Visible Progress on Cleanup of the Former Asarco Smelter – Prickly Pear Creek Bypass Channel

The Montana Environmental Trust Group (METG), Trustee of the Montana Environmental Custodial Trust, is moving forward with cleanup of the former Asarco smelter.  METG’s progress is visible on the west side of Highway 518 in East Helena where construction workers can be seen operating excavators, cranes, trucks and other heavy equipment.  Work underway on the so-called “East Bench” – the area between Prickly Pear Creek (PPC) and Highway 518 south of Highway 12 – is one part of a series of inter-related, EPA-approved cleanup plans (called Interim Measures or IMs).  These IMs are designed to reduce the offsite migration of contaminants in groundwater resulting from more than a century of smelting activities at the former Asarco facility.

Contaminated soils in direct contact with groundwater beneath the smelter site contribute to the contaminant plumes migrating off-site.  Because it is not technically or financially possible to remove all the waste that is contaminating groundwater, the cleanup plans focus on “getting the waste out of the water.”  Surface water from PPC and the manmade Upper and Lower Lakes raises groundwater levels in the south plant area, which increases the loading of contaminants to groundwater and pushes plumes of contamination offsite.  The cleanup plan is designed to reduce surface water recharge from Upper Lake, Lower Lake and PPC to groundwater at the south end of the site and is referred to as the “South Plant Hydraulic Control (SPHC) Interim Measure (or SPHC IM).”  To lower groundwater levels and reduce this recharge from the south plant area, SPHC IM entails draining the water from the lakes and realigning PPC to the east away from the south plant area.

East Bench construction activities are paving the way for realignment of PPC, which is the centerpiece of the SPHC IM.  Beginning in May, utilities were moved from the area where the realigned PPC will be constructed.  Working with NorthWestern Energy and CenturyLink, existing power distribution lines and telecommunications cables were moved to a utility corridor along Highway 518.  Partnering with the City of East Helena, METG also installed a new City waterline to replace the existing East Bench waterline.  At the City’s request, METG upgraded the waterline to allow the City to improve and expand its water service.

METG began construction of the PPC Temporary Bypass Channel in early July.  The purpose of this channel is to temporarily divert PPC flows away from the south plant area to drain water from Upper and Lower Lakes.  The PPC Temporary Bypass Channel consists of a low flow channel and a larger floodplain channel.  Material excavated from the PPC Temporary Bypass Channel will eventually be used as part of a capping system to be installed on the former smelter property.  After Upper and Lower Lakes are dry, the Upper Lake berm and diversion structure will be removed.  With the Temporary Bypass Channel in operation, the realigned PPC can be constructed, PPC flows can be directed into the realigned PPC and Smelter Dam can be removed.  (Smelter Dam and other PPC structures, which have not been maintained, could fail and potentially cause downstream flooding.)  The PPC Temporary Bypass Channel may be retained as an overflow channel while the realigned PPC stabilizes in the new creek bed after which the channel can be reclaimed and integrated into the PPC realignment.  The PPC Temporary Bypass Channel is slated to be operational this fall.  Remaining work on the creek will be implemented in the next two to three years.

Implementation of SPHC IM, including PPC realignment, will significantly reduce the loading of contaminants to groundwater.  Realignment of PPC will also create numerous other benefits, including: reduced erosion of slag into PPC; increased flood storage; enhanced creek habitat; and elimination of the major impediment to fish passage on PPC by removal of Smelter Dam.  Construction of the PPC Temporary Bypass Channel represents a critical first step in the realizing these important environmental and community events.

For more information please contact Cindy Brooks, Director of Remediation and Redevelopment for the Montana Environmental Custodial Trust, by email at or by telephone at 617-448-9762.