1600 121ST ST SE 2016-01-01 MF Import

2) the maximum water depth of the facility does not exceed three feet during a two year storm, nor exceed three feet for more than four hours for a 25 year storm; the side slopes are a maximum of 3:1 (H:V); and the facility is a dual use facility; or 3) specific City Council approval is q��nted for an exemption per the criteria in the �ity's Design and Construction Standards and Specifications. If fencing is required, its exact location and also the location of the gates necessary to access the pond for maintenance must be shown. Detention Pond• If any berms will be created as part of the surface pond design, the followinq note regarding pond berm r3tcri,3ls on the plans must be includ�.d on the plans: NOTE: Berm soils shall consist of m�t��rial ccnforming to the following gradation: Sieve Size $ Passing 3" 100 ,Y4 65-9U ,�200 12-2U All the inflows to the pond from paved areas must enter the first cell of the pond, if feasible. The access road must also be provided to this first cell, as it is in this first cell that sediment will accumulate. The outlet of the pond ehould be from the second cell. The top of the berm between the two cells should be protected against erosion by covering the top of it with rip-rap. All inlets to the pond ehould be protected against erosion with rip-rap. The rip-rap should extend from the outlet of the pipe to the bottom af the pond. What appears to be a rip-rap pad at outfall 4A should te called out as such. If the pond will provide dead storage, plants sho..ld be established in the bottom of the pond. Small fruited bulrush, yelluw iris, and cattails should do well in depths of water 0.5 to 1.0 foot. The plans should call out the type of vegetation tc+ be planted, t.he density c,f the plantings, and the total number of plants needed. One p1anL• every 1-2 square feet, with plants of the same type planted in groups, is recommended.