WITH the Derwent flood defences under fire for delays, the contractor has come up with a scheme to ensure the work is completed on time.

Contractors building the defences have had to go back in history for the innovative process to ensure the scheme for the twin towns meets the deadline.

Interserve Project Services, which is building the £6.5m scheme for the Environment Agency, says it is determined to have the defences "water-tight" by November.

Plans for the section of the defences have had to be continually re-designed and modified as they are built, said the scheme project manager, John MacDonald, and methods of working changed as Interserve came up against difficult sections of ground.

"The sections of defence walls alongside the railway line have had to be built at night to fit in with the operation of rail services. This is a slow process due to the short working time allowed each night."

He added that to ensure the project finishes on time, Interserve has looked for other solutions so that work can be carried out during the day and speed up the process.

"The new system that Interserve has found is being used near Priorpot Beck and the Derwent Surgery in Norton," said Mr MacDonald.

The process, known as "screwfast piling", is being used where the riverbank is so weak that methods used elsewhere in the scheme are impractical, he added.

"It is a method of working originally used by the Victorians," said Mr MacDonald. They used the technique for constructing bridges.

"The process uses a pair of large screw piles in every section that are twisted into the ground using modern high-power hydraulic machinery. The defence wall is then built up off the pile foundation."

He said that in certain areas, Interserve could not use the heavy piling machine as the riverbank is too weak to withstand the weight.

"This method of building flood defences is new, but gives the wall a stable foundation within the riverbank that will withstand the pressure of water against it when levels in the river are high.

"It means that we can use smaller and lighter machinery on site and, in the case of the property near the surgery, cause much less disruption and damage to the householder's garden. It is a method that has not yet been widely used, but is an excellent new method of constructing a defence wall."

Interserve staff have been specially trained by the designers of the process to install the screw piles on site. A combination of hard and soft defences are being built by the company which has been on site since January this year, after the Environment Agency fast-tracked the Malton and Norton flood alleviation scheme following the two major floods in two years.

However, both residents and councillors have hit out over what they see as the slow progress towards completion of the defences.

Howard Keal, chairman of the Derwent Action Group, claims Ryedale District Council has missed its target for completion of the project.

He said: "A public meeting in Norton immediately after the November 2000 floods was told work would begin in spring and be completed by the autumn of last year. We are now left holding our breath hoping that the authority's pumping station for Mill Beck will be in place before homes and businesses are hit again."

Meanwhile, Norton councillor David Lloyd-Williams blamed the district for any delays caused by the need for Transco to complete work before Interserve could move in to carry out their portion of the project, saying that "the responsibility rests with the prime mover, which is the district council".

He said: "I think if you are the main instigator of a project then you make sure from the start that all the sub-contractors and work necessary to start your contract is in order."

Updated: 09:22 Wednesday, September 18, 2002