2014/07/16 Council Agenda Packet

sum, the estimated economic cost from the closure of Interstate 5 in December 2007 is $47 million. In addition to Interstate 5, an additional 65 highways across the state were also closed due to flooding, landslides and downed trees. From highway damage alone, the storm is estimated to have cost $23 million for state highways and $39 million for city and county facilities. Interstate 90 was also closed due to this winter storm. As Interstate 5 is the primary north -south corridor for commerce on the West Coast, similarly Interstate 90 is the primary east -west corridor, with approximately 6,500 trucks traveling through Snoqualmie Pass each weekday. Due to record snowfall and warm temperatures, the threat of avalanche caused the pass to be closed for almost four days. Stevens and White Passes were also closed periodically throughout the months of January and February 2008. While alternate routes, albeit of much longer distance, were available for Interstate 5 traffic, the options for east -west travel were limited due to the severe weather and the closing of additional routes. At times, all east -west traffic was at a standstill. The estimated economic cost from the closure of Interstate 90 in early 2008 is $28 million. King County has also studied the economic impacts of flooding. The October 2007 report, "Economic Connections Between the King County Floodplains and the Greater King County Economy" indicates that approximately 2% of the county's population and 6% of the county's employment is located in the floodplain region, including 30% of the county's aerospace employment. The report estimates that a one -day shutdown in the area would cost approximately $46 million in lost economic output. Longer -term impacts, including potential movement of employers out of the area because of flooding issues, would have significant economic implications. The impacts from closure of critical transportation routes extend beyond the costs to the trucking industry, employment centers and from highway damage. Examples of other important sectors that are impacted from these events include emergency services and the agricultural community. The ability to obtain medical care and prescriptions, the ability of grocery stores to receive food and preserve perishable items, the ability to safely transport livestock, and the increased costs of delays are all examples of further effects from a region severely impacted by storms and flooding. The region and the state are proactively addressing the needs identified from events such as those in the winter of 2007-200812; however, the potential increase in these events from a changing climate will require additional proactive planning and coordination. SECTION 5: CURRENT PLANNING EFFORTS Emergency planning efforts are currently underway for a variety of reasons unrelated to the potential impacts from climate change. However, these efforts and interagency coordination will be critical in preparing the region for future emergency scenarios. For example, the recent efforts to prepare, plan and mitigate for a failure at the Howard Hanson Dam are a good example of the benefits of coordinated emergency preparedness planning that may be called upon for future emergency scenarios due to a changing climate. A summary of these efforts and background on the issues facing the Howard Hanson Dam are discussed below, along with other efforts in the region related to planning for adaptation to climate change. Howard Hanson Dam: Background The Howard Hanson Dam flood threat is a case study of known potential flooding in a highly urbanized, industrial area. This example can be drawn on to illustrate the potential impacts due to flooding and the necessary coordination and planning efforts that may need to be undertaken in the industrial areas vulnerable to sea level rise. Completed in 1961, the Army Corps of Engineers constructed the Howard Hanson Dam as a flood control mechanism for the Green River Valley. Since then, major development has swept through the valley, transforming it into a key industrial center with residential development as well. In early 2009, the Corps found major structural issues with the dam. If the reservoir fills up due to a storm or multiple successive storms, the Corps may be forced to flood the valley to prevent complete dam failure and catastrophic flooding. Initially, the Corps was predicting a 1-in-3 chance of a major flood; the threat has since been lowered to a 1-in-25 chance due to the several million dollars invested in reinforcing the dam. Over the next 3-5 years, long-term repairs will be required for a permanent fix and will cost hundreds of millions of dollars (Bissonnette 2009). In the event that the Corps does need to flood the Green River Valley before a permanent fix has been made, businesses and residents in the 12 For example, the 1-90 Snoqualmie Pass East project is designed to mitigate delays due to avalanches and rock slides L-19 Appendix L: Climate Change Background