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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Care has to be taken if such large storage capac i ty is provi ded at thi s time. <br />With such a large stored volume and a small early usage, stagnation will <br />occur. This can be remedied by selecting a mode of operation in the early <br />years of only partially filling the tanks. As the water demands expand in <br />time, the levels can be raised in accordance with higher use rates. <br /> <br />It is concluded that either a two-or three-pressure zone system could <br />simu1 taneously provi de adequate di stri buti on and fi re-f1 ow storage. Storage <br />for a two-zone system with 1,150,000 gallons would be marginal for emergency <br />pipeline downtime, while a three-zone system that used the on-site 1,000,000 <br />gallon tank would provide a total of 2,150,000 gallons and allow a longer <br />outage on the main line. <br /> <br />3.3.3 Pipeline Hydraulics and Pipe Size <br /> <br />The remaining factor that determines pipe size for the 2.5 and 3.0 cfs ran'll'! <br />of design flow examined is the total head available. The Cortez treated water <br />tank fluctuates in water surface from elevation 6387.7 when empty to elevation <br />5407.7 when full. In our hydraulic analysis we have assumed all tanks to be <br />one-half full. Under the one-half full assumption, the two existing tanks in <br />Towaoc have predetermined water surface elevations. A third tank yet to be <br />constructed could be located at, above, or below the other tanks. The Tribal <br />P1 anni ng Oepartment has proposed that housi ng expansi on be di rected to the <br />north of Towaoc which would require water delivery to areas higher in <br />e1 evati on than the exi sti ng tanks. A new tank hi gher up the hi 11 from the <br />present tanks cou1 d be provi ded and separate pressure zones for each tank <br />could be established. <br /> <br />The effects on the system of having three pressure zones each served by a <br />separate tank is addressed in Chapter 4. O. For the purpose of exami ni ng the <br />pipeline system hydraulics we have assumed the new tank would eventually be <br />built at a higher elevation, with a water surface elevation range of 6230 to <br />6250, with a half-full elevation of 6240. <br /> <br />3-11 <br /> <br />l050c <br />