Work on troubled Kumaka revetment halted

-backfilled soil slipping into water

Work on the Kumaka revetment in the Mabaruma Sub-region has stalled for the second time this year and loads of earth, which were packed into the area, were last evening falling into the nearby Aruka River.

Stabroek News understands that the private contractor has abandoned the project amid protests from persons in the business community there that the work being done could not effectively solve the problem.

Minister of Transport and Hydraulics, Robeson Benn, told Stabroek News last evening that a team of engineers visited the area yesterday to assess the situation after the ministry received reports that the soil used to backfill the area was slipping into the Aruka River. However, he said, he had not been briefed by the team and as such could not comment further on the issue.

In this picture taken yesterday, a man stands on the area which was being backfilled at the Kumaka waterfront. The level of the area is below that of the harder surface shown at left.

Kumaka businessman Alan Adams told Stabroek News yesterday that members of the business community recently met the regional administration and discussions were ongoing as regards the issue. He said the 10-member team visited the Regional Administration office at Mabaruma and spoke with Regional Chairman, Paul Pierre on the issue. Two days later, the work ceased.

A resident of the Region One community told Stabroek News yesterday that loads of earth, which were packed into the area had begun slipping into the river over the past three days as the revetment was being forced into the waterway under pressure from the soil. She said that on Wednesday evening there were loud cracks beneath the surface of the fragile waterfront as the revetment leaned further into the river under pressure.

Meanwhile, Adams stated that he had been advising the work team “from a layman’s perspective that what they were doing was wrong”. He said the piles were driven into the shallow section of the waterfront. “I told them that they need to pall–off the area more into the hard surface but they didn’t listen and instead they gone about 40 feet more out.”

He said that area was fragile and according to him, “a man dive in front there recently and he told me personally that he was able to swim under the piles. Imagine that meh friend.”

At the moment, Adams said, the mud was slipping under the revetment daily and according to him, “when the whole front gone, we ain’t got no more Kumaka and business gon dead here.”

Stabroek News visited Kumaka two weeks ago when work was in full swing; the workmen were compacting the area with earth. Residents had argued then that the piles which were driven into the earth, were sunk to some 40 feet, but noted that the depth of the problematic area was as much as 70 feet.

The contractor had also tied the revetment to the support piles months after the revetment was built, a critical engineering flaw which would add pressure to the shallow waterfront.

Engineer Charles Sohan had stated in the letter columns of this newspaper this week that the project should have been halted a long time ago, given the type of work being effected by the contractor. “It is unfortunate that over 300 ft or so of revetment has already been completed and the Ministry of Public Works (MPW) did not recognize that something was amiss during its construction, although it was clearly evident to residents of the area that the design appeared to have serious flaws and the contractor was executing poor quality work as it progressed,” Sohan said in his letter.

He added that the misalignment of the revetment was indicative that a rotational and stability failure involving the piles, sheeting and anchorages had started. To exacerbate the situation, Sohan said, the contractor had been backfilling using a CAT excavator. He was placing layers of weak soil to replenish displaced and settled material behind the revetment, and this put additional lateral pressures on it and caused the structure to tilt and slide faster into the river.

He said that the Works Ministry should have its geotechnical and structural design calculation rechecked urgently to ensure that the revetment’s sheet piles were driven to firm soil below the compressible layer and river bed with adequate tie-back anchorage, and that the lateral soil and pore pressures on it are within the factor of safety for stability and rotational failures.

The waterfront had been eroding for months. Reports are that some three years ago, when the country experienced a tremor, the business community at Kumaka observed sections of the land shifting into the river.

The area had been threatened by the nearby river for a number of years and residents had been calling on the authorities ever since to address the issue. Several businesses have already removed from the waterfront area.

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