Silt Curtains & Turbidity Barriers – Africa

Silt curtain deployment requires advance planning, correct anchoring, and disciplined handling procedures. The two most common causes of silt curtain failure on African waterway projects are inadequate anchoring that allows the curtain to drift or collapse under tidal load, and incorrect skirt depth that causes the curtain to billow, drag the seabed, or flare under current. Both are preventable with correct specification and competent site supervision.

Pre-Deployment Preparation - Install the anchoring system in the waterway before the curtain arrives at the water's edge. Confirm anchor positions account for tidal rise and fall and allow sufficient mooring line length for the curtain to move vertically without stress. Ensure a clear working area on shore or on the deployment vessel. Join pallet sections in consecutive order on land with the skirt remaining furled. For large deployments across multiple pallets, confirm each pallet is numbered and sequenced correctly before any section enters the water.

Towing to Position – Once the desired curtain length is connected and furled, tow the system to the deployment location at a maximum speed of two to three knots. The curtain must remain furled during towing. Never drag an unfurled curtain with the skirt deployed through water - this places severe and undue stress on the webbing, connectors, and skirt material and will cause damage.

Anchoring and Skirt Release – Secure the furled curtain to the anchoring system before releasing the skirt. Check that the skirt is not twisted around the flotation chamber - a twisted skirt will not deploy correctly and will concentrate stress at the twist point. Once the curtain is anchored in the correct position and confirmed untwisted, remove the ties furling the skirt and allow the curtain system to drop into place under its own ballast weight. Do not attach the curtain directly to piles or poles driven into the seabed under any circumstances.

Confirming Correct Deployment – After the skirt has deployed, visually confirm the curtain is sitting vertically in the water column, the ballast chain is hanging freely and not resting on the seabed, and the freeboard is sitting correctly above the waterline. Check that all connector points are secure and that the curtain forms the intended configuration - closed, open, or maze - relative to the work area and any adjacent structures. Confirm a minimum 0.5m gap exists between the skirt base and the seabed at low tide.

Repositioning if Required – If the curtain needs to be moved after initial deployment, furl the skirt before dragging or towing the system to its new position. Never reposition an unfurled curtain. Disconnect from anchoring points, furl, reposition, re-anchor, and re-release the skirt in sequence.

Ongoing Inspection and Maintenance – For deployments longer than three months implement a scheduled inspection programme. Check curtain position, skirt condition, anchor line integrity, connector and zipper condition, marine growth accumulation, and hardware wear at anchoring points at intervals determined by site exposure - from daily in high-energy environments to quarterly in sheltered stable conditions. Keep a spare curtain section on site. Record all inspections and maintenance actions. Where visual inspection from the surface is insufficient, deploy underwater divers to inspect the submerged skirt and connections - particularly following any observed sediment plume within the protected area.

Recovery – Before removing the curtain, cease all marine works and conduct a visual inspection of water quality within the protected area to confirm no active sediment plume. Disconnect the curtain from anchoring points, furl the skirt, and remove the mooring system. Tow the furled curtain back to the launch site. On land, clean with a high-pressure washer to remove biofouling, silt, and sediment, allow to dry completely, and repack on pallets for storage or disposal. A well-maintained curtain can be redeployed on future projects.