Multi-Hazard Mitigation Plan: 19. Mitigation Strategy

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Chapter 19:Mitigation Strategy buildings will be lost when a hurricane moves through parts of the island. It has been esti- mated that 38% of homes will be heavily damaged and an equal number will suffer minor damage from an Iniki-strength hurricane striking any island.109 State Civil Defense has published a guide on strengthening houses to minimize losses."0 Adopting and enforcing a building code with adequate wind load requirements is the primary mitigation tool for structures. The code requirements for wind pressure have increased by a factor of 2:1 since 1958 as the Uniform Building Code changed. The current level is based on a 95 mph peak gust, is applicable to commercial structures only and was adopted by the County in 1993. Prior to 1993, the County had no specific code requirements related to wind forces for residences. The code implemented in 1993 (the 1991 UBC) requires roof-to-wall uplift ties. The most important action the County can take other than code revision is to ensure that public buildings, shelters, and other vital facilities meet the code requirements. The FEMA 1993 report is an excellent manual on structural lessons from Iniki while the ARA 2001 report covers implementation of these factors in detail."' The 2006 IBC significantly improves the wind design requirements of the 1991 UBC, therefore its adoption in the county of Hawaii is of the utmost importance. • Infrastructure lifelines. Harden exposed communication and electrical systems. Consider underground installation for new development and in strategic existing areas. 19.2.2 Earthquakes Hawaii County is believed to be exposed to the highest seismic hazard in the State. In approximately the past 50 years, the County has experienced at least eight earthquakes with a Richter Magnitude of 6.0 or greater, and the geological structure of the island is believed to be capable of generating even larger earthquakes. Moreover,because the vast majority of structures in the County were designed and constructed before adoption of the 1976 Uniform Building Code (UBC), which is the earliest UBC edition whose seismic design requirements are similar to the 1991 UBC, many of these structures most likely do not conform to the minimum seismic design requirements adopted by other high seismic risk regions of the United States. Mitigation actions include preventive measures and emergency services improvements: • Identification of Vulnerable Structures and Areas. Refine the applicability of the HAZUS model to Hawaii Island to assess earthquake risks and identify appropriate mitigation actions. The findings of a recent study prepared for the Hawaii State Earthquake Advisory Committee 109 Schroeder,Tom, 1993,"Hawai'i Hurricanes:Their History,Causes,and Future,"Office of State Planning, December 1993. 110 Hawai'i State Civil Defense, 1997,"Construction Guide:On Strengthening Houses Against Hurricanes and Earthquakes,May 1997. 111 Federal Emergency Management Agency(FEMA), 1993,`Building Performance:Hurricane Iniki in Ha- wai'i",January 1993,Federal Insurance Agency,Washington,D.C.;Applied Research Associates(ARA),2001, "Hazard Mitigation Study for the Hawaii Hurricane Relief Fund"(incorporates part of FEMA-sponsored Iniki Building Performance Report),December 2001. 19-4 Hawaii County Multi-Hazard Mitigation Plan