Pacific Southwest, Region 9: Superfund
Serving Arizona, California, Hawaii, Nevada, the Pacific Islands, and Tribal Nations
Asarco Hayden Plant
EPA #: AZD008397127
County: Gila and Pinal
City: Hayden and Winkelman
Congressional District: 04
Other Names: Hayden Smelter
In October 2016, EPA issued a Site Updates Fact Sheet (click here).
On November 2, 2016, EPA hosted two community meetings. More information about the meetings can be found below.
On this page
Description and History
NPL Listing History
NPL Status: Non-NPL
Final Date: 05/27/08
The ASARCO Hayden Plant Site is located 100 miles southeast of Phoenix and 50 miles northeast of Tucson. The site consists of the towns of Hayden and Winkelman, and nearby industrial areas including the ASARCO smelter, concentrator, former Kennecott smelter and all associated tailings facilities in the area surrounding the confluence of the Gila and San Pedro Rivers. Contamination at the site is caused by historical smelting and processing activities as well as ongoing operations.
Hayden has a population of approximately 840. Based on a 2007 reconnaissance estimate, there are a total of 383 structures in the town of Hayden. Winkelman has a population of approximately 435 people and 215 structures. The school complex for the towns of Hayden and Winkelman is located on the northern edge of Winkelman.
The site is currently administered through an Administrative Settlement Agreement and Order on Consent between EPA, ASARCO and ADEQ.
The ASARCO Ray Complex is composed of the Ray mine and the Hayden Smelter. The Ray Mine has extracted copper since approximately 1880. One of the first owners of the mine was Ray Copper Company. This company transitioned to Ray Consolidated Copper Company (RCCC) with the acquisition of Globe Mines Exploration Company, Ltd., and Gila & Ray Copper Mines in 1898 and 1906, respectively. Winkelman was founded in 1887 and Hayden was founded in 1909 as a company town to provide housing for workers supporting the mining and smelting operations
The ASARCO Hayden smelter began operations to process ore from the Ray Mine in 1912. In 1933, Kennecott bought the Ray Mine from RCCC. The ASARCO Hayden smelter stopped receiving ore from Ray Mine in 1958, at which time Kennecott began operation of its own Hayden smelter. The ASARCO Hayden smelter began receiving concentrates from Pima, Duval, Bagdad, Cyprus, Silver Bell, and Mission mines after 1958.
In 1974, the 1,000-foot double-shell concrete stack was built by ASARCO to discharge exhaust gases from the smelting operations, which replaced the 300-foot reverberatory furnace stack and 250-foot converter stack. The Kennecott smelter was shut down in 1982. ASARCO completed modernization of its Hayden smelter in 1983, which included construction of a second sulfuric acid plant to capture and reuse sulfur dioxide (SO2) emissions produced during smelting, and construction of a wastewater treatment plant to recover process water from the sulfuric acid plant for reuse. After the modernization in 1983, ASARCO’s smelter renewed processing ore from the Ray Mine, and ASARCO bought the Ray Mine Division from Kennecott in 1986.
Tailings disposal in Impoundments AB/BC, started in 1910 at a rate of approximately 4,000 tons per day (tpd). By 1952, the rate had increased to approximately 16,000 tpd, followed by an increase to 21,000 tpd in 1960. A slope failure occurred in 1972 that measured 500 feet across and 30 to 50 feet deep. Another failure occurred in 1973. At the time of failure, water was seeping out of failed portions of the impoundment. In 1982, construction of Tailings Impoundment D began with an 8,700 feet long, 48 feet high starter dike.
The former Kennecott Copper Company (Kennecott) smelter area, located on the north edge of Hayden and north of the concentrator facility, underwent demolition work beginning in 2004. Currently, the area consists of miscellaneous building debris, storage tanks, foundations, and an abandoned slag dump northwest of the former smelter. The 600 foot tall former Kennecott smelter stack was not demolished. The lime and filter plant facilities are still actively operated.
At the currently operating Ray Complex operations, sulfide ore undergoes primary crushing at the Ray Mine and is transported by rail to the Hayden operations. At the 27,400 tons per day (tpd) Hayden concentrator, the ore is off-loaded at the track hopper and passed through secondary crushing processes where it is further reduced in size. The ore is transported by Conveyor 9 (a portion of which is overhead) to rod mills and ball mills where the ore is pulverized to sand size or smaller, and then converted to slurry. The ore slurry is directed to froth flotation tanks where the copper minerals are separated from the bulk of the copper ore. The copper-rich concentrate, which contains about 25 to 30 percent copper, is sent to the smelting operation for further processing (the smelter also receives concentrates directly from the Ray Mine operations). The tailings waste from the froth flotation process is sent to the thickeners, and then transported as slurry in the tailings pipeline and deposited on Tailings Impoundments AB/BC and D.
The copper-rich concentrates are delivered to the 720,000 tons per year (tpy) Hayden smelter, located about 2,000 feet east-northeast of Hayden. The smelter facility includes an oxygen flash furnace, converters, anode casting, oxygen plant, and acid plant. The concentrates are unloaded and blended with fluxes, then transferred to fluid bed dryers where they are dried and stored prior to being introduced into the oxygen flash furnace. The copper concentrates ignite, melt, and partition to produce matte (approximately 55 percent copper) and slag.
The matte from the flash furnace is subsequently processed in converter furnaces to remove additional impurities and produce blister copper (approximately 98.5 percent copper). Finally, the blister copper is further processed in anode furnaces to produce copper anodes that are 99 percent pure. The anodes are shipped offsite for final processing.
The active smelter building is approximately eleven stories tall, and a portion of the air emissions are released to the atmosphere through a 1,000-foot-tall stack. During the smelting process, sulfur from the ore is oxidized to form SO2 gas, which is converted to sulfuric acid in the sulfuric acid plant. Slag from the smelter operations is transferred to open waste stockpiles located immediately southeast of the smelter operations area. Treated wastewater and other process waters are discharged to containment pond CP-1, located east of the smelter. Decant water from the tailings impoundment is discharged to retention ponds located east of Tailings Impoundment AB/BC, where it is reclaimed into the process operations. Process/storm water management consist of several drainage and surface water impoundment located throughout the concentrator and smelter areas.
Tailings Impoundment AB/BC is located south of State Route 177 and north of the Gila River, and extends for approximately 2.5 miles. Tailings Impoundment AB/BC has a maximum width of one mile and a maximum height of 200 feet. The newer Tailings Impoundment D is located south of the Gila River, extends for a length of approximately two miles, has a maximum width of 1,500 feet, and a maximum height of 150 feet.
Contaminants and Risks
- Surface Water
- Soil and Sludges
- Environmentally Sensitive Area
Almost 100 years of smelting activities at this site has deposited lead, arsenic, and copper across residential and industrial soil areas. Residential soil sampling in Hayden indicate the highest concentrations of lead, arsenic and copper are located on the north edge of town, near the old Kennecott smelter and on the east side near the concentrator and the number 9 conveyor. Arsenic soil concentrations in Hayden range from near background (12.5 mg/kg) to 540 mg/kg. Lead in Hayden ranges from near background (48 mg/kg) to 7,250 mg/kg. Copper varies from below a background of 1,270 mg/kg up to 39,700 mg/kg. In Winkelman, contamination is lower then Hayden and centered along the highway 177 area and along the railroad tracks on the south side of town. Samples from the school complex on the north end of Winkelman indicate the school has relatively low soil concentrations, with all concentrations below proposed remediation levels.
Groundwater beneath the smelting and slag deposition areas of the site is impacted by arsenic, manganese, sulfate, selenium and molybdenum. Tailings impoundment along the Gila River have caused elevated levels of contaminants to be discharged into surface and groundwater.
Despite the 1,000 foot tall stack, air quality monitoring in the two towns measured elevated levels of arsenic, lead, copper, cadmium and chromium from site operations. For example, the average levels of arsenic in Hayden air is .0239 micrograms per cubic meter (ug/m3) while areas unaffected by mining, such as the Organ Pipe National Monument area southwest of Tucson, have average concentrations of .0004 ug/m3 or less. These concentrations indicate that the arsenic in Hayden air is about 60 times above what would be expected in an area unaffected by smelting activities. The high levels in Hayden were typically measured when the wind was blowing from the smelter towards town. In Winkelman, the average arsenic air concentration (.00796 ug/m3) is 20 times higher then the Organ Pipe area and is likewise elevated when the wind direction is from the smelter. The high arsenic concentrations are not always associated with high dust levels.
Residential areas are located close to industrial areas and therefore have a high level of exposure. These areas include: the concentrator over the fence from the public park/library/swimming pool area; the number 9 conveyor which travels over residential properties; and the smelter which is 2000 feet from Hayden and 1500 feet from the school complex near Winkelman.
The site is located along the intersection of the Gila and San Pedro Rivers, which is also a prime habitat for the Southwest Willow Flycatcher, a federally listed endangered species.
Investigation and Cleanup Activities
EPA has completed its Work Plan for a Phase II Remedial Investigation (“RI”) at the ASARCO Hayden Plant Site and ASARCO is implementing the Work Plan. EPA took over the writing of the Phase II RI Work Plan following ASARCO’s failure to develop an appropriate Work Plan, as required by a 2008 Administrative Order on Consent (“AOC”) entered into by ASARCO, EPA, and ADEQ.
The Phase II investigation is evaluating the nature and extent of contamination due to historic and current copper smelting operations in the following environmental media: air, surface soils, groundwater, surface water, stormwater runoff, process water, and sediments. The results of this investigation will lead to any additional needed soil, water, and air cleanup activities. The surface soil investigation includes industrial areas and certain residential areas that were not fully remediated during the Phase I work (see below). Areas to be investigated include Asarco industrial properties and surrounding areas in the towns of Hayden and Winkelman, Arizona.
Activities being conducted include:
- - Comprehensive air quality investigation for metals (including lead and arsenic) and particulate matter;
- Sampling of tailings piles, slag, stockpiled materials, and discolored surface soils;
- Sampling of sediments in washes, ponds, impoundments, and other drainages;
- Sampling to establish background soil conditions in upland areas;
- Additional surface water sampling in the Gila and San Pedro Rivers to characterize inputs from the tailings piles and groundwater;
- Stormwater sampling to characterize contaminants from ASARCO operations dispersed via stormwater drainage;
- Sampling of process water from the tailings piles, reclaim ponds, facility discharge points, and tailings seepage areas to evaluate contaminant levels and potential groundwater and surface water impacts; and
- Installation of six new groundwater monitoring wells and two years of quarterly groundwater monitoring.
In 2002 ADEQ, on behalf of EPA, performed an Expanded Site Investigation (ESI) which primarily included soil sampling around the conveyor belt that runs near homes and disperses ore dust in residents’ yards. Residential yards were sampled on Smelter Road, Hillcrest Avenue, Sunnyslope Road, Ray Avenue, Velasco Avenue, and Garfield Avenue. Of the 27 sample locations in Hayden:
-Arsenic levels exceeded the Residential Soil Remediation Level (R-SRL) of 10 mg/kg at 26 locations (maximum of 67.4 mg/kg),
-Copper levels exceeded the former R-SRL of 2,800 mg/kg (note that the R-SRL was increased to 3,100 mg/kg in 2007) at 24 locations (maximum of 55,100 mg/kg) and
-Lead levels exceeded the R-SRL of 400 mg/kg at three locations (maximum of 851 mg/kg). In addition, cadmium, mercury, and zinc levels in several samples were reported as elevated compared to the average background concentrations, but were not detected above their R-SRLs. The ESI concluded that the elevated concentrations of metals were the result of ASARCO operations. Elevated concentrations at ASARCO operations were shown, in sediment analysis from containment pond CP-1 (which collects stormwater, wastewater, and process waters from the smelter area) to contain elevated concentrations of arsenic, cadmium, chromium, copper, lead, mercury, and zinc.
A 2004 Removal Assessment by the EPA Emergency Response Section sampled soils in the Hayden, Kearney, and Winkelman areas to further evaluate impacts from Site operations. Kearney did not contain elevated levels of contamination. Soil samples were collected at a total of 51 locations in Hayden and 69 locations in Winkelman from randomly selected locations within an established grid. Of the 51 samples in the Hayden area, 40 exceeded R-SRLs including arsenic at all 40 locations (R-SRL of 10 mg/kg, maximum of 91 mg/kg), copper at 29 locations (R-SRL of 2,800 mg/kg,maximum of 11,400 mg/kg), and lead at one location (R-SRL of 400 mg/kg, 463 mg/kg). In Hayden, sample locations revealing elevated copper and lead concentrations generally coincided with locations showing high arsenic concentrations, with the highest concentrations typically concentrated close to the Conveyor 9 area, east of the Conveyor 9 area near Power House Wash, concentrator operations and the former Kennecott smelter area.
Of the 69 samples from the Winkelman area, the SRL was exceeded at 16 locations for arsenic (maximum of 320 mg/kg), seven locations for copper (maximum of 19,000 mg/kg), and three locations for lead (maximum of 485 mg/kg). In Winkelman, elevated arsenic levels were generally located along and south of State Route 177. The study further concluded that the elevated concentrations of metals found throughout Hayden and Winkelman are likely the result of contamination dispersed from ASARCO operations.
Cleanup Results to Date
ASARCO, under EPA direction, has removed soil from over 260 residential properties in Hayden and Winkelman between March 2008 to October 2009. These yards had high concentrations of arsenic, lead or copper.
Potentially Responsible Parties
Potentially responsible parties (PRPs) refers to companies that are potentially responsible for generating, transporting, or disposing of the hazardous waste found at the site.
At this site, Asarco LLC and Kennecott Minerals Company are PRPs.
Documents and Reports
Public Information Repositories
The public information repositories for the site are at the following locations:
Hayden Public Library
175 5th Street
Hayden, Arizona 85235
EPA Site Manager
Mail Code SFD
75 Hawthorne Street
San Francisco, CA 94105
EPA Community Involvement Coordinator
Mail Code SFD-6-3
75 Hawthorne Street
San Francisco, CA 94105
EPA Public Information Center
After Hours (Emergency Response)