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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 /> Impervious SurFace Cover by Management Zone for <br /> Water Quality Protected Waterways <br /> 1000 g------ <br /> 800 <br /> 600 519 ~ Acres <br /> 400 ISC <br /> 200 ~ 5 ~3- 91 04 <br /> 0 - - <br /> Channel 0-25 ft 26-50 ft 51-75 ft <br /> zone zone zone <br /> <br /> ~ 6 <br /> <br /> i <br /> <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 parceUcorridor 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 Ouality 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 all 85.3 milesl of waterways that meet the water quality <br /> protection criteria: 303(d) waterway, or direct tributaryto 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 5 <br /> _ <br /> <br />