Stability of the northern bank and the M25
The application has repeatedly alleged that the possibility of a failure in the Gault Clay on the northern slope could present a risk to the M25, which at its nearest point is 60 metres from the carriageway. Until very recently Highways England, the agency in charge of the motorway, has maintained that it had no concerns that the existing geology of the northern slope of the quarry poses a threat to the integrity of the M25.
In correspondence with Westerham Town Council dated March 2021, Highways England wrote, ‘Our statement from 2018 saying that the M25 is 60m from the northern slope and it would be unlikely that the slope failures would migrate that far north and reach the M25, has not changed.’
Correspondence with other enquirers in which Highways England stating that it has no record of a risk to the M25 from the Covers Farm northern slope can be seen by clicking here.
However, KWG understands that Highways England has not objected to the Covers infill application and is now acknowledging that in the longer term there may be a risk from the “do nothing” scenario.
In the course of this application Highways England has also made it clear that they want there to be monitoring of the stability of the slopes in case the proposed work has an effect on this.
The northern lake
The application claims that the water in the northern dip is not draining away and that in twenty years’ time it might overtop and flood the Croydon Road. This was simply extrapolated from a few aerial photos of the water sampled from various years.
The applicant supposed that there were silts and clay fines on the base of the dip, preventing the water from draining into the sandy stratum that lies beneath. However in material submitted in 2021 the applicant states that the northern lake is not lined with clay.
The idea that the water level is just increasing without ever subsiding seemed to be undermined at the December 2018 ‘Drop-in’ meeting when Mr Warde admitted that the water level of the northern lake goes up and down.
The applicant proposes to make a framework of embankments in the dip where the northern lake is, by tipping the construction waste into the water, and thereby create a series of cells. The cells would then be filled with waste, and the displaced water in each would be pumped into another lake to the south of the quarry.
The applicant insists that 0.8 million cubic metres of construction waste needs to be brought in to the site, requiring haulage in 84,000 four-axle tipper trucks, over an estimated 5-6 years. The haulage contractors would be paying the site owner to tip the waste here.
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