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distribution panels to assure that no pump station is without power for more than three hours (one generator for every seven to eight stations, 24 -hours per day). Recent Storm Related Problems: During the recent hurricanes, power was lost for prolonged periods lasting as many as nine days. The Utilities Department, in addition to the 58 distribution panels within Rockridge, has over 250 lift stations throughout the County that also rely on portable generators for backup emergency power. The number of generators and crews needed to service this number of sites is not available. As a result, sewage systems backed up through out the Rockridge community creating a public health hazard over an extended number of days. Flooding of the low-lying area also contributed to health concerns. The top of each pump station is flush with grade and therefore is susceptible to infiltration during flooding which further exacerbates storage capacity of the system. Geological Considerations: Beneath the grade in the Rockridge area, there is an unusually small distance from grade to bedrock, sometimes as low as 2 to 3 feet. The neighborhood was originally built as a septic tank system. Due to the rock bed, percolation rates were very unfavorable for such a septic system. In the early 1990's, the Connt'y ICplaCed Lie Septic tank s"y"stem with the current system. it was found to be difficult and costly to install a gravity system due to excavation through rock. Therefore, the low profile piping system that exists now was installed. Hazard Mitigation Alternatives: It has become a major priority to the County to modify the existing system and mitigate future hazards due to power outages and flooding. The following three alternatives were investigated: 1. Dedicated Emergency Power Generators for Existing System: System Description — The existing distribution panels can be re -fitted to feed power from buried conduits connected to dedicated automatic transfer switch (ATS) stations. The ATS stations would receive normal power from the power company from the existing overhead distribution system. The ATS stations would be equipped with emergency power from permanent generators. Upon loss of normal power, the ATS will automatically start the generator and then switchover to emergency power to keep all stations fully operational during the power outage. It is proposed under this alternative to secure up to three sites to locate ATS and generator equipment. The three sites must be located to minimize the distance from the generator to each individual distribution panels. From these three sites, underground power is to be installed largely along existing wastewater collection main routes, storm water mains, or other utilities' easements. Figure 1 depicts the proposed system for this alternative. Likely Construction Cost — $27000,000 Page 2 of 7 F:\Utilitics\UTILITY- ENGINEERING\Projccu - Urili\y Comvuaion Per uh RC - Rock idgc Scwa FEMA Mitigation UCP N 3521\PBS&J Engincccring Rccpon\Tcch Mcmo Roclmdgc - Vacuum option doc