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Waste and Underground Tank Management Bureau

CHS Inc. Laurel Refinery
Laurel, Montana


CHS Inc. Location Map Location Map

view across the CAMU towards construction of the refinery coker
View across the CAMU towards construction of the refinery coker (2007)


CHS Inc. Groundwater Samplings
Groundwater Sampling


LNAPL Recovery from a CAMU Monitoring Well



CHS owns and operates a 42,000 barrel per day refinery in Laurel.  The refinery has been in operation since the 1930s.  Fuel products include propane, gasoline, burner fuel, diesel fuel, asphalt, propane de-asphalted pitch, and road oil.

The original owner and operator of the Laurel Refinery was Independent Refining Company.  Farmers Union Central Exchange, Inc. (CENEX) purchased the refinery in the 1940's.  In 1998, CENEX merged with Harvest States Grain to form Cenex Harvest States Cooperatives, the current owner of the refinery.  Subsequently, Cenex Harvest States Cooperatives was shortened to CHS, Inc.  



The Resource Conservation and Recovery Act (RCRA) is the federal law which requires proper management and disposal of hazardous waste.  Hazardous waste permits are required for on-site units that are used to treat, store or dispose of hazardous waste.  Hazardous waste permits must also include provisions requiring facility-wide investigation and remediation of releases of hazardous waste or hazardous constituents.   The Montana Hazardous Waste Act (MHWA) is the State equivalent of RCRA.

The State of Montana issued a hazardous waste permit to CHS, Inc. in 1991 for the closure and post-closure care of the facility's two inactive land treatment units.  In addition, because the State of Montana was not yet authorized by EPA to implement facility-wide corrective action, EPA issued a federal permit to CHS that same year.  The EPA permit required facility-wide investigation of releases and potential releases of hazardous waste or hazardous constituents.

In 2000, the State was approved by EPA to implement facility-wide corrective action.  This enabled Montana Department of Environmental Quality (MDEQ) to combine requirements for closure and post-closure care of the land treatment unit with requirements for facility-wide corrective action in a single permit, which was issued in 2002.  



Facility-Wide Corrective Action

EPA conducted a RCRA facility assessment (RFA) at the Laurel refinery in 1989.  The RFA identified 32 areas needing further investigation for potential contamination in soils and groundwater.  CHS conducted a RCRA Facility Investigation (RFI) from 1991 to 2006, which identified the nature and extent of hazardous constituents in soils and both ground and surface water at the facility.  In addition, a baseline risk assessment was conducted to determine the areas of contamination at the facility which posed risk to human and ecological health.

Concurrent to the RFI work, CHS implemented Interim Measures (IM) at the refinery boundary to halt off-site migration of contaminants in groundwater.  The IM technologies include air sparging fences, pump and treat well systems, and a slurry wall barrier.  CHS also implemented measures, in the form of a pump and treat system, to stabilize and remove Light Non-aqueous Phase Liquid (LNAPL) from the groundwater in the refinery interior.

CHS conducted a Corrective Measures Study (CMS) to evaluate remedial technologies and approaches for remediating contaminated media at the facility.  CHS then submitted a CMS report to the MDEQ, which is currently under review.  Following review of the CMS report, the MDEQ will choose a remedy for the facility and develop a draft Statement of Basis which will outline the corrective measures CHS must take to implement a remedy for contamination at the facility.  The draft Statement of Basis and Environmental Assessment will be issued for public comment.  After consideration of comments, the MDEQ will finalize selection of a remedy and will modify the CHS hazardous waste permit to include requirements for implementing the remedy.  CHS will then implement the remedy through a Corrective Measure Implementation work plan.  

Regulated Units

An area in the southwestern portion of the refinery was used from 1965 to 1988 to treat refinery wastes.  This area is comprised of two land treatment units, the Old Landfarm (OLF) and the New Landfarm (NLF).  The OLF was approximately 14.5 acres and was used from 1964 through 1981.  The NLF was approximately 8 acres and used from 1981 through 1988.

CHS began closure of both land treatment units in 1991, following the closure requirements as outlined in the closure/post-closure permit.  The permit established standards for allowable concentrations of hydrocarbon and metal constituents in the soils.  Soils with constituents above the standard were excavated in phases and placed on areas of the units where soil standards had been met.  Each excavated soil volume (or 'lift’) was then land treated until standards were met for that lift.  In 2002, MDEQ, at the request of CHS, designated the OLF as a Corrective Action Management Unit (CAMU).  The NLF was clean-closed in 2006.

Groundwater Corrective Action   At the CAMU,  Light Non-aqueous Phase Liquid (LNAPL) is present on the surface of the groundwater beneath the CAMU.  The LNAPL consists of hydrocarbons which migrated through the land treatment soils into the groundwater.  The LNAPL ‘floats’ on the groundwater surface and can be recovered through pumping.

As a corrective measure to address the LNAPL, CHS installed a barrier wall system to contain the contamination.  The barrier wall system is composed of a bentonite slurry wall two feet wide and 15 feet deep at the downgradient edge of the CAMU.  The barrier wall stops off-site contaminant migration and ponds the LNAPL along the upgradient edge of the wall.  The LNAPL is pumped into recovery wells and recycled back into the refinery’s petroleum refining process.  Monitoring wells are located south (down gradient) of the barrier wall and are sampled regularly.

Corrective Action Management Unit (CAMU)  CAMUs are physically distinct geographic areas within a facility designated for managing, treating or disposing remediation wastes generated by corrective action or cleanup at a facility.  CAMU rules are found in 40 CFR 264.552 and are incorporated by reference in ARM 17.53.801.

The CAMU at the CHS refinery may be used to land treat and dispose of petroleum-contaminated soil generated during corrective action activities.  Types of contaminated soil expected to be treated include soils from corrective measures required by facility-wide corrective action, and soils from remediation of spills and/or excavation of contaminated soils found during facility construction or maintenance activities.

The CHS hazardous waste permit places conditions on how CHS must operate and maintain the CAMU.  Concentration limits of hazardous constituents are designated for contaminated media and CAMU soils.  In addition, soil nutrients (specifically carbon, nitrogen, potassium, and phosphorous) and pH must be kept within certain limits.  The permit also sets requirements for tillage, as well as weed and blowing soils control and minimization.  Soil and groundwater monitoring must be conducted to guard against migration of contaminants into deeper soils or groundwater.  The permit also contains requirements that guard against migration of contamination into deeper soils or groundwater.     



DEQ Contact: 
Becky Holmes, Environmental Science Specialist
Montana Department of Environmental Quality
P.O. Box 200901
Helena, Montana 59620-0901