How surface water would be dealt with in any proposal to quarry Straitgate has fundamental implications for flooding, groundwater recharge for springs and water supplies, stream flows and airport safeguarding.
Even Aggregate Industries recognises pre-emptive planning is key to flood defence:
The Great British weather has only become more erratic in recent years, with torrential storms and heavy rain frequently causing widespread flooding and misery – and the reality, unfortunately, is that it is likely to get worse.
The issue at Straitgate is so sensitive that the Environment Agency has already said that a number of conditions "must be secured on any planning permission", including:
8. The working and restoration infiltration design shall ensure that drainage mimics the pre-excavation drainage. This shall be achieved following the principles described in the July 2017 Hydrogeology/Drainage Regulation 22 responses report.
But as we’ve already pointed out – here, here, here and here – Aggregate Industries’ infiltration plans could not work as described, post-extraction drainage could not mimic pre-excavation drainage.
This issue stretches back a long way. It’s not as if Aggregate Industries hasn’t been warned.
In 2015, the Environment Agency said:
The development should be designed so that drainage from the site mimics, as closely as possible, the natural hydrograph in perpetuity – this will ensure that the hydrographs of springs and water courses in the area are not adversely impacted.
We object to the planning application, as submitted, because the applicant has not supplied adequate information to demonstrate that the risks posed to groundwater can be satisfactorily managed. We advise that this further information should be requested under Regulation 22 of the Environmental Impact Assessment regulations.
On infiltration areas, in particular:
8. The working and restoration infiltration design should be described in detail. How will it ensure that drainage will mimic the pre-excavation drainage?
A Regulation 22 request was duly made by Devon County Council. A meeting was held between personnel from the Environment Agency, Aggregate Industries and its consultants. Minutes were produced. On the subject of infiltration areas:
MW [from the Environment Agency] said that the final restoration profile should mimic the current one so as to ensure recharge is not inadvertently moved from one sub-catchment to another thereby ensuring the headwater flows remained similar.
Aggregate Industries produced a response, "the July 2017 Hydrogeology/Drainage Regulation 22 responses report." Don’t worry, they fibbed:
2.9.4 The majority (i.e. 2/3) of the planned extraction area will be at either post-restoration or pre-extraction stage, with natural runoff patterns following the slope gradient, and infiltration to the relevant sub-catchment. 2.9.8 The restoration has therefore been designed to ensure the site is restored to baseline conditions (i.e. ‘mimic’ them), with some betterment provided where possible.
It was fiction. The final restoration profile could not mimic the current profile; there would not be "natural runoff patterns following the slope gradient" given that the base of any quarry, the revised MWWT – the blue contours – does not mimic the existing topography – the brown contours – as shown below:
And the 2/3 claim? Could just 1/3 of the site be worked at any one time? Of course not.
It is proposed to quarry Straitgate in three phases. When it comes to Phase 3, the Flood Risk Assessment says:
3.2 Phase 3 area... Soils will be placed onto the Phase 1 area to restore this area to final the landform... Overburden will be placed within Phase 2 area, with the exception of the eastern infiltration area which is to be left open.
In other words, as phase 3 is started, phases 1 and 2 have not yet been restored.
And this is still what’s proposed, according to the newly delivered Soils Management document. i.e.
For phase 1:
This stage is illustrated by Drawing SF / 5-1 Rev B. The soils that are stripped from this initial phase may remain in store for a period of approximately 10 years…
For phase 2:
Some of the soils from Phase 2 may need to go into storage and extend the original Phase 1 bunds in the east of the site. The soils that are put into storage from this second phase may remain in store for a period of approximately 8 years…
For phase 3:
All of the soil resources from Phase 3 will then be direct placed into the previously worked out void, as shown in Drawing SF / 5-3 Rev B.
Again, all phases being worked at the same time – not 2/3 "at either post-restoration or pre-extraction stage". In fact, by the end of phase 2, 2/3 of the site would be excavated, and would stay this way until the end of phase 3.
It was a simple thing, but Aggregate Industries still couldn’t come clean.
