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Wetland Design

Windmill

Wetlands Vegetation

Cleanup Objectives: Remediate surface and ground water containing high concentrations of metals, nitrate, and explosives at a 1,100-acre site (now known as Apache Nitrogen Products, Inc.)

Green Remediation Strategy: Employ a hydraulically driven constructed wetland system, solar energy for shallow ground water recirculation, wind energy for de-watering, and native soil covers

• Engineered a 4.5-acre tiered wetlands structure relying on natural gradients to drive water through treatment ponds in the site's northern half
• Used a 1.4-kW photovoltaic (PV) system equipped with a solar-powered centrifugal pump to promote water recirculation in the wetlands system
• Used a mini PV unit to power a flow meter that measures the volume of water moving through the wetlands system
• Injected wetlands-treated water directly into the alluvial aquifer
• Capped 10 abandoned pond areas in the site's southern half through construction of soil covers made of native materials
• Installed a windmill to generate electricity for powering pumps needed to de-water a perched ground water zone underlying the capped areas

Results:

• Obtained sufficient PV-generated electricity to recirculate ground water in the wetlands system (through 100 feet of two-inch hosing elevated 10 feet from ground surface) at a rate of 5 gallons per minute
• Operated the recirculation system only during daylight hours, which matched peak performance of contaminant degradation mechanisms occurring in the wetlands
• Reached the standards for treated water discharge after five years of operation, allowing shut-down of the recirculation system
• Avoided air emissions associated with consumption of grid electricity during five years of ground water recirculation
• Treated over 400 million gallons of ground water that had passed through the wetlands by early 2009, removing over 497,000 pounds of nitrate-nitrogen
• Reduced the electricity costs for ground water recirculation and de-watering by approximately 66%, when compared to the expense of installing new power lines to the grid in this remote area and purchasing the needed electricity
• Completed remedial construction in September 2008, with ongoing monitoring
• Continuing to achieve nitrate-nitrogen concentrations below the 5.0 mg/L ground water standard and 10 ug/L drinking water standard, as compared to pre-remediation concentrations reaching 570 ug/L
• Continuing to recharge the aquifer with clean water exiting the wetlands system

Property End Use: Nature reserve

Point of Contact: Andria Benner, U.S. EPA Region 9

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