PRELIMINARY PUBLIC HEALTH ASSESSMENT
PREWITT ABANDONED REFINERY
PREWITT, MCKINLEY COUNTY, NEW MEXICO
The Prewitt Abandoned Refinery, an Update 7 site proposed for the National Priorities List, is located about one-half mile west of the Prewitt Post Office, McKinley County, New Mexico. The site consists of two separate parcels, one consisting of 68.2 acres and the other consisting of 6.8 acres. The site was operated as a crude oil refinery from 1939 to 1957 and is now abandoned. Although the site is located in rural area, several off-site residences are located within 1,500 feet of the site. Benzene, toluene, xylene, polynuclear aromatic hydrocarbons, chromium, and lead were detected in on-site soil samples and on-site and off-site groundwater samples. Site-related contaminants have also been detected in off-site private wells. The most likely pathways for contaminants to migrate from on-site to off-site areas include those associated with groundwater and soil. Human exposure to site contaminants is most likely to occur via ingestion and inhalation of, or dermal contact with, contaminated groundwater and soil. The site is of potential public health concern because of elevated levels of contaminants in groundwater and soil.
The Prewitt Abandoned Refinery (PAR), consisting of 75 acreslocated in a rural area one-half mile west of the Prewitt PostOffice, McKinley County, New Mexico, is an Update 7 site proposedfor the National Priorities List (NPL). The PAR site consists oftwo separate parcels of land (see Figures 1 and 2). The largestparcel includes 68.2 acres located just south of U.S. Route 66. The remaining section of the site includes 6.8 acres of landlocated on the north side of Route 66 (directly across the roadfrom the larger portion of the site).
The largest parcel of the site was operated as a crude oil refinery from 1939 to 1957. The refinery had five major processes, including a crude distillation unit, a thermal cracking unit, a reforming unit, a polymer gasoline unit, and a caustic treatment unit. The primary products of the on-site oil-refining operation included gasoline, fuel oil, diesel fuel, and kerosene. Allegedly, while the refinery was operational, several spills of finished product (gasoline) occurred during the filling of railroad cars and on-site storage tanks. Railroad cars were filled in the northernmost section of the site; however, the on-site storage tanks apparently were located south of U.S. Route 66.
During operation of the refinery, sludges
from the on-siteAmerican Petroleum Institute (API) separator were placed intothree unlined surface impoundments located in the northwestcorner of the southern parcel of the site. Fluids from theseparator were drained directly onto the ground and formed areasof tar-like material. Other areas of petroleum-stained soil arescattered around both parcels of the site, but primarily in thesection north of U.S. Highway 66 along the railroad spur servingthe refinery. Area residents have reported that on-site storagetanks leaked.
In 1957, refinery operations at the PAR site were discontinued. According to aerial photographs the refinery equipment, including44 storage tanks, were removed sometime after October 1958. In1966, the Baca Chapter of the Navajo Nation purchased the PARsite.
The site was identified by the U.S. Environmental Protection Agency (EPA) because of a citizen's complaint. Site investigations have been conducted by the New Mexico Environmental Improvement Division (NMEID) and the EPA Region VI Field Investigation Team (FIT). In August 1984, the NMEID submitted a Hazardous Ranking Score (HRS) package to the EPA; however, the site did not rank high enough to be included on the NPL. As a result of additional investigations in 1985 and 1986, NMEID identified sludges from the API separator as a source of groundwater contaminants. In August 1986, a new HRS package was submitted to the EPA for reconsideration of the PAR site for listing on the NPL. The site was proposed for the NPL Update 7 on June 24, 1988, but had not been added to the NPL as of the date of this Preliminary Health Assessment.
A visit to the PAR site was conducted by Agency for Toxic Substances and Disease Registry (ATSDR) personnel on March 23, 1989. During the site visit it was noted that a house trailer had been moved onto the site and was being used as a residence. Although at the time of the site visit access to the site was unrestricted since that time the site has been fenced and the on-site house trailer removed from the site. Empty beverage containers scattered around the site indicated unauthorized site entry.
The site lies in a rural area of New Mexico. The nearestresidences (less than 10) are located immediately east of thenorthern portion of the site along Route 66. About 2,500 feetwest of the site lies the Kampgrounds of America (KOA)Campground, which serves as a recreational and camping area. South of the site lies Interstate 40, a four-lane highway. Withthe exception of several deteriorating building foundations onthe southern portion of the site, both portions are flat, barren,and arid with scattered shrubs and grasses. There are notsurface water impoundments in either portio of the site.
Other observations made during the site visit are discussed inappropriate sections of this Preliminary Health Assessment.
Staff from the Navajo Superfund Office (NSO) indicated that thetribal council had expressed concerns that the site be cleanedup, but they were not aware of specific health concerns by tribalmembers or nearby residents.
Several Navajo Reservation communities are adjacent to the PAR site, including the Baca, Haystack, Bluewater, and Casamero lake Chapters. The nearest residential area is located just east of the site and consists of six residences just east of the northern portion of the site along the north side of Route 66. Approximately 350 people reside within a 1-mile radius, with the largest portion of these residents living in the Baca Chapter community located just southwest of the site and Interstate 40. An estimated 1,200 people reside within 3 miles of the site.
A community well serving a reported 1,500 members of the BacaChapter of the Navajo Tribe is located adjacent to the site'swestern border. During their 2-hour-long site visit, ATSDR staffnoticed that water was used to fill up a total of four 55-gallondrums located in the beds of two pick-up trucks. A more accurateestimate of the number of residents using the community well isabout 350 (based on observations of well use and localdemographics). The on-site trailer and residents have beenrelocated to an off-site area since the March 23, 1989, sitevisit by ATSDR staff.
Six residences are located east of the site (although theresidence nearest the site has been abandoned and the wellserving this residence closed). The five occupied residencesrely on private wells for potable water.
The only commercial land use within 1 mile of the site consistsof a service station/small convenience store located 0.5 mileswest of the site along Interstate 40. The only industrial landuse within 1 mile of the site is the railroad line running northof the site.
Recreational land uses within the site area include a KOACampground located 2,500 feet west of the PAR site, and a rodeoarena located approximately 1 mile east of the site. There arenot surface water bodies within 1 mile of the site.
Only limited agricultural activity, consisting of the raising of sheep, was observed in the site area. Herds of sheep werelimited in size (less than 20) and were raised on Navajo triballands located south of the site. During the site visit, ATSDRstaff also noted that home gardens and crop-related agriculturalactivities were absent or of very small scale within a 1-mileradius of the site.
On-site wastes contain contaminants commonly associated withcrude oil refineries including lead, chromium, benzene, toluene,xylenes, and other hydrocarbons. Other on-site contaminants,including polynuclear aromatic hydrocarbons (PAHs), have beendetected in the on-site surface impoundments. Chlorinatedpesticides, reported to have been detected in soil samplescollected from surface impoundments in 1980 and 1984, may havebeen incorrectly identified. This error may have resultedbecause of the complex hydrocarbon matrix in the soil samples.
Results of preliminary groundwater monitoring of off-site privatewells in 1981 and 1983 showed that the water was contaminatedwith benzene and ethylbenzene. Results of groundwater monitoringin 1985 and 1986 identified additional groundwater contaminants,including toluene and xylene, and linked the groundwatercontamination to the API separator discharge. The highest levelsof groundwater contaminants were detected in the on-sitemonitoring wells screened in the alluvial aquifer and located inthe northeast quarter of the southern portion of the site. Contaminants were also detected in the monitoring wells screenedin the Chinle Aquifer and the San Andres/Glorieta Aquifer.
Off-site groundwater monitoring was limited to samples collectedfrom the private wells located west of the southern portion ofthe site and east of the northern portion of the site. Off-sitegroundwater contaminants were detected in a pair of off-siteresidential wells located east of the northern portion of thesite and in a railroad-owned well located northeast of the site. Contaminants were not detected in the Baca Chapter well.
The highest levels of soil and sediment contaminants weredetected in the soil samples collected from the northwest cornerof the southern portion of the site. Specific areas with thehighest levels of soil and sediment contaminants included theformer surface impoundments, drainageways from the impoundments,and the discharge drainageway for the API separator. Soil andsediment contaminants were also detected in the northern portionof the site, particularly in the culvert that serves as adrainageway for the site. Soil and sediment contamination at thesite appears to be limited to a relatively small portion of thesite (less than 5%).
|Contaminant||Maximum Concentration |
(Reported as parts per billion [ppb])
|Contaminant||Maximum Concentration |
(Reported as parts per billion [ppb])
|Benzo (b) fluoranthene||52,000|
|Contaminant||Maximum Concentration |
(Reported as parts per billion [ppb])
|Private Wells, 1985-1988|
|Contaminant||Maximum Concentration |
(Reported as parts per billion [ppb])
|Benzene (New Railroad Well)||680|
|Benzene (Residential Well)||69|
|Lead (Residential Well)||49|
Quality assurance and quality control procedures were used toensure the accuracy of the results of groundwater sampleanalyses. The conclusions contained in this report are based onthe data package supplied to ATSDR. The accuracy of theseconclusions is based on the reliability and comprehensiveness ofthe data contained in materials reviewed.
Initial sampling results showed numerous chlorinated pesticidesat the PAR site. Available site documents indicate pesticideswere never manufactured, used, or disposed of at the site, andthese compounds were probably incorrectly identified because ofthe oily matrix of the samples.
During ATSDR's site visit several on-site physical hazards,including empty storage tanks, building foundations, andconstruction debris, were noted. Empty beverage containers foundin various sections of the site during the March 1989 site visitindicated that unauthorized site entry occurred prior to theinstallation of the fence around the perimeter of the site. Sitetrespassers and remedial workers may come into contact with on-site physical hazards.
The site lies in an area with three water-bearing units,including an alluvial aquifer, an aquifer located in thesandstone unit comprising the middle portion of the ChinleFormation, and the San Andres Limestone/Glorieta SandstoneAquifer. During on-site investigations, groundwater wasencountered in on-site alluvium at a depth of 15 feet. Alluviumwithin site vicinity varies in thickness from zero (in areas ofoutcropping by the Chinle Formation) to about 20 feet. Thealluvium is underlain by the upper Chinle, comprised of siltstoneand mudstone, which usually acts as an aquitard. Although anaquitard lies between the upper and lower aquifers, contaminantsfrom the alluvial aquifer may migrate to the lower aquifersthrough the casings of several abandoned on-site wells. Within1.5 miles of the site no wells are known to be screened in thealluvial aquifer.
Wells drawing water from the aquifer located in the middleportion of the Chinle Formation typically are 180 to 210 feetdeep; however, the depths of these wells vary considerablybecause the Chinle Formation varies in thickness from 300 to1,000 feet. This is the predominant aquifer in use within thevicinity. The top of the aquifer seems to be well confined, andin most cases the aquifer appears to be under artesian pressure.
The San Andres Limestone/Glorieta Sandstone Aquifer is located atdepths in excess of 700 feet. Wells drawing from this aquifertypically range to depths of 750 to 790 feet. This aquifer isalso under artesian pressure.
Regionally, groundwater flow in the alluvium and the ChinleFormation is to the southeast; however, locally, groundwater inthe alluvial aquifer follows the topographic slope and flows tothe northeast. In the site vicinity, groundwater flow in theMiddle Chinle and the San Andres Limestone/Glorieta Sandstoneformations is to the northeast.
Locally, groundwater is used for residential, agricultural, andlimited industrial purposes. The Baca Chapter of the NavajoTribe draws water for domestic use from a well located adjacentto the western border of the site. The Baca Chapter well has aflow rate of 28 gallons per minute and a depth of 284 feet(Middle Chinel Formation). Private wells within 1 mile of thesite are used for the watering of livestock.
Five residences located just east of the site also rely onprivate wells for potable water. The residences nearest the sitehave been abandoned and the residential well closed. Groundwatercontamination was detected in a 187-foot-deep private welllocated about 100 feet east of the site.
Results of electromagnetic terrain conductivity surveys conductedat the PAR site indicated a shallow groundwater contaminant plumenorth of the API separator discharge area. Results of a seismicrefraction survey of the site indicated the presence of a faultrunning from the southeast to the northwest, through thenortheastern corner of the site, and the possible presence of asecond fault 800 feet east of the previously identified fault. These faults may influence the flow of groundwater and themigration of contaminants from the site.
2. Surface Water
The site lies in a flat area that gently slopes to the north and east. Surface water runoff from the site flows to the northeast, through two culverts (an east or west culvert) running under U.S. Highway 66, to the Mitchell Draw Arroyo located 0.5 miles north of the site. This arroyo is the major drainage course in the site area and drains to the southeast toward the Rio San Jose Valley. The Mitchell Draw Arroyo is an intermittent stream that flows primarily during periods of precipitation. There are no year-round surface water bodies on-site or within 2 miles of the site.
Site conditions, including the sandy nature of the soil, the flattopography, and the distance to surface water bodies, areexpected to minimize the site's impact on the water quality ofthe nearest bodies of surface water.
3. Soil and Sediment
On-site soil and sediment contaminants may be transported to off-site areas via water or wind erosion. The site lies in anarid region with infrequent but heavy downpours. During heavyrains, storm water runoff may transport dissolved contaminantsand contaminated soils and sediments to off-site areas. Monitoring results for surface soil and sediment indicate thatcontaminants are migrating from the waste impoundments and formerproduct storage tank areas toward the on-site east and westculverts. Because of sparse vegetation, wind erosion may occurat the site during dry conditions.
Air monitoring was not conducted during preliminary siteinvestigations. Soil- and groundwater-associated contaminantsmay become airborne through volatilization or the release offugitive dusts. High rates of volatilization of soil andsediment contaminants to ambient air are unlikely at the presentbecause the site has been inactive for about 50 years. If soil-excavating activities are conducted at the site, substantialvolatilization of wastes in soil and sediments and the release ofdusts may occur.
5. Contaminated Food-Chain Entities
Contaminants from groundwater, soil, and sediments maybioaccumulate in food chain-entities, such as crops and animals. Several private wells within 1 mile of the site area are used forthe watering of livestock. Livestock watered with contaminatedgroundwater may bioaccumulate contaminants. The site is notlikely to be used as a livestock grazing area because of thesite's sparse vegetation.
1. Groundwater-Associated Pathways
Human exposure via ingestion or inhalation of, dermal contact with, groundwater contaminants may result from use of contaminated groundwater for domestic, industrial, and agricultural purposes. Contaminants at levels of public health concern were detected in on-site monitoring wells and in three off-site private wells located east of the site. The private wells included a pair of residential wells (one serving a residence that was abandoned in 1985) and a well owned by the railroad. Groundwater contaminants detected in on-site and off-site groundwater included hydrocarbons and metals commonly associated with refined petroleum products such as gasoline. Groundwater contaminants were not detected in samples collected from groundwater monitoring wells located in the southwestern portion of the site.
2. Surface-Water-Associated Pathways
No surface water bodies are within 2 miles of the site;therefore, this medium is not of public health importance for thePAR site.
3. Soil- and Sediment-Associated Pathways
Since the March 23, 1989, site visit by ATSDR staff, the site hasbeen fenced and access to the site is restricted; therefore, sitetrespass by unauthorized personnel and contact with contaminatedsoil and sediments from the waste impoundments are unlikely.
4. Food-Chain-Associated Pathways
Another potential pathway for human exposure is through the ingestion of food-chain entities that may bioaccumulate site-related contaminants. Since no crop- or livestock-raising activities re conducted on-site or immediately adjacent to the site, this pathway of human exposure is not expected to be of importance.
5. Airborne-Associated Pathways
Another potential pathway for human exposure is site-relatedcontaminants is through the inhalation of airborne contaminants. During soil- and sediment-disturbing activities, levels ofairborne volatile organic chemicals and dusts may be of publichealth concern to on-site workers and nearby residents.
On the basis of preliminary sampling results, the PAR site is ofpotential public health concern because of on-site soil andsediment contamination and on-site and off-site groundwatercontamination.
In recent groundwater monitoring of private wells northeast ofthe site, benzene and lead were detected in three wells,including one abandoned well, at levels near or exceeding MaximumContaminant Levels (MCLs) established by the Safe Drinking WaterAct.
Soil and Sediment
Although a relatively small portion of the site's surface appearsto be contaminated, contaminant levels in these ares aresufficiently high to be of public health concern. Thepossibility of human contact with site contaminants wouldincrease significantly during any on-site remedial activitiesthat include soil-disturbing activities.
A brief discussion of the identified site contaminants of publichealth concern follows.
Human exposure to benzene at the PAR site may occur through theingestion, inhalation, or dermal absorption of contaminatedgroundwater. Benzene is classified as a human carcinogen via theinhalation route. The EPA established a drinking water MaximumContaminant Level Goal (MCLG) for benzene of zero, with a currentMCL of 5 ppb. Benzene was detected in on-site monitoring wellsand three off-site private wells at levels in excess of the MCL.
Use of groundwater contaminated with benzene for householdpurposes, such as bathing or cooking may result in thevolatilization of benzene and inhalation exposures to thehousehold residents. Short-term exposures (less than 14 days) tobenzene at levels as low as 10 parts per million (ppm) may affectthe immune system. Benzene exposure may also affect the centralnervous system (CNS), causing drowsiness, dizziness, headaches,and vertigo (4).
Human exposure to benzo(b)fluoranthene at the PAR site may occurthrough dermal contact with contaminated soils or sediments, orthrough the ingestion and inhalation of contaminated soil andsediments. Although no data are available on the health effectsof human exposure, results of studies in laboratory animalsindicate that long-term exposure to benzo(b)fluoranthene causescancer in laboratory animals when applied dermally over thelifetime of the animal. On the basis of results of animalstudies, benzo(b)fluoranthene is also expected to cause cancer ininhalation and ingestion exposures to benzo(b)fluoranthene aswell as short-term dermal exposures are not known (5).
The three major forms of chromium all differ in their effects;the two most common forms are discussed in this section. Chromium at the PAR site is probably present in the chromium(III) form, because this is the form associated with petroleumproducts. Chromium (III) is an essential dietary element and acommon component in many foods. The other common form ofchromium is chromium (VI), the form associated with chromatemanufacturing and is not expected to be found at the PAR site.
Human exposure to chromium at the PAR site may occur as a resultof ingestion of contaminated soil, inhalation of airborne-contaminated dusts, or dermal absorption of soilcontaminants. Long-term oral exposure in animals to low levelsof chromium has not resulted in harmful effects. From availablemonitoring results, acute high-dose exposure to chromium at thePAR site is not likely by any route. Dermal exposure to eitherform of chromium can result in chromium sensitivity.
The EPA has classified chromium (VI) as a human carcinogen by theinhalation route. Thus, the inhalation of chromium-contaminateddust may increase the potential for contracting cancer. There isno evidence that chromium (III) or chromium (VI) is carcinogenicvia the oral route of exposure (6).
Human exposure to chrysene at the PAR site may occur throughdermal contact with contaminated soil and sediments or throughingestion and inhalation of contaminated soil and sediments. Although no data are available on the health effects of humanexposures to chrysene, results of studies in laboratory animalsindicate that long-term dermal exposure to chrysene causescancer. From these animal studies, humans experiencing long-termdermal exposures to chrysene are likely to develop cancer. Noanimal or human data are available on the health effects ofinhalation or ingestion exposures to chrysene or short-termdermal exposures (7).
Human exposure to lead at the PAR site may occur through theingestion of contaminated groundwater or through the ingestion orinhalation of contaminated soil. Lead was detected at a level of49 ppb in samples collected from an off-site residential well. This level exceeds EPA's drinking water MCL of 20 ppb and theproposed MCL of 5 ppb. Inhalation exposure to lead-contaminateddusts may occur during any on-site soil-excavating activities,such as may occur during site remediation.
Ingestion of lead-contaminated soil is another important humanexposure pathway at the PAR site. Passive ingestion of soiloccurs during work and recreational activities. Young childrenare prone to ingest dirt either directly (pica) or through hand-to-mouth activities. Children are especially susceptible tohealth effects of lead exposure. As mentioned in the Site VisitSection of this report, empty beverage containers at the siteindicate past site trespass; however, the installation of a fencearound the perimeter of the site should help reduce sitetrespass.
Low levels of lead exposure may cause decreased growth andreduced intelligence quotient (IQ) scores. Low levels of leadexposure may also cause hypertension in middle-aged men. Pregnant women exposed to lead may transfer the substance to thefetus, which may cause preterm birth, reduced birth weight, anddecreased IQ in the infant. Results of studies have shown thatlead causes cancer in laboratory animals; however, it is notknown whether lead causes cancer in humans (8).
The Centers for Disease Control (CDC) has cautioned thatconcentrations of lead in residential soil or dust greater than500 to 1,000 arts per million (ppm) could lead to elevated bloodlead levels in children inhaling or ingesting soil. Lead levelswithin the range of these values were found in soil samplescollected from on-site areas.
Based on information reviewed, ATSDR has concluded that thePrewitt Abandoned Refinery site is of potential public healthconcern because humans may be exposed to benzene and lead, foundin on-site and off-site groundwater, and to benzo(b)fluoranthene,chromium, chrysene, and lead, found in on-site surface soil andsediment.
In accordance with Comprehensive Environmental Response,Compensation, and Liability Act of 1980 (CERCLA) as amended, thePrewitt Abandoned Refinery site has been evaluated forappropriate follow-up with respect to health effects studies. Since human exposure to on-site and off-site contaminants maycurrently be occurring and may have occurred in the past, thissite is being considered for follow-up health effects studies. After consultation with Regional EPA staff and State and localhealth and environmental officials, the Division of HealthStudies, ATSDR, will determine if follow-up public health actionsor studies are appropriate for this site.
As additional information is received by ATSDR, such materialwill form the basis for further assessment as warranted by site-specific public health issues.
ATSDR recommends the following to protect public health:
- Continue to monitor private wells, including residential wells and the Baca Chapter well, located off-site and within 1 mile of the site to determine whether water is suitable for continued potable use.
- Abandoned on-site wells should be properly plugged to preventtheir well casings from serving as conduits for the migrationof contaminants to deep aquifers.
- Conduct additional on-site and off-site groundwatermonitoring to define local hydrogeology and identify thenature and extent of the contaminant plume.
- Conduct additional soil and sediment monitoring to defineareas of soil contamination.
- Include the following in the remediation workplan ifadditional site remediation occurs:
Provide adequate personal protective equipment that meets thestandards of the Occupational Safety and HealthAdministration (OSHA) for workers conducting remedialactivities in and around the site.
Follow appropriate precautionary guidelines, regulations, andadvisories from the National Institute for OccupationalSafety and Health (NIOSH) and OSHA.
Employ methods of dust suppression if remedial activitieswill involve ground-disturbing activities. Appropriate real-time,peripheral air monitoring should be done duringworking hours in addition to on-site air monitoring. Levels of contaminants in the ambient air at the periphery of thesite should not exceed National Ambient Air Quality Standards(NAAQS) or NIOSH recommendations.
Environmental and Health Effects Reviewer:
Richard Earl Gillig, M.C.P.
Environmental Health Scientist
Remedial Programs Branch
ATSDR Regional Representative:
Public Health Advisor
Regional Support Services
1. Hazardous Ranking Score Package, Prewitt Abandoned RefinerySite, Prewitt, New Mexico. Steven Cary, August 11, 1986.
2. Evaluation of EPA's Proposed Listing of the Prewitt AbandonedRefinery Property on the CERCLA National Priorities List. Woodward-Clyde Consultants, August 1988.
3. Expanded Site Inspection, Prewitt Abandoned Refinery Site, Prewitt, New Mexico. Ecology and Environment, Inc. September 23, 1988.
4. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Benzene. Atlanta: ATSDR, 1989.
5. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Benzo(b)fluoranthene. Atlanta: ATSDR, 1989.
6. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Chromium. Atlanta: ATSDR, 1987.
7. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Chrysene. Atlanta: ATSDR, 1987.
8. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Lead. Atlanta: ATSDR, 1987.