Rain, Tankers, Ground water, Rivers, and ……..Overpumping.

Rain? The UK Centre for Ecology and Hydrology has reported 2023 the wettest July-December period since records began in 1890. Ground water levels were reaching their highest ever recorded levels locally, reported the government’s Environment Agency (EA) who are responsible for monitoring both groundwater and river levels. All the stores for water are full, river, surface and groundwater stores, no trees, no evaporation and still it rains! So, water everywhere, including underground.

Ground water? This is water from rain that is soaked up by the rocks and the ground like a sponge. Underground it travels to the rivers and then flows away. Since 2013 the Chilbolton Flood Advisory Group (FAG, see below) has been recording ground water levels monthly at a local dip for the Environment Agency. We saw the highest ground water levels ever in December 2023. When these underground stores are full, there is nowhere for the water to go, so it appears at the surface, through floors, along the roads, into holes in the sewage pipes underground filling them up so the sewage pumping plant (designed primarily to handle solid waste) can’t cope.

Rivers?   In January 2024 every river in the area was so full they were overtopping their banks and despite a dry spell, the river levels just didn’t fall as the ground water continued to feed them.

And in Chilbolton……?

Tankers? SW used three tankers an hour in December and January to pump ground water surpluses away from SW’s main sewage pumping station. SW paid for them to ensure sewage did not back up into people’s homes through the drains or pour out onto the street and into people’s gardens. The tankering lowered the ground water levels near the main Chilbolton Sewage Pumping station significantly and averted the threat there. Many local villages are the same. But tankers are 24/7, noisy, disruptive and expensive in manpower and energy. The alternative?

Overpumping.  A bland term for discharging the water that is flooding the sewage pumping station into the river Test. It is piped through filtration tanks and regularly changed filter bags into the Abbotts stream and under the Sleeper bridge on the Common. This is very strictly controlled by the EA. A long-term Infiltration Reduction Plan (IRP) has to be produced by SW, and agreed by the EA. This was done by SW in 2018 and has been regularly reviewed. Over pumping cannot happen until the ground water in specified EA boreholes reaches a certain level. This level was triggered in October 2023. Despite permission SW then delayed overpumping, continuing tankering. At the time of writing 27.1.24 pumps and pipes are in place but tankering continues as press and media have taken up the issue in response to pressure from water bailiffs on this iconic river Test and the public.

The decision to overpump is not the Chilbolton Parish Council’s or FAG’s, it is solely in the hands of SW and the EA. We liaise but have to accept their assurance that minimal pollution will occur. Natural England who oversee the Common SSSI are also aware but are unable to over-ride the EA.

The Flood Advisory Group (FAG) was set up in 2002 to advise Chilbolton Parish Council on water issues and to ensure that they are well informed and that the village is as resilient as practically possible to both ground water and river floods. We bring in key personnel to advise. Brilliant members have been out digging out ditches, clearing drains, rodding our culverts, nagging the County to clear their culverts, liaising effectively with the Environment Agency and Southern Water and with local people at risk and since 2013 monitoring ground water levels with monthly dips. Major decisions though, like overpumping, are regulated by Government Agencies and the water companies. Details of Chilbolton’s IRP and the water treatment equipment (General appendix A) can be found at:

https://www.southernwater.co.uk/our-story/our-plans/infiltration-reduction-plan