3301 SEAWAY BLVD WHOLE SITE 2025-10-30

Sabrina Fandler From: Sent: To: Subject: Attachments: Follow Up Flag: Flag Status: Hi Sabrina — Jane Zimmerman Thursday, May 26, 2016 2:39 PM Sabrina Fandler Bertch Capital plan/report review Bertch PAD.pdf Follow up Flagged Please see below for my first, very general review comments for the Bertch Capital site. The submitted plans and report lack much of the necessary detail to allow me to conduct a thorough review at this time. Therefore, my comments mostly reference sections of the City's Stormwater Management Manual for requirements that must be met and calculations that must be provided. In addition, I have also highlighted the City's PAD for SEPA 16-006 — see the attached document — to identify additional information required to address drainage -related requirements for this project. Thank you, Jane General stormwater requirements as detailed in the City's 2010 SWMM —the applicant must show that all applicable requirements are being met -Access road requirements per Chapter 2.2 of Volume III -Pond berm and embankment material and construction specifications as provided by a geotechnical engineer, see standards in Chapter 2.3 of Volume III for minimum requirements -Liner requirements per a geotechnical engineer's material and construction specifications, must include provisions for protection/identification for maintenance activities in the bottom of the pond -Pond fencing in accordance with Chapter 2.5 of Volume III -Overflow requirements per Chapter 2.9, Volume III and the calculations necessary to show the standards are being met. A secondary inlet to the flow control structure must be provided in accordance with Chapter 2.9 and the primary overflows to the two drainage basins must be proportioned in the same way as the design release rates. In addition, due to the height of the pond berm on the east side, an emergency spillway will be required. The location and design of the emergency spillway must be specifically reviewed and approved by the project's geotechnical engineer. More specific plan/report comments: -A minimum of 6" of sediment storage must be provided in the bottom of the pond -The grading for the pond must stay outside of the NGPE and all pond contour lines must close on the buildable area of the site, outside of the NGPE line. The proposed grading shown on the southeast side of the pond is not feasible and will either result in grading within the NGPE or a smaller than required pond. -The placement of the MWS units downstream of the detention pond control on this site is unacceptable due to the lack of elevation difference between the primary outlets and the invert elevation of the downstream drainage system. As located, the MWS units will create backwater effects that will reduce the effective head on the primary orifices of the flow control structures and unacceptably alter the stage -discharge relationship of the restrictor units — meaning that the pond will overflow more often than is allowable.