Porthallow is on the south coast of Cornwall. It is a remote pebble and shingle beach,
approximately 150 metres wide, surrounded by hills. A stream flows onto the beach.
The emergency/storm overflow from the Porthallow STW, that discharges to the Porthallow
Stream approximately 80m upstream of the bathing water. The operation of the overflow
can lead to a temporary drop in water quality in the Porthallow Stream and Porthallow
bathing water.
The sewage treatment scheme for Porthallow which provides secondary treatment and
ultraviolet (UV) disinfection, was completed by South West Water in early 2000. A
total of around 60 homes, including all the houses that used to discharge to the Porthallow
Stream, are now connected to the STW. Storm overflow event duration monitoring (EDM)
was installed at Porthallow pumping station by April 2011.
For the four year (2020-2023) assessment period where data is available, seaweed (macroalgae)
was assessed as being sufficient to be objectionable for 24% of visits, with 71% of
visits noting the presence of seaweed (macroalgae). This bathing water does not have
a history of large amounts of seaweed (macro algae).
For the four year (2020-2023) assessment period where data is available, phytoplankton
(microscopic algae) was assessed as being sufficient to be objectionable for 2% of
visits, with 0% of visits noting the presence of phytoplankton (microscopic algae).
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.
This bathing water is subject to short term pollution procedures. The Environment
Agency makes a daily pollution risk forecast at this site based on the effects of
rain, wind and sunlight on bathing water quality. These factors affect the levels
of bacteria that get washed into the sea from livestock, sewage and urban drainage
via rivers and streams and how they disperse.
When these factors combine to make short term pollution likely we issue a pollution
risk warning on this website and the beach manager will display a sign advising against
bathing at the bathing water. After a short term pollution event, levels of bacteria
typically return to normal after a day or so but it’s possible to have several warning
days in a row. Details of the work to reduce the sources of bacteria at this bathing
water are detailed in this profile.
In 2023 1 pollution risk warnings were issued for this bathing water.
All bathing waters have the potential to be affected by a pollution incident and if
this occurs a pollution risk warning will be issued with associated advice against
bathing on this website.
Streams and rivers are typically affected by human sewage, animal slurry and runoff
from roads. The Porthallow Stream flows onto this beach. The Environment Agency have
monitored the stream between 1986 and 2014, and found that water quality is temporarily
worse during and after heavy rainfall.
The outfall from Porthallow STW discharges to the Porthallow Stream approximately
400m upstream of the bathing water. This discharge is disinfected and designed to
protect bathing water quality.
Environment Agency samplers make observations of litter present on the beach at every
visit, this includes assessments of sewage debris, litter and tar. At Porthallow for
the four year (2020-2023) 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 35% of visits. Tarry residue was not noted at
this site.
There are 10 farms in the catchment, most of which are arable. During and after periods
of heavy rainfall, runoff to the Porthallow Stream from agricultural land is greatly
increased, and the quality of the bathing water can be reduced.
The catchment surrounding Porthallow is approximately 650 hectares. The Porthallow
Stream (including tributaries) is approximately seven and a half kilometres long and
enters the sea at Porthallow beach. The steep areas in the middle of the catchment
mean rain runs off rapidly into the stream. Land use is mainly agricultural, with
around 10 farms, a mixture of improved grassland, arable and some woodland.
The catchment is located in the Cornwall Area of Outstanding Natural Beauty (AONB).
It is next to the Fal and Helford Special Area of Conservation (SAC) and Meneage Coastal
Section Site of Special Scientific Interest (SSSI).
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 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.
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 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.
