PUBLIC HEALTH ASSESSMENT
MOFFETT NAVAL AIR STATION
(a/k/a MOFFETT FEDERAL AIRFIELD)
MOUNTAIN VIEW, SANTA CLARA COUNTY, CALIFORNIA
|Site||Site Description/Waste Disposal History||Investigational Results/ Environmental Monitoring Results1,2,3,4||Corrective Activities and/or Current Status||Public Health Evaluation|
OU1 (Sites 1 and 2)
|(1) Runway Landfill||From the 1960s to 1978, the landfill received various waste solvents, refuse, and scrap equipment. The landfill was never formally closed.||Soil Gas: Volatile organic compounds
(VOCs) and methane were detected at elevated concentrations.
Surface and Subsurface Soil: VOCs and semi-volatile organic compounds (SVOCs) were detected below ATSDR comparison values (CVs). Polychlorinated biphenyls (PCBs) were detected above CVs at a maximum of 18 parts per million (ppm). Soils were not analyzed for total petroleum hydrocarbons (TPH).
Leachate: The following VOCs were detected above CVs in multiple samples: benzene (15 parts per billion [ppb]) and 4-methylphenol (7,900 ppb -- no CV established). Other VOCs and SVOCs were detected below CVs. PCBs were detected above CVs (1.40 ppb). Leachate was not analyzed for TPH.
Groundwater: Bis(2-ethylhexyl)phthalate (BEHP) was detected sporadically above CVs; as this compound was not detected in leachate, detections were attributed to laboratory contamination. VOCs and pesticides were detected below CVs. TPH was sporadically detected.
Surface water and sediment: TPH compounds were detected as follows in surface water in the Storm water retention pond north of Site 1 and in Jagel Slough: TPH extractable as JP-4 (50 ppb); TPH extractable as diesel (92 ppb); TPH extractable as motor oil (850 ppb); and TPH extractable as other heavy TPH components (1,300 ppb). However, these compounds were determined to have come from Storm water runoff rather than from Site 1. Sediment from the Storm water retention pond was analyzed for PCBs; none were detected.
|Wastes from Sites 1 and 2 were consolidated at Site 1. The Site 1 landfill was capped. A passive gas venting trench was installed to prevent landfill gas migration. Landfill gas monitoring is being conducted. A groundwater collection trench was also constructed, and water in this trench will be monitored.||No apparent past, present, or future public health hazards
exist, because of a lack of significant exposure.
Soils: This site is inaccessible to the public and the landfill has been capped, eliminating any possible exposure to landfill soil. Any exposures that occurred in the past were most likely only incidental.
Leachate and Groundwater: Organic contaminants from leachate have not migrated into groundwater. Furthermore, groundwater is not used for public consumption and most likely will not be in the future.
Surface Water and Sediment: Surface waters are not used recreationally.
|(2) Golf Course Landfill||From the 1940s to the 1960s, the landfill received various waste solvents, refuse, and scrap equipment. A burn pit was used for disposal of outdated flares and cartridge activated devices until 1978.||Soil gas: Tetrachloroethylene (also known
as perchloroethylene or PCE) was detected in gas in the center of the landfill.
No evidence of methane migration was found and landfill gases were not detected
at the surface.
Soils: VOCs and SVOCs were detected below CVs. Aroclor 1254 was detected above its CV (at 28 ppm) in a subsurface landfill soil sample. Soils were not analyzed for TPH.
Leachate: The following VOCs were detected above CVs in multiple samples: benzene (38 ppb), total 1,2-dichloroethylene (DCE) (110 ppb), vinyl chloride (120 ppb), and PCE (7 ppb). Other VOCs and one SVOC were detected below CVs.
Groundwater: Trichloroethylene (TCE) was detected just above its CV in an upgradient monitoring well. (This probably represents the fringe of the OU5 plume -- see below.) Other VOCs were detected sporadically.
Surface Water and Sediment: Samples taken from the perimeter of the saltwater evaporation pond were analyzed for VOCs, SVOCs, and PCBs. Only BEHP (a common laboratory contaminant) was detected, at 7 ppb. Samples taken from the Navy Channel and Northern Channel were analyzed for TPH. The Northern Channel contained TPH extractable as motor oil (1,300 ppb) and extractable as diesel (120 ppb). The Navy Channel contained TPH extractable as motor oil (900 ppb) and extractable as diesel (180 ppb). TPH compounds were not thought to come from Site 2, however, because they were not found consistently in groundwater monitoring wells.
|Wastes from above and below the water table at Site 2 were relocated to Site 1. Site 2 was backfilled and restored. Groundwater monitoring will be conducted for a minimum of 3 years.||No past, present, or future public health hazards exist. It is unlikely that significant exposure to site-related contaminants occurred in the past. The site has been fully remediated.|
OU2-East (Soils at Sites 3, 4, 6, 7, 10-East, 11, and 13)
|(3) Marriage Road Ditch||Extends for approximately 2,000 feet along the eastern side of Marriage Road and is 5 to 6 feet below sea level. From the 1940s to the 1970s, this site received waste oils, solvents, fuels, detergents, paints, and hydraulic fluids via storm drains from Hangars 2 and 3.||Soil Gas: A plume with elevated VOC levels
was found during Phase I, but was not found during Phase II.
Soil: All VOCs and SVOCs detected were below CVs and/or are common laboratory contaminants. PCBs were detected during Phase I, but were not found in Phase II. TPH was detected in Phase I sampling, but was not found during Phase II.
|No action.||No past, present, or future public health hazards exist. It is unlikely that significant exposure to site-related contaminants occurred in the past. Levels of contaminants currently present at the site do not pose a health hazard based on current and likely future use.|
|(4) Abandoned Wastewater Holding Ponds||From 1968 to 1978, former ponds received waste and wastewater from activities at Hangars 2 and 3. Hazardous materials disposed of included fuels and oils, paint sludge and stripper, solvents, chlorinated VOCs, and ethylene glycol. Former ponds were removed, closed, and replaced by the industrial wastewater flux ponds.||Soil: VOCs, SVOCs, and PCBs were detected below CVs. TPH (extractable as JP-5) was detected below risk-based screening levels (RBSLs).||No further action.||No past, present, or future public health hazards exist. It is unlikely that significant exposure to site-related contaminants occurred in the past. Levels of contaminants currently present at the site do not pose a health hazard based on current and likely future use.|
|(6) Runway Apron||From the 1940s to the 1970s, this area was used for casual disposal of wastes from aircraft maintenance, including solvents, fuels and oils, and paints. In 1979, Hangar 3 aprons were enlarged by paving over this area.||Soil: VOCs and SVOCs were detected below CVs. TPH (extractable as JP-5) was detected below RBSLs.||No further action.||No past, present, or future public health hazards exist. It is unlikely that significant exposure to site-related contaminants occurred in the past. Levels of contaminants currently present at the site do not pose a health hazard based on current and likely future use.|
|(7) Hangars 2 and 3||Unpaved areas at the corners of hangars were used to discard wastes such as paints, solvents, fuels and oils, and hydraulic fluids. In addition, several large fuel tanks and a steam cleaning waste sump were located at the northeast corner and on the east side of Hangar 3. These tanks (Tanks 2 and 43) had leaked and were removed and investigated as Site 19.||Soil: VOCs and SVOCs were detected below CVs. TPH (extractable as JP-5) was detected below RBSLs.||No action.|
|(10-East) Runways||Site 10-East encompasses the runway and tanks and sumps in the area southwest of the runway and north of the Bayshore Freeway. Site 10 tanks and sumps were used for storage, separation, or disposal of petroleum products or solvents. Many of these tanks and sumps are designated as separate sites. The tanks and sumps that are considered only as Site 10 include Tanks 21, 33 through 41, 51, 52, and 57.||Soil: VOCs and SVOCs detected were common laboratory contaminants and were below CVs. TPH (extractable as JP-5) was detected below RBSLs.||No action.|
|(11) Engine Test Stand Area||The site was used to test aircraft engines under power for an unknown period of the facility's history. The test area is covered by concrete and asphalt and has a small drainage depression that funnels waste oils, hydraulic fluids, and fuels to the southern edge of the pad.||Soil: VOCs and SVOCs were detected below CVs. TPH (extractable as JP-5) was detected below RBSLs.||No action.|
|(13) Equipment Parking Area||This area consists of a lot used for support vehicle parking and a building used for repair and maintenance of support equipment. Waste and industrial wastewater from spills, leaks, and equipment washing were flushed into a surface drainage ditch adjacent to the parking area. A sump is present on the southwest corner of Building 142 that received stripping/vehicle-steam-cleaning wastes.||Soil: VOCs and SVOCs were detected below CVs. TPH (extractable as JP-5) was detected below RBSLs.||No action.|
OU2-West (Soils at Sites 8, 10-West, 14-North, 16, 17, and 18)
Note: The aquifers on the west side of MFA are affected by a regional groundwater plume that originates at the Middlefield-Ellis-Whitman (MEW) Superfund site. (The MEW site is located south of MFA and is named for the roads which bound it.) The OU2-West soils overlie this aquifer and may be affected by the contamination that originates off-site. In October 1992, EPA determined that because the west-side aquifers of MFA and the overlying soils were affected by the MEW plume, they were subject to the 1989 Record of Decision (ROD) for the MEW site. These soils have been remediated to cleanup standards specified in the MEW ROD.
|(8) Waste Oil Transfer Area||From the 1940s to the 1980s, a 5000-gallon tank at the site received waste oil that reportedly included about 100 gallons per year of transformer oils (possibly containing PCBs) and about 200 gallons per year of solvents. Oil was reportedly spilled onto the ground during transfer from the trucks to the sump feeding the tank. Both the tank and sump were removed in 1981. Vehicles in the adjacent storage yard may also have leaked petroleum products onto the soils.||Soil: VOCs and SVOCs were detected below CVs. TPH (extractable as JP-5) was detected in Phase I surface samples, but not in Phase II samples.||NASA excavated and disposed of soils off-site to reduce the potential for further releases to groundwater.|
|(10-West) Chase Park||Chase Park is located between U.S. Highway 101, Girard Road, Dailey Road, and the transportation maintenance area.||Soil: No contaminant sources have been identified in the Chase Park area.||No action.||No past, present, or future public health hazards exist. No contaminant sources were identified.|
|(14-North) Tanks 67 and 68||Tanks 67 and 68 were located between the dry cleaner's building and the NEX gas station. The age, contents, volume, and use of the tanks is unknown. Tank 67 was removed in May 1990 and Tank 68 was removed in July 1994 during the Building 88 remedial action.||Soil: No contamination was identified at either tank.||No further action.||No past, present, or future public health hazards exist. No contaminant sources were identified.|
|(16) Public Works Steam Cleaning Rack (Sump 60)||The Public Works Steam Cleaning Rack is within the Public Works Vehicle Yard. The steam cleaning rack consisted of two catch basins that drained a concrete wash pad and drain to an underground oil/wash separator. The sump was removed as part of the Phase II removal action which was completed in 1991.||Soil: No contamination was identified in sample data collected during the sump removal.||No further action.||No past, present, or future public health hazards exist. No contaminant sources were identified.|
|(17) Paint Shop Sump 61||This sump received wastes from the paint shop and from Hangar 1. Wastes from the paint shop included oil- and latex-based paints, thinners, toluene, and turpentine. The types of wastes received from Hangar 1 are unknown. Sump 61 and surrounding contaminated soils were removed in 1991.||Soil: No further contamination remains at this site.||No further action.||No past, present, or future public health hazards exist. It is unlikely that significant exposure to site-related contaminants occurred in the past. No contamination remains at the site.|
|(18) Dry Cleaner's Sump 66||In the dry cleaner's building (Building 88), sinks and floor drains at the extractor/spotting station and floor drains near the dry cleaning machines flowed into Sump 66. Field observations during a 1987 investigation found cracks in the sump. The sump was removed in 1990.||Soil gas: Elevated levels of VOCs were
Soil: VOCs were detected below CVs.
|In 1994, the building, foundation, underground piping, and Tank 68 and Sump 91 (also located on the northern side of the building) were demolished and removed; soil was excavated and treated.|
OU4 (West-Side Aquifers)
|Ground-water under sites: 8, 9, 12, 14, 16, 17, 18; portions of 10, 15, 19||The aquifers on the west side of MFA are affected by a regional groundwater plume that originates at the MEW Superfund site. (See note for OU2-West.) In addition, Navy sources have released contaminants to the aquifer. Dry Cleaner's Sump 66 (Site 18) was a source of PCE and possibly TCE and other chlorinated organics. Although the sump has been removed, soils at the site are still a potential source of groundwater contamination. Site 9 was a source of petroleum and possibly VOC contamination.||Groundwater: Groundwater contamination appears to be
confined primarily to the A1 and A2 aquifer zones with minor
amounts of contaminants present in the B2 aquifer zone.
Concentrations of the VOCs TCE, 1,2-DCE, 1,1-DCE, and
PCE all exceed CVs. The primary contaminant of concern is
TCE, with maximum concentrations of 12,000 ppb in the A1
aquifer and 18,000 ppb in the A2 aquifer. The on-site extent of
contamination extends from Highway 101 to approximately
Site 8. 1,2-DCE and 1,1-DCE plumes are centered in
approximately the same location as the TCE plume.
Maximum concentrations in the A1 and A2 aquifers are as
follows: 1,2-DCE (1,700 ppb -- A1; 880 ppb -- A2); 1,1-DCE
(200 ppb -- A1; 1,300 ppb -- A2). Two small PCE plumes are
present in the A1 aquifer and one in the A2 aquifer, with
maximum concentrations of 7,800 ppb and 480 ppb,
Small isolated areas of petroleum hydrocarbons were observed and are associated with releases from fuel storage tanks in the vicinity of Site 9 at MFA. At free product well FP9-01 near Site 9, the maximum TPH concentration was 20,000 ppb. In addition, a potential petroleum hydrocarbon source may exist at the Jet Fuel Supply Area on the NASA-Ames Research Center property.
|In October 1992, EPA determined that because the west side aquifers of MFA were affected by the MEW plume, they were subject to the 1989 ROD for the MEW site. In conjunction with the MEW groundwater remediation program, the Navy is controlling contaminants in the west-side aquifers originating from Navy sources. The Navy has constructed a pump and treat system to remediate the groundwater in the area of Site 9. This system will work in conjunction with others operated by NASA and the MEW companies, to form a regional pump and treat system.||No past, present, or future public health hazards exist. The shallow aquifers are not used for any purpose. Drinking water at MFA was historically supplied from the deep aquifer, but is now supplied by municipal sources which rely primarily on surface water. It is unlikely that water from the shallow aquifers will be used in the future; in any case, such use would not occur before cleanup is completed.|
OU5 (East-Side Aquifers)
|Groundwater under Sites 3, 4, 5, 6, 7, 11, 13, 21, 22, 23, 24; portions of Sites 10, 15, 19; weapons bunkers; industrial flux ponds||See descriptions for individual sites (above and below). The chlorinated hydrocarbon contamination is thought to originate at Site 7. Petroleum hydrocarbons come from Sites 5, 19, and 24.||Groundwater:
A1 aquifer: The East Side A1 aquifer is contaminated both by petroleum hydrocarbons and by chlorinated hydrocarbons. Since 1989, sampling has indicated that the main contaminants in the chlorinated hydrocarbon plume are TCE (140 ppb), 1,2-DCE (90 ppb), PCE (260 ppb), 1,2-dichloroethane (DCA) (14 ppb), 1,1-DCE (16 ppb), and vinyl chloride (89 ppb). (All of these values, except 1,2-DCE, are well above CVs.) There are two plumes, southern and northern. (Note: High concentrations of VOCs were detected in samples from well W-7 near former Tank 43 during 1983-1985. These included PCE [110 ppb], TCE [7,900 ppb], 1,2-DCE [22,000 ppb], and vinyl chloride [2,800 ppb]). A TPH plume at Site 5 had a maximum TPH extractable concentration of 2 million ppb. TPH extractable at Site 19 had a maximum concentration of 99,000 ppb. At the high-speed fuel hydrants at Site 24, the maximum TPH extractable concentration was 21,000 ppb.
A2 aquifer: Chlorinated VOCs were detected sporadically and at low levels. Contaminants from the A1 petroleum plume have not been detected in the A2 aquifer.
B and C aquifers: Although BEHP has been detected in these aquifers, it is attributed to laboratory contamination.
|The OU5 ROD was issued on June 28, 1996. The major components
of the selected remedy for the southern plume include:
--Institutional controls: Fencing of the treatment system area; operation and maintenance of Building 191 and storm drainage system; and domestic use restrictions on the groundwater at OU5
--Extraction and treatment of groundwater using an air stripping system followed by discharge. The discharge method for OU5 is discharge to surface water. The construction of the groundwater treatment system was completed and is scheduled to start up in the 1998.
No action other than groundwater monitoring was deemed to be required for the northern plume.
|No past, present, or future public health hazards exist. The shallow aquifers are not used for any purpose. Drinking water at MFA was historically supplied from the deep aquifer, but is now supplied by municipal sources which rely primarily on surface water. It is unlikely that water from the shallow aquifers will be used in the future; in any case, such use would not occur before cleanup is completed.|
PETROLEUM SITES (Sites 5, 9, 12, 14-south, 15, and 19)
Note: Based on San Francisco Bay Area Regional Water Quality Control Board guidance issued in 1996, petroleum sites at MFA are being evaluated using RBSLs for various possible receptor scenarios. Soil RBSLs for MFA were presented in the "Draft Petroleum Site Evaluation Methodology Technical Memorandum" (PRC, 1997); groundwater evaluations were to be conducted individually for each site. Thus, this table compares TPH levels in soil at each site to RBSLs, but simply presents (with no comparison) TPH concentrations associated with the various petroleum-related groundwater plumes that have been identified.
|(5) Fuel Farm Area||Site 5 operates as the main fuel facility for NAS Moffett Field. The site has a northern and southern section, and includes 18 tanks (14 underground storage tanks [UMTS] and four above-ground storage tanks [ACTS]) which receive and dispense petroleum products for base activities. Many of the tanks have an associated sump and discharge pipe; wastes from discharge pipes were historically dumped on the ground or into dry wells in the vicinity. Active tanks include USTs 10, 11, 12, and 13 (which have been tested for leaks) and ASTs 72, 73, 74, and 75. USTs 4, 5, 6, 7, 8, 9, 18, and 26 were removed.||Soil: VOCs, SVOCs, and PCBs were detected below CVs. TPH was detected below RBSLs.||A pilot test to evaluate the effectiveness of using bioventing and biosparging to treat soil and groundwater was conducted. The Navy is awaiting further evaluation using risk-based screening level guidance from the State of California.|
|(9) Old Fuel Farm||At the old fuel farm at Building 29, aviation gasoline was stored in 13 USTs and one AST. At the old naval exchange gas station near Building 31, four former tanks and piping were potential sources of gasoline contamination in soils. All of the above USTs have been removed. VOC contamination from the MEW site also affects the soils at Site 9. Contamination may have come from either Navy or MEW sources.||Soil: VOCs and SVOCs were detected below ATSDR CVs. TPH (as gasoline) was detected above RBSLs, at a maximum concentration of 2,100 ppm.||Phase I testing of an air sparge/soil vapor extraction system has been completed. In addition, a pump-and-treat system has been installed at Site 9 as part of the MEW groundwater remediation program. The Navy is awaiting further evaluation using risk-based screening level guidance from the State of California.||No past, present, or future public health hazards exist. Incidental contact with contamination in the past is unlikely to have posed a health hazard. Remediation will prevent any future health hazard.|
|(12) Fire Fighting Training Area||This site consists of a bermed pit containing a mockup of a plane and a 5000-gallon above-ground fuel tank north of the pit. From the 1950s to 1987, the target plane was periodically covered with waste fuel from the tank and ignited. Fire crews extinguished the flames with water and/or fire-fighting chemicals.||Soil: Soils with elevated levels of TPH
were excavated during 1993. Post-excavation testing found TPH concentrations
Soil Gas: VOCs were detected during Phase I sampling. The area in which they were found was excavated in 1993.
|5,500 cubic yards of soil were excavated in 1993; this soil was treated to reduce TPH levels to below cleanup goals, and backfilled. Some contaminated soil could not be excavated because of overlying roads and runways. The Navy is awaiting further evaluation using risk-based screening level guidance from the State of California.|
|(14-South) Abandoned Tanks 19 and 20||Tanks 19 and 20, located at the corner of Macon Road and the South Gate exit, were 5,000-gallon tanks used to store unleaded vehicle fuel. Both tanks were removed prior to a 1987 investigation, which found petroleum hydrocarbon contamination in the groundwater.||Soil: Soil contamination is primarily
confined to the saturated soils within the A1 aquifer zone. TPH in this
zone exceeded RBSLs, with a maximum of TPH (purgeable as gasoline) at 1,300
Groundwater: Groundwater in the A1 aquifer is contaminated by TPH, with a maximum concentration of 42,000 ppb TPH (purgeable as other compounds).
|A recirculating in-situ treatment (RIST) system went into operation in August 1995; this pilot-test system is scheduled to operate for 3 years. The Navy is awaiting further evaluation using risk-based screening level guidance from the State of California.||No apparent past, present, or future public health hazards exist, because of a lack of significant exposure. Incidental contact with contamination is unlikely to pose a health hazard. Groundwater in the shallow aquifers is not used for any purpose.|
|(15) Eight Sumps and Oil/Water Separators, and One Tank||Site 15 consists of eight sumps and oil/water separators and one tank, which are distributed throughout MFA. One sump is active (Sump 59); Tank 54 and Sumps 25, 42, 58, and 64 have been removed. Sump 63 is an inactive catch basin for the ground support equipment area steam cleaning. Sump 130 is a sewer manhole/sump located near Building 575, a battery locker.||Soil and Groundwater:
Tank 54: VOCs were found at low levels (below CVs) in soil; no groundwater contamination was found.
Sump 58: TPH (purgeable as gasoline) was detected above RBSLs in soil (740 ppm) and was found in groundwater (250 ppb).
Sumps 59, 63, 64, 130: No TPH was found above RBSLs.
|Sumps 25, 42, and 62 are affected by the MEW ROD.
Sumps 59, 63, and 130 were recommended for elimination from the petroleum sites program because no contamination above cleanup levels was found to be associated with them.
|No apparent past, present, or future public health hazards exist, because of a lack of significant exposure. Incidental contact with contamination is unlikely to pose a health hazard. Groundwater in the shallow aquifers is not used for any purpose.|
|(19) Leaking tanks 2, 14, 43, 53||Tank 2 was installed in 1979 and had a capacity of 2,000 gallons. It received hazardous wastes from the Power Plant Shop in Hangar 3, including oils, hydraulic fluids, MEK (methyl ethyl ketone), JP fuels, B&B cleaner, PD-680 solvent, toluene, and Stoddard solvent. Tank 43, installed in 1979, was a 200-gallon hazardous waste tank for Hangar 3 that contained waste oils, solvents, waste fuel, MEK, PD-680 solvent, paint waste, and battery acids. Tank 14 was a 1700-gallon standby diesel tank for Building 158. Tank 53 was a 500-gallon unleaded gasoline tank for use at the golf course physical plant. All tanks were removed by the Navy in June 1990.||Soil and Groundwater:
Tank 2: VOCs and SVOCs were detected below CVs in soil. TPH was detected below RBSLs in soil.
Tank 14: No VOCs or SVOCs were detected in soil, except for a very low concentration of toluene (below CV) in one sample. TPH was detected (below RBSLs) in one localized area, which will be excavated before closure.
Tank 43: VOCs and SVOCs were detected below CVs in soil. VOCs detected in groundwater are discussed in the OU5 section. TPH was detected below RBSLs in soil. TPH was detected in groundwater: extractable as kerosene (99,000 ppb) and purgeable as other light components (1,900 ppb).
Tank 53: VOCs were detected below CVs in soil, but above CVs in groundwater. No SVOCs were detected. TPH (purgeable as gasoline) was detected above RBSLs in soil (1,600 ppm).
|Corrective measures are recommended for soil and groundwater
in the areas of Tanks 2 and 43, and for soil at Tank 53.
No further action has been recommended for Tank 14.
|No past, present, or future public health hazards exist, because of a lack of significant exposure. Incidental contact with contamination is unlikely to pose a health hazard. Groundwater in the shallow aquifers is not used for any purpose.|
OU6 (Wetlands, Stormwater Retention Ponds, and Storm Channels)
|Wetlands, Stormwater Retention Ponds, Storm Channels||Possible sources of contamination:
Sites 1, 11, and 15; regional groundwater plume; and horizontal conduits. See descriptions for individual sites (above and below).
|Soil and Sediment: VOCs and SVOCs were
detected below CVs. TPH (extractable as diesel) was detected below RBSLs.
The following pesticides were detected above CVs: aldrin in the Northern
Channel (0.6 ppm); dieldrin in the Northern Channel, along Lindbergh Avenue
and in the wetlands (8.5 ppm); and chlordane along Lindbergh Avenue (6.3
ppm total chlordane). PCBs were detected above their CV: Aroclor-1254 in
the wetlands and the Northern Channel (59.9 ppm); Aroclor-1260 in the wetlands
and the Northern Channel (33 ppm).
Surface Water: Three VOCs were detected below CVs. No SVOCs or pesticides were detected in OU6 surface water. Aroclor-1254 was detected above its CV (1.5 ppb) in the Eastern Diked Marsh.
|Lindbergh Avenue Ditch has been remediated by NASA. (A
completion report was issued in March 1997.) Contaminated sediments and
soils were removed and disposed of off-site. A below-grade storm sewer was
constructed to carry stormwater in place of the ditch.
The ROD for remediation of sediments in other areas is pending.
|No apparent past, present, or future public health hazards exist, because of a lack of significant exposure. It is unlikely that exposure to site-related contaminants occurred in the past at levels that would pose a health hazard. Lindbergh Avenue Ditch has been remediated and no longer poses a hazard. The Northern Channel is inaccessible because it is fenced off from MFA. The stormwater retention ponds are not used by humans; the Eastern Diked Marsh area is rarely used (PRC, 1996a).|
|(20) Zook Road Fuel Spill||Until 1982, ASTs located north of the present fire station were used to store aircraft fuel; fuel from these tanks was periodically spilled onto the ground and would accumulate in low areas next to the runways, taxiways, and Zook Road.||Soil: VOCs and SVOCs were detected below
ATSDR CVs. TPH (extractable as kerosene) was detected above RBSLs during
Phase I sampling (100,000 ppm). TPH extractable was below RBSLs during Phase
II sampling, but TPH purgeable was found above RBSLs (1,200 ppm).
Groundwater: The following VOCs were detected above CVs: 1,1-DCE (2 ppb), benzene (1 ppb), and vinyl chloride (30 ppb). These contaminants may be from the site or from the regional plume. No SVOCs were detected. TPH extractable as diesel was detected at an estimated concentration of 1,500 ppb.
|This site will be closed in a manner similar to the petroleum sites following Regional Water Quality Control Board (RWQCB) guidance.||No past, present, or future public health hazards exist. Incidental contact with contamination in the past is unlikely to have posed a health hazard. Any contamination with the potential to pose a future public health hazard will be remediated. Groundwater in the shallow aquifers is not used for any purpose.|
|(21) Patrol Road Ditch||Patrol Road Ditch carries some of the surface stormwater flow from the eastern side of MFA, including the Fuel Farm. In addition, Patrol Road Ditch was used for disposal of waste fluids, including motor oil, transmission fluid, and hydraulic fluid.||Soil: VOCs, SVOCs, and pesticides were detected below CVs. No PCBs were detected.||No action.||No past, present, or future public health hazards exist at this site. Soil contaminants were detected at levels that do not pose a health hazard based on current and likely future use.|
|(22) Golf Course Landfill 2||Golf Course Landfill 2 is located on the northeastern corner of the golf course. It received wastes, probably similar to those at Sites 1 and 2, from the 1940s through the 1960s. By 1970, the site had been revegetated and had become part of the golf course.||Soil Gas: No VOCs were detected at the
surface, and methane was not found to be migrating beyond landfill boundaries.
Soil: VOCs, SVOCs, and PCBs were detected below CVs. TPH was detected below RBSLs. The pesticide dieldrin was detected above its CV (0.18 ppm). Some radioactivity was detected during Phase I sampling, but reanalysis of the sample and the area indicated that the initial detection had been incorrectly high and that the levels found at the site are attributable to decay of naturally occurring elements.
Groundwater: VOCs were detected below CVs. One SVOC, n-nitrosodiphenylamine, was detected above its CV, at a maximum of 22 ppb. TPH (extractable as other heavy components) was detected (10,000 ppb); TPH (purgeable as other light components) was detected (560 ppb). No pesticides or PCBs were detected.
|A draft feasibility study (FS) report for Site 22 was issued in January 1998. The remedial alternative which received the highest score in the FS evaluation included the following elements: access restrictions, a biotic barrier, and groundwater and gas monitoring. Additional field work was performed in April 1998 to determine the landfill depths and boundaries more accurately and to collect additional groundwater samples. The data will be used to refine the feasibility study.||No past, present, or future public health hazards exist. It is unlikely that exposure to site-related contaminants occurred in the past at levels that would pose a health hazard. Groundwater at the site has not been used in the past and is unlikely to be used in the future. Access to the site will be restricted in the future.|
|(23) Golf Course Landfill 3||Golf Course Landfill 3 is located on approximately 2 acres just south of the northern weapons bunker area. Debris such as grass clippings, soil, concrete, and airplane parts were apparently dumped in this area over an unknown period of time. Magnetometer surveys did not indicate the presence of significant quantities of metallic materials.||Soil: Toluene, which was detected below its CV, was the only VOC found. SVOCs and TPH were detected in surface soil; levels were consistent with the presence of asphalt in the disposed debris. Pesticides were found in at least one surface soil sample but were attributed to golf course maintenance.||No action.||No past, present, or future public health hazards exist. Hazardous materials were not disposed of in this landfill.|
|(24) Active Petroleum Sites||Site 24 includes the Hangar 1 fuel pits, the high-speed fuel hydrants, and the Fuel Pier. The Hangar 1 Fuel Pits, in the Hangar 1 floor, held aviation gasoline but are no longer used. The high-speed fuel hydrants, located northwest of Hangars 2 and 3, are used to fuel and defuel aircraft. The fuel pier is located at the end of a manmade peninsula that extends north from the northeastern corner of MFA to Guadalupe Slough.||Soil: TPH was detected below RBSLs in
soil at the high-speed fuel hydrants and at the Fuel Pier. The only significant
soil contamination at Hangar 1 was related to the regional VOC plume.
Groundwater: TPH extractable as JP-5 was detected in groundwater at the high-speed fuel hydrants (21,000 ppb). The only significant groundwater contamination at Hangar 1 was related to the regional VOC plume.
|Contaminated soil was removed at the high-speed fuel hydrants.||No past, present, or future public health hazards exist. Incidental contact with contamination is unlikely to pose a health hazard. Groundwater in the shallow aquifers is not used for any purpose.|
|Weapons Storage Bunkers||The weapons bunkers, located in two secured areas near the golf course, are used to store high explosives. A diesel UST and a 55-gallon diesel AST located at the northern weapons bunker have been removed.||Soil: No contamination was found other than low levels of common laboratory contaminants.||No further action.||No past, present, or future public health hazards exist. No contamination exists at this site.|
|Industrial Wastewater Flux Ponds||These holding ponds, with a combined capacity of about 2 million gallons, were opened in 1978. They received wastewater from the aircraft washrack drains and ground support equipment washrack drains. The ponds were taken out of service in January 1994 and were removed in 1995.||Soil: No SVOCs or TPH were detected. Very low levels (below CVs) of PCE and TCE were found.||No further action.||No past, present, or future public health hazards exist. Contaminants were detected at levels that do not pose a health hazard. The site has been fully remediated.|
|Potential Runway Wetland||This site, located between the southern ends of the runways, is assumed to be the result of an improperly abandoned agricultural well.||Contamination is not an issue at this site.||In 1997, the well was located and destroyed.||No public health hazards exist at this site because no hazardous materials were disposed of at this site.|
Sources: IT, 1991, 1992a, b; PRC, 1993, 1994a, 1995, 1996a, b, 1997; Tetra Tech, 1998a, b; Navy/EPA, 1994, 1996, 1997.
1. See Appendix B for an explanation of CVs.
2. Metals data were not presented for many sites in Moffett Field summary documents, for the following reasons: (1) the chemicals thought to be released by Navy activities were mostly organic compounds; (2) levels of metals found were usually below background levels for the area; and (3) spatial analyses of metals on the base revealed no significant patterns of occurrence. These factors led to a conclusion that metals found during the MFA site investigation were generally naturally occurring.
3. Because ATSDR does not have comparison values for TPH, TPH detections are discussed in light of the evaluation method specified for MFA petroleum sites (see note under Petroleum Sites section of table).
4. Maximum contaminant concentrations are presented parenthetically.
|Moffett NAS||Mountain View||Sunnyvale|
|Persons per square mile||662||5,606||5,354|
|% American Indian, Eskimo, or Aleut||0.7||0.6||0.5|
|% Asian or Pacific Islander||5.4||14.7||19.3|
|% Other races||3.0||6.9||5.1|
|% Hispanic origin||6.0||16.0||13.2|
|% Under age 10||11.2||11.6||11.7|
|% Age 65 and older||0.0||9.8||10.4|
Source: Census of Population and Housing, 1990: Summary Tape File 1A (California) [machine-readable data files]. Prepared by the Bureau of the Census. Washington, DC: The Bureau [producer and distributor], 1991.
|Moffett NAS||Mountain View||Sunnyvale|
|166||29, 990||48, 296|
|Persons per household||3.83||2.23||2.42|
% Households owner-occupied
% Households renter-occupied
% Households mobile homes
% Persons in group quarters
Median rent paid,
* A household is an occupied housing unit, but does not include group quarters such as military barracks, prisons, and college dormitories.
Source: Census of Population and Housing, 1990: Summary Tape File 1A (California) [machine-readable data files]. Prepared by the Bureau of the Census. Washington, DC: The Bureau [producer and distributor], 1991.
MFA No Apparent Public Health Hazard Situations
|PATHWAY NAME||POTENTIAL EXPOSURE PATHWAY ELEMENTS||COMMENTS|
|SOURCE OF CONTAMINATION||ENVIRONMENTAL MEDIA||POINT OF EXPOSURE||ROUTE OF EXPOSURE||POTENTIALLY EXPOSED POPULATION||EXPOSURE PERIOD EVALUATED|
|Groundwater||Regional plume from MEW Superfund site; solvents used at MFA||Groundwater||Wells||Ingestion,
|Past: Wells at MFA were screened in the
deep aquifer, which is not contaminated.
Current: The one active well at MFA is screened in the deep aquifer and is not used for drinking water.
Future: Contamination is not expected to migrate to the deep aquifer. Wells at MFA are unlikely to be used to provide drinking water.
|Past/Current/Future: Contamination from MFA has not migrated offsite and is unlikely to in the future.|
|Soil||Waste disposal, leaking tanks, and various activities at MFA||Soil||Onsite surface soil||Dermal,
|Residents and employees at MFA; visitors to MFA||Past
|Past/Current: Infrequent and incidental
contact with contamination is unlikely to pose a health hazard.
Future: Areas posing a potential health hazard for long-term, frequent exposure will be remediated.
|Surface Water and Sediment||Various activities at MFA||Surface water
|Onsite surface water and sediment||Dermal,
|Residents and employees at MFA; visitors to MFA||Past
|Past: It is unlikely that exposure to
site-related contaminants occurred in the past at levels that would pose
a health hazard.
Current/Future: Lindbergh Avenue Ditch has been remediated. Remaining contamination is located in infrequently accessed areas.
- Background Level:
- A typical or average level of a chemical in the environment. Background often refers to naturally occurring or uncontaminated levels.
- The Comprehensive Environmental Response, Compensation, and Liability Act of 1980, also known as Superfund. This is the legislation that created ATSDR.
- Comparison Values:
- Estimated contaminant concentrations in specific media that are not likely to cause adverse health effects, given a standard daily ingestion rate and standard body weight. The comparison values are calculated from the scientific literature available on exposure and health effects.
- The amount of one substance dissolved or contained in a given amount of another. For example, sea water contains a higher concentration of salt than fresh water.
- Any substance or material that enters a system (the environment, human body, food, etc.) where it is not normally found.
- Referring to the skin. Dermal absorption means absorption through the skin.
- Environmental Contamination:
- The presence of hazardous substances in the environment. From the public health perspective, environmental contamination is addressed when it potentially affects the health and quality of life of people living and working near the contamination.
- Contact with a chemical by swallowing, by breathing, or by direct contact (such as through the skin or eyes). Exposure may be short term (acute) or long term (chronic).
- A source of risk that does not necessarily imply potential for occurrence. A hazard produces risk only if an exposure pathway exists, and if exposures create the possibility of adverse consequences.
- Health Outcome Data:
- A major source of data for public health assessments. The identification, review, and evaluation of health outcome parameters are interactive processes involving the health assessors, data source generators, and the local community. Health outcome data are community specific and may be derived from databases at the local, state, and national levels, as well as from data collected by private health care organizations and professional institutions and associations. Databases to be considered include morbidity and mortality data, birth statistics, medical records, tumor and disease registries, surveillance data, and previously conducted health studies.
- Swallowing (such as eating or drinking). Chemicals can get in or on food, drink, utensils, cigarettes, or hands where they can be ingested. After ingestion, chemicals can be absorbed into the blood and distributed throughout the body.
- Breathing. Exposure may occur from inhaling contaminants because they can be deposited in the lungs, taken into the blood, or both.
- Soil, water, air, plants, animals, or any other parts of the environment that can contain contaminants.
- All the chemical reactions that enable the body to work. For example, food is metabolized (chemically changed) to supply the body with energy. Chemicals can be metabolized and made either more or less harmful by the body.
- National Priorities List (NPL):
- The Environmental Protection Agency's (EPA) listing of sites that have undergone preliminary assessment and site inspection to determine which locations pose immediate threat to persons living or working near the release. These sites are most in need of cleanup.
- No Public Health Hazard:
- Sites for which data indicate no current or past exposure or no potential for exposure and therefore no health hazard.
- An area of chemicals in a particular medium, such as air or groundwater, moving away from its source in a long band or column. A plume can be a column of smoke from a chimney or chemicals moving with groundwater.
- Potentially Exposed:
- The condition where valid information, usually analytical environmental data, indicates the presence of contaminant(s) of a public health concern in one or more environmental media contacting humans (i.e., air, drinking water, soil, food chain, surface water), and there is evidence that some of those persons have an identified route(s) of exposure (i.e., drinking contaminated water, breathing contaminated air, having contact with contaminated soil, or eating contaminated food).
- Public Comment:
- An opportunity for the general public to comment on Agency findings or proposed activities. The public health assessment process, for example, includes the opportunity for public comment as the last step in the draft phase. The purposes of this activity are to 1) provide the public, particularly the community associated with a site, the opportunity to comment on the public health findings contained in the public health assessment, 2) evaluate whether the community health concerns have been adequately addressed, and 3) provide ATSDR with additional information.
- Public Health Action:
- Designed to prevent exposures and/or to mitigate or prevent adverse health effects in populations living near hazardous waste sites or releases. Public health actions can be identified from information developed in public health advisories, public health assessments, and health consultations. These actions include recommending the dissociation (separation) of individuals from exposures (for example, by providing an alternative water supply), conducting biologic indicators of exposure studies to assess exposure, and providing health education for health care providers and community members.
- Public Health Assessment:
- The evaluation of data and information on the release of hazardous substances into the environment in order to assess any current or future impact on public health, develop health advisories or other recommendations, and identify studies or actions needed to evaluate and mitigate or prevent human health effects; also, the document resulting from that evaluation.
- Route of Exposure:
- The way in which a person may contact a chemical substance. For example, drinking (ingestion) and bathing (skin contact) are two different routes of exposure to contaminants that may be found in water.
- Another name for the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), which created ATSDR.
- Volatile Organic Compounds (VOCs):
- Substances containing carbon and different proportions of other elements such as hydrogen, oxygen, fluorine, chlorine, bromine, sulfur, or nitrogen; these substances easily become vapors or gases. A significant number of the VOCs are commonly used as solvents (paint thinners, lacquer thinner, degreasers, and dry cleaning fluids).
ATSDR comparison values are media-specific concentrations that are considered to be "safe" under default conditions of exposure. They are used as screening values in the preliminary identification of "contaminants of concern" at a site. The latter is, perhaps, an unfortunate term since the word "concern" may be misinterpreted as an implication of "hazard". As ATSDR uses the phrase, however, a "contaminant of concern" is merely a site-specific chemical substance that the health assessor has selected for further evaluation of potential health effects.
Generally, a chemical is selected as a contaminant of concern because its maximum concentration in air, water, or soil at the site exceeds one of ATSDR's comparison values. However, it cannot be emphasized strongly enough that comparison values are not thresholds of toxicity. While concentrations at or below the relevant comparison value may reasonably be considered safe, it does not automatically follow that any environmental concentration that exceeds a comparison value would be expected to produce adverse health effects. Indeed, the whole purpose behind highly conservative, health-based standards and guidelines is to enable health professionals to recognize and resolve potential public health problems before they become actual health hazards. The probability that adverse health outcomes will actually occur as a result of exposure to environmental contaminants depends on site specific conditions and individual lifestyle and genetic factors that affect the route, magnitude, and duration of actual exposure, and not on environmental concentrations alone.
Screening values based on non-cancer effects are obtained by dividing NOAELs or LOAELs determined in animal or (less often) human studies by cumulative safety margins (variously called safety factors, uncertainty factors, and modifying factors) that typically range from 10 to 1,000 or more. By contrast, cancer-based screening values are usually derived by linear extrapolation from animal data obtained at high doses, because human cancer incidence data for very low levels of exposure simply do not exist, and probably never will. In neither case can the resulting screening values (i.e., EMEGs or CREGs) be used to make realistic predictions of health risk associated with low-level exposures in humans.
Listed and described below are the various comparison values that ATSDR uses to select chemicals for further evaluation, along with the abbreviations for the most common units of measure.
|CREG =||Cancer Risk Evaluation Guides|
|EMEG =||Environmental Media Evaluation Guides|
|EPA =||Environmental Protection Agency|
|kg =||kilogram (1,000 grams)|
|m3 =||cubic meter (used in reference to a volume of air equal to 1,000 liters)|
|MCL =||Maximum Contaminant Level|
|mg =||milligram (0.001 grams)|
|MRL =||Minimal Risk Level|
|ppb =||parts per billion, e.g., µg/L or µg/kg|
|ppm =||parts per million, e.g., mg/L or mg/kg|
|RfD =||Reference Dose|
|RMEG =||Reference Dose Media Evaluation Guide|
|µg =||microgram (0.000001 grams)|
Cancer Risk Evaluation Guides (CREGs) are estimated contaminant concentrations in water, soil, or air that would be expected to cause no more than one excess cancer in a million persons exposed over a 70-year lifetime according to EPA estimates. As ATSDR's most conservative comparison value, the CREG merits special attention. Note that this does not mean that exposures equivalent to the CREG are actually expected to cause one excess cancer in a million persons exposed over a lifetime. Nor does it mean that every person in an exposed population of one million has a 1-in-a-million chance of developing cancer from the specified exposure. Although ATSDR CREGs continue to be useful devices for screening carcinogenic substances at a site, they cannot be used to predict cancer incidence rates at a site. Furthermore, the exposure assumptions on which EPA's cancer risk estimates and ATSDR's CREGs are based (i.e., essentially lifetime exposure) seldom apply at contaminated sites.
Environmental Protection Agency (EPA) values are similar to ATSDR's CREGs and EMEGs in that they are risk-based concentrations derived for carcinogens and non-carcinogens from RfDs and Cancer Slope Factors, respectively, assuming default values for body weight, exposure duration and frequency, etc. Unlike ATSDR values, however, they are available for fish, as well as for water, soil, and air.
Environmental Media Evaluation Guides (EMEGs) are concentrations of a contaminant in water, soil, or air that are unlikely to be associated with any appreciable risk of deleterious noncancer effects over a specified duration of exposure. EMEGs are derived from ATSDR minimal risk levels by factoring in default body weights and ingestion rates. Separate EMEGS are computed for acute (< 14 days), intermediate (15-364 days), and chronic (> 365 days) exposures.
Maximum Contaminant Levels (MCLs) represent contaminant concentrations in drinking water that EPA deems protective of public health (considering the availability and economics of water treatment technology) over a lifetime (70 years) at an exposure rate of 2 liters of water per day.
Minimal Risk Levels (MRL) are estimates of daily human exposure to a chemical (i.e., doses expressed in mg/kg/day) that are unlikely to be associated with any appreciable risk of deleterious noncancer effects over a specified duration of exposure. MRLs are derived for acute (< 14 days), intermediate (15-364 days), and chronic (> 365 days) exposures. MRLs are published in ATSDR's Toxicological Profiles for specific chemicals.
(EPA's) Reference Dose (RfD) is an estimate of the daily exposure to a contaminant unlikely to cause noncarcinogenic adverse health effects over a lifetime of exposure. Like ATSDR's MRL, EPA's RfD is a dose expressed in mg/kg/day.
Reference Dose Media Evaluation Guide (RMEG) is the concentration of a contaminant in air, water or soil that corresponds to EPA's RfD or RfC for that contaminant when default values for body weight and intake rates are taken into account.
COMPARISON VALUE REFERENCES
- Agency for Toxic Substances and Disease Registry. Health Assessment Guidance Manual. Atlanta: ATSDR, October 1992.
- National Institute for Occupational Safety and Health. Pocket Guide to Chemical Hazards. Washington D.C.: Department of Health Human Services, June 1994.