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Chapter 4-Site-Specific industrial Storm Water BTOPs <br />• <br />I What to Consider <br />Sediment traps are suitable for small drainage areas, usually no more than 10 acres, that have no <br />unusual drainage features. The trap should be large enough to allow the sediments to settle and <br />should have a capacity to store the collected sediment until it is removed. The volume of storage <br />required depends upon the amount and intensity of expected rainfall and on estimated quantities of <br />sediment in the storm water runoff. Check your Permit to see if it specifies a minimum storage <br />volume for sediment traps. <br />A sediment trap is effective for approximately 18 months. During this period, the trap should be <br />readily accessible for periodic maintenance and sediment removal. Traps should be inspected after <br />each rainfall and cleaned when no more than half the design volume has been filled with collected <br />sediment. The trap should remain in operation and be properly maintained until the site area is <br />permanently stabilized by vegetation and/or when permanent structures are in place. <br />Advantages of a Sediment Trap <br />• Protects downstream areas from clogging or damage due to sediment deposits <br />• Is inexpensive and simple to install <br />• Can simplify the design process by trapping sediment at specific spots onsite <br />• <br />Disadvantages of a Sediment Trap <br />• Is suitable only for a limited area <br />• Is effective only if properly maintained <br />• Will not remove very fine silts and clays <br />• Has a short life span <br />r <br />4-87