3214 BROADWAY BROADWAY KINECT APARTMENTS 2021-08-11

• • CITY OF EVERETT STORMWATER MANAGEMENT MANUAL • Maintenance Standards • 1. During the establishment period, check grass-lined channels after every rainfall. • 2. After grass is established, periodically check the channel; check it after every heavy rainfall • event. Immediately make repairs. 3. It is particularly important to check the channel outlet and all road crossings for bank stability and • evidence of piping or scour holes. • 4. Remove all significant sediment accumulations to maintain the designed carrying capacity. Keep • the grass in a healthy, vigorous condition at all times, since it is the primary erosion protection for • the channel. • 3.3.3 BMP C202: Channel Lining • Purpose • To protect erodible channels by providing a channel liner using either blankets or riprap. • Conditions of Use • When natural soils or vegetated stabilized soils in a channel are not adequate to prevent channel erosion. • 1. When a permanent ditch or pipe system is to be installed and a temporary measure is needed. • 2. In almost all cases, synthetic and organic coconut blankets are more effective than riprap for • protecting channels from erosion. Blankets can be used with and without vegetation. Blanketed • channels can be designed to handle any expected flow and longevity requirement. Some • synthetic blankets have a predicted life span of 50 years or more,even in sunlight. • 3. Other reasons why blankets are better than rock include the availability of blankets over rock. In • many areas of the state,rock is not easily obtainable or is very expensive to haul to a site. Blankets can be delivered anywhere. Rock requires the use of dump trucks to haul and heavy • equipment to place. Blankets usually only require laborers with hand tools, and sometimes a • backhoe. 4. The Federal Highway Administration recommends not using flexible liners whenever the slope • exceeds 10 percent or the shear stress exceeds 8 pounds/square foot. • Design and Installation Specifications • 1. See BMP C122 for information on blankets. • 2. Since riprap is used where erosion potential is high, construction must be sequenced so that the • riprap is put in place with the minimum possible delay. • 3. Disturbance of areas where riprap is to be placed should be undertaken only when final • preparation and placement of the riprap can follow immediately behind the initial disturbance. • Where riprap is used for outlet protection,the riprap should be placed before or in conjunction with the construction of the pipe or channel so that it is in place when the pipe or channel begins • to operate. • 4. The designer, after determining the riprap size that will be stable under the flow conditions, shall • consider that size to be a minimum size and then,based on riprap gradations actually available in • the area, select the size or sizes that equal or exceed the minimum size. The possibility of drainage structure damage by children shall be considered in selecting a riprap size, especially if • there is nearby water or a gully in which to toss the stones. • • • Volume II—Construction Stormwater Pollution Prevention • 3-39 • •