3/15/2011 SEWER COMMISSION Minutes

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5. n • J M VAC recommended a rebuild every to years, although it is not always completed in that timeframe. The rebuild kit for the valve costs$55 and the rebuild kit for the controller costs $551, which should be rebuilt every 7 years. Mr. Docherty clarified that rebuilds varied based on service and was dependent upon the number of homes connected to the system, adding that typically two homes would be connected to one valve pit. Mr. Docherty stated that the valve pit was located off of the road and-covered, in a grassy area by a cast iron grate. Mr. Docherty stated that PVC pipe SDR 21-is used for collection piping, which is thicker and heavier than standard gravity pipe. The diameter is typically -1 o inches with trench depths ranging from 4 feet to 16 feet. The saw.tooth profile allows the pipe to remain shallow. The vacuum station houses components such as the tank, vacuum pumps, sewage pumps, control .panel and the backup generator. Sewage and vacuum pumps are duplex so that if one pump is down, another pump kicks in. The vacuum tank is typically made of steel or fiberglass and the typical pressure is. 2 inches of mercury column gauge. Sewage pumps are skid mounted and assembled at the factory, then installed. The control-panels are PLC. Mr. Docherty stated that bio filter of woodchips is used to eliminate odor_ Mr. Docherty discussed the ways in which a vacuum sever system can save money, such as with increased construction costs that are incurred with gravity systems. Lifts are used to get around other existing pipes and placement of the valve pits and pipes off of the street'limits the need for street repaving. Homeowner electricity is not required because the.valve is pneumatically operated. The valve pit includes no electrical connections. The system allows easy access and is a lightweight sst and safe during construction. An immediate leak notification alarm is in place to prevent big problems. Mr. Docherty summarized the recent problem that occurred in Provincetown, describing the installation of the system. Mr. Docherty stated that the entire system is tested fir leafs as it is being installed and upon completion of the installation. In Provincetown, a valve had been placed before connecting the pipe and the candy cane and the tubing pinched, imploding the pit,. but not destroying the sump completely. Rocks eventually entered the system through cracks and during a high flow time, a leak occurred. Isolation valves were inaccessible due to parked cars. Mr. Docherty stated that the operator did not feel he had the authority to shut down the single main to the vacuum station, so the entire system came down. Chairman Fudala inquired whether AfRVAC designed the system and 1 -r, Docherty responded that AIRVAC was a supplier and assisted with the design during construction with one An vAC supervisor. fir. rginton-Smith added that wastewater was flowing in the streets-because they were pumping into the end of the line which caused the overflow. Mr. ra inton-Smith also noted that the design was based on a grinder pump original design and that a combination of issues caused the problem in Pro incetown. M1-. Docherty indicated that new pits are one piece pits with a dedicated air terminal making it difficult to implode a pit. Future plans include developing pit alarms that will require no electricity. Regarding a plan for 1 lashpee, M-F. Benton-Smith referenced the Town's watershed areas and � highlighted wastewater treatment plants installed by various developments. Mr. raginton- Smith referenced a proposal that was submitted for the 1 ashpee watershed in 2005 which would include the installation of a vacuum station and also the addition of the Johns'Pondl Ashumet Pond area, although the area may present a challenge due to'major topographical shifts. The 5