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REDWOOD CITY GREEN INFRASTRUCTURE PLAN Figure 7. Scenario 1: Map of GI capacities within each subwatershed of Redwood City (sediment target, with regional identified project). As can be seen in the above results, the cost -optimization favored implementation of different combinations of GI projects within each subwatershed. These combinations were based on: (1) number and type of GI project opportunities identified within each subwatershed, and (2) cost- effectiveness given various characteristics associated with GI control measure efficiency (typically governed by infiltration rates), higher sediment (or PCBs) generation in upstream areas, etc. During implementation, it is almost certain that the actual implementation of GI will not follow the RAA output exactly; however, the recipe provides "management metrics' by subwatershed (described below) to guide the adaptive management process. Dimensions and location of GI projects will vary based on on -the -ground feasibility and site-specific constraints. GI performance varies based on factors like the physical properties of the facility and upstream drainage area managed. For these reasons, it is not recommended that GI capacity serve as the focus for stormwater improvement goals for the GI Plan. The RAA recommends management metrics for the GI Plan that are based on metrics that can be easily measured and tracked throughout implementation. At the left side of the table in Table 2 are columns under the header "Management Metrics for GI," which include performance metrics for "% Load Reduction PCBs (Annual)," "Annual Volume Managed (acre -ft)," and "Impervious Area Treated (acres)." The "% Load Reduction PCBs (Annual)" and "Annual Volume Managed (acre -ft)" metrics are based on annualized results represented in the RAA modeling system that are directly comparable to TMDL WLAs. The "% Load Reduction PCBs (Annual)" provides a relative comparison of the load reduction to be achieved within each subwatershed. The "Annual Volume Managed (acre -ft)" shows the acre-feet of water captured and infiltrated and/or treated within each subwatershed, resulting in a total annual volume of 15.3 acre-feet of stormwater managed in Redwood City for an average year. This 15.3 acre-feet of stormwater managed could serve as the primary metric to be tracked for GI implementation. In other words, stormwater volume managed is being used as a unifying metric to evaluate GI effectiveness. 'Impervious Area Treated (acres)"is an additional metric suggested by the MRP for implementation tracking. As a result of adaptive management, the implementation plan may change over time and alternative RWC GREEN INFRASTRUCTURE PLAN 22 JUNE 2019 ATTY/RESO.0075/CC RESO APPROVING THE GREEN INFRASTRUCTURE PLAN — EXHIBIT A RESO. NO.15780 REV: 06-20-19 PR MUFF NO. 802