Public Comment (8) - Laserfiche WebLink

Reduction and EC 9.6793 Stormwater Flow Control (Headwat ~IEA lot owner will be responsible for maintaining its stormwater management system consistent with EC 9.6797 Stormwater Operation and Maintenance." ® During the PEPI permit process, the public stormwater system shall include City-approved proprietary stormwater treatment technology that meets the requirements of EC 9.6792 Stormwater Pollution Reduction and EC 9.6793 Stormwater Flow Control (Headwaters). The applicant's August 22, 2012 testimony accepts these conditions of approval and states that the applicant will comply with them (the conditions are listed as #16 and 17 at the end of this Final Order). The above statement that "EC 9.6790(2) requires that post-development peak flows will not exceed existing pre-development flow" is inaccurate. The stormwater development standards at EC 9.6791 through EC 9.6797 do not require this detention - of the western portion of the site. The reference here is actually EC 9.6793 Stormwater Flow Control (Headwaters), but this code provision would not apply to the development proposed on the western portion of the site because the outfall to an open conveyance system occurs below an elevation of 500 feet. In other words, the criterion at EC 9.8325(7)(j) does not require the Applicant to provide on-site detention of stormwater runoff from the development proposed on the western portion of the site. The eastern portion of the site, however, would require detention under EC 9.8325(7)(j). As noted above, the Applicant's proposed detention ponds that overflowed to open drainage systems on City parklands did not meet this criterion. The PC addresses this with the imposition of condition of approval #3. Further, even though the flow control standards at EC 9.6793 do not apply, the PC endorses the HO's condition for compliance because it provides the detention necessary to address the approval criterion at EC 9.8325(13). The key to compliance with EC 9.8325(13) is that the development will provide onsite detention, so that stormwater runoff will not increase peak flows or velocity in such a manner as to cause damage to the open drainage system. The HO addressed this criterion as follows: The above approval criterion is specific to "stormwater runoff from the PUD," rather than street and utility crossings of the onsite natural drainage courses. As addressed previously at EC 9.83251710), regarding the stormwater development standards at EC 9.6791 through EC 9.6797, the western portion of the development site does not direct stormwater runoff from the PUD to an on-site waterway, although the proposed piped system does outfall to an open drainage system farther to the north. The condition of approval required to comply with EC 9.8325(7)(j) that addresses flow- control ensures that the application complies this approval criterion. (See page 34 of HO Decision.) Final Order- Deerbrook PUD (PDT 12-1) December 17, 2012 Page 29 32