{"id":3519,"featured":0,"modified":"2026-04-17 19:58:10","latitude":46.01169927189128117106520221568644046783447265625,"longitude":-112.517801284921006299555301666259765625,"title":"Groundwater Contamination","subtitle":"","fullsize":"https://storyofbutte.org/files/fullsize/4bb60e6d01b97fb6c82e9383d488936f.jpg","address":"","all_locations":[],"zoom":16,"creator":["Jon Sesso"],"description":"The seminal contributor to groundwater contamination is the Berkeley Pit, a problem created in 1982 when ARCO ceased mining activities and turned off the pumps at the 3,900-foot level below the surface in the Kelly Mine. Thousands of miles of underground mine workings and the Berkeley Pit flooded as the groundwater started rising to its natural level. In the Pit, that water, when exposed to heavy metals on the Pit walls and air (oxygen), became a toxic soup that requires perpetual monitoring and management. <br />\r\n<br />\r\nGiven the adverse impacts of this contamination, the groundwater in large portions of Butte’s urban area can’t be used for drinking. The extent of the damage, in volumetric and economic terms, is enormous. For just the bedrock aquifer on the Butte Hill, lost ground water resources are estimated at 6,900 gallons per minute (gpm). By comparison, 5,000 gpm equates to seven million gallons per day, which is about the average amount of water used by Butte citizens on a typical day. In economic terms, approximately 3,000 residential properties and 350 commercial parcels are situated over the contaminated aquifers on the Hill. If these aquifers were not contaminated, the residents and businesses could have used a substantial portion of the groundwater resources as a source of drinking water through private wells. <br />\r\n<br />\r\nBy 1994, the EPA determined that it was “technically impractical” to remediate this contamination. They stipulated that, to protect human health, a ground water control area and other restrictions needed to be put in place to limit the use of existing wells and prohibit new wells in specific areas. EPA also approved the proposed plan from ARCO and Montana Resources (the active mine operator in 1994 and still today) to allow the groundwater to enter the Berkeley Pit until the level reached 5,350 feet above sea level. This is about 60 feet below a “Critical Water Level” where contamination could potentially begin to adversely affect alluvial groundwater resources. Once the water level in any of the underground mines surrounding the Pit reached 5,350, which occurred in 2018, pump and treat operations began. Today, approximately seven million gallons per day are pumped out of or diverted away from the Berkeley Pit, processed through two treatment plants, and used in active mining operations or discharged into Silver Bow Creek.","sponsor":"Superfund Advisory and Redevelopment Trust Authority and The Foundation for Montana History","accessinfo":"","lede":"Mining in Butte severely impacted water resources – groundwater, stormwater, surface water, drinking water, and even sanitary sewer water – all contaminated by the heavy metals brought to the surface from the Richest Hill on Earth.","website":"","related_resources":["<a href=\"https://storyofbutte.org/admin/tours/show/108\">Mining Technologies</a>"],"factoids":[],"files":{"https://storyofbutte.org/files/fullsize/4bb60e6d01b97fb6c82e9383d488936f.jpg":{"id":5750,"mime-type":"image/jpeg","title":"Butte Before the Pit","description":"Aerial imagery showing Butte prior to the digging of the Berkeley Pit open-pit mine.  | Courtesy of Montana Resources","thumbnail":"https://storyofbutte.org/files/square_thumbnails/4bb60e6d01b97fb6c82e9383d488936f.jpg"},"https://storyofbutte.org/files/fullsize/5987ea3f3bd27cc8ba933441db0ef695.jpg":{"id":5751,"mime-type":"image/jpeg","title":"Butte After the Pit","description":"Aerial imagery showing Butte after digging of the Berkeley Pit open-pit mine.  | Courtesy of Montana Resources. ","thumbnail":"https://storyofbutte.org/files/square_thumbnails/5987ea3f3bd27cc8ba933441db0ef695.jpg"},"https://storyofbutte.org/files/fullsize/37497bf3b51f602ac46e6551cb7876c4.jpg":{"id":5752,"mime-type":"image/jpeg","title":"Berkeley Pit, Early Days","description":"Berkeley Pit with surrounding communities, including McQueen and East Butte. 1963.  | Butte-Silver Bow Public Archives, Smithers.11.231.03","thumbnail":"https://storyofbutte.org/files/square_thumbnails/37497bf3b51f602ac46e6551cb7876c4.jpg"},"https://storyofbutte.org/files/fullsize/080f33db7a64860a1cf3c3d088bb055a.jpg":{"id":5753,"mime-type":"image/jpeg","title":"Berkeley Pit, Later Days","description":"View of Berkeley Pit looking to the northwest, 2015, after having subsumed surrounding neighborhoods. | Geoff Weston photograph, Butte-Silver Bow Public Archives","thumbnail":"https://storyofbutte.org/files/square_thumbnails/080f33db7a64860a1cf3c3d088bb055a.jpg"},"https://storyofbutte.org/files/fullsize/47b159ab1120477df6270b34a94b6472.jpg":{"id":5754,"mime-type":"image/jpeg","title":"Drinking Water","description":"Almost $100 million in settlement funds have been invested in Butte’s drinking water infrastructure: replacing miles of distribution pipelines in town and miles of a water transmission pipeline from the Divide diversion dam; removing the old dam and installing a new one, along with a new pump house at Divide; building a new treatment facility for the Basin Creek supply; and other projects. All made possible with funds from the ARCO’s NRD settlement with the State of Montana.  | Walter Hinick, Montana Standard photo.","thumbnail":"https://storyofbutte.org/files/square_thumbnails/47b159ab1120477df6270b34a94b6472.jpg"}}}