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Contract 420

SECTION ONE

The mid Kent section was started six months later than the adjoining structure-rich contracts, which meant it missed the benefit of the extraordinarily dry 1998/99 winter.

But like all the eastern end of Section One it caught the full flood of last winter's deluge. Lakes formed in the part finished cuts and remained for months in places such as Fairbourne Lane, Harrietsham.

Many areas could not be drained because of the damage that floodwater and silt would have wrought to local watercourses - which RLE had been meticulous in protecting right from the start of construction. Deep scars were eroded in unprotected slopes where the vegetation had yet to take hold.

The result for the country contracts, 420 and 440, is a huge claim against the project insurance. Tens of millions are being negotiated.

Now the ground is drying, extra hours are being worked to make up and the muckshift is going full out. Curiously some of the clay sections have dried out faster than sandy areas, which in many cases have remained like thick soup.

The priority is to get the earthworks shaped up so the formation can be laid on top. Only then can track drainage be placed.

A feature of the Mid Kent contract are short tunnels used in the most environmentally sensitive areas. Piled walls were used for several, including Boxley Tunnel where the line is hemmed in by woodland that has to be protected.

At two sites where there was open space the joint venture opted for a more economical alternative using precast arches from Reinforced Earth Company and erection subcontractor PCE.

The half arch units are staggered to avoid the need for centring and have an insitu stitch at the crown. Backfilling of the 360m long Eyhorne Street Tunnel had to wait until last month when the sand had dried out enough for the delicate balanced compaction operation each side of the arches.

Contract 420 - Mid Kent, Boxley to Lenham Heath Hochtief/Norwest Holst Joint Venture 20km Target Cost £85M Key features: Includes transit of Boxley Valley which was always one of the most environmentally sensitive sections of CTRL. Most of the route follows close to the M20.

Continuing heavy rain last autumn and into this year curtailed muckshifting and made parts of the site impassable. Now the ground is drying out there is a rush on to complete the earthworks. Finished structures, earthworks and mitigation bunds are softening into the landscape as vegetation begins to grow again.

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