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Pipelines do not represent a safety hazard unless their structural integrity is compromised, resulting in a release of natural gas or crude oil to the environment, and in rare cases,ignition of the product released. To assess the hazard posed by the pipelines, the pipeline risk analysis must identify: The events that could lead to a pipeline leakimpture and ignition of the product; The probability or frequency of such events; the consequences of such events; The annual individual risk(expressed as probability of being exposed to a fatal hazard over a one- year period) associated with leaks or ruptures and explosions at varying distances from the pipelines; and The recommended setbacks to avoid individual risks. The events that could lead to a pipeline leak or rupture include: third party dig-ins, corrosion or deterioration,weld or material defects, and ground movement. The events that could lead to the ignition of the product released include: sparks caused from metal saws or other equipment breaching the pipeline, mechanical equipment that create sparks as part of internal combustion,and open flame sources. The probability of such events was based on Federal Department of Transportation, Office of Pipeline Safety(OPS)incident data.The consequences of such events was determined based on computer modeling performed by Quest Consultants,Inc.using the CANARY computer software hazards analysis package,which takes into account release conditions,ambient weather conditions, effects of local terrain, and mixture thermodynamics(see the pipeline risk analysis for a description of the modeling approach, modeled assumptions,and results).The consequences analysis evaluated the consequences of both contamination and explosion. With respect to contamination hazards,the analysis indicates that leakage or rupture of the Chevron crude oil pipeline(Pipeline CSFM 0499)could result in soil, surface water, and groundwater contamination,and that this contamination could result in exposure of people to toxic fumes or ingestion(if potable water wells or downstream drinking water surface water intakes were located in the vicinity). With respect to explosion hazards,the analysis estimates that the maximum downwind — hazard zone distance for a torch fire resulting from full rupture of the largest natural gas pipeline(the 36- inch PG&E natural gas pipeline,Pipeline L401)is 1,496 feet with immediate ignition and 912 feet with delayed ignition. Maximum torch fire,pool fire, and flash fire hazard zones would be smaller for the smaller diameter natural gas pipelines and for holes in the pipelines rather than full rupture. The annual individual risk associated with such events was determined by combining the likelihood of pipeline leak or rupture and ignition events with the associated consequence to predict the probability of an individual being exposed to a fatal hazard over a one-year period. Land use occupancy factors(i.e., percent of time each use is occupied)were estimated and included as an input to the annual individual risk calculations. For this analysis, school and residential uses were assumed to be occupied 100%of the time, — office, commercial, light industrial and community college uses 30%of the time, and open space and recreation areas 15%of the time. Risk transects(measurements of individual risk as a function of distance from a pipeline)were constructed for the pipelines as part of the quantitative risk assessment modeling.The transects illustrate how the risk decreases with distance from the pipelines. Individual risk contours constructed for the _ system of pipelines in the College Park area illustrate the combination of risk because of multiple pipelines in the different utility corridors(Figure 3,Appendix K). An acceptable level of individual risk associated with underground pipelines has not been established by the state or the federal government for new land uses other than schools. Various governmental agencies EDAW College Park at Mountain House Specific Plan III Draft EIR Public Health and Safety 4.9-34 San Joaquin County