Ventron and Velsicol were jointly liable for the environmental damage. The creek has been measured as having the highest concentration of methyl mercury of any fresh-water sediment in the world. Between 1 and 2 g of mercury per kg of sediment were detected in samples. A total of discharge of 268 tons of mercury-contaminated toxic waste were discharged into the creek between 1943 and 1974. Wolf had demolished the former Ventron plant in 1974, but the residual pollution remained in the creek, rendering the site still unsustainable. EPA Superfund designations The federal "Superfund" law was enacted by Congress in 1980 to provide for cleanup of hazardous waste sites, and was based on New Jersey’s 1977 spill cleanup law. EPA applied the new cleanup law in 1983 and 1984 as it designated the Ventron/Velsicol site and two nearby sites—the Scientific Chemical site in Carlstadt, and the Universal Oil Products site in East Rutherford—as Superfund sites. EPA and NJDEP began detailed assessment and initial cleanup activities on these sites in the 1980s. Contaminated soil was removed and replaced at several properties in 1990, as an interim measure. but completion is projected to continue during the first quarter 21st century. In addition to mercury, all three sites are laden with PCBs. Only the Scientific Chemical site is listed as "under control" as of 2018. In October 2018 EPA announced a 5.5-year plan to remove and/or cap the toxic waste in the creek and watershed resulting from the Ventron/Velsicol site discharges. Wildlife Through the early 1900s, the predominant plants in the watershed were freshwater species such as cattails and Atlantic white cedar. The plant composition began to change after construction of the Oradell Dam on the Hackensack River in 1921. The dam was built at the head of tide, which increased the salinity of Berry's Creek, and since then the marsh vegetation in has been composed predominately of Phragmites (Phragmites australis). Berry's Creek harbors the last remaining northern harrier nest site in the Meadowlands. It is heavily used by wintering raptors. "The marshes of the Meadowlands provide many important wetland functions. More than 265 species of birds use the area, and the Meadowlands is recognized as a major link along the Atlantic Flyway for migratory species (especially shorebirds) and an important overwintering area for a variety of waterfowl... Waterway-associated birds occurring in the region include a variety of shorebirds, wading birds, waterfowl, and gulls."