHAP) dose limits. Therefore, the impacts would not be significant. The emissions levels associated with the 1,000 and 500 weapons levels would be less than those for the 2,000 weapons level. Therefore, the impacts for these levels are bounded by the impacts for the 2,000 weapons level and are also not significant.
Pit Storage ActivitiesOnly indirect pollutant emissions would result from pit storage activities. Pollutant exhaust emissions from the Safe Secure Tractor Trailers hauling weapons or pits to Pantex Plant and from the vehicles used by personnel responsible for pit storage would be the principal sources. Onsite pit transfers are accomplished with electric forklifts which do not emit any pollutants.
Pollutant emissions from these indirect sources are a small fraction of the total emissions from Pantex Plant. Therefore, air quality impacts resulting from pit storage activities would be negligible.
Environmental Restoration ActivitiesIn May 1994, Pantex Plant was placed on the National Priorities List by EPA. The primary motivations for cleanup of these sites are to protect the general environment and to protect the health and safety of persons in proximity to the site.
Environmental restoration (ER) activities at Pantex Plant are expected to generate 772.6 cubic meters (1,010 cubic yards) of hazardous solid waste between 1997 and 2000 (see section 4.13), most of which will be in the form of contaminated soil. The majority of ER activities are expected to be completed by 2000.
Remedial actions at Pantex Plant could involve handling of contaminated soil. This handling could result in fugitive dust emissions that can carry inorganic particles and organic constituents that are contained in or are adhering to the dust.
Soil handling can also lead to enhancement of volatile organic emissions due to exposure of the contaminated soil to the atmosphere. Specific activities with emission potential include excavation, transport, dumping, storage, and grading.
Pantex Plant procedures for minimizing fugitive dust emissions would keep the impacts to a minimum. Thus, air quality impacts from ER activities would be reduced to a minimum and would, therefore, be negligible.
Waste Management ActivitiesThe principal sources of pollutant emissions related to waste management activities are as follows:
- Burning Ground.
- Drum sampling.
- Bulk transport.
The emissions from these sources were included in the site-wide dispersion modeling. As indicated previously, the results of the site-wide modeling indicated that the continued operation of Pantex Plant would produce only negligible impacts to the regional and local air quality (see section 4.7.2.1).
4.7.2.2 Impacts of New Facility Construction Upgrades
Construction ImpactsDuring the construction phase of the new facility upgrades, exhaust emissions from construction equipment would consist of CO, VOCs, NO2, SO2, and particulate matter. The calculation of emission rates of exhaust pollutants from construction equipment was based on emission factors provided in the EPA document AP42, Compilation of Air Pollutant Emission Factors (EPA 1995b, volume 2, Table II-7.1). For highway vehicles (worker commuting vehicles and delivery vehicles) emission factors were obtained from the EPA Mobile Source Emission Factor Model (MOBILE 5a) (EPA 1994).
Construction equipment composition that was assumed for the peak construction year, 1999, is shown in Table 4.7.2.21. (See section 3.1.1 for description of facility upgrade projects.) Fugitive dust generated during the clearing, grading, and other earth-moving operations is dependent on a number of factors, which include silt and moisture content of the soil, wind speed, and area disturbed. A common procedure to estimate fugitive emissions from an entire construction site is to use the EPA emission factor of 1.2 tons per acre per month of construction activity (EPA 1995b, volume 1, Section 13.2.3.3). This emission factor represents particles less than 30 microns in diameter. A multiplication factor of 0.5 was used to correct the emission rate to one for PM10 (EPA 1995b, volume 1, Page 13.2.2-3). Also, it was assumed that water would be applied to disturbed areas. This would reduce emission rates by about 50 percent (EPA 1985). It was estimated that construction of the facilities would disturb a total of 3.2 hectares (7.9 acres) over the construction period. It was assumed that the disturbance would occur in the first 2 years, 1998 and 1999, of the construction period.
The estimated annual pollutant emissions resulting from construction activities for the years 1998 through 2004 are presented in Table 4.7.2.2-2. Construction emissions during the peak year, 1999, increase the Pantex Plant annual emissions (see Table 4.7.1.3-7) by about 8 to 13 percent. The emission increases for the other construction years (1998, 2000, and 2001) are less. These temporary increases are too small to result in violations of the NAAQS beyond the Pantex Plant boundary. Therefore, air quality impacts resulting from construction of the new facility upgrades would be negligible.
Operations ImpactsEmissions resulting from the operation of the new or upgraded facilities have been mostly accounted for in the site-wide air quality analysis for continued operations under the Proposed Action (section 4.7.2.1). Emissions from the Materials Compatibility and Assurance Facility, the Metrology and Health Physics Calibration and Acceptance Facility, the Nondestructive Evaluation Facility, and the Gas Analysis Laboratory currently occur at Pantex Plant. The only change in their emissions would be a change in their location.
The HWTPF and Pit Reuse Facility would be new facilities. The HWTPF and Pit Reuse Facility will use high efficiency particulate air (HEPA) filters to reduce particulate emissions. The HEPA filters have a collection efficiency of 99.97 percent. Activated charcoal canisters or equivalent equipment would be used to absorb organic gases at the HWTPF. These filter systems are capable of controlling both radioactive and nonradioactive pollutants. Since the emissions from this facility would be reduced to very low levels, air quality impacts would be negligible.
Overall, the emissions from these new or upgraded facilities would not produce ambient concentrations that would exceed the NAAQS or the Texas ESLs. In addition, no increases in radiological emissions are anticipated. Therefore, the air quality impacts would be negligible.
4.7.2.3 Summary of Impacts
An analysis of pollutant emissions and ambient concentrations resulting from Proposed Action activities found that air quality standards or guidelines would not be violated beyond the Pantex Plant boundary. Specifically, maximum ambient concentrations that would occur at the 11 residences near the boundary were found to be below the NAAQS and Texas ESLs. Therefore, air quality impacts resulting from the Proposed Action would be negligible.
4.7.3 Impacts of No Action Alternative
Weapon-Related ActivitiesThe major difference between this alternative and the Proposed Action is that weapons disassembly operations would cease when 12,000 pits have been placed in interim storage at Pantex Plant. However, the requirement to support the weapons stockpile with other operations, including weapons assembly, modification, and surveillance activities will continue. Three weapon levels2,000, 1,000, and 500are assumed for analysis. In addition, no upgrade projects would be initiated under the No Action Alternative. Therefore, there would be no emissions from construction under this alternative.
Since the activities related to the assembly of weapons produce chemical and radiological pollutant emissions similar to those produced by disassembly, the ambient concentrations resulting from the three levels of weapons for this alternative would be approximately the same as those described in the Proposed Action (section 4.7.2.1). No operational emissions or air quality impacts above those described in the affected environment would occur because new facility upgrades would not be implemented under this alternative. Therefore, it may be concluded that the air quality impacts resulting from continued operation under the No Action Alternative would be similar to the Proposed Action; i.e., impacts would not be significant.
Pit Storage Activity (12,000 Pits Only)The emissions resulting from pit storage activity would be the same as those for the Proposed Action (section 4.7.2.1). Indirect emissions from Safe Secure Tractor Trailers hauling weapons or pits to Pantex Plant would be only a small fraction of the total Pantex Plant emission inventory. Also, once the storage limit of 12,000 pits has been reached, the emissions related to this activity would cease. Thus air quality impacts resulting from the storage of 12,000 pits would be negligible.
Environmental Restoration ActivitiesER activities under the alternative would proceed in the same manner as under the Proposed Action (section 4.7.2.1). Emissions related to soil disturbance activities would be minimized through the application of water. Particulate emissions would not cause PM10 standards to be violated offsite. Air quality impacts would be negligible.
Waste Management ActivitiesWaste management activities under this alternative would be the same as under the Proposed Action. The emissions from these activities were included in the site-wide dispersion modeling for the Proposed Action. Air quality impacts for waste management activities under this alternative would also be negligible.
4.7.4 Impacts of Pit Storage Relocation Alternative
4.7.4.1 Impacts of Relocating 20,000 Pits
The Pit Storage Relocation Alternative includes all operations, upgrades, and modifications of the Proposed Action. Emissions resulting from activities related to the relocation of 20,000 pits would be added to those of the Proposed Action (see section 4.7.2.1). Indirect emissions from exhausts of the vehicles required to haul the pits to the alternative sites would be the only chemical or radiological emissions associated with the Pit Storage Relocation Alternative. These additional pollutant emissions would constitute a small fractional increase in the site-wide emission inventory of the Proposed Action. This small emission increase would not produce any detectable change in the ambient concentrations described in the Proposed Action. Therefore, as in the case of the Proposed Action, air quality impacts would not be significant.
4.7.4.2 Impacts of Relocating 8,000 Pits
Emissions resulting from the relocation of 8,000 pits would be less than the emissions from the relocation of 20,000 pits. Therefore, as described in the previous section, the air quality impacts of relocating 8,000 pits would not be significant.
4.7.5 Cumulative Impacts
The cumulative impacts presented here include impacts of the continued operations at Pantex Plant combined with impacts associated with activities described in the WM PEIS, SSM PEIS, and S&D PEIS. Since the Pantex Plant EIS Proposed Action and the SSM PEIS No Action Alternative represent a continuum of operations, the impacts associated with any new mission or facility that could be implemented at Pantex Plant are discussed in the context of that continuum. The impacts from the WM PEIS program are combined with those of the Pantex Plant EIS Proposed Action. The impacts from the S&D PEIS are combined with those of the SSM PEIS No Action Alternative. A detailed discussion of this methodology is presented in section 4.2.
4.7.5.1 Impacts of Alternatives in the Waste Management Programmatic Environmental Impact Statement
The WM PEIS evaluated alternatives for the construction and operation of LLMW and LLW waste facilities at Pantex Plant. None of the alternatives are expected to cause an exceedance of air quality standards. For a discussion of the atmospheric release effects on human health related to a chemical or radiological accident, see section 4.14.5.1 in this volume.
4.7.5.2 Impacts of Alternatives in the Stockpile Stewardship and Management Programmatic Environmental Impact Statement
The SSM PEIS includes three alternatives that apply to Pantex Plant: No Action, Downsize Existing Capability, and Relocate Capability. Under the No Action Alternative, no downsizing or modification of facilities would occur. Due to the reduced workload expected in the future, air quality impacts from operations are expected to be less than current impacts. Air quality would remain within regulatory limits. Under the downsizing alternative, the operations would be consolidated. Air quality impacts would be equivalent to those of the No Action Alternative. Under the Relocation Alternative, air quality impacts from assembly and disassembly operations and HE fabrication would cease.
4.7.5.3 Impacts of Alternatives in the Storage and Disposition of Weapons-Usable Fissile Materials Programmatic Environmental Impact Statement
The S&D PEIS is considering Pantex Plant for long-term storage of inventories of nonsurplus weapons-usable plutonium and highly enriched uranium (HEU), storage of inventories of surplus weapons-usable plutonium and HEU pending disposition, and disposition of surplus weapons-usable plutonium. For storage, the strategy for long-term storage of weapons-usable plutonium and HEU, as well as the storage site(s), would be decided. The storage alternatives include upgrading the existing plutonium storage facilities, consolidation of plutonium from other sites, and collocation of plutonium and HEU storage. The collocation alternative is used for analysis purposes in this EIS as the bounding storage alternative.
Under the S&D PEIS Collocation Alternative, construction of new storage facilities would be required in order to store plutonium and HEU at Pantex Plant. Increased PM10 and total suspended particle concentrations may occur during the peak construction period, particularly during dry and windy conditions. Appropriate control measures would be followed to minimize pollutant concentrations during construction. Concentrations of all pollutants at the site boundary would remain within applicable Federal and State ambient air quality standards. During operation, concentrations of criteria and toxic or hazardous air pollutants are predicted to be in compliance with Federal, State, and local air quality regulations or guidelines (DOE 1996a:chapter 4).
For the disposition alternatives in the S&D PEIS, the emphasis at this stage in the NEPA decision process is on choosing the strategy and technology mix rather than the actual site. The evolutionary Light Water Reactor is used for analysis purposes in this EIS as the bounding Disposition Alternative. Implementation of this disposition alternative would require the construction and operation of a pit disassembly and conversion facility, plutonium conversion facility, MOX fuel fabrication facility, and one or more light water reactors. The bounding alternative also assumes that all of the facilities previously mentioned would be collocated at the same site (potentially Pantex Plant).
4.7.6 Potential Mitigation Measures
Although the air emissions do not involve significant impacts, DOE used Best Available Control Technology as defined in TNRCC regulation and will continue to do so, to identify operational areas where improvements can be made in the management practices. An example is the ongoing substitution of newer, more environmentally benign cleaning solvents.
DOE may chose one or more of the following measures to alleviate the temporary dust emissions from construction activities. These measures could include covering, watering, or applying nontoxic solid binders to exposed piles of gravel, sand, dirt; and suspending all excavation and grading operations when wind speeds are exceedingly high.
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