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The U. S. Environmental Protection Agency (EPA), Region VII Office, provided the Iowa Department of Public Health, Toxic Substances Evaluation Program (IDPH/TSEP) with a copy of the Removal Site Assessment Report for the Economy Products Company site in Shenandoah, Iowa.1 EPA asked TSEP to review the data and information provided and determine whether contamination from the site poses a public health hazard. EPA is considering a removal action at the site. This Health Consultation only applies to an evaluation of the data and information provided in references (1), (2), (3), (4) and (5) of this document. This evaluation will provide information about the potential public health impact of 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 Economy Products Company (EPC) site is a 1-acre property located in Shenandoah, Page County, Iowa (Figure 1). The surrounding area is a mixture of commercial and residential properties. The east and south side of the site is bordered by the Earl May Seed and Nursery Company (EMSNC), and to the north and west, by 8th Avenue and Southwest Road, respectively (Figure 2). EPC operated as an agricultural chemical firm that formulated various pesticides, including organochlorine (OC) pesticides, from 1961 to 1973. Some of the pesticides are now banned or have been subjected to restricted use regulations (i.e., aldrin, chlordane, tetrachlorodiphenylethane (DDD), dichlorodiphenyltrichloroethane (DDT), dieldrin, endrin, heptachlor, lindane, and toxaphene).

On May 10, 1973, a fire destroyed the chemical warehouse together with the main packaging area and an adjacent building. An office building situated on the southwest corner of the property was the only structure remaining. In 1974, EMSNC purchased the EPC property and currently uses the building to store nursery stock. The remainder of the site is composed of soil/grass plots, which are segregated by concrete sidewalks (Figure 3). The closest private residence is approximately 40 feet south of the site.

It was thought that pesticide residues were dispersed throughout the site and surrounding areas during the fire. Following the fire, most of the recoverable hazardous chemical materials/residues were removed and disposed of at off-site locations by the Iowa National Guard. The bulk of the hazardous materials were buried in the Stennett limestone quarry in Stennett, Iowa, and the remaining debris and rubble were disposed of at the Shenandoah Municipal Landfill. The area where the fire occurred was covered with a one-foot clay cap.1

Preliminary Assessment (1988):

The Iowa Department of Natural Resources (IDNR) performed a Preliminary Assessment (PA) of the site in 1988, which included the Stennett quarry and Shenandoah landfill. The PA recommended additional sampling of soils and groundwater at the EPC site. IDNR concluded that the waste disposed of at the Stennett quarry did not pose an immediate threat to human or the environment. It was also determined that a slight potential for groundwater contamination exists at the Shenandoah landfill. The report suggested that down gradient residents might potentially be impacted by a migrating contaminant plume.

Site Inspection (1993):

A Site Inspection (SI) was conducted by Camp, Dresser and McKee (CDM) Federal Program under EPA contract in 1993.1 Surface soil, subsurface soil, and sediment from drainage pathways near the site were sampled. On-site groundwater samples could not be collected because clay-rich soils repeatedly plugged inlet holes of the subsurface sampling probe.

During the SI a surface soil sample, taken between the south site boundary and the nearest residence contained several OC pesticides. Aldrin, dieldrin, DDD, DDT, gamma chlordane, and methoxychlor were detected at concentrations between 2.37 milligrams per kilogram (mg/kg) and 35.1 mg/kg. An on-site subsurface soil sample (collected where the former chemical warehouse was located), taken at a depth of 2.5 feet, contained DDD, DDT, alpha-chlordane and gamma-chlordane at concentrations ranging from 75.2 mg/kg to 468.0 mg/kg. The subsurface sample also contained two herbicides: 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) at 0.29 mg/kg and 1.1 mg/kg, respectively. OC pesticides and herbicides were detected in sediment samples collected from drainage pathways downgradient of the site. Based on the results of the SI, EPA recommended that additional soil sampling be conducted to assess the potential threat to EMSNC employees, nearby residents, and surrounding areas.

Site Assessment (1994):

In February 1994, Ecology and Environment, Inc./Technical Assistance Team (E & E) and EPA conducted a site assessment and collected soil samples. The site assessment report (April 22, 1994) indicated that twelve surface soil samples (0" to 3") and one subsurface soil sample (22" to 34") were collected on-site and immediately off-site. The samples were analyzed for OC pesticides and herbicides. The highest concentrations of OC pesticides were detected in the subsurface soil sample (Sample No. 011). This sample was collected in the area where the former chemical warehouse was located. This area is now covered with a one foot clay cap. Nine OC pesticides were detected with a total pesticide concentration of 343.1 mg/kg. Five off-site surface soil samples were collected. The highest concentrations were found in a composite sample (Sample No. 005) collected between the EMSNC office building and a residential property. The total pesticide concentration was 24.2 mg/kg. The surface and subsurface sampling results are presented in Table 1.

Three samples were also analyzed for polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzodioxins (PCDDs), which are commonly associated with OC pesticides. Concentrations of PCDFs and 2,3,7,8 TCDD equivalents were below 1.0 microgram per kilogram (µg/kg).

In 1994, at the request of EPA, the Agency for Toxic Substances and Disease Registry (ATSDR) prepared a health consultation that reviewed the data and information in the SI Report to determine whether contamination from the site posed a public health hazard. ATSDR recommended that areas containing total organochlorine pesticide residues in excess of 10 mg/kg should be remediated. A surface and subsurface sample collected where the fire occurred and one surface sample collected along the southern portion of the site exceeded this level. Three surface samples collected from the residential properties were below 10 mg/kg total pesticide. ATSDR stated that, if the on-site subsurface area with high concentrations was unearthed during excavation, it could pose a health hazard to workers or future site occupants. Also, long-term exposure (> 365 days) to concentrations > 10 mg/kg total pesticide could pose a significant health risk. It was further recommended that EPA consider additional soil sampling to determine the extent of soil contamination.4

Comprehensive Removal Assessment (1995):

Based on the results of the SI, EPA authorized a comprehensive removal assessment (conducted in February 1995) to determine the extent of soil contamination and to assess the leaching potential of the contaminants. It was proposed that soil (surface and subsurface), groundwater, and sediment from drainage ditches be collected.

Soil samples were field-screened for total DDT (DDT, DDD, and dichlorodiphenyldichloroethylene (DDE)) using an immunoassay kit. Total DDT was selected as the surrogate compound to provide an indication of total pesticides in soils. The results of the site assessment (February 1994) showed that a direct correlation existed between concentrations of total DDT and total pesticides. It was also determined that 10 mg/kg total pesticides in soil be used as the screening level to define boundaries of contamination at the site. It was also proposed that 10 mg/kg total OC pesticide be used as a removal action level. This proposal was based largely on precedence at similar EPA Region VII OC pesticide sites. However, further consideration and investigation by Region VII EPA resulted in the decision that chemical specific clean-up levels would be used at the EPC site.2 A summary of analytical results from the February 1995 sampling event is provided in Table 2.

A grid was established across the site to identify soil sample locations. Surface soil samples were collected from 115 locations at depths of 0-4 inches. Grab samples were collected from 113 of those locations and two composite samples were collected from locations along the west side of Southwest Road. Twenty-five (approximately 20 %) of the screened surface soil samples and one composite sample from the drainage ditch west of the Burlington Northern Railroad tracks (west of Southwest Road) were analyzed for pesticides to confirm the screening results. Only surface samples collected in the southern portion of the site (south of the office building) were analyzed to confirm the screening results. The detected concentration of total OC pesticides ranged from approximately 1 mg/kg to 606 mg/kg in twenty-one of the surface samples. The remaining five surface samples were below levels of detection.

Twenty-nine subsurface samples (up to 24 feet in depth) were collected from 18 locations. At most locations, sampling/screening continued at increasing depths, until a screening concentration <10 mg/kg total DDT was recorded. Six (approximately 20 %) of the screened subsurface samples were analyzed for pesticides to confirm the screening results. Only subsurface samples collected in the southern portion of the site (south of the office building) were analyzed to confirm the screening results. The concentration of total OC pesticides ranged from approximately 368 mg/kg to 9,670 mg/kg in three of the subsurface samples. The remaining three subsurface samples were below levels of detection.

A surface and subsurface sample were also collected and analyzed for volatile organic compounds (VOCs). The data quality of the surface soil sample was compromised by improper sample collection techniques. The subsurface sample had detectable levels of six VOCs. The highest individual concentration detected was total xylene (3.1 mg/kg).

Groundwater sampling was attempted at two locations using a Geoprobe to install temporary well points. Groundwater was not encountered at the off-site location (hollow steel rods were driven to refusal at a 21' depth). Groundwater was encountered at 24.5 feet at the on-site location. However, a groundwater sample could not be collected due to the low hydraulic conductivity.

Two sediment samples were collected from the drainage pathway south of the office building. The screening results indicated that the total DDT concentration was less than 10 mg/kg. However, neither of the samples were confirmed through analytical methods.

Extent of Contamination Groundwater Investigation (1995):

In 1995, Region VII EPA requested that Roy F. Weston, Inc./Response Engineering and Analytical Contract (REAC) perform an extent of contamination (EOC) groundwater investigation, and an evaluation of treatment and disposal options. The objectives of the EOC were to determine the presence, lateral and vertical extent, and magnitude of pesticide, herbicide, and VOC contamination in the site's surficial aquifer. Groundwater monitoring wells and piezometers were installed. Soil and groundwater samples were collected and specific samples were analyzed.

Five sampling locations were selected (Figure 2). Three permanent groundwater wells and four permanent piezometers were installed, at varied depths, on and surrounding the former EPC site. Additionally, two temporary piezometers were installed at Locations No. 1 (deep) and No. 2 (deep). Soil samples were collected from each bore hole at various depths. They were analyzed for pesticides, semivolatile organic compounds (SVOCs), target analyte list (TAL) metals, and VOCs. Groundwater samples were collected and analyzed for pesticides, herbicides, SVOCs and VOCs.

A soil sample collected at Location No. 5 had the highest reported concentration of pesticides, SVOCs, and VOCs. Location No. 5 is where the former chemical warehouse was located. Pesticides, SVOCS, and VOCs were detected from 1 to 23 feet in depth. The highest total pesticide concentration was detected in the one to three foot interval (1,079 mg/kg) at this location. The highest concentration of total pesticides from Locations No. 1 and No. 4 were 52 mg/kg (0 to 6' depth) and 160 mg/kg (0 to 2' depth) , respectively. The concentration of total pesticide at Location No. 2, was 1 mg/kg or less from 0 to 24 feet. Pesticides were not detected in soil from Location No. 3. Herbicides were not detected in any of the soil samples.

Groundwater flows in a south-southwestern direction. The data suggests that at Location No. 3 (the hydraulically upgradient location) the upper and lower water bearing units are hydraulically connected. However, the upper and lower water bearing units are not hydraulically connected in the general site area. The results of the investigation suggest that an aquitard, or confining clay layer, separates the two units. Also, heavy seasonal watering of plant material stored at the site via an underground irrigation system may enhance groundwater mounding over the site. It appears that perched groundwater occurs from Location No. 5 southward.

The highest concentration of total pesticide (228 µg/L) , herbicides (2.8 µg/L) and VOCs (334  µg/L) were detected in groundwater collected from Location No. 5 (only the upper water bearing unit was sampled). Location No. 1 had detectable concentrations of total pesticide in the upper and lower water bearing unit (7 µg/L and 0.02 µg/L, respectively). Location No. 2, No. 3 and No. 4 (only the lower water bearing unit was sampled) did not have detectable levels of total pesticide, herbicides or VOCs.

Site Visit (1997):

On July 24, 1997, TSEP staff members visited the site to assess current conditions. The site remains unrestricted but access is limited by fencing and natural barriers (e.g. hedges).

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