Butte, Montana

After AOC-mandated nutrient effluent upgrades at the WWTP were halted due to Pentachlorophenol (PCP) in the dewatering effluent, WET was contacted by BSB to provide technical expertise to facilitate the resumption of construction activities.  Because the site is within BPSOU, the dewatering effluent was being released to the Butte Treatment Lagoons (BTL), which treats metals-contaminated water from area sites.  However, the BTL was not designed to treat PCP contaminated water.  After confirmation that the effluent water had metals and PCP contamination, mitigation strategies were developed by WET personnel to facilitate the needed upgrades at the plant and protect water quality in Silver Bow Creek. Potential mitigation strategies were modeled, and a preferred strategy selected in consultation with EPA, DEQ and Atlantic Richfield.

A demonstration pilot test of the preferred mitigation alternative was developed and implemented to test the mitigation strategy under the numerous stresses present in the aquifer below the WWTP.  The pilot test was successful and construction upgrades are again moving forward.  This project included coordination between multiple local, state, and federal government entities, multiple meetings, review of a 3-D ground water flow model of the site, additional flow modeling of mitigation strategies and field work including a subsurface Geoprobe investigation, groundwater and surface water sampling, and water level monitoring from a pre-test to post-test timeframe.