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PUBLIC HEALTH ASSESSMENT
 

EVALUATION OF POTENTIAL EXPOSURES TO CONTAMINATED OFF-SITE GROUNDWATER FROM THE OAK RIDGE RESERVATION (USDOE)
OAK RIDGE, ANDERSON COUNTY, TENNESSEE


I. SUMMARY

In 1942, the federal government established the Oak Ridge Reservation (ORR) in Anderson and Roane Counties in Tennessee as part of the Manhattan Project to research, develop, and produce special radioactive materials for nuclear weapons. Four facilities were built at that time. The Y-12 Complex, the K-25 site, and the S-50 site were created to enrich uranium. The X-10 site was created to demonstrate processes for producing and separating plutonium. Since the end of World War II, the role of the ORR (Y-12 Complex, K-25 site, and X-10 site) broadened widely to include a variety of nuclear research and production projects vital to national security.

In 1989, the ORR was added to the U.S. Environmental Protection Agency's (EPA's) National Priorities List (NPL) because, over the years, the ORR operations have generated a variety of radioactive and nonradioactive wastes that a portion of which remain in old waste sites and some pollutants have been released into the environment. The U.S. Department of Energy (DOE) is conducting clean up activities at the ORR under a Federal Facility Agreement (FFA) with EPA and the Tennessee Department of Environment and Conservation (TDEC). These agencies are working together to investigate and take remedial action on hazardous waste from past and present activities at the site.

ATSDR is the principal federal public health agency charged with evaluating human health effects of exposure to hazardous substances in the environment. Prior to this public health assessment, ATSDR addressed current public health issues related to off-site areas, including the East Fork Poplar Creek area and the Watts Bar Reservoir area.

I.A. Scope of this Public Health Assessment

This public health assessment is focused solely on evaluating the potential off-site exposures to contaminated groundwater emanating from ORR. Exposures to groundwater within the ORR boundaries are not considered in this document. Likewise, exposures to contaminated surface water will not be evaluated in this document – even though this contamination may be a result of discharge from contaminated groundwater. Exposure to contamination in surface water and other media is addressed in other ATSDR public health assessments including: Current & Future Chemical Exposure Evaluation (1990-2003), White Oak Creek Radionuclide Releases, and Y-12 Mercury Releases PHA's.

The overall goal of this PHA is to determine the potential public health hazard posed by historical releases of contaminants to groundwater. It will accomplish this goal by evaluating all currently available groundwater monitoring data as well as demographic and current and historical land and groundwater use information. This information will be used to determine whether members of the community are being exposed to contaminated groundwater emanating from ORR. Another goal of this PHA is to fully address specific community concerns solicited by ATSDR as part of the public health assessment process about site-related public health issues relating to exposure to off-site groundwater.

I.B. ATSDR's Evaluation of Exposure to Contaminated Off-Site Groundwater

Based on available data, off-site contamination has only occurred in monitoring wells and seeps/springs in Union Valley, and residential wells have been unaffected by contamination resulting from ORR activities. Since nearly all groundwater beneath the ORR ends up as surface water before leaving the site, community exposure to contamination via off-site groundwater is unlikely.

The east end volatile organic compound (EEVOC) groundwater contaminant plume, extending east-northeast from the Y-12 Complex, is the only confirmed off-site contaminant plume migrating across the ORR boundary. This carbon-tetrachloride dominated plume is actually several contaminant plumes that have commingled and have migrated east-northeast off-site into Union Valley. Institutional controls are set forth in the Interim Record of Decision for Union Valley (Jacobs EM Team, 1997), in which, DOE requires license agreements with property owners whereby DOE will notify them of the potential of contamination and requiring property owners to inform DOE 90 days prior to any changes in groundwater use. It also requires appropriate verification by DOE of compliance with the agreements and notification of state and local agencies. While this selected action does not provide for reduction in toxicity, mobility or volume of contaminants of concern, ATSDR scientists conclude that it is protective of public health to the extent that it limits or prevents community exposure to contaminated groundwater in Union Valley.

ATSDR scientists have concluded that there is no exposure to contaminated groundwater emanating from ORR. Therefore, the groundwater does not pose a public health hazard. Sufficient evidence exists that no human exposures to off-site contaminated groundwater have occurred, no exposures are currently occurring, and exposures are not likely to occur in the future (ATSDR 2005). ATSDR also examined the possibility of vapor intrusion of VOCs into an office building which partially overlies the EEVOC plume. Conservative modeling results estimate indoor vapor concentrations several orders of magnitude below Occupational Safety and Health Administration and National Institutes for Occupational Safety and Health guidelines. ATSDR scientists have concluded that exposure via vapor intrusion does not represent a health threat.


II. BACKGROUND

II.A. Site Description

In 1942, during World War II, the U.S. government developed the Oak Ridge Reservation (ORR) under the Manhattan Project initiative to produce and study nuclear material needed to make nuclear weapons (ChemRisk 1993b). The ORR is located in eastern Tennessee, in the city of Oak Ridge, approximately 15 miles west of Knoxville; it is situated in both Roane and Anderson Counties. The southern and western borders of the ORR are formed by the Clinch River, and most of the reservation lies within the Oak Ridge city limits. The ORR plants are isolated from the city's populated areas. Figure 1 shows the location of the ORR.

When the federal government acquired the ORR in 1942, the reservation consisted of 58,575 acres (91.5 square miles). Since that time, the federal government has transferred 24,340 (38.0 square miles) of the original 58,575 acres to other parties (e.g., City of Oak Ridge, Tennessee Valley Authority [TVA]); the U.S. Department of Energy (DOE) continues to control the remaining 34,235 acres (53.5 square miles) (Jacobs Engineering Group Inc. 1996; ORNL 2002).

Under the Manhattan Project, the government constructed four facilities at the ORR. The X-10 site (formerly known as the Clinton Laboratories and is now part of what is referred to as the Oak Ridge National Laboratory [ORNL]) was built to produce and separate plutonium. The K-25 site (formerly known as the Oak Ridge Gaseous Diffusion Plant [ORGDP] and now referred to as the East Tennessee Technology Park [ETTP]), the Y-12 plant (now known as the Y-12 National Security Complex), and the former S-50 site (now part of the ETTP) were developed to enrich or process uranium (ChemRisk 1993b; Jacobs Engineering Group Inc. 1996; TDEC 2002; TDOH 2000).

Location of the Oak Ridge Reservation
Figure 1. Location of the Oak Ridge Reservation

II.B. Site Geology/Hydrogeology

ORR is located in the East Tennessee Valley, which is part of the Valley and Ridge Province of the Appalachian Mountains. The East Tennessee Valley is bound to the west by the Cumberland Mountains of the Appalachian Plateau Province and to the east by the Smokey Mountains of the Blue Ridge Province. The defining characteristics of the Valley and Ridge Province are the southwest trending series of ridges and valleys caused by crustal folding and faulting due to compressive tectonic forces as well as the differential weathering of the various formations underlying the area.

The contaminated areas on the ORR were separated into large tracts of land that are typically associated with the major hydrologic watersheds (EUWG 1998). These watersheds are:

  1. East Tennessee Technology Park (ETTP) Watershed
  2. Bethel Valley Watershed
  3. Melton Valley Watershed
  4. Bear Creek Valley Watershed
  5. Upper East Fork Poplar Creek (UEFPC) Watershed

For the purposes of this health assessment, the ETTP Watershed will be discussed independently, but the Bethel Valley and Melton Valley Watersheds will be discussed together, as will the Bear Creek Valley and UEFPC Watersheds. These groupings were made based on the similar hydrogeology of watersheds as well as the similarity of the nature of ORR operations in each watershed.

The vast majority of information available concerning the geology and hydrogeology of the site indicates that groundwater occurs as shallow flow with short flow paths to surface water (ORNL 1982, MMES 1986, USGS 1986b, USGS 1988, USGS 1989, USDOE 2004, SAIC 2004). The fractures and solution cavities, which are common in this karst region, occur in shallow (0-100 ft. deep) bedrock and significantly decrease at depth (>100 ft. deep). In the aquitard formations (see Table B-1) as much as 95% of all groundwater occurs in the shallow zone and discharges into local streams and eventually into the Clinch River. In the aquifer formations, the Knox Aquifer being the most important, solution conduits can make flow paths much deeper and longer along strike; however, there is no evidence of deep regional flow off of the ORR or between basins (USDOE 2004). Please refer to Appendix B for a discussion of ORR geology and general groundwater flow principles relative to the area.

It is important to note that conclusions reached in this Public Health Assessment are based upon currently available data and are limited by the uncertainties inherent in both the data and the general nature of karst groundwater systems. Please refer to Appendix B for a discussion of karst systems on and around the ORR and their impact on groundwater flow.

Groundwater beneath the ORR is typically very shallow and approximately 95% ends up as surface water before leaving the site boundary (USDOE 2004).

It is unlikely that contaminated groundwater at the ORR will flow beneath, and continue to flow away from, streams and rivers that surround the site. There is an extensive interconnection between groundwater and surface water and groundwater contamination sources on the ORR are primarily in the shallow subsurface (with the exception of deep-well injection conducted at ORNL, which will be discussed in the Melton Valley Watershed section of this document). Furthermore, core samples have shown that beneath the alluvium at the bottom of the stream beds in this area is a silty-clay horizon that likely impedes downward groundwater movement (USGS 1989). The incised meander (see Appendix A) of the Clinch River in bedrock also represents a major topographic feature that prevents groundwater from passing beneath the river (ORNL 1982). ATSDR scientists conclude that on-site contaminated groundwater does not likely migrate beneath and away from streams and rivers either as slug-flow or in fractures, solution channels, or other conduits in the bedrock.

II.C. Off-Site Groundwater Data

ATSDR scientists queried the Oak Ridge Environmental Information System (OREIS) Database for all groundwater sampling data from residential wells, monitoring wells, and from seeps and springs. The query resulted in over 2150 on-site sampling locations and over 120 off-site sampling locations with hundreds of thousands of data points with dates ranging from the mid 1980's to 2004. The specific sources of data are:

  • ORNL Groundwater Monitoring Data (1991-2004)
  • ORNL Bethel Valley Watershed RI 1997
  • ORNL White Oak Creek Watershed RI 1996
  • Y-12 Upper East Fork Poplar Creek RI 1997
  • Y-12 Groundwater Protection Program (Ongoing)
  • ORR Integrated Water Quality Program 1998
  • ORR Water Resources Restoration Program (Ongoing)
  • ORR Remediation Effectiveness Reports (2000-2005)
  • K-25, K-1070-A Burial Ground – Brashears Creek
  • Lower East Fork Poplar Creek Operable Unit
  • Atomic City Auto Parts Site Characterization
  • TDEC Environmental Monitoring Reports (through 2003)

In 1996, TDEC initiated a residential well sampling program. Seventy-one (71) residential wells were identified for sampling. Most were situated southwest and within 2 miles of ORR boundaries because, based on the hydrology and geomorphology of the area, these were the areas most likely affected by contaminated groundwater from ORR. In conjunction with the residential well sampling program, TDEC conducted a house-to-house survey of homeowners about their concerns with groundwater. The results of this survey revealed that there were no anecdotal problems with groundwater quality. The analytical results of the residential well sampling program indicated that there was no "discernable" impact on residential wells from activities on the ORR (TDEC 2004).

These sampling locations were first separated into on- and off-site locations. Since this health assessment focuses on off-site (outside ORR boundaries) exposure to groundwater contamination, only off-site sampling data were evaluated. Next, the sampling locations were differentiated based whether they came from residential wells, monitoring wells, or from seeps and springs. A further distinction was made based upon proximity of the sampling locations to the main facilities of ORR: near ETTP, near ORNL, or near the Y-12 Complex. Maps are included (Figure 4, Figure 8, and Figure 14) and sampling results will be discussed for each area in the respective sections.

The only data gaps that were identified during the data evaluation process were the relative irregularity of residential well sampling. These wells are not regularly and systematically sampled in the same way that monitoring wells are. In TDEC's 2005 Environmental Monitoring Plan (TDEC 2005), "older" residential wells are typically only sampled when there is a specific request or other justification to do so. In the mid-1990's, when the majority of available data in the OREIS database was collected, TDEC conducted a sweeping residential well sampling as part of their 1996 Residential Well Sampling Program. Newly installed residential wells are included in the current (2005) sampling plan.

It should be noted that TDEC's residential well sampling program was never intended to be a comprehensive characterization of off-site well contamination. So, we include the lack of residential well sampling data as a "data gap" not to criticize the efforts of TDEC but to highlight an area where sufficient data is unavailable.

II.D. East Tennessee Technology Park (ETTP) Watershed

The 1,700-acre K-25 site, which includes the former S-50 plant (37 acres), is now called the East Tennessee Technology Park (ETTP). The K-25 site is close to the ORR's western border (Figure 2); it is situated along Poplar Creek, near the creek's confluence with the Clinch River in Roane County, approximately 10 miles west of downtown Oak Ridge (ChemRisk 1999a; U.S. DOE 1996).

Operational History

In October 1944, the S-50 plant started separating uranium by liquid thermal diffusion; the plant closed in September 1945. The K-25 site was used from 1945 to 1964 to enrich weapons-grade uranium through gaseous diffusion. From 1965 to 1985, the site used uranium hexafluoride in the gaseous diffusion process to manufacture commercial-grade uranium. All gaseous diffusion operations ceased at the site in 1985, and the site was closed in 1987. Since 1996, reindustrialization has been the focus of the K-25 site, which now houses two business centers—the Heritage Center and the Horizon Center. The site also maintains the Toxic Substances and Control Act (TSCA) incinerator; it is the only facility in the country authorized to incinerate wastes with radioactive and hazardous contaminants that contain PCBs.

Geology/Hydrogeology

The ETTP was constructed almost entirely on the limestone bedrock of the Chickamauga Group (see Figure B-1). The Chickamauga Group is between 450 and 600 meters thick in the Oak Ridge area. Although the formation is predominantly limestone in composition, it resists dissolution and large cavities are rare. Consequently, water storage remains near the surface in the unconsolidated zone because of the low hydraulic conductivity of the bedrock. Cracks and fissures do occur in the Chickamauga Group and, therefore, prevent any prediction of groundwater flow direction and rate in the bedrock (MMES 1986, USGS 1986B, USGS 1988, USGS 1989, SAIC 2004). However, since these cracks and fissures decrease with depth, deep groundwater flow is very limited. The Chickamauga Group is considered a flow-limiting aquitard (ORNL 1982, MMES 1985, USGS 1997). The lithology of the Rome Formation, which underlies the southeastern portion of the ETTP, consists of shales and siltstones which have typically low hydraulic conductivities; however, due to the complex fractures and fissures in this formation, it is also nearly impossible to accurately predict a flow path for groundwater in this formation (Figure 3).

Because the local water table occurs just below the surface in the unconsolidated zone, groundwater flow is generally consistent with the surface topography. However, the rate and direction of groundwater flow in the ORR vary, and are often affected by fluctuations in precipitation as well as flood control operations both up and down stream. Groundwater recharge comes from diffuse rainwater infiltration through the permeable, well-drained silty soils typical of the area. However, during high precipitation events, the clay content in the soil can prevent rapid infiltration and may result in significant surface run-off. Groundwater discharge occurs through evapotranspiration during the spring and summer months, but is predominantly discharged into surface water via seeps and springs. Most groundwater at ORR ultimately ends up in the Clinch River serving as base flow for small streams and tributaries, including Mitchell Branch and Poplar Creek near the ETTP area (MMES 1985, SAIC 2004).

Contamination at ETTP

The primary contaminants in sediments at ETTP are inorganic elements, radionuclides, and polychlorinated biphenyls (PCBs). In soils, the contaminants of concern include inorganic elements, radionuclides, semi-volatile organic compounds (SVOCs), polyaromatic hydrocarbons (PAHs), and VOCs. However, the primary contaminants of concern in groundwater at ETTP are VOCs. Dye tracing has been used to identify exit points for groundwater discharge to surface waters around the ETTP. Monitoring wells have been installed at each of these exit points to evaluate contaminant concentrations in these areas and to monitor the migration of known contaminant plumes. As of FY 2003 sampling, volatile organic compound (VOC) concentrations have shown a general decreasing trend at exit point monitoring wells. Results from monitoring of the bedrock well (BRW-083) and the unconsolidated zone well (UNW-107) near the confluence of Mitchell Branch and Poplar Creek, have shown no detectable levels of VOCs (Figure 2). These wells are considered a significant exit point for several commingling groundwater plumes emanating from the eastern portions of ETTP, including the K-1070-C/D burial grounds and the K-1401 area.

Testing at exit point monitoring wells BRW-035 and BRW-068, between the K-901 holding pond and the Clinch River, have occasionally shown low concentrations of TCE and 1,2-DCE, chloroform, gross alpha and gross beta activity; all below the respective MCLs. VOC contaminated groundwater does, however, discharge to surface water from several seeps and springs north of the K-901 holding pond including Spring 21-002.

Another significant contaminant source area for the ETTP is the K-27 building. VOC concentrations in the groundwater in this area range from 20 µg/L (UNW-096) to 130 µg/L (UNW-038). Both of these unconsolidated zone monitoring wells are southwest of K-27 along Poplar Creek. Monitoring wells (BRW-016) north of K-27 along Poplar Creek typically reveal TCE degradation products such as cis-1,2-DCE and vinyl chloride. FY 2003 sampling from BRW-016 revealed vinyl chloride concentrations slightly above the MCL of 2 µg/L.

As is the case north of K-27, the distal portions of the commingled VOC plumes near the Mitchell Branch are largely composed of TCE degradation products cis-1,2-DCE and vinyl chloride. In both cases, this can indicate that the source of contamination is significantly upgradient or the source of contamination has been eliminated. It could also be a result of increased biodegradation in those particular areas. Based on monitoring data from FY 2003 collected from known and suspected exit point locations, contaminant (largely VOC) concentrations have either remained constant or have decreased from previous years. These steady or decreasing groundwater concentrations have also resulted in decreased impact on ETTP perimeter surface waters. VOC concentrations from the Mitchell Brach weir (K-1700 – see Figure 3 inset) have decreased from 1997-98 (SAIC 2004).

On-Site Groundwater Monitoring Locations at ETTP
Figure 2. On-Site Groundwater Monitoring Locations at ETTP

Conceptual Model of Groundwater Flow and Contaminant Transport at ETTP
Figure 3. Conceptual Model of Groundwater Flow and Contaminant Transport at ETTP

Off-Site Groundwater Monitoring Data

Seeps and Springs

Comparison values are doses or substance concentrations set well below levels that are known or anticipated to result in adverse heath effects (ATSDR 2005) — see Appendix A.

Lead and manganese were the only substances detected above comparison values (CVs) in seeps and springs near ETTP. Lead was only detected in five samples out of 28. Three out of those were above the 15 ppb MCL for lead. Of the 12 detected samples of manganese, only one sample was above the 500 ppb CV for manganese. For both substances, all samples that were detected above the respective CVs were taken from the CCC Well #2 (See Figure 4). Samples taken from an adjacent location (CCC Well #1) on the same day(s) were below detection limits for both substances.

Table 1: Contaminants Detected Above Comparison Values in Seeps or Springs Near ETTP

Substance

Detects / Samples

Samples Detected Above CVs

CV (ppb)

Max Conc. (ppb)

Max Location

Max Conc. Date

Lead

5 / 28

3

15

95.4

CCC Well #2

3/5/1996

Manganese

12 / 15

1

500

995

CCC Well #2

9/8/1995

Monitoring Wells

There were no contaminants detected above CVs in monitoring wells outside of the ORR boundaries near the ETTP.

Residential Wells

The only contaminant detected above CV in residential wells near ETTP is boron. Boron has been detected in four samples from four different wells collected on September 22, 1998. Only one of these samples was detected above the 100 ppb CV. This sample was taken from RW-A-15 and yielded a boron concentration of 154 ppb. No subsequent sampling has been conducted at these wells.

ATSDR Conclusion for the ETTP Watershed

Lead, manganese and boron are naturally occurring elements. Lead and manganese were both detected above CVs in seeps outside the ORR. Because neither lead nor manganese could be detected in samples collected concurrently at adjacent sampling locations, it is unlikely that these substances are associated with groundwater contamination. Likewise, boron was only detected above it's CV in one sample. Concurrent sampling at adjacent wells revealed concentrations well below the CV. Exit pathway monitoring wells are being continually monitored as part of the Water Resources Restoration Program for ETTP. Groundwater contamination at ETTP does not migrate off-site; rather, it is discharged into surface water. The ETTP Environmental Monitoring Plan includes surface water surveillance (ORNL 2004). ATSDR scientists conclude that the public (community) is not being exposed to groundwater contamination from ETTP.

Off-Site Groundwater Sampling Locations Near ETTP
Figure 4. Off-Site Groundwater Sampling Locations Near ETTP

II.E. Bethel Valley Watershed and Melton Valley Watersheds

The X-10 site, now known at the Oak Ridge National Laboratory (ORNL) is about 10 miles southwest of the city center of Oak Ridge in Roane County, and encompasses approximately 26,580 acres. It is surrounded by heavily forested ridges that include Chestnut Ridge, Haw Ridge, and Copper Ridge (ChemRisk 1999a; TDOH 2000). The X-10 Site is situated within two watersheds – Bethel Valley and Melton Valley (ORNL et al. 1999). The main laboratory at X-10 is located along Bethel Valley Road, within Bethel Valley (ChemRisk 1999a; ORNL et al. 1999). The X-10 site also contains remote facilities and waste storage areas in Melton Valley (ORNL et al. 1999). White Oak Creek begins in Bethel Valley and flows south along the eastern border of the plant and travels through a gap in Haw Ridge before entering Melton Valley. From Melton Valley, White Oak Creek joins the Clinch River below Melton Hill Dam (ChemRisk 1999a). See Figure 1 for the location of White Oak Creek and the relationship between X-10, White Oak Dam, the Clinch River, and the Watts Bar Reservoir.

Operational History

Beginning in the early 1940s, radioactive material was used on the ORR for various processes, such as uranium enrichment, plutonium production, plutonium separation, and the development of separation processes for additional radionuclides (ChemRisk 1993b; Jacobs Engineering Group Inc. 1996). The X-10 site was built in 1943 as a "pilot plant" to demonstrate plutonium production and chemical separation. The government had intended to operate the facility for only one year. However, this initial time period was extended indefinitely as operations were continued and expanded at X-10 (ChemRisk 1999a; TDOH 2000). After World War II, the facility's focus was broadened to include non-weapons related activities, such as the physical and chemical separation of nuclear products, the creation and assessment of nuclear reactors, and the production of a range of radionuclides for global use in the medicinal, industrial, and research disciplines (ChemRisk 1993b). In the 1950s and 1960s, the X-10 site became a worldwide research center to study nuclear energy and to investigate the physical and life sciences that are related to nuclear energy. From 1958 to 1987, the Oak Ridge Research Reactor operated to support various scientific experiments at X-10. For a long period of time, this reactor was the main radionuclide supplier to the "free world" for medical, research, and industrial purposes (Johnson & Schaffer 1992, Stapleton 1992, and Thompson 1963 as cited in ChemRisk 1993b).

Geology/Hydrogeology

The entire X-10 site was built on the Chickamauga Group (see Figure B-1). This aquifer formation is a flow limiting strata that has a relatively low hydraulic conductivity. This formation is subject to upper-level fracturing, but these cracks and fissures are typically only a few centimeters wide and serve more as groundwater storage as opposed to facilitating the spatial movement of groundwater (MMES 1985). Haw Ridge separates Bethel Valley from Melton Valley. This ridge was formed partially from thrust faulting by compressive tectonic forces millions of years ago. It is also a result of differential weathering. Underlying Haw Ridge is the Rome Formation. This siliciclastic formation is composed primarily of siltstone, sandstone and shale (USGS 2004). The Rome formation is more resistant to weathering than the Chickamauga Group, which underlies the Bethel Valley to the north, and the Conasauga Group, which underlies Melton Valley to the south.

Major Remedial Activities in Bethel Valley
Figure 5. Major Remedial Activities in Bethel Valley

Groundwater in the ORR area generally occurs in the unconsolidated zone. Depth to the water table, depending on seasonal variability, in the Bethel Valley ranges from 1 to 35 feet and from 1 to 67 feet in Melton Valley. Groundwater flow paths most often mirror the surface topography with diffuse discharge to surface waters or as discharge via springs and seeps (Figure 7). In the Bethel Valley, there is a hydrologic divide separating surface water flow in the western third of the watershed. West of the divide, surface water and groundwater flow west to Raccoon Creek (Figure 6) and eventually into the Clinch River. East of the divide, waters flow east to White Oak Creek. Groundwater flow generally follows these topographic trends and flow paths to surface water are relatively short (ORNL 2004).

White Oak Creek flows through a gap in Haw Ridge from Bethel Valley to Melton Valley. Soils in the Melton Valley area, overlying the Conasauga Shale, have a low primary porosity and therefore, have a low storage capacity. The common concept of contaminated groundwater plume migration is not appropriate in this area because of the shallow active zone and the interaction with surface water. The water that infiltrates into the upper weathered zone eventually discharges into streams via the "bathtub effect" – where water collects in a low area, or trench, causing an overflow at the down gradient end (MMES 1985). This overflow occurs as springs or seeps from which water flows downhill to creeks and streams (Figure 7).

Contamination in Bethel Valley and Melton Valley

The major operations at X-10 take place within the Bethel Valley Watershed. The main plant, key research facilities, primary administrative offices, as well as various forms of waste sites, are situated in Bethel Valley. Over the past 60 years, X-10 releases have contaminated the Bethel Valley Watershed. Mobile contaminants primarily leave the Bethel Valley Watershed via White Oak Creek. These contaminants travel from the Bethel Valley Watershed to the Melton Valley Watershed, where further contaminants enter White Oak Creek. Then, the contaminants that have been discharged to White Oak Creek are released over White Oak Dam and into the Clinch River (U.S. DOE 2001d).

Bethel Valley Contamination

For the purpose of environmental investigation and remediation, the Bethel Valley area was subdivided into four regions. The regions are; Raccoon Creek, West Bethel Valley, Central Bethel Valley, and East Bethel Valley (Figure 6). The Raccoon Creek area lies on the western most portion of the valley west of Highway 95. West Bethel Valley lies east of Highway 95 and west of the ORNL main plant area. While the Raccoon Creek area does not have any known contaminant source areas, West Bethel Valley contains a burial ground (SWSA 3) and adjacent landfills, which have resulted in soil and groundwater contamination in both West Bethel Valley as well as Raccoon Creek. Radiological wastes were stored in SWSA 3 from 1946 to 1951 from DOE facilities all over the country. The SWSA 3 and the adjacent landfills cover approximately 18 acres in Bethel Valley. Over the years, seasonal surface water infiltration and heavy rain events have resulted in contaminant leaching from SWSA 3 and the adjacent landfills. Subsurface contaminant movement was short, flowing to Raccoon Creek to the southwest, and northeast to the Northwest Tributary (SAIC 2004).

Conceptual Model of Groundwater Flow and Contaminant Transport in Bethel Valley
Figure 6. Conceptual Model of Groundwater Flow and Contaminant Transport in Bethel Valley

While the Raccoon Creek and the West Bethel Valley areas have relatively small defined contaminant release areas, the Central and East Bethel Valley areas have extensive soil and groundwater contamination. The Central Bethel Valley contains the main ORNL plant site and has over 150 sites that have been identified for environmental restoration (SAIC 2004). The leading areas of concern in terms of groundwater contamination in the Central Bethel Valley are the Corehole 8 plume and in some building sumps which have tested positive for mercury contamination (Figure 5). However, the only groundwater plume that is regularly monitored on a watershed scale is the Corehole 8 plume (SAIC 2004).

The Corehole 8 Plume, which was identified at X-10 in 1991, is a plume of groundwater that is contaminated with Sr 90 (SAIC 2002, U.S. EPA 2002a). In 1994, a removal site evaluation revealed that contaminated groundwater was leaching into X-10's storm drain system and was being released into First Creek. First Creek is a stream that feeds into White Oak Creek and ultimately flows into the Clinch River. Additional evaluation indicated that the contaminated groundwater was seeping into the storm drain system via three catch basins on the western portion of X-10 (SAIC 2002). In November 1994, an action memorandum was approved; by March 1995, a groundwater collection and transmission system was being used at the Corehole 8 Plume to prevent groundwater infiltration (SAIC 2002, U.S. EPA 2002a). Through this system, groundwater is treated by X-10's Process Waste Treatment Plant (PWTP) and then released through a National Pollutant Discharge Elimination System (NPDES) outfall.

In August 1995, DOE prepared a removal action report that required monthly monitoring of the storm drain outfall close to the joining of First Creek and the Northwest Tributary (Figure 5). In addition, based on suggestions from the 1997 remediation effectiveness report (RER), monthly composite samples are taken at this area, as well as at the Corehole 8 sump (SAIC 2002). Surface water monitoring in October 1997 revealed elevated levels of Sr 90 and uranium 233 (U 233) in First Creek. In December 1997, further investigation indicated that this contamination was entering the area through two unlined storm drain manholes. As a result, in March 1998, DOE established another interceptor trench that linked to one of the plume's collection sumps. An addendum to the original action memorandum was approved in September 1999. This addendum, which was intended to increase the effectiveness of the initial remedial action, endorsed more groundwater extraction and treatment activities at the Corehole 8 Plume (SAIC 2002, SAIC 2004). The source of the Corehole 8 plume is the W-1A tank in the North Tank Farm. This tank was commissioned in 1951 to receive LLLW from Buildings 3019, 3019B, and 2026, but use of the tank was discontinued in 1986 because of leaks in the transfer lines. Grab samples of soil around the W-1A tank revealed extremely high levels of transuranic waste (TRU). The tank is still in place because it was determined that removal of the tanks would result in a high dose rate to the workers (SAIC 2004).

Melton Valley Contamination

In the late 1950's, scientists at ORNL began experimenting with injecting low-level radioactive waste mixed with a Portland cement into induced fractures of the underlying bedrock. The geologic formation involved was a low-permeability formation of the Conasauga Group called the Pumpkin Valley Shale. Two experimental sites were developed for testing of this disposal method. The first was Hydrofracture-1 (HF-1) and the other was HF-2. At each site twenty-four observation and monitoring wells were installed. Various experiments revealed that the Pumpkin Valley Formation could effectively and safely contain the contaminated grout. Continued experimental and, later, successful operational waste disposal was performed at two other injection sites (Old Hydrofracture Facility and New Hydrofracture Facitily – OHF and NHF) until operations were halted in 1982. The Underground Injection Control regulations promulgated by the USEPA effectively eliminated hydrofracture waste injections at ORNL (SAIC 1997, ORNL 2000). In 2000, Bechtel Jacobs Company LLC (BJC) contracted Tetra Tech NUS, Inc and their sub-contractor Texas World Operations, Inc. to perform the plugging and abandonment (P&A) of 111 wells in Melton Valley (Whiteside et al. 2002). As of FY 2002, demolition and deconstruction activities at OHF were completed and 110 of 111 hydrofracture wells have been plugged and abandoned (P&A) exceeding ALARA principles on the project (SAIC 2004, Whiteside et al. 2002). Contaminated grout is expected to remain in the induced hydrofractures in the Pumpkin Valley Shale or within boreholes or wells penetrated by grout. There is no known contribution to surface water contamination from hydrofracture waste (SAIC 1997).

Surface Water and Shallow Groundwater Flow in Melton Valley
Figure 7. Surface Water and Shallow Groundwater Flow in Melton Valley

Melton Valley served as the U. S. Atomic Energy Commission's (AEC's) Southern Regional Burial Ground for wastes for ORNL and over 50 other facilities. X-10 disposed of its radioactive wastes (liquid and solid) in Melton Valley, and also operated its experimental facilities within this watershed (U.S. DOE 2002a, 2002b). The major burial grounds are SWSA's 4, 5, and 6. Wastes were buried predominantly in unlined trenches and auger holes. Consequently, discharges from Melton Valley's waste areas have produced secondary contamination sources that include sediment, groundwater, and soil contamination. Furthermore, contaminants that are discharged from Melton Valley travel off the reservation through surface water and flow into the Clinch River (SAIC 2002, USGS 1988). As a result, the greatest impact to off-site receptors is from strontium 90 (90Sr), tritium (3H), and cesium 137 (137Cs) contaminated surface water flowing across the White Oak Dam (WOD). The three primary release areas in Melton Valley are the SWSA 4 seep areas, and SWSA 5 Seeps C and D (SAIC 2004).

The SWSA 4 seeps area is located at the X-10 site (U.S. DOE 2001e). Data collected at the ORR suggest that releases from SWSA 4 have contributed to approximately 25% of the overall 90Sr that is discharged over White Oak Dam (SAIC 2002). SWSA 4 consists of 23 acres that were used between 1951 and 1974 for industrial and radioactive waste burial (SAIC 2002). DOE's investigation revealed that two seeps produced about 70% of the overall 90Sr that was discharged from SWSA 4 (SAIC 2002; U.S. DOE 2001e). Because contaminants from these waste trenches migrated into White Oak Creek, grouting techniques were used to reduce the releases of 90Sr from these trenches; these activities were completed in October 1996. Surface water monitoring revealed that, as of 2001, these efforts had resulted in the 90Sr releases being reduced by about 33% (SAIC 2002).

In 1994, DOE conducted an assessment and remedial activities at SWSA 5 Seeps C and D. The assessment found that 90Sr was discharged from the X-10 site, and that Seeps C and D were major sources of off-site releases. Seeps C and D are located in the southern portion of WAG 5, which consists of a burial site used for radioactive waste disposal between 1951 and 1959 (SAIC 2002; U.S. DOE 2001f). Since 90Sr could potentially constitute a significant threat to off-site populations, one of DOE's main goals was to minimize these discharges from SWSA 5 into the White Oak Creek system (SAIC 2002; U.S. DOE 2001f; U.S. EPA 2002a). The objective of these remedial activities was to reduce the quantity of 90Sr in collected groundwater by at least 90% (SAIC 2002; U.S. DOE 2001f).

DOE's investigation in 1994 showed that Seep C was a major source of 90Sr releases to White Oak Creek (SAIC 2002). Of the strontium detected at White Oak Dam between 1993 and 1994, 20% to 30% was released from Seep C. In March 1994, an action memorandum was accepted, and by November 1994, a "French" drain had been installed at Seep C. The French drain collects the groundwater and directs it to a unit for treatment; this treatment unit consists of drums filled with minerals that filter the 90Sr. Once the groundwater is treated, it is released into Melton Branch. Thus, the primary goal of these remediation activities is to lower the amount of 90Sr that is released to Melton Branch, and therefore, to off-site locations (SAIC 2002; U.S. DOE 2001f). According to samples taken in 2000 and 2001, the treatment unit has prevented over 99% of the 90Sr at Seep C from entering Melton Branch (SAIC 2002). The amount of 90Sr is greater downstream from Seep C than upstream, which suggests that a portion of the 90Sr from WAG 5 bypasses the treatment unit (SAIC 2002; U.S. DOE 2001f). Currently, there are bimonthly sampling and weekly inspections of the treatment unit at Seep C (SAIC 2002).

Seep D was also a major source of 90Sr to the White Oak Creek watershed (SAIC 2002). Of the 90Sr detected at White Oak Dam between 1993 and 1994, 7% was released from Seep D. An action memorandum was passed in July 1994, and a groundwater treatment unit was installed and functioning at Seep D by November 1994. Once the groundwater has been treated, it is released to Melton Branch (SAIC 2002; U.S. DOE 2001f). Data collected in 2000 and 2001 showed that this treatment unit has prevented over 99% of the 90Sr at Seep D from entering Melton Branch (SAIC 2002). However, the amount of 90Sr is greater downstream at Seep D than upstream. This suggests that small quantities of 90Sr going into Melton Branch did not originate from the Seep D pumping location (SAIC 2002; U.S. DOE 2001f). Daily inspections are conducted at Seep D and monthly sampling is performed on the treatment unit, as well as upstream and downstream of Melton Branch (SAIC 2002).

All of the waste areas in the Melton valley are in the aquitard formations of the Conasauga Group, where permeability, and consequently, groundwater migration, is limited (USGS 1988). As is the case in much of the ORR, groundwater flow is very shallow is closely coupled with surface water. Greater than 95% of the rainwater that infiltrates the soil ends up as surface water in White Oak Creek and eventually in to the Clinch River (ORNL 1982, SAIC 2004). As a result, most of the monitoring that is performed in Melton Valley concerns surface water with emphasis on the WOD. Surface water contamination in this area is addressed in the White Oak Creek Public Health Assessment.

Off-Site Groundwater Sampling Locations Near ORNL
Figure 8. Off-Site Groundwater Sampling Locations Near ORNL

Off-Site Groundwater Monitoring Data

Seeps and Springs

Thallium was detected in one of seven samples from seeps and springs off-site near ORNL. The detected sample was taken from the SEC Well on March 4, 1996 and revealed a concentration of 2.4 ppb, which is slightly above the 2 ppb MCL for thallium. Thallium was not detected in a sample collected from the same location six months earlier. Subsequent sampling at that location has not been conducted.

Monitoring Wells

Table 2: Contaminants Detected Above Comparison Values in Monitoring Wells in the Bethel Valley and Melton Valley Watersheds

Substance

Detects / Samples

Samples Detected Above CVs

CV (ppb)

CV Source

Max Conc. (ppb)

Max Location

Max Conc. Date

Boron

8 / 9

8

100

EMEG

243

1193

5/13/1994

Iron

6 / 11

1

10950

RBC for tap water

16200

PLC Well

9/7/1995

Thallium

2 / 11

2

2

MCL

2.4

PLC Well

3/4/1996

Boron was only detected in one well – well #1193. Boron was not detected in the most recent sample from this well, which occurred on April 3, 1996. Iron was only detected above the 10950 ppb CV in one sample. This sample was taken from the PLC Well in September of 1995. A subsequent sample, six months later, from the same well yielded a concentration of 2550 ppb – well below the CV. Both samples with elevated thallium concentrations were taken from the PLC Well. No subsequent sampling has taken place for thallium at the PLC Well.

Residential Wells

There have been no contaminants detected above comparison values in residential wells near the ORNL.

ATSDR Conclusion for Bethel Valley and Melton Valley Watersheds

Groundwater in Bethel Valley and Melton Valley has short flow-paths to surface water, namely, First Creek, Raccoon Creek, the Northwest Tributary and White Oak Creek. Contaminated groundwater has not migrated to the ORR boundary. Remediation of groundwater in Bethel Valley is ongoing as it is in Melton Valley. Contaminant concentrations in general are either decreasing or are steady. There is no site-related groundwater contamination beyond the ORR boundaries from operations in Bethel or Melton Valleys. Thallium has been detected sporadically in seeps/springs and monitoring wells near ORNL. While subsequent sampling has not been conducted at the specific locations (SEC Well and PLC Well), concurrent sampling from adjacent locations have not been able to detect thallium. Iron and boron were not detected in subsequent sampling events. No contamination has been detected in residential wells near ORNL. For these reasons, ATSDR concludes that there is no public (community) exposure to groundwater contamination emanating from the ORNL.

II.F. Bear Creek and Upper East Fork Poplar Creek Watersheds

The Bear Creek watershed and the Upper East Fork Poplar Creek (UEFPC) watershed comprise a large portion of Bear Creek Valley on the ORR. Bear Creek Valley is bordered by Chestnut Ridge and Pine Ridge. The 825-acre Y-12 plant, now called the Y-12 National Security Complex, is located in Bear Creek Valley and lies predominantly in the UEFPC watershed.

Operational History

From 1944 to 1947, the Y-12 Complex was used to electromagnetically enrich uranium. In 1952, the facility was converted to enrich lithium-6 using a column-exchange process and to fabricate components for thermo-nuclear weapons using high-precision machining and other specialized processes. In 1992, after the Cold War ended, Y-12's mission was curtailed, and the plant is currently used for weapons disassembly and weapon renovation operations. The National Nuclear Security Administration currently uses the Y-12 National Security Complex as the primary storage site for highly enriched uranium. While operational levels have increased since 1992, the total operations have not approached the levels experienced before the 1990's.

Geology/Hydrogeology

The Y-12 Complex is located in the eastern end of Bear Creek Valley. It is bordered on the south by Chestnut Ridge and on the north by Bear Creek Road and Pine Ridge (ChemRisk 1999). The main Y-12 production area is about 0.6 miles wide and 3.2 miles long; the area contains roughly 240 principal buildings, of which about 18 were directly involved with processing and/or storage of uranium compounds (Patton 1963; UCC-ND 1983 as cited in ChemRisk 1999). The Y-12 Complex is located within the corporate limits of the city of Oak Ridge, about 2 miles south of downtown (ChemRisk 1999). It is less than a half mile from the Scarboro community, but Pine Ridge (which rises to about 300 feet above the valley floor) separates the Y-12 Complex from the main residential areas of Oak Ridge (TDOH 2000). Figure 9 illustrates how groundwater flows along strike in Pine Ridge and Chestnut Ridge. Indeed, the southward sloping orientation of the bed planes beneath Pine Ridge prevents groundwater from flowing north toward Scarboro.

Cross-sectional Diagram of Pine Ridge and Chestnut Ridge in the Y-12 Vicinity
Figure 9. Cross-sectional Diagram of Pine Ridge and Chestnut Ridge in the Y-12 Vicinity

Contamination at Bear Creek Valley and UEFPC Watersheds

Bear Creek Valley Watershed

In the June 2000 Record of Decision (ROD) for the Phase I Activities in Bear Creek Valley and the Oak Ridge Y-12 Plant, Bear Creek Valley was divided into three Zones for the purposes of establishing and evaluating performance standards for each zone in terms of resulting land and resource uses and residential risks following remediation (Figure 10).

Zone 1 is the area of Bear Creek Valley Watershed west of surface water monitoring location BCK 7.87. The pre-ROD situation for this zone was that there was no unacceptable risk to residential or recreational users of the land or resources in this area of the valley. The agreed upon goal for this zone was to maintain the "unrestricted use" classification. Monitoring locations, scheduling of sampling and parameters to be monitored were established throughout this zone to ensure that the goals of the ROD would be achieved (SAIC 2004).

Groundwater sampling in FY 2003 revealed that there was no uranium detected above MCLs in Zone 1. Uranium that was detected in Zone 1 was only found in GW-715 at a concentration substantially lower than results from FY 2002 sampling. These data indicate that uranium concentrations may be going down overall after peaking following a five year increase in this well from 1998. Since 1998, GW-715 has also yielded detectable concentrations of nitrate, 99Tc, gross alpha, and gross beta. At 43 feet deep, GW-715 is the shallowest well in Zone 1 and represents the close relationship with the surface water in Bear Creek. The contaminants detected in groundwater are also typically detected at surface water sampling locations along Bear Creek. In fact, losing reaches of Bear Creek contribute to groundwater recharge between Northern Tributary #9 (NT-9) and surface water sampling station #6 (SS-6) (SAIC 2004). In FY 2003, there were anomalously high exceedences of AWQCs due to high-flow conditions. These levels are expected to decrease markedly thus reducing groundwater contamination in Zone 1.

Zone 2 is the area of Bear Creek Valley between Bear Creek surface water stations BCK 7.87 and BCK 9.47. The short-term land use goals for this zone are recreational and the long-term goal is to attain unrestricted use classification. The ROD identifies the comparative criteria for groundwater in Zone 2 to be MCLs. The remedial action objective (RAO) for cleanup levels in Zone 2 is risk to potential residents to the area be below 1 x 10-5. The RAO applies as the performance criterion at BCK 9.47. BCK 9.47 is the eastern, upgradient extent of Bear Creek in Zone 2 and the integration point (IP) for contaminants in Bear Creek Valley.

In FY 2003, samples collected at the IP exceeded secondary MCLs for aluminum and manganese. Uranium was detected in the August 2003 sampling event but levels remained in the background range, so over the past 10 years the slight downward trend continues. According to these results, as of FY 2003, Zone 2 continues to meet criteria for the remediation goal of recreational land use.

The total flux of contaminants from all sources exiting the watershed in surface water and groundwater is evaluated at the IP. In the 1994 remedial investigation, mass balance equations and calculations were performed and determined that of the total amount of water passing through the IP only 3% was groundwater – measured at the Maynardville Limestone picket A.

Bear Creek Valley Zones 1, 2, and 3
Figure 10. Bear Creek Valley Zones 1, 2, and 3

Up to 99% of contaminants exiting the former waste disposal sites in Bear Creek Valley are intercepted at the IP.

Zone 3 is the area of Bear Creek Valley that lies east of the IP (BCK 9.47). The BYBY, the S-3 Site and the BCBG are located in Zone 3. The remediation goal for Zone 3 is to reduce contaminant levels to be consistent with long-term industrial land use. Groundwater cleanup criteria in Zone 3 have not been determined but contaminant concentrations are being monitored and compared to MCLs for evaluation. Uranium, nitrate, manganese, and several VOCs have exceeded MCLs in Zone 3 for many years following previously observed trends. For example, nitrate concentrations in GW-526 have been historically increasing as a result of the plume's center of mass migrating along strike, but have remained relatively stable since 1995; the closure of the S-3 Site has resulted in decreasing concentrations of uranium, nitrate, and 99Tc in GW-276; and stable to slightly decreasing concentrations of uranium, nitrate and TCE have been observed at exit pathway picket B.

As is the case throughout much of the ORR, there is a very high interconnectivity between surface and groundwater. There are gaining and losing reaches of Bear Creek along the entire Bear Creek Valley and often the contamination of surface water results in increasing contaminant concentrations in the shallow ground water and vice versa. Indeed, there are several large solution cavities beneath Bear Creek which (along certain reaches) serve as a hydraulic drain to the Maynardville Limestone (Lemiski 1994, SAIC 1996). However, completion of remedial actions in Bear Creek Valley has resulted in substantial reductions in contaminants in general. The short and long-term goals set forth in the ROD, in terms of land use and risk to residents, are being met.

UEFPC Watershed

Groundwater contamination occurs beneath the entire UEFPC watershed and continues east, across the ORR boundary, into Union Valley (Figure 13). This contaminated plume is made up of several commingling plumes from a variety of sources (Figure 11). The contaminants that were detected in one of the six monitoring wells in the Maynardville Limestone and in two springs feeding Scarboro Creek were consistent with those found in the carbon tetrachloride plume emanating from the Y-12 Complex (U.S. DOE 1997). Although the sources of most of these contaminants can not be confirmed, they are likely a result of various leaks and spills throughout the Y-12 facility. The east end of the Y-12 complex has been used primarily for maintenance and as a shipping and receiving area. Carbon tetrachloride, the primary VOC in the east end VOC (EEVOC) contaminant plume, was used extensively in the 1940s in the electromagnetic uranium separation process. The high historical on-site concentrations of carbon tetrachloride (>8000µg/L) indicate that there are probably DNAPLs present.

Groundwater in adjacent formations flows toward the Maynardville Limestone because of the formation's relatively high hydraulic conductivity and well-developed karst system.

Groundwater in the UEFPC watershed typically flows along strike from west to east in the Maynardville Formation between 100ft and 400ft below ground. Groundwater flow direction in this area is also influenced by anthropogenic structures such as pipes, drains and other underground structures which have created preferential flow paths for contaminated groundwater (SAIC 2005). However, the Maynardville Limestone is the primary pathway for contaminant migration off-site from Y-12 (Figure 12). Groundwater from adjacent formations tends to flow toward the Maynardville Limestone because of its well developed karst-system (U.S. DOE 1997). Because of the high interconnectivity with surface water, groundwater discharges at seeps and springs constitutes much of the base flow of Scarboro Creek and UEFPC. Depth to groundwater in this area is between 1 and 4 feet below ground during the winter and between 2 and 7 feet below ground in the summer (USGS 1989).

Groundwater in this area responds quickly to storms and can exhibit high flow rates with rapid dilution. A silty-clay glei horizon exists beneath EFPC and impedes downward groundwater migration (USGS 1989).

The Interim Record of Decision (ROD) for Union Valley was published in 1997 in accordance with the requirements of CERCLA (Figure 13). It presents the selected interim remedial action for Union Valley. Two interim actions were considered: Alternative 1 – no action, and Alternative 2 – institutional controls. The selected action was Alternative 2, which consisted of the following institutional controls: 1) DOE obtains license agreements with property owners notifying them of the potential contamination and requiring them to notify DOE of any changes in use of groundwater or surface water in certain areas and, 2) there will be appropriate verification by DOE of compliance with the agreements and notification of state and local agencies. This remedy is not the final remedy for Union Valley and, thus, it does not have provisions to reduce toxicity, mobility or volume of contaminants of concern. The purposes of this interim action are to 1) ensure that public health is protected while final actions are being developed and implemented and, 2) identify and, if necessary, prohibit future activities with a potential to accelerate the rate of contaminant migration from the characterization area or increase the extent of the contaminant plume (U.S. DOE 1997). In October 2000, a VOC treatment system began full-scale operation. The treatment system, which removes groundwater and treats it using filters and air strippers, is located near the ORR boundary with Union Valley.

The EEVOC plume is the only confirmed off-site contamination of groundwater at the ORR (USDOE 2004). While it is important to understand the sources and magnitudes of on-site contamination, especially as they relate to contamination off-site, the purpose of this health assessment is to determine the extent of off-site groundwater contamination using existing information and the effect, if any, this contamination will have on the public health. The Tennessee Department of Environment and Conservation (TDEC) conducts groundwater sampling at locations on the ORR and at off-site locations. In CY 2003, six residential wells and 17 exit pathway springs were sampled. In the 2003 Environmental Monitoring Report (TDEC 2003a), TDEC reports findings from three off-site springs (Bootlegger, Cattail and SS-7) and one groundwater well (GW-919). While traces of VOCs from the EEVOC plume have historically been detected in the Bootlegger spring, early in CY 2003, dilution, as a result of higher than average rainfall events, resulted in non-detects in this spring. There are no residential wells in Union Valley (Figure 14).

Conceptual Model of Groundwater Flow and Contaminant Transport at the Y-12 Complex
Figure 11. Conceptual Model of Groundwater Flow and Contaminant Transport at the Y-12 Complex

East End VOC Plume Conceptual Model
Figure 12. East End VOC Plume Conceptual Model

Estimated Extent of the EEVOC Plume in Union Valley
Figure 13. Estimated Extent of the EEVOC Plume in Union Valley

Off-Site Groundwater Monitoring Data

Seeps and Springs

Not surprisingly, the samples which contained concentrations of substances above CVs came from springs just east of the ORR boundary near the Y-12 Complex. These springs are within the known extent of the EEVOC plume (Figure 13). These results are from a one-time sampling event on March 21, 1996. Samples were collected from each sampling location and then they were split and were assigned separate sample identification numbers. Of the 15 'Samples Detected Above CVs' listed in Table 3, 13 of them are from two split samples from SCR7.14SP and SCR7.16SP. There were two other samples (from SCR7.1SP and SCR7.18SP) with elevated levels of manganese. There has been no subsequent sampling of these springs.

Table 3: Substances Detected Above CVs in Seeps or Springs Near the Y-12 Complex

Substance

Detects / Samples

Samples Detected Above CVs

CV (ppb)

CV Source

Max Conc. (ppb)

Max Location

Max Conc. Date

Benzene

1 / 8

1

5

MCL

7

SCR7.14SP

3/21/1996

Boron

16 / 16

4

100

EMEG

880

SCR7.14SP

3/21/1996

Iron

13 / 16

3

10950

RBC for Tap Water

44000

SCR7.14SP

3/21/1996

Manganese

15 / 16

6

500

RMEG

2900

SCR7.16SP

3/21/1996

Selenium

1 / 1

1

50

MCL

69

SCR7.16SP

3/21/1996

 

Residential Wells

There were no contaminants detected above CVs in off-site residential wells near the Y-12 Complex. The nearest residential well (RWS 67) is over 2 miles from the Y-12 Complex.

Monitoring Wells

Thirty chemical contaminants and twelve radionuclides were detected above comparison values in off-site monitoring wells near the Y-12 Complex. Nine chemicals (indicated by superscript 3 in Table 4) were detected above CVs only in wells in the EFPC floodplain. Wells in the EFPC floodplain include WDANE4, NOAND1, WFANE1, BRAND7, and others with similar naming convention as shown on Figure 14. As previously mentioned, groundwater does not migrate from Union Valley beneath Pine Ridge (see ATSDR's response to Public Comment #2 in Table 10); therefore, it is unlikely that any contamination in the EFPC floodplain is a direct result of groundwater contamination emanating from the Y-12 Complex. The groundwater contamination in the EFPC Floodplain results from contaminated surface water (EFPC) infiltrating into the groundwater. In 1993, ATSDR conducted a Health Consultation for this area and concluded that there is a possible health threat to people consuming groundwater in this area; however, based on available data, all residences in the area were using water from the municipal water system. Fourteen of the thirty chemicals (indicated by superscript 4 in Table 4) were either detected below CVs or not detected at all in concurrent or subsequent samples taken from wells in Union Valley. Additional comments regarding the monitoring for each substance are included in Table 4.

Of the twelve radionuclides detected above CVs (Table 5), seven were not detected above CVs, or not detected at all in subsequent samples. Five of the radionuclides were only detected above CVs in the EFPC floodplain (except radium in one sample in GW-169). Concurrent sampling of gross beta from GW-169 (the only radium exceedance) yielded a concentration 10 times lower than the CV.

Table 4: Contaminants Detected in Monitoring Wells Near the Y-12 Complex

Substance

Detects / Samples

Samples Detected Above CVs

CV (ppb)

CV Source

Max Conc. (ppb)

Max Location

Max Conc. Date2

Comments

2,4-Dinitro phenol 3

15 / 103

15

20

RMEG

50

EFPC Floodplain1

3/12/1991

All samples detected above CVs were taken from wells in the EFPC Floodplain.

2-Nitroaniline 3

15 / 113

15

3.3

RBC for Tap Water

50

EFPC Floodplain1

3/12/1991

All samples detected above CVs were taken from wells in the EFPC Floodplain.

Acetone 3

81 / 247

1

9000

RMEG

14000

WDANE4

11/19/1990

The only sample detected above the CV was taken from a well in the EFPC Floodplain.

Aluminum 4

188 / 347

33

20000

EMEG

140000

GW-169

9/28/1995

Aluminum has not been detected in subsequent samples in GW-169. Several wells in the EFPC Floodplain yielded aluminum concentrations above the CV.

Arochlor-1260 3

4 / 82

4

0.033

RBC for Tap Water

1

EFPC Floodplain1

3/12/1991

All samples detected above CVs were taken from wells in the EFPC Floodplain.

Arsenic 4

39 / 310

7

10

MCL

83

GW-169

9/28/1995

Arsenic has not been detected in subsequent samples.

Barium 4

350 / 354

1

2000

MCL

3150

NOAND1

6/14/1991

Another sample on the same day (6/14/1991) from the same well yielded a concentration of only 412 ppb.

Benzene 3

15 / 237

3

5

MCL

7

NOAND1

11/08/1990

All samples detected above CVs were taken from wells in the EFPC Floodplain.

Beryllium

36 / 196

20

4

MCL

28.1

NOAND5

6/18/1991

Elevated levels of beryllium have only been found in GW-169 in Union Valley; however, several wells in the EFPC floodplain have shown concentrations above the CV.

Boron

183 / 184

75

100

EMEG

2900

GW-232

3/12/1991

All samples detected above the CV have come from wells located within the known extent of the EEVOC.

Carbon tetrachloride

45 / 244

26

7

RMEG

200

GW-170

11/17/1994

All samples detected above the CV have come from one well, GW-170, located within the known extent of the EEVOC.

Chloroform 4

52 / 249

1

100

EMEG

134

GW-170

2/2/1994

Samples collected on the same day from the same well were below the CV. Subsequent samples were also below the CV.

Chromium 4

88 / 354

13

100

LTHA

720

GW-169

4/27/1992

Subsequent samples were well below the CV for chromium.

Cobalt 4

74 / 354

3

100

EMEG

144

WFANE1

11/19/1990

In two of the three wells where samples exceeded the CV, subsequent samples were below the CV.

Copper 4

139 / 354

10

100

EMEG

6320

WFANE1

11/19/1990

Most samples detected above CVs were taken from wells in the EFPC Floodplain.

Dibenzo(a,h) anthracene 3

11 / 113

11

0.009

RBC for Tap Water

11

BRAND7

11/2/1990

All samples detected above CVs were taken from wells in the EFPC Floodplain.

Flouride 4

124 / 198

1

4000

MCL

4900

GW-169

5/18/2000

Only one sample exceeded the CV. Concurrent and subsequent samples from adjacent wells were below the CV.

Ideno(1,2,3-cd)pyrene 3

15 / 113

15

0.092

RBC for Tap Water

12

WAANE12

3/14/1991

All samples detected above CVs were taken from wells in the EFPC Floodplain.

Iron 4

300 / 354

78

10950

RBC for Tap Water

200000

GW-169

9/28/1995

The only well in Union Valley with elevated iron levels was GW-169. All other samples exceeding the CV were in the EFPC Floodplain.

Lead

93 / 296

38

15

MCLG

1200

GW-169

4/27/1992

Samples from both Union Valley and the EFPC floodplain exceeded the CV.

Manganese

309 / 354

193

500

RMEG

27600

NOAND3

6/18/1991

Samples from both Union Valley and the EFPC floodplain exceeded the CV.

Mercury 3

41 / 119

22

2

MCL

280

WFANE1

11/19/1990

All samples detected above CVs were taken from wells in the EFPC Floodplain.

Methylene chloride 3

130 / 250

4

600

EMEG

4200

BRAND7

11/2/1990

All samples detected above CVs were taken from wells in the EFPC Floodplain.

Nickel 4

100 / 358

16

100

LTHA

657

WFANE1

11/19/1990

Samples from both Union Valley and the EFPC floodplain exceeded the CV.

Selenium 4

37 / 259

4

50

EMEG

72

GW-230

9/20/1995

All samples detected above the CV have come from wells located within the known extent of the EEVOC.

Tetrachloroethylene 4

77 / 259

23

5

MCL

11

GW-170

11/17/1994

All samples detected above the CV have come from wells located within the known extent of the EEVOC.

Thallium

38 / 88

38

2

MCL

7

GW-170

2/2/1994

All but one sample detected above CVs were taken from wells in the EFPC Floodplain. Only one sample was detected above the CV in GW-170 in 1994. Thallium was never detected in adjacent wells. Subsequent sampling for thallium in GW-170 has not been conducted.

Trichloroethylene 4

67 / 261

3

5

MCL

6

GW-169

3/1/1991

All samples detected above the CV have come from wells located within the known extent of the EEVOC.

Vanadium 4

80 / 366

37

30

EMEG

300

GW-169

9/28/1995

The only well in Union Valley with elevated vanadium levels was GW-169. All other samples exceeding the CV were in the EFPC Floodplain.

Zinc

272 / 354

7

3000

EMEG

12000

GW-230

6/18/1996

All samples detected above the CV have come from wells located within the known extent of the EEVOC.

**PLEASE SEE APPENDIX A FOR DEFINITIONS OF TERMS USED IN THIS TABLE**
1Several locations reported the same maximum concentration. All locations were in the EFPC Floodplain.
2Where more than one sampling location yielded the same maximum concentration, the most recent sample date is reported.
3Contaminants detected above CVs only in the EFPC Floodplain.
4In all subsequent samples from wells in Union Valley, contaminants were either detected below CVs or not detected at all.

Table 5: Radionuclides Detected Above CVs in Monitoring Wells Near the Y-12 Complex

Radionuclide

Detects / Samples

Samples Detected Above CVs

CV (pCi/L)1

Max Conc. (pCi/L)

Max Location

Max Date

Comments

Alpha radiation

122 / 177

9

15

81.3

GW-232

11/7/2001

Subsequent samples in all wells have been below detection limit.

Am-241

70 / 72

38

7.25

110

NOAND1

3/8/1991

All samples above the CV were from the EFPC Floodplain.

Beta radiation

164 / 189

5

50

2560

GW-230

8/7/2002

Subsequent samples in all wells have been either below detection limit or below the CV.

Gross beta

41 / 41

1

50

57.5

GW-169

9/28/1995

Concurrent sampling from this well yielded 4.9 pCi/L.

Iodine-129

27 / 27

2

14

21.6

GW-170

3/22/1995

Subsequent samples in all wells have been below the CV.

Neptunium-237

52 / 53

29

13.8

239

WEANE3

3/8/1991

All samples above the CV were from the EFPC Floodplain.

Radium

109 / 109

14

5

26.3

NOAND2

11/8/1990

All samples above the CV were from the EFPC Floodplain except one from GW-169. Subsequent samples from GW-169 were below the CV.

Radium-228

5 / 8

1

2

2.11

GW-230

12/13/1995

Subsequent samples have been either below detection limit or below the CV.

Thorium-234

13 / 13

3

435

655

GW-172

9/26/1994

Subsequent sampling has not occurred.

Uranium-234

111 / 113

8

30

109

WFANE1

11/19/1990

All samples above the CV were from the EFPC Floodplain.

Uranium-235

87 / 114

2

30

54.9

GW-230

9/28/1994

Subsequent samples have been either below detection limit or below the CV.

Uranium-238

119/ 124

7

30

115

WFANE1

11/19/1990

All samples above the CV were from the EFPC Floodplain.

1Based on Federal Guidance 13, two liters water/day

Off-Site Groundwater Sampling Locations Near the Y-12 Complex
Figure 14. Off-Site Groundwater Sampling Locations Near the Y-12 Complex

ATSDR's Conclusion for Bear Creek Valley and UEFPC Watersheds

The most successful remediation efforts in FY 2002 and FY 2003 occurred in Bear Creek Valley. The uranium flux throughout the watershed decreased markedly. The EEVOC plume in the UEFPC Watershed has been subject to aggressive pump and treat remedial efforts since August of 1999 when an action memorandum was issued to begin installation and testing of a groundwater extraction well. Actual pumping of the plume commenced in June of 2000. Administrative controls set forth in the 1997 Interim ROD for Union Valley are deemed protective of public health. Since the EEVOC groundwater plume extends off-site into Union Valley, ATSDR scientists will evaluate possible exposure scenarios for this area in the Evaluation of Environmental Contamination and Potential Exposure Pathways section of this document.

II.G. Land Use and Natural Resources

When the ORR was acquired in 1942, the government reserved a section of the reservation (about 14,000 acres out of the total of approximately 58,575) for housing, businesses, and support services (ChemRisk 1993d; ORNL 2002). In 1959, that section of the ORR was turned into the independently governed city of Oak Ridge. This self-governing area has parks, homes, stores, schools, offices, and industrial areas (ChemRisk 1993d).

The majority of residences in Oak Ridge are located along the northern and eastern borders of the ORR (Bechtel Jacobs Company LLC et al. 1999). However, since the 1950s, the urban population of Oak Ridge has grown toward the west. As a result of this expansion, the property lines of many homes in the city's western section border the ORR property (Faust 1993 as cited in ChemRisk 1993d). Apart from these urban sections, the areas close to the ORR continue to be mainly rural, as they have historically been (Bechtel Jacobs Company LLC et al. 1999; ChemRisk 1993d). The closest homes to X-10 are located near Jones Island, about 2.5 to 3.0 miles southwest of the main facility (ChemRisk 1993d).

In 2002, the ORR measured 34,235 acres, which includes the three main DOE facilities: Y-12, X-10, and K-25 (ORNL 2002). The majority of the ORR is situated within the city limits of Oak Ridge. These DOE facilities constitute approximately 30% of the reservation; the remaining 70% of the reservation was turned into the National Environmental Research Park in 1980. This park was created so that protected land could be used for environmental education and research, and to show that the development of energy technology could be compatible with a quality environment (EUWG 1998). A large amount of land at the ORR that was formerly cleared for farmland has grown into full forests over the past several decades. Sections of this land contain areas called "deep forest" that include flora and fauna considered ecologically significant, and portions of the reservation are regarded as biologically rich (SAIC 2002).

Historically, forestry and agriculture (beef and dairy cattle) have constituted the primary uses of land in the area around the reservation. However, these uses of land are both declining. For several years, milk produced in the area was bottled for local distribution, whereas beef cattle from the area were sold, slaughtered, and nationally distributed. In addition, tobacco, soybeans, corn, and wheat were the primary crops grown in the area. Also, small game and waterfowl were hunted on a regular basis in the ORR area, but deer were hunted during specific time periods (ChemRisk 1993d). Waterfowl and small game hunting regularly occurs within the ORR area, while deer hunting occurs annually on the ORR (ChemRisk 1993d). During the annual deer hunts, radiological monitoring is conducted on all deer prior to their release to the hunters. Monitoring is conducted to ensure that none of the animals contain quantities of radionuclides that could cause "significant internal exposure" to the consumer (Teasley 1995).

The southern and western boundaries of the ORR are formed by the Clinch River; Poplar Creek and East Fork Poplar Creek drain the ORR to the north and west (Jacobs EM Team 1997b). White Oak Creek, which travels south along the eastern border of the X-10 site, flows into White Oak Lake, over White Oak Dam, and into the White Oak Creek Embayment before meeting the Clinch River at CRM 20.8 (ChemRisk 1993b, 1999a; TDOH 2000; U.S. DOE 2002a). Ultimately, every surface water system on the reservation drains into the Clinch River (ChemRisk 19993b). The Lower Watts Bar Reservoir is situated downstream of the ORR, extending from the confluence of the Clinch and Tennessee Rivers to the Watts Bar Dam (U.S. DOE 1995a as cited in ATSDR 1996). As a result, the Clinch River and the Lower Watts Bar Reservoir have received contaminants associated with X-10 operations (Jacobs EM Team 1997b; U.S. DOE 1995a; U.S. DOE 2001a). Please see Figure 1 for these relative water systems.

The majority of land around the Clinch River and the Lower Watts Bar Reservoir is undeveloped and wooded. Other than activities at the ORR, there is minimal industrial development in these surrounding areas, and there is a fair amount of residential growth. The public has access to the Clinch River and to the Lower Watts Bar Reservoir, which it uses for recreational purposes such as boating, swimming, fishing, water skiing, and shoreline activities (U.S. DOE 1996d, 2001b, 2003b).

None of the current landowners in Union Valley extract groundwater for residential use. The nearest residential well is over 2 miles from the EEVOC groundwater plume.

Land use in Union Valley, just east of the Y-12 complex, is zoned by the City of Oak Ridge primarily as "Forestry, Agriculture, Industry, and Research District". The land over the presumed extent of the off-site contaminant plume is zoned as "Industrial District 2". None of the current landowners in Union Valley extract groundwater for residential use. Extracted groundwater from dewatering of the quarry on lot Excess (613) by Rogers Group, Inc. is discharged to surface water. No contamination has been found in the quarry water. The closest "One-Family Residential District" is 2.25 miles east of the known extent of the EEVOC plume (DOE 1997).

II.H. Demographics

Demographic data provide information on the size and characteristics of a given population. ATSDR examined demographic data to determine the number of people living in the vicinity of the ORR and to determine the presence of sensitive populations, such as children (age 6 years and younger), women of childbearing age (age 15 to 44 years), and the elderly (age 65 years and older). According to the 2000 U.S. Census, 153 children, 403 women of childbearing age, and 423 elderly persons live within a quarter mile from the ORR; and 778 children, 1,935 women of childbearing age, and 1,681 elderly persons live within a mile of the ORR (see Figure 15).

Demographics also provide details on population mobility and residential history in a particular area. This information helps ATSDR evaluate how long residents might have been exposed to environmental contaminants. The number of people living in the counties surrounding the ORR from 1940 to 2000, are listed in Table 6.

Table 6: Population of Surrounding Counties from 1940 to 2000

County

1940

1950

1960

1970

1980

1990

2000

Anderson County

26,504

59,407

60,032

60,300

67,346

68,250

71,330

Blount County

41,116

54,691

57,525

63,744

77,770

85,969

105,823

Knox County

178,468

223,007

250,523

276,293

319,694

335,749

382,032

Loudon County

19,838

23,182

23,757

24,266

28,553

31,255

39,086

Meigs County

6,393

6,080

5,160

5,219

7,431

8,033

11,086

Morgan County

15,242

15,727

14,304

13,619

16,604

17,300

19,757

Rhea County

16,353

16,041

15,863

17,202

24,235

24,344

28,400

Roane County

27,795

31,665

39,133

38,881

48,425

47,227

51,910

Sources: U.S. Bureau of the Census 1900–1990, 2000

Figure 15 shows the demographics within a 5 mile radius of the ORR boundary. As previously mentioned, most of the residents of the Oak Ridge and surrounding communities, live along the northern and northeastern borders of the site. Figure 16 shows the population distribution within a one and 3 mile radius of the Y-12 complex – the only area where groundwater contamination has migrated off-site. Surrounding the area of known off-site EEVOC plume, along Union Valley Road to the east-northeast of the Y-12 complex, there are no residences. For more information concerning the demographics of the surrounding towns please refer to the following Public Health Assessments: Former K-25 and S-50 Sites Air Releases, Y-12 Uranium Releases, and White Oak Creek Radionuclide Releases.

Demographics Within 5 Miles of ORR
Figure 15. Demographics Within 5 Miles of ORR

Demographics within 1 and 3 miles of the Y-12 Complex
Figure 16. Demographics within 1 and 3 miles of the Y-12 Complex



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