Item 9: Ordinance Concerning Stormwater Development Standards

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ATTACHMENT B Staff Responses to City Council and Public Testimony Comments and questions from the May 8, 2006, City Council public hearing and written comments received through May 22, 2006, fell roughly into six categories. The six categories are as follows: 1) the impervious surface area threshold; 2) applicability of the ordinance to infill type development; 3) applicability of the ordinance to subdivisions implementing an approved PUD; 4) clarification of the relationship between the River Road – Santa Clara Basin Plan and the Stormwater Development Standards; 5) preservation of the natural drainage system; and 6) design and construction of stormwater management facilities including the promotion of rainwater harvesting. Staff responses are provided herein for each category of comments. 1.Explain the justification for the 3,000 square foot impervious surface area threshold. Reduce the threshold. : Staff Response A number of citizens testified requesting that the Council reduce the impervious surface threshold for applicability to a level in-line with Gresham (2,500 square feet ) or Portland (500 square feet) for example. While all new areas of impervious surface have some impact on stormwater quality and the volume of stormwater runoff, a threshold of 3,000 square feet of impervious surface area is recommended for applicability of the proposed standards in order to balance pollution reduction with other considerations. Of the jurisdictions surveyed using this stormwater management approach, the threshold size of total impervious surface area ranged widely, from 500 square feet to 9,000 square feet. The lower end of this range, 500 square feet, would potentially be the most effective, but could result in many small stormwater management facilities and significantly more cost to the City because of the increase in permitting, administration, inspection, maintenance and enforcement. The upper end of this range (9,000 square feet) would likely be much less effective since it would exempt significantly larger areas of new impervious surfaces. The 3,000 square foot threshold was unanimously recommended by the Public Works Stormwater Department Advisory Committee in June 2000. Once an application is subject to the standards, all of the impervious surface area must be addressed by an approved facility ( not just the amount of impervious surface i.e. area in excess of 3,000 square feet). It is expected that decreasing the threshold below 3,000 square feet would not significantly increase the overall effectiveness