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N ovember 2013 MM # 1351 SANITARY SEWER FEASIBILITY STUDY & REPORT NORTH SEBASTIAN AREA VACUUM COLLECTION SYSTEM ALTERNATIVE Vacuum sewers are a mechanized system of wastewater transport and represent a viable option when the service area has at least (150) users. Unlike gravity sewer flow, vacuum sewers use differential air pressure to move the sewage. A central source of power to operate vacuum pumps is required to maintain vacuum on the collection system as illustrated in the vacuum system schematic included in the Appendix of this report. The vacuum collection system will be located in the street right-of-way and include a valve pit along with the vacuum sewer pipelines. Each house o r user will have its own sewer lateral identical to the sewer lateral used on a gravity collection sewer system. In a gravity sewer system, the sewer lateral will connect to a sewer collection system pipeline in the street right-of-way. However, in a vacuum system, the sewer lateral will connect to a valve pit located in the street right-of-way but in close proximity to the property line. When possible, the valve pit will be located in a manner to serve two (2) or more users, but in cases where Tots are large or other conditions do not permit a valve pit serving more than one (1) u ser, a valve pit will serve each Individual user. Each valve pit has its own collection sump which is connected directly to the vacuum system pipeline. The sump compartment is separated from the top valve chamber by a sealed partition. There are no electrical connections required at the valve pit as the entire system in the valve pit is operated by pneumatic pressure differential. The top of the valve pit is at existing grade and furnished with a standard 24 -inch diameter manhole access cover. A descriptive drawing of a typical valve pit is shown in the Appendix of this report. Each of the valve pits discharge into a vacuum sewer system when the collection sumps are full. The vacuum sewer system consists of vacuum sewer mains constructed of 4 -inch and 6 -inch PVC pipe with division valves as required. The vacuum sewer mains are designed to maintain a generally downward slope towardtheir ultimate discharge into the central vacuum station The vacuum systems is designed on a saw tooth pattern and they can have slops as flat as 0.0020%. The vacuum sewer mains are constructed at a depth of 4- to 5 -feet below grade. The vacuum sewer main system ultimately discharges into the central vacuum station which is the "heart" of the vacuum collection system. The equipment installed in the central vacuum station is similar to that of a conventional sewage pumping station except vacuum is applied to the wet -well (collection tank) that is sealed. Major components include the tank, sewage pumps, vacuum pumps, control panel, and stand-by electrical generator. A typical vacuum station schematic is shown in the Appendix of this report. 11