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I I I I I I I I I I I I I I I I I I I . Construction of detention ponds · Installation, removal or replacement of ~tructures at specific problem areas · Improvement or enlargement of major drainage channels . Acquisition of property/structures within specific flooding areas and relocation of homeowners and! or businesses · Floodproof structures in specific flooding areas · Construction of berms and spill structures to contain additional stormwater captured by the irrigation canals/ditches and control the release of excess stormwater As previously indicated, approximately 89 percent of the Godding Hollow Basin and 75 percent of the Tri- T own Basin are presently undeveloped and largely consist of agricultural lands . Along the major drainageways in both Godding Hollow and Tri-Town Basins, flooding problems are predominantly associated with road crossings, limited channel capacity, and lack of on-site detention in developed areas. Due to the nature of the flooding problems and the largely undeveloped basins, this master planning effort focused on providing alternatives that would significantly reduce the peak discharge in the major drainageways. Flooding problems are created at several of the road crossings along Godding Hollow and the Tri-Town drainageways which do not adequately convey the 100-year flood event without overtopping the roadway. Currently, the jurisdiction for improving the structures rests w1th either the county or state highway officials. Given that these structures are located within the urban growth boundary, however, this master planning effort assumed replacement of the structures as development occurs within the basin. Furthermore, replacement of these structures assumes the stormwater runoff is conveyed to these locations. The actual limits of the floodplain were not determined during this study; consequently, channel improvements may ultimately be necessary to ensure that these stormwater flows are conveyed to the location of the crossing structures. Several of the existing detention ponds behind roadway and railroad embankments do not meet existing drainage criteria. Nevertheless, these ponds play an important role in reducing the . 100-year peak discharge in the subbasins in which they are located. This master planning effort assumed that these ponds will remain intact or will be replaced/incorporated into future detention requirements associated with development within each basin. , The general approach taken to provide solutions to the drainage problems within the Godding Hollow and Tri- Town Basins consisted of the major types of improvements as indicated below. T:\OPEMCoweldOl\coweldOJ Inl rptwpd 5.2 SeptemberS, 1999