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updated annual average potable water demand projections for the 20 -year planning horizon to be used as the basis for determining the approximate size of the reservoir and corresponding WTP that would be required to meet future potable water demand. The demand will be based on existing future land use maps and corresponding population densities within the Urban Service Boundary. Consultant will rely on County staff to coordinate closely with the County's Metropolitan Planning Organization (MPO) representative to obtain the existing available information. Future phases and permitting activities will require additional development of population/demand projections to more closely mirror the medium BEBR and Shimberg Center population projections for the County (not included in the Phase 1 Scope of Services). The size of the reservoir will have to be confirmed in the subsequent phase (through modeling) and will only be approximated using the population/demand projections and an assumed unlimited surface water supply for the purpose of this Phase 1 feasibility study. As an open water body, a reservoir of this nature is subject to natural additions and losses such as rainfall, evaporation, and groundwater seepage. These contributing factors affect the size of a reservoir over and above the flows that are to be intentionally added via diversion from the surrounding drainage canals, and cannot be fully accounted for without detailed data review and modeling (not included in this phase). A simplified water balance approach using annual average conditions will be applied to determine sizing of up to two preliminary reservoir configurations. Limited data collection will be conducted in support of this effort. These data include stream flow records for proposed surface water supply sources (where available), along with rainfall and evaporation records for up to three nearby gages. Once the size of the required reservoir is approximated, Consultant will evaluate the following related to surface water withdrawals, storage and treatment: ■ Suitability of proposed site (proximity to existing WTP, distance from water sources, size of reservoir, etc.); ■ Property acquisition requirements [for both reservoir and pipeline rights-of-way (ROW)); ■ Permitting considerations, requirements and potential obstacles; ■ Environmental impacts, including Total Maximum Daily Load implications and availability of credits; ■ Potential surface water sources to supply the reservoir (including coordination with the local drainage district)1; ■ Reservoir sizing for utility purposes alone vs. utility and agricultural use (with agricultural needs/demands to be provided by representatives from the agricultural community rather than being developed by Consultant); ■ Consideration of drought conditions/impacts (how drought conditions will affect Tong -term operations during dry periods; quantification of available flows under drought conditions will not be provided in Phase 1); ■ Pre-treatment and treatment considerations; ■ Constructability review; and ■ Conceptual capital cost estimates (including land acquisition, reservoir construction, transmission piping construction, range of anticipated costs for surface water treatment plant2, pumping, engineering/design and O&M costs3). 'The volume and timing of surface water available for withdrawal/diversion to the proposed reservoir project cannot be quantified without detailed basin/watershed and reservoir system modeling (not included in this Scope of Services). Modeling will be performed in a subsequent authorization, if the feasibility study suggests that the property is suitable for such a project. 2Consultant will rely on past experience with surface water treatment plants to approximate a range of anticipated cost per gallon of capacity to construct the treatment facility. Accurate A-5 j11429REV5 (2).doc docx 107