Retail Gasoline Station, Grantville, PA (Ongoing Groundwater
Cleanup)
In April 2007, HES responded to an unleaded gasoline
release from a ruptured underground product supply line. Immediately action contained
the release and prevented impact to downgradient wetlands and a stream.
The release was estimated to be approximately 1,800
gallons which impacted surface and subsurface soils and groundwater. Soil impacted in the area immediately downgradient of
the release was excavated and disposed.
At the request of the PA DEP a site characterization
investigation was performed. Twenty-eight soil
borings and 10 monitoring wells were installed to delineate the extents
of soil and groundwater contamination. Surface water,
and two distinct aquifers were impacted by the release. A groundwater
remediation system is currently in operation to address the multiple
impacts.
Truck Stop,
Frystown, PA Closure (December 2009)
During the closure of two
30,000-gallon diesel underground storage tanks, contaminated soil and
water was encountered. Contamination originated
at numerous locations where piping leaks had occurred within the former
tank systems. Interim remedial actions involving
the excavation of contaminated soil and removal and disposal of
contaminated water were performed.
Forty
soil borings were extended to delineate the extent of soil contamination
remaining on the property. In addition, fifteen
monitoring wells were installed. A 1.2 acre plume
of free product and a 3.5 acre plume of dissolved-phase groundwater
contamination was delineated. A temporary product
recovery system was installed and operated prior to the installation of
a four-well groundwater pump-and-treat system. The
recovery wells operated simultaneously to maintain hydraulic control
over the leading edge of the contaminant plume. Free-product was
separated and contained; the remaining contaminated groundwater was
pumped through a parallel series of activated carbon vessels and then
subsequently discharged to a nearby stream following the requirements of
a NPDES permit. The active groundwater treatment
system was shutdown in October 2005. Groundwater
compliance point well monitoring began in December 2005, and concluded
in September 2007. The attainment monitoring data
was combined with contaminant fate-and-transport analyses to
demonstrate that the dissolved contaminant plume would attenuate within
the confines of the property to concentrations below the Statewide
Health Standards. All supporting data was
submitted to the PA DEP in a Final Report. The PA DEP accepted the Act 2 Final Report and granted
liability protection in December 2009.
Commercial Greenhouses facility, Landisville, PA Closure (November
2008)
In March 2001, HES responded to a #2 heating oil release
from a leaking underground product distribution line. The
release was estimated to be approximately 300 gallons and impacted
surface and subsurface soils, surface water and groundwater. Efforts by HES, the PA Fish Commission and the PA DEP
contained the majority of the fuel that impacted the surface; however,
there was a small impact to a nearby stream and pond. Soil
impacted in the immediate vicinity of the release was excavated and
disposed.
At the request of the PA DEP a site characterization
investigation was performed. Fifty-four soil
borings and 17 monitoring wells were installed to delineate the extents
of soil and groundwater contamination. A three
well product and groundwater recovery system was installed and operated
to address the free phase product and dissolved groundwater impacts. Over 99% of the free product was recovered by the
remediation system, and the dissolved contaminant plume was reduced to
the extent that it longer has the potential to impact on-site water
supply wells or migrate off the property. The active groundwater
treatment system was shutdown in June 2005. A
soil demonstration of attainment sampling event was performed in July
2005 and indicated that all impacted soil had been remediated to
acceptable concentrations. Groundwater compliance well monitoring began in
September 2005, and concluded in June 2007. The
attainment monitoring data was combined with contaminant
fate-and-transport analyses to demonstrate that the dissolved
contaminant plume would attenuate within the confines of the property to
concentrations below the Statewide Health Standards. All
supporting data was submitted to the PA DEP in a Final Report. The PA DEP accepted the Act 2 Final Report and granted
liability protection in November 2008.
Petroleum Bulk
Plant, Lancaster, PA (Closure April 2007)
In
September and October 1998, five underground storage tanks were removed
from two separate tank fields at the bulk plant. Three
of the removed USTs formerly stored gasoline and each contained
numerous corrosion holes. A site characterization
investigation was performed to delineate the extent of soil and
groundwater contamination at the facility. The
soil investigation included the extension of 33 soil borings and
revealed that over 1,700 cubic yards of soil between the depths of 8 and
39 feet below grade had been impacted at concentrations above the PA
DEP Statewide Health Standards. The groundwater
investigation included the installation and sampling of 9 groundwater
monitoring wells. Groundwater impacts were
limited to the area located near the one of the former UST
fields, and monitoring data suggested the dissolved contaminant plume
would attenuate before reaching the downgradient property boundary. The remediation strategy proposed for the impacted
groundwater was monitored natural attenuation and four additional
compliance-point monitoring wells were subsequently installed along the
site’s downgradient property boundaries.
The impacted soil at
the site consisted of a mixture of silts, clays and clay loam. Due to the depth of the impacted soil, excavation was not feasible, and the fine-grained
texture of the soil limited the number of in-situ remediation options. A high-vacuum soil vapor extraction system utilizing
an oil-sealed liquid-ring vacuum pump was installed in April 2004 to
extract gasoline vapors from a network of 8 extraction wells located in
the two separate source areas. The extracted soil
gas was passed through two 1,800 lb activated carbon canisters and
discharged to the atmosphere. A soil
investigation performed after 13 months of operation revealed that
contaminant concentrations in one source area were reduced to levels
below the Statewide Health Standards and that contaminant concentrations
in the second source area had been reduced to levels slightly above the
Statewide Health Standards. The attainment samples from both impacted areas passed the
statistical test and attainment of the SHS has been
demonstrated for the impacted soil. Each of the
facility's 8 compliance-point monitoring wells passed the statistical
test and attainment of the SHS was documented. The PA DEP accepted the Act 2 Final Report and granted
liability protection in April 2007. Former Auto Dealership and Garage, Bensalem, PA (Closure June 2002)
Three underground storage tank systems were removed from three separate areas on the property. Free product and contaminated soil were encountered in each tank area. Interim remedial actions were performed to recover the free product. Twenty-six soil borings were extended to delineate the extent of soil contamination and seven groundwater monitor wells were installed to delineate the extent of groundwater contamination. A combination soil vapor extraction/in-situ bioremediation system was installed and operated in one of the tank areas. In the other two UST areas, contaminated soil was excavated and contaminated groundwater was removed and treated on-site.
Approximately 100 tons of gasoline-contaminated of tank bedding material was treated above grade with an on-site vapor extraction system. Within 58 days the pile was remediated to non-detect concentrations.
Twenty-three hydraulic lift systems and a floor drain collection system were removed from the facility. Thirty-four additional soil borings, 10 of which were converted to small-diameter monitoring wells, were installed to delineate soil and groundwater contamination in these areas. Contaminated soil was excavated and disposed and contaminated groundwater was remediated by a pump-and-treat system.
During the cleanup process, a potential buyer expressed interest in the property; however, the buyer was concerned about potential environmental liability associated with the past petroleum releases. HES worked closely with the owner, the buyer, and the PA DEP to create and execute a buyer/seller agreement that would allow the sale of the property to proceed. Under the agreement, the original owner of the property retained responsibility for the environmental cleanup. The new owner purchased and developed the property.
HES performed an aquifer usage evaluation in the area surrounding the property and subsequently received a “non-use aquifer” designation from the PA DEP. This risk-based designation allows the property owner to use less stringent cleanup standards in areas where groundwater is not used as a source of potable water. In addition, HES performed contaminant fate-and-transport modeling to demonstrate that a contaminant plume originating from a gasoline tank area was stable and would not migrate beyond the downgradient property boundary. Eventually, soil and groundwater contamination in 18 source areas was remediated to levels below the PA DEP cleanup standards. Pennsylvania regulatory requirements call for the installation and monitoring of compliance wells on the downgradient property boundaries to demonstrate attainment of the applicable cleanup standards. HES performed five successful quarters of monitoring and then pursued final closure. The PA DEP accepted the Act 2 Final Report and granted liability protection in June 2002. The site has since been redeveloped and houses a Giant Super Market.