Number 4 is a private earth dam located in Pima, Arizona, with a primary purpose of storing tailings. Standing at a height of 40 feet and a length of 28,708 feet, this dam has a storage capacity of 12,730 acre-feet. Despite being designated as a high hazard potential structure, the condition assessment of Number 4 is currently not available, raising concerns about its safety and potential risks in the event of a failure.

Operated by the Mine Safety and Health Administration, this dam has not been inspected or assessed for its condition in recent years. With no emergency action plan in place and limited information on risk assessment or management measures, there is a pressing need for increased scrutiny and monitoring of Number 4. As climate change continues to impact water resources and infrastructure stability, it is crucial for water resource and climate enthusiasts to advocate for stronger regulations and oversight to ensure the safety of structures like Number 4 and protect surrounding communities from potential harm.