Guam Hazard Mitigation Plan - Western States Seismic Policy Council

SECTIONFIVERisk Assessmentoutfall pipe is damaged close to shore and sewage is released closer to shore than intended.The total coastal surface water potentially affected by a sewage hazard event within a 1-mileradius of each of the 3 sewage plants is 6.2 square miles. This hazard is expected to affectonly coastal surface water, and not any of Guam’s land area.• National Pollutant Discharge Elimination System air and water permitted facilities: Asshown on Figure D-19, 22 facilities on Guam have National Pollutant Discharge EliminationSystem (NPDES) permits to discharge certain quantities of hazardous waste into surfacewaters. An additional 15 facilities also have the potential to discharge HAZMATs into theatmosphere. The locations of these facilities have been determined by information obtainedfrom GEPA. For facilities that are permitted to discharge into the water or atmosphere, a 1-mile radius around each facility has also been determined to be the area potentially exposedto a HAZMAT release. As such, the facilities that have the potential to discharge into waterencompass 30.7 square miles. Assuming meteorological conditions are not a factor, an areaof 29.5 square miles will be affected if a release were to occur from one of the fifteenfacilities permitted to discharge to the atmosphere.• Hardfill sites: Figure D-20 shows the facilities that have the potential for a HAZMAT (fireand toxic gas) release from a hardfill site. The area of susceptibility for this type of releasecovers an area of 22.3 square miles using a 1-mile radius around each site.• Pre-CERCLIS sites: 409 Pre- Comprehensive Environmental Response, Compensation, andLiability Information System (CERCLIS) sites exist on Guam. Location information is onlyreadily available for some of these sites, and a susceptibility analysis can only be conductedfor about one-third of the sites. The amount of other information available for these sitesvaries. For many of the sites, the types and quantities of HAZMATs are unknown. For manyof the sites, the location is known, but the pathway(s) for a HAZMAT release is unknown.Therefore, the susceptibility analysis conducted for the known Pre-CERCLIS sites is verygeneral. The potential area exposed to a HAZMAT release has been determined to be a 1-mile radius around each known site. Figure D-21 shows the 142 known Pre-CERCLISfacilities and the 1 mile potential exposure area around each location. The area ofsusceptibility to a HAZMAT release from the known Pre-CERCLIS sites is 139.71 squaremiles.Previous OccurrencesNo Federal disaster declarations have been made on Guam specifically for a HAZMAT event.The National Response Center collects information on all reported HAZMAT releases. Table 5-10 lists oil and chemical spills for Guam over a 10-year periodOne of the most significant HAZMAT events to have occurred on Guam happened while SuperTyphoon Pongsona was tracking across Guam. During this incident, two petroleum tanks at theMobil fuel storage facility at the Guam Commercial Port caught fire. The fire burned for 6 days,destroyed four petroleum tanks, and resulted in a temporary halt in civilian gasoline sales. Thetank that first caught fire had been damaged during Typhoons Chata’an and Halong, and as aresult, standard safety precautions for fuel storage tanks were not followed for this tank prior totyphoon landfall. It is believed that static electricity built up in the tank, causing the fuel vaporsin the tank to ignite. The fire deposited a large amount of soot in the adjacent harbor, and the fireretardants used to control the fire may have entered the adjacent marine environment.5-30