Wahyoe Boediwardhana, Malang – Cleanup work to flush away mud deposits from the Porong River in Sidoarjo, East Java, to the sea during the rainy season would not cause problems, an official said.
The statement came from the new managing director of the East Java Jasa Tirta state river management agency (PJT), Tjoek Waluyo, who was recently appointed in Malang.
He said the company had successfully flushed away mud sediment several times previously using river water at volumes ranging between 50 to 200 cubic meters per second, combined with the use of dredgers owned by the Sidoarjo Mudflow Mitigation Agency (BPLS).
PJT had earlier dredged and cleared a silted-up area near the mud disposal pipes using a volume of water from upstream.
"The biggest volume of water we released to wash away the mud was 208 cu.m. per second and the result was positive. The diluted mud was able to flow out to sea," Tjoek told reporters.
Tjoek said the biggest volume of water Porong River had ever contained was recorded at 1,500 cu.m. per second during the floods of March 2002.
The agency, he said, released a considerable volume of water because the river functioned as a flood control waterway for the Brantas River to prevent floods in Surabaya.
"Flushing the mud with 200 cu.m. per second of water was enough to push it out to sea, let alone the 1,500 cu.m. that came later," he said.
He said residents shouldn't be worried about the possibility of floods occurring during the rainy season, as problem areas would be dredged.
Tjoek said the BPLS had placed a number of dredgers at the downstream area near the Porong River delta and at the mud disposal pipes.
"The BPLS has deployed a large dredger at the mouth of the river to remove mud blockage in the delta area and a couple along the river," he said.
The PJT assured the cleanup process would not disrupt the Brantas River management system.
Tjoek said some of the water used to flush away the mud deposits originated from the Sutami Dam in Karangkates, Malang regency, which acts as a flood control facility, irrigation system, source of clean water and power generating source for Java and Bali.
He added the PJT would only use a small amount of water for the cleanup process, while the rest would be taken from the Brantas River.
"So, don't be worried the cleanup operation would affect other (waterways). We have already sorted this matter. The dam operation system will remain in control."
Separately, director general of water resources at the State Ministry of State Enterprises Iwan Nursyirwan Diar gave his assurance there would not be any changes to the main function of Porong River as a flood control means for Brantas River.
"I guarantee the Porong River's function as a flood control waterway will remain effective," Iwan said.
He praised efforts made by the PJT and the BPLS in the cleanup process, saying a combination of dredging and flushing would achieve a favorable result.
"We will continue to deposit mud into the Porong River because this is the government arrangement."
The agency has also carried out other measures to combat possible impacts the cleanup drive may cause, such as restoring and reinforcing Porong River embankments.
"We have also repaired the dike we earlier dismantled to make way for a dredger," Iwan said.