Chapter 1 - Hazard Mitigation Web Portal - State of California

State of California Multi‐Hazard Mitigation PlanChapter 5 – Earthquakes, Floods and Wildfires: Risks and StrategiesMitigation in High‐Rise BuildingsGuidelines are available for the retrofit of building contents and nonstructural building systems,such as ceilings, light fixtures and mechanical equipment (FEMA 74). Structural retrofits can beaccomplished using ASCE 41‐06 or the International Existing Building Code. A Tall BuildingsInitiative has been launched by the cities of Los Angeles and San Francisco to developperformance‐based engineering for future new tall buildings.(http://peer.berkeley.edu/tbi/index.html )Mobile HomesCalifornia has approximately 473,000 mobile homes. HCD regulates installations and alterationsto mobile homes in approximately 3,600 of the state’s 5,800 mobile home parks. Localgovernments have enforcement jurisdiction over the remaining parks, as well as over allmanufactured home installations outside of parks. In 1974, HCD began to require engineeredtie‐down devices for wind loads in excess of 15 pounds per square foot for singlewide homes.However, most mobile homes installed from 1974 to 1994 were multi‐wide or were installed inregions with lower wind speed and were exempt from this requirement. Therefore, mosthomes installed prior to 1994 are not attached to their foundations or otherwise braced to resistearthquake loads.Numerous studies have determined that the performance of pre‐1994 mobile homes inCalifornia earthquakes is significantly worse than that of conventional wood‐frame dwellings.The primary earthquake weaknesses are the temporary foundations on which such homes arecommonly placed. Homes on inadequate foundations can shift and fall several feet inearthquakes, severing gas lines. Doors can become stuck, trapping occupants and creatingserious threats to life in events with fires (SSC 95‐01, Turning Loss to Gain).Mitigation of Mobile HomesIn 1981, the state began to regulate the design and construction of optional EarthquakeResistant Bracing Systems that can be installed under existing mobile homes at the owners’discretion. Since 1994, the state has required that new or relocated mobile homes be braced toresist earthquakes in one of three ways:• Conventional foundation systems similar to wood‐frame dwellings• Engineered tie‐down systems• Earthquake‐Resistant Bracing SystemsProgress Summary 5.K: Mobile HomesProgress as of 2010: California HCD revised its regulations in October 2009 to require that fuelgasburning water heaters in new mobile homes be seismically braced upon installation. Thisregulation extends to existing mobile homes by requiring seismic bracing to be demonstratedupon re‐sale or rental. The current high priority for HCD for future mobile home mitigation is topursue a requirement for installation of fire sprinkler systems in new manufactured homes. Thisis expected in January of 2011.Mitigation of Natural Gas Systems in BuildingsThe CSSC has developed guidance for local governments for mitigating natural gas systems inbuildings, titled Improving Natural Gas Safety in Earthquakes (SSC 02‐03). The most cost‐Public Comment Draft – July 2010 164