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Feasibility Study <br />Water Treatment Plant <br />City of Lino Lakes, MN <br />WSB Project No. 015822-000 Page 26 <br />8.2 Proposed Watermain Phasing <br />The water treatment plant capacity was incrementally increased from 5,000 gpm to 10,000 gpm <br />with the model in order to determine which segments of parallel trunk watermain(s) will be <br />needed at various phases as development progresses. The incremental plant capacities were <br />compared with the future water demand projections to determine approximately when the <br />watermain improvements are anticipated to be needed. The necessary trunk watermain <br />improvements corresponding with each phase, and the resulting hydraulic conditions in the <br />watermains in the vicinity of the potential plant site, are shown in Figure 7 in Appendix A and <br />summarized in Table 8-2. <br />Table 8-2. Proposed Watermain Phasing <br />Phase <br />WTP <br />Flow <br />(gpm)* <br />Approx. <br />Year**Watermain Description Watermain <br />Dimensions <br />Max. <br />Headloss <br />Gradient <br />(ft/1,000ft)*** <br />Max. <br />Velocity <br />(ft/s)**** <br />1 5,000 2021 <br />Upsize 6-inch to 12-inch in Black <br />Duck Dr from E Shadow Lake Dr to <br />Mallard Ln <br />575 LF (12”)5.1 5.0 <br />2 6,000 2030 <br />Parallel 16-inch WM in Birch St <br />from Black Duck Dr to White Oak Rd, <br />Upsize 6-inch to 12-inch in Black <br />Duck Dr from Birch St to Lantern Ln <br />and from Well No. 1 to E Shadow <br />Lake Dr <br />3,300 LF (16”) <br />1,475 LF (12”)5.1 5.0 <br />3 7,000 to <br />8,000 2040 <br />Parallel 16-inch WM in Birch St <br />from White Oak Rd to 20th Ave S, <br />Upsize 8-inch and 10-inch to 12-inch <br />in Black Duck Dr at Partridge Pl and <br />at Crystal Ct <br />11,500 LF (16”) <br />1,440 LF (12”)4.0 to 5.1 4.3 to <br />5.0 <br />4 9,000 to <br />10,000 <br />Post- <br />2040 <br />N/A – Velocities exceed 5 ft/s with <br />two parallel 16-inch trunk watermains N/A 7.6 to 8.8 6.1 to <br />6.6 <br />*System max day demands increased to necessitate WTP flow rate. <br />**Approximate year that the WTP capacity will need to be increased to meet maximum day demand, <br />based on a 20-hour supply period. <br />***AWWA M32 recommends a maximum headloss gradient of 10 ft per 1,000 ft. <br />****AWWA M32 recommends a maximum velocity of 5 ft/s. <br />As shown in Table 8-2, the maximum flow velocity is more constraining than the maximum <br />headloss gradient. The existing 16-inch trunk watermain reaches a velocity of 5 ft/s at a flow rate <br />of 3,150 gpm. Because the potential plant site is centrally located in the water distribution system, <br />a total flow rate of 6,000 gpm results in approximately 3,000 gpm flowing outward in either <br />direction in the 16-inch trunk watermain, which satisfies the velocity constraint. A plant capacity of <br />6,000 gpm only requires trunk watermain improvements in the immediate vicinity of the plant site. <br />However, increasing to 7,000 gpm (resulting in approx. 3,500 gpm flowing in each direction) will <br />require parallel trunk watermains alongside the existing 16-inch trunk watermains in Birch Street <br />as shown in Figure 7 in Appendix A. <br />Watermain phasing was also reviewed along Black Duck Drive north of Birch Street. The existing <br />watermains in Black Duck Drive include a mixture of 6-inch, 8-inch, 10-inch, and 12-inch diameter <br />watermains. A 12-inch trunk watermain has been installed in Aqua Lane to the northwest to <br />improve transmission to the northwest portion of the system, and the watermain in Black Duck <br />Drive should be upsized to 12-inch to complete a uniform, continuous loop. The phases at which <br />particular segments of this watermain need to be upsized to 12-inch diameter to meet the AWWA <br />recommended hydraulics are shown in Figure 7 in Appendix A. These improvements could also <br />be completed all at once in Phase 1.