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St Aubin water safety assurance

30 September 2016

​The Department of the Environment (DoE) has the following points to make in response to Save Our Shoreline’s (SOS) comments made in the media and the summary of the report it has seen.

Safety of St Aubin’s Bay

In respect of nitrates, nitrite, ammonia and hydrogen sulphide, St Aubin’s Bay is safe to use and swim in. The DoE samples the quality of bathing waters every week during the bathing season and the level of ammonia and nitrates found in the bay are insufficient to cause concern to human or animal health. The level of hydrogen-sulphide has also been sampled and was found to be negligible.

However, as a general guide for any stream/outfall around Jersey, the Department re-affirms its previous advice that people should not wade or play in outfalls, as these can potentially carry pollutants washed from the land, particularly following periods of heavy rain.

Sewage Treatment Plant

The DoE regulates the discharge entering St Aubin’s Bay from the Sewage Treatment Works under the Water Pollution (Jersey) Law 2000. The Department for Infrastructure (DfI) operates the plant and must abide by the conditions set out in the discharge permit issued to it by DoE.

The DoE maintains robust independent regulation of the sewage works. Working alongside DfI, it has undertaken extensive and wide-ranging sampling and research in St Aubin’s Bay according to strict protocols over a number of years. This research helps both the regulator and operator to make informed decisions based on robust scientific evidence. This information is made available to the public (including SOS) when it is published on the States of Jersey website.

It is well known that the sewage treatment plant is old and failing the total nitrogen limit specified by the discharge permit. Regulatory action has been taken in accordance with normal procedures. While extensive sampling and testing in St Aubin’s Bay suggests that the levels of nitrogen measured could be contributing to the growth of green seaweed in the bay, the levels are insufficient to cause concern to human or animal health.

Part of the solution to reducing the nitrogen levels associated with the sewage treatment plan is to replace the plant. The States has agreed funding, and a replacement plant is being planned by the operator (DfI) and will be operational in 2021. As well as partially addressing the nitrogen levels, the new plant will cater for an increased island population, require less electricity to run and have many other benefits.

Water Management Plan

It has long been recognised by all parties that controlling nitrates at source is the best solution to addressing nitrate levels found in our sea water, streams and groundwater.

While the sewage treatment plant contributes to nitrate levels in the bay, run-off from land also contributes to the problem in equal volumes to that of the sewage treatment plant, as do nitrates from the wider marine environment.

The DoE has successfully worked with farmers and landowners for some years to better manage the use of fertilisers and manures applied to land, so as to reduce levels of nitrates found in streams and groundwater. Nitrate levels in streams and groundwater, and hence levels flowing into the bay, are reducing.

The DoE is due to publish a Water Management Plan and present this to the States of Jersey later this year. This will include a number of important initiatives and measures to further reduce levels of nitrates from land based sources.

Solutions to the Sea Lettuce (Green Seaweed)

While reducing the level of nitrates discharging into St Aubin’s Bay from the sewage treatment plant and from land run-off may reduce the amount and frequency of sea lettuce events, the solution to this problem is more complicated.

The Bay provides an ideal environment for sea lettuce to thrive, and prevailing winds and currents cause the weed to accumulate in certain areas of the Bay. Whilst there are background levels of nitrates in the wider Bay of St Malo, the majority of nitrates in the nearshore area results from run-off from the land and the sewage works. There is unlikely to ever be a solution that completely eradicates sea lettuce from the bay.

The States welcome ideas and initiatives from SOS and other organisations that may lead to a solution to the sea lettuce issue. Any solution will need to consider the environmental impact on the bay and be based on sound scientific evidence.

Tony Legg (referred to in the SOS report) is in discussion with DoE and DfI in relation to his proposals, including the possibility of setting up an oyster farm. Consideration will need to be given to safeguarding the delicate ecosystem that exists in the bay.

SOS Report

The research and sampling methods carried out by SOS are unclear and limited. Monitoring and modelling carried out by the DoE and DfI is extensive and scientifically robust.

It is a concern of the Department that some of the report conclusions are unduly alarmist and not supported by evidence. The evidence is certainly not at a level that we, as regulators and scientists, are required and expected to achieve in order to make decisions to protect the environment on the public’s behalf.  

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