Industrial Landfill

Roux Associates was retained by the landfill owner, a multi-national chemical company, to evaluate and develop cost-effective alternative landfill cover. Following the completion of hydrogeological and geochemical characterization investigations, Roux personnel developed an innovative solution consisting of three key elements:

   1. The design and retrofit of a staged Constructed Treatment Wetlands (CTW) into the
         existing 16-acre jurisdictional wetlands;
   2. The installation of a Phytotechnology Cap (Phyto Cap) over key landfill areas; and
   3. The consumptive recirculation/re-use of treated CTW water to minimize discharge.

The multi-phase project was designed by Roux in 1998, with the CTW constructed in 1999. The Phyto Cap, consisting of 18,500 specialty tree species, was installed in 2001. The ENS solution is passively operated and has the capacity to treat combined leachate/stormwater runoff flows of up to 150,000 gallons/day. The CTW can retain and treat runoff from storms in excess of 100-year return frequency. Performance to date have been excellent, reducing zinc levels below 0.1 mg/L while eliminating acidity and reducing iron to less than 3 mg/L.

The total cost of the CTW/Phyto Cap was approximately $2 million, saving our client tens of millions of dollars in capital costs and potentially millions more in O&M costs. Further, since the CTW improved the water quality of the impacted wetlands, the cost of restoring the wetlands was also saved. The system was approved by the USCOE, US Fish and Wildlife Service, USEPA and the Virginia Department of Environmental Quality (VADEQ).

In addition to the very large cost savings, an analysis was performed comparing the sustainability attributes of the implemented CTW/Phyto Cap to the proposed RCRA Cap/leachate treatment system. Both remediation alternatives were evaluated in terms of energy consumption, greenhouse gas emissions, water treatment, carbon capture and sequestration, and land use benefits across the life span of each technology, including mobilization --> construction --> demobilization as well as 30 years of operation, maintenance, and monitoring.

It was determined that the CTW/Phyto Cap will consume 9,754 MMBTU of energy across its life span, while the proposed RCRA Cap/leachate treatment system would require 138,472 MMBTU of energy. The CTW/Phyto Cap energy requirements are equivalent to the annual electricity needs of 224 single-family homes versus the annual electricity needs of 3, 177 single-family homes for the proposed RCRA Cap/leachate treatment system.

These energy requirements amount to greenhouse gas emissions of 1,128 metric tonnes carbon dioxide equivalents (CO2e) for the CTW/Phyto Cap and 16,450 metric tonnes CO2e for the proposed RCRA Cap/leachate treatment system. However, carbon sequestered over thirty years by the specific trees planted in conjunction with the CTW/Phyto Cap results in avoided emissions of 11, 104 metric tonnes of CO2e. Therefore, the total greenhouse gas emissions avoided by the CTW/Phtyo Cap are 9,975 metric tonnes CO2e, and the difference between the two systems is 26,425 metric tonnes CO2e. This difference is equivalent to taking 4,800 average passenger cars off the road for one year.


This comprehensive, landscape-based approach to sustainable remediation also provided the following benefits: existing natural systems and hydrology were maintained, water re-use opportunities were enhanced, additional wildlife habitat was created, additional air purification was provided, chemical requirements were eliminated, educational value was provided, a highly valued open space area aesthetically preferable to conventional treatment methods was created, additional soil stabilization was provided, and Site redevelopment plans were further supported.