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Page 24 <br /> Control Panel la %liew(NISI —PVC Splice Box <br /> Modal Simplex Pumping System w+com Grlps <br /> � tdodo) <br /> _ Flaergla:s Gasketed Lid Ilh <br /> Slalriess Stool Bolts <br /> Model <br /> Flbotgiass Gaskolod Lid <br /> with 5lalnless 5Ieel BOIL Sbpe Ground PVC Rise•vdth Gromr'atts) <br /> Model A-y from Riser Modc•I <br /> PVC Rldar w11n Glommotis} To Control Panel Dlachaga Asombly <br /> Modal <br /> t,4ode1 <br /> Conduh Seal fiexDte Nose <br /> sdadel Lfft e,t Oischoroe <br /> Tank Adapter(Cas1 or B.R d) <br /> Inlet Tee Model <br /> floe lnducar <br /> L-ol Control <br /> Flaal Assembly <br /> Model <br /> ` —_ �fer Gnriddga <br /> ault heel Ports <br /> prenco Etlluem Pump <br /> h+rode) <br /> BlotuhFPump Vault <br /> Nboel <br /> Figure 6. Existing tank retro-fitted with STEP package. <br /> Infrastructure Phasing Considerations <br /> The Town of Mashpee's intent is to address critical areas in small increments, involving smaller amounts of up- <br /> front capital costs. Orenco effluent sewers are easily oversized for future connections, due to the lack of solids <br /> in the main lines, to accommodate future connections, at relatively low up-front and ongoing costs associated <br /> with conveyance infrastructure. Because up to 85% of the cost of Orenco effluent sewers is associated with on- <br /> lot equipment packages (STEP system), the cost to upsize/oversize conveyance system infrastructure, a <br /> network of small diameter PVC or polyethylene pipe, is minimal .., typically a small percentage of total project <br /> costs. Conventional gravity sewer collection systems, on the other hand, require expensive, large diameter <br /> gravity mains that are costly to oversize and maintain and are the majority of the cost of traditional sewer <br /> programs. Grinder sewers, because they require 2 ft/s scouring velocity, have severe challenges when <br /> oversizing force-mains for future connections.As a result, Orenco effluent sewers provide the most cost <br /> effective, up-front and long term, collection system option for phased approaches. <br /> Existing Equipment Considerations <br /> Recently installed tanks with watertight and satisfactory specifications are sometimes acceptable, and some <br /> `newer'communities have used existing tanks in an Orenco effluent sewer. <br /> The preponderance of septic tanks sold in the U.S. are structurally unsound and almost never watertight. Where <br /> groundwater levels are high, leaky tanks allow infiltration that can overburden a system's pumps and treatment <br /> facilities. Where high ground water is not a problem, leaky tanks exfiltrate and the scum layer lowers to the <br /> discharge ports, causing solids and grease carryover and subsequent maintenance and pollution problems, In <br /> an effluent sewer, leaky tanks are unacceptable. Watertightness is a requirement that should be mandatory for <br /> all onsite applications. Explicit details and specifications are necessary to ensure quality tank construction. Even <br /> so, unless strict quality control is uniformly enforced, the problem will persist because manufacturers of quality <br /> tanks will find it hard to compete. The extra cost of a high quality tank is insignificant when compared to the cost <br /> of maintaining and rectifying a system with inadequate tanks. <br />