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TECHNICAL MEMORANDUM To: Steven J. Doyle, Assistant Utilities Director, and Indian River County From: Bob Morrell, Project Manager, PBS&J Date: March 14`h 92005 Re: Rockridge Sewage Collection System Hazard Mitigation -Alternatives Indian River County Utilities had experienced significant problems in maintaining operation of the sewage collection system within the Rockridge subdivision during the recent storm events in September of this year. In response to these events, Indian River County Utilities contracted with PBS&J to develop and evaluate different alternatives to mitigate the potential for future re -occurrence. Also, the County requests PBS&J to investigate possible funding options through the Federal Emergency Management Agency (FEMA). PBS&J has made an analysis of three alternatives to correct problems with the existing system. These alternatives include providing emergency power to the existing system as it is currently installed, replacing the system with a gravity flow collection system, and replacing the system with a vacuum collection system. This technical memorandum presents PBS&J's findings and recommendations. This document will form the basis for discussions to be held with the County to select the alternative to pursue for a design and construction effort. As part of these discussions, funding options will be reviewed and identified. Introduction and Background: Existing S s� Rockridge is a community of predominantly single-family residential homes. Of these, 413 existing residences are connected to a sewer collection system that relies on individual pump stations at each home. The pump stations include a single two horsepower pump powered through a 240V, three-phase control panel which runs on an on/off float control system. The 413 control panels are powered through 58 distribution panels located throughout the neighborhood which power from three to eleven control panels each. Each distribution panel is fed by an overhead power grid, which also serves the residential power. Currently, each distribution panel has a generator receptacle that can be used to provide emergency power in the event of a power outage. The wetwell at each pump station is a 30 -inch diameter fiberglass tank with a three-foot depth. The pump is turned on its side for piping considerations, which reduces pump efficiency and pumping volume available for storage. Pumping volume within each pump station is approximately 35 gallons. For a typical residential flow of 250 gpd, this would represent 3 to 4 hours of storage capacity on an average basis. During any prolonged outage, as many as eight generators would be needed to service the 58 Page 1 of 7 F:\Utilirics\UTILITY - ENGINEERING\Projccu -Utility Ccmvuaion Pcmd\siJRC - Rack dgc Sewa FEMA MiJgwion UCP a 2521W65&J Engincemng Repon\Tech Mcmo Rocl dge- Vacuum Option doc