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Pacific Southwest, Region 9

Serving: Arizona, California, Hawaii, Nevada, Pacific Islands, Tribal Nations

Solar Power Used to Pump Water through Wetlands at Apache Powder

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Located in Cochise County, Arizona, the Apache Powder Superfund site is approximately seven miles southeast of the incorporate town of Benson and 2.5 miles southwest of the unincorporated town of St. David. The site takes up approximately nine square miles and includes former operations known as Apache Powder Company, a former industrial chemicals and explosives manufacturer. Contaminants identified on-site include high concentrations of heavy metals in ponds, arsenic, fluoride and nitrate in perched groundwater, DNT in a drum disposal area, and nitrate in shallow wells including a domestic drinking well with 470mg/L nitrate. The primary exposure path for the contaminants is direct ingestion of the contaminated groundwater.

The perched groundwater zone is pumped and treated by forced evaporation (brine concentrator) and the waste water from the facility was also treated. The shallow aquifer was pumped and treated with the use of constructed wetlands. The wetland system covers about 4.5 acres, treats approximately 150gpm and was completed in 1997, saving over $15 million. The treated water is then pumped back into the aquifer.

When the water exceeds nitrate discharge limit of 30ppm, the water cannot be discharged to the aquifer. Thus, to power that pump which re-circulates water through the wetlands, solar power panels were installed. This solar power system consists of 12 Kyocera KC-120 photovoltaic panels with a 1,440 watt total capacity and one solar-powered Suncentric 7632 centrifugal pump. The system is capable of pumping 5 gallons per minute through 100 feet of a 2-inch fire hose with an elevation rise of approximately 10 feet. The system is used during daylight hours.

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