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 directors.

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 MDEP’s "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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