THE DIRT: The Page Repository Pt. 2 - History of the site

At first glance, the Page Repository seems like an unusual place for an environmental cleanup project. Why would engineers build a repository in what appears to be a wetland? 

The answer begins more than a century ago. 

Long before the repository existed, the site served as the Page Mine tailings pond, where fine mining waste was deposited for decades. Those tailings contained elevated concentrations of lead and other metals, creating a long-term source of contamination. 

When mining operations ended, the exposed tailings presented another problem. As they dried, fine contaminated particles became airborne, creating dust that posed a risk to nearby communities. 

To prevent that from happening, cleanup managers intentionally maintained water over much of the former tailings pond. A water-control structure, known as a weir, was installed on the west end of the Page Swamp to maintain a relatively constant water level. During wet periods, the tiered weir allows excess water to flow downstream. During dry periods, it retains water over the tailings, preventing them from drying out and becoming mobile through wind erosion. 

Over time, vegetation became established, wildlife colonized the area and portions of the former industrial site developed wetland characteristics. Although these wetlands resulted from historic mining activities and subsequent cleanup actions — not natural processes — they became regulated under the Clean Water Act. 

As engineers planned each repository expansion, wetland impacts were carefully evaluated through formal wetland delineations documented in the design reports. Federal law required those impacts to be compensated through wetland mitigation. Projects such as the West End Natural Infrastructure (WENI) project and later restoration work at Robinson Creek created and enhanced wetlands that replaced lost wetland functions while supporting the continued cleanup of contaminated mine waste. 

The concrete foundation visible today is another part of that long-term engineering strategy. The repository design calls for concrete or quarry rock beneath the disposal area to create a stable platform above the saturated ground. This foundation supports heavy equipment, minimizes settlement and helps isolate contaminated materials from groundwater. 

To ensure the foundation and waste placed at the Page Repository are not impairing water quality, 14 sites are sampled and monitored. Scientists monitor the site using eight groundwater monitoring wells and six surface water sampling locations. Water samples are collected twice each year — during both high-flow and low-flow conditions — and analyzed for metals as well as indicators of overall water quality, including dissolved oxygen, pH, conductivity and oxidation-reduction potential. Most groundwater monitoring occurs on the north side of the repository between the Page Repository and Interstate 90. Scientists compare results from downgradient monitoring wells to established prediction limits to determine whether water quality is changing over time. If a result exceeds those limits, it is verified through additional sampling and, if the trend continues, investigators conduct a detailed evaluation to determine the cause. This ongoing monitoring helps ensure the repository continues to protect surrounding water resources. 

Once the engineered foundation is complete, contaminated soils are placed in controlled lifts over many years. The repository ultimately will reach approximately 60 feet of engineered fill before reaching its design capacity. Throughout construction, engineers carefully limit how much material is placed each season to maintain stability and allow the underlying foundation to settle as designed. 

When repository operations are complete, the contaminated materials will be covered with an engineered cap that minimizes rain and snowmelt infiltration. Reducing the amount of water that moves through contaminated waste is one of the most effective ways to limit the movement of dissolved metals into groundwater and nearby streams. 

The Page Repository represents decades of careful engineering and environmental planning. What may appear to be a pile of concrete is actually a critical component of an engineered system designed to safely contain contaminated mine waste, protect water quality and support the continued cleanup of the Coeur d'Alene Basin for years to come.

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The Dirt is a series of informative articles focused on all aspects of cleanup efforts associated with the Bunker Hill Superfund Site. Our goal is to promote community awareness of contamination issues, to provide tools for protecting public health, and to keep the community informed of current and future cleanup projects. The Dirt is a group of committed and local experts from multiple agencies, including the Basin Environmental Improvement Project Commission, Panhandle Health District, Shoshone County, Silver Valley Economic Development Corporation and the Idaho Department of Environmental Quality.