Admin Order 58-12-14 - Laserfiche WebLink

Home Browse Search

beneficial to confirm capacity issues on the major system. Therefore, installation of a flow meter in the Basin has been added to the capital project list. The capacity - related capital projects resulting from the modeling will be added to the City's long -term stormwater capital improvement needs. The City's project list (including all stormwater project needs, city -wide) is significantly larger than the budget available, and by necessity a prioritization process is used to identify the highest priority projects for implementation. Prioritization criteria include whether a flooding problem is observed vs. predicted by modeling, which is where the large stormwater projects referred to in the comment would not rise to the top in the foreseeable future. Flow data and model refinement will realistically precede implementation of these capital projects. In effect, these projects are placeholders for potential capital investment in the future to maintain system capacity, and are based upon the best available information and professional engineering judgment. Individual stormwater facility capital projects will be assessed using additional data prior to final design and construction to ensure proper sizing. The County does not currently have funding for stormwater related capital projects. As the County develops funding for such projects, prioritization will be assigned in a manner similar. With respect to the extent of the model, basin planning stormwater models were generally limited due to budget and resource constraints to the larger system (pipes 36- inches and larger, and larger waterways), generally inside city limits. The RR -SC basin plan model goes beyond the modeling in other basins in that it extends, for the most part, through the mix of jurisdictional areas to the urban growth boundary. The Willamette Overflow downstream from node 72088 was not included in the model because most of it is on the edge of the UGB, with some located outside the UGB, and is located downstream from subbasin WO -000 which lies entirely outside of the UGB. It appears redundant to create capacity with facilities to replace drywells and construct large flood control capital projects. [SC -81 The City's Stormwater Development Standards require stormwater systems (pipes or drywells) serving less than 40 acres to be designed for a 5 -year storm. Open channel systems serving less than 40 acres and all systems serving 40 acres up to 640 acres must be designed for a 10 -year storm, except for culverts and bridges for arterial streets which must be designed for a 25 -year storm. The modeling for future (build -out) conditions reflects that the existing drywells do not manage a volume of runoff significant enough to affect capacity needs of the major system. In other words, whether under existing conditions or future buildout conditions, the existing public drywells do not have a significant effect on the major system conveyance needs. The decommissioning of drywells is not driving the capacity - related capital projects. What is driving the capacity related projects is a set of constraints on the major system (for example, on the RR -SC Stormwater Basin Plan Comments Pg.15 of 17