Terminal Avenue Brownfield
Landmark was contracted by the buyer to perform a Phase I Environmental Site Assessment (ESA) and a wetland delineation on the undeveloped 2-acre property in Wilmington, Delaware. Based on the findings, a Phase II ESA was conducted. The buyer entered the property in the DNREC State Brownfields program based on the results of the Phases I and II ESA reports with the intent of developing the property for future commercial use while getting liability protection and financial assistance through the Brownfields Program.
Landmark collected soil samples, sediment samples, groundwater samples, and surface water samples, which were analyzed by a DNREC-sanctioned laboratory and found to contain high concentrations of heavy metals and semi-volatile organic compounds. The analytical results, cleanup recommendations, and risk assessment data were issued in a Brownfield Investigation (BFI) report. The data in the BFI report along with the wetland functional assessment and the clean-up actions described in the Final Plan of Remedial Action issued by DNREC were used to design an acceptable Remedial Action Work Plan.
Due to the elevated risk to human health from the on-site contaminants, a 12-inch thick (minimum) earthen cap was designed to be placed over the entire subject property to permanently encapsulate and prevent future exposure to the underlying contaminated soils and sediments. Placement of the proposed cap over the entire site necessitated the construction of a structural retaining wall, piping an existing drainage ditch, and filling an existing non-tidal emergent wetland with clean imported fill material, which required a Nationwide Permit (NWP 38) from the USACE and a Subaqueous Lands permit from DNREC.
The USACE issued a NWP 38 for the permanent filling of 1.2 acres of wetlands and Waters of the U.S. (WOTUS) and mandated compensatory mitigation of 0.6 acres as a condition of the permit. Due to size constraints and underlying contaminated soils, a suitable off-site location in the same watershed was designed by Landmark and approved by the USACE, which has been constructed and is currently being monitored.