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HomeMy WebLinkAboutMulti-Hazard Mitigation Plan: Executive Summary Executive Summafv EXECUTIVE SUMMARY The Island and County of Hawaii has experienced 42 natural disaster events since 1977 and five tsunamis (1946, 1952, 1957, 1960, and 1964) since 1940. This island is uniquely exposed to all the major natural hazards due to its active volcanoes (lava flow and earthquake hazards), young geological age (sheetflow flooding due to undefined drainage-ways), vast land area larger than all the other islands combined(expansive areas vulnerable to wildfires), varied topography dominated by five mountains (complex hurricane wind acceleration patterns), and easternmost location in the Hawaiian islands chain (hurricane exposure). Of lesser concern is sandy beach erosion due to the geologically youthful age of this island resulting in few sandy beaches; instead, sea cliff erosion is of greater concern to control building too closely to the cliff edge. The purpose of this multi-hazard mitigation plan is to provide a strategy to reduce or eliminate loss of life or property caused by natural hazard events. A multi-hazard strategy addresses the relationship among various types of hazards, leverages resources to benefit multiple hazards, and allocates limited resources to areas susceptible to the most severe or frequent hazards. Risk and Vulnerability Assessment Hazard Anal The state of knowledge and hazard mapping are summarized below: • High Wind Storms. For high wind risks, the areas exposed to wind acceleration due to topography have been mapped. • Hurricanes. Similar to high winds, the areas exposed to wind acceleration due to to- pography have been mapped. For storm surge risks, the Flood Insurance Rate Maps (VE zone)will be updated based on hurricane surge modeling. • Landslides and Rock Falls. GTS mapping has been developed to identify areas susceptible to landslide or rock falls based upon the slope of the terrain, soil type, and ground moisture level. • Earthquake. The County should adopt the 2006 International Building Code as the official building code; this better classifies the probabilistic acceleration parameters of the Island than previous versions of the obsolete 1991 Uniform Building Code currently enforced by the County. Maps have also been developed to distinguish areas where ground motion could be significantly increased by softer soil conditions. • Lava Flows and Volcano Gases (VOG). Although mapping exists that zones the entire island into nine lava hazard zones, the Hawaii Volcano Observatory is presently working to replace this map with a probabilistic hazard map. UH Manoa Center for the Study of Active Volcanoes (CSAV) is developing a modeling system to predict direction and speed of flow for a given eruption. ix Hawaii Countv Multi-Hazard Mitigation Plan Executive Summafv • Tsunami. New mapping is being developed for tsunami inundation areas (delineation of historical and modeled run-up used to control development) and tsunami evacuation areas (more conservative delineation than inundation areas based on identifiable landmarks such as roads and used to facilitate field evacuation logistics). Historically in Hawaii Flood Insurance Rate Maps (FIRM) also accounted for the tsunami inundation risk areas and limits of historical inundations (VE zone). • Flooding. FEMA and the County are working on making the FIRMS available in digitized format, which will improve the GTS. The County is also working on improving the accuracy of the FTRMs based on updated topographic information. Additionally, the GIS includes revisions to the FIRM (called Letter of Map Revisions or LOMRs). Improvements are needed to the rainfall and stream-flow gauging system to improve forecasting and real-time monitoring. In December 2008 and February 2009, FEMA submitted to the the County Preliminary Digital Flood Insurance Rate Maps (Pre-DFTRMs). The County is currently doing flood studies (map updates) in the following areas: Puna, Hilo, North and South Kona. There are several privately funded flood studies ongoing in the Kona, Hilo and Waimea. As part of FEMA's mapping process, the County is also pursuing, with the help of the U.S. Army Corps of Engineers, levee certifications for Alenaio, Paauau and Wailoa Flood Damage Reduction Control Projects. All of these studies will be completed within the next year to year and one half. • Dam Failures.Dam break studies have been conducted to map areas were flooding may result due to dam failure. • High Surf. The entire coastline of Hawaii Island is susceptible to the effects of high surf, areas were the potential for coastal flooding exists are defined as the VE zones on the current FIRM maps as described in the Hurricane and Flood chapters. • Coastal Erosion.No studies or GIS data exist to establish safe setback limits to address sea cliff erosion risks. Beach erosion in Hawaii County is not a significant enough problem to presently warrant detailed mapping. • Droughts and Wildfire. As part of the Hawaii Drought Plan areas where the water supply sector, agriculture and commerce, and/or environment, public health, and safety are vulnerable to the effects of drought were mapped in GTS. This mapping also identifies areas where historic wildfires have occurred and where this risk is present. • HAZMAT. The Department of Health Hawaii State Response Program List of Priority Sites identifies all Hawaii sites for potential or known non-emergency response actions managed by the HEER Office Site Discovery, Assessment, and Remediation Section Remedial Project Managers (RPMs). Sites are categorized as a potential hazard when sampling data indicate that contaminant concentrations exceed Hawaii Environmental Action Levels. The DOH Hawaii SRP Priority List of Sites shows 83 sites on the Big Island with potential or known hazardous substance or petroleum contamination. Three sites were determined to require No Further Action (NFA). HEER Office Remedial Project Managers (RPMs) continue active oversight on 70 assessment and response actions. X Hawaii Countv Multi-Hazard Mitigation Plan Executive Summafv Risk Assessment Risk can be defined as exposure to the chance of loss or injury. Critical Facilities and Special Populations/Areas This plan focused on mitigating hazards to critical facilities and special populations or areas. Critical facilities include those public and private facilities that need to be operational during and after a hazard event to meet public health and safety needs, or to speed economic recov- ery. These facilities include: • Emergency response facilities-- Civil Defense Emergency Operations Center, emergency shelters, fire and ambulance stations, hospitals, police stations, Department of Public Works base yards; • Infrastructure lifeline facilities-- transportation (harbors, airports, roads/bridges), energy (electrical, fuel, gas), communication (wired/cabled telecommunication, wireless), water, wastewater; • Recovery facilities-- debris clearing and disposal, car rentals,buses, financial institutions, survival and building supplies; • Secondary hazard facilities-- facilities that increase the hazard risk if damaged, including wastewater facilities and hazardous waste sites. A study of the critical facilities on the Big Island has been preformed to evaluate and rank the vulnerability of each building to the above hazards. Loss estimations have been developed and a benefit cost analysis of potential retrofits will be performed on facilities of highest priority. This study will be detailed in Chapter 16; this loss estimation information is used as one of several criteria to prioritize the allocation of limited resources to mitigate hazards. Estimates of historical and potential future losses for each of the above hazards can be further refined in future updates of the plan to rank the severity of the risk imposed by each hazard. Special populations identified with demographic data are those that are more vulnerable and may require special assistance to prepare, evacuate, or recover include: • Young and elderly; • Non-English speakers; • Persons with disabilities. Special areas that are more vulnerable and may require special assistance to prepare, evacuate, or recover include: • Schools, day care centers, and nursing homes; • Residences and buildings built before 1985 under building code additions prior to the adoption of the 1982 UBC and therefore more susceptible to hurricane and earthquake damage; • Residences and buildings in high hazard areas; • Remote residences that are distant from sirens or off-grid; • Hotels and resorts, due to their economic importance; Xi Hawaii County Multi-Hazard Mitigation Plan Executive Summafv The GIS system superimposed the hazard layers over the critical facilities and special populations/areas to identify those located in high hazard areas. Vulnerable critical facilities were assessed to determine whether the facility should be hardened. Vulnerable special populations and areas require a range of mitigation measures discussed in the plan. The following table summarizes the vulnerable critical facilities, special populations, and special areas based on the best available data. xii Hawaii Countv Multi-Hazard Mitigation Plan Executive Summary Summary of Vulnerable Critical Facilities,Special Po mulations,and Special Areas by District Puna South Hilo North Hamakua North South Kohala North Kona South Kona Ka'u Hilo Kohala Emergency shelters--major shelters--major commu- communication communleatlon shelters--major shelters--major communication Ka'u Hospital and operations facilities capacity capacity deficiency; ecation system hardening system harden- capacity deficiency; cefoelty defi- system hardening Naalehu EMS ranked deficiency;Pahoa communication system and/or redundancy; ing and/or Kohala High& ciency;commu- and/or redun- high in a critical Fire Station In lava system hardening hardening Hale H.W. redundancy; Elementary School nication system carry;Building 1 facilities vulnerability flow hazard zone and/or redundancy; and/or Hamakua and Kohala and Waimea State hardening arid/ and 2 and the study 2;communication The Acute Care redundancy; Hamakua Health Hospital and office building require or redundancy; Psychiatric Facility system hardening Facility and the Laupahoeho Center ranked high in North Kohala hardening;cam- Kona Police at Kona and/or redun- Extended Care e Police critical facilities Police Station munication system Station and Community carry; Facility at Hilo Station and vulnerability study ranked high in hardening and/or Keauhou-Kona Hospital ranked Keaau Fire and Medical Center Laupahoeho a critical redundancy;North Fire Station high In a critical Police Station and ranked high in a e fire Station facilities Hawaii Community ranked high in a facilities Pahoa Fire Station critical facilities ranked high vulnerability Hospital and Waimea critical facilities vulnerability study ranked high In a vulnerability study in a critical study Fire Station ranked vulnerability critical facilities facilities high In a critical study vulnerability study vulnerability facilities vulnerability study study Infrastructure Hilo Harbor--no Kawaih rdening plans for due to damage no hae Harbor— Kona Airport-- lifeline facilities haardening tsunami or during the Kiholo Bay hurricane surge; Earthquake several Hilo Airport--no mitigation measures hardening;Eleo- have been trical generating recommended:high station(Walakea)in strength piling and VE flood zone:elec- anchorage retrofits, trical transmission ground and subg.de lines along Saddle improvement, Road in lava flaw performance hazard zone 2 monitoring Special populations High%of young- high%of elderly; high%of high%of elderly Hlgh%of high%of high non-English High%of sters;high%of high disahled;high elderly youngsters;high elderly;high dis- speakers youngsters;high elderly;high n-English n-English added; high of elderly;high dis- disabled;high% speakers speakers non-English added;high%public public assistance; speakers assistance high non-English speakers xiii Hai raii County Multi-Hazard Mitigation Plan Executive Summafv Mitigation Strategy Mitigation goals and objectives to eliminate or reduce risk include: 1. Goal: Continually strive to improve the state of the art for the identification of hazard areas,prediction capabilities, and warning systems. Objectives: 1.1. Prepare GIS maps for all hazards with the best available information and formulate a strategy to maintain/upgrade the data. 1.2. Improve applicability of modeling systems to Hawaii Island conditions for hazard mapping,mitigation planning, and scenario training purposes. 1.3. Improve flood prediction and field-monitoring systems. 1.4. Establish a warning system that is cognizant of warning siren gaps that require supplemental field warning, which strives to fill those gaps based on population, that is routinely tested and maintained, and that educates the public on proper response. 1.5. Establish a rigorous reporting system after each major event to document the extent and cause of damage, lessons learned, and actions required to improve hazard mitigation,preparedness,response, or recovery. 2. Goal: Control future development and retrofit existing structures within hazard areas to minimize losses. 2.1. Update the building code to cost-effectively resist earthquake, hurricane, and flood susceptibility. 2.2. Periodically review the effectiveness of current land-use-related plans, codes, and standards to control future development within hazard areas. 2.3. Develop incentives, such as tax deductions and insurance discounts, to encourage retrofitting of existing structures to resist earthquake, hurricane, and flood susceptibility. 3. Goal: Ensure that all emergency response critical facilities and communication systems remain operational during hazard events. 3.1. Harden all essential emergency facilities and communication systems to withstand earthquake and hurricane forces (Ensure road access to hospitals remains clear and that all hospitals have helicopter access, no emergency facilities should be located in the 100-year flood-prone areas). 4. Goal: Ensure that all lifeline infrastructures are able to withstand hazard events or have contingency plans to quickly recover after a disaster. 4.1. Harden ports and airports to enable post-disaster operations. 4.2. Harden major highway segments that have no alternate bypass to withstand earthquake and 100-year floods as well as rockfalls/landslide closure. 4.3. Harden fuel storage facilities and ensure distribution network to critical facilities. 4.4. Reduce vulnerability of electrical system to all hazards. 4.5. Develop water systems that resist damage to all hazards and contingency plans to truck water. xiv Hawaii County Multi-Hazard Mitigation Plan Executive Summafv 5. Goal: Provide adequate pre- and post-disaster emergency shelters to accommodate residents and visitors. 5.1. Identify and harden selected shelters to withstand hurricane. 5.2. Establish a standardized due diligence procedure for qualifying a building for private self-sheltering. 6. Goal: Develop a level of awareness among the general public and businesses, particularly the visitor industry, that results in calm and efficient evacuations, self- sufficient survival skills, and willingness to abide by preventive or property protection requirements. 6.1. Develop a broad-based public information program that utilizes a diversity of communication media. 6.2. Develop special public information programs targeted to vulnerable populations. 6.3. Develop a community-based network that double-functions as the Community Emergency Response Team and provides input into mitigation planning. 7. Goal: Minimize post-disaster recovery disruption by developing systems for efficient clean-up, documentation of damage and injury, and processing of appropriate aid to rebuild businesses and the economy. 7.1. Educate businesses on business interruption planning. S. Goal: Protect natural and cultural resources to the extent practicable that buffer hazards or have significant value. The followin6 are the County priorities rel!ardinl!hazard mitigation projects: 1. Hardening and Retrofitting of Critical Facilities Conduct all hazard evaluations and develop cost-effective retrofits for priority facilities including: • hurricane shelters and schools, • hospitals, fire stations, and police stations, airports • Hilo and Kawaihae harbors and fuel storage facilities • key County bridges and plan alternative transportation routes, • power plants, water systems, communications sites, sewage treatment plants, and other facilities/buildings providing critical services 2. Upgrading of County Building Codes in accordance with Hawaii Revised Statues Chapter 107, State Building Code and Design Standards 3. Mapping/Assessments/Studies Analysis of high hazard areas and studies to develop mitigation measures: • perform screening evaluations of alternative facilities to augment public shelters to address shelter shortfall • investigate and document effectiveness of VOG mitigation techniques and incorporate in public awareness meetings xv Hawaii County Multi-Hazard Mitigation Plan Executive Summav • update the HAZUS MH model to incorporate current bridge status and adapt HAZUS MH with enhanced building information data for hurricane loss estimation and identification of vulnerable structures Develop mapping of all major natural hazards: • flood map modernization with incorporation of both hurricane flood and tsunami inundation into DFIRM's • updated tsunami evacuation maps • earthquake ground failure hazard maps • probabilistic lava inundation maps • probabilistic tsunami inundation maps • dam inundation evacuation maps • landslide and slope stability hazard maps • LIDAR-based remapping of streams 4. Wildfire Prevention(firebreak establishment and fire mitigation resource inventory) 5. Drought Mitigation by improvements to irrigation aqueduct, reservoirs, and water management 6. Policy for Repetitive Flood Loss Properties 7. Develop natural hazard mitigation criteria policies for county facility site selection and design S. Public Awareness/Education, with additional focus on implementation of Multi-Hazard Mitigation Techniques and VOG • Incentives for Homeowners and Business to retrofit vulnerable structures: To further support this type of outreach,the following actions are still needed: • an expedited permit process if the homeowner uses the standard recommended plans; • working with insurance companies to get homeowners insurance credits for implementing these retrofits; • need to expand the Expert System to add the hurricane mitigation techniques that were previously developed for the Hawaii Hurricane Relief Fund's Loss Mitigation Grant Program. • Retrofit training,videos, displays, and demonstration/pilot retrofit projects • Multi-hazard public information website consolidating GIS mapping products for hazards &zoning 9. Mitigation of Erosion/Land/Rock Slides in residential areas and highways. (Highways have greater priority) xvi Hawaii County Multi-Hazard Mitigation Plan Executive Summafv Changes to Risk Exposure Due to Successful Mitigation Projects • Critical Facility Study. An all-hazard screening of critical facility buildings in the County of Hawaii has been conducted and a HAZUS MH risk assessment model created to evaluate the expected losses for each building. Two facility groups, that ranked high based on these analyses were evaluated in more detail such that recommended mitigation procedures were developed. A Benefit-Cost Analysis of the mitigation project construction funding was performed. This detailed evaluation provided the information necessary to submit a PDM grant applications for the retrofit project, and prioritize the most vulnerable critical facility buildings for future retrofits. • Shelter Studies Evaluations of 29 buildings throughout the Hawaiian Islands were conducted in accordance with the requirements of the Department of Accounting and General Services (DAGS), Division of Public Works, Scope of Services and Procedure for Structural Assessment of Buildings for Hurricane Shelter Classification. The primary objective of these evaluations were to identify whether the structures substantially meets the wind load criteria for a Shelter rating of Type B or better. The evaluations also identify recommendations for any further incremental structural or nonstructural retrofits to achieve substantial compliance with Shelter Types B, A, and EHPA, where economically feasible. Four facilities on the Big Island were evaluated according to this procedure; the results of these studies are presented in Chapter 16. • Wind Map Improvements The building code now used in the County of Hawaii does not include any design requirements for amplified winds caused by topography. The International Building Code (IBC) 2006 Edition that will replace the code now used in the County introduces a new topographic factor and a wind directionality factor that in their default formulations would not give accurate results in Hawaii. This would lead to a high probability of incorrect design unless the State Building code amendments are adopted. The state of Hawaii amendments include several customized map products prepared for the building code in Hawaii County. Significant improvements in wind hazard mitigation can be accomplished through the use of wind speed-up mapping in local building codes and risk assessments. New wind maps incorporating this effect define a standard for a uniform level of protection for hurricane hazard throughout the County. Benefits include explicit quantification of wind-hazard and its mitigation through the identification of the severity of wind environments for planners and building designers that will significantly improve building performance. Determination of the wind hazard in topographically affected critical facility sites is essential for pre-disaster planning and emergency operations planning. Criteria for critical facility use and any necessary mitigation can then be objectively established. The overall effort will support goals of this plan to implement effective public safety planning and mitigation of coastal hazards. A 2008-2009 project sponsored by the State Office of Planning undertook the technical amendments necessary for the adoption of new wind speed design mapping provisions into the International Building Code 2006 and ASCE-7 standard by the County of Hawaii, which xvii Hawaii County Multi-Hazard Mitigation Plan Executive Summafv is located within a hurricane hazard region. Improvements in wind hazard mitigation can now be implemented through the use of these specialized "uniform-risk" wind speed maps for design use as a local code adoption to the State amendments to the International Building Code (IBC). A consistent level of protection for hurricane hazard would then be achieved in structural design on the island of Hawaii, thereby mitigating future hurricane losses in new construction. Implementation of the topographic and directionality in the County of Hawaii Building Code would fulfill recommendations made by structural engineers after Hurricanes Iwa(1982)and Iniki(1992). In addition, the enactment of the TBC 2006 with these wind provisions would be critical to maximizing federal disaster public assistance aid in future disasters. Section 406(e) of the Stafford Act requires that FEMA provides post-disaster public assistance aid funding only to the level of the code in place at the time of the disaster. When a county building code or any state building regulation is obsolete, any cost differential for repairing state buildings to modern standards currently becomes the responsibility of the State and County. Enacting a modern code would enhance the amount of federal aid available after a disaster to allow the State to rebuild in conformance to the latest disaster-resistant codes. Otherwise, post-disaster rebuilding and repairs may recreate vulnerabilities and weaknesses of antiquated codes that just happened to be in place at the time of the disaster. Thus, key benefits of this project are improved disaster-resistant construction immediately to reduce losses, and increased federal aid for post-disaster recovery of the State after the next disaster. • State Building Code Statute Act 82 (May 21,2007) The State legislature found that the State has traditionally allowed the individual counties to establish their own building codes. In the past the counties adopted various portions of the Uniform Building Code, so the code differs from county to county. The status of fragmented building requirements in Hawaii is of serious concern to those involved in building ownership, design, construction, and insurance. Over forty states have adopted some form of a statewide building code. The adoption of a uniform set of statewide building codes applicable to one and two family dwellings, all other residential uses, and commercial and industrial buildings, and state buildings makes it possible for building owners, designers, contractors, and code enforcers within the State to apply consistent standards. The International Building Code is currently being considered for adoption by all counties. The health and safety considerations related to the codes are of statewide interest, especially relating to emergency disaster preparedness. Act 82 was implemented in Hawaii Revised Stature 107-Part II HRS 107 Part IT created the authority of the State Building Code Council, any law to the contrary notwithstanding, to establish a comprehensive State Building Code. Under HRS §107-25, the State Building Code is required to include various codes and design standards that are listed specifically or generically in the statute. The State Building Code Council includes the State agencies and County jurisdictions with pre-existing regulations affected by a State Building Code. xviii Hawaii Countv Multi-Hazard Mitigation Plan Executive Summafv • The purpose of the law is to require the Department of Accounting and General Services to establish and implement a State Building Code • Creates a State Building Code Council with decision making authority • Preserves responsibilities for administration, permitting, enforcement and inspection as presently held by each county • Prohibits conflict with chapter 464, HRS, Professional Engineers, Architects, Surveyors and Landscape Architects • Requires adaption of the State Building Code by the local county government within 2 years • Permits county amendments without State Building Code Council approval • There is great importance of adopting the IBC as it relates to the County's ability to advance in FEMA's Community Rating System (CRS) program. If the iBC is not adopted, the County cannot advance past CRS Classification 8 or only a 10-percent reduction in flood insurance premiums for all Hawaii County policy holders. • HAZUS MH Earthquake Modeling with updated building inventory database The Hawaii and Maui County general building stock data was enhanced by using residential and commercial property tax databases and several state government property databases. The project incorporated the unique Hawaii building types including the vulnerable post and pier single-wall construction type that statistically exhibited much higher damage levels than conventional wood-frame construction on slab-on-grade. • Post and Pier Retrofit Study A survey of 53 post and pier houses on the island of Hawaii was performed to determine the typical structural characteristics and variations in structural properties of these houses in the most vulnerable areas. The survey also investigated the extent of damage of these homes during the 2006 earthquakes along with any attempts to retrofit the houses at the time of survey. Based on this survey, a number of prototypical models of post and pier houses were analyzed for different levels of ground motion. A number of aspects of the houses were found to require retrofitting for even moderate levels of ground motion. From the analysis, three retrofit options were developed, with the applicability of each retrofit based on the location of the house and its structural properties. The retrofits are presented in a general format that can be applied to a wide range of houses without specific input from a structural engineer, except in special cases. Retrofit Option 1 is primarily a strengthening of connections using the existing post and pier foundation system, applicable in regions of low to moderate seismic hazard and for houses with moderate differential post heights. Retrofit Option 2 uses additional plywood shear walls between the ground and first floor of a house to provide additional lateral strength and stiffness to the foundation system. This retrofit is applicable in all regions with most combinations of differential post height and other structural properties. Retrofit Option 3 uses masonry shear walls to provide additional lateral strength and stiffness. This option is applicable for any post and pier house, although in some extreme cases a structural engineer would need to be consulted if the properties of the house fall outside the range of properties considered in the report. xix Hawaii County Multi-Hazard Mitigation Plan Executive Summafv • Soil NEHRP Classification Maps To be able to utilize the strong motion data recorded by the USGS Hawaiian strong motion network, knowledge of the subsurface site conditions beneath the USGS stations was required. The subsurface geology and, more important, the shear-wave velocity (Vs) structure beneath the USGS stations has been unknown to date. The information is invaluable to verify the appropriateness of the empirical ground motion attenuation models being used in the state hazard maps produced by USGS and in site-specific hazard analyses for engineering design. To obtain Vs information beneath the USGS strong motion sites, Spectral Analysis of Surface Waves (SASW) surveys were performed by the University of Texas, Austin, and URS Corporation in January 2008 (Wong et al. 2008). The SASW technique has been used to obtain Vs profiles at other USGS strong motion sites (e.g., Seattle, the Imperial Valley, and Los Angeles), and this technique has been well validated against other approaches, such as down-hole surveys (e.g., Wong and Silva 2006). The technique has been particularly useful in volcanic regimes where interbedded volcanic sequences can result in low-velocity zones (e.g.,Yucca Mountain and Los Alamos). The SASW methodology is a non-destructive and non-intrusive seismic method. It utilizes the dispersive nature of Rayleigh-type surface waves propagating through a layered material to estimate the shear-wave velocity profile of the material (Stokoe et al. 1994; Joh 1996). In this context, dispersion arises when surface-wave velocity varies with wavelength or frequency. Dispersion in surface-wave velocity arises from the changing stiffness properties of the soil and rock layers with depth. Spectral analysis is used to separate the waves by frequency and wavelength to determine the experimental ("field") dispersion curve for the site. An analytical procedure is then used to theoretically match the field dispersion curve with a one-dimensional layered system of varying layer stiffness's and thicknesses. The one- dimensional Vs profile that generates a dispersion curve that matches the field dispersion curve is presented as the profile at the site. An active seismic source is required for the SASW surveys. In these surveys, one of the NSF's Network for Earthquake Engineering Simulation (NEES) mobile vibrators, known as "Thumper," was used. Thumper has been designed to be a moderate- to high-frequency vibrator for use in seismic reflection and surface wave projects. The surveys took place from January 7 to 17, 2008 at 22 USGS strong motion. Several surveys were also performed at Kawaihae Harbor. The high PGA's recorded at the Waimea Station and the North Kohala Police Station are probably due to thin soil site amplification where a strong velocity contrast exists between the soil and underlying basalt. Based on the survey results, all of the 22 USGS strong motion sites are "soil" sites with Vs'0 values ranging from 442 ft/sec at the USDA Laboratory in Hilo (National Earthquake Hazards Reduction Program [NEHRP] site class E) to 1,812 ft/sec at the South Kohala Fire Station (NEHRP Q. Surprisingly, none of the strong motion sites had rock-like Vs30 values, even sites where basalt outcropped at the surface, such as at the University of Hawaii at Hilo. xx Hawaii County Multi-Hazard Mitigation Plan Executive Summafv As demonstrated in the 2006 earthquake, where some strong motion stations recorded peak horizontal accelerations close to Ig, site response effects can be significant on the Big Island. As part of FEMA-supported studies following the earthquake, a new 1:100,000-scale map of site conditions on the Big Island of Hawaii was produced. The mapping makes use of about 25 new SASW measurements (Wong et al., 2008) and 1:100,000-scale geologic mapping by Sherrod et al. (2007). An earlier 2006 site class map portrayed nearly all of the island as NEHRP site class B; however, based on about 20 SASW measurements in areas mapped as basalt, it is believed that most of the island should be mapped as NEHRP C or D. Vs30 estimates for these basalt sites ranged from 844 to 1,812 ft/sec, spanning NEHRP classes C and D. The median value for these Vs30 estimates is 1,304 ft/sec, with a log mean of 1,274 ft/sec and a standard deviation of 274 ft/sec. The sites cover a range of basaltic rock conditions as depicted on the geologic map, including lava flows, scoria cones, littoral deposits, spatter or tuff cones, cinder cones, and lava domes. Other geologic map unit groups for which only a few Vs30 estimates were made from SASW data include alluvium, ash/tephra, and artificial fill. These were assigned to map units NEHRP site class D, C to E, and C to E, respectively. Geologic deposits for which there is no quantitative velocity data and preliminary site class assignments have been made are sand dunes (D), landslide deposits (D), and glacial deposits (D). • Landslide Hazard Maps A conceptual level slope risk map was prepared for the Hawaii HAZUS Conversion Project, using an adaptation of the slope hazard methodology given in the FEMA 2007 HAZUS-MH MR3 Technical Manual. The URS approach involved the interactions of three primary slope hazard input criteria simplified to low,medium and high hazard susceptibility The current HAZUS mapping for the Island of Hawaii is an initial pilot study allowing a scientific basis for incorporating slope hazards into island wide scenario loss estimates. This approach provides a simplified method where high resolution topography and rainfall data can be used with existing geologic maps in digital format to develop slope hazard criteria for rural,remote and developing areas where detailed slope hazard input data is not available. Plan Update and Maintenance Rather than just describe the need for plan maintenance and general tasks, this chapter was revised to provide specific actions and summary of specific ongoing hazard mitigation projects that will impact the next adoption of the mitigation plan. Thus, this provides a checklist of the resources expected for the plan maintenance taskings. This should ensure continuity and connectivity with ongoing and future work that should improve the next plan. This mitigation plan will be reviewed annually with input from an interagency Hazard Mitigation Planning Committee and an organized network of community groups in each district. The annual review will result in revised work-plans; budget requests to the County CIP, State Civil Defense, and other funding sources; suggested amendments to codes and plans; and proposed revisions to the text of this plan. xxi Hawaii County Multi-Hazard Mitigation Plan