Environmental Protection Agency (EPA) #: AZD008399263

Superfund National Priority List (NPL) Placement: Aug. 30, 1990

Location

The Apache Powder Superfund Site is located approximately seven miles southeast of the incorporated town of Benson and two-and-a-half miles southwest of the unincorporated town of St. David in Cochise County, Arizona. Study area covers approximately nine square-miles and includes 1,600 acres of land owned by Apache Nitrogen Products Inc. (ANPI), formerly known as the Apache Powder Company. The San Pedro River bounds the eastern side of the site, running from the southeast corner of the property toward the northwest | View Map >

Contaminants of Concern (COCs)

Groundwater | Nitrate and perchlorate

If you are connected to a public water system (PWS) there is little to no risk of impact from exceedances because the water is filtered through the PWS for residential and business use | View Drinking Water Notices >

If you have a private well in the vicinity of the exceedance, we encourage you to test the well water. 

Not sure what to test for? | Learn More >

COCs at the site may change as new data become available.

Action Taken

Use of a constructed wetland to treat water coming from a nitrite-contaminated shallow aquifer, monitored natural attenuation (MNA) for groundwater outside the capture zone of the wells, and institutional controls (ICs) have been in place since 2008. A new extraction well began pumping to the treatment lagoons (wetlands) in July 2018 and a geophysical study (Electrical Resistivity and Induced Polarization) was conducted the same month.

Status

Ongoing remedial work continues at ANPI. The site has three major ongoing remedial actions as identified in the 2008 Preliminary Close-Out Report. The current selected remedies are:

Northern Area Groundwater 


While the wetlands achieved full-scale operation in 2004 with extraction well SEW-1, two new wells - SEW-2 and SEW-3 - were installed and began full-scale operation in July of 2018 and March 2021, respectively. During the winter months, extraction from SEW-2 or SEW-3 is decreased or stopped in an effort to reduce nitrate loading in the wetlands to maintain its efficiency. 

Southern Area Groundwater
The Southern Area has achieved clean up levels. Long-term monitoring and ICs for the Perched System and shallow aquifer are ongoing.

Contaminated Soils 
Excavation and off-site disposal or on-site treatment or encapsulation, including ICs for other contaminated soils detected during confirmatory soil sampling in the Legacy Soils Area was conducted. Clean up of Legacy Soils was deemed complete in 2019; no contamination was left onsite.

EPA and ADEQ are working with ANPI to update the Operation and Maintenance Plan, and maintain or improve the efficiency of the wetlands. This site is subject to programmatic five-year reviews and the next review will be conducted in 2027.

Learn more about this Superfund site on the EPA website | View >