While corrosion related damage to rail facilities and adjacent structures due to electric rail stray current has been documented, transportation agencies currently use conservative and often costly methods to protect highway structures against stray current. In addition, AASHTO requires special consultation be performed by a corrosion specialist and appropriate protection be provided for highway structures constructed near or beneath a Light Rail Transit (LRT) system. Most transportation agencies do not have engineering specialists on their staff who have the background to address stray current issues nor to deviate from these conservative standards, and there is little research available upon which to base updated guidelines. Instead, they rely on stray current mitigation measures provided by the electric rail operators. Operators of electric rail facilities often rely on mitigation measures that are based on older 1920¿s technology. These measures often focus on stray current mitigation and monitoring for infrastructure related to the rail facility and other buried underground utilities. Stray current monitoring and mitigation plans for nearby transportation structures typically do not exist. Some operators have implemented newer mitigation measures such as thyristor grounding systems, however, there is uncertainty regarding the effectiveness of these measures in preventing stray current corrosion of nearby transportation structures. Conservative methods such as Guidelines For LRT Stray Current Provisions (December 1988) outlined in California DOT (Caltrans) Bridge Design Details (BDD), Section 12-10.1, were included in the BDD because of the I-105 LRT corridor rail system. The provisions that were developed were an adaptation of the local BART heavy rail stray current design measures, and are often considered by electrified rail operators as too conservative for light rail transit systems. They were conservative for the newly emerging LRT systems and have become overly conservative in current projects. Local Agencies have become increasingly critical of these expensive, overly conservative design details. There is industry and international standard practice, and academic theory, but no defendable design standard. This project will provide it. The product of this research would be a design standard that mitigates the effects of stray currents in adjacent structures appropriate for LRT systems. This project could be included with a larger research project on the causes of structure corrosion.

To develop stray current design standards for protecting bridges and earth retaining structures subjected to stray current from LRT systems. The research conducted will provide a technical basis for modifying existing State guidelines (where they exist), and provide a basis for developing standardized AASHTO Bridge Design Specifications for stray current mitigation. This research would contribute to transportation agencies' goals of safety, reliability, flexibility and performance.

The project will likely include two phases: Phase 1 should include a literature review of state of the art practices for mitigation of stray current; Phase 2 should include strategies for monitoring stray current corrosion (if needed) in and around LRT systems by collecting field data to evaluate actual damage due to corrosion and testing the effectiveness of any new standard; Phase 3 should include drafting uniform and accepted design standards and monitoring strategies that effectively mitigate the effects of stray currents in adjacent structures. Principal Investigator; graduate student; and test equipment.

We anticipate a total contribution of $30,000 from each State or Partner spread over two years at $15,000 per partner.