Sewage in the Grom

We’ve been deeply shocked to discover that the Grom is full of raw sewage. It’s not a little bit of sewage, either – even when there hasn’t been heavy rain, Southern Water is pumping sewage for hours and hours.

How do we know?

The Upper Medway Sewage Action Group have been testing the Medway and the Grom for some months. The clearest sign that raw sewage is going into the Grom is the extremely high levels of e-coli that we have found.

This slide shows cultures of e-coli taken from the Grom. We shouldn’t see more than five blue blobs from a clean river’s sample. Instead the whole slide is covered – these are catastrophic levels of e-coli.

E-coli comes from the guts of mammals, and could come from livestock. But the worst samples in the whole area are always from the outfall from Southern Water’s waste water treatment works. The outfall enters the Grom below Green River Farm at Burrswood (there’s a very long pipe between the main works near Adams Well and the outfall).

People and animals can get very ill from e-coli so don’t let your dogs or children go in the water – and if you fish or use the river in any way, always wash your hands very carefully.

E-coli won’t affect the wildlife of the river much, but our samples also show that Nitrate, Phosphate and Ammonia levels are very high. This is almost certainly due to the sewage.

High Nitrates and Phosphates cause eutrophication – the river is too rich in nutrients and causes algae and some plants grow too fast, killing fish, invertebrates and other plants.

Even relatively low levels of Ammonia will kill fish, invertebrates and other wildlife.

Sewage in the Grom in numbers

In 2022 the waste water pumping station in Groombridge itself – that should handle our village’s waste – was overloaded on 31 separate occasions. It dumped untreated sewage directly into the Grom for a total of 324 hours. This is the equivalent to dumping untreated sewage in the river for 13.5 days non-stop.

The Tunbridge Wells South waste water treatment works dumped untreated sewage – some of it filtered but not treated – into the Grom 116 times, for a total of 788 hours.

Taken together, this means Southern Water dumped untreated sewage into the Grom for 1112 hours – or 46 days – in 2022.

This means that untreated sewage was dumped into the Grom by Southern Water for the equivalent of at least a month and a half of the year. In other words, for at least 12% of the year, Southern Water is dumping untreated sewage in this very small river. 

We say at least because these are only the notified sewage spills, and the duration total will be longer as discharges don’t start and stop at the same time.

You can see the figures for yourselves on the Rivers Trust’s sewage map.

River water quality

Members of the Upper Medway Sewage Action Group have been testing the Grom and the Medway for pollutants since late 2022.

In the group’s March report on levels of Ammonia, Nitrate and Phosphate, the Grom consistently tested well above safe levels:

“Of the 110+ samples taken to date 82 of them have proved to be in excess of DEFRA and Environment Agency (EA) guidelines.

74.5% of samples are above acceptable levels of Orthophosphate, Nitrate or Ammonia and in some cases all three!

To put things into context about the River Grom:

On July 7th 1991 an EA survey  found a fish biomass of 398kg/Ha (kilogrammes per hectare). A good fishery comes out at 200 and reasonable fishing is available at 100. We now believe that the Grom is now pretty much devoid of life!!!!!“

What next?

At their request, the Upper Medway Sewage Action Group is now supplying its test results to the Environment Agency (EA).

It reports all pollution incidents and is demanding that the EA takes action.

The Group is also campaigning to stop this shocking level of sewage release by Southern Water – you may have seen some of its members on the BBC news last month.

Sarah, who is part of the Wild Groombridge team, also belongs to the the Upper Medway Sewage Action Group. You can contact her here if you want to know more – there will be more action and campaigning soon.