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three options) in that it protects what remains of the waterways/setback areas that drain to water quality impaired waterways, even though some of them maybe quite impacted with impervious surfaces. Option 2 -Combination of Standard Setback and Removal of Some Waterways from "Protect" Status This option would apply a standard setback to all water quality waterways that do not exceed the ISC thresholds for all management zones, and, utilize the parcel/corridor impact evaluation to eliminate .from "protect" status those waterways that exceed the ISC thresholds for one or more management zones. In other words, waterways that do not meet the threshold criteria of impervious surface area within all three management zones (up to 10% ISC streamside zone; up to 25%ISC middle zone; up to 40%ISC outer zone) would be deemed too impacted to have adequate water quality function to warrant protection. This approach involves not only looking at individual waterways, but also at the corridor as a whole, to evaluate existing ISC against the threshold criteria. The result would be that a standard setback would be applied to Amazon Main Stem for instance, but that the Roosevelt Channel, the north Beltline Floodway,. Debrick Slough (including Delta Ponds), and the west Beltline floodway would be taken out of the "water quality protect" designation and no protections would be applied. With this option, 60.5 of the 85.3 (71 %) water quality waterways would be protected. While this approach acknowledges the presence of significantly impacted areas and becomes the basis for no protection, it does not account. for the presence of water quality function within waterways that have earthen bottom with side-slope vegetation -even at high levels of impact -and the role they play in helping to address TMDLs on a system-wide basis. Option 3 -Combination of Standard Setback and Customization of Buffer Widths for Some Waterways This option would apply a "standard setback" to all water quality waterways that do not exceed the ISC thresholds for all management zones, and, utilize the parcel/corridor impact evaluation to refine buffer widths for waterways that exceed the ISC thresholds. In other words; for waterways that exceed the threshold criteria of impervious surface area within one or more of the three management zones (10%ISC streamside zone; 25%ISC middle zone; 40%ISC outer zone), aerial photos and the GIS tool would be used to determine more specifically the location, nature and concentration of the impervious surface area. This "look-back" included a review of the "Total ISC" data to determine if the percent impervious surface cover of the overall waterway corridor was below the 25% threshold. Results from this closer evaluation would be used to customize the buffer widths to something that recognizes existing impacts up-front. For example, where we know there are significant impacts due to adjacent roadways (e.g. Upper Amazon between East and West Amazon Drive, Roosevelt Channel, west Beltline Floodway, etc), reduce the buffer to something more in-line with where the impervious surface area currently starts (e.g. 25 feet, 50 feet). Using this approach all of the 85.3 miles of water quality waterways would be protected, with varying degrees of protection for 24.8 miles of the waterways. Stormwater Management Team Recommended Option The SWMT recommends, by unanimous consensus, proceeding with Option 1: apply a standard 75 foot setback to all water quality waterways and exempt existing development through provisions in the ordinance. The team believes that Option 1 is the most defensible, the most reasonable, and is clear and simple. Option 2 was supported by a couple SMWT members as an alternative to Option 1, for its use of the parcel/corridor evaluation data and for its simplicity. Option 3 was the staff team's recommendation to the SWMT, however it was not very well supported given the "look back" and apparent subjectivity in customizing buffer widths. It was thought by the SWMT that Option 3 would leave the city open to challenge, and that it would be simpler to exempt existing development through ordinance provisions rather than customized buffer widths. 3/28/06 (Page 8 updated 4/4/06)