The Raritan Bay Slag site is located in Morgan (Sayreville Borough) and Laurence Harbor (Old Bridge Township), New Jersey. From the late 1960s to early 1970s, Sea Land Development Corporation constructed the Laurence Harbor seawall along Raritan Bay and enhanced the Western Jetty, a federal navigation jetty of the Cheesequake Creek Inlet, using lead slag from industrial blast furnaces in Perth Amboy operated by the National Lead Company (now NL Industries).

In 2007, the New Jersey Department of Environmental Protection (NJDEP) identified elevated concentrations of antimony, arsenic, copper, and lead along the Laurence Harbor seawall adjacent to Old Bridge Waterfront Park. While NJDEP investigated the seawall area, the Western Jetty on the Morgan side of the Cheesequake Creek Inlet was identified as another area of concern. In March 2009, slag, refractory brick, and shredded automotive battery casings were discovered on a 47-acre parcel near Margaret’s Creek, a small tributary of Raritan Bay. Subsequent soil sampling found similar waste materials buried along the seawall and adjacent beach. The U.S. Environmental Protection Agency (EPA) added the site to the Superfund Program's National Priorities List (NPL) in November 2009. The impacted area extends approximately 1.3 miles along the waterfront from the just beyond the Western Jetty southeast to Margaret’s Creek. A 2,500 foot section of beach along the waterfront has been fenced off to restrict public access. The site is divided into three sectors based on the type of environment and proximity to source areas: the Seawall Sector, the Jetty Sector, and the Margaret’s Creek Sector.

The primary sources of contamination at the site are slag and battery casings. The seawall is built out of up to 80% lead slag, and the Western Jetty and adjacent shoreline is comprised of 80 to 90% slag. Waves in Raritan Bay flow predominantly from the east and northeast, and as a result, contaminants from the Seawall and Margaret's Creek Sectors migrated westward. Currents near the Jetty Sector are complex due to strong tidal currents within Cheesequake Creek. Sediment is deposited on the western side of the jetty and transported into the bay by the currents. To prevent recontamination, EPA first completed a cleanup of the Margaret's Creek Sector and is now developing the design plans to complete remedial actions.