2023: Site inspection was conducted.

2022: Site inspection was conducted. The water supply well pumps for the irrigation system were replaced.

2020 – 2021: Site inspection was conducted each year.

2019: Repairs were made to the irrigation system.

2017 – 2018: Site inspection was conducted each year.

2013 – 2015: Site inspection was conducted.

2008 – 2009: Site inspection was conducted.

2007: Repairs were made to the slope irrigation system and additional grass was hydroseeded on the slope. Groundwater monitoring of wells in the vicinity did not detect lead or arsenic at concentrations above drinking water standards.

2005: Grass was planted during the summer on the soil cover.

2001 – 2002: At the request of local property owners, additional soil sampling was conducted between March and July 2001 to further define the vertical and horizontal extent of the contamination. During the course of the investigation, laboratory results indicated that the limits of impacted soil were considerably further south than had been originally estimated. The tailings were found on an additional three properties. The results of the supplemental soil sampling are summarized in the October 2002 soil characterization report.

Based upon the new data, the December 2000 plans and specifications to implement the soil remedy were modified and sent out to bid May 2002. In December 2002, the construction contractor mobilized to the site.

2000: In December, a final Remedy Design Submittal (100%) was prepared.

1999: A human health risk assessment (HHRA), dated June 25, 1999, was performed to evaluate the no action alternative and soil cover alternatives. The HHRA concluded that the no action alternative may result in significant risk to future on-site residents. The report also concluded that this significant risk will be eliminated if the soil cover alternative is implemented provided the soil cover is maintained and remains in place.

In September, ADEQ issued a ROD that formally adopted remedial alternatives for groundwater and soil at the site. The selected groundwater remedy consists of groundwater monitoring and institutional controls for installing new wells within the control area defined in the ROD. The selected soil remedy consists of excavation, consolidation, and placement of a soil cover and associated stormwater controls.

1997 – 1998: Beginning in 1997, the Arizona Department of Environmental Quality (ADEQ) conducted a remedial investigation (RI)/ feasibility study (FS) to determine the nature and extent of current and future effects of the contamination on the groundwater. The site was placed on the WQARF Registry in April of 1998 with an eligibility and evaluation score of 65 out of a possible 120. Results of these investigations are summarized in the July 10, 1998, RI report and the Aug. 14, 1998, FS report.

ADEQ characterized the nature and extent of current and potential future effects of contamination in soil. The results are summarized in the Oct. 5, 1998, Tailings Characterization Report. Also in October 1998, the proposed remedial action plan (PRAP) was prepared to evaluate the groundwater and soil remedial cleanup alternatives to address the potential human health risk posed by the metals in the soil at the site. The selected alternative was excavation, consolidation, and capping of the tailings on the site. 

1863 – 1962: Milling and stockpiling of gold ore from the Vulture Mine took place from 1863 until the early 1900s. The stockpiled tailings were processed briefly from 1957 to 1962. The original milling process consisted of crushing and flotation. The concentrates were stockpiled at the Vulture Mill and processed using cyanide in the early 1890s.