Metropolitan Transportation Authority Long Island Railroad Long Island City Freight Yard
Posted on June 12, 2015
Client: Metropolitan Transportation Authority Long Island Railroad
Project Type: Remedial Investigation and Remedial Design
Project Cost: $116,500
D&B Project Responsibilities
The LIRR retained D&B to conduct a Remedial Investigation (RI) of an “open” petroleum spill that occurred at the LIRR Long Island City Freight Yard in Long Island City, New York. The site is a former gasoline service station, which operated under a lease agreement with the LIRR from the early 1940’s to 1984. The spill is associated with nine former 550-gallon USTs that leaked an unknown quantity of gasoline, resulting in documented soil and groundwater contamination. According to information provided by the LIRR, the USTs and 100 tons of contaminated soil were removed from the site in 1995.
It was clear to D&B that a number of factors would complicate the characterization of the spill, such as the highly industrialized nature of the neighborhood, with a gas station present directly across the street. In addition, numerous underground utilities are present both on-site and off-site which could be influencing groundwater flow and contaminant migration, including the Jackson Avenue below grade subway tunnel. Further complications include the presence of highly variable urban fill, recognized by the New York State Department of Environmental Conservation (NYSDEC) as potentially containing contaminants that could be mistakenly attributed to the open spill.
To address these complications, D&B conducted a detailed review of existing data and reports, and developed a RI work plan that not only focused on delineation of the residual contamination related to the spill but also on determining groundwater flow direction and the potential effect that utilities may be having on groundwater flow and contaminant migration. The goal was to determine what contamination was related solely to the spill, and be able to separately identify contamination that may be related to urban fill or off-site sources such as the gas station. As part of the RI, D&B completed the following:
- A geophysical survey utilizing terrain conductivity and electromagnetic methods, along with ground penetrating radar (GPR) to locate underground utilities and the limits of the previous UST excavation areas;
- The completion of 10 soil probes and the collection of soil samples for chemical analysis utilizing the Geoprobe direct push method;
- The installation and development of two groundwater monitoring wells utilizing the hollow stem auger drilling method; and
- The collection of groundwater samples from all newly installed and existing monitoring wells utilizing low-flow sampling procedures.
The RI was completed in August through December 2011. Based on the results of the RI, D&B was able to determine the extent of residual contamination from the spill, finding minimal evidence of volatile organic compounds (VOCs) in soil around the former excavation areas. The contaminants that were identified were confined vertically in a zone from the water table to the top of a confining clay-rich unit starting at approximately 11 to 15 feet in depth. Several semivolatile organic compounds (SVOCs) that were consistent with historic fill and not related to the spill were also detected in soil in the same area. However, elevated concentrations of VOCs related to the open spill, including BTEX and several benzene-containing compounds, were identified within site groundwater, consistent with historical data.
In the RI Report, D&B argued that soil impacts from the spill had been largely remediated through the removal of the USTs and associated contaminated soil, and in accordance with NYSDEC’s CP-51 guidance and NYSDEC’s previous determinations regarding urban fill. We recommended investigating the feasibility of implementing groundwater remedial activities in a targeted area of the Site, as well as continuous routine groundwater sampling until closure of the “open” spill is achieved. Following submittal of the RI Report, D&B assisted LIRR with its negotiations with the NYSDEC regarding the remedial alternatives for the Site, and the NYSDEC ultimately approved D&B’s recommendation to proceed with in-situ chemical oxidation treatment and an enhanced monitoring schedule to address the remaining subsurface contamination.
In June 2013, D&B prepared a Conceptual Design for in-situ chemical oxidation treatment for the Freight Yard site, which was submitted to the NYSDEC for review. The plan calls for a two-part injection of a chemical oxidant (RegenOxTM), followed by Oxygen Release Compound (ORC Advanced) to break down the petroleum contaminants in the short term and encourage aerobic bioremediation over a longer time period. The chemicals will be introduced to the subsurface between the water table and confining clay unit using the Geoprobe direct-push technology at approximately 25 injection points covering the impacted area. Once NYSDEC gives final approval for this plan, D&B will assist LIRR in implementing the injections, with follow-up performance monitoring.
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