1716 W MARINE VIEW DR BASE FILE 2018-01-02 MF Import

Enginren P7amtrrs sunvrn; September 15, 1995 File No. 24-93-016-006-01 Reid Middleton, Inc. 1903133rd Ave. W. Suite 301 Mr. Kirk Brooks 110. Box 608 City of Everett Lynnwood, WA Public Services Division 3200 Cedar Street 9so3aa3s Everett, WA 98201 Phone 205 775-3433 Subject: Port of Everett Southeast Marina Project FAX 206775-3439 Dear Kirk, Enclosed are calcull:'ions regarding the question, dated July 6, 1995, from Dan Mathias regarding potential additional flows from The Landing project (formerly called the Southeast Marina project). In summary, the peak flow from a 6-month, 24-hour storm, is 1.52 cubic feet per second (cfs). This peak flow would occur for a short duration (10 minutes according to the model), with the average flow over the 24-hour storm period being 0.32 cfs. Stormwater regulations require this peak be treated prior to discharge to surface waters. For this project, "treatment" is diverting the flow to the sanitary sewer. During a 2-year, 24-hour storm, the 10-minute peak would increase to 2.38 cfs (0.86 cfs more than the 6-month peak), with the 24-hour average being 0.50 cfs. In normal conditions most of the 2-year storm flow in excess of the 6-month storm peak (1.52 cfs) will bypass the sewer connection and discharge directly to the existing outfall in the marina. On an occasion when a higher tide occurs at the same time as the peak of a 2-year, 24-hour storm, the bypass of the 2-year, 24-hour storm will be less. Statistically, this is expected to happen once every 16 years. The peak flow during this event to the sanitary sewer would be 2.38 cfs (the entire 2-year, 24-hour peak). This should answer the question and allow the drawings to be approved. Please call me if you have any additional questions. Sincerely, REID MIDDLETON, INC. Pa A MA Robert O. Galteland, P.E. Project Engineer vlt\wt\evt\semarina\,alcltr.rog { D Enclosure II r L Lt 1 D U SEP 15 1995 CITY OF EVERETT Bldg. Permit Counter