BRISTOL FLOATING HARBOUR RECREATIONAL WATER PROFILE

Bathing water profiles are a requirement of the revised EU Bathing Water Directive 2006/7/EC and supporting regulations. The Floating Harbour is not designated as a bathing water because it is a multi-use area that includes navigation and flood defence. Swimming is prohibited through the bye-laws, however since the Harbour is widely used for recreational purposes throughout the year City Council has produced a profile for users. Advice for event organisers is available from the Harbour Office. The profile gives information about the water, pollution sources and improvements made to provide better water quality for all users.

BRISTOL FLOATING HARBOUR,

Local Authority: Bristol City Council Environment Agency Region: Wessex; Lower Bristol Avon Bristol City Council monitors and assesses the recreational water quality of Bristol Floating Harbour, throughout the year. The monitoring results are published on Bristol City Council’s website at http://www.bristol.gov.uk/page/water-quality www.bristol.gov.uk Recreational Water Map

Recreational Water Description

Bristol Floating Harbour is located in the heart of Bristol’s urban centre. It is a large man-made standing body of water fed by the River Avon and retained by lock gates at Cumberland Basin and Netham Lock. The harbour is predominantly fresh water with minimal saline intrusion from spring tides and locking operations at Junction Lock. The Floating Harbour is used for widespread recreational purposes throughout the year by various recreational clubs such as sailing, rowing, fishing and canoeing. Swimming in the harbour is strictly prohibited, unless special permission is obtained from the Harbour Master in advance.

2 Catchment Map

[Source: Bristol Avon Catchment Flood Management Plan, Environment Agency]

Severn Estuary

Bristol Floating Harbour

Catchment Description

The Bristol Avon catchment feeds the Bristol Floating Harbour and covers an area of approximately 2200km2. From the source, located north of Malmesbury, the Bristol Avon flows south and west taking in tributaries from the surrounding hills of the Cotswolds, Salisbury Plain and the Mendips before feeding into the harbour at Netham Lock. Tributaries, notably the Frome, River Chew, River Marden, Semington Brook, Tetbury and Sherston Avons and Brook all drain into the Bristol Avon upstream of the entrance to the Floating Harbour. The Bristol Frome enters the Floating Harbour at Castle Park or St Augustine’s Reach during times of peak flow after heavy rainfall, but under normal conditions is diverted to the River Avon New Cut via the Mylne’s Culvert. The catchment encompasses the two major cities of Bristol and Bath as well as diverse industry, varied agriculture and increasing tourism from the surrounding area.

3 Pollution Management

Water quality in the Bristol Floating Harbour is dependent upon the type and area of land draining to the water and the activities undertaken in the Bristol Avon catchment. There are many sources of potential contamination in this dynamic drainage system. The following sections give an indication of these potential pollution sources, conditions under which they may arise and measures put in place to improve the water quality.

Our Investigations

Bristol City Council works with the Environment Agency, Wessex Water, and the Health Protection Agency to investigate possible sources of contamination, improve water quality and provide health advice to recreational users. A long historical dataset on water quality is used to investigate water quality issues, provide trend analysis, and provide health advice to recreational users. The Floating Harbour is a complex system with different sources of contamination that can access the harbour at different places at different times and be of different origins. Most are dependent on heavy rainfall. Investigative work is ongoing to gather information to better understand the dynamic system that is the Bristol Floating Harbour.

Water Quality Sampling

Bristol City Council monitors water quality in the harbour for bacterial contamination all year round. Samples are taken throughout the harbour from Netham Lock to Cumberland Basin. Samples are analysed by accredited laboratories.

The current EU Bathing Water standard for bacterial contamination is 2000 cfu/100ml Escherichia Coli. Bristol Floating Harbour is not a designated bathing water and therefore these water quality standards do not apply. However, Bristol City Council uses a locally derived trigger value of 5000cfu/100ml Escherichia Coli to warn users of poor water quality and additional samples are taken daily until normal water quality returns.

Water quality sampling results are available online online at www.bristol.gov.uk/page/environment/water-quality

Rivers and Streams The rivers and streams upstream of Bristol Floating Harbour consist of a number of tributaries flowing through both rural and urban areas. The sewerage systems within the urban areas largely accept combined flows of foul sewage and storm water run-off. They are under increased pressure during times of heavy rain and flooding, and this can result in the discharge of diluted sewage into the smaller rivers and streams which feed the River Avon, which is the main source to the Harbour.

4 Bristol Avon The River Avon to the east of Bristol, flows directly into the Feeder Canal at Netham Lock and has a major influence on background water quality in the Floating Harbour. It is the main source of water to the Harbour.

The Avon has a number of potential pollution sources upstream. Discharges from the sewage treatment works at Saltford and Keynsham plus combined sewer overflows in east Bristol itself and towns such as Bath and Chippenham.

During heavy rain, flood water from the Brislington Brook is diverted at St Anne’s Terrace which is then discharged into the River Avon upstream of the harbour entrance at Vale.

Water from the Bristol Avon can only enter the western end of the harbour through the Junction Lock gates during locking operations which allow vessels to enter or leave or during a spring tide when tidal waters can over top the outer lock gates. These saline intrusions are thought to have minimal effect on water quality, but the impact on bacterial quality is unknown.

During spring tides, the incoming tide of the Bristol Avon can overtop the weir at Netham and enter the harbour at Netham Lock. On an incoming tide, discharges from Black Rocks (the Northern Storm Water Interceptor) and Ashton Avenue pumping station into the tidal River Avon could be incorporated into the flows into the harbour, albeit diluted by the huge volume of receiving waters.

After very heavy rainfall, when the River Avon is in spate, the gates at Netham Lock are often closed to prevent excess water coming into the harbour. This reduces the amount of background contamination from the River Avon entering the Harbour during this period. During heavy rainfall when flows in the River Frome are very high, much of the excess river water is diverted into the Northern Storm Water Interceptor at Eastville to reduce the flood risk to the city centre. This water is piped underneath the city and directly out into the Avon Gorge at Black Rocks, just downstream of the Suspension Bridge through the Northern Storm Water Interceptor.

River Frome

The River Frome to the north of Bristol is culverted just before it reaches the city centre. During periods of normal flow, the river flows through the Mylne’s Culvert, a tunnel which runs under the Floating Harbour, out into the River Avon (New Cut).

During heavy rain, when the Mylne’s Culvert is tide locked (blocked by the high tide), river water can back up and discharge into the Floating Harbour at St Augustine’s Reach and adjacent to Castle Park. It is this discharge into the Harbour during times of heavy rainfall, which is likely to be contaminated with dilute sewage from the combined sewage overflows located along the River Frome culverts underneath the city centre.

We can therefore anticipate that during times of heavy rainfall when the Mylne’s Culvert is tide locked, the River Frome is the primary source of contamination in to harbour waters as the Lock Gates at Netham are likely to be closed.

Surface run-off

Heavy rain falling on pavements and roads flows into surface water and highway drains within the central Bristol area, ultimately flowing into the Harbour. The quality of harbour water may be adversely affected as a result of such events.

5 Discharges from boats

Bristol Floating Harbour is home to a number of residential, leisure, commercial, heritage and visiting boats. Boat owners must adhere to the Bristol Docks Byelaws 2009, which requires that all boats must dispose of their waste water (sewage and grey water) correctly. However, some boat owners continue to discharge their sewage and grey water into the harbour illegally and pollute harbour water. A voluntary survey looking at the waste disposal from boats in the harbour took place in 2006. The survey established that of the 38% of boats that took part, 10.4% reported raw sewage was discharged into harbour waters as a means of disposal. Since the survey was undertaken, waste disposal facilities for boaters have been significantly improved with new pump out facilities located at Bristol Marina, the harbour Inlet, Mud Dock and Temple Back. Although disposal facilities have been improved, some boats may still discharge waste illegally into harbour waters. A mandatory vessel inspection survey of all boats moored in the harbour will take place in 2012/2013. Boat owners found to be discharging sewage will risk having their mooring agreements revoked or being fined.

Scouring and Dredging Operations In order to reduce the build up of silt in the Cumberland Basin, a procedure known as Scouring is undertaken approximately once a fortnight utilising the natural flow of the Bristol Avon. Lock gates are opened at both ends of the harbour drawing the water seawards. The water level in the harbour may be reduced by as much as 0.5m during a five hour period from the commencement of the scour. The scouring operation by its nature will re-suspend, mix and move both silt and water within the harbour environment. In addition to the frequent scouring operations, routine maintenance dredging is regularly undertaken to retain the navigational requirements of this working harbour. Water Injection dredging is the technique used to move the silt under gravity back into the River Avon through the Underfall Sluice gates. This process has been approved by the Environment Agency and the Marine Management Organisation (MMO). The impact of these operations on the quality of the harbour water and the flow rates through the harbour system are unknown. A study into the effect of scouring and dredging on water quality has been identified as an area of interest to understand how these navigational operations can impact the local environment.

Rats The urban sewers are a perfect breeding ground for rats. Rats harbour many bacteria and virus. Of most health concern is Leptospirosis (Weil ’s disease) that is excreted in rat urine. This contamination is minimised by regular baiting by Bristol City Council of sewers that connect to the Floating Harbour.

6 Wildlife

There are various water-bird populations such as swans, ducks and cormorants around the Floating Harbour. In particular many breeding seagulls in the Redcliffe area are attracted to the sources of waste food around the harbour. The faecal contamination from wildlife is thought to be minimal.

Working with Wessex Water

Sewage treatment works / outfalls

Wessex Water has worked with the Council and the Environment Agency over a long period to help make improvements to their sewerage infrastructure. Improvements have been carried out to local pumping stations, surface water outfalls and leaking sewers. Discharges from sewage treatment works have improved substantially in England and Wales since the 1980s. Wessex Water has undertaken significant improvements upstream on the Bristol Avon at Saltford and Keynsham sewage treatment works, and more locally at Ashton pumping station and Black Rocks in recent years. This has greatly improved the water quality in the Bristol Avon and therefore, the Floating Harbour. We will continue to work with Wessex Water and the Environment Agency to identify further areas for improvement and ensure that the sewerage infrastructure is sufficient for now and the future.

Emergency and storm overflows The majority of sewers located around the Floating Harbour are “combined sewers” and carry both sewage and surface water from roofs and drains. A storm overflow operates during heavy rainfall when the sewerage system becomes overwhelmed by the amount of surface water. The overflow reduces the risk of sewage from backing up pipes and flooding properties and gardens. An emergency overflow will only operate when something goes wrong, for example due to pump failure or blockage in the sewerage system. There are three combined sewer overflows which can discharge into the harbour during heavy rainfall. Two are located at Mardyke, Western Wharf but these discharge infrequently due to recent major infrastructure improvements undertaken by Wessex Water. The third is upstream of Temple Back and only discharges to the Harbour very rarely during a confluence of high tides, high flows in the river Frome and heavy rain.

Working with the Environment Agency

Drainage Misconnections

Modern sewerage systems have two separate systems, one takes foul sewage away for treatment to improve its water quality so that it can be safety discharged, the other takes rainwater runoff through surface water drains to rivers, lakes and the sea. Misconnections occur

7 when waste water pipes are plumbed into surface water drains instead of the foul water sewerage system. Misconnections can give rise to pollution when foul sewage water is discharged directly to the environment through a surface water drain. For example, a washing machine or toilet may be incorrectly plumbed so that it discharges to the surface drain rather than the foul sewage drain. Bristol Operation Streamclean is a partnership between the Environment Agency, Wessex Water and Bristol City Council that works to identify illegal drainage misconnections and organise correction to prevent further pollution to rivers, streams and Bristol Floating Harbour.

Farming community

The harbour is situated in the centre of an urban centre but can still be affected by rural sources of pollution upstream in neighbouring areas. The Environment Agency works with farmers to enhance farming practices, reduce run off from farmlands, and improve their understanding of pollution issues throughout the Bristol Avon catchment. The Agency’s ongoing work includes giving advice on good farming practice as well as offering farm visits and surveys of the area to identify potential contamination risks.

Algae

Cyanobacteria (blue green algae)

Blue green algae (cyanobacteria) occur naturally during the summer months and can pose a health risk to users and animals. There is no evidence of blue green algae in Bristol Floating Harbour.

Phytoplankton (microscopic algae)

Phytoplankton (microscopic algae) naturally increase in number at certain times of the year. This process is known as a phytoplankton bloom. There have been incidences of algal blooms within the harbour; however it is thought these blooms do not pose a risk to human health.

Working with the Health Protection Agency Bristol City Council works closely with the Health Protection Agency (HPA) to monitor and analyse the water quality of the harbour. The HPA has provided specific health guidance and advice for recreational users of the Floating Harbour, in particular for setting policy and conditions for the annual Bristol Harbourside Triathlon.

8 Further information Water Framework Directive

The EU Water Framework Directive (WFD) establishes a common approach to managing water within the European Community and aims to achieve ‘good’ water quality status for all water- bodies. The environmental objectives for the WFD will be delivered through the actions described in the River Basin Management Plans (RBMPs) and the Bristol Avon Catchment Management Plan. Actions identified in the RBMPs for other improvements, also contribute to improvements in bathing water quality. The River Basin Management Plans are published on the Environment Agency website. The Floating Harbour has not yet been classified for WFD purposes. Bristol City Council is working with The Environment Agency to get it included for designation in the second cycle.

About this document Written: January 2013 Next update: January 2014 We welcome feedback on this profile. Please contact us at the following address; Environment Team Sustainable City and Climate Change Service Bristol City Council CREATE Environment Centre Smeaton Road Bristol BS1 6XN Tel: 0117 3525894 E: [email protected]

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