Ordinance 2909-06 - Laserfiche WebLink

reduce the standard stream buffer width only when there has previously been substantial legal alteration of the stream and/or buffer on the subject lot or adjoining lots resulting in the existing buffer being unvegetated, sparsely vegetated, or vegetated with non-native invasive species and when buffer enhancement is provided per the following critieria. Where buffer reduction with enhancement is permitted by this chapter, it shall be limited to portions of buffers that have minimal functions due to prior legal alteration. 1. The planning director shall only allow a buffer width reduction when the proposal includes a stream and buffer enhancement plan that improves the functions of the buffer and the stream. An enhanced buffer shall not result in more than a fifty percent reduction in the standard buffer width for buffers that are unvegetated, sparsely vegetated, or vegetated with invasive species; and the reduced buffer shall not be less than the minimum dimension allowed by buffer width averaging. 2. A mitigation / enhancement plan shall be prepared per Section 18(E) [37.180(E)] of this chapter. The plan shall include a comparative analysis of buffer functions prior to and after enhancement, and demonstrate, as part of a critical area report, that proposed buffer enhancement, together with proposed buffer width reduction, will result in an increase in the buffer and stream functions when compared with the function of the standard buffer. At a minimum, the report shall address soils, slopes, existing and proposed vegetation, temporary irrigation, maintenance, monitoring and contingency. 3. If a limited portion of the buffer has been previously legally altered and meets the criteria, in this section, a buffer width reduction may be approved for that portion of the required buffer only. 4. The following criteria shall be used to determine when a required buffer is degraded and substantial legal alterations are present: a. The required buffer area has been graded or substantially altered and has not been substantially revegetated (i.e. the buffer is covered with gravel, impervious surface, mowed lawn, or is vegetated with primarily invasive species such as reed canary grass, Himalayan blackberry, purple loosestrife, or other non-native invasive species covering more than 75% of the buffer area). b. Substantial clearing of the buffer was authorized and substantial revegetation with native species has not occurred. c. A buffer that has been logged in the past but that has revegetated with an overstory of willow, cottonwood, alder, evergreen, or mixed evergreen/deciduous overstory, and an understory shrub layer of non invasive species does not constitute substantial alteration. D. Riparian Wetland. Any stream adjoined by a riparian wetland shall have the buffer which applies to the wetland, unless the stream buffer requirement is more protective, in which case the stream buffer requirement shall apply. E. Standard Buffer Width Averaging. The city may allow buffer width averaging, provided that the total area on the lot contained within the averaged buffer is not less than that 42