Projects Investigating and Remediating
Petroleum Contaminated Soils (Includes Indoor Air Quality Sampling)
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Site: Convenience Store, Skowhegan, Maine.
EnviroInvestigations (ERI) conducted a Maine DEP Chapter 691 UST site
assessment and discovered a release of petroleum product (gasoline) at the site. ERI
installed over 150 feet of soil vapor extraction (SVE) piping while the site was still
under construction for the UST replacement. ERI coordinated and supervised soil removal
operations. We performed a hydrogeological investigation that included the direct
advancement of 15 soil borings, installation of five micro-wells and groundwater and soils
sampling for gasoline, MTBE, BTEX and diesel fuel. Referencing water utility and town
records with a site walkover, ERI performed a survey of private water supply wells within
1,000 feet of the site. ERI interacted directly with the town officials and negotiated a
two-year land use agreement for the placement of the above ground portion of the soil
vapor extraction system (VES).
We designed and installed a soil vapor extraction system at the site
because of high levels of gasoline concentrations in site soils and due to the potential
of petroleum vapors migrating into an adjacent dwelling. The work included soil vapor
modeling using Hyperventilate software, system design and construction, system start-up
and monthly operation and maintenance monitoring. A 7.5 horsepower regenerative blower is
extracting about 275 cfm of gasoline vapors from two horizontal vapor extraction wells.
Readings of gasoline vapors from the exhaust have averaged over 175 ppm since the system
was put online in late fall 1998.
Site: Condominium, Yarmouth, Maine.
Two hundred (200) gallons of kerosene were released inside the living
room of a condominium. The spilled kerosene flowed from the first floor, down the interior
and exterior basement walls and ended up on the water table under the basement floor
through cracks and seams in the basement floor. We conducted a hydrogeological
investigation of the release and documented soil type for remedial options, delineated the
extents of contamination and installed three micro-wells to determine water table
elevation and groundwater flow direction. In addition, ERI advanced four Geoprobe
soil borings near the spill site, performed vapor screening of soil headspace, and
conducted an elevation survey of the micro-wells and gauged the water levels. We
coordinated a soil removal where approximately 40 cubic yards of contaminated soil were
removed from the site. Site restoration work included removal and replacement of shrubs,
ground covering ornamental plants and sod by a licensed insured professional landscaper.
Exterior site restoration work ended with the installation of a new asphalt walk/driveway
to the satisfaction of the condominium owners and the owner's association board of
ERI designed, installed and provided operations and maintenance
(O&M) for a kerosene recovery, groundwater depression and vapor extraction system for
the site. The groundwater depression system removed water from below the basement floor
and passed it through two carbon filters before re-introducing it back under the basement
floor upgradient of the spill area. The vapor control system involved venting underneath
the basement floor using a regenerative blower and exhausting it outside above the
building roofline. Bioremediation (bacteria enzymes break down the petroleum hydrocarbons
into carbon dioxide, water and fatty acids) was successfully used to remediate the
kerosene contaminated concrete walls and floors.
Indoor air quality tests (analysis by NIOSH 1550 and TO-14 (sample
collections by SUMMA Canister)) for kerosene vapors was performed throughout the
remediation process to document clean-up progress and determine when final clean-up goals
were achieved. Air sampling results have been compared to the action levels in MDEPs
"Trial Guideline for Protecting Residents from Inhalation Exposure to Petroleum
Vapors". The most recent indoor air quality tests indicated that site clean-up goals
have been met. The site is currently undergoing final restoration for site closure.
Site: Apartment Building, Biddeford, Maine.
The MDEP reported that approximately 200 gallons of #2 heating oil was
spilled at the site in August 1998. The spill appeared to be caused from a corrosion hole
that formed in the bottom of a 275-gallon aboveground storage tank (AST) located in the
basement of the building. Additionally, MDEP decided to continue monitoring for
recoverable free product and to conduct indoor air quality (IAQ) sampling during the
1998/1999 heating season. IAQ samples were collected over a 24-hour time period using
SUMMA canisters. ERI collected IAQ samples in the basement, 1st floor front
apartment and the 1st floor rear apartment living areas of the building.
Samples were analyzed for benzene, toluene, ethylbenzene, total xylenes, n-hexane,
n-nonane and naphthalene by gas chromatography/mass spectrometry (GC/MS) according to EPA
Method TO-14 (Compendium of Methods for the Determination of Toxic Organic Compounds in
Ambient Air - Volatile Organic Compounds).
All sampling results were compared to the chronic (365
days or more of exposure) Action Levels published in the "MDEP Guideline for
Protecting Residents From Inhalation Exposure to Petroleum Vapors" to determine if
further corrective action was needed or if site closure could occur. It was concluded that
indoor air quality in the basement and front and rear apartments were within acceptable
MDEP Health Guidelines for inhalation. All air sample concentration results were below chronic
Action Levels and indicated, according to the MDEP Guideline, that all sampled areas would
be suitable for long-term occupancy (i.e., 70 years) without any significant health risks.
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