Project: Contaminated Sediment Capping
Location: Poughkeepsie, NY (Hudson River Valley)
Duration: 1 Month


Northstar Marine’s dive services were subcontracted for an environmental test study being conducted at a closed power plant in Poughkeepsie, NY, located on the Hudson River. When in operation the plant produced a by-product sediment consisting of NAPL (manufactured gas plant coal tar) and aromatic hydrocarbons (PAH’s). This substance had accumulated in the surrounding riverbed and was being released into the water in the form of a slick. As a result Agate Construction was contracted to lay stone filled Geo Grid Mats designed to absorb the coal tar product in a 100’x100’ test area.

Northstar provided all dive services for the project.  After rough positioning was done with sonar and marker buoys on the river bottom, the Northstar divers entered the water and directed any necessary repositioning using two-way communication. The final positioning was determined once the divers checked and measured to determine the Geo Grid Mat was within given tolerances. The divers used surface supplied air and were working in approximately 60’ of water, in water temperatures between 40 and 55 degrees, with a visibility of approximately 6 inches to 2 feet in currents averaging 1 ½ to 5 knots. If the Geo Mat system is found to be effective, Northstar will be contracted to assist in this innovative technology for the capping of the impacted sediment in several acres of the Hudson River.