PUBLIC HEALTH ASSESSMENT

NORTON AIR FORCE BASE
NORTON AIR FORCE BASE, SAN BERNARDINO, CALIFORNIA

SUMMARY

Norton Air Force Base (AFB), an inactive military base, encompasses over 2,000 acres of land in San Bernardino County, California. Norton AFB is situated between the San Gabriel Mountains on the northwest and the San Bernardino mountains on the northeast, with the Santa Ana River on its southern boundary. The installation, which opened in 1942, was used as an Army and Army Air Corps supply facility and housed numerous tenant organizations. The base closed in March 1994.

The facility was placed on the U.S. Environmental Protection Agency (EPA) National Priorities List (NPL) in 1987 because of contamination detected in the base groundwater and soils. Contaminants of potential concern at this site include trichloroethylene (TCE), tetrachloroethylene (PCE), 1,2-dichloroethylene (DCE), polychlorinated biphenyls (PCBs), various radionuclides, and metals, including arsenic.

Community members have expressed concern about potential health effects associated with site contaminants in groundwater and soils. In response, the Agency for Toxic Substances and Disease Registry (ATSDR) conducted an initial site visit in May 1995. At that time, no immediate public health hazards were identified; however, additional data were needed to fully evaluate groundwater and soil contamination. ATSDR revisited Norton AFB in May 1997 to confirm that no immediate hazards to public health exist and further evaluate community health concerns.

ATSDR reviewed and evaluated groundwater data. TCE was detected in groundwater beneath Norton AFB and the nearby vicinity. Routine monitoring of the base drinking water wells, private wells in the area, and the nearby public water wells indicate that the water meets EPA's drinking water standards. In addition, Norton has active groundwater cleanup systems in place to treat the contaminated water. To ensure continued delivery of safe drinking water off site, Norton AFB has agreed to supply off-site drinking water should it become necessary in the future. For these reasons, ATSDR concludes that TCE groundwater contamination from Norton AFB does not pose a threat to public health.

Seemingly elevated radionuclide readings in several public supply wells and documentation of radionuclide usage and storage at Norton AFB led to a comprehensive radionuclide investigation of Norton AFB and the surrounding area. Groundwater and soil investigations were conducted at Norton AFB to identify radionuclides of potential concern and quantify background concentrations on base. No radionuclide constituents were detected in soils at levels that pose a public health hazard. All radionuclides detected in the drinking water wells on base and Riverside drinking water wells were determined to be naturally occurring. Radionuclides in base drinking water wells were not detected at levels above EPA's drinking water standard (except for one sample). Although the city of Riverside drinking water wells located downgradient from Norton AFB have naturally occurring radionuclide levels above the MCL, affected groundwater is blended with water from non-impacted wells to reduce contaminant levels and meet drinking water standards. For these reasons, ATSDR concludes that radiological contaminants detected in soils, Norton AFB drinking water wells, and Riverside drinking water wells downgradient from Norton AFB do not pose an apparent health hazard.

ATSDR also reviewed on-site soil and soil gas data. Twenty-two installation restoration program (IRP) sites and 73 areas of concern (AOCs) were targeted as suspect areas for chemical use and/or waste disposal activities on base. Contaminants in on-site soils were either detected at levels that do not pose a public health hazard; were inaccessible because of their depth below the ground's surface; or located where exposure was infrequent or unlikely. Based on the available data, ATSDR concludes that no public health hazards are associated with exposure to soil or soil gas contamination on base (see Table 1, Public Health Evaluation column).

Based on review of available information on groundwater and localized soil contamination, ATSDR concludes that Norton AFB should be assigned to the No Apparent Public Health Hazard category.

BACKGROUND

Site Description and Operational History

Norton Air Force Base (AFB) is a closed military base located in San Bernardino County in southern California, southeast of the city of San Bernardino in the San Bernardino Valley. Norton AFB is approximately 55 miles east of Los Angeles and 60 miles west of Palm Springs (Figure 1). It is situated between the San Gabriel Mountains on the northwest and the San Bernardino Mountains on the northeast, with the Santa Ana River forming its southern boundary. The cities of San Bernardino, Highland, Redlands, Loma Linda, Colton, and Riverside surround the approximately 2,000-acre base.

Norton AFB was established in 1942 as the San Bernardino Air Depot, an Army and Army Air Corps supply facility. The facility's primary function was the repair and maintenance of aircraft. After World War II, operations expanded to provide maintenance, storage, and logistics support for various missile programs. In 1966, Norton AFB became the base for the 63rd Military Airlift Wing, providing airlift and food services to worldwide air and ground combat units. Headquarters for the Aerospace Audiovisual Services (AAVS) was also established at Norton AFB in 1966 to provide audiovisual services to the Air Force and all Department of Defense agencies. Norton AFB also has housed numerous tenant organizations, including Air Force Inspection and Safety Center Headquarters; Air Force Audit Agency Headquarters; Military Airlift Command Non-Commissioned Officer Academy-West; and Headquarters and Ballistic Missile Organization (ESI, 1982). The base was selected for closure by the Base Realignment and Closure Commission in 1988 and closed on March 31, 1994 (Earth Tech, 1995b).

Past waste disposal activities at Norton AFB have included burial of drums and other unspecified materials at several sites in the golf course area on base; disposal of waste oil, solvent, paint residue, and similar substances into unlined pits, ponds, or drying beds; disposal of wastes from the Industrial Waste Treatment Plant (IWTP); discharge of waste aviation fuel, oil lubricant, and miscellaneous combustible materials during fire training exercises; storage of drums with possible leaks on unprotected surfaces; leakage from underground storage tanks (USTs) containing waste oil, lubricant, and solvent; spills of aviation fuel, oil solvent, polychlorinated biphenyls (PCBs), acidic plating solution, and similar substances onto unprotected surfaces; and burial of small quantities of low-level radioactive wastes. In addition, trichloroethylene (TCE) was used as a solvent in various operations at Norton AFB, which led to soil and groundwater contamination (ESI, 1982).

Remedial and Regulatory History

In June 1982, the Air Force initiated an installation restoration program (IRP) at Norton AFB to investigate environmental contamination from past waste handling practices. From 1982 to 1988, the Air Force reviewed records and conducted site investigations of suspected waste disposal sites. (For more information on the extent of these investigations, see Table 1.) Environmental sampling and analysis revealed various levels of soil and groundwater contamination. IRP work identified 22 sites as potential sources of contamination or of potential public health concern due to past waste disposal practices (Ecology & Environment, Inc., 1988; see Figure 2).

EPA placed Norton AFB on the National Priorities List (NPL) on July 22, 1987, due to hazardous substance contamination identified in the IRP investigation. Principal site contaminants are TCE, 1,2-dichloroethylene (DCE), tetrachloroethylene (PCE), PCBs, various radionuclides, and inorganics, including arsenic. A plume of TCE contaminated groundwater is present beneath portions of the base and southwest of Norton AFB (USAF, 1993a).

The Air Force conducted a series of additional records searches to evaluate chemical uses at Norton AFB from 1991 to 1993 and to determine if areas of the base, besides the 22 IRP sites, had the potential for environmental contamination. Record searches and further investigations identified suspected chemical use or waste disposal activities at 73 areas of concern (AOC). Soil investigations, cleanup, and site restoration have been completed at most of these targeted areas; the remaining sites should be cleaned up and restored by 2000 (see Table 1).

In 1992, Phase I of the off-base groundwater monitoring program began with the installation and monitoring of 28 off-base monitoring wells between the southwestern boundary of Norton AFB and the drinking water wells located downgradient of the base. Wells were sampled monthly for 6 months. Thereafter, sampling frequency was reduced to a quarterly basis except for wells with an average concentration of TCE or 1,2-DCE greater than 1.25 parts per billion (ppb); those wells continued to be sampled monthly (Earth Tech, 1994a).

In 1993, Phase II of the off-base groundwater monitoring program began with the installation of eight more monitoring wells to determine the lateral and vertical extent of the TCE plume. The Phase II wells were installed at multiple depths. These wells are deeper and are located further downstream from Norton AFB than the Phase I wells. All wells were sampled quarterly, and the wells with TCE or 1,2-DCE concentrations of 1.25 ppb or greater were sampled monthly (Earth Tech, 1994a).

Multiple sites on Norton AFB were also targeted for radionuclide investigations. These sites were identified based on verbal or written reports of contamination, documented past work activities, or survey results indicating potentially elevated radionuclide levels. In 1994, a basewide radionuclide investigation of groundwater and soil quality at these target areas was initiated. Soil sampling was conducted over a 4-month period (April through July 1995), and groundwater from 48 groundwater monitoring and domestic drinking water production wells located on or in the vicinity of Norton AFB was sampled three times in a 1-year period (October/November 1994, April/May/June 1995, and October/November 1995) (IT, 1996a) (see Site Visits and Community Concerns section below for ATSDR radionuclide evaluations).

A field study was conducted in 1994 to address the potential public use of water supply wells in an area southwest of Norton AFB. These investigations verified the location and status of each private water supply well identified in the records search (Earth Tech, 1997b).

Groundwater remediation is ongoing. One pump and treat system was installed on base in the most contaminated part of the TCE plume area in June 1992; the capacity of the system was doubled in 1995. A second pump and treat system was installed at the southwest base boundary in March 1995. These systems pump contaminated groundwater out of the aquifer, treat it, and then reinject it back into the groundwater aquifer. In addition, a soil vapor extraction (SVE) unit and air stripping towers became operational in October 1995 to mitigate TCE contamination leaching from the soil to the groundwater. SVE technologies treat contaminated soil in situ (in place). By 1996, the Norton AFB groundwater remedy was certified operational by the state of California and EPA (ATSDR, 1997a).

In 1997, the abandoned well plugging and closure program to identify and permanently remove from service any existing small and large diameter wells in the southwest corner of the base was completed (Earth Tech, 1997e). These wells were closed to alleviate the possible path for migration of contaminants between the different aquifers. Many abandoned wells were located on the property south of Mill Street, east of Tippecanoe Avenue, and north of Central Avenue (at the end of Norton AFB runway 24), which was acquired by the Air Force about 1982 (Earth Tech, 1997c; Figure 3). This tract of land was formerly a housing development (approximately 70 lots) with some light industry; the land was subdivided in late 1948. No monitoring data were available for these abandoned wells to evaluate potential past public health exposures. Groundwater data from nearby monitoring wells were, however, available for review. These data were used below to analyze potential exposures.

Site Visits and Community Concerns

ATSDR conducted an initial site visit on May 25, 1995, to identify potential health hazards associated with the site. During the site visit, ATSDR met with representatives from the Air Force and EPA. ATSDR held public availability sessions to gather information about possible community health concerns.

Following ATSDR's initial site visit, seemingly elevated levels of radioactive constituents were detected in groundwater samples on the Norton AFB property, particularly in monitoring well 158 (MW-158). In November 1995, ATSDR obtained a sample of water from MW-158 which was evaluated by an ATSDR health physicist, as was other groundwater sampling data from the well. Uranium and its associated decay products were found in the water sample submitted. Although the amounts of uranium in the sample were higher than normally found in groundwater, the detected radiation activities were at the expected activity ratios indicating that the detected uranium was of natural origin. These findings were presented to the Norton AFB Restoration Advisory Board (RAB) in March 1996 (ATSDR, 1996; Georgia Institute of Technology, 1996).

ATSDR revisited Norton AFB during May 6 and 7, 1997, to confirm that no immediate public health hazards existed and further evaluate community health concerns. ATSDR met with representatives from the Air Force and California's Department of Health Services. ATSDR representatives also met and discussed health concerns related to Norton AFB with interested community members during a public availability session at the San Bernardino Public Library. During this public session, ATSDR also explained the nature of the public health assessment process to interested community members, including regulators, water purveyors, community members involved in RAB activities, and community members who expressed health concerns related to Norton AFB.

During ATSDR's site visits, community members expressed various concerns regarding the site (ATSDR, 1995c). These concerns are grouped into four areas of general concern. The concerns listed below were addressed in this public health assessment:

1. Possible health effects caused by exposure to TCE in groundwater.



2. Possible health effects caused by exposure to radioactivity in groundwater.



3. Potential health effects from exposure to contaminated soil (especially near the day care facility), including radiological materials.



4. Potential associations between their medical and physical ailments (e.g., lupus, cancer, migraines) and possible multiple chemical exposures from Norton AFB. Further, potential associations between a rumored dump in the vicinity of Norton AFB, problems with their homes (e.g., phosphorous red material around the house and visible gas vapors), and their self-reported medical problems.

Demographics and Land Use

To identify the presence of sensitive subpopulations, such as young children or the elderly, in the vicinity of an NPL site, ATSDR examines the demographics of the nearby communities (see Figure 4). This information also provides detail on residential history in a particular area that helps ATSDR assess time frames of potential human exposure to contaminants. The demographic and housing data for Norton AFB and the surrounding areas, particularly the area southwest of the site where groundwater contamination has migrated, are presented in this section. Data are based on census data from 1980 and 1990, and are also summarized in Tables 2 and 3, respectively.

Norton AFB and Site Area Population and Housing Data

The 1990 U.S. Census indicated the population on Norton AFB to be approximately 650 people, 70 percent of which were male; in 1984, the population on base was estimated to be slightly less than 8,000 people (Snedeker, 1986). Although the population on base declined from 1980 to 1990 because of the closing of the base, the areas surrounding Norton AFB experienced a rapid population growth of over 35 percent (see Table 2). Substantial increases in the black, Hispanic, and Asian and Pacific Islander populations, particularly for families in their childbearing years, occurred during that time frame while the white population decreased by more than 10 percent.

In 1990, the median rent for a home on base was about $650 per month. Data indicate that there was a substantial increase in the percentage of renter-occupied households on base from 1980 to 1990. This increase coincides with the movement of young families to the area. The total renter-occupied households on base in 1990 was more than 98 percent (see Table 3). In 1990, over 80 percent of the residents on Norton AFB and in the surrounding areas lived in their current home for less than 10 years. This percentage suggests that the residents of Norton AFB and the general surrounding area are relatively transient in nature, with few long-term residents.

Southwest Area Population and Housing Data

The area southwest of Norton AFB experienced a population loss of over 15 percent from 1980 to 1990. This area is more racially and ethnically mixed than the site area as a whole, with high percentages of Hispanics and blacks and a rapidly-declining white population. The number of children under the age of 10 (over 22 percent) and the number of persons per household (3.65) also increased between 1980 and 1990 (see Table 2).

The number of owner-occupied households in the southwest area decreased by about 9 percent between 1980 to 1990. In 1990, the median value for a house in the southwest area near the base was about $75,000 and the median rental fee for a home was about $340 per month (For the median values adjusted to the consumer price index, see Table 3.) Over 73 percent of the householders in the southwest area had lived in their current unit for less than 10 years in 1990. Similar to the findings above, the people residing in the area southwest of Norton AFB are also relatively transient in nature, with few long-term residents.

Land Use in Norton AFB Area

The land surrounding Norton AFB is zoned for residential, commercial, industrial, and agricultural uses. The residential areas primarily consist of single-family detached dwellings in subdivisions and schools, while commercial areas are made up mostly of governmental, business, or professional buildings; medical offices or clinics; hotels; and supermarkets. Industrial areas include storage yards, industrial plants, and motor and rail terminals. Norton AFB is bordered by the Santa Ana River to the southeast. An area of agriculture is located on the south side of the Santa Ana River approximately 0.5 mile from Norton AFB; produce grown in this area includes oranges, strawberries, olives, and soybeans (USAF, 1993a).

Quality Assurance and Quality Control

In preparing this public health assessment, ATSDR relied on the information provided in the referenced documents. The environmental data presented in this public health assessment are from the remedial site investigations for the IRP and AOC sites; radionuclide investigations; quarterly groundwater monitoring data; and drinking water well data from city of San Bernardino Municipal Water Department, State Department of Health Services, Norton AFB, and the city of Riverside. The limits of these data have been identified in the associated reports.

COMMUNITY HEALTH CONCERNS AND POTENTIAL EXPOSURE PATHWAYS

Introduction

The following discussion evaluates community concerns about potential human exposure via contaminated groundwater and soils. This public health assessment will state each concern, present a brief summary of ATSDR's conclusions, and describe in more detail any identified exposure pathways and the basis for ATSDR conclusions. ATSDR's conclusions regarding the past, present, and potential future exposures to various environmental media on and in the vicinity of Norton AFB are based upon evaluation of data gathered from remedial site investigations, radionuclide speciation studies, groundwater monitoring data, Riverside and Norton drinking water wells data, and the observations compiled during site visits.

ATSDR reviewed the available data and information compiled on all recognized or designated IRP sites and AOC sites (see Table 1) at Norton AFB to ensure a thorough evaluation of all potential or completed pathways of human exposure to contaminants.

ATSDR addressed community health concerns by conducting a thorough investigation of the environmental data to determine if potential or completed pathways of human exposure to contaminants existed in the past or if they exist now or potentially in the future. The results of that pathway investigation are summarized in Table 5. The exposure evaluation process is explained in more detail in Figure 5. Tables and figures are provided at the end of this document.

Appendix A provides a glossary of environmental and health terms presented in the discussion. In evaluating environmental contamination, ATSDR uses several media-specific comparison values to select environmental contaminants for further evaluation, including Environmental Media Evaluation Guides (EMEGs), Reference Dose Media Evaluation Guides (RMEGs), Cancer Risk Evaluation Guides (CREGs), and EPA's Maximum Contaminant Levels (MCLs). Appendix B provides a description of the comparison values used in this evaluation to assess environmental contamination. Appendix C contains the estimates of human exposure dose and determination of health effects based on toxicity for TCE in groundwater.

1. Concern: TCE in groundwater

Could exposure to TCE-contaminated groundwater result in adverse human health effects for residents of neighboring communities or for former employees of Norton AFB?

Conclusions

After detailed review of the available data, ATSDR has drawn several conclusions regarding past, present, and possible future exposures to contaminated groundwater at Norton AFB:

Present and Potential Future Exposures

• Drinking water supplied from the base drinking water wells BP-3 and BP-5 on Norton AFB is safe to drink. Only one of the two base drinking water wells lies in the TCE plume area (base well BP-5) (Figure 6). This well is 1,100 feet deep and, since testing of the well began in September 1980, TCE has been detected in only one sample (6.2 ppb) (ESI, 1982; Weston Consultants, 1985; Martin Marietta Energy Systems, Inc., 1992). Further, this detection only slightly exceeds the MCL of 5 ppb. This slightly elevated concentration is the only detection of TCE above the MCL in either well.



• No present or future health hazards exist because municipal drinking water must meet federal and state drinking water standards. Periodic monitoring of base wells will ensure that drinking water from these wells remains safe to drink. If contamination is found at levels above drinking water standards, the well water will either be blended with unaffected well water to safe levels, or treated to reduce contaminant levels, or the well will be shut down (Tom Dodson & Associates, 1998).



• Riverside drinking water is and will remain safe to drink. Riverside drinking water is supplied by groundwater production wells located downgradient of the Norton AFB contamination plume. These wells are slightly affected by the contamination; however, the water is blended with uncontaminated water from wells upgradient of Norton AFB to reduce contaminant levels. Drinking water is regularly tested and meets drinking water standards (City of Riverside Public Utilities Department, 1992, 1995).



• No present or potential future public health hazards exist from the existing private groundwater wells located downgradient of the Norton AFB groundwater plume. These wells have been tested and no contaminants were detected (Earth Tech, 1997b).

Past Exposures

• Ingestion of drinking water supplied from base drinking water wells posed no past health hazards. No contamination at levels associated with health hazards has been detected in groundwater sampled from base drinking water wells since 1980, when sampling began (ESI, 1982; Weston Consultants, 1985; Martin Marietta Energy Systems, Inc., 1992).



• Riverside drinking water also posed no past public health hazard. Data from 1979 indicate that TCE levels were below drinking water standards for most of the Riverside drinking water wells (see Table 7). According to analytical results obtained by the city of Riverside from 1989 to 1991, three wells (Raub 5, Norman Road⁽¹⁾, and Warren 2) consistently contained TCE concentrations between 1 ppb and 17 ppb; however, water was blended to meet drinking water standards prior to human consumption (City of Riverside Public Utilities Department, 1992, 1995).



• No public health hazards are associated with the past consumption of water from the South San Bernardino County Water District wells (now abandoned) in the former housing area property now owned by the Air Force. ATSDR estimated exposure doses and potential noncancer and cancer effects from ingesting water from these wells and levels were below those associated with health effects.

Discussion

Norton AFB Hydrogeology: The former Norton AFB is located within the 110-square mile Bunker Hill groundwater basin, which is subdivided into three water-bearing zones or aquifers (upper, middle, and lower) (ESI, 1982; see Figure 7). Locally overlying the three zones is a perched zone of water; the perched zone is located 25 to 28 feet below ground surface (bgs) and does not contain enough water to be a viable drinking water supply. Potable water on Norton AFB can be found beginning in the upper aquifer at about 57 to 150 feet bgs.

Norton AFB and the nearby city of Riverside draw drinking water primarily from the middle and lower water-bearing zones of Bunker Hill basin, 250 to 1,000 feet bgs. The Norton AFB TCE plume is located closer to the ground surface, primarily in the upper aquifer; however, some contamination has reached the middle aquifer at a maximum depth of approximately 400 feet (Earth Tech, 1994a; 1997b). Groundwater generally flows from northeast to southwest. The Norton AFB TCE plume is migrating southwesterly toward the Riverside community (see Figures 8 and 9).

Two pump and treat systems installed in the plume area are slowing the migration and reducing the concentration of contaminants in the aquifer. These systems pump contaminated groundwater out of the aquifer through extraction wells, treat the water via air stripping, and then reinject the clean, treated water back into the groundwater aquifer. (See Figure 8 for the location of the pump and treat wells.) The soil vapor extraction system has removed significant amounts of VOCs from the soils above the groundwater level.

Groundwater Use: Municipal and private water wells supply groundwater to the former Norton AFB and residences and businesses in the nearby community for drinking and other uses. The primary municipal wells are located 2 miles downgradient (southwest) of the base and include the Gage Canal water well complex, located immediately south and southwest of the base, and the Raub, Warren, and Thorne water well complexes, located approximately 1.5 miles southwest of the base. The Raub, Warren, and Thorne complexes are owned by the city of Riverside and used for domestic and agricultural purposes (Figure 6). Three private drinking water wells were identified downgradient of Norton AFB; two wells are located near Waterman Avenue and one is located off of Valley View Road (Figure 8). No other private water wells are being used as a potable source of water for residences or businesses (Earth Tech, 1997b).

Fifteen active wells compose the Gage Canal complex (Figure 6). Five of these wells are located between the southern boundary of the base and the Santa Ana River and nine wells are located south of the river. Most of the Gage Canal wells are screened in the middle to lower aquifers. Eight of the Gage wells (26-1, 27-1, 27-2, 29-1, 29-2, 29-3, 31-1, and 46-1) are screened, at least partially, in the upper aquifer (City of Riverside, 1997; ESI, 1982).

Norton AFB, prior to closure, received its water supply from a system that originally used four deep wells in the middle and lower aquifers (see Figure 6). Additional water was purchased from the city of San Bernardino as needed. Three of the four original base drinking water production wells are located in the central base area; base drinking water well BP-5 is the only well located within the TCE plume area (Martin Marietta Energy Systems, Inc., 1992; Figure 6). The city of San Bernardino took over the Norton AFB water supply system in 1995. The City operates four wells on the former base (BP-3, BP-5, BP-11, and a newly installed well, BP-2A) which are not in use at this time (Tom Dodson & Associates, 1998; ATSDR, 1997b).

Groundwater Quality: Since the early 1980s, trace concentrations of TCE and its degradation products have been detected in several of the off-base drinking water wells in the Bunker Hill basin southwest of Norton AFB, particularly in the wells screened at depths of less than 400 feet (Earth Tech, 1994a, 1997b). No contaminants have been detected above drinking water standards in base drinking water wells being used,⁽²⁾ nor have contaminants been detected in the three private wells located downgradient of Norton AFB (Earth Tech, 1997b). ATSDR reviewed sampling data from Norton AFB drinking water wells from 1979 to the present; sampling data from the city of Riverside wells from 1979 to the present; and annual groundwater sampling data collected since 1995 from the three private wells in the vicinity of the Norton AFB groundwater plume. ATSDR evaluated these data to determine if contaminants in those wells posed any potential health hazards to persons drinking and using the water.

In addition to TCE, tetrachloroethylene (PCE) has also been recognized as a groundwater contaminant in several areas of the Bunker Hill basin upgradient of the base (north of the city of Redlands and east/southeast of the southern sector of Norton AFB) and in the IRP Site 2 area. A report by Ecology & Environment (1987b) indicates that from 1979 to 1984 the Lockheed Corporation gathered groundwater data from wells north of the city of Redlands and southeast of the southern sector of Norton AFB. TCE concentrations in these wells ranged from several ppb to nearly 200 ppb; PCE ranged from 0.12 ppb to 2.5 ppb. During this same time interval, TCE was also detected in wells north of the base ranging from 1.7 ppb to 8.7 ppb; PCE was detected at a maximum level of 1.9 ppb. More recently, PCE and/or TCE were detected in some wells north of the base and northwest of base well BP-11 and in Norton drinking water wells (see Figure 6; Tom Dodson & Associates, 1998; City of Riverside, 1992, 1995). These data suggest that a number of potential upgradient TCE/PCE sources exist besides Norton AFB.

Present and Potential Future Exposures

Norton AFB drinking water wells. No present or future health hazards exist because municipal drinking water wells must meet federal and state drinking water standards. Periodic monitoring of base wells will ensure that drinking water from these wells remains safe to drink. If contamination is found at levels above drinking water standards, the well water will either be blended with unaffected water to safe levels, or treated to reduce contamination levels, or the well will be shut down (Tom Dodson & Associates, 1998). The following data support these conclusions:

• No contaminants were detected above EPA's maximum contaminant levels (MCLs) in the former drinking water wells on Norton AFB (except one sample from BP-5 containing 6.2 ppb of TCE in September 1980; see Table 6) (ESI, 1982; Weston Consultants, 1985; Martin Marietta Energy Systems, Inc., 1992).



• Base drinking water well BP-3 is located cross-gradient to the TCE contamination; therefore, that well has not been affected by the TCE contamination on site (Figures 6 and 9). Recent sampling does, however, indicate PCE contamination at levels below the drinking water standards.



• Although located in the Norton AFB TCE plume, base drinking water well BP-5 is screened at 1,100 ft bgs in the lower aquifer, which is significantly below the depth of TCE contamination in the upper aquifer (Table 4). This well is not affected by the TCE contamination in the upper aquifer (ESI, 1982; Weston Consultants, 1985; Martin Marietta Energy Systems, Inc., 1992).



• Although the newly installed well on base (BP-2A) has consistently had levels of PCE above drinking water standards, this well has not been used to supply drinking water.



• Remediation of the soils on base and the groundwater pump and treat remedies have reduced the TCE contaminant levels existing in or migrating to the groundwater (HAZWRAP, 1997a; See Figures 8 and 9).



• Groundwater will continue to be monitored on- and off-base to ensure drinking water standards are maintained (HAZWRAP, 1997a; Site Characterization Process Action Team, 1994).

Riverside community. Based on the contamination migrating from Norton AFB, the water from present Riverside drinking water wells (and private wells in the area) is safe to drink, and should remain safe to drink in the future for the following reasons:

• Since 1993, the TCE groundwater plume beneath and extending beyond Norton AFB has been reduced (Figures 8 and 9) because of groundwater and soil remedial activities (i.e., two pump and treat systems and soil vapor extraction) (HAZWRAP, 1997a; Site Characterization Process Action Team, 1994). These activities will limit further migration of contaminants into Riverside drinking water wells.



• The Norman Road well was deactivated in 1991 by the South San Bernardino County Water District because TCE was consistently detected above the MCL during the period between 1989 and 1991 (ESI, 1982; Weston Consultants, 1985; Martin Marietta Energy Systems, Inc., 1992). The Norman Road well remains deactivated.



• The Warren No. 2, Warren No. 3, Gage 26-1, Gage 27-1, and Raub 5 wells are the only active Riverside wells that have exceeded the MCL for TCE and/or PCE. Groundwater from these wells are blended with water from other unaffected wells upstream of Norton AFB to reduce contaminant levels to acceptable drinking water standards (City of Riverside Public Utilities Department, 1992, 1995).



• If the city of Riverside requests well head treatment at a well that consistently exceeds the MCL, the Air Force will provide the City with a groundwater treatment system and an alternative water source (Earth Tech, 1994b). Riverside has requested that the Air Force provide well head treatment at the Raub 5 drinking water well; the Air Force is currently installing the treatment.



• Riverside drinking water production wells will continue to be monitored to ensure that the water meets all applicable drinking water standards (HAZWRAP, 1997a; Site Characterization Process Action Team, 1994).



• No contaminants known to be associated with the Norton AFB groundwater contamination have been detected in the three private wells in the area southwest of Norton AFB. These wells will be sampled annually as part of the Air Force Water Supply Contingency Policy Sampling Program (Earth Tech, 1997b).

Past Exposures

Norton AFB drinking water wells. Since monitoring began in 1980, no contaminants have been detected above the MCLs in the four previously used base drinking water wells (BP-2, BP-3, BP-5, and BP-11; see Figure 6) except one isolated hit of 6.2 ppb in September 1980 in well BP-5. Consequently, the drinking water supplied from these wells has remained safe to drink (ESI, 1982; Weston Consultants, 1985; Martin Marietta Energy Systems, Inc., 1992; Table 6). Because no contamination has been detected at elevated levels and the drinking water wells on base are significantly deeper than the TCE contamination, it is unlikely that the wells were affected prior to 1980.

Riverside community. Riverside's municipal water supply (and one nearby private well) did not pose any past public health hazards. Reasons supporting ATSDR's conclusion include the following:

• According to analytical results obtained by the city of Riverside, water samples taken from Raub 5 and Warren 2 wells and from the Norman Road well (owned by the South San Bernardino Water District) from 1989 to 1991 consistently contained TCE concentrations between 1 ppb and 17 ppb. These are the only Riverside wells that demonstrated TCE levels higher than the MCL. Water from these wells has been blended with uncontaminated water from wells upgradient of Norton AFB to reduce contaminant levels to meet EPA and California drinking water standards (City of Riverside Public Utilities Department, 1992, 1995). Water from upgradient wells is unaffected by the Norton plume or any other contaminant plumes in the area. However, some of the unaffected wells are downstream of another local groundwater plume (Newmark plume).



• The South San Bernardino County Water district deactivated the Norman Road in 1991 (ESI, 1982; Weston Consultants, 1985; Martin Marietta Energy Systems, Inc., 1992).



• No contaminants have been detected in the private wells located downgradient of Norton AFB area since sampling began in 1995 (Earth Tech, 1997b).

Abandoned Wells

Abandoned wells were identified during the Norton AFB abandoned well search in the area of the former housing development (not affiliated with Norton AFB) south of Mill Street, east of Tippecanoe Avenue, and north of Central Avenue (Earth Tech, 1997e; see Figure 3). This tract of land lies within the area of the identified TCE groundwater plume. According to Earth Tech (1997a), water to these houses was supplied by the South San Bernardino County Water District. In the absence of historical monitoring data and former use of the abandoned wells in the housing area, ATSDR made several assumptions in order to evaluate the potential for adverse health effects from the consumption and use of these wells in the past.

Accounting for sensitive subpopulations (e.g., children) identified in the demographics section of this report, ATSDR estimated the potential exposure dose for both adults and children. In deriving the human exposure doses, ATSDR incorporated information about the frequency and duration of contaminant exposure and contaminant concentration. ATSDR assumed that adults drank 2 liters of well water each day and weighed 70 kilograms (kg) and children drank 1 liter of water each day and weighed 16 kg. To calculate a conservative exposure dose, ATSDR used the longest possible exposure period, 30 years, which would cover the time span from 1952 to 1982. In the absence of historical abandoned well data, ATSDR used average contaminant concentrations found in monitoring wells (in 1992) upgradient to the former housing area. The average contaminant concentration present in the upgradient monitoring wells in 1992 is likely to be much higher than the concentration present in the abandoned wells prior to 1982. Concentrations were taken from monitoring wells with a depth of 100 to 150 feet bgs, which coincides with the average depth of the abandoned wells found in the housing area.

ATSDR believes that the estimated exposure dose is more conservative (higher) than the actual exposure dose for the following reasons:

• Monitoring well data were only available since 1992, which is 10 years after the sale of the housing property to the Air Force. Contaminant concentrations in 1992 (prior to groundwater treatment remedies on base) are expected to be greater than those that would have been present in the housing area (downgradient to the TCE-source areas) 10 years earlier.



• Data from monitoring wells located upgradient to the housing area were used in the exposure dose calculations. Because these wells are located closer to the TCE contamination source area than the housing area, they will have higher contaminant levels than those assumed to be present in the housing area. In fact, TCE concentrations found in the upgradient monitoring wells were significantly higher than the TCE concentrations detected in monitoring wells directly downgradient to the housing area.



• The exposure duration of 30 years, used in the exposure dose calculations, is extremely conservative. If residents moved out of the area before houses were purchased by the Air Force in 1982 or moved into the area after the early 1950s, when housing first became available in this area, then their exposure durations would likely be less than 30 years. Demographic information indicates that area residents are highly transient in nature--over 80 percent of the residents lived in their current home for less than 10 years in 1990.

Noncancer Effects--ATSDR's estimated exposure doses are compared with health guideline values that are likely to be without an appreciable risk of adverse effects, other than cancer, such as ATSDR's oral minimal risk level (MRL). MRLs have been derived for TCE for acute (14 days or less) and intermediate (15 to 364 days) exposures and were used to evaluate potential noncancer effects associated with past exposures in the former housing area.⁽³⁾ Inadequate data exist for evaluating noncancer effects associated with chronic (365 days or more) exposures to TCE. When evaluating chronic exposures (i.e., the possible maximum 30-year exposure period), therefore, ATSDR cancer guidelines were applied to evaluate potential long-term health effects. A more detailed review of ATSDR's human exposure dose estimates is provided in Appendix C.

The estimated exposure doses for a child and an adult for less than chronic exposures are 0.003 milligrams per kilogram per day (mg/kg/day) and 0.001 mg/kg/day, respectively. Estimated exposure doses for both the child and adult are less than the acute MRL of 0.2 mg/kg/day; therefore, adverse noncancer effects are not expected to be associated with any short-term drinking water exposures. The estimated dose in children slightly exceeds the available MRL for intermediate exposures (i.e., 0.003 versus 0.002 mg/kg/day). Because the MRL represents a conservatively derived health guideline (i.e., the guideline value does not represent the absolute level at which health effects will occur, but has safety values built in) and estimated exposure doses were derived using conservative assumptions (i.e., the estimated dose is most likely higher than the actual exposure dose), exceeding the MRL by such a small factor does not likely indicate the potential for adverse health effects. ATSDR therefore concludes that past exposure to the groundwater from abandoned wells in the housing area was not likely to have resulted in noncancer effects.

Cancer Effects--When evaluating the potential for cancer to occur, ATSDR uses its estimated exposure doses and EPA's cancer potency factor (CPFs), which define the relationship between exposure doses and the likelihood of an increased risk of developing cancer over a 70 year lifetime. A more detailed discussion of CPFs and how they are used to determine whether concern for cancer effects exists is presented in Appendix C.

ATSDR's estimated risk for consumption of contaminated groundwater from the abandoned wells in the former housing area assuming a 30 year exposure period is 6.4 x 10^-6 (or 6.4 excess cancers in a population of 1,000,000). ATSDR believes that exposure at this level does not contribute excess cancer in the population; the level is within the typical range (10^-4 to 10^-6) not considered to cause excess cancer. ATSDR concludes that past exposures to the groundwater from the housing area abandoned wells is not likely to have resulted in cancer.

2. Concern: Radioactivity in groundwater

Could the levels of radionuclides found in the groundwater at Norton AFB result in adverse health effects for residents of neighboring communities or for former employees of Norton AFB?

Conclusions

• No past, present, or potential future health hazards are associated with consuming water from Norton AFB drinking water wells. Since sampling started in 1988, no radiological contamination has been detected in Norton AFB drinking water production wells that has exceeded drinking water standards (San Bernardino Municipal Water Department, 1997).



• No past, present, or potential future health hazards are associated with consuming water supplied by Riverside drinking water wells. Since 1990, radiological contamination in Riverside drinking water wells (particularly in the shallower screened Gage wells, Raub 5, and Warren 2) has consistently exceeded the drinking water standards, but contaminated groundwater is blended with uncontaminated groundwater to reduce radiological levels and meet drinking water standards. (City of Riverside Public Utilities Department, 1992, 1995; San Bernardino Municipal Water Department, 1997).

Discussion

Elevated radionuclide readings in several public supply wells and documentation of radionuclide usage and storage at Norton AFB led to a comprehensive radionuclide investigation of Norton AFB and the surrounding area. Groundwater investigations were conducted at Norton AFB to identify radionuclides of potential concern, quantify background concentrations of radionuclides in groundwater, and determine whether radionuclides are attributable to artificial sources or are naturally occurring.

Norton AFB Hydrogeology: The groundwater of the Bunker Hill basin underlying Norton AFB and the surrounding area is recharged predominantly by runoff from the San Bernardino Mountains. These mountains contain naturally occurring uranium deposits. Erosion of these deposits and runoff down the Santa Ana River and Mill Creek carried and redeposited the uranium-bearing compounds in the Bunker Hill basin. Fine-grained, organic-rich alluvial deposits, related to historical swamp and bog environments in the basin area, contain the elevated levels of naturally occurring uranium. Decades ago, as agricultural and urban demands for groundwater grew, groundwater was depleted more rapidly than it was recharged and the artesian system (flowing wells) in the western part of the base ceased to flow. The groundwater table in this area (a former swamp area) fell more than 100 feet between 1945 and 1968. The lowering of the water table exposed the once-saturated, oxygen deficient, organic-rich sedimentary deposits to the air. Oxidation of those deposits remobilized the uranium causing an increase in the groundwater's radionuclide levels (IT, 1997).

As future demand for groundwater increases, the groundwater table may again decrease and expose more uranium-bearing, organic-rich sediments to oxidizing conditions. This may, in turn, allow for more uranium to become remobilized and leach into the groundwater. Naturally occurring uranium may continue to exceed MCLs for gross alpha radiation (indication of radioactivity), as may total uranium in groundwater samples from the wells within or near the historical bog/swamp area.

Groundwater Quality: Past sampling of groundwater from some city of Riverside drinking water production wells located downgradient to the south and to the east and west of Norton AFB found levels of total uranium (non-detect [ND] to 55 picocuries per liter [pCi/L]) and gross alpha (ND to 59 pCi/L) that exceeded their respective MCLs for drinking water (20 pCi/L [total uranium] and 15 pCi/L [gross alpha]) (City of Riverside Public Utilities Department, 1992, 1995). Monitoring wells on and off the Norton AFB also detected elevated levels of gross alpha (2.38 to 456 pCi/L) and total uranium (ND to 4,956 pCi/L)⁽⁴⁾ (U.S. Air Force, 1995b). Monitoring well (MW)-158 contained the highest observed uranium concentrations (screened from 35 to 55 feet; sample depth of about 50 feet) in the northeast corner of the base.

Past, Present, and Potential Future Exposures

Norton AFB drinking water wells. ATSDR concludes that radiological contaminants detected in Norton AFB drinking water wells do not pose a health hazard. There is no evidence that people have been or will be exposed to radiological concentrations that might result in adverse health effects. Reasons supporting ATSDR's conclusion include the following:

• No drinking water production wells supplying Norton AFB have radiological constituents above their respective MCLs. Gross alpha was detected in on-base drinking water wells between 0.2 pCi/L and 12.60 pCi/L and total uranium was detected at levels ranging from ND to 14.7 pCi/L, which are below EPA and California drinking water standards of 15 pCi/L (gross alpha) and 20 pCi/L (total uranium) (Table 6).



• The available data suggest that radiological constituents detected in groundwater at Norton AFB are not from base activities; no radiological contaminant source has been documented. ATSDR evaluated the sampling results from MW-158, which historically contained quantities of uranium above the MCL (ATSDR, 1996). This well contained uranium and its associated decay products. Furthermore, the detected radiation activities in the sample indicated only naturally occurring radiological material.



• Although total uranium was detected in MW-158 at a level of 4,956 pCi/L in 1991, which greatly exceeds the MCL for drinking water, MW-158 was resampled and found to contain levels 40 times lower than that high result but still 20 times greater than the MCL (Table 8). Moreover, MW-158 is not a drinking water well and is not representative of the radioactivity levels in the drinking water supplied by base wells (USAF, 1995b). No one consumed water from MW-158; therefore, no public health hazards are associated with it.

Riverside community. ATSDR concludes that consumption and use of drinking water supplied by Riverside drinking water wells does not pose any health hazards. This conclusion for present and potential future exposures is based on the following reasons:

• The city of Riverside water supply currently meets California and EPA drinking water standards for gross alpha and uranium.



• Although contamination levels in some of the individual wells tested exceed MCLs at the wellhead, levels are not representative of the water delivered to the household tap. Groundwater is drawn from more than one well at a time, blended with water from other wells, treated, and pumped to storage tanks prior to shipment to the water distribution system as finished water. The contaminant levels of the blended, finished, tap water supplied to residences or other points of use is less than that measured in any of these individual water supply wells (where the MCL was exceeded).



• Riverside currently prioritizes well pumping operations from the Bunker Hill groundwater basin in order to comply with the existing MCLs for gross alpha and uranium (City of Riverside Public Utilities Department, 1992, 1995).



• The state of California (Section 64441 of Title 22, Register 77, No. 45-11-5-77) requires Riverside to test for uranium on a regular basis. Groundwater monitoring will continue to include this requirement (City of Riverside Public Utilities Department, 1992, 1995).

Radiological levels in the drinking water wells supplied by Riverside did not pose a past health hazard. The following reasons support ATSDR's conclusion:

• Contaminants in the Riverside drinking water wells did not exceed MCLs until about 1990.



• After radiologic contamination was detected in some Riverside drinking water wells, the groundwater was blended prior to distribution to residences or other points of use. Monitoring ensured that any radiological contaminant detected above the MCL in an individual well was reduced to drinking water standards before reaching consumers.

3. Concern: Exposure to contaminated soil

Can the locations (especially near the day care facility) and levels of soil contamination, including radiological materials, at Norton AFB result in adverse health effects for nearby residents?

Conclusion

ATSDR concludes that surface soil contamination on Norton AFB does not pose a public health hazard. ATSDR also concludes that the limited areas of radiological-contaminated soil found on Norton AFB do not pose a public health hazard. There is no evidence that people have been exposed to radionuclide contamination at levels that might result in adverse health effects.

Discussion

ATSDR evaluated the data and information presented in site investigation reports, remediation reports for IRP and AOC sites, and work plans to assess potential exposure pathways via soil (see Table 1). ATSDR determined that human exposure to contaminated soil at Norton AFB does not comprise a past, present, or potential future pathway because contamination was either 1) detected at levels that did not pose a public health hazard; 2) detected at depths below the ground's surface that are inaccessible to the general public; or 3) in areas where site access was restricted, unlikely, or infrequent. In addition, most remediation, cleanup, and site restoration on the base has been completed. Deed restrictions are in place to prevent future residential redevelopment in areas where contaminant levels were only reduced to industrial target cleanup goals (TCGs) (See Table 1--IRP Sites 8, 9, 10, 12, 19; AOC Site 40).

ATSDR also evaluated radionuclide soil data for the targeted investigation areas; findings are presented in Table 1. Site investigations to determine potential radionuclide contamination included a drive-over survey and background soil sampling/trenching.⁽⁵⁾ No radionuclides were detected in surface soils at these areas. Contamination was detected above cleanup goals in the soils outside Building 752 beneath the industrial waste line, but contamination was restricted to subsurface soils that are inaccessible to the public. Any soil that was found to be contaminated has been excavated (IT, 1996a).

The former day care facility located on base in Building 24 was constructed in 1979 (U.S. Air Force, 1993b). This building has been re-opened as a day care facility, Smart Start Day Care, for approximately 1 year. This building is not located near any of the identified areas of concern for potential soil or radiological contamination (see Figure 2). The Norton AFB Environmental Baseline Survey (1993b) classified the day care facility and the adjacent surrounding area as Category I property. An area designated Category I indicates that no storage, release, or disposal of hazardous substances or petroleum products has occurred (including no migration of these substances from adjacent areas) (U.S. Air Force, 1993b). Consequently, no past human exposures to contamination at the on-site day care facility occurred and no apparent health hazards are associated with the facility's former use. Likewise, no current or future health hazards are associated with the continued use of this building as a day care.

4. Concern: Other Public Health Concerns

Is there any connection between multiple chemical exposures from Norton AFB and self-reported medical illnesses (e.g., cancer, lupus, and migraines) of community members living in the vicinity of Norton AFB? Are these self-reported health problems and other problems reported by residents concerning their homes (e.g., gas fumes, phosphorous red staining) related to an alleged military dump?

Conclusion

No data indicate that the general public was exposed to any chemicals at Norton AFB that posed a public health hazard. For any of the health concerns discussed below, please consult your primary care physician. Because of the scope of operations or work performed at Norton AFB, it is possible that workers were exposed to several different chemicals. Occupational exposure to chemicals and other worker health and safety issues are evaluated by or governed by the Occupational Safety and Health Administration, National Institute of Occupational Safety and Health, and various state agencies. Adverse health effects and problems with area houses are not associated with contaminants detected at Norton AFB or an alleged military dump. Throughout site and remedial investigations, no such dump has been located on Norton AFB.

Discussion

Cancer. Contaminants in soil and groundwater are at levels that do not pose a public health hazard. No identified exposure pathways exist for all environmental media (i.e., groundwater, soil, air); therefore, Norton AFB activities are not a likely source for the self-reported increased cancer cases.

Lupus. Systemic lupus erythematosus is a chronic multisystem autoimmune inflammatory disorder. The exact cause of lupus is largely unknown and risk factors remain obscure (Riedel and Pottern, 1992). Since environmental data indicate low contaminant levels in soil and groundwater and no identified exposure pathways via all environmental media, Norton AFB is not likely the source of the reported increased lupus cases.

Migraines. Contaminants in soils and in groundwater at Norton AFB are present at levels that do not pose a human health hazard. Consequently, Norton AFB is not a likely cause for the reported increased migraine cases.

House Problems. No alleged dump has been found during the site and remedial investigations at Norton AFB. No contaminants in soil or groundwater are present at levels that pose a problem to houses or to humans. Consequently, Norton AFB is not a likely cause for the reported house problems (e.g., gas fumes, phosphorus red staining).

CONCLUSIONS

ATSDR concludes that the TCE-contaminated groundwater does not pose a public health hazard because, to date, contaminants have not been detected in drinking water wells on- or off-site at concentrations that might result in adverse human health effects.

• Drinking water supplied from the four previously used base drinking water wells was safe to drink in the past. Water supplied by the two wells (BP-3 and BP-5) that will remain in use on base are presently safe to drink and will remain safe to drink in the future. Although the newly installed base well (BP-2A) has consistently had levels of PCE above safe drinking water standards, this well has not been used to supply drinking water. Only one of the base drinking water wells lies in the TCE plume area (base well BP-5; See Figure 6). BP-5 draws water primarily from the lower aquifer and is significantly deeper than the contaminants detected in the upper aquifer. Consequently, BP-5 has not been contaminated with TCE (see Table 6). Ongoing monitoring of these wells, and if needed, taking actions like blending, treatment, or shutting down a well will ensure that water supplied from these wells meets safe drinking water standards.



• Riverside drinking water, which is partially supplied by drinking water wells downgradient of the Norton AFB TCE contamination plume, did not in the past and do not presently pose a public health hazard. Riverside supply well data from 1979 indicate that TCE levels in most of the Riverside drinking wells have not been above MCLs. Although analytical results obtained by the city of Riverside from 1989 to 1991 indicate that two supply wells (Raub 5 and Warren 5) and one well from South San Bernardino County Water District (Norman Road) consistently had TCE concentrations from 1 to 17 ppb, operations have ensured that the water was and is blended or otherwise treated to meet EPA's drinking water standards. In addition, two pump and treat systems are operating in the TCE plume area to reduce contaminant levels and prevent further contaminant migration.



• No past or present public health hazards exist from exposure to the private drinking wells located downgradient of the Norton AFB TCE plume. The wells have been tested and no contaminants were detected.



• No public health hazards are associated with consumption of water from abandoned wells in the former housing area property now owned by the Air Force. ATSDR estimated exposure doses and noncancer and cancer effects from ingesting water from these wells; levels were below those associated with health effects.

ATSDR concludes that radiological contaminants detected in Norton AFB drinking water wells and Riverside drinking water wells downgradient of Norton do not pose a health hazard . There is no evidence that people have been or are exposed radiological contamination in the drinking water at concentrations that might result in adverse health effects.

• No past, present, or potential future health hazards are associated with consuming drinking water from Norton AFB drinking water wells. Detected levels of radiological contaminants have not exceeded the drinking water standards in samples collected from wells on Norton AFB from 1988 to the present (see Table 6).



• No past, present, or potential future health hazards are associated with consuming drinking water from groundwater supplied by Riverside drinking water wells. Although radiological contamination in Riverside drinking water wells (particularly Gage, Raub 5, and Warren 2) has consistently exceeded drinking water standards since 1990, contaminated groundwater is blended with unaffected groundwater to reduce radiological levels to those that do not pose a public health hazard.

ATSDR concludes that soil contamination on Norton AFB does not pose a public health hazard. There is no evidence that people have been exposed to chemical or radiological contamination concentrations in surface soils at levels that might result in adverse health effects.

• Soil contaminants were either detected at levels that did not pose a public health hazard; located at depth below the ground surface that are inaccessible to the general public; or otherwise restricted from the public access making exposure infrequent or unlikely. In addition, most remediation, cleanup, and site restoration on the base has been completed.

On the basis of information available on contamination of groundwater and on localized contaminated soils, ATSDR concludes that the Norton AFB site should be assigned to the No Apparent Public Health Hazard category.

PUBLIC HEALTH ACTION PLAN

The Public Health Action Plan (PHAP) for Norton AFB contains a description of actions taken and those to be taken, as necessary, by ATSDR, the Air Force, EPA, and the California Department of Health at and in the vicinity of the site subsequent to the completion of this public health assessment. The purpose of the PHAP is to ensure that the public health assessment not only identifies public health hazards, but provides a plan of action designed to mitigate and prevent adverse human health effects resulting from exposure to hazardous substances in the environment. The public health actions that are completed, being implemented, or planned are as follows:

Completed Actions:

• The Air Force completed investigations at the 22 IRP sites and 73 AOCs to identify potentially contaminated areas. Soil investigations, cleanup, and site restoration is completed at most of these targeted areas (see Table 1).



• Two pump and treat systems have been installed in the Norton AFB TCE plume area to reduce contamination and to prevent further migration of contamination into downgradient drinking water supplies.



• IRP Sites 8, 13, and 14 and AOC Sites 3, 23, 37, 39, 40, and 44 have been closed with regulatory approval.



• Soil vapor extraction (SVE) has successfully removed over 7,000 pounds of TCE from the soils. The SVE system is being dismantled with EPA (California and United States) approval. Soil confirmation samples of the affected area indicate remaining levels of contamination will not adversely impact the groundwater.



• The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA; also known as Superfund), as amended, requires ATSDR to conduct needed follow-up health actions in communities near hazardous waste sites. To identify appropriate action, ATSDR created the Health Activities Recommendation Panel (HARP). HARP has evaluated the data and information contained in the Norton AFB Public Health Assessment for appropriate public health actions and did not identify the need for follow-up public health activities.

Ongoing Actions:

• As identified in the long-range Water Supply Contingency Policy, groundwater in on- and off-base wells is being monitored to determine the extent of the TCE groundwater plume.



• The Air Force will continue operating the pump and treat systems in the TCE plume area to mitigate and contain the contamination.



• If the off-site private wells in the plume area remain in use, they will continue to be tested annually for potential contamination.



• New and existing drinking water wells on base will continue to be monitored to ensure compliance with regulatory standards.



• The city of Riverside will continue to regularly monitor the public water supply to ensure compliance with regulatory standards.



• The Air Force will continue to bring contaminated surface and subsurface soils from other IRP sites to IRP Site 2. These soils will be stabilized on IRP Site 2 and will be used as part of the foundation layer for the landfill cap. Other site remediation projects will be completed by winter 1997. Deed restrictions to prevent residential redevelopment of this area will be required if soil contaminant levels are only reduced to industrial target cleanup goals.



• The Air Force will also continue remedial activities at the landfill on IRP Site 2 by installing a 25-acre cap and a landfill gas extraction and treatment system. Landfill cap construction is planned from January to December 1998.



• The Air Force will install two new wells in the perched groundwater table (around 25 feet deep) at IRP Site 17 during the summer 1997 to remove the shallow layer of contaminated groundwater above the upper aquifer. Soil gas sampling of any dry wells in this perched zone will also take place quarterly for 5 years.

Planned:

• IRP Sites 16 and 21 will be officially closed by the Air Force under state RCRA regulations pending the results of groundwater sampling conducted over the past year.



• The Air Force submitted an Engineering Evaluation and Cost Estimate (EE/CA) for regulatory review of AOC 70. This process will be completed by May 1998.



• If future data indicate the presence of contaminants in drinking water at levels of potential health concern, ATSDR will review that data and determine if further action(s) may be necessary.

PREPARERS OF REPORT

W. Mark Weber, Ph.D.
Environmental Health Scientist
Federal Facilities Assessment Branch
Division of Health Assessment and Consultation

Gary Campbell, Ph.D.
Environmental Health Scientist
Federal Facilities Assessment Branch
Division of Health Assessment and Consultation

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Hazardous Waste Remedial Action Program. 1996g. Final Technical Memorandum Expanded Source Investigation Addendum Number 1 for Norton AFB. November 7, 1996.

Hazardous Waste Remedial Action Program. 1997a. Final Fourth Annual Groundwater Data Trends Report and Long-Term Groundwater Monitoring Plan for Norton AFB. February 25, 1997.

Hazardous Waste Remedial Action Program. 1997b. Action memorandum AOC 44/IRP Site 10/IRP Site 12. March 4, 1997.

Hazardous Waste Remedial Action Program. 1997c. Explosive Ordinance Disposal Proficiency Training Area (Area of Concern 73) Clearance Report. April 28, 1997.

HAZWRAP. See Hazardous Waste Remedial Action Program.

IT Corporation. 1995. Draft Preliminary Groundwater Sampling and Analysis Informal Technical Information Report, Basewide Radionuclide Characterization, Norton Air Force Base, California. April 7, 1995.

IT Corporation. 1996a. Draft Final Basewide Soil Characterization Report, Basewide Radionuclide Characterization, Norton Air Force Base, California. June 1996.

IT Corporation. 1996b. Basewide Soil Characterization Report, Basewide Radionuclide Characterization, Norton Air Force Base, California. August 1, 1996.

IT Corporation. 1997a. Draft Basewide Soil Characterization Report, Basewide Radionuclide Characterization, Norton Air Force Base, California. February 1997.

IT Corporation. 1997b. Draft Basewide Soil Characterization Report, Basewide Radionuclide Characterization, Norton Air Force Base, California, Building 752 Pipeline Removal Report Addendum. February 1997.

Morrison Knudsen Corporation. 1996. Draft: Norton Operating Location Air Combat Camera Services Closure Certification Report. May 1996.

Norton Air Force Base. Installation Restoration Program Brochures. Various dates.

Norton Air Force Base. 1994a. Installation Restoration Program. Restoration Advisory Board. San Bernardino, CA. January 1994.

Norton Air Force Base. 1994b. Supplemental Environmental Baseline Survey. San Bernardino, CA. March 1994.

Norton Air Force Base. 1995a. Installation Restoration Program. Fact Sheet No. 8. San Bernardino, CA. January 1995.

Norton Air Force Base. 1995b. Installation Restoration Program. Fact Sheet No. 9. San Bernardino, CA. February 1995.

Norton Air Force Base. 1996a. Installation Restoration Program. Restoration Review 2(3). San Bernardino, CA.

Norton Air Force Base. 1996b. Installation Restoration Program. Restoration Review 2(4). San Bernardino, CA.

Norton Air Force Base. 1996c. Installation Restoration Program. Restoration Review 2(5). San Bernardino, CA.

Norton Air Force Base. 1996d. Installation Restoration Program. Factsheet Series No. 14. San Bernardino, CA. April 1996.

Norton Air Force Base. 1996e. Underground Storage Tanks Removal Program. San Bernardino, CA. June 1996.

Norton Air Force Base. 1997. Data Summary Report for the Radiological Investigation of the Sanitary Sewer. San Bernardino, CA. March 1997.

Ogden Environmental and Energy Services Co., Inc. 1997. United States Air Force Installation Restoration Program Volume I Closure Report. May 1997.

Riedel, D.A., and Pottern, L.M. 1992. The Epidemiology of Multiple Myeloma. Hematology/ Oncology Clinics of North America 6(2). April 1992.

San Bernardino Municipal Water District. 1997. Well data. 1997.

Site Characterization Process Action Team. 1994. Long Term Groundwater Monitoring Program Guidance, prepare for the California Base Closure Environmental Committee. 1994.

Snedeker, C.H. 1986. Norton Air Force Base and San Bernardino: Communities in symbiosis. California State University. October 1986.

Taylor, G.C. 1994. Mineral Land Classification of a Part of Southwestern San Bernardino County: The Big Bear Lake-Lucern Valley area, CA. DMG Open-File Report 94-06. 1994.

Tom Dodson & Associates. 1998. Water Quality Data from Domestic Wells at the Former Norton AFB. March 11, 1998.

US Air Force. 1993a. Central Base Area Operable Unit--Record of Decision. November 24, 1993.

US Air Force. 1993b. Basewide Environmental Baseline Survey Norton Air Force Base, California. December 1993.

US Air Force. 1995a. Public release: Investigation at golf course finds no bunker, no radium paint waste, no radioactivity above background. March 2, 1995.

US Air Force. 1995b. Public release: Resampling of monitoring well MW-158 indicates natural uranium isotopes occurring at levels 40 times lower than previously reported. March 20, 1995.

US Air Force. 1995c. Draft--Off-Base Water Supply Contingency Policy. May 1995.

US Air Force. 1995d. Private well sampling results from Earth Tech, included with letter written by Gary J. Jungwirth, Assistant Base Environmental Coordinator, to Ed Imsand at Meadowbrook Dairy. May 5, 1995.

US Air Force. 1995e. Letter written by Gary J. Jungwirth, Assistant Base Environmental Coordinator, to David Garcia, Public Utilities/Water Engineering at City Hall, San Bernardino, CA. May 22, 1995.

US Air Force. 1996a. Installation Restoration Program; Action Memorandum--IRP Site 1. March 1996.

US Air Force. 1996b. Final Decision Document To Support No Further Response Action Planned at IRP Sites 7, 11, 15, and 18. April 17, 1996.

US Air Force. 1996c. Underground Storage Tanks Removal Program: Draft Closure Report--Former Underground Storage Tank Site at Building 647, IRP Site 6. June 1996.

US Air Force. 1996d. Decision Document To Support No Further Action Planned at IRP Sites 3 and 4. August 1, 1996.

US Air Force. 1996e. Community Relations Plan for Norton Air Force Base Installation Restoration Program. August 1996.

US Air Force. 1996f. Interim Record of Decision, OU 3, IRP Site 19, Waste Drum Storage Area No. 1. October 11, 1996.

US Air Force. 1997a. Restoration Review. Norton AFB, San Bernardino, CA. Volume 3, Issue 2. March 1997.

US Air Force. 1997b. Action Memorandum Installation Restoration Program Site 17/Industrial Waste Treatment Plant Perched Zone Groundwater. March 27, 1997.

Wade, M.C., B.L. Beatty, and P. Philip. 1994. Fall 1994 Wildlife and Vegetation Survey, Norton AFB. Oak Ridge Nation Laboratory. Report Number ORNL/TM-12886. December 1994.

Weston Consultants. 1985. Final Report Phase II, Stage 1--Problem Confirmation Study on Norton Air Force Base, San Bernardino, CA. 1985.

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1. The Norman Road Well is owned by the defunct South San Bernardino County Water District.
2. Except one detection of 6.2 ppb in September 1980 in well BP-5 which only slightly exceeds the MCL of 5 ppb. This slightly elevated concentration is the only detection of TCE above the MCL in base drinking water wells.
3. The intermediate MRL has been recently withdrawn as a formal ATSDR guideline; see Appendix C.
4. One time detection in 1991. Monitoring well resampled and results indicate total uranium levels 40 times lower.
5. Site investigations include the following: Accelerated IRP Site 20 investigation; field work at Building 763 (south Apron Area); and investigations at Buildings 658, 795, and outside 752, as well as the housing area anomaly, MW-158 area, IRP Site 1, and the Industrial Waste Treatment Plant (IWTP).

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