2006-097A. - Laserfiche WebLink

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Table 1 depicts the cost breakdown used to estimate the cost of this alternative. In order to develop the cost estimate for this alternative, the following assumptions were made: • Power distribution is underground through polyethylene conduit • Change distribution to 480V, 3-phase power • Property can be obtained for generator/ATS sites (land cost is included) • Two generators will be outside a building with a sound attenuated enclosure • One generator will be inside a building (building cost is included) • Fuel tank — sub -base, 660 gallons with critical muffler • Conduit routes to largely follow existing collection system routes (backyards) • Grade in the area is essentially flat • The cost includes 20% for contingencies and administrative • The cost includes 10% for engineering and planning fees. If 480V, 3-phase power is not available from the power company, then cost will be 40% higher to distribute at the existing 240V, 3-phase service ($3,174,000). This is due to voltage drop losses requiring nearly doubling the wire size. In order to convert to 480V service, each of the existing 58 distribution panels would have a new step- down transformer installed to drop back to 240V service. Discussion of Benefits and Disadvantages — For this alternative, there is no change to the system that will be readily apparent to customers. The existing system remains in place, the only change being the ability to maintain operation during power outages. Unfortunately, the system will continue to be a high maintenance problem with over 400 individual pump stations, 58 electrical service substations, and three additional sites with complex electrical systems. The system will also continue to be susceptible to flood interference since the individual pump stations remain. The generator site will be built above 100 -year flood elevation, which will require each site to be raised. The generator sites will be included with buildings that will attenuate sound, provide proper security, and reduce risk of tampering with the system. This alternative will be readily implemented and would result in very little, if any, interruption of service for the existing system. 2. Replacement with Gravity Collection System: System Description — The conceptual design of a gravity sewer system is based on constructing a master pump station at the intersection of 16`h Street and 4`h Court to collect individual homes' sewage using a gravity force main system as shown on Figure 2. The gravity system includes the gravity and force mains and a single master pump station. The master pump station will transfer sewage to the County's existing pump station located at 141h Street via an existing 6 -inch force main. An emergency Page 3 of 7 F Widaics\UTILITY- ENGINEEIUNGVrojws- Utility Covvoction Pc UNIRC - Rock dgc Scwar FEMA Mitigation UCP p 2521TSS& Engincccring Rcpo kTcch Mcnno Rockridgc - Vacuum Option doc