Silver Bow Creek Remediation and Restoration

By editor

Anaconda, Deer Lodge County, Montana

Silver Bow Creek courses for twenty-two miles through the rugged heart of southwestern Montana, flowing from the mineral-laden slopes of Butte to the Warm Springs Ponds near Anaconda. Its waters, once vibrant with life, carried for more than a century the detritus of industrious mining -- tailings, slag, and metals-laden effluents that leached from the veins of the Boulder Batholith, the vast granitic mass underlying these mountains. By the waning years of the twentieth century, the creek had become a desolate channel, its waters toxic and its bed barren of fish. The floodplain, once a complex assemblage of riparian vegetation, lay smothered beneath layers of contaminated soil. This was a landscape not of natural processes but of industrial residue.

The origins of this desolation lie in the relentless extraction of copper and other metals from the Butte mines, beginning in the late 1800s. The Boulder Batholith, formed over seventy million years ago during the Laramide orogeny, hosts some of the richest copper ores in the world. As miners excavated the veins of chalcopyrite, born from hydrothermal fluids circulating through fractured Precambrian and Paleozoic rocks, they produced vast quantities of waste. Flood events compounded the damage, washing heavy metals into Silver Bow Creek and depositing them across its floodplain. The metals, including arsenic, lead, cadmium, and zinc, poisoned the waters and soils. As early as 1983, biologists declared portions of the creek “biologically dead,” noting the absence of trout and other aquatic organisms.

In 1999, a concerted effort to heal this scarred landscape began under the auspices of the federal Superfund law. The Montana Department of Environmental Quality, joined by the Natural Resources Damage Program of the Montana Department of Justice and the Greenway Service District, undertook the immense task of remediation and restoration. This work, funded through a settlement with the Atlantic Richfield Corporation (ARCO), demanded not only financial resources -- over $120 million -- but also a deep understanding of geology, hydrology, and ecology. More than eighty workers labored annually over more than a decade, reshaping channel banks, removing contaminated sediments, and reestablishing native vegetation.

The remediation sought to address both the immediate and long-term threats to the creek’s ecosystem. The removal of mine tailings, some containing concentrations of metals far exceeding safe thresholds, was critical. Contaminated soils were excavated, isolated, or treated to prevent further leaching. A new stream channel was engineered to mimic natural geomorphic features, incorporating pools, riffles, and meanders to provide habitat for aquatic life. This channel was carefully designed to stabilize flow, reduce erosion, and facilitate the reestablishment of riparian plants such as Salix exigua (sandbar willow), Populus tremuloides (quaking aspen), and Carex nebrascensis (Nebraska sedge).

The results have been extraordinary by any measure. Trout, principally Oncorhynchus clarkii (cutthroat trout) and Salmo trutta (brown trout), have returned to stretches of Silver Bow Creek where none had swum for decades. The presence of mink (Neovison vison) and trumpeter swan (Cygnus buccinator) in the restored wetlands reflects a resurgence of biodiversity. These species indicate not merely survival but the renewed functionality of food webs and habitat connectivity. Deer (Odocoileus hemionus) and elk (Cervus canadensis) now graze along the creek’s corridor, drawn by the verdant growth of native plants.

Water quality monitoring reveals profound improvements. Before remediation, concentrations of metals in both surface water and groundwater often exceeded drinking water standards set by the Environmental Protection Agency. Today, sampling finds these contaminants below regulatory limits within the remediated areas. Aquatic insect diversity, a sensitive biological indicator, shows marked recovery. The algal assemblage, once dominated by metal-tolerant species, now includes taxa such as Cladophora and Ulothrix, which require cleaner water. These shifts in biological communities signify that the creek’s waters have regained the chemical balance necessary to support complex life.

The engineering of the new channel is a striking accomplishment. Vegetation has taken hold firmly on the banks, with willow and aspen rooting deeply in the reconstituted soils. Pools and riffles provide critical habitat for spawning and refuge during high flows. This design follows principles articulated by stream ecologists who recognize that channel morphology shapes habitat diversity and resilience. As the Montana Department of Environmental Quality has noted, “The success of this project is measured not only in pounds of metals removed but in the rebirth of a living stream.”

This project’s scale and success are remarkable compared to similar efforts across the nation. It is perhaps the largest stream remediation project of its kind in the United States, a fact recognized by awards from local, national, and international organizations dedicated to environmental restoration. The partnership between state agencies and the EPA demonstrates the capacity for coordinated action to heal landscapes damaged by industrial activity.

The story of Silver Bow Creek recalls words from William Clark, who in 1805 marveled at the region’s geology during the Corps of Discovery expedition: “The country is very mountainous and rocky and the streams are rapid and clear.” One imagines that had Clark seen Silver Bow Creek at the nadir of its contamination, he might have lamented the loss of such clarity. Yet today, the creek flows with renewed vigor, its waters once again clear enough to reflect the sky and support life.

Silver Bow Creek’s restoration reveals the power of meticulous scientific inquiry combined with dedicated labor. It underscores the importance of understanding geology and hydrology in crafting solutions that respect natural processes. More than a century after mining reshaped this valley, nature’s rhythms have begun to reassert themselves, carried on the waters of a creek that now courses with new promise.

See also

• Silver Bow Creek Remediation and Restoration at Anaconda, Deer Lodge County
• The Boulder Batholith and the Richest Hill on Earth at Butte, Silver Bow County
• Contributions of the Washoe Smelter at Anaconda, Deer Lodge County