R2026-125 Resolution Authorizing Agreement with INTERA Incorporated to Provide Professional Engineering Services to the City of Decatur for the Alternate Water Supplies Update, City Project 2024-05

Home Browse Search

update the triple-bottom-line analysis of water supply options, 4) provide updated recommendations on the timing of investments in those projects, and 5) apply decisions made during a May 2026 table-top drought exercise to guide the City on the amount and timing of demand cutbacks and alternative supply triggers. Scope of Work To achieve these objectives, the following tasks will be performed: 1. DEMAND PROJECTION SCENARIOS INTERA will review and finalize with City staff the timing and quantity of selected demand projections including potable and non-potable water demands. Rather than attributing future demand to specific industrial/commercial proposals, incremental demands of, for example, 5, 7, and 10 MGD, will be assessed. In this task, we will also review and finalize with City staff, a master list of possible supply alternatives and set aside alternatives no longer considered desirable. The number of supply alternatives to assess will be constrained to include: • Excavation of the former Vulcan Pit(water mine) • Vulcan Harristown gravel pit including excavation • Extended/expanded use of the Mahomet Aquifer • Sanitary District of Decatur(SDD) wellfield • Lake Tokorozawa with a direct lake intake or wells on adjoining SDD property • Continued use of the Cisco well 2. DEMAND SCENARIO MODELING INTERA will update the GOLDSIMTM model developed for the 2019 study, including new lake bathymetry, to refine the relationship between lake stage and storage volume. We will run the model with new water demand scenarios identified in Task 1 under the Design Drought condition established for the 2019 study.These modelled demand scenarios will provide a set of supply gaps that form the basis for assessing supply options. 3. SUPPLY OPTION ANALYSIS In this task, INTERA will screen the list of supply alternatives identified in Task 1 to those that are technically feasible and have the potential to meaningfully address the supply gaps identified above. We will provide clear reasons to exclude those alternatives that do not bear further investigation. The remaining existing and new supply options will be assessed to a comparable level of detail as was done in Section 6 Supplemental Sources of the 2019 report. This includes analyses of potential water supply quantities for each alternative. For new alternatives, 2 Last Revised:2/03/2022