Turbidity Barrier - Sediment / Pollutant Containment
LOCATION: Seattle, WA SCOPE OF WORK: Desgin & supply Type 2.DOT approved turbidity barrier system
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Challenge: A large diameter storm drain outfall pipe that discharges into Lake Washington (Seattle) required relining. This was a high profile project because municipal and state regulartory agencies were monitoring compliance with the specification that called for a zero tolerance for any pollutants or discharge of sediment into the fish bearing lake. In addition, the containment barrier had to remain stationary and withstand significant wave action from winds, power boats, personal water crafts, water skiers and wake boarders.
Solution: Layfield designed and supplied a Type 2.DOT approved impermeable turbidity barrier system that included both barrier curtains and anchor kits to hold and secure the barrier system in place.
Materials: A Type 2.DOT Turbidity Barrier must comply with U.S.A.C.E. standards. The barriers are made from strong 18 oz/yd2, high visibility yellow reinforced vinyl. Each individual curtain has a 5/16" cable along the floats that connect the curtains and provide stabilization. A 5/16" ballast chain is also pre-installed into each curtain to ensure they stay veritical. Aluminum wear shields on each bottom corner ensure high stress areas don't get damaged. Two custom curtains were supplied that tapered from the shore to a depth of 30' and ran perpendicular to the shore line 60'. These two curtains were connected to two end curtains that were 30' deep and 40' long. Six Type 'B' anchor kits were supplied to hold the entire system in place.
Special Features: For this project the top floatation was upgraded to a 12" x 12" float to obtain the necessary freeboard from the high wave action. Due to the extreme hard pan on the lake bottom the 25 lbs. Danforth anchors were replaced with 400 lbs. concrete blocks. The project site had virtually no staging area so Layfield packaged the curtains in a manner that allowed for easy deployment. The high strength barrier system performed perfectly under the demanding conditions and that allowed the contractor to focus on relining the pipe without distraction or delay.