Memorandum <br />Page 2 of 2 <br />September 2, 2021 <br />lqjff <br />infiltration was explored by the design team but was deemed infeasible, due to the presence of season-high <br />groundwater. Several options for vegetated treatment were studies through the development site. Due to <br />the limited space for a vegetated treatment facility and the nature of the use surrounding the practice facility, <br />vegetated treatment was not possible. Mechanical treatment will be used to treat all drainage from the <br />proposed development area. As stated above, a water quality manhole will be utilized to treat all incoming <br />runoff from the site. <br />Flood Control <br />The destination of treated runoff leaving the site is a 42-inch public storm main located in Leo Harris Pkwy. <br />The stormwater main flows east and outfalls into the Q Street Channel. The City of Eugene Stormwater <br />Master Plan lists no capacity concerns for the 42-inch storm main. Therefore, per flood control standards, <br />no detention or retention of stormwater will be required. <br />Flow Control <br />The proposed site is not above 500 feet, and there are no capacity issues with the public storm system, so <br />flow control requirements do not apply. <br />Source Control & Oil Control <br />The proposed project does not include any facilities that are highly likely to generate pollutants that cannot <br />be addressed through mechanical treatment, so source control is not required. Similarly, the project does <br />not include the construction of any large parking lots or vehicle storage, so oil control requirements do not <br />apply. <br />COPIES: <br />Colin McArthur, Cameron McCarthy, cmcarthur@cameronmccarthy.com <br />Laura Sinn, Olson Kundig, lauras@olsonkundig.com <br />2100102- sb <br />