Established by the US Environmental Protection Agency (EPA) in 1983, the California Gulch Superfund Site encompasses about eighteen square miles in central Lake County, including the city of Leadville. One of the nation’s first Superfund sites, it was created to clean up heavy-metal pollution caused by mining and smelting in the area during the late nineteenth and early twentieth centuries.
California Gulch is a tributary of the Arkansas River, whose headwaters are located near Leadville. The California Gulch Site is divided into twelve “operable units” (OUs), or individual areas requiring cleanup. They include abandoned mines, tailings piles (waste materials leftover from mining), residential areas, and smelter sites. In addition to the EPA, multiple federal, state, and local agencies are involved in managing the site, including the Bureau of Reclamation, Colorado Department of Public Health and Environment (CDPHE), and the Lake County Commissioners. Throughout the site’s history, cleanup activity has included the construction of catchment ponds, rock-and-soil plugs in abandoned mines, soil removal from residential areas, and the establishment of two water treatment plants that ensure safe drinking water for Leadville.
Shortly after it was created, the EPA placed California Gulch on the National Priorities List (NPL), which prioritizes cleanup activities among the nation’s Superfund sites. Since then, nine of the twelve OUs have been partially removed from the NPL, though cleanup and remediation continue to the present. As of 2021, the EPA reports that “cleanup is complete at over 90 percent of the site.”
Mining in California Gulch dates to 1860, but heavy industrial mining and smelting did not begin until a silver boom kicked off there in the late 1870s. Silver mining fell off after the price of silver crashed in 1893, but mining of base and industrial metals such as lead, copper, zinc, and molybdenum continued in the area through the twentieth century. The Climax Molybdenum Mine still operates today and is the county’s largest employer, though it is located well outside the Superfund site and will eventually require its own environmental remediation.
Throughout the area’s mining history, dozens of mines were opened, exposing tons of metal-bearing rock to open air. This change began the natural process of acid mine drainage, where oxygen reacts with sulfides in mineral-bearing rocks to produce sulfuric acid and dissolved iron that then flow into local water sources. The acid further dissolves other metals, such as copper and lead, and the metal-laden water poses a threat to wildlife, ecosystems, and in some cases, human water supplies.
In addition, smelters—facilities where ore is made molten to extract precious metals—produced a waste product called slag, which consists of unwanted heavy metals that contaminate soil and water. The first smelter in California Gulch was built in 1875; additional smelters went up in 1878 and 1879, with a maximum of sixteen eventually operating in the area (though most closed in 1880 after the arrival of the Denver & Rio Grande Railroad). The American Smelting and Refining Company (ASARCO) began operating smelters in Leadville in the early twentieth century and, owing to multiple lawsuits in the mid-2000s, has assumed responsibility for cleanup activities at several OUs in the California Gulch Site.
In 1983 a local rancher, Bernard Smith, reported orange water in the Arkansas River that made his livestock sick and stunted his hay crop. Media reports got the attention of the EPA, and the agency quickly designated Leadville as a Superfund site. From the beginning, the designation irked locals, many of whom believed that a Superfund site would cause property values to plummet, destroy the area’s mining heritage, and damage the town’s ability to recover economically from the mining era. It did not help that the EPA arrived at the same time as the Climax Molybdenum Mine—outside the Superfund site—was drastically reducing its operations and laying off many residents. The lengthy timespan of cleanup—several decades—has only exacerbated residents’ resentment of the site.
Upon establishing the California Gulch Site, the EPA identified the “most serious water quality problem” as “acid mine drainage from the Yak Tunnel,” a 3.4-mile drainage tunnel connected to seventeen abandoned mines, which empties into California Gulch. The tunnel was leaching water containing “high concentrations of dissolved metals, including iron, lead, zinc, manganese, and cadmium.” The agency noted that this water could potentially contaminate “domestic ground water supplies” as well as have “adverse impacts on fish in the Arkansas River, and livestock and crops grown” on land irrigated by the river. As such, the Yak Tunnel was designated “OU1” at the California Gulch Site.
To remedy the dirty flow from the Yak Tunnel, in 1992 the EPA built the Yak water treatment plant. The plant continues to treat water today, removing some 200 tons of metal each year. It is operated by the Newmont Mining Company, which was identified as a responsible party for the pollution. The EPA also built retention ponds beneath some 2,000 piles of waste rock to catch heavy-metal runoff from abandoned mines before it enters local water sources.
In 1991, following a lawsuit by the Sierra Club, the US Bureau of Reclamation built a water treatment plant at the north end of the Leadville Mine Drainage Tunnel, which carries contaminated water from the Superfund site to the east fork of the Arkansas River north of Leadville (the plant is not part of the Superfund site). The tunnel made headlines in 2008, when multiple underground cave-ins caused the blockage and buildup of more than 1 billion gallons of metals-laden water that threatened to burst out and inundate the city. The event prompted a state of emergency declaration by the EPA and county officials but was remedied before a major blowout occurred.
With financial assistance from ASARCO, soil remediation in residential and former industrial areas, including smelter sites and the old Denver & Rio Grande Railroad yard, began in 1995 and was mostly complete by 2011. Soil cleanup involved moving, consolidating, and containing more than 350,000 cubic yards of dirt contaminated with lead and other heavy metals. This process decontaminated some 500 residences. Beginning in 1995, ASARCO- and county-sponsored education programs helped raise resident awareness of soil contamination and the risks of lead poisoning, though there were no documented cases of health effects among locals.
As cleanup efforts dragged on at the beginning of the twenty-first century, Leadville residents started to come up with ideas to help their community rebound from the psychological and economic toll of living amid a Superfund site. For example, the Mineral Belt Trail, a scenic bike trail that loops around Leadville, was dedicated in 2000 to improve the quality of life in the city and cover contaminated soil. In 2009, with more than $1.2 million from grants (including some from the EPA) and individual donations, the city of Leadville built a youth sports complex on the site of a former ASARCO zinc smelter.
By 2007 an estimated $150 million had been spent on cleanup efforts at the California Gulch Site, and in 2008 the state and federal agencies, including the EPA, reached a settlement with Newmont and ASARCO for another $138.5 million.
Although it angered residents and has taken decades, cleanup at the California Gulch Superfund Site has nonetheless helped renew interest in Leadville real estate and allowed outdoor recreation to become an important pillar of the local economy. The median sale price for houses in Lake County jumped from $163,000 in 2014 to $254,000 in 2017, and sales volume increased during that period as well. Today the average home price in Lake County is around $272,000. On the site of the old D&RG railroad yard, a new development is under construction that will include dozens of single-family houses and townhomes, as well as an apartment building and several commercial buildings.
Meanwhile, cleanup at the California Gulch site has also sparked renewed tourism to Leadville. By 2012, when site cleanup passed 90 percent, overnight travel spending in Lake County generated $30.5 million in revenue. The two water treatment plants have allowed for the recovery of trout populations in the Arkansas River, which draw hundreds of anglers each year, and annual outdoor events such as the Leadville Trail 100 Run and the Leadville MTB 100, a bike race, draw thousands of visitors. From 2013 to 2018, Lake County saw job growth in the retail, arts and recreation, and accommodation and food services industries, and the county population has increased from 7,261 in 2013 to more than 8,000 in 2021.
As of early 2021, the Union Milling company is attempting to secure permits to revive the Leadville Mill to process waste rock piles left outside many of the area’s mines. Although considered waste rock at the time they were taken out, these gravel piles contain trace amounts of precious metals that can be extracted using newer mining technology. After removing the waste rock, Union Milling would then remediate the sites with vegetation planting and erosion control measures. If approved, the activity would be the first precious metal extraction in the Leadville area since the declaration of the Superfund site.