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R -9.4770-C Water Quality Waterways Map — Mapping Procedures. Pursuant to <br />EC 9.4786(2) and EC 9.4778(1), approval of an application to correct the Water Quality <br />Waterways Map must be based, in part, on consideration of the procedures the City used for <br />mapping the setback areas on that Map. This Section sets out those procedures. All mapping <br />relates to conditions in place on March 9, 2009, the date the City Council approved Ordinance <br />20430. <br />1. Waterway Location. The location of each water quality waterway depicted on <br />the adopted Water Quality Waterways Map ("the Map") was initially determined <br />based on the City of Eugene's open waterways data file referred to as "DOPEN" <br />and verified, with any necessary modifications, through aerial photography and <br />field visits where access was granted by property owners. <br />2. Map Setback Measurement Point by Waterway Category: <br />2.1. Tributary to 3 03(d) waterway. As provided at EC 9.4778(1)(b), the <br />setback for tributaries to 303(d) waterways was measured from the <br />waterway's top of high bank (THB). THB was identified at the highest <br />point at which the vertical rise of the waterway bank met the horizontal <br />grade of the adjoining topography. THB location was identified and <br />digitized into a Geographic Information System (GIS) shape file using a <br />combination of the City's DOPEN file, 2004 aerial photography, and 2 <br />foot contour elevations. The location of the setback measurement point <br />was identified on the adopted Water Quality Waterways Map. <br />2.2. Headwater stream. As provided at EC 9.4778(1)(c), the setback for <br />headwater streams was measured from the stream's centerline. The <br />location of stream centerline was based on the City of Eugene's DOPEN <br />file. <br />3. Map Setback Area by Waterway Catel4ory: <br />3.1. Tributary to 303(d) waterway. Based on the location of the setback <br />measurement point and per EC 9.4778(1)(b), 25 foot setback areas were <br />identified on the Water Quality Waterways Map extending landward from <br />the THB on each side of the waterway's channel, forming GIS polygons. <br />These setback area polygons constitute a portion of the overall water <br />quality management area mapped for tributaries to 303(d) waterways <br />included on the adopted Water Quality Waterways Map. The other <br />component of the Water Quality Management Area for tributaries to <br />303(d) waterways is the waterway's channel which, pursuant to EC <br />9.4778(1)(a), is that area located between the THB on each side of the <br />waterway. This channel area was identified by creating a GIS polygon <br />that connects and encloses the area between the two THBs and was also <br />depicted on the adopted Water Quality Waterways Map. <br />Administrative Order - Page 5 of 12 <br />