October 2012

Pollution incident

In late October last year the River Crane and the Duke of Northumberland’s River were both devastated by the uncontrolled discharge of an enormous volume of raw sewage. The incident occurred due to the blockage of a large Thames Water sewer main and the subsequent release of effluent into the river rather than allowing it to flood Heathrow Airport.

Over the last year the Friends of the River Crane Environment (FORCE) have been reviewing what has happened in response to this disaster and how the river is coping.

We know that, immediately following the pollution event, the river was essentially dead, all the fish and river insect life being killed along the 20 kilometres of the River Crane and Duke of Northumberland’s River between the outfall (next to the A4 in Cranford) and the River Thames.

Around 7000 mature fish, including seventeen different species, were bagged up and sent to Mogden to be counted and we estimate that upwards of 10,000 fish were killed in total.

The River Response

A river can recover naturally to pollution over time but it requires both good flushing flows and a healthy upstream source of life for this to happen. Unfortunately, last winter was fairly dry and by Spring this year there was still polluted sediment on the river gravels and the river itself remained in poor condition. FORCE undertook its first regular river sampling in March and found that no fish, and only a few river insects, had returned, and river life was dominated by black midges.

We were therefore very grateful for the heavy rains in the spring and early summer. These gave rise to high flushing flows along the river and helped to clear the sediment and algal growths from the gravels and to bring in more insect life from upstream. By mid May there were more signs of life with a good population of fresh water shrimps and may fly. There were still no fish however and this was to be the first summer in ten years that kingfishers did not breed at the Crane Park Island nature reserve.

On 29th May we celebrated the sighting, by FORCE members, of a first few sticklebacks in the river. Throughout the summer there were more regular public sightings of small fish and fish fry, as well as kingfishers returning to patrol the river. Our last formal sampling was in late August and we found a wide variety of insect life including mayfly and caddis fly and the first damselfly larvae. We also recorded stickleback and stone loach along with dace and roach fry.

It is clear that the river is slowly recovering, the numbers and variety of insect life have largely returned, and although we have yet to find dragonfly larvae we have seen them flying over the river again. At this stage in the recovery the numbers of insects are probably higher than they would have been before the pollution incident and this is due to the continued absence of the large fish that would normally eat them.

Regular sampling has shown us that fish numbers are now also slowly recovering, but we believe that it will take 10 to 15 years for the full age range of fish to be restored. We are also concerned about the current limited range of fish species and that some such as eels, pike and bullheads may not recover naturally if they are not present in the upstream river.

The human response

Immediately after the pollution incident Thames Water accepted full responsibility and pledged that they would fund the restoration of the river so that it would be in a better condition in 5 years time than prior to the incident. In the mean time the Environment Agency undertook to work on the prosecution that will see a case taken to court. One year on, we are still awaiting the date of this court case.

In April this year Thames Water made a formal commitment to work with the Crane Valley Partnership (a grouping of the key statutory and community organisations with an interest in the river) to restore and improve the River Crane, and pledged £400,000 to support this. As a result of this the Crane Valley Partnership agreed to employ an officer to develop and implement a plan of action over the next five years, with the bulk of the funding being available for river improvement projects.

Six months later however, we are still awaiting the formal start of this process and the latest expectation is that an officer will not be in place until the spring of 2013, a full 18 months after the pollution incident.


Whilst we have been pleased by the natural recovery of the river, FORCE has been frustrated over the last year by the slow pace of the authorities in delivering on their promises; and yet we remain hopeful that eventually this process will lead to long term benefits for the river. We look to the River Wandle as an example of what is possible, as a similar response there to pollution in 2007 led to the development of the Wandle Trust and an investment of several million pounds to date on the environmental and community value of this south London green corridor.

FORCE will continue to work with the other interested parties to improve the environmental value and resilience of the River Crane and to minimise the risk of a repeat of last year’s disaster. We will keep our members and the general public informed of progress and we plan to hold a public meeting in the New Year to review the situation.