The Diamond Alkali Superfund Site (DASS) includes portions of the Passaic River beginning at the lower Passaic River Study Area (LPRSA), which runs 17.4 miles south from the Dundee Dam to the confluence with the Hackensack River, and the Newark Bay Study Area (NBSA), including Newark Bay, the Arthur Kill, the Kill Van Kull, and tidal portions of the Hackensack River. However, these areas incorporate only a portion of the New York Bight Watershed Estuary, which through tidal action, intricately connects the water bodies of the Passaic River to both the Upper and Lower New York Bays and the Hudson River.

Production of pesticides and other chemical products began at 80 Lister Avenue in the 1940s. In the 1950s and 1960s, the Diamond Alkali Company owned and operated the facility, manufacturing agricultural chemicals, including the herbicides used in the defoliant known as “Agent Orange.” An unwanted by-product of these manufacturing processes was the extremely toxic chemical 2,3,7,8-tetrachlorodibenzo-para-dioxin, (2,3,7,8-TCDD and hereinafter referred to as “TCDD”). TCDD is commonly and interchangeably referred to as “dioxin,” although dioxin(s) is actually a general name for a large group of chemical compounds, with similar chemical structures, that induce toxicity via a common mechanism of action, resulting in a common spectrum of biological responses.

In 1983, environmental sampling by the State of New Jersey and the U.S. Environmental Protection Agency (EPA) at and near 80 Lister Avenue, as well as in the river, revealed high levels of TCDD. The site was subsequently listed on the Superfund National Priorities List (NPL) in 1984. TCDD, pesticides and other hazardous substances were found in the soil and groundwater at 80-120 Lister Avenue. TCDD, polychlorinated biphenyls (PCBs), metals, polycyclic aromatic hydrocarbons (PAHs) and pesticides were also found in sediment of the lower Passaic River. Additional sampling revealed DASS-related hazardous substances throughout Newark Bay and its tributaries, the Hackensack River, the Arthur Kill River tidal strait and the Kill Van Kull tidal strait.

The DASS was listed on the National Priorities List on September 21, 1984. As defined by EPA, the DASS consists of “...the former Diamond Alkali facility at 80-120 Lister Avenue in Newark, New Jersey, the Lower Passaic River Study Area (LPRSA), the Newark Bay Study Area and the areal extent of contamination.” The LPRSA is “...the 17-mile, tidal portion of the Passaic River, from RM [River Mile] 0 to Dundee Dam (RM 17.4), and its watershed, including the Saddle River (RM 15.6), Third River (RM 11.3) and Second River (RM 8.1).” The EPA has divided the DASS into four “operable units” (OUs):

• OU1, the former site of the Lister Avenue Plant;

• OU2, the lower 8.3 miles of the Passaic River (the “Lower 8.3 Miles”);

• OU3, Newark Bay and portions of the Hackensack River, Arthur Kill, and Kill van Kull; and

• OU4, the 17-mile LPRSA.

Collectively, the four OUs incorporate only a portion of the New York Bight Watershed Estuary, which through tidal action intricately connects the water bodies of the DASS to both the Upper and Lower New York Bays and the Hudson River.

The LPRSA watershed includes the northeastern New Jersey counties of Bergen, Essex, Hudson, and Passaic. Most of the area is developed, with these counties having a combined population in 2018 of approximately 3 million people (U.S. Census Bureau 2018). Land use in the watershed is a mix of residential, commercial, and industrial. Intensive commercial and industrial uses occur near Newark Bay, which is in proximity to an extensive infrastructure of roadway, railway, and marine transportation services.

Environments adjacent and within the DASS include a mixture of urbanized and degraded natural environments. The salt marshes of the New Jersey Meadowlands border the Hackensack River for about seven miles from just north of Newark Bay up to the confluence with the Overpeck Creek. Further north, the Hackensack is surrounded by suburban developed land up to the Oradell Dam. The Arthur Kill and Kill Van Kull, important shipping channels in the New York/New Jersey Harbor, border Staten Island on the west and north, respectively, separating the island from mainland New Jersey. The channels are surrounded by a mixture of industrial and commercial facilities, urban parks, and residential neighborhoods. Newark Bay is an urban estuary about six miles long, fed by fresh water entering from the Passaic and Hackensack Rivers at the north end and by salt water entering from the Arthur Kill and Kill Van Kull tidal straits from the south.