3.1 Phase 1: Slate Creek Watershed – Hydrologic and Hydraulic Study To support this hydraulic study, the County has performed preliminary analysis of the Slate Creek watershed and the town of El Dorado drainage conditions. This information includes: preliminary site surveying of the watershed, topography, and drainage patterns, evaluation of existing flow rates and Slate Creek hydraulics, and preliminary alternatives analysis and approximate recommendations. This preliminary information can be found using the hyperlink here: El Dorado Drainage Phase 1 focuses on the Upper Slate Creek watershed and begins at the upper reaches (north of Pleasant Valley Road); it ends approximately three hundred feet (300 ft) downstream of the El Dorado Irrigation District (“EID”) wastewater pump station facility or at a downstream distance far enough to consider and capture the effects to the EID facility associated with alternative recommendations. In this phase, the successful Proposer shall: a) identify the existing drainage patterns within the Slate Creek watershed that contribute to the flooding conditions, b) evaluate alternatives and recommendations to mitigate these conditions, and c) develop cost estimates for the proposed improvements. Recommendations associated with the Phase 1 analysis should consider downstream effects downstream of the EID facility on South Street. Alternative recommendations for the Phase 1 analysis may involve division or staging of solutions to accomplish over a period of years. The Hydrologic and Hydraulic Study shall include: o Development and calibration of the hydrologic and hydraulic model; o Evaluation of alternatives to address drainage issues; o Preliminary cost estimates for improvements; o Assess climate change impacts that may result in increases flow and duration of storm events that may not be captured in the existing County Drainage Manual; and o Include integration of green infrastructure where possible. o Final alternative recommendations; o Preliminary alternative cost estimates; and o Identification of other constraints (i.e. right-of-way impacts, environmental considerations). 3.2 Phase 2: Town of El Dorado and Pleasant Valley Road – Hydraulic Study Based on preliminary analysis of the existing drainage features within Pleasant Valley Road and the town of El Dorado, it is understood that backwaters from Slate Creek hydraulics have a direct effect on the flooding within the roadway infrastructure. It is also understood that the existing drainage infrastructure is aged and compromised in areas with very little cover beneath the roadway and constrained by the shallow creek channel elevations and flat ground. Phase 2 focuses on the existing drainage infrastructure within Pleasant Valley Road and the town of El Dorado. While Phase 2 is also predominately within the Slate Creek Watershed, the successful Proposer shall concentrate upon the existing drainage infrastructure within the County right-of-way and flooding locations within the public infrastructure. In this phase, the successful Proposer shall: a) evaluate existing drainage conditions, and b) provide alternative recommendations for the drainage systems to improve performance and management of flooding conditions within the town and public/County right-of-way. While there is an overlap in performance and recommendations between both Phase 1 and Phase 2, it is anticipated that the Phase 2 improvements will occur in advance of Phase 1; Phase 2 is also currently partially funded for construction. It is intended that Phase 2 will serve as a Basis for Design of the Pleasant Valley Road and town of El Dorado drainage improvements. The Phase 2 Hydraulic Study shall include: o Existing conditions, and o Preliminary alternative recommendations. o Final alternative recommendations; o Preliminary alternative cost estimates; and o Identification of other constraints and considerations (i.e. right-ofway impacts, environmental considerations).
