After Has Highways 'thrown a curve ball'? back in 2015, Aggregate Industries produced some cross sections - see below - so that Highways England could "fully understand" the impact of any quarrying directly next to the A30. Highways England originally wanted to see "that the full depth of the quarry excavation would not be lower than the A30 carriageway", but settled for a series of planning conditions, which were repeated in the most recent response:
The maximum extent of quarry workings adjacent to the A30 trunk road boundary shall not exceed that shown on drawing SF HWYS/1 and at all times a minimum buffer zone of 10m shall be maintained between the application boundary and the quarry workings.... Buttressing of extraction slopes shall be undertaken in line with the submitted plans with an agreed slope profile as shown on drawing SF HWYS/1... Reason: ...to protect the highway structural integrity and in the interest of the safe and efficient operation of the trunk road.
Last week, however, Highways England said they would revisit the application.
There have been quarry face slippages at AI's Manor Farm sand and gravel quarry in Kempsford, Gloucestershire. In an application to extend the quarry, the MOD was concerned about nearby landing lights for RAF Fairford. AI's consultants had said:
A 20m stand off to each lighting column will allow for a worst case situation where the quarry face could fail and cut back to an angle below the natural angle of repose (a gradient of approximately 1 in 3) and the face failure would not reach the base of the closest lighting pole. 1 in 3 is considered to be a stable slope in this type of material and 20m should therefore give the lights the protection required plus a safety margin beyond that. 10
Although the extraction proposals incorporate stand-off zones to protect boundaries there are concerns that in some instances that these might not be adequate. A request to review these limits to prevent site stability problems during and post extraction is strongly recommended to avoid slippage problems already experienced from the current quarrying works. 6.29
Prior to the commencement of works the applicant shall submit a plan for the approval of the Mineral Planning Authority detailing how the adjoining MOD land and the retained land on which aircraft landing lights are located will be protected from collapse or slippage whilst extraction operations are undertaken and until restoration has been completed.
And what has AI proposed next to the A30 dual carriageway? Not 20m standoffs, but 10m. Not 1 in 3 slopes, but as steep as 1 in 0.5.
