4817 RUCKER AVE 2024-12-09 - Laserfiche WebLink

• Storm water discharges shall match developed discharge durations to existing site durations for the range of existing discharge rates from the 10-year peak flow through the full 100-year peak flow. (note that this requirement is different than what was modeled for this project) Update drainage calculation section for these thresholds. WWHM updated • Peak runoff rates from the developed site shall not exceed existing site runoff rates in the 25- year and 100-year return intervals. Not exceeded The existing condition to be matched shall be the site as it exists at the time of application. Calculations shall be performed using a continuous simulation modeling program approved by the Washington Department of Ecology for storm water facility design in Western Washington. Modeling shall be performed using a 5-minute timestep. (revise modeling calcs to match this requirement) WWHM revised to 5 minute timestep The Flow Control Performance Standard may be achieved through any combination of onsite stormwater management techniques,flow control BMPs and selective site design which can be demonstrated to achieve the standard. Modeling for Rock-Filled-Infiltration: Revise model to model for the requirements in the two bullets listed above. Revised Reiser height is listed as 5 feet but the rim of the structure is only 2.5 ft above invert. Revise. The riser height is correct.The SSD table can be opened to see that the return interval discharges match the heights modeled. Riser height is measured from facility bottom and is mostly theoretical to make the model work. A 5' riser height equates to a 5' stage above facility bottom, but we have 6' available, which means the stage has not reached the top of rock. Modeling for basins A& D: See my comments in previous email (attached). Revised to include the small amount of existing sidewalk Thanks, Amie Roshak, P.E. Associate Engineer I Public Works—Utilities Engineering P: 425.257.7249 1 F: 425.257.6735 13200 Cedar Street, Everett, WA 98201 everettwa.gov/pw I Facebook I Twitter Note:Emails and attachments sent to and from the City of Everett are public records and may be subject to disclosure pursuant to the Public Records Act.