BLAINE, ANOKA COUNTY, MINNESOTA
The Minnesota Department of Health (MDH) received a request from the Minnesota Pollution Control Agency (MPCA) to evaluate potential public health concerns regarding the Gallagher Dump that is located in the city of Blaine, Anoka County, Minnesota (the site). The site was identified by the MPCA through its Dump Assessment Program as an "action site," indicating that the site warranted further evaluation due to its potential to adversely impact public health or the environment. The site had also been identified by the MPCA as a possible source of contamination found in three Blaine city wells. This health consultation is based on a site visit conducted by MDH staff on April 29, 1999, private water supply well sampling conducted by MDH staff in 1989, 1991, 1997, and 2001, a review of previous MDH documents, and information provided to MDH by the MPCA and its consultant, STS Consultants, LTD (STS 2000a; STS 2000b).
The city of Blaine is located on the northern edge of the seven county metropolitan area that comprises the Twin Cities of Minneapolis and St. Paul. The site is located between 91st and 93rd Avenues, approximately 2 miles southwest of the center of the city of Blaine and immediately west-southwest of the Anoka County Airport (see Figure 1). The dump occupies approximately 30 acres and is currently used as a solid waste transfer station. Very little waste is exposed at the surface of the site.
Historical information shows the dump was operated between 1955 and the early 1970s. Reportedly, household, municipal, industrial, and possibly hazardous wastes, including ash from an on-site incinerator, were deposited there. The wastes may have been placed in contact with surface water or groundwater, and were occasionally burned. Based on a Phase II site investigation, the volume of waste at the site is estimated to be approximately 265,000 cubic yards.
In April 1989, MDH sampled six private wells near the site. Samples were collected for volatile organic compounds (VOCs) and general chemistry analyses. Analytical results showed a low concentration of 1,2-dichloroethane (1,2-DCA) in a water sample collected from one well completed in the Ironton-Galesville aquifer, but an analysis of a subsequent sample collected in 1991 from that well did not detect any VOCs (MDH 1997). However, the report that describes this sample does not identify the well location and it is unclear whether this well was a private or public water supply well. A review of well logs from the area suggests that it was a public water supply well because private wells in the area are generally completed in aquifers above the Ironton-Galesville. Review of the MDH files did not locate any laboratory reports of a detection of 1,2-DCA in a private well. It seems most likely that the reported detection was in city well #3 or #4, both of which were sampled in 1989 and found to have low concentrations of 1,2-DCA.
In 1997, MDH sampled one well near the site. MDH was unable to re-sample other private wells sampled earlier because the homeowners did not grant permission. Water samples were taken from the well, which is completed in the Quaternary deposits, and analyzed for VOCs, general chemistry, and tritium analyses. No VOCs were detected above the laboratory reporting limits. Two additional wells were sampled in 2001 (see Figure 1), one of which was first sampled in 1991. Both of these wells are also completed in the Quaternary deposits, and the samples were analyzed for VOCs, metals, and general chemistry parameters. No VOCs were detected, and concentrations of metals and general chemistry parameters were within normal limits.
Since 1993, 1,2-DCA has been detected at levels above the federal drinking water standard for public water supplies (the Maximum Contaminant Limit, or MCL) in three Blaine municipal wells (wells #3, #4, and #16). Other VOCs such as tetrachloroethylene and chloromethane have also been detected. The VOC concentration trends in these wells are illustrated graphically in Figures 2, 3, and 4. The Blaine city wells, which are located within one mile of the site, have been the focus of several investigations conducted by the MPCA, and are listed on the state Superfund list. The city wells are completed between 500 to 700 feet below grade and are cased in bedrock to depths of between 200 to 300 feet. The source of the 1,2-DCA contamination in the city wells has not been determined despite several investigations conducted in the area by the MPCA. The lack of contamination in private wells near the Gallagher dump indicates that it is likely not the source of the city well contamination.
Based on geologic information provided in the Phase I report (STS 2000a), soils at the site are composed primarily of the fine sands and sandy loam developed on sandy outwash materials deposited during the Wisconsinan glaciation. The uppermost bedrock beneath the site is either the St. Lawrence Formation (dolomite) or Franconia Formation (sandstone), both of upper Cambrian age, at 200 to 300 feet below grade.
Groundwater at the site was encountered at depths of 11 to 18.5 feet below ground. Based on topography and regional hydrology, the groundwater is expected to flow north and northeast towards First Silver Lake. Only temporary monitoring wells were installed to collect water samples, so flow direction beneath the site could not be determined.
On April 29, 1999, Jim Kelly, Melinda Salisbury, and Lisa Pogoff of the MDH and Andrew Nichols of the MPCA visited the site. A solid waste transfer facility now occupies the southwest corner of the site and the southern one-third of the site is used for storage of waste containers. The remainder of the site is vegetated with scattered trees and thick grass. No extensive areas of exposed waste were observed, but some waste was exposed on the east side and in the adjacent ditch. No evidence of environmental impairment, such as surface staining or vegetative stress was observed. The site is surrounded by developed or developing commercial properties, mostly offices and warehouses. The nearest residences were to the south, across U.S. Highway 10.
Fifteen soil borings were advanced by STS at the site. All of the borings were completed as temporary monitoring wells, the locations of which are shown in Figure 5. The borings encountered a discontinuous layer of sand and clay cover material up to 3 feet thick overlying up to 15 feet of waste, which in turn was underlain by natural sand and silt deposits. Wastes encountered included paper, wood, glass, metals, and other debris. Cross sections of the dump are presented in Figures 6 and 7.
Organic vapors were detected in all of the borings using a photo ionization detector (PID) during drilling, with concentrations ranging up to 30 PID units. Methane gas was detected in nine borings at concentrations exceeding the lower explosive limit (LEL). Methane concentrations ranged from 0.4 to 47 percent (see Table 1). The lower explosive limit for methane is 5.35 percent, and represents the lowest concentration of methane in air capable of burning.
Surface soil was analyzed from four locations for metals, polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), diesel range organics (DRO), pesticides, and herbicides. Two metals (chromium and copper) exceeded their MPCA Soil Leaching Values (SLVs) and one (copper) exceeded its MPCA Soil Reference Value (SRV). The SLV represents the concentration of a contaminant in soil above which leaching could contaminate the groundwater at levels above the established standards. The SRV represents the concentration of a contaminant in soil at or below which normal dermal contact, inhalation, and/or ingestion is very unlikely to result in an adverse human health effect. It should be noted, however, that the chromium analysis was for total chromium, but the results were compared to the more toxic chromium VI screening criteria. Also, copper was detected in the method blank, casting some doubt on this detection. In addition, three PCBs were detected, one of which (Arochlor 1260) exceeded its SRV. Three pesticides, ten PAHs, and DRO were also detected at low levels. The surface soil analytical results and screening criteria are presented in Table 2.
Waste samples from four soil borings were analyzed for volatile organic compounds (VOCs), metals, PCBs, PAHs, DRO, pesticides, and herbicides. Seven metals (arsenic, cadmium, chromium, copper, lead, mercury, and nickel) exceeded their SLVs and five metals (arsenic, chromium, copper, lead, and mercury) exceeded their SRVs. In addition, barium was detected at elevated levels. Eighteen VOCs were detected, four at concentrations exceeding their SLV. The VOC 1,2-DCA was not detected in the waste samples. Eleven PAHs were detected (in one boring only) and benzo(a)pyrene exceeded its SRV. DRO was detected in all of the samples at levels of 730-2,400 milligrams per kilogram of soil (mg/kg). Four PCBs were detected at concentrations exceeding their SRVs, and two at concentrations exceeding their SLVs. The pesticide DDT was detected in two borings. The waste sample analytical results are presented in Table 3.
Soil collected below the waste horizon from four soil borings was analyzed for VOCs, metals, PCBs, PAHs, DRO, pesticides, and herbicides. No compounds were found to exceed their SLV or SRV and only background concentrations of metals were detected. DRO was detected in two borings at relatively low concentrations (19-23 mg/kg). No other compounds were detected. The soil analytical results and screening criteria are presented in Table 4.
Groundwater from fifteen soil borings and the well purge/development water, was analyzed for VOCs, metals, PCBs, PAHs, DRO, pesticides, and herbicides. Elevated levels of barium, arsenic, nickel, selenium, and mercury were detected, but only arsenic (at 51.7 micrograms per liter (ug/l)) exceeded its drinking water standard. Arsenic was detected in all of the borings at concentrations ranging from 9-32 ug/l. Twenty-four VOCs were detected, including 1,2-DCA in one boring. Three of the VOCs (1,4-dichlorobenzene, benzene, and ethylbenzene) exceeded their respective Health Risk Limits (HRL). The HRLs are promulgated MDH standards for private drinking water supplies. If contaminant concentrations in drinking water are at or below their HRLs, the water is considered safe for human consumption over a lifetime. DRO exceeded its Health Based Value (HBV) in all of the samples. An HBV is similar to an HRL, but has not been promulgated into rule. One pesticide, DDD, was detected in one sample. No PCBs, PAHs, or herbicides were detected. The groundwater analytical results are presented in Table 5.
Sediment from four locations in the adjacent ditch was analyzed for metals, PCBs, PAHs, pesticides, and herbicides. The sediment screening criteria were exceeded by four metals (cadmium, copper, lead, and mercury) and elevated concentrations of barium were detected (there is no criterion for barium in sediments). One sample also contained very high concentrations of DDT (200 ug/kg) and the PCB Arochlor-1254 (1.8 mg/kg). No herbicides were detected. The sediment criteria are based on effects on aquatic organisms and exceedances of these criteria do not necessarily indicate a human health concern. The sediment analytical results and criteria are presented in Table 6.
Dumps may pose a potential human health risk when people come into contact with chemicals in soil, water, or air at levels of health concern, or when people are exposed to physical hazards such as sharp objects or uneven ground. This requires that a chemical and/or physical hazard is present and that people are in contact with them.
Waste materials in old dumps are often buried beneath a thin layer of whatever type of soil is easily available. Sometimes the cover consists of a waste material such as ash or sand blast sands, which usually contain high concentrations of metals. Often the cover materials are thin or absent in spots, exposing wastes and contaminants. Over time, compaction and degradation of the waste results in settling and the emergence of large, sharp objects such as scrap steel, which can become a physical hazard.
Organic waste materials in the dump (if it was not burned regularly) often degrade and generate methane and other gases. Low levels of chemical solvents may also be present in gas produced by old dumps. Together, these gases are referred to as "landfill gases." These gases are frequently explosive and can migrate up to a few hundred feet from the dump site, depending on local conditions. This gas migration can result in explosive levels of methane and concentrations of solvents above health concern in nearby homes or buildings.
The degradation of solid waste also produces leachate when infiltrating water contacts the waste and dissolves chemicals from it. Leachate may discharge to surface water or infiltrate into groundwater. Groundwater contaminated by leachate usually does not have any distinguishing appearance, color, or taste, and people are rarely aware of any problem unless the water is tested. Soil with contaminant concentrations below the SLVs is not expected to generate leachate at levels that would be above groundwater or surface water criteria.
The Gallagher Dump is a typical urban/suburban dump because it was located near a town and accepted all types of wastes. Although few waste materials are exposed at the dump surface, surface soils contain several contaminants at concentrations that exceed their SRV. In addition, numerous contaminants were detected in the waste horizon within the dump, in the groundwater beneath the dump, and in sediments in the ditch adjacent to the dump. Also, high concentrations of methane gas were detected during the site investigation, which could pose an explosive hazard if this gas migrates and accumulates in any of the buildings on or adjacent to the site. VOCs may also be present in the landfill gas, and could pose a health concern.
Groundwater samples exceeded health-based drinking water standards for five compounds (arsenic, 1,4-dichlorobenzene, benzene, ethylbenzene, and DRO), but also contained a large number of VOCs, one pesticide, and elevated concentrations of several metals. The presence of high concentrations of DRO, as well as other VOCs and PAHs that may be related to petroleum, indicate the potential for significant petroleum contamination to be present in the dump. The site investigation did not define the horizontal extent of groundwater contamination, so it is not clear whether widespread contamination is associated with this site.
One of the VOCs detected at the site, 1,2-DCA, has been detected at concentrations above drinking water standards in the city wells. It is not clear whether the dump has contributed toward the contamination of water supply wells in the area, although it appears unlikely. Other potential sources of this contaminant may exist within the area of the site.
1,2-DCA has been used in the manufacturing of vinyl chloride and insecticidal fumigants and is a constituent in tobacco flavoring, paints, varnish, finish removers, and metal degreasers. Its most common use today is for the production of vinyl chloride and other chemicals and to dissolve grease, glue, and dirt. In the past it was added to leaded gasoline to remove lead. 1,2-DCA is classified as a probable human carcinogen by the U.S. Department of Health and Human Services. Exposure to high levels of 1,2-DCA in air or water are also associated with adverse effects to the heart, central nervous system, liver, kidneys, and lungs (ATSDR 2001).
The detection of heavy metals such as mercury and lead in sediments is evidence that the site is impacting the surrounding wetlands. While the sediments are unlikely to represent a direct exposure concern, the presence of bio-accumulating compounds such as mercury, DDT and PCBs could contribute to contamination in area wildlife that are hunted or fished and consumed. Bio-accumulating compounds are chemicals that increase in concentration as they move up the foodchain.
Agency for Toxic Substance and Disease Registry (ATSDR) Child Health Initiative
ATSDR's Child Health Initiative recognizes that the unique vulnerabilities of infants and children make them of special concern to communities faced with contamination of their water, soil, air, or food. Children are at greater risk than adults from certain kinds of exposures to hazardous substances at waste disposal sites. They are more likely to be exposed because they play outdoors and they often bring food into contaminated areas. They are smaller than adults, which means they breathe dust, soil, and heavy vapors close to the ground. Children also weigh less, resulting in higher doses of chemical exposure per body weight. The developing body systems of children can sustain permanent damage if toxic exposures occur during critical growth stages. Most importantly, children depend completely on adults for risk identification and management decisions, housing decisions, and access to medical care.
Children may be attracted to exposed debris areas due to the presence of bottles, shiny metal objects, exposed dirt, etc. Very small amounts of waste are exposed at the site and surface soils are contaminated at concentrations that exceeded human exposure standards. However, the current use of the site as a waste transfer station and its location in an area of office buildings and warehouses suggests that children are not frequenting the site. Children may have been exposed to 1,2-DCA in water from private wells or from the municipal water supply system in the past.
Based on a review of available information in MPCA and MDH files, a site visit conducted on April 29, 1999, and analysis of private water supply samples, it appears that this site poses an indeterminate public health hazard. The hazards include potential chemical hazards from contact with contaminated surface soils and explosive hazards if methane gases migrate to and accumulate in on-site or off-site buildings. Also, a wide range of contaminants are present in the waste materials at the site and in the groundwater beneath the site, which could potentially migrate to off-site receptors. Private well sampling data suggest that the site is not impacting nearby wells, however. It is unclear at this time whether the site is acting as a source for VOC contamination detected in the nearby city wells.
- Additional cover soil should be placed on the surface of the dump to prevent exposure to contaminated soils. This would also likely help to reduce the amount of contamination entering the adjoining wetland as a result of runoff. The cover material should be able to support vegetation and graded to promote runoff without excessive erosion.
- On-site and nearby structures should be evaluated for potential infiltration of landfill gases.
- Institutional controls such as a notice filed with the property deed should be implemented to record the location of the dump for future reference.
- The MPCA should continue to evaluate potential sources of the contamination in the Blaine city wells, including the Gallagher Dump.
- The extent of groundwater contamination associated with the site should be defined.
- Private water supply well owners should be advised to connect to city water and to properly seal their wells if they are no longer in use.
MDH's Public Health Action Plan for the site will consist of:
- A letter to the MPCA, city and county authorities, and the site owner advising them of our recommendations;
- A review of any additional data that becomes available, and participation in any meetings or other public outreach activities.
ATSDR 2001. ATSDR ToxFAQsTM, Agency for Toxic Substances and Disease Registry, Atlanta, GA. Found online at: http://www.atsdr.cdc.gov/tfacts38.html.
MDH 1997. Annual Report, Dump Monitoring Program.
STS 2000a. Draft Phase I Environmental Site Assessment. STS Consultants, LTD, July 18, 2000.
STS 2000b. Draft Phase II Environmental Site Assessment. STS Consultants, LTD, October 20, 2000.
US Department of Health and Human Services, 1998. Health Consultation: Blaine Municipal Wells, December 22, 1998.
Site Assessment and Consultation Unit
Minnesota Department of Health
tel: (651) 215-0917
Site Assessment and Consultation Unit
Minnesota Department of Health
tel: (651) 215-0913
Technical Project Officer
Division of Health and Consultation
State Program Section
Agency for Toxic Substances and Disease Registry
This Gallagher Dump Health Consultation was prepared by the Minnesota Department of Health under a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR). It is in accordance with approved methodology and procedures existing at the time the health consultation was begun.
Technical Project Officer, SPS, SSAB, DHAC, ATSDR
The Division of Health Assessment and Consultation, ATSDR, has reviewed this public health consultation and concurs with the findings.
Lisa C. Hayes
for Richard Gillig
Chief, Superfund Site Assessment Branch, DHAC, ATSDR