Jargon Translator

Clark Fork Superfund Terms

Action Level: The level or concentration of a harmful or toxic substance (like lead or arsenic) at or above which remedial or regulatory action is required. The Record of Decision defines these levels for the Clark Fork Superfund cleanup.

Alluvium Borrow: Material such as sand and gravel removed from one area of the floodplain ("borrowed") to replace contaminated materials removed in another area during cleanup.

Avulsion: Refers to when a river leaves its existing channel and forms a new channel. In the Clark Fork floodplain, avulsions can cause erosion of contaminated soils into the river, so cleanup plans are often designed to minimize this risk.

Borrow Area: An area from which alluvium or vegetation is borrowed for use in a treated area of the floodplain.

Brush Matrix: A mixture of brush and dormant willow cuttings that may also incorporate dense willow clumps, juniper trees, or root wads. These matrices are designed to protect riverbanks subject to high flow rates and also to create overhanging bank habitat.

Channel Migration Zone (CMZ): The area in a floodplain where a river or stream is expected to flow over time, either due to forces such as gravity and topography, or other factors such as hardened (ie, riprapped) banks, or climate-related changes.

Clark Fork Five: Copper, Cadmium, Zinc, Lead, & Arsenic, the main contaminants of concern found in the Clark Fork River floodplain.

Consent Decree (CD): A legal agreement entered into by the U.S. government (through EPA and Dept. of Justice) and the Potentially Responsible Parties. CDs are lodged with a federal court and are the enforcement agreements EPA uses to implement the remedial action (cleanup) at a Superfund site. The Clark Fork Superfund complex involves multiple Consent Decrees.

Constructability: In the Strategic Plan, refers to the ease, feasibility, cost effectiveness, and other factors of a proposed phase cleanup design. This is one of the criteria DEQ uses to determine the priority rank of each phase (higher priority given when multiple phases can be completed with combined infrastructure to save costs and minimize disruption).

Cubic Yard: Often used to measure volume of wastes in the floodplain. Equal to a 3x3x3 cube. A standard pickup truck holds about 2.5 cubic yards.

Design Review Team (DRT): Creates the detailed plans for cleanup of each phase. CFRTAC (and its technical advisor) serves as a member of this team alongside cleanup agency staff. The DRT can also include local government representatives and members of the public.

Entrainment: In the Strategic Plan, refers to the potential for contaminated sediments to be picked up by and incorporated into the river, such as during a flood event. This is one of the criteria DEQ uses to determine the priority rank of each phase (higher priority given in high erosion areas where entrainment is a greater risk).

Explanation of Significant Differences: This document explains modifications made to the original remedial action outlined in the Record of Decision for the Clark Fork River cleanup.

Floodplain Connectivity: The connection of a river to its adjacent floodplain. When connected (as opposed to being confined in an incised channel), the river can reach the floodplain during high water, which provides moisture and nutrients to vegetation and helps recharge groundwater. This connectivity is critical to the health of the ecosystem.

Geomorphology: Sometimes called fluvial or hydro- geomorphology, this refers to the interaction of a river with the land around it, the sediment it carries and how, and how these interactions change in response to flow rates, channel shape, human intervention, and other variables. Cleanup and restoration activities can greatly impact the river's geomorphology.

In-situ: Refers to something situated in its original place. Cleanup documents may refer to "in-site treatments," which means contaminated sediments would be treated in place instead of being removed.

Opportunity Ponds: Contaminated wastes removed from the floodplain during cleanup will be disposed of at the 3,000-acre Opportunity Ponds repository near the town of Opportunity, Montana.

Potentially Responsible Party (PRP): Any company and/or individual(s), including owners, operators, transporters or generators, that are potentially responsible for contamination at a Superfund site. For the Clark Fork cleanup, the PRP is the Atlantic Richfield Company (ARCO), which, as of 2000, is a subsidiary of British Petroleum and is sometimes referred to as BP-AR.

Preliminary Design Plan (PDP): The initial, or draft plan for how a given reach of the Clark Fork will be cleaned up. Based on input from landowners and other entities, such as CFRTAC, or on new data or findings, the preliminary design will be adjusted before a final plan is completed.

Q1.5, Q10: Refers to the recurrence interval (number of years) between flood events on the river. A "Q1.5 discharge" refers to a flood event expected to occur every 1.5 years, or 2 out of every 3 years. A "Q10 discharge" refers to a 10-year flood event, or a flood with a 10% chance of occurring in any given year. For example, a plan for a certain phase of the Clark Fork cleanup may refer to features designed to "resist erosion up to the Q10 discharge," meaning they could withstand a 10-year flood.

Record of Decision: (ROD): The document describing the cleanup method chosen by EPA to be used at a Superfund site. A ROD usually includes a site history, description of cleanup alternatives, rationale for the chosen cleanup method, cost estimates, and a summary of public comments and EPA's response to them. The Clark Fork cleanup ROD was signed in 2004.

Remediation: Refers to the cleanup of a damaged or contaminated area. This is different from "Restoration," which refers to "repairing" the damaged or contaminated area. The Clark Fork basin is undergoing both remediation and restoration, with DEQ being responsible for remediation activities.

Removal Boundary: In a cleanup design, the area determined by DEQ where contaminated sediments will be removed. This boundary is determined by factors such as the Channel Migration Zone (CMZ), location of slickens, and other factors, such as areas where it is desirable to preserve existing vegetation.

Restoration: Refers to "repairing" damaged or contaminated natural resources and enhancing or creating aquatic and terrestrial habitats. The Clark Fork basin is undergoing both remediation and restoration, with NRDP being responsible for restoration activities.

Risk Concentration Level: For a given contaminant or a combination of contaminants, the level or concentration at or below which EPA considers risks to the environment and human health (such as causing illness or increasing the probability of cancer) to be very small. This level can vary depending on expected exposure pathways, who is expected to use a given area, how they will use it, how long or frequently they will use it, and other variables. In the Clark Fork cleanup, this level plays a significant role in determining how and to what extent a given phase, area, or reach of the river will be cleaned up.

Slickens: Refer to areas in the Clark Fork floodplain that are highly contaminated with heavy metals-laced mine waste. Typically devoid of vegetation, slickens often appear brown, orange, and teal, and are a major source of contamination reaching the river during rain and flood events. (To see examples of slickens in the Clark Fork floodplain [as of 2021 and earlier], see the Clark Fork River Slicken Assessments.)

Swale: A sunken or marshy area in the floodplain. Swales are typically shallow and aid in slowing down or redirecting runoff. Existing swales are incorporated into some Clark Fork cleanup designs, and new swales can be created as part of cleanup activities to enhance habitat.

Vegetative Borrow: Plants and shrubs removed from one area of the floodplain ("borrowed") to help revegetate areas where contaminated soils and vegetation have been removed.

Acronym Decoder

ARCO: Atlantic Richfield Company
BP-AR: British Petroleum-Atlantic Richfield
BMP: Best Management Practices
CERCLA: Comprehensive Environmental Response, Compensation and Liability Act (aka: "Superfund")
CFR: Clark Fork River
CFROU: Clark Fork River Operable Unit
CMZ: Channel Migration Zone
COC: Contaminant of Concern
DEQ: MT Dept. of Environmental Quality
DRT: Design Review Team
EPA: Environmental Protection Agency
FWP: MT Fish, Wildlife & Parks
NRDP: Montana Natural Resource Damage Program
PPM: Parts per Million
PRP: Potentially Responsible Party
ROD: Record of Decision
SBC: Silver Bow Creek
WSP: Warm Springs Ponds

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Clark Fork Superfund Terms

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