Nyack MGP Site (Isotec Case Study 29)
Site Location: Nyack, NY
Contamination: Bedrock contaminated with non-aqueous phase liquid (NAPL) and MGP-related compounds. Primary contaminants of concern (COCs) include volatile organic compounds (VOCs), Poly-nuclear aromatic hydrocarbons (PAH's) and total petroleum hydrocarbons (TPH). Levels of COCs reached 6 mg/l for VOCs and 1,200 mg/l for PAHs in the dissolved phase and 8,500 mg/l for VOCs, 36,000 for PAHs and 900,000 mg/l for TPH in NAPL.
Geology: Fractured bedrock
Area Treated: ~36,000 cubic yards consisting of 20 vertical feet of an impacted bedrock zone.
Effectiveness: Successfully treated a large portion of the free phase NAPL present in the bedrock. The entire project was completed ahead of the schedule and under the budget (the total cost of the treatment program was ~ $300,000 . The project was given an 'Award of Merit' by the New York Construction Journal in 2007.
The subject site is a former MGP site located in Nyack, New York. Past business activities at the site resulted in soil, groundwater and soil gas contamination with both light nonaqueous phase liquid (LNAPL) and dense non‐aqueous phase liquid (DNAPL) and MGP‐related compounds. The New York State Department of Environmental Conservation (NYSDEC) in consultation with the New York State Department of Health (NYSDOH) had selected a four‐phased remedy for the entire site. ISOTEC’s in‐situ chemical oxidation (ISCO) technology was chosen as the second phase of the remedy to address the impacted bedrock, the source of the site contamination. The applicable remedial action objectives for the bedrock remedy as described in the Record of Decision (ROD) for the site are to eliminate or reduce to the extent practicable: 1) the presence of NAPL and MGP‐related contaminants as the sources of soil, groundwater and soil gas contamination; and 2) the migration of NAPL and MGP‐related contaminants that would result in soil, groundwater, or soil gas contamination.
The size of the impacted bedrock volume was estimated to be 36,000 cubic yards with an assumed impacted bedrock thickness of 20 feet and the total pore volume of the impacted bedrock was estimated to be 145,000 gallons. Based on contamination investigation performed at the site, approximately 24% of the pores and fractures within the impacted zone were estimated to be NAPL or “sheen” impacted, though not necessarily saturated. Target contaminants of concern (COCc) are the NAPL/MGP‐related constituents including volatile organic compounds (VOCs), polynuclear aromatic hydrocarbons (PAHs) and total petroleum hydrocarbons (TPH). Levels of the COCs reached 6 ppm for VOCs and 1,200 ppm for PAHs in dissolved phase and exceeded 8,500 ppm for VOCs, 36,000 ppm for PAHs and 900,000 ppm for TPH in NAPL. Prior to the ISCO treatment program, a total of 36 liters of LNAPL and DNAPL had been recovered from some of the bedrock wells.