Floating Silt Barrier - Burnaby Lake Rejuvenation Project
LOCATION: Burnaby, BC TIMEFRAME: January – June 2010 SCOPE OF WORK: 4,600 lineal Meters of Floating Silt Barrier PROJECT PARTNERS Owner/Client: Hazco Environmental Services
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Burnaby Lake is one of the few remaining lakes of significant ecological value within the Greater Vancouver area. It is home to over 400 plant, bird, and fish species, 16 of which are rare and endangered. The lake is also a recreation oasis, with more than 300,000 people who visit it each year. The project will restore the open water for the preservation of the diverse ecosystem and to re-establish the rowing course to international standards for events and training. This will require the removal of approximately 360,000 m3 of sediment off the silt-choked lake bed.
Dredging the lake bottom will produce a significant amount of turbidity. The turbidity would pose immediate danger to aquatic wildlife. Without a turbidity mitigation plan, the Environment Ministry would not issue its approval or permits to commence the dredging.
A pilot dredging project demonstrated that the permeable silt curtain was effective in maintaining total suspended solid (TSS) levels below 25 mg/L outside the silt curtain.
An inner silt curtain was used to prevent migration of suspended solids (turbidity) from the immediate dredging area and reduce or eliminate potential water quality effects. An outer/fish exclusion silt curtain was incorporated to direct fish around the dredging operation and provides a monitoring zone between the two silt curtains. The outer curtain will also act as an additional measure to prevent migration of suspended solids.
Where space in the lake permited, two inner silt curtains were set up within the outer curtain to allow the dredge to move from one inner curtain to another and still be within an outer/fish exclusion curtain. This limited the number of times the silt curtains had to be moved and consequently reduced any potential for water quality effects.
The Environmental Contractor contacted Layfield to submit a floating silt curtain design that would meet all of the projects requirements: contain the turbidity/silt, strong and durable components to withstand anticipated wind loads and turbulence caused by the dredging operation, light weight for ease of handling, cost effective considering the large quantity of curtains required.
Layfield provided the Environmental Contractor 305 modified floating silt curtains 2.75 m deep by 15.25 m long. The modifications included a high strength to weight ratio RPE 25 float cover and a load cable pocket located just below the floatation pocket. The contractor installed the load cable and ballast chain on-site.
The Environmental Contractor was able to order and install the Floating Silt Curtains in stages with Layfield accommodating the project schedule. The curtains performed their various functions as expected even though the thick vegetation on the lake bottom did propose some installation hurdles.
Once again, Layfield’s diverse line of Turbidity Barriers and Floating Silt Curtains meet demanding projects performance criteria, financial budget and schedule.