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t <br /> Page 25 <br /> Existing tanks; therefore, require thorough evaluation to confirm watertightness and structural integrity. Leaky <br /> and structurally inadequate tanks, a common theme among old tanks, often translates to increased infiltration, <br /> higher maintenance costs, less efficient solids digestion,and compromised secondary treatment processes. <br /> Existing_tanks,-as_a_result,lequire-a i tailed-evaluation-before-utilization. <br /> Older communities, Glide, Oregon for example, initially inspected the first 100 or so tanks for use in a new <br /> effluent sewer system at that time.Tank contents were pumped, inside walls were cleaned with chlorine, and all <br /> tanks were smoke tested. In the older community, failure rates were 95%. <br /> The Town of Mashpee has a high number of recently installed interceptor tanks,thus we have assumed that a <br /> large percentage of on-site costs,which are the majority of collection system infrastructure costs, can be <br /> reduced. <br /> Non-Mandatory Connections <br /> With traditional gravity sewer collection and centralized wastewater treatment immediate customers are <br /> necessary to equitably distribute the initial capital cost and the initial 0&M cost. This, in large part, is why <br /> mandatory connections are necessary when a conventional sewer approach is utilized. Mandatory connection is <br /> often met with opposition because newly installed on-site systems are treated the same as aged and failing <br /> septic systems. Owners of newly installed septic systems often believe that they should be compensated for the <br /> lost investment they have in their on-site wastewater system. <br /> Install centrallzed <br /> mpacily -` <br /> \ <br /> n a <br /> Wsswoea er new p <br /> 15 <br /> W / Lend time u(certr5li<ed capacity <br /> L) r-tld 1/Jj <br /> Idle centrallzel capacity <br /> _ f . Clvcrhuill Wp.xity <br /> C.9(15GI[Y or 4L'¢Itr5112&A VY1'/1P <br /> Install cl untrnlizrd -—.— CapaCIN e(deoantra"Ited VeWtPs <br /> capacity <br /> Time <br /> Figure 6.Typical treatment plant expansion timeline. <br /> 0&M costs for STEP/STEG systems are almost fully attributed to the on-site pump and tank and the treatment. <br /> Since both the on-site system and the treatment capacity(as illustrated in Figure 6) can easily be deferred to the <br /> time of connection, the concept of mandatory connection can be revisited. We would suggest that connections <br /> be prioritized to failing and aging septic systems first while newer system be allowed to remain in service <br /> provides that they are regularly inspected. <br /> 4 70-80%of the collection system capital costs are associated with the on-lot components <br /> o On-lot components are not installed until the connection is made <br /> 4 20-30% of the collection system capital costs are associated with the main lines <br />