Capital Hill PUD: PDT 17-01 Page 4 of 5 <br />Completeness Review Response <br />August 22, 2017 <br />All pervious pavement has been removed from the project. See attached Storm water Plan <br />Sheet C2. <br />• How are flood control standards being addressed for the individual lots? Specifically the lots <br />that are east of the private street and drain away from the street (Lots 5, 7-18). Where will <br />the run off go in large events. <br />The PUD application is an application for approval of lots, not structures. There is no <br />practical way to address stormwater management requirements in any specific manner. <br />More than likely these lots will employ level spreaders that release water into the forested <br />area at pre-development flows. See note on Stormwater Plan that "All individual lots will <br />need to address water quality and flow control requirements when applying for building <br />permits" <br />• Flood and flow control standards require consideration for ALL impervious area, including <br />future buildings, driveways, and other impervious areas. According to Table 2 in the <br />Stormwater Management Plan, they aren't including the runoff from the buildings when <br />determining peak discharge rates. What happens in a large event? Will the proposed <br />mechanical System have adequate capacity to handle runoff from the additional impervious <br />surfaces on the individual lots? <br />This question has been posed quite often by public works staff at time of land use <br />application submittal. Many times, but not consistently staff has agreed that this point in the <br />process is not an appropriate time to be proposing specific stormwater solutions as there are <br />no proposed impervious surfaces on site. The appropriate time to ask this question and to <br />provide site specific solutions is at the time of building permit. <br />Otherwise we are making up solutions for conditions that don't exist or don't exist in the <br />manner in which we are imagining them. It becomes a guessing game and an unnecessary <br />addition to client and development costs. <br />Individual Lot Runoff <br />The individual lots will need to meet water quality and flow control requirements when <br />submitting for building permits and are not addressed by the improvements proposed above. <br />Possible water quality mechanisms for the private lots would be the use of mechanical <br />treatment or perhaps lined planters, rain gardens, sand filters, or swales. For flow control, <br />some of the mechanisms above might work, but the use of underground storage tanks or <br />oversized pipes may serve better. <br />For the lots bound by the new roadway improvements, upon treatment and flow control, <br />drainage disposal will discharge onto the new roadways. For the lots draining away from the <br />roadway to the east, disposal (after treatment and detention) would be into level spreaders <br />directed toward the existing park land to the east or north. <br />• The applicant has not adequately addressed the destination requirements, particularly with <br />respect to Capital Drive. As of now, it appears as though they will be collecting surface <br />runoff, concentrating it, and directing it away from their property, which isn't acceptable. <br />Where will this water go once it leaves the site? Are their ditches or a public system in the <br />area? They must display that the downstream system has capacity to handle concentrated <br />flow. Bubbler systems are no longer accepted in the City. <br />Flows will not exceed predevelopment flows. See revised Stormwater Report and <br />Storm water Analysis Report. <br />Schirmer Satre Group • 375 West 4 m Avenue, Suite 201, Eugene, OR 97401 • (541) 686-4540 <br />