Status Report for Stono Phosphate Works Site – Completion of the Non-Time-Critical Removal Action
The Stono Phosphate Works Site (the “Site”) is a 15-acre, Non-NPL site located on Austin Avenue in North Charleston, South Carolina. The Site is located between Interstate 26 to the east and the Ashley River to the west. The Site is bounded to the north by the Rhodia Corporation facility, and to the south by the Atlantic Phosphate Works Site (including the Hagood Power Station owned and operated by SCE&G). The predominant structures that are located on the Stono Phosphate Works Site today are related to the Dolphin Cove Marina.
Phosphate fertilizer manufacturing occurred at the Site from 1900 to the late 1950s. Environmental impacts associated with the former phosphate manufacturing include lead and arsenic contamination, as well as low pH conditions, in soil, sediment, and groundwater. By way of a corporate merger in 1999, the Exxon Mobil Corporation is successor in interest to former VCC phosphate-based fertilizer manufacturing activities at the Site.
The Non-Time-Critical Removal Action (NTCRA) was initiated at the Site in January 2011, and involved the excavation, treatment, and off-site disposal of an estimated 30,000 to 40,000 cubic yards of contaminated soil and sediment. The wetlands impacted by the NTCRA were restored once the sediment excavation work was complete. A chemical amendment was mixed with the backfill placed below the water table in the soil excavation areas to help reduce the levels of lead and arsenic in groundwater. EPA met with representatives from SCDHEC, and ExxonMobil’s consultants ARCADIS on June 16, 2011, to conduct the Final Inspection for the NTCRA. Demobilization was completed on July 8, 2011.
As part of the Post-Removal Site Controls, groundwater monitoring will continue at the Site in order to determine the effectiveness of the NTCRA. Lead and arsenic levels in groundwater are expected to decline within 5 to 10 years. Future land use restrictions will be placed on the property deed to prohibit anyone from using the impacted groundwater for drinking water purposes.