Walden has prepared a Final Certification Report to document the lagoon closure activities performed at a mid-Atlantic paper mill. From 1937 to 1992, the paper mill discharged wastewater with a high total dissolved solids content into an unlined surfacelagoon_1 impoundment covering approximately 250 acres. Under an Order from USEPA and the State, the mill was required to close this lagoon in accordance with applicable residual waste management regulations. A wastewater treatment plant was constructed on-site in 1992, at which time wastewater discharge to the lagoon ceased permanently. The lagoon sludge was determined
to be non-hazardous, low permeability residual solid lagoon_2waste comprised mainly of inert calcium carbonate and paper fibers. Investigations confirmed that use of the lagoon had not adversely impacted groundwater or surface water quality.



The Residual Solid Waste Closure Plan for the lagoon was prepared by Walden’s senior

lagoon_3hydrogeologist, with the goal of restoring the area for beneficial use. Engineering and hydrogeologic studies concluded that the lagoon could be drained and the residual solids consolidated in a chemically and geotechnically stable landfill. Closure engineering studies indicated that a synthetic soil cap growing medium could be produced using readily available dewatered sludge from the mill’s wastewater treatment plant, wood waste and fly ash from the coal boilers. Importing low permeability cover material from an off-site source to control infiltration was not necessary because the lagoon sludge did not generate significant volumes of leachate. The lagoon closure activities include the following:

  • lagoon_4Draining the lagoon
  • Consolidating lagoon sludge to reduce the area from approximately 250 acres to 70 acres
  • Contouring the consolidated sludge to facilitate drainage and control erosion
  • Applying synthetic soil cover and seeding to promote re-vegetationlagoon_5
  • Discharge monitoring for compliance with NPDES limits
  • Erosion and sediment control
  • Regular inspections, groundwater monitoring and surface water monitoring


In addition, thriving wetlands and wildlife habitats were developed at the site during closure activities in cooperation with the U.S. Fish and Wildlife Service. The closed residual solid waste landfill continues to be managed through post-closure groundwater monitoring, site revegetation as needed, inspections and maintenance.

When preparing the 2016 Final Certification Report, Walden staff with a 20-year history on this closure project conducted a comprehensive site inspection of the storm water/erosion control systems, grading contours and vegetation elements which are integral to final closure of the residual waste lagoon. The certification also involved a detailed review of project documentation including aerial photographs, topographic maps, groundwater monitoring data, and surface water monitoring data. The current State residual solid waste regulations and those in effect at the time of closure plan approval were thoroughly evaluated to identify any changes affecting the closure standards. Walden determined that the lagoon had been closed in accordance with all applicable orders and regulations. Post-closure monitoring and inspections will continue to ensure that the area remains in good condition.


Walden Environmental Engineering provides a wide range of services including landfill closure and restoring sites for beneficial use. Please call us at (516) 624-7200 if you wish to discuss how Walden can assist with your project needs.