Effective Sediment Control with Geotube® Silt Curtain for Dredging Operations

The challenge

Despite its economic and cultural endowment, Manila Bay’s environment has been deteriorating at an alarming rate. It is severely polluted with marine, domestic, industrial, and commercial waste - threatening marine life and the livelihoods primarily dependent on the bay’s resources. According to recent water samples and laboratory tests conducted by the DENR, Manila Bay’s coliform level is 330 million MPN, way beyond the acceptable level of less than 100 MPN.

The Philippine government now makes the rehabilitation of Manila Bay top priority following the successful campaign in Boracay and other popular beaches in the country. The first phase of the project is to clean and reduce the water pollutants of Manila Bay which involves massive dredging and sediment control.

The design

Dredging involves the disturbance of sediments and needs to be properly contained to prevent the spread of pollutants. TenCate Geotube® Silt Curtain system was chosen as the sediment control solution for the dredging works along Manila Bay. The silt curtain system had to remain functional throughout the entire dredging operation works to contain the sediments. A special UV shield was developed for the silt curtain to ensure that the exposed fabric does not degrade when subjected to weathering exposure. The fabric used for the silt curtain UV shield has a tensile strength of 45kN/m and strength retention of at least 80% when subjected to 5,000 hours of UV exposure in the UV chamber. This is equivalent to 42 months of outdoor exposure.

The construction

2.7km of TenCate Geotube® Silt Curtains were delivered to the site in sections of 20m lengths with a varying depth of 2m, 4m, and 5m. The silt curtains were laid down close to the deployment zone for easy assembly. Floaters of 300mm in diameter were inserted on the silt curtain canvas cover. Each panel, 5m in length of the silt curtains, were connected by hooks and reinforced belts. After assembling the silt curtain panels, it was then towed into the water by motorized boats to the desired location. The silt curtains were then fixed with the anchors in furled position.

The performance

With proper design and expertise, silt curtain systems are beneficial in keeping dredging sediments from polluting surrounding waters to maintain a clean environment and a healthy, undisturbed marine ecosystem. In this project, the installation of TenCate Geotube® Silt Curtain along the 2km stretch of Manila Bay had effectively confined turbid water and prevented sediment pollution outside the work area.

Overview of TenCate Geotube® Silt Curtain containing silt within the work area

Geotube® Silt Curtain being deployed to the work site

Effective performance of TenCate Geotube® Silt Curtain in sediment control

The Geotube® Silt Curtain hangs vertically and is connected to the concrete blocks