Solving Stray Current Mitigation In Portland’s Rail System

By Aaron Eder, P.E. | August 2014, Vol. 69, No. 8
Rendering of the Portland-Milwaukie light rail system. (photo courtesy of TriMet)

The city of Portland joined with TriMet to undertake the Portland Mall Revitalization Project. Portland Mall Light Rail was a key element in the planning effort connecting Clackamas County, one of the area's fastest-growing areas, with Portland State University (PSU), the primary destination in TriMet’s transit system. With a million new residents projected in the region, this extension of the region's light rail system was considered to be a key element in the long-range regional transportation plan. This extension positioned the region for future growth of high-capacity light rail to the southeast and southwest portions of the metro area.

In September 2009, construction of the 8.3-mile alignment was complete, bringing the region's total light rail system to over 52 miles and allowing light rail riders to make connections between Clackamas County and Gresham, PDX, Washington County, North Portland and downtown Portland.

The Portland-Milwaukie Light Rail Transit Project will create a light rail alignment that travels 7.3 miles, connecting Portland State University in downtown Portland, inner Southeast Portland, Milwaukie and north Clackamas County (see Figure 1). MAX service on the alignment is scheduled to begin in 2015. By 2030, this light rail line will carry up to an average of 22,765 to 25,500 weekday rides, and there will be approximately 22,000 households and 85,000 employees within walking distance of Portland-Milwaukie light rail stations.

Impacts to utilities

Light Rail Transit (LRT) system operations impose two unique impacts to utilities within the LRT corridor. The first and most obvious impact is that, unlike cars or buses, light rail trains cannot be detoured around obstructions in the road when, for instance, a water line breaks. Utilities which lie underneath the tracks must be either relocated or improved to minimize the possibility of breaks and mitigate the need to tear up the road and shut down LRT operations during routine or emergency utility maintenance.