Metropolitan Transportation Authority Long Island Railroad Jamaica Station
Posted on June 11, 2015
Client: MTA Long Island Railroad
Location: Jamaica Station, Jamaica, New York
Project Type: Remedial Investigation
Project Cost: $161,500
D&B Project Responsibilities
LIRR retained D&B to conduct a Remedial Investigation (RI) of a petroleum spill that occurred at the LIRR Jamaica Station facility in Jamaica, New York and is classified as “open” by the New York State Department of Environmental Conservation (NYSDEC). The spill resulted from a release of No. 2 fuel oil from two 20,000-gallon underground storage tanks (USTs). The characterization of the spill is complicated by the presence of numerous subsurface utilities in the area, including subway tunnels and underground utilities, along with the presence of highly variable urban fill. Furthermore, above grade structures supporting immediately adjacent elevated tracks severely limit access to drilling/sampling equipment. Additionally, extensive pumping associated with public water use and subway tunnel dewatering has resulted in historical water table fluctuations of more than 20 feet within the spill area, further complicating subsurface conditions.
The objective of the RI was to characterize the extent of contamination related to the spill, as well as site hydrogeology, in order to obtain sufficient information to develop appropriate remedial actions and obtain closure of the spill. To achieve this objective, despite the complications described above, D&B thoroughly reviewed historical data and focused the RI on closing any data gaps associated with the source area, and avoiding any duplication of past work. In addition, D&B planned to complete all borings to a depth sufficient to characterize the entire zone of historical water table fluctuations. 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 the closed USTs;
- Five soil borings to a depth of 55 feet below grade and the collection of subsurface soil samples utilizing the Geoprobe direct-push method;
- Two groundwater probes and the collection of groundwater samples utilizing the Geoprobe direct-push method; and
- The collection of groundwater samples from all existing monitoring wells utilizing low-flow sampling procedures.
During the RI, which was completed in April 2012, D&B was successful in delineating the extent of residual petroleum contamination associated with the USTs, which included heavily stained and NAPL saturated soil. However, VOC and SVOC concentrations in soil and groundwater were found to be relatively low.
Based on the evaluation of historical and recently acquired data, D&B developed a conceptual model for the site, determining that the heavily weathered state of the residual petroleum resulted in the low contaminant concentrations. This evaluation also confirmed our initial hypothesis that a large “smear” zone would be present due to the significant historical water table fluctuations and the likely “old” age of the spill. By identifying this complicating factor during the initial scoping process, D&B had been able to successfully achieve the objective of delineating the extent of contamination, providing a long-term savings in cost and time for LIRR.
Following the completion of the RI, NYSDEC requested that additional soil borings and monitoring wells be installed downgradient of the USTs in the elevated tracks, despite the severe limits to drilling equipment in this area. D&B investigated the use of drilling equipment designed to operate on railroad tracks (i.e., hi-rail drill rig) and located a capable operator. Working closely with LIRR, D&B is in the process of planning this challenging drilling work.
The current scope of work for the hi-rail drilling includes the completion of three soil borings to a depth of 75 feet below grade utilizing the mud rotary drilling method. Subsurface soil samples will be collected for characterization purposes, followed by the installation of permanent monitoring wells. This work will be completed during off-hours and weekends to avoid disruption to LIRR’s commuter schedule. In order to complete the work safely, on time and within budget, close cooperation will be required between D&B, the drilling contractor and multiple divisions of the LIRR. Following the installation and sampling of the newly installed wells, D&B will assist LIRR with selecting a remedial action for the open spill.
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