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Cottage Grove Landfill Ecological Risk Assessment

Site Description/History

Environmental Setting

In this section, the history of the site, along with endangered species known (or suspected) to be at the site, is described. Information about the historical and current land-use, as well as types of habitats, and known or suspected sources of contamination.

Site Description

Cottage Grove Landfill consists of an inactive sanitary landfill, an operating auto parts and scrap metal salvage junkyard, a pond, and a private residence. The site is located on the southern bank of the Little Calumet River, northwest of the junction of 138th Street and Cottage Grove Avenue, Chicago, Illinois. It is bound by the river on the north and a canal and recreational marina on the west. The adjacent lands are disturbed: two neighboring landfills to the east and southeast, and a glass recycling plant to the south.

The Little Calumet River is the most important ecological resource near the landfill.

Sensitive Habitats

Palustrine wetlands were identified from the Lake Calumet and Blue Island wetlands maps. A small (0.4 x 0.04 mile) emergent vegetation wetland is as close as 0.15 miles (mi) to the south and southwest of the site, but is upgradient of the reported ditch flows and is mainly situated on the opposite side of the glass recycling plant. A small (0.4 x 0.08 mi) temporarily flooded mixed forest and emergent vegetation wetland is across the river from the landfill, in Altgeld Gardens, west of Beaubien Preserve and south of Carver Park. This wetland is not shown as directly fronting the river, and is classified as having partial drainage. The Beaubien Preserve has approximately 0.8 mi frontage of temporarily and seasonally flooded deciduous forest and emergent vegetation wetlands on the Little Calumet, but is about 0.4 mi upstream of the site. The next closest wetlands along the river are two deciduous forest palustrine wetlands about 2.5 and 2.75 mi downstream. The former, with about 0.14 mi river frontage, is on the north bank between the river and the rail spur south of 127th Street, and is temporarily flooded. The latter, with approximately 0.5 mi river frontage, is on the south bank west of the rail bridge, part of the Whistler Preserve, Cook County Forest Preserve District, Riverdale, and is seasonally flooded.

Threatened and Endangered Species

SLERA (Screening Level Risk Assessment):
Screening Level Problem Formulation (Step 1)

For this site, the Region 5 ecologist (James Chapman) performed the Ecological Risk Assessment, including calculation of Hazard Quotients (HQ), deciding on potential assessment endpoints and conceptual site models (See ERA Guidance Step 3 for more information on endpoints and site models).

This section describes the likely sources of contamination, what the contaminants are, and what plants and animals at the site are likely to be affected by those contaminants and in what manner.

Contaminants of Potential Ecological Concern (COPECs)

Soil, sediment, surface water and groundwater were sampled August 17-18, 1995. The chemicals elevated above background concentrations are as follows:

Acetone and DHEP were eliminated from further consideration because they are common laboratory contaminants and were detected in their respective blanks. Three inorganics were eliminated because the detections are below average concentrations or within the range reported for the respective media. Groundwater aluminum and sediment antimony were eliminated because they were detected in the blanks. Because of their low toxicities and the expected dilution upon discharge to surface water, groundwater magnesium (290 mg/l) and potassium (198 mg/l) were eliminated, even though they greatly exceeded the ranges reported for freshwater (to 6 and 10 mg/l, respectively, Bowen 1979), .

A problem with the data is that most of the background samples are potentially compromised. The background sediment (ST01) and surface water (SW04) samples are located on the south bank of the Little Calumet River in the northeast section of the site, and are downstream of the discharge of the east ditch between the site and Land and Lakes No. 2 landfill. According to the Expanded Site Investigation (ESI), this ditch receives some runoff from the eastern perimeter of the site. The background groundwater sample (GW02), located between the site and the Little Calumet River, also may be in a downgradient position.

The landfill soil samples also do not appear to have been well chosen. Four low spots were identified on the landfill, but none were sampled. No soil samples were taken from any of the three ditches on the west side of the landfill (although a sediment samples was taken below one ditch)

Fate, Transport, and Ecotoxicity

Only those chemicals likely to contribute to the potential ecological risks of the site are discussed in this section. This procedure is followed because the screening level ecological risk assessment (SLERA) is based on a screening comparison of the concentrations of COPECs with benchmark guidelines by media (soil, sediment, or surface water). This numerical comparison results in a Hazard Quotient; if the HQ is greater than one, the potential for ecological risk by that COPEC is present. (See Step 2 of the Guidance for more details.)

The benchmark values are sufficiently conservative so that chemicals detected at concentrations below the guidelines are not expected to exhibit significant ecological effects, even if fully bioavailable. Since fate, transport and toxicity variables do not modify the outcome of the screening (these effects are embedded in the derivation of the particular guidelines), discussions of these processes for the chemicals screened out are unlikely to contribute meaningful information to the SLERA.

Exposure Pathways and Potential Receptors

Soil

The site provides only low quality terrestrial (land) habitat that may be utilized by common urban/suburban wildlife (e.g., sparrows, robins, blue jays, field mice or voles, etc.). The primary potential receptors of soil organic contaminants would be worm-eaters such as robins or raccoons. The pathway includes ingestion of bioaccumulated substances in earthworms and incidental ingestion of soil. Insectivory is another pathway for exposure to soil bioaccumulative contaminants (e.g., shrews). The site is by the Little Calumet River, so soil erosion could result in transport of particle-bound contaminants to the river ecosystem.

Sediment

The use of the pond by wildlife has not been investigated, but, because of its small size and location in a highly disturbed landscape, it is probably a low quality habitat. The primary receptors of pond sediment contaminants would be benthic invertebrates and rooted aquatic plants. Fish (if present) could be exposed through eating benthic invertebrates, consumption of plants, and ingestion of sediments. Terrestrial organisms (e.g., raccoons, herons, kingfishers) could be exposed to bioaccumulative contaminants through consumption of fish or larger benthic invertebrates; and insect-eating animals such as swallows and bats might be exposed through preying on emergent aquatic insects (i.e., insects that have aquatic stages in their life-cycles).

The same pathways apply to the river and harbor sediments, but with no uncertainty regarding the presence of fish.

Surface Water

The primary pathways are direct exposure, bioconcentration, bioaccumulation. Terrestrial receptors could be exposed directly through drinking, and indirectly through consumption of aquatic organisms.

Groundwater

Groundwater contaminants become potential ecological concerns when they discharge to surface waters, the Little Calumet River in this case.

 

SLERA: Risk Calculations/Exposure Estimates (Step 2)

This section includes calculations of Hazard Quotients and calculated estimations of risk by COPECs to potential receptors in different media (soil, sediment, surface water). This step involves the comparison of the concentrations of COPECs with benchmark guidelines by media (sediment, soil, surface water). If the maximum concentration of a chemical found at the site exceeds the screening benchmark guideline, then there is the potential for risk and further study is needed to clarify that risk. (See SLERA Step 2 for more information on the screening process, including calculating Hazard Quotients.)

Ecotoxicological Benchmark Values

The Screening Level Ecological Risk Assessment (SLERA) is based on a screening comparison of the concentrations of chemicals of potential ecological concern (COPEC) with benchmark guidelines by media. The following (nonregulatory) guidelines are used in this SLERA:

Exposure Estimates

The SLERA is performed with the following conservative assumptions:

1. Bioavailability - 100%, with the exceptions of the influence of sediment total organic carbon and water hardness (assumed to be 1% and 50 mg/l as CaCO3, respectively, in the absence of site-specific information);
2. Area use factor - 100%; Contaminant level - highest sample concentration.

Risk Characterization

None of the Contaminants of Potential Ecological Concern (COPECs) in surface water or groundwater exceed ambient water quality criteria protective of aquatic life (Table 4). Chromium (Cr) and Nickel (Ni) approach the Ambient Water Quality Criteria (AWQC) in groundwater, but are unlikely to present significant potential ecological risks since the dilution upon discharge to surface waters would lower the concentrations well below levels of concern.

Two COPECs, DDD and Copper (Cu), exceed the Ontario Sediment Quality Guideline lowest effect levels (LEL) in the canal west of the site (Table 5). DDD approaches the severe effect level (SEL) at that location. There are no exceedances for the second canal sediment sample.

Several PAHs meet or exceed the Ontario Sediment Quality Guidelines in one of the pond sediment samples (Table 5). Phenanthrene, fluoranthene, pyrene, and chrysene meet or approach the SEL; and benzo[a]anthracene, benzo[a]pyrene, and total PAHs exceed the LEL. There are no exceedances for the second pond sediment sample. Since PAHs do not biomagnify, the potential ecological risks are to the benthic organisms, fish and amphibians that might inhabit the pond. The PAHs do not present a risk to off-site ecological receptors unless the pond frequently overflows.

Uncertainty

There are several sources of uncertainty. Risks may be underestimated because of poor choice of background samples and possibly of landfill soil samples. Risks are intentionally overestimated by the conservative assumptions discussed above, and the use of generic benchmark values. The potential risks of PAHs and DDT in sediments are dependent on the assumed value for total organic carbon. Another uncertainty is the use of the site by wildlife.

Scientific-Management Decision Point (SMDP)

Potential ecological risks are associated with Polycyclic Aromatic Hydrocarbons (PAHs) in pond sediments, and with the pesticide DDD and Copper (Cu) in canal sediments. The pond contaminants do not represent a potential risk for off-site ecological receptors, because PAHs do not biomagnify and there is no on-going transport of pond contaminants to off-site areas. Although the PAHs are a potential risk for organisms inhabiting the pond, the pond appears to have limited intrinsic wildlife value.

The copper and DDD in canal sediments are potential risks to off-site ecological receptors, however, the significance of the risk is uncertain. The copper appears to be an isolated hit. DDD was also detected in low concentrations in one landfill soil sample, so it may represent a release from the site. If the total organic carbon (TOC) of the canal exceeds 1%, the sediment DDD would not present a significant ecological risk.

There does not appear to be evidence of substantial releases of contaminants from the landfill. There are isolated samples that meet or exceed benchmark values, but there is no consistent pattern to indicate major releases. A possible explanation of the isolated, but high, concentrations of PAHs in only one of the pond sediment samples is a spill or deliberate disposal related to junkyard activities. DDD may represent an ecological risk in canal sediments, but, again, the exceedance is isolated, and the significance of the risk may be overestimated by the conservative TOC assumption.

Definitive statements on ecological risk can not be made with the present data. The site does not appear to present a substantial threat to off-site ecological receptors. Additional sampling of the boundary and pond sediments with TOC analysis would help resolve the uncertainties.

Risk Management SMDP/Current Status (Step 8)

• August 1995 - Screening Level Ecological Risk Assessment completed

Links to more information on this site

• CERCLIS Hazardous Waste Sites Information: Cottage Grove Landfill

Contacts for this site

• James Chapman, Ecologist

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