Multi-Hazard Mitigation Plan: 05. Tropical Cyclones

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Chapter•5:Hazard Analysis—Tropical Cyclones Glazing in buildings located in wind-borne debris regions shall be protected with an impact resistant covering or be impact-resistant glazing according to the requirements specified in ASTM E1886 and ASTM E1996 or other approved test methods and performance criteria. The levels of impact resistance shall be a function of Missile Levels and Wind Zones specified in ASTM E1886 and ASTM E1996. EXCEPTIONS: 1. Glazing in Category Il, III, or IV buildings located over 60 ft (18.3 m) above the ground and over 30 ft (92 m) above aggregate surface roofs located within 1,500 ft (458 m) of the building shall be permitted to be unprotected. 2. Glazing in Category I buildings shall be permitted to be unprotected. The Hawaii State Building code allows for the construction of a safe room in residential construction in lieu of the windborne debris protection requirements. This essentially reinstates the previous versions of the ASCE 7 where unprotected glazing is allowed in a windborne debris region although, it must be considered as an opening when determining the enclosure classification. 5.5.1.2 Utilities Damaged or destroyed utility lines and facilities — including electricity, computer and satellite links, gas sewer, and water services — can cripple a region after a disaster. Power lines are often badly damaged or destroyed resulting in the loss of power for days, weeks or even months as in the case of Hurricane Iniki. In addition to basic modern household appliances being affected, public water supplies, water treatment and sewage facilities can also be impacted. Electric pumps cannot pump drinking water into an area without power. Disaster victims who do get water may have to boil it to eliminate waterborne pathogens introduced to the supply in breached areas. Electrical transmission and distribution lines have been particularly susceptible to failure in previous hurricanes, with 30% of the wooden power distribution poles and 26% of transmission poles on Kauai failing during Hurricane Iniki. This has resulted in periodic updates to the design criteria for these poles. The most recent design criteria were adopted by the State Public Utility Commission as Hawaii Administrative Rules 6-13, and are based on the 2002 National Electrical Safety Code which references the ASCE 7 wind load criteria. While this would an improvement to the local design standards it does not incorporate the latest Hawaii specific wind design criteria. It is recommended that the future mitigation project should further update the transmission and distribution line design criteria to incorporate the Hawaii specific wind design criteria and utilize the effective wind speed maps that account for topographical, directionality and local exposure. Procedures should be implemented to assure the adoption of the new standards so that when a power pole fails and is replaced, the replacement should meet the current standards. 5-15 Hawaii County Multi-Hazard Mitigation Plan