Lucky Friday No 4, also known as Tailings Pond #4, is a private water resource structure located in Mullan, Idaho. Completed in 2010, this earth dam stands at a towering height of 132 feet, with a hydraulic height of 99 feet and a structural height of 131 feet. With a storage capacity of 624 acre-feet, Lucky Friday No 4 serves the primary purpose of storing tailings from mining activities in the area.

Managed by the Mine Safety and Health Administration, Lucky Friday No 4 has a high hazard potential due to its location near the Little North Fork and South Fork Coeur d'Alene River. Despite this, the dam has been assessed as satisfactory in condition, with the last inspection conducted in July 2020. The structure has no spillway and relies on a valve for outlet control. Its risk assessment categorizes it as high, highlighting the importance of implementing proper risk management measures in the event of emergencies.

Water resource and climate enthusiasts monitoring Lucky Friday No 4 should note its critical role in managing mining waste in the region. As a key infrastructure in Shoshone County, Idaho, this dam serves as a reminder of the delicate balance between resource extraction and environmental protection. With its high hazard potential and risk assessment score, ongoing monitoring and maintenance are crucial to ensure the safety and integrity of Lucky Friday No 4 for both the community and surrounding ecosystems.