▲ Prickly Pear Creek Realignment East Helena, Montana Pioneer Technical Services Helena, Montana Resourceful engineering eradicated a toxic threat to groundwater by realigning a natural stream away from the contamination danger. For more than a century, ore processing at a nearby smelter had sent tons of slag and waste products into the Prickly Pear Creek floodplain, causing widespread contamination and major threats to the groundwater. To restore the area's environmental health, the project team removed a nearby dam and lake complex replacing it with a "natural" stream channel that diverts the creek away from a contaminated slag pile. Groundwater levels below the most contaminated soils were permanently lowered, which reduced the extent and magnitude of the groundwater plumes, restored fish passage through the site and reestablished more than 140 acres of wetlands. MAY / JUNE 2019 ENGINEERING INC. 23