2019 Bathing Water Profile for Polstreath
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Polstreath is on the south coast of Cornwall. It is a remote sandy beach, approximately 330 metres wide, backed by cliffs and accessed by a coastal path.
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Cornwall
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Cornwall
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There is a storm/emergency overflow from the Mevagissey pumping station, that discharges to the sea approximately 420m south of the bathing water. The operation of the overflow can lead to a temporary drop in bathing water quality.
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The South West Water scheme for Menagwins (St Austell) sewage treatment works (STW), which provides secondary treatment and ultraviolet (UV) disinfection, was completed in 1996, on a trial basis. The continuous untreated discharge at Mevagissey was transferred to Menagwins STW in 1997, and following completion of the trials, the UV system was permanently installed in early 1998. Improvements were made to the sewerage network in Mevagissey in 1999 which have reduced saline infiltration and flooding problems at both Mevagissey and Menagwins. Improvements were made to the storm discharges Menagwins STW in early 2000. Storm overflow event duration monitoring (EDM) was installed at Mevagissey pumping stations by April 2011.
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For the four year (2015-2018) assessment period where data is available, seaweed (macroalgae) was assessed as being sufficient to be objectionable for 4% of visits, with 82% of visits noting the presence of seaweed (macroalgae). This bathing water does not have a history of large amounts of seaweed (macro algae).
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For the four year (2015-2018) assessment period where data is available, phytoplankton (microscopic algae) was not noted at this site. Phytoplankton (microscopic algae) naturally increase in number at certain times of the year. This process is known as a phytoplankton bloom. This bathing water does not have a history of phytoplankton blooms. The risks to human health from contact, ingestion or inhalation with marine algae that currently occur in UK coastal waters are considered to be low. However, some individuals may be more sensitive and display some reactions. A common marine algae found in UK coastal waters is Phaeocystis, which is often mistaken for sewage as it forms foam and a brown scum, but it is non-toxic.
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2019 Bathing Water Profile for Polstreath
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2019-09-30
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2019-05-01
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Sewage from the Polstreath area is pumped to Menagwins (St Austell) STW for treatment via the Mevagissey pumping. The outfall from Menagwins (St Austell) STW discharges to the St Austell River. This discharge is disinfected and designed to protect bathing water quality.
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Environment Agency samplers make observations of litter present on the beach at every visit, this includes assessments of sewage debris, litter and tar. At Polstreath for the four year (2015-2018) assessment period where data is available, sewage debris was not noted at this site. Litter was not assessed as being sufficient to be objectionable, but was observed as being present on 40% of visits. Tarry residue was not noted at this site.
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There are around 10 farms in the bathing water catchment. During and after periods of heavy rainfall, runoff from agricultural areas to the Mevagissey Stream is greatly increased, and the quality of the bathing water may be reduced.
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The catchment surrounding Polstreath is approximately 560 hectares. There is a tiny stream 360m long which flows onto the beach, and the Mevagissey Stream enters the sea at Mevagissey Harbour 500m south of the bathing water. The catchment of the Mevagissey Stream includes several tributaries totalling eight and a half kilometres (km) which merge to the main stream at various points along the valley. The steep catchment means rain runs off rapidly into the stream. Land use is agricultural, with around 20 farms which are mostly beef, sheep, and some arable. The popular tourist attraction of ‘The Lost Gardens of Heligan’ is in this catchment, which is also partly within the Cornwall Area of Outstanding Natural Beauty (AONB).
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Polstreath
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Polstreath
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Sampling point at Polstreath
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201710
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50.27436607251723
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-4.78420121717727
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45310
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Sampling point at Polstreath
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p152 dT23 h59 m59 s
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2019 05 01 t00:00:00
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2019-05-01T00:00:00
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2019 09 30 t23:59:59
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2019-09-30T23:59:59
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2019 28000:1
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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.
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The majority of sewers in England 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.
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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.
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It is the Environment Agency role to drive improvement of water quality at bathing waters that are at risk of failing higher 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.
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Discharges from sewage treatment works have improved substantially in England since the 1980s.
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