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SECTION 4 water Quality Eualuatiou term through re- development, and developed areas with high pollutant source land uses such as commercial and industrial uses. This effort included identifying areas with the following characteristics: 1) largely developed areas with little remaining vacant land; 2) densely developed high pollutant source areas; 3) sufficient space available for a surface water quality facility; 4) the space that was available is publicly owned or vacant and potentially available for purchase; and 5) the location could potentially be used to construct a CP that addresses objectives in addition to water quality control (i.e., flood control, natural resources enhancement, recreation, education). Given the differences in the River Road Santa Clara basin when compared to the other basins (i.e., the mix of County /City jurisdiction and the significant presence of drywells), the identification of water quality CPs was conducted somewhat differently from the previous basins. The development of water quality CPs was predominantly focused on water quality projects that could be implemented to deal with increases in runoff and pollutant loads associated with the decommissioning of public drywells. Approximately 151 public drywells (79 County and 72 City) will need to be decommissioned to comply with DEQ's UIC rules. Decommissioning of the drywells is expected to be a significant undertaking. Therefore CPs were developed to address the water quality objectives in parallel with the decommissioning effort, especially since the potential decommissioning of public drywells could result in a significant increase in pollutant loads to the surface water system (see Figure 4 -2). These proposed CPs are described below under "Water Quality CPs Associated with UIC Decommissioning." Additional water quality CPs were also developed to specifically target high pollutant source areas and stream stability problems that were described in Subsection 4.2 above. These proposed CPs are described below under "Other Water Quality CPs." Water Quality CPs Associated with UIC Decommissioning As described in Section 3.0, drywells located in close proximity to each other were grouped into drywell "clusters ". This grouping of drywells was conducted because some of the decommissioning options could be applied and constructed in a manner to address a "cluster ", as opposed to individual drywells. A total of 39 drywell clusters were identified. The drywell clusters are illustrated on the Stormwater Management Strategy Development map in Appendix H, and listed in Table 3 -6, and the location of each of these clusters is also shown in Figures 3 -2 through 3 -8. As a result of the decommissioning of drywells, alternative systems will be necessary to handle the flows (up to the 5 -year, 24 hour design event) that are currently being handled through drywells. CP options were selected for each drywell cluster with the intent of maximizing water quality benefits while addressing increases in flows from a flood control and conveyance standpoint. As described in Section 3.0, three project options were developed to handle the flows from these drywell drainage areas: 1) construct pipes to handle flows and route them to the nearest storm piped system — provide structural pre- treatment as part of the pipe retrofit (Pipe and Pre -treat Option); 2) direct drainage to a neighborhood -scale surface infiltration /rain garden facility for storage and infiltration (Surface Infiltration/Rain Garden Option); or 3) construct on- street rain gardens to handle right -of -way drainage as local street improvements are made (On- Street Rain Garden Option for Local Streets). 0:\25695978 Eugene RR -SC Final Basin P1an\Master P1anTINAL 2- 2010\Master_Plan 3- 11- 10_FINAL_ Word _Version.doc 4 -8