UPDATE
March 8, 2013

Over 1 year after the release of a gasoline-type refinery product known as reformate into Sand Creek located in Commerce City, Colorado, cleanup progress continues. Suncor Energy Inc. (Suncor) and its contractors are responsible for designing, installing, and maintaining a series of remedial systems to control contaminant migration and address areas which have already been impacted. The Colorado Department of Public Health and the Environment (CDPHE) is the lead regulatory agency who ensures the cleanup measures are timely and appropriate. The Region 8 Environmental Protection Agency (EPA), who provided the initial emergency response, continues to provide technical support and oversight for the project.

Suncor has implemented several remedial systems to contain and recover reformate from the subsurface. To date, over 1.1 million gallons of reformate have been successfully recovered. The vast majority of this material has been recovered from the subsurface within the Suncor refinery property, preventing it from migrating offsite. Remedial operations have been constructed to address three different contaminant phases: pure product reformate, dissolved phase reformate, and soil vapor.

Pure Product Reformate – a gasoline type liquid (reformate) which has settled atop the water table.

• Barrier Wall Systems – also referred to as vertical engineered barriers.
  More Information on Barrier Wall Systems (PDF) (2 pp, 961K)
  • Barrier Walls to Bedrock - Barrier walls were installed prior to the 2011 release around a portion of Suncor’s property. These systems physically block migration of groundwater or any contaminants by creating a low permeability section tied into bedrock. In total, there is over 5,300 feet of barrier wall comprised of bentonite clay which is tied into bedrock. These walls also help to better route contamination toward remediation systems.
  • Hanging Barrier Wall and Product Recovery Pumping – Multiple hanging wall systems were installed in 2012. This barrier system differs from the system previously described because it is not tied to bedrock. Considering the reformate floats atop the water table this wall functions as a skimmer. In other words, this wall blocks the first several feet of the water table and works in parallel with a recovery trench and groundwater pump system. When the pure reformate is recovered it is typically recycled back into the refinery processes.
• Enhanced Fluid Recovery Systems (EFRs) – These systems utilize a specialized pumping apparatus which can remove pure product reformate floating on top of the water table, vapors emanating from that product, and dissolved phase product which have migrated into groundwater. Once pumped, the recovered reformate is taken to Suncor facilities for additional refining. Contaminated groundwater is typically treated with an air stripping unit and vapors are treated with activated carbon filters or combustion units.
  More Information on Air Stripping (PDF) (2 pp, 1.2 MB)
  More Information on Activated Carbon Treatment (PDF) (2 pp, 1.0 MB)

Dissolved Phase Contamination – reformate components which have dissolved into the groundwater.

• Air Sparging / Soil Vapor Extraction (AS/SVE) – This system has been implemented in numerous locations to address contaminant impacted subsurface areas. Air sparging units pump air into the water table which volatilizes reformate compounds. These compounds are then captured using a vacuum created by soil vapor extraction wells equipped with an air pollution control device. This technology can be effective for pure phase reformate as well as the dissolved phase.
  More Information on AS/SVE (PDF) (2 pp, 1.2 MB)
• Groundwater Monitoring / Pump and Treat - Pump and treat has been in use on Suncor property for many years and was being phased out until the seep was discovered in November 2011. Since then, this system was rehabilitated and enhanced with additional extraction and monitoring points to capture and recover as much contamination contained on Suncor property as possible. Suncor has also been working with surrounding property owners to ensure any contamination originating from the initial release that has migrated offsite is contained and remediated. In particular, Suncor has been working with the neighboring Denver Metro Wastewater Reclamation District (Metro). Several facility expansion projects on Metro’s property required dewatering operations which have altered groundwater flow in the area. To be sure the dewatering operations do not create a groundwater gradient that will allow dissolved phase contamination to travel further into Metro property, numerous monitoring wells have been installed. Suncor has also constructed a temporary treatment plant specifically to treat groundwater from Metro’s construction dewatering operations (pictures below).
  More Information on Pump and Treat (PDF) (2 pp, 728K)

Suncor Temporary Treatment Plant

Soil Vapor - volatile reformate components which change phases from liquid to gas and reside in soil pore space.

• Vapor Intrusion Mitigation – Indoor air sampling was conducted in buildings which were potentially affected by vapors emanating from the contaminant plumes. To mitigate this exposure pathway in buildings where sampling results indicated a presence of contamination, both sub-slab depressurization and utility conduit depressurization systems were installed. These systems route contaminated vapors away from indoor air and treat vapors with air pollution controls similar to SVE systems previously described. Ongoing air monitoring in buildings fit for depressurization systems as well as other occupied buildings without systems ensures efficacy of the remedy and safety of employees.
  More Information on Vapor Intrusion Mitigation (PDF) (2 pp, 778K)

The described technologies are dynamic and natural variations in the subsurface amongst other factors require the remedial systems to be constantly optimized. This optimization will help to facilitate the most thorough cleanup possible. Looking forward Suncor plans to implement more AS/SVE systems to contain and recover product.

UPDATE
December 6, 2011

EPA continues to respond to a seep of a gasoline-type material into Sand Creek near its confluence with the South Platte River in Commerce City, Colorado. As of December 6, approximately 3,500 gallons of gasoline-type material has been recovered during the operation, and the isolated area of Sand Creek where the seep is occurring has been largely contained.

A 220-foot interceptor trench was completed on December 3 between the seep and the creek to prevent additional material from entering Sand Creek. This trench appears to be effective in containing and collecting residual seeping material. Current information indicates that the material is migrating from the Suncor refinery, traveling under the Metro Wastewater Treatment Facility and appearing on the shore of Sand Creek.

There continues to be no evidence or reports of impacts to downstream water users of the South Platte River or to wildlife in the affected area. Initial results from samples collected from in impacted areas along Sand Creek from Tuesday, November 29 through Friday, December 2 confirm the presence of benzene as well as toluene, ethlylbenzene and xylene. EPA believes benzene concentrations are largely a result of the disturbance from cleanup crews working in and near the river at the seep location and expects levels will fluctuate as cleanup actions continue. The cold temperature also reduces the evaporation rate of contaminants, which may be a factor in day-to-day fluctuations. We expect these levels will decrease once we complete the removal of material from a sandbar and other residual material between the trench and Sand Creek.

Summary of EPA Surface Water Sampling Results

Background

On November 28, EPA was notified of a sheen and associated gasoline-type odor reported by a fisherman on Sand Creek. EPA responders quickly deployed to the site and identified a stretch of the stream bank where a gasoline-like material was seeping into the stream. EPA contacted Suncor, owner of a refinery adjacent to the creek, and requested that they initiate a response.

Suncor response teams and contractors immediately deployed containment and absorbent booms throughout the stream and worked overnight to create an earthen and sandbag dam around the shoreline area where the gasoline-like material was seeping. The dam has successfully contained nearly all of the material seeping from the shoreline. Containment and absorbent booms are still deployed in several locations downstream of the seep to ensure any residual material that is not contained by the dam is collected and recovered. Material is being vacuumed off into trucks as it accumulates. Suncor is also monitoring air quality at the site.

Suncor has taken response actions to capture material and prevent the flow of material into the creek. This includes damming the shoreline of Sand Creek where material is seeping and constructing an interceptor trench that is expected to act as a barrier to stop the flow of material into the creek. Suncor and the Colorado Department of Public Health and Environment (CDPHE) are continuing to investigate the source of contamination. EPA will continue its oversight of response actions as Suncor continues to implement the cleanup.

Below: image of seep location and boom material in Sand Creek, December 1