Abstract
The state of New Jersey is not known for extensive karst landscapes, but there are over 100 caves listed in a survey of those features. Numerous sinkholes have also been identified, though no comprehensive database yet exists. Occasional news stories have reported damaging collapses, many of which seem infrastructure related, in several counties. This paper reports on the conditions at a proposed major construction site in a glaciated limestone terrane, Warren County. The area is underlain by the Allentown Dolomite and the Beekmantown Group carbonates (Cambrian/Ordovician age), and covered with a variable layer of glaciofluvial sediments. The area is of extra concern for karst-related issues because: 1) It is close to the terminal margin of multiple glacial advances, and therefore was likely subjected to high surface and groundwater flux of waters undersaturated with respect to CaCO3. 2) It is close to the incised Delaware River, which is ~50 m lower in elevation, implying valley wall stresses and increased local hydraulic gradients that could increase the development of karst features. 3) An abandoned, possibly pre-glacial, streamway crosses the site. 4) A thrust fault bounds the area on the east, across which lie low solubility crystalline rocks forming an allogenic highland. Anticipated site changes included large impermeable areas, stormwater management, groundwater extraction, and wastewater disposal. Concerns included infrastructure stability, water quality and water availability. Although surface expression of karst features was minimal, preliminary excavations and limited well data indicated an irregular rockhead and deep high permeability zones. In the end, this project was withdrawn, though not due to karst conditions. A wholistic approach combining regional geologic history, hydrogeology, site observations, subsurface data, and planned development impacts provides benefit when evaluating karst risk.
DOI
https://doi.org/10.5038/9781967518012.1028
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Karst at a Potential Construction Site Adjacent to the Delaware River Near the Glacial Terminus, New Jersey, USA
The state of New Jersey is not known for extensive karst landscapes, but there are over 100 caves listed in a survey of those features. Numerous sinkholes have also been identified, though no comprehensive database yet exists. Occasional news stories have reported damaging collapses, many of which seem infrastructure related, in several counties. This paper reports on the conditions at a proposed major construction site in a glaciated limestone terrane, Warren County. The area is underlain by the Allentown Dolomite and the Beekmantown Group carbonates (Cambrian/Ordovician age), and covered with a variable layer of glaciofluvial sediments. The area is of extra concern for karst-related issues because: 1) It is close to the terminal margin of multiple glacial advances, and therefore was likely subjected to high surface and groundwater flux of waters undersaturated with respect to CaCO3. 2) It is close to the incised Delaware River, which is ~50 m lower in elevation, implying valley wall stresses and increased local hydraulic gradients that could increase the development of karst features. 3) An abandoned, possibly pre-glacial, streamway crosses the site. 4) A thrust fault bounds the area on the east, across which lie low solubility crystalline rocks forming an allogenic highland. Anticipated site changes included large impermeable areas, stormwater management, groundwater extraction, and wastewater disposal. Concerns included infrastructure stability, water quality and water availability. Although surface expression of karst features was minimal, preliminary excavations and limited well data indicated an irregular rockhead and deep high permeability zones. In the end, this project was withdrawn, though not due to karst conditions. A wholistic approach combining regional geologic history, hydrogeology, site observations, subsurface data, and planned development impacts provides benefit when evaluating karst risk.