The beach lies at the mouth of the Afon Colhuw, to the South West of Llantwit Major, rocky in places there is a shingle bank with sandy areas at low tide. The bay is backed by steep sandstone cliffs facing south westerly towards the Bristol Channel. Colhuw beach lies in the middle of the Glamorgan Heritage Coast, with the Wales Coastal Path extending along the top of the beach. The valley either side of the lower reaches of the river is designated as a Site of Interest for Nature Conservation and the Cwm Colhuw Nature Reserve extends along the southern slope of the Afon Colhuw. Natural Resources Wales’s designated sample point is located at the centre of the beach.
As a beach which has recently been designated, Natural Resources Wales will work to establish any sources of pollution around Colhuw beach, this work is carried out in partnership with the Vale of Glamorgan Council. Investigations are also undertaken during the season when necessary, such as where there are elevated bacterial results in the bathing water that cannot be simply explained due to weather conditions.
When the capacity of Llantwit Major treatment works is reached during wet conditions, storm sewage is firstly stored in a large tank, once this is full there can be a discharge of storm sewage via the sea outfall. Once the capacity of this discharge is reached there is an additional overflow to the Afon Colhuw approximately 850m upstream from Colhuw beach.
In recent years, telemetry equipment called Event Duration Monitoring (EDM) has been installed in all the overflows by the water company Dŵr Cymru Welsh Water (DCWW). This technology has allowed them to respond to warnings of blockages in the sewerage system and has reduced the number of actual and potential spills. The data collected is reported to NRW as part of requirements to monitor and reduce the numbers of spills.
Natural Resources Wales has developed a good working relationship with Dŵr Cymru Welsh Water and liaises with them regularly to identify problems that could affect bathing water quality.
Natural Resources Wales and the Vale of Glamorgan Council working together to maintain and improve the bathing water quality at across the Vale.
Inspections are carried out jointly by Natural Resources Wales and the Local Authority before the Bathing Water season starts on the 15th of May, usually these visits are done with the water company as well where applicable.
Heavy rain falling on pavements and roads often flows into surface water drains or highway drains, ending up in local rivers and, ultimately, the sea. The quality of bathing water may be adversely affected following such events.
Modern sewerage systems have two separate systems, one takes foul sewage to sewage treatment, the other takes rainwater runoff through surface water drains to rivers, lakes and the sea. Misconnections occur when wastewater pipes are plumbed into surface water drains instead of the foul water sewerage system. This can give rise to pollution when the wastewater is discharged directly to the environment through the 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.
Phytoplankton (microscopic algae) naturally increase in number at certain times of the year. This process is known as a phytoplankton bloom. These algal blooms can occur at any beach during the bathing season and are usually noticeable by a surface scum. Beaches along the South Wales coast are known to have blooms which can wash ashore from time to time.
Streams and rivers are typically affected by sewage or run off from further up the catchment. During and after periods of heavy rainfall, run off from agricultural and urban areas will be greatly increased. Colhuw beach is influenced by the freshwater input from the Afon Colhuw which runs along the side of the car park and flows onto the beach through the shingle bank by the slipway. The river may impact bathing water quality at Colhuw beach particularly following periods of heavy rainfall.
There is public sewerage infrastructure in Llantwit Major and surrounding areas, some properties in the wider catchment have private sewage treatment arrangements.
Treated effluent from the public sewage works in Llantwit Major at outfalls to the sea around 800m East of the beach, this receives disinfection with ultraviolet treatment prior to discharge to the sea. There are also coastal discharges at Aberthaw approximately 6km to the East, Marcross approximately 4km West and St. Donats approximately 2km West of Colhuw beach.
Colhuw beach could potentially be impacted by storm, emergency and surface water outfalls, particularly during heavy rainfall when these discharges can result in a deterioration in the quality of the water in the catchment intermittently.
Natural Resources Wales samplers make visual observations of the beach at every visit. This includes assessments of sewage debris, animal faeces, litter and oil or tar. At Col-Huw Beach (Llantwit Major), data are available for the two year assessment period 2023. Sewage debris was observed in trace amounts on less than ten per cent of occasions. Trace amounts of animal faeces were noted at the site on a minority of occasions. Trace amounts of litter were observed at the bathing water the majority of the time and in greater amounts on less than ten per cent of occasions. Oil and tarry residues were not noted at this site.
Areas of pastureland occupied by livestock feature in the rural areas of the catchment. Farms are inspected according to their level risk of polluting the bathing waters. Natural Resources Wales will work with the local farming community to identify activities that are detrimental to Colhuw bathing water and to amend practices to protect water quality.
Poorly maintained private sewage treatment facilities could be a source of pollution, therefore the registration of all private sewage systems in Wales was required by 30 June 2012. The primary aim of this exercise was to provide increased protection for the environment and sensitive features such as bathing water beaches. Where properties are identified in the catchment that are not on mains sewerage, Natural Resources Wales will endeavour to ensure registration has been made.
Natural Resources Wales works with private owners to identify and mitigate potential pollution sources to bathing waters, this work involves where necessary, advisory mail drops, dye tracing, misconnection surveys and meetings. We welcome any comments or information from the public about environmental pollution.
The natural drainage (hydrological) catchment of the Afon Colhuw surrounding the bathing water drains around 18 square kilometres. It comprises of the Boverton Brook and Llanmaes Brook forming the Hoddnant in the East, and the Ogney Brook in the West becoming the Afon Colhuw at the Southerly point of the town. Land use is typical for the Vale of Glamorgan mainly rural with mixed agriculture and more urban areas with the St. Athan airfield, areas of light industry and the conurbation of Llanmaes, Boverton and Llantwit Major.
Seaweed (macroalgae) and phytoplankton (microscopic algae) are a natural part of the marine and freshwater environment. Below we note whether these have been recorded in quantities sufficient to be a nuisance.
The majority of sewers in Wales 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 prevents sewage from backing up pipes and flooding properties and gardens. An emergency overflow will only operate infrequently, for example due to pump failure or blockage in the sewerage system.
Heavy rain falling on pavements and roads often flows into surface water drains or highway drains, ending up in local rivers and, ultimately, the sea. The quality of bathing water may be adversely affected as a result of such events.
It is Natural Resources Wales' role to drive improvement of water quality at bathing waters that are at risk of failing European standards. It is natural for water to run off the land to the sea. Water quality at a bathing water is dependent upon the type and area of land (the catchment) draining to the water and the activities undertaken in that catchment. The following sections serve to highlight potential sources of pollution, conditions under which they may arise and measures being put in place to improve water quality.
