Solhaus site

solaus-greiner-construction-530The Minnesota Pollution Control Agency (MPCA) staff from the Petroleum Brownfields (PB), the Voluntary Investigation and Cleanup (VIC) and Superfund programs provided technical oversight of the environmental investigation, cleanup and redevelopment of the Solhaus/Gopher Oil-Delaware/Huron Flats Site.

History

The site has been developed since the late 1880s. Until the 1940s, the site was used by a paint-mixing company and storage warehouse. The site was redeveloped in the 1940s by Gopher Oil for petroleum storage and distribution. Gopher Oil’s operations ceased in the 1980s. Before it was cleaned up and redeveloped, the site was occupied by an office building, cold storage warehouse, and surface parking.

Environmental issues

Site soils were investigated in several phases by the Superfund program in the 1990s and 2000s.

Soils at the site soils were contaminated with 1,1,1-trichloroethane (1,1,1-TCA), trichloroethene (TCE), lead,
polychlorinated biphenyls (PCBs), tetrachloroethene (PCE), mercury, and petroleum compounds. PCBs and petroleum were considered the main contaminants of concern.

PCB concentrations in the soil were considered hazardous and the site was listed on the Minnesota Permanent List of
Priorities (PLP) database through the Superfund Program for both hazardous substances and petroleum.

Site groundwater was contaminated with TCE, vinyl chloride, and petroleum compounds.

Site soil vapors were contaminated with cis-1,2-dichloroethylene, 1,1,1-TCA, TCE, vinyl chloride, and petroleum
compounds.

The cleanup process

  • Buildings on the site were demolished.
  • The contaminated soils at the site were excavated to depths of 18 to 20 feet below ground surface and taken to an approved landfill. Removed soils included approximately 17 tons of PCB-impacted soils and approximately 19,220 tons of predominantly petroleum-impacted soils.

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Redevelopment of the site

  • A six-story, 75-unit student apartment building with parking on the ground floor was built on the site.
  • A passive ventilation system was installed under the building to reroute any potential petroleum vapors and keep them from entering the housing area.

Environmental and economic benefits

  • Hazardous and highly contaminated soil was removed from the site and no longer acts as a source for groundwater contamination.
  • Increased tax revenue from the new, 75-unit apartment building for students.

Assurances received

September 21, 2010: VIC No Association Determination
July 29, 2011: VIC No Further Action Determination
September 11, 2011: PB Response Action Plan Completion
November 7, 2011: Delisting from the State Superfund List

Institutional controls

July 14, 2011: Affidavit Concerning Real Property Contaminated with Hazardous Substances. This affidavit serves as a notification that contamination remains at depth and that groundwater beneath the site is contaminated.

Project partners

  • MPCA VIC program staff included Lynne Grigor and Shanna Schmitt; PB program staff included Amy Miller and Tom Higgins, and Superfund program staff included Steve Schoff and Dave Scheer.
  • Develope: Curt Gunsbury of Solhaus Associates, LLC
  • Environmental consultant: Dave Vieau of Vieau Associates, LLC
  • Public funding sources included Hennepin County, the Minnesota Department of Employee and Economic Development, and the City of Minneapolis.