MANILA, Philippines — The government’s move to dump crushed dolomite boulders is not a permanent solution to the problems besetting Manila Bay, the Mines and Geosciences Bureau (MGB) said yesterday.
The MGB, an attached agency of the Department of Environment and Natural Resources (DENR), said previous studies showed that beach nourishment is not a remedy to the Manila Bay issue.
“According to studies and scientific researches, mechanically placed sand on beaches moves as affected by waves, currents, tides and wind and other potential impacts of anthropogenic and natural events,” the MGB said.
Beach replenishment is the practice of adding sand or sediment to beaches to combat erosion and increase beach width.
However, the MGB said it is important to note that beach nourishment does not stop erosion.
“It merely prevents erosion for a short time,” the MGB said.
The DENR has started laying out crushed dolomite along the beach as part of the rehabilitation of Manila Bay.
The MGB cited international studies in California that found out that added coarser sand to some beaches stayed on despite energetic waves.
In one case, the bureau said the sand moved both north and south along the coast that contributed to the closure of a river estuary, causing concentrated pollution and hypoxia.
In the case of the dolomite sand spread along Manila Bay, the MGB said systematic monitoring of monsoon or seasonal currents should be done to follow the general pattern of the direction of movement and deposition of piles of sediments in the bay.
“The process will take some time but regular monitoring and studies will enable the DENR to predict on how the nourished sand will evolve,” the MGB said.
The DENR has clarified that the dolomite spread along Manila Bay is classified as coarse-grained sand, which is two to five millimeters in size or equivalent to 2,000 to 5,000 microns, and therefore almost 100 times bigger than dust.
“Famous islands known for their fine sand such as Panglao and Boracay became world-renowned for their powdery sand, which were derived from weathered coralline limestone and dolomitic limestone, and no health complaint has been filed by tourists and swimmers,” the DENR said.