Quantifying Subsurface Tar Volumes at Three Former Manufactured Gas Plants

Abstract

Manufactured gas plants (MGPs) were a staple of the Industrial Revolution, operating in the US primarily on the East Coast, starting in the early 19th before phase-out in the mid-twentieth century. Their legacy includes the release of copious quantities of subsurface tar, and when located adjacent to waterways, tar in sediment due to direct discharge and leaking bulkheads. Computing the depth and extent of tar impacts is a three-dimensional problem required to facilitate appropriate remediation efforts. At three former MGPs, 306, 223, and 254 boreholes with 1452, 544, and 276 intervals were coded and %saturation attributed to saturated (S_n = 70%) and residual (S_Nr = 20%) tar. These data were incorporated into the 3-D krieging software EnviroInsite to estimate the spatial extent of tar and oil impacts and their affiliated volumes. At the former Citizens, Fulton, and Metropolitan MGPs, the model estimated a most probable volume (MPV) of 7.21, 4.36, and 0.8 million gallons of tar. As a sensitivity analysis, S_n was decreased to 60%, reducing the MPV to 6.3, 3.4, and 0.6 million gallons, respectively, Regardless, it is irrefutable that a large amount of tar remains in the subsurface ∼70 years after the facilities ceased operating.

Keywords:

• MGP
• percent
• saturated
• residual
• sensitivity
• east
• coast

Acknowledgements

The contributions of Med Bennett and David Frank are recognized and much appreciated over the course of this project.

Disclosure Statement

No potential conflict of interest was reported by the author.

Data Availability Statement

The data used in the model are available in the Supplemental Information.

Additional information

Funding

This work was completed as part of a project determining the subsurface LNAPL volume at the 3 MGPs cited. While Geomega and myself had a commercial relationship over the duration of the project with our client, no funding was requested to develop this paper and they had no involvement in the preparation of this manuscript.