Revised On: Feb. 8, 2024 - 9:00 a.m.

2022: BHP submitted Source Remediation Plan Site Characterization Updates for Copper Cities Deep Pit and Miami Unit.

2021: BHP completed the Miami Avenue Tailings Relocation project. Freeport McMoRan (FMMI) is conducting a sediment acidity and geochemical characterization program to evaluate the feasibility of alkali applications as a means to facilitate remediation of groundwater.  FMMI submitted the final evaluation of the effects of site waters on the stability of in situ treated sediment one year post test at the Live Oak Gulch in January. FMMI Submitted a draft workplan in July to develop site-specific criteria for aluminum, copper, and manganese in the perennial lower Pinal Creek.

2020: The results of large scale pilot tests in Live Oak Gulch were submitted to ADEQ by FMMI in July and September.

2019: BHP ceased mining operations and is continuing to develop reclamation (source control) plans for various facilities/properties within the Site. FMMI continued ongoing reclamation projects and development of the strategic plan for groundwater restoration. Effluent from the both the Town of Miami and City of Globe wastewater treatment plants is now being recharged immediately down gradient of the Kiser Basin wellfield to increase groundwater levels and improve the pumping capabilities of the extraction wells.

2013: FMMI worked on the Webster Lake In-fill Reclamation Project, which was completed in late 2015. FMMI has also started reclamation projects at the #1, #5/Davis Leach stockpiles and the #16 Waste Rock/Landbridge stockpile. Future reclamation projects at various leach, waste rock and tailings stockpiles are in the planning stage, which runs through to 2021.

FMMI (now the sole participant in the PCP) is developing a long-range strategic plan and conducting bench and pilot testing with the intent of optimizing and speeding up aquifer restoration at the site.

2011 – 2012: FMMI continues with construction of the Webster Gulch Reclamation Plan which, includes grading, covering, capping and revegetation of waste piles, re-routing of surface flows, and construction of subsurface drains. FMMI's 27/28 Leach Dump Infill Project includes a new leach solution impoundment for the 27/28 leach dump and capping, re-grading and re-vegetation of various waste rock piles. FMMI provided funding and technical assistance to the Town of Miami on their new wastewater treatment plant which was constructed at the base of the #3 Tailings Pile adjacent to Miami Wash. The new plant was commissioned in July of 2011 and turned over to the town in June of 2012. Treated wastewater (effluent) from the plant is intended for mine reuse, groundwater recharge and irrigation of the local golf course.

2010: The Pinal Creek Group has re-assessed the Pinal Creek flood elevations in the floodplain in response to flooding during the winter of 2009-2010 and in response to work conducted by a floodplain neighbor who was impacted by winter flooding. The work started in 2010 threatened to divert floodwaters towards the Pinal Creek Water Treatment Plant and potentially cause erosion and damage to embankments constructed by the Pinal Creek Group. The Army Corps of Engineers investigated the area which resulted in a work stoppage in the floodplain and the requirements for the neighbor to obtain a Clean Water Act 404 Permit.

The Pinal Creek Group was dissolved and FMMI’s Pinal Creek Project (PCP) became the sole owner/operator of the Pinal Creek groundwater remediation systems and responsible for the Groundwater Remedial Action Plan described in the 1998 Consent Decree.

2009: FMMI, formerly Phelps Dodge, began construction on the Webster Lake Infill Project and the 27/28 Leach Dump Infill Project.

2008: BHP has completed the removal and/or capping of numerous waste rock piles in the Copper Gulch drainage. Several piles were re-located to the BHP Miami In-Situ Mining facility where the waste rock will be leached. The well replacement program was completed in May, although the program is still available for testing (and possible replacement) of wells upon residents’ request.

2007: During calendar year, approximately 2,144,911 pounds of heavy metals were removed by the LPC Water Treatment Plant.

2006: Early in the year, the capping and revegetation of the BHP Miami Unit No. 2 Tailings was completed. In mid-2006, Phelps Dodge-Miami began reclamation of the slag pile along Bloody Tanks Wash. The pile was re-graded, capped and re-vegetated.

As of April, approximately 105 million pounds of heavy metals (aluminum, beryllium, cadmium, cobalt, copper, iron, lead, manganese, nickel, and zinc) were removed from aquifers at the site. This water was treated and released to Pinal Creek, reused at the mines, or evaporated at the mines. The perennial and ephemeral reaches of Pinal Creek, Miami Wash, and Bloody Tanks Wash were removed from the State’s list of impaired water bodies.

2005: In February, the Pinal Creek Group submitted a request to the ADEQ Water Quality Division to change the designate uses of a portion of perennial Pinal Creek. The request was to change the creek from aquatic and wildlife warm water to an aquatic and wildlife effluent-dominated stream. The Pinal Creek Group also requested dropping the fish consumption designation. In September, the Pinal Creek Group submitted a formal petition for the removal of the fish consumption designation from a portion of perennial Pinal Creek. Also submitted at that time, was a use attainability analysis for the fish consumption use. That same month, the Pinal Creek Group submitted a formal petition to re-classify a portion of Pinal Creek as effluent-dependent water.

In the spring, Bloody Tanks Wash, which is adjacent to the BHP Copper-Miami, was widened. The retaining wall that separated Bloody Tanks Wash from the former Miami Tailings No. 2 was removed and the tailings behind the wall were relocated onto the remaining tailings leftover from the previous reprocessing operation. The remaining tailings at the BHP Miami Unit lie outside of the 100-year floodplain.

During the summer, reclamation started of the remaining tailings at the BHP Copper-Miami Unit. The tailings began to be capped with clean fill, consolidated, regraded, and storm water channels and storm water and sediment ponds were being constructed. In the late part of summer, BHP began a site characterization/RI of the Solitude Tailings Impoundment located in Solitude Canyon (a tributary of Russell Gulch). The investigation included soil borings, test pits and groundwater monitor well installation. Samples were collected for chemical analysis, agronomic testing, geotechnical testing and stability analysis.

2003 – 2005: Investigations into soil and stream sediment contamination began. The Phase I sampling of soil and stream sediment was completed in April 2004. The results of the Phase I soil and stream sediment investigations were submitted in November 2005. A risk assessment was included as part of that submittal.

Major construction was completed and revegetation of the piles began during the spring of 2004. Runoff sampling conducted during 2003 after capping of waste rock and tailings piles has documented major improvements in runoff water quality.

In spring 2004, revegetation of the BHP Copper Old Dominion Mine waste rock and tailings was completed. In early summer of 2004, a failure of the Diamond H pit wall threatened the Diamond H Treatment Plant which was subsequently deconstructed. A temporary batch plant was constructed nearby to allow for continued treatment of acid-metal groundwater from the Kiser Basin containment well field. In late 2004, a new location for the treatment plant was selected and in September 2005 design plans were prepared and submitted for review. The plant was relocated near the southeast corner of the Diamond H Pit. Stability analyses were conducted and the critical components of the plant will be constructed outside of any areas of high for slope and rock failure.

2002: Remedial construction of the engineered cap of the BHP Copper Old Dominion Mine tailings and waste rock began to prevent acid-metal runoff from reaching upper Pinal Creek began.

2001: In January, a groundwater barrier (soil-cement-bentonite slurry wall) was constructed across LPC, which serves as the downstream containment of the plume. Full scale groundwater extraction began just above the barrier for neutralization and metal removal in the LPC Treatment Plant. In May, a second treatment plant (Diamond H Treatment Plant) was completed to treat water captured from the Kiser Basin (upstream) containment. In June, a groundwater well field (Kiser Basin well field) that serves as the upstream containment of the acid-metal plume was completed, and groundwater extraction began. 

1999: In November, the LPC Treatment plant was completed and groundwater extraction at the leading edge of the acid-metal plume began. 

1997 – 1998: A Consent Decree governing the clean up was signed in 1997, and approved by the U.S. District Court in 1998. A WQARF administrative order to implement an early response action (ERA) was signed in 1998 to expedite construction of the LPC treatment plant, begin groundwater extraction at the leading edge of the acid-metal plume, and prevent further degradation of the perennial reach of Pinal Creek.

Initial source control remedial investigations and associated FSs were completed by 1998. Numerous source and exposure control actions have been implemented at the various mine Sites, including facility upgrades, groundwater extraction, groundwater containment, removal from service of solution impoundments, capping/covering of tailings, management controls, institutional controls, storm water controls and many others.

In October 1998, the site was placed on the WQARF Registry with an eligibility and evaluation score of 97 out of 120.

1997: Ecological and Human-Health risk assessments and the groundwater FS and Recommended Remedial Action Plan (RRAP) were completed by 1997. The RRAP proposed groundwater extraction at two locations, upstream and downstream containment of the plume, construction of two lime neutralization treatment plants, private well replacement, source control, and special well construction and abandonment requirements. 

1994: The Pinal Creek Group began a private well testing and replacement program, which continues today. 

1986 – 1990: Source control actions began in 1986 under order from EPA for violations of the Clean Water Act. In 1989, the site was listed on the old WQARF Priority List by the state of Arizona. In 1989, the Pinal Creek Group (a consortium of Phelps Dodge, BHP Copper Inc., and Inspiration Consolidated Copper Co.) was formed to conduct the RIs and begin remedial actions. The groundwater RI began in 1990. In 1990, the interim remedial action (IRA) which consisted of groundwater extraction from the alluvial aquifer at four locations, began. 

1979 – 1981: The first area-wide investigation of groundwater and surface water contamination was conducted in 1979-1981. Widespread groundwater and surface water contamination was documented. Releases of contaminants and hazardous substances have occurred from all of the major mining and processing sites from a variety of different sources, including, but not limited to, process solution impoundments, tailings piles, leach dumps, waste rock piles, spills, and as storm water runoff. Erosion of waste piles, especially tailings piles, has also resulted in the release of contaminants to water courses. Particulate fallout of wind-blown tailings and from copper smelters in the area has also contributed to the spread of contamination at the site. 

1878 – 1970: Mining and mineral processing began in the Globe-Miami area in 1878 with the discovery of silver in the Globe Hills. By 1893, copper had replaced silver as the main commodity produced in the district, and continues to be today. Releases of contaminants from mine and processing sites started shortly after mining, milling, and smelting began.

Groundwater contamination was first discovered in the 1930s in the alluvial In the 1940s, groundwater contamination was discovered in the alluvial aquifer of Bloody Tanks Wash. The first public supply wells were contaminated in the late 1940s, and private wells along LPC were first impacted in the 1970s.