2006 Water Comprehensive Plan - City of Bellevue

Storage Conclusions and RecommendationsBased on the storage analysis:• Storage volume is adequate in two of the three operating areas, for current and projected fireflow, equalizing, and standby requirements, through build-out.• In the West Bellevue operating area, calculated storage requirements are greater thanprovided by available storage reservoirs. This is projected to first occur in 2018. A total of2.35 MG of additional storage in the West Operating Area will be required to meet build-outconditions. Of this total, approximately 1 MG is needed by 2025. Therefore, adding 1 MGof storage by 2018, would preclude the need for additional storage until 2025.Construction of new storage could be located at existing reservoir sites in the WestOperating Area. Since there is time before the additional storage is needed, construction ofthe new storage could be paired with demolition of existing reservoirs as they age. Thedemolished reservoirs would then be replaced with larger reservoirs on the same site. Aplanning level cost estimate for design and construction of 2.35 MG of new storage isapproximately $5.2 million.• The total deficiency of 2.35 MG does not necessarily mean that new storage must or shouldbe constructed. Additional storage capacity could be made available to the West Bellevueoperating area from the East Bellevue operating area’s 5 MG of surplus storage.Two projects were identified that, if both were constructed, would provide the capacityneeded to transfer enough water from East Operating Area storage surplus to eliminate theWest Operating Area’s storage deficiency. Each project would construct new 12-inchdiameter pipe, a large PRV, and modify system valveing to improve the systems flowtransfer capacity. These two projects are generally located along NE 40 th Street between148 th and 132 nd Avenues, and along NE 8 th Street between 151 st and 132 nd Avenues. ThePRV’s would need to include controls that would automatically activate them in anemergency in order for the East Operating Area storage to be considered available in anemergency. The planning level cost estimates for these projects are approximately $2.1million and $1.5 million respectively.Use of the PRV stations and piping improvements instead of construction of new storagewill be beneficial for water quality, particularly chlorine residual concentrations. Bymoving more water from the storage-rich East Bellevue operating area to the storagedeficient West Bellevue operating area, water will reach the customer more quickly andthere will be less degradation of chlorine concentrations in the distribution system.• The choice of method to address the West Operating Area storage deficiency should befurther evaluated for cost and for the secondary benefits that can be derived from theconstruction, such as increased supply redundancy, water quality impacts of increasedstorage, the ability to respond to short-term emergencies such as fires, and the availability ofwater near the point of demand versus having to transfer water across the distribution system8-13