The Pinewood Site (the Site) is a closed hazardous waste landfill that is held in trust for the people of South Carolina through SCDHEC. By permit, the Site must be operated and maintained under post closure care requirements until 2103. One of the primary maintenance activities is routine monitoring and removal of landfill leachate that accumulates on top of the liner system within each closed landfill cell.
What is Landfill Leachate?
Landfill leachate is liquid that has passed through a waste mass. Leachate generated at the Pinewood Site meets the definition of listed hazardous waste code F039, multi-source leachate.
Collection, Treatment & Removal of Landfill Leachate
At the Pinewood Site, leachate is collected through a series of collection pipes and sumps in the landfill. Once leachate is pumped from each landfill cell sump, it is collected in storage tanks located on-site in the Central Tank Farm (CTF), where it is either sent off-site for disposal at permitted Treatment Storage and Disposal Facilities or treated on-site in the Leachate Treatment System (LTS).
The closed landfill is divided into three sections. Leachate is collected in sumps within the three sections of the landfill and pumped into on-site storage tanks in the CTF where it is accumulated for either shipment by tanker truck to an off-site disposal facility or treatment on-site within the LTS. Under normal circumstances, the LTS can treat the volumes of leachate generated from the three landfill sections. Once leachate is transferred to the LTS, pH adjustment and precipitation occurs. The suspended solids, including metal hydroxides, are removed from the leachate by a filter press and cartridge filter and subsequently dried in a sludge dryer, generating filter cake. Once suspended solids are removed from the leachate, the remaining liquid is evaporated in an evaporator reducing it to a concentrated liquid slurry. The liquid slurry is either sent off-site for disposal or further dried into a solid for eventual disposal offsite.
The leachate collection system consists of pumps, pipes, and tanks. The system requires regular maintenance and replacement parts to ensure its continuous operability. Additionally, the permit issued to the Pinewood Site from SCDHEC requires regular inspections at the Site, landscaping, and other periodic reporting.
Detection Monitoring Program
The Pinewood Site contracts with professionals to regularly sample several hundred groundwater wells that ring the landfill sections. The groundwater samples are analyzed by certified laboratories and the results are reported to SCDHEC. The strategic placement of the wells and the regular testing of the wells insures detection of any contaminants were they to escape containment in the close landfill cells.
Operational & Capital Improvements
Since the Pinewood Site will be monitored and maintained for the foreseeable future, the Pinewood Trustee continues to investigate ways to save money by making operational and capital improvements. The Trustee has worked with engineers to analyze leachate treatment alternatives in order to find the least expensive means of treating the landfill leachate. The Trustee is also working with landfill designers to improve part of the Section III landfill cover to reduce the quantity of leachate recovered from the primary and secondary liner of that section. Reduction of leachate will constitute meaningful savings to the Trust. Finally, the Trustee is preparing a Request for Proposals that will be distributed to qualified contractors seeking proposals to assist the Trustee with a design to enhance the cover of the oldest section of the landfill, Section I. Rainfall infiltration into Section I increases leachate recoveries from the Section I sumps, and therefore, operating costs. An enhancement to the cover could result in significant savings to the Trust over time.