9300 W MALL DR 2018-01-01 MF Import

Y The location of the pond will most likely result in some interception of upstream drainage. This interception is not critical in the design of the wetpond, but may need to be accounted for in the design of the biofiltration swale, depending upon where the swale is located. Vegetated swales: A vegetated swa3.e is required per the SEPA approval conditions. Due tc the high g':oundwater table in the area and the 9enerally shaded conditions, the swale should be desi:led as a biofiltrat•ion swale. The following note should be added on the page wii:h tkee biofiltration swale cross-sectional details: NOTE: the specified biofiltration seed mix is not a , standard mix and will need to be specially ordered. Allow 3-4 weeks for delivery of the mix. If problems are encountered in obtaining a r.iix meeting the City's specifications, please contact Jane Zimmerman, City of Everett Public Works, at 25�-8800. The plan� should specify construction of the swale per section 4.15.1.2 of the City of Everett�s Design and Construction �tandards and Specifications. The swale seed and plant list from page IV-17 of the City's standards should also be inclu@ed on the plans. A vegetatvd swale could be incorporated into the side slopes of the wet pond under ihe following conditions: 1) the bottom of the swale was at or above the maximum storage elevation for the 2 year, 24 hour storm (the wetpond design storm). Other storms would be allowed te inundate the swale. 2) the berm separating the swale from the rest of the pond was a minimum of 1 foot high and 0.5 feet wide, with side slopes of 3:1 (please see attached sketch). 3) the surface area of the swale is subtracted from the surface area of the pond when performing wetpond calculations, especially in determining the amount of area to be planted with wetland vegetation If a swale is planned for after the wetpond, as depicted in the site plan, the swale must be located outside of the wetland buffer areas. Only minor grading of areas within the edge of buffers will be allowed to construct the swales.