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2021 Multijurisdictional Local Hazard Mitigation Plan 8.4.4 Environment The environment would be vulnerable to a number of risks in the event of dam failure. The inundation could introduce foreign elements into local waterways, resulting in destruction of downstream habitat and detrimental effects on many species of animals, especially endangered species. 8.5 FUTURE TRENDS IN DEVELOPMENT The planning partners’ general plans and other planning activities provide guidance related to hazard mitigation and future development. Dam failure is currently not addressed as a stand-alone hazard in the safety elements of the municipal partners’ general plans, but flooding is. Flood-related policies in the general plans will help to reduce the risk associated with dam failure for all future development in the planning area. Municipalities participating in this plan have established comprehensive policies regarding sound land use in identified flood hazard areas. Most of the areas vulnerable to the more severe impacts from dam failure intersect the mapped flood hazard areas. However, there are structures on the perimeter of the dam failure inundation outside of the regulated floodplain that are not subject to floodplain management codes and standards. These structures would be more vulnerable than those constructed with floodplain codes and standards. 8.6 SCENARIO An earthquake in the region could lead to liquefaction of soils around a dam, without warning during any time of the day. A human-caused incident such as a terrorist attack also could trigger a catastrophic failure of a dam that would impact the planning area. Failure of a high hazard dam in the County would likely result in loss of life, roadways, structures, and property, and exert severe impacts on the local economy. While the possibility of failure is remote, results would be devastating. The worst-case scenario would involve failure of the Lower Crystal Springs Dam. In addition to severe property damage and potential injuries, loss of water from the Crystal Springs Reservoir could lead to reduction in available potable water for the County and the Bay Area. Coupled with the ongoing drought throughout the state and already low water supply availability, this damage could lead to significant water shortages. 8.7 ISSUES The most significant issues associated with dam failure involve properties and populations within inundation zones. Flooding as a result of a dam failure would significantly impact these areas. Warning time for dam failure plausibly would be limited. Moreover, dam failure is frequently associated with other natural hazard events such as earthquakes, landslides, or severe weather, which limits predictability of dam failure and compounds the hazard. Important issues associated with dam failure hazards are as follows:  A significant number of the structures located in the dam failure inundation zone are located outside of special flood hazard areas, meaning that they are not constructed to withstand floodwaters and are less likely to be covered by flood insurance. Even structures that have been designed with flood hazards in mind may not be able to withstand the height and velocity of flow from a dam failure event.  Addressing security concerns and the need to inform the public of the risk associated with dam failure is a challenge for public officials.  California law requires that a property’s location in a dam failure inundation be disclosed to a seller if the seller or the seller’s agent has knowledge of the property’s location within the hazard area or if the local 8-12