In June 2021, Arizona’s sixth largest wildfire started just south of Superior. The fire burned east, south and west, consuming 180,000 acres of Sonoran desert terrain and obliterating some of Arizona’s most unique ecosystems. Once the fires were extinguished in July of 2021, the region was pummeled with record breaking monsoon storms during August and September, which created a new set of ecological and infrastructure problems for the Copper Corridor region.
During their May 12, 2022, Board of Supervisors meeting, the Pinal County Board of Supervisors voted to submit a letter to the Natural Resources Conservation Service, requesting help to repair damages to the Big Box Lake and Big Box Dam.
The Big Box Lake and Dam is important environmental infrastructure that helps to control stormwater run off from Devil’s Canyon and Mineral Creek, which eventually deposits into the the Gila River. The dam is a 150-foot concrete arch dam constructed in the 1970s. The Big Box Lake is part of a 2002 Clean Water Act Section 404 mitigation commitment by ASARCO; the lake provides 35 acres of open water and riparian habitat. Mineral extraction companies are often required to fund a variety of environmental mitigations to ensure there is a balance of preservation to the extraction uses.
According to the information provided by ASARCO to Pinal County, the lake is generally an open-water lake. Post-Telegraph Fire, the runoff from Devil’s Canyon and Mineral Creek deposited a tremendous amount of ash, sediment and woody debris that has damaged the lake and is posing risk to downstream infrastructure and Gila River habitat. With the debris and sediment in the lake, the lake has more of a pudding like consistency. The debris in the lake is also putting stress on the dam itself.
ASARCO reached out to Pinal County to assist with the request to NCRS, as ASARCO’s insurance does not cover the needed repairs and to qualify for assistance from the federal government the local political subdivision must request funding and support. The funding from the State of Arizona’s Telegraph Fire appropriations funding was not able to be utilized for this project.
Pinal County requested funding through NCRS to complete a three-phase project to restore the Big Box lake and dam. The first phase of the project will clear access to the Big Box Dam Control and removal of of surface debris by dredging 100,000 cubic yards and removal of sediment and debris from three areas along with cleanup of 50,000 cubic yards from the area of Devil’s Canyon. Phase two objective will be to continue cleaning of the Big Box Lake and remove debris along with an assessment of the dam’s construction. Phase three will clean the sediment deposited in natural channels by post-fire flood runoff.
Big Box Lake in 2019. The dam can be seen at the extreme bottom edge.
Big Box Lake in 2022 after the Telegraph Fire.
A map showing the location of Big Box Lake and Dam in relation to Devil’s Canyon and Mineral Creek.