In the latest instalment of a project designed to revamp Phnom Penh’s drainage system, officials have begun work expanding a sediment chamber near the Royal Palace to Wat Botum.

Phase three of the ongoing $350 million drainage system project spearheaded by the Japanese International Cooperation Agency (JICA) in collaboration with Phnom Penh City Hall began in early 2012 and is expected to be completed by April 2015, Long Dimanche, a City Hall spokesman, said.

“It is a big sediment chamber to protect flooding in Phnom Penh,” Dimanche said.

More than 10 construction workers began clearing an area on Botum Park’s northeast side of trees and other obstructions two weeks ago, preparing to dig the area, Hang Kong, a construction site chief, said.

The sediment chamber will play the role of a sediment trap, protecting drainage pipes upstream and downstream of the chamber from clogging. It will also act as a control box to change the flow direction in the rainy and dry seasons, said Toga Uchida, a JICA project formulation adviser.

The 10-metre-by-20-metre chamber, which will prevent debris from clogging drains and prevent floodwater from reaching the river, will be built 5.7 metres under the ground.

About 50 years old, the current sediment chamber spans from Street 240 to the border of the Royal Palace, and has deteriorated over the years, Uchida said.

JICA began working on the drainage project with City Hall in 1999. The initial two phases of the project cost more than $19 million and took nearly a decade to complete.

Construction of the Botum Park chamber is expected to be completed by August, Uchida said. The estimated cost has not yet been calculated.