2007-012A - Laserfiche WebLink

Home Browse Search

+ Chapter 4 - Best Management Practices for Erosion and Sediment Control Maximum velocities The maximum allowable velocity in the emergency spillway channel will depend upon the type of lining used . For vegetated linings, allowable velocities are listed in Table 5 . 35a (STORMWATER CONVEYANCE CHANNEL - Section 5.35 - ES BMP 1 .35). For non -erodible linings , such as concrete or asphalt paving and riprap , design velocities may + be increased . However, the emergency spillway channel shall return the flow to the natural channel at a non -eroding velocity. See Appendix 1 .26A for design details . Stabilization of the Embankment and Basin The embankment of the sediment basin shall be temporarily seeded within 15 days after its + completion as perTEMPORARY SEEDING - Section 6 .65 (ES BMP 1 .65) . If excavation is required in the basin , side slopes should not be steeper than 2: 1 . Cleanout Sediment shall be removed from the basin when the capacity is reduced to 55 cubic yards per acre ( 104 M3/ha) of drainage area . This elevation should be clearly marked, preferably on the riser. Plans for the sediment basin shall state the methods for disposing of sediment removed from the basin . Possible alternatives are the use of the material in fill + areas on-site or removal to an approved off-site dump . Final removal Sediment basin plans shall show the final disposition of the sediment basin after the upstream drainage area is stabilized . The plans shall specify methods for the removal of + excess water lying over the sediment, stabilization of the basin site , and the disposal of any excess material . Sediment shall not be flushed into the stream or drainageway. Safety Sediment basins are attractive to children and can be very dangerous . Therefore , they should be fenced or otherwise made inaccessible to persons or animals unless this is deemed unnecessary due to the remoteness of the site or other circumstances . Strategically placed signs around the impoundment reading " DANGER-QUICKSAND" .. should also be installed . In any case , local ordinances and regulations regarding health and safety must be adhered to. .. Construction Specifications Site Preparation r Areas under the embankment and any structural works shall be cleared , grubbed , and stripped of topsoil to remove trees , vegetation , roots , or other objectionable material . In .. order to facilitate cleanout and restoration , the pool area (measured at the top of the principal spillway) will be cleared of all brush and trees . 449