Effective sediment control for dredging with GEOTUBE

Overview

Manila Bay's environment is rapidly deteriorating due to high pollution levels from various sources such as marine, domestic, industrial, and commercial waste. This pollution threatens marine life and the livelihoods of those who depend on the bay's resources. Recent tests by the DENR have shown that the coliform level in Manila Bay is a staggering 330 million MPN (most probable number), far exceeding the acceptable level of less than 100 MPN.

Challenge

To address this issue, the Philippine government has prioritized the rehabilitation of Manila Bay, following successful campaigns in places like Boracay. The first phase of the project involves extensive dredging and sediment control to clean and reduce water pollutants. For this task, the GEOTUBE^® SC system has been selected as the optimal solution.

Solution

Design:

Dredging activities disturb sediments that must be contained to prevent the spread of pollutants. The GEOTUBE SC system ensures sediment control throughout the dredging operation. To protect the silt curtain from degradation caused by weathering, a special UV shield has been developed. This UV shield has a fabric with a tensile strength of 45 kN/m (10,116 lb/ft) and maintains at least 80% strength retention after 5,000 hours of UV exposure, equivalent to 42 months of outdoor exposure.

Construction:

A total of 2.7 km (1.68 miles) of TenCate GEOTUBE SC were delivered to the site in 20 m (65.62 ft) sections with depths ranging from 2 m (6.56 ft) to 5 m (16.4 ft). The silt curtains were laid close to the deployment zone for easy assembly. Floaters with a diameter of 300 mm (11.81 inches) were inserted into the silt curtain canvas cover. Each 5 m (16.4 ft) panel of the silt curtain was connected using hooks and reinforced belts. Once assembled, the silt curtains were towed into the water by motorized boats and securely fixed with anchors.

Performance:

Properly designed silt curtain systems, like the GEOTUBE SC, are crucial in preventing dredging sediments from contaminating surrounding waters. By maintaining a clean environment and protecting the marine ecosystem, these systems are highly effective. In this project, the installation of the TenCate GEOTUBE SC along a 2 km (1.24 miles) stretch of Manila Bay successfully confined turbid water and prevented sediment pollution outside the work area.