l of/~ f i3 <br />1 t...~ x. <br />i <br />October 15, 2013 <br />- <br />SSW Job # 13-7076 <br />SSW <br />Willard C. Dixon, AIA 300 Blair Blvd <br />HOURS.' <br />Eugene, OR 97402-4150 <br />CML-SIRUCTLTA- BUICDUIGDESIGA <br />SURVEYING ^ UAND USE PLANNING <br />2350 Oakmont Way, Suite 105 <br />Eugene, OR 97401 <br />Attention: Willard C. Dixon AIA <br />(541) 485- <br />Fax (541) 485-8384 <br />8383 <br />www.ss sswengineers.com <br />Re: Oakleigh Meadow Cohousing (P-DT13-0001) <br />The following is in response to the public comment concerning stormwater at the proposed <br />Oakleigh Meadow Cohousing. We appreciate the concern in regards to the quantity of runoff <br />from the site, treatment of pollutants and the destination of the stormwater. Unfortunately, the <br />information from the public comments is in error. Calculations indicating the quantity, treatment, <br />and flow were submitted to the city and were available to the public as of 7/30/13 through the City <br />of Eugene's website. Furthermore, the calculations presented assume that some of the <br />stormwater runoff needs to be retained for a full month's accumulation of water. This is not a <br />requirement of the city code or the 2008 Eugene Stormwater Manual. However, runoff flows for <br />storm events are reduced to predevelopment flows.through.the means of oversizing the treatment <br />facilities and detention. <br />The design of the site has taken account for the items listed in EC9.8320 (9), and EC9.6791 <br />through EC9.6797, specifically stormwater destination, stormwater pollution reduction, and <br />stormwater flow control. The site and all the stormwater facilities were designed in accordance <br />with the 2008 Eugene Stormwater Manual. <br />Since infiltration is unadvisable and there is no existing stormwater system available, destination <br />of the stormwater from the site, after treatment, will be along the east side of the property and will <br />sheet drain on to the adjacent city property. Flow from the site is reduced to pre development <br />flow and is dispersed using rip rap. This destination was agreed upon in a meeting on January <br />30th, 2b13 by Neil Bjorklund with the city's Public Works department. <br />Treatment of the stormwater from the site conforms to the treatment options listed in the 2008 <br />Eugene Stormwater Manual and consists of pervious pavements, 15 rain gardens, and a <br />vegetated swale. Pervious pavement will be located in the parking stalls, the entry and the fire <br />turnaround. <br />Site walking surfaces and the roof tops of the homes will utilize the 15 rain gardens around the <br />site. Each rain garden is sized to treat and reduce flows to predevelopment rates. Sizing of the <br />rain garden was performed by using the City of Eugene's "Stormwater Surface <br />Filtration/Infiltration Facility Sizing Spreadsheet. <br />Page 1 of 2 Oakleigh Meadows Cohousing <br />576 <br />