Region 8

Yellowstone River Spill: Data

On this page:

Crude oil data
Soil data
Air data
Water data
Sediment data

View EPA sampling locations and results

Instructions: To use the data mapping application, please click on the image above to launch the viewer in your web browser, and then zoom into the area of interest. When you see the sample icon you are interested in, click on the icon to bring up the sample name, which includes the date the sample was collected, along with a description and a link to the analytical data. If you want to see the analytical data, click on the link to open a window that presents the results along with some explanation of the analytical results qualifiers (U, J or B).

Crude Oil Data

EPA collected two samples of crude oil from valves on the Silvertip Pipeline in the week following the spill. The first sample (SPPR03) was collected near the Conoco Refinery on the north side of the Yellowstone River in Billings, and the second sample (SPPR04) was collected at the block valve on the south side of the Yellowstone River near Riverside Park in Laurel. These samples were analyzed using methods designed to identify the various constituents of the oil. Other methods were used to identify any constituents that might pose a threat to human health in the hours immediately following the spill and whether there were any persistent constituents, such as metals, that might pose a threat to the environment. These results are also consistent with the information provided by the responsible party, ExxonMobil, regarding the assertions that the released oil was a sour medium crude.

The Silvertip Pipeline Crude Oil fact sheet linked below explains the analytical findings for the samples collected from the pipeline and compares these results with those of samples of weathered crude collected from environmental media downstream. Additionally, the analytical laboratory summary reports for the crude oil samples split between EPA and the Montana Department of Environmental Quality (DEQ) are also linked below, but this data is inherently technical and may require scientific interpretation. Please refer to the fact sheet for the interpretation.

Fact Sheet: Summary of Pure and Weathered Crude Oil Samples (PDF)
(6 pp, 843K)
EPA Crude Analysis Report (PDF) (72 pp, 1.6MB)
DEQ Crude Analysis Report (PDF) (45 pp, 1.4MB)

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Soil Data

EPA and the Montana Department of Environmental Quality (DEQ) conducted soil sampling in areas impacted by the Yellowstone River Oil Spill. Samples were collected from areas on public and private property where there was visible oil up to two weeks after the spill occurred, but before any cleanup crews had removed contaminated soils. These sampling results are an important picture of the degree of impact and the petroleum constituents that remain after many weathering processes have taken place. Samples were tested for volatile organic compounds (VOCs), semi-volatile organic compounds (SVOC), extractable petroleum hydrocarbons (EPH), and volatile petroleum hydrocarbons (VPH). The sample analysis results are being provided to the respective property owners.

When crude oil is released and exposed to the environment, many of the smaller, lighter hydrocarbons evaporate into the air within the first 24-48 hours. Evaporation of the lighter compounds leaves behind the medium and heavier portions of the oil that is now the focus of the cleanup effort. The potential for human exposure to these compounds was closely monitored during the first weeks of the spill to ensure that all appropriate actions were taken to protect human health and the environment. The results of the soil samples will greatly assist with assessment and cleanup efforts because they are used to determine where oil was transported, what compounds are present in the environment, and what ecological risk they may pose. Confirmatory samples will likely be collected following cleanup to compare to this data.

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Air Data

Air monitoring using real-time instruments that look for volatile organic compounds continue to show no detections in ambient air along the Yellowstone River.

Additionally, six air samples were collected for a 24-hour period at several outdoor locations along the Yellowstone River. These samples were sent to the laboratory for analysis, and all results are posted here. The data show that there continues to be no public health concerns resulting from the release of oil into the river. Two compounds (naphthalene and methylene chloride) were detected at concentrations slightly above the levels used to evaluate potential human health risks. However, naphthalene concentrations are similar to concentrations in the area prior to the spill and methylene chloride is not a compound associated with the oil spill. No other compounds were detected above levels which could pose a risk to human health.

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Water Data

Surface water sampling conducted by EPA and DEQ between Laurel and Miles City, Montana indicates there are no petroleum hydrocarbons above drinking water standards in that region. Six surface water samples were collected in the days after the spill to determine the amount of petroleum-related compounds that may be present in the river water. Samples were tested for volatile organic compounds (VOCs), semi-volatile organic compounds (SVOC), extractable petroleum hydrocarbons (EPH), and volatile petroleum hydrocarbons (VPH).

The results of river water analysis are consistent with a release to a rapidly flowing river in that no petroleum-related compounds were identified.

A total of 33 drinking water samples were collected from private residences along the Yellowstone River in the days following the spill. These samples were collected to verify that private wells were not impacted by the spill. The samples were analyzed for constituents of concern related to the crude oil release.

Only one compound in one drinking water sample was detected. This sample was from a well known to be installed in a contaminated groundwater plume associate with an identified EPA Superfund site. This compound (trichloroethylene) is not associated with petroleum products.

In addition, 14 samples were collected from irrigation wells on private property. These samples were collected to verify that these groundwater irrigation wells were not impacted by the spill. The samples were analyzed for constituents of concern related to the crude oil release.

No compounds of concern were detected in any of the irrigation wells samples.

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Sediment Data

EPA and the Montana Department of Environmental Quality (DEQ) conducted sediment sampling in areas impacted by the oil spill. Samples were collected from submerged sediments near the shorelines where there was visible oil up to two weeks after the spill occurred. These samples were collected to determine the amount of petroleum hydrocarbons that might have ended up in river sediments due to the violent mixing of the water column during the flooding. These sampling results are an important part of evaluating where the crude oil ended up in the environment and how it may breakdown due to natural processes. Samples were tested for volatile organic compounds (VOCs), semi-volatile organic compounds (SVOC), extractable petroleum hydrocarbons (EPH), and volatile petroleum hydrocarbons (VPH).

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Maps of sampling locations

EPA initially posted our sampling locations and results using the maps below. We have since upgraded our data posting capabilities but are providing these original maps for historical purposes.