English

Abstract

Butte’s Metro Storm Drain (MSD) is a channel that was constructed in the 1930’s to manage storm flows from Butte, Montana’s midtown area. It was in disrepair and contained large amounts of sediments, impacted by local industrial and urban activity. In addition, it collected base flow groundwater impacted with elevated levels of metals. These metal-impacted waters drained from the MSD to the local stream, Silver Bow Creek. To address these issues, a reclamation design was implemented in order to accomplish these major goals: 1. clean the channel of sediments to reduce sediment loads to Silver Bow Creek; 2. separate groundwater flows for routing to a treatment system and to reduce dissolved metals loads to Silver Bow Creek; and 3. provide a recreational corridor with enhancements to be more natural and aesthetically pleasing and functional for public use. Construction began in 2003. The channel was reconstructed with a subdrain beneath the surface channel. The sub-drain collects groundwater that previously entered the surface channel, and the collected groundwater is routed to a nearby treatment system. The reconstructed surface channel was first lined with a low-permeability liner to prevent storm flows from infiltrating into the sub-drain. Then, the surface channel was re-constructed using several features which allowed the channel to continue to drain storm flows, but also be more natural-looking. These features included a small meandering pilot channel incised into the base of the channel, which was constructed and revegetated for a natural appearance. Also, in several areas, the channel was widened with more gentle side slopes to reduce its original “engineered ditch” look. Finally, off-channel vegetation was planted, including large native trees and shrubs, and a walking trail was constructed along the channel’s entire length to make the corridor more useable as a recreational corridor. The construction was completed in 2004, and initial water quality monitoring results suggest there have been substantial reductions in metals loading to Silver Bow Creek from the MSD. Based on the successful construction completion and the water quality results, the major goals of the project have been achieved. Additional