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HEALTH CONSULTATION

LE MARS COAL GAS SITE
LE MARS, PLYMOUTH COUNTY, IOWA

 

STATEMENT OF ISSUES AND BACKGROUND

The U. S. Environmental Protection Agency (EPA), Region VII Office, provided the Iowa Department of Public Health (IDPH), Toxic Substances Evaluation Program (TSEP) with information related to the Le Mars Coal Gas site in Le Mars, Iowa. Iowa Department of Natural Resources (IDNR) asked TSEP to review the data and information provided in the Site Inspection Report (SI) for the Le Mars Coal Gas Site (February 9, 1998) and determine whether contamination from the site poses a public health hazard. This Health Consultation only applies to an evaluation of the data and information referenced in this document. This evaluation will provide information about the potential public health and children's health impact resulting from exposure to on-site and off-site contaminated media. Any additional information or site activities could alter the conclusions and recommendations provided in this Health Consultation.

The Le Mars Coal Gas site is approximately 1.6 acres. It is located in Le Mars City, Plymouth County, Iowa (Figure 1). The surrounding area is mostly residential or undeveloped. The site property is triangular shaped and bordered on the south and east by public sidewalks and parking, and to the north and west by railroad tracks (Figure 2).

Based on 1990 U.S. Census Data, 6720, 2847, and 770 people lived within 1 mile, 0.5 mile and 0.25 mile of the site, respectively. The population is predominantly Caucasian. There were 733, 306, and 81 children, under the age of six, living within 1 mile, 0.5 mile and 0.25 mile of the site, respectively (Figure 3).

The property is currently owned by the City of Le Mars. Previous owners include the Le Mars Gas Company, Iowa Public Service Company, and private parties. A historic plant layout can be seen in Figure 4. Past waste disposal activities at this site are unknown. However, major types of chemical classes associated with coal gasification sites includes volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs), particularly polynuclear aromatic hydrocarbons (PAHs), and inorganic compounds.

Initial Soil Sampling (November 1990):

A city contractor (CDM Federal) collected subsurface soil samples from two soil borings in the underground storage tank (UST) area in November 1990. The borings were drilled to approximately 20 feet below ground surface (bgs) and were sampled to satisfy the existing Iowa UST insurance requirements. The analytical results indicated that total organic hydrocarbons were present above the existing guidelines. It was postulated that an UST leak had occurred. Two UST monitoring wells were installed by the city for purposes of detecting leakage. In December 1990, a city contractor (Siouxland Environmental Services, Inc.) conducted a pressure test of the USTs. The results indicated that the USTs were not leaking.

Monitoring Well Installation (February 1995):

The Iowa Underground Storage Tank Board (UST Board) developed a State-funded Community Remediation Project (CRP) to handle UST sites in Iowa. The Le Mars site CRP involved the installation of three additional monitoring wells in the area of the USTs. In February 1995, three monitoring wells were installed by Geotek Engineering & Testing Services, Inc. under contract with the UST Board. The three wells (MW-1, MW-2, and MW-3) were completed to a depth of 20-25 feet bgs. Cresol-like odors were encountered during drilling. Soil samples were collected from the borehole locations at 2.5 foot intervals. The highest detected concentrations of total petroleum hydrocarbon (TPH) and PAHs were from 20-25 feet bgs. The highest concentration of TPH as gasoline and TPH as fuel oil was detected at 4320 mg/kg and 12,000 mg/kg, respectively in MW-1 at 22 feet bgs. The highest concentration of total carcinogenic PAHs and total noncarcinogenic PAHs at 1024 mg/kg and 2776 mg/kg, respectively in MW-3 at 25 feet bgs. Groundwater samples were not collected. The identification of coal tar contamination prompted the UST Board to delete the site from the UST program and refer it to the EPA Superfund Program for further investigation.

Site Inspection (February 1997):

The scope of the site inspection (SI) included soil, sediment and groundwater sampling to identify the source and extent of contamination. During November 1996, Ecology & Environment, Inc. conducted a site reconnaissance for SI activities of the Le Mars Coal Gas site. City officials indicated that a 500 gallon underground waste oil tank was located approximately 10 feet southwest of the underground diesel fuel tank. It was reported that the waste oil tank was very old and collected waste oil from the maintenance shop.

Twenty eight surface (0-2 feet) and subsurface soil samples (various depths up to 20 feet), eight groundwater samples and seven sediment samples were collected (Figure 5 and Figure 6). Soil samples were analyzed for VOCs, SVOCs, total metals and cyanide. Groundwater samples were analyzed for lower detection limit VOCs, ethylene dibromide (EDB), methyl-tert-butyl ether (MTBE), SVOCs, total and dissolved metals and cyanide.

Biased sampling of surface and subsurface soils was conducted to locate potential source areas and migration pathways. The highest detected on-site concentrations of SVOCs (2273 mg/kg carcinogenic PAHs and 8506 mg/kg noncarcinogenic ) and VOCs (primarily benzene, toluene, ethylbenzene, and xylene (BTEX)) were recorded in the eastern portion of the site from approximately 6 to 17 feet bgs in the former gasometer area. In eastern portion of site, groundwater is approximately 12-15 feet bgs. Consequently, it appears that contamination is located below the groundwater. Even though detected levels of SVOCs and VOCs were above health-based comparison values in subsurface samples, the depth of the contamination does not support exposure via direct contact or inhalation of volatile compounds. Exposure to detected levels of VOCs, SVOCs and inorganic compounds in surface soil (0-2 feet) is unlikely to result in adverse health effects. Consequently, on-site contamination does not pose an apparent health threat to the general public. Workers conducting subsurface activities should take the proper precautions when handling soil near the former gasometer area.

Seven sediment samples were collected from the on-site drainage-way (#206), open drainage ditch (#204 and #205), Willow Creek (#201, #202, and #203), and the buried drainage-way/culvert (#207) approximately 35 feet upstream of the on-site drop inlet (background sample). VOCs were not detected in any of the sediment samples. Inorganic compounds were detected in the sediment samples, however exposure to these levels would not result in a public health threat. SVOCs were detected in six of the seven sediment samples. The background upstream culvert sample was below detection. The highest concentration of total PAHs (343 mg/kg) was detected in the on-site drainage-way sample. Data suggests that the uppermost portion of the aquifer is above or at the bottom of the drainage ditch, therefore a groundwater/surface water interface may be present. During the site visit a groundwater/surface water interface was not observed and was apparent from existing data. The physical and chemical properties of PAHs (e.g., specific gravity >1) would support downward migration in the saturated zone. Also, PAHs bind strongly to organic matter and soil particles, thus lessening their bioavailability. While access to the drainage ditch is not restricted, it is not readily accessible because the bank is step and there is no direct access route. Long-term exposure to sediment is unlikely and should not pose a threat to public health.

An off-site residential background surface soil sample (Sample #118) and subsurface soil samples (Sample #119, #120, #121) were collected. The highest detectable concentration of total PAHs (71.8 mg/kg) was found at 16-18 feet bgs. VOCs were below detection except for carbon disulfide and toluene which were detected at less than 1 mg/kg. Analytical results from soils collected at the offsite residential background location indicate that exposure to reported levels would not pose a public health threat.

Analytical results from groundwater samples collected from MW-1, MW-2 and MW-3 indicated that SVOCs (including PAHs), VOCs (primarily BTEX), and several inorganic compounds were above health-based comparison values. Benzo(a)pyrene ranged from below detection to 180 mg/L. BTEX represented the majority of VOCs detected. Benzene was the highest detected VOC, with concentrations ranging from 3,800 g/L to 120,000 <>mmg/L, dissolved = ND) was the highest detected site related inorganic compound.


The Le Mars City Municipal Wells No. 4 and No. 8 are approximately 2000 feet downgradient (northwest) of the site. Groundwater samples collected from the Le Mars City Municipal Well No. 8 had detectable levels of total xylene (4 mg/L), carbon disulfide (35 mg/L), benzo(a)pyrene (0.012 mg/L), and cyanide (26 mg/L). Municipal Well No. 8 was re-sampled for VOCs on July 2, 1997, except for carbon disulfide (560 mg/L) all VOCs detected were below health based comparison values. Municipal Well No. 4 was below detection for organic constituents and below health based comparison values for inorganic constituents during both sampling events.As reported in the SI, city water officials indicated that the nearest private well is located approximately 3,000 feet upgradient (southeast) of the site. Additionally, six residential wells are within 1 mile of the site.

Site Visit (1998):

On April 22, 1998, TSEP staff visited the site to observe current conditions and to meet with the Le Mars Public Works Supervisor. It was determine that public/community health concerns related to the site do not exist. The city would like to resolve issues associated with the Le Mars Coal Gas site and are awaiting direction from U.S. EPA.

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