No Further Action Needed at Former UST Facility, Former Smith Farm Service (Walthill Standard) Underground Storage Tank Project, Walthill, Omaha Reservation, Nebraska
The U.S. Environmental Protection Agency (EPA) Region 7, in consultation with the Nebraska Department of Environmental Quality (NDEQ), has determined that no further action is needed at the former Smith Farm Service (Walthill Standard) underground storage tank site.
EPA invites the public to review decision documents included in the Administrative Record file. The Administrative Record file is located at:
Walthill Public Library
Attn: Nola Briggs
222 Main St.
Walthill, NE 68067-0466
Hours of operation: Mondays and Thursdays from 12 p.m. to 5 p.m.
The Administrative Record file will be available for review from September 20 through September 28, 2012.
The former Smith Farm Service (also known as Walthill Standard) operated as a gas station until the early 1990s. The underground storage tanks located at this facility were removed on June 13, 1991. During the removal process, a release of petroleum products (gasoline and diesel) was discovered. As a result, the former owner of the facility, Richard Smith, was compelled by EPA and NDEQ to conduct an initial Tier 1 investigation of the site.
The Tier 1 investigation was completed on July 27, 2001, and it indicated that levels of benzene and n-hexane (two gasoline constituents) in the subsurface soil and groundwater were above NDEQ’s Risk-Based Screening Levels for enclosed space vapor inhalation exposure pathways. Therefore, it was determined that the site may pose an unacceptable risk to human health for vapor exposure through inhalation.
As a result of the Tier 1 investigation, on April 27, 2007, EPA compelled Mr. Smith to conduct a Tier 2 investigation at the site. The Tier 2 investigation was completed on November 7, 2008. The Tier 2 investigation consisted of additional soil and groundwater sampling that would allow for a more complete risk-based corrective action analysis of the site, and help determine what kind of remedial action was needed to clean up the site.
The Tier 2 investigation established that only benzene and n-hexane in soil exceeded NDEQ’s Tier 2 Site-Specific Target Levels (SSTLs) for enclosed space vapor inhalation exposure pathways. The benzene and n-hexane levels in the groundwater were below the SSTLs. Therefore, only the subsurface soil had contamination that posed an unacceptable risk to human health for vapor exposure through inhalation.
As a result of the Tier 1 and Tier 2 investigations, in August 2010, EPA instructed Mr. Smith to conduct corrective action activities at the site that consisted of the excavation and disposal of the contaminated soil, and confirmation sampling and testing to verify that the bulk of the contaminated soil was successfully removed below the established SSTLs for the site. Starting on April 11, 2011, approximately 210 tons of contaminated soil was excavated and disposed of at the L.P. Gill Landfill in Jackson, Nebraska.
Confirmation soil samples were collected from the excavation area before it was backfilled with clean soil, to confirm that the bulk of the contaminated soil was removed. The soil inhalation SSTL for benzene was exceeded in all except for one of the confirmation samples collected from the excavation area. However, EPA determined that the confirmatory samples may have been compromised by the flooding of the excavation area caused by a water line that was breached during the excavation.
In order to verify that the remedial excavation was successful in mitigating the contamination at the site to the Tier 2 SSTL levels, EPA instructed Mr. Smith to conduct additional confirmation sampling to verify the effectiveness of the remedial excavation activities. The additional sampling activities consisted of collecting one sub-slab vapor sample from inside the former Smith Farm Service facility (Walthill Standard), and soil gas samples at three locations between the southern limit of the excavation and the Martial Arts Academy. The additional sampling activities were conducted on March 7, 2012.
The results of the sampling and analysis indicated soil gas levels for benzene were, in fact, well below the SSTLs for the site. Therefore, the site did not present unacceptable risks to human health and the environment.
Based on the excavation and removal activities, as well as the Tier 1 and Tier 2 assessment results, EPA, in consultation with NDEQ, determined that the site no longer represents an unacceptable risk to human health and the environment and, therefore, no further action is recommended for the former Smith Farm Service (Walthill Standard).
FOR MORE INFORMATION
EPA maintains a mailing list of interested individuals that is used to send updated information throughout the process.
If you have questions about EPA’s decision, or want to be added to the mailing list, please contact:Wilfredo Rosado-Chaparro
EPA Region 7 (AWMD/STOP)
901 North 5th Street
Kansas City, KS 66101
Phone: (913) 551-7944
EPA Region 7 (OPA)
901 North 5th Street
Kansas City, KS 66101
Phone: (913) 551-7253
Toll-free: (800) 223-0425