2014/05/28 Council Agenda Packet

Explore justification for further public investment: • Consider acceptable target level -of -service (how many landslide -related interruptions are tolerable), recognizing that interruption -free service from landslides is likely not achievable or affordable. • Estimate order -of -magnitude, long-term improvement (capital) costs. • Evaluate projected cost of impacts against long-term improvement (i.e., capital) costs for a reasonable lifecycle to justify further public investment. • Distinguish public benefit from private benefit on privately owned infrastructure to ensure taxpayer dollars are used to benefit Washington State, its businesses and communities. The science and structural response of a fluid -like mass impacting a rigid structure, like the debris containment walls commonly used along the corridor, are not well understood, and current design methodology is poorly constrained. Similarly, the use of patterned -reinforced wire mesh to address shallow slope instability has not yet achieved widespread use in North America but is gaining widespread use in Europe. Research efforts should be undertaken to optimize design of debris containment structures and evaluate effectiveness of slope stabilization methods for shallow failures. Recommendations include: • Make design improvements to ensure reliability and optimize design of low -deflection, debris containment structures; • Evaluate test sections of reinforced mesh to determine suitability for more widespread application. If further public investment is deemed worthwhile, a landslide management system should be implemented and managed by a public agency that is closely coordinating with BNSF to proactively identify, prioritize, program and fund mitigation projects. p. 27