Wood River Refinery West Fence Line Environmental Investigations: Roxana, Illinois (Illinois EPA Update #2)

              State of Illinois
Pat Quinn, Governor
Illinois Environmental Protection Agency
Lisa Bonnett, Interim Director
Illinois
Environmental
Protection Agency
Office of Community Relations
1021 N. Grand Avenue East
Springfield, Illinois 62702
May 2011
Illinois EPA UPDATE #2
Wood River Refinery West Fence Line Environmental Investigations
Roxana, Illinois
Background:
Illinois Environmental Protection Agency (Illinois EPA) is requiring Shell Oil Products US (Shell) to investigate and adequately remediate hydrocarbon contamination along the western property boundary of the ConocoPhillips Wood River Refinery (WRR) and a benzene release which occurred near the intersection of Rand Ave. and Central St. The potentially affected area of Roxana is bounded to the north by First St., to the south by Rand Ave., to the west by Central St., and to the east by Chaffer St. Shell owned the refinery for many years and is responsible for addressing certain historical environmental issues there.
Shell has been conducting environmental investigations in this area and has recently found high concentrations of certain hydrocarbons, including benzene, as vapors in subsurface soils near the refinery boundary and under the Roxana Public Works buildings, south of Eighth St. Dissolved hydrocarbons and free petroleum product have been found in groundwater both at the refinery and off-site near the western fence line. These volatile chemicals have the potential to migrate through soils as vapors and enter buildings through earthen crawlspaces, cracked floor slabs, or cracks in basement walls. This migration of contaminant vapors into buildings is referred to as “vapor intrusion.” Because of the potential for vapor intrusion, the Illinois EPA has required Shell to investigate whether hydrocarbon vapors have entered buildings in the eastern part of this area and remedy any cases they find.
Residential Vapor Intrusion Investigation Results:
To determine if vapors are entering buildings from the soils below, Shell is sampling the Roxana Public Works facilities and several homes close to the fence line and near where soil and/or groundwater contaminant concentrations are highest. Shell collects three soil gas samples from below each building (these samples are referred to as “sub-slab” samples), as well as indoor air samples from the basement and first floor at all participating homes and buildings. An outdoor air sample is also collected during each sampling event.
This sampling began in April and is continuing. No indoor air problems have been found at most of the homes. However, the sub-slab air samples at three homes contained significant concentrations of benzene or other hydrocarbon vapors (mainly methane). So far, low concentrations of hydrocarbons have also been found in the basement air of one of these three homes; this is suggestive of vapor intrusion and re-sampling of this home is planned. Shell is required to take steps to reduce the relatively high levels of contaminants detected as vapors in the soils beneath these homes and is also required to sample neighboring homes, if possible, to determine if additional homes are potentially affected.
To date, the concentrations of hydrocarbon vapors detected indoors at these homes would not be expected to cause immediate adverse health effects. However, when high concentrations of hydrocarbon vapors are found in soils below a home, there is potential for vapor intrusion and subsequent safety and health hazards. This concern led the Illinois Department of Public Health (IDPH) to recommend that residents of homes with relatively high levels of contaminants detected in sub-slab samples not sleep in their basement bedrooms until sample results indicate sub-slab vapor concentrations have been adequately reduced. Shell has been offering alternative housing to those residents. If, during future sampling, petroleum vapors are found to be intruding into a home at levels that pose a risk to human health, Shell will extend the offer of temporary alternative housing to the home’s residents until an adequate remedy is in place.