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10%. Overall ISC was not included in Figure 1 in order to retain a meaningful y-axis scale for the <br />individual zone ISC acreage. <br />Figure 1. Acres of Potentially Regulated Land & <br />Impennous Surface Comer by Management Zone for <br />Water Quality Protected Waterways <br />1000 <br />800 <br />600 519 ®Acres <br />400 ®ISC <br />200 8 ' 04 <br />0 <br />Channel 0-25 ft 26-50 ft 51-75 ft <br />zone zone zone <br />IV. OPTIONS <br />Taking into account the evaluation results, options for proceeding include: <br />Option 1. Apply a "standard setback" to all water quality waterways (i.e. those that meet the water <br />quality protected criteria: 303(d) waterway, or direct tributary to a 303(d) waterway, or headwater. <br />stream, but not roadside ditches) regardless of level of impact in terms of ISC; or <br />Option 2. Apply a "standard setback" to all water quality waterways that do not exceed the ISC <br />thresholds for all management zones, and, utilize the parcel/corridor impact evaluation to <br />.eliminate from "protect" status those waterways that exceed the ISC thresholds for one or more <br />management zones; or <br />Option 3. Apply a "standard setback" to all water quality waterways that do not exceed the ISC <br />thresholds for all management zones, and, utilize the parcel/corridor impact evaluation to refine <br />buffer widths for waterways that exceed the ISC thresholds for one of more management zones. <br />These three options are further described below. Note that for all options, the SWMT recommends <br />removing the Highway 99 roadside channel and all of its direct tributaries. <br />Option 1 -Standard Setback to All Water Quality Waterways <br />This option would apply a standard buffer (75-ft each side, measured from centerline or top-of--bank as <br />described in Section III -Evaluation Process) to a1185.3 milesl of waterways that meet the water quality <br />protection criteria: 303(d) waterway, or direct tributary to a 303(d) waterway, or headwater stream <br />regardless of level of impact in terms of ISC. All existing development as represented by impervious <br />surfaces as of the adoption date of the ordinance would be exempted through provisions in the ordinance. <br />This would likely be the most defensible approach to take (e.g. avoids the customization-approach of <br />Option #3 which then could open up challenges to the customized buffer widths) and it reduces <br />implementation complexities. This option also avoids the perception that exempting mostly publicly <br />owned or managed waterways from protection due to large .amounts of contiguous impervious surface <br />areas in the form of waterside streets (Option #2). It also is the most protective of water quality (of the <br />1 Total number of water quality waterways, updated to reflect removal of Highway 99 and it tribs, and waterways <500 ft long. <br />3/28/06 (Page 8 updated 4/4/06) <br />