Admin Order 58-12-14 - Laserfiche WebLink

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Most proposed flood control capital projects were identified to address problems predicted to occur by the model developed for the major system, for larger storm events, based upon assumed impervious surface area percentages. The City acknowledges that the assumed impervious surface area percentages used in the model are inherently slightly conservative, as they do not reflect assumptions about the degree to which impervious surface area will be reduces through incentives, however it is the City's, County's and consulting engineer's best professional judgment that slight conservatism is appropriate in the assessment of the major flood control elements of the system for purposes of identifying potential flooding problems and capital project needs. It is very important to realize, however, that during capital project design, in advance of any capital project construction, a more detailed storm drainage study is conducted which delineates the drainage areas, impervious areas, and runoff volumes to a greater level of detail than is done in the master planning process and would refine the size of flood control facilities. Justify why flood control standards do not pencil out compared to flood control capital projects for this basin. [SC -91, [RR -91 As with the other stormwater basins, most of the identified flooding problems in RR -SC were anticipated to occur as a result of existing developed conditions. While future development would exacerbate some of the problems, a capital project would already be required to address existing condition flooding. Implementing on -site storage requirements for new development would not address the majority of capacity - related problems as identified by the model. Require on -site storage and infiltration for all new development. [SC -41, [SC -91, [RR -21 As described above, the method for managing stormwater is not prescribed, but acceptable choices are provided in the Stormwater Management Manual. The appropriate destination method is site - specific and depends on a number of factors including soil type, slopes, and availability of public and private infrastructure. While on -site storage and infiltration is not explicitly required, certain circumstances prevalent in the RR -SC basin would in effect necessitate on -site retention /infiltration, for example: o Development sites in any area of the City where a public stormwater system does not exist and extension from the public system is not planned. Figure 4 -11 (Project Planning Phase) in the draft basin plan illustrates this situation, which reflects inherent constraints in some areas of the RR -SC basin (as well as other areas within the City, but less so) for piping stormwater off -site. The decision making process reflected in the figure conveys the City's strategy to allow for use of capacity where there is capacity in an existing piped system, and for connection to an existing piped system if it is feasible and there is capacity in the downstream receiving system. Given the RR -SC basin's inherent constraints (including discontinuous stormwater system, flat topography, mixed jurisdictional areas, RR -SC Stormwater Basin Plan Comments Pg.10 of 17