Sewage pollution and faecal bacteria found in Roath Park Lake

Sewage has been polluting Roath Park Lake for years according to tests showing high levels of bacteria found in human faeces.

Recently revealed emails show that ‘unauthorised sewage discharges’ are polluting water in the lake and nearby brooks.

The faecal bacteria could also explain why toxic blue-green algae has kept coming back to the lake.

Emails sent by Cardiff council staff about water quality were published in April, in response to a freedom of information request. The request was first made in March 2019, but the council took more than a year to answer.

In an email from April last year, an unnamed officer in the parks department said: “We are aware that Roath Park lake and other watercourses in the area do have some issues with unauthorised sewage discharge.

“Welsh Water is aware of the situation, but to date the problem has not been resolved.”

Councils must routinely monitor bathing waters for bacteria that indicates faecal pollution, under EU law. However, Roath Park Lake isn’t designated as a bathing water and was last analysed in 2013.

In an email from March last year, an unnamed officer in the council's environment department said: “Samples were last analysed from the site in 2012 and 2013, and these indicated that bacterial levels within the waterbody were far in excess of recommended limits for immersion activities in freshwaters.”

Tests from November 2012 found faecal coliforms and faecal streptococci in the lake — two types of bacteria found in human faeces.

Inspectors measure faecal bacteria by the number of colony forming units per 100 millilitres (cfu/100ml). Safe levels for bathing are considered anything less than 900 coliforms and 330 streptococci.

At the north end of the lake, inspectors found 25,000 cfu/100ml faecal coliforms and 6,200 faecal streptococci. That is nearly 30 times safe bathing levels of the coliforms.

In the middle of the lake, they found 2,000 coliforms and 883 streptococci. At the south end, they found 530 coliforms and 63 streptococci.

The results show sewage pollution is coming into the lake, the email in March said, but the pollution is reducing as the water flows downstream and is exposed to UV light from the sun.

The email also explained that the blue-green algae that keeps coming back to the lake could be linked to the sewage pollution. The unnamed council officer said: “The repeated occurrence of these blooms further suggests a high nutrient load from upstream of the lake, which is usually associated with sewage inputs.”

Now there are calls for the council and Welsh Water to act on the problem.

Rodney Berman, Liberal Democrat councillor for Penylan, said: “Liberal Democrat councillors have repeatedly called for the Labour-run council to address the issue [of toxic blue-green algae], but the city’s leaders seem to be continuing to neglect this jewel in the crown of Cardiff’s parks.

“Pollution in the lake could be a contributory factor and if there has been unauthorised discharge of sewage into the lake, then that is clearly something that needs to be looked into. The council needs to work with Dŵr Cymru/Welsh Water to address this as part of their investigation into what could be done.”

Roath Park lake was first formed when a dam was built across the Roath Valley and Nant Fawr brook. It was filled with water in December 1893, and soon after swimming in the lake was popular.

In summer 1928 an outbreak of dermatitis among bathers was traced to a parasite infecting snails living in the lake. The council killed the snails with dilute copper sulphate, and people then carried on swimming. Further concerns about the water quality between 1948 and 1955 led to repeated closures.

Swimming in water with a lot of faecal bacteria increases the chance of contracting diseases and illnesses like typhoid fever, hepatitis, gastroenteritis, dysentery and ear infections, according to the Water Research Centre.

The council monitors the lake daily for blue-green algae and said there is none at the moment. A spokesperson said the pollution could be from misconnected sewers — where wastewater is released directly into rivers and streams.

The council spokesperson said: “Currently there is no evidence of blue-green algae being present in Roath Park lake, but we are monitoring the site on a daily basis. If this naturally-occurring algae does return then the necessary safety steps will be taken.

“The presence of pond weed in the lake demonstrates that water quality is generally good. However, we understand there are some long-term issues with unauthorised wastewater discharge entering the watercourses that feed the lake.

“It is over 50 years since problems with the water quality in Roath Park led to the prohibition of swimming in the lake and we would continue to remind people to stay out of the water.

“The wastewater network is the responsibility of Welsh Water, not Cardiff council, and we understand that survey work is being carried out to identify any potential misconnections that could be related to this issue.”

A commercial property upstream from the lake has misconnected sewers, according to Welsh Water — but the water company would not reveal where the property is.

A Welsh Water spokesperson said: “As a company so closely linked to the environment, we are very aware of the impact our work has on our surroundings and take our environmental performance very seriously. While the presence of blue-green algae is naturally occurring, and not a reflection of poor water quality, any report of its presence is investigated when raised with us, together with the local authority.

“Incidents of pollution into Roath Brook have been primarily due to illegal misconnections to surface water drains – which are designed to take rainwater from the urban areas to watercourses, which in this case flow into Roath Lake. These illegal connections are made from either domestic or commercial sources and enter into the drainage network and then a watercourse. We work hard to work with businesses and individuals to raise awareness of the dangers of misconnected sewers and potential harm this does to the environment.

“While Roath Park Lake is not a bathing water, and the council does not permit bathing in it, we have worked in partnership with Natural Resources Wales and the local authority to help identify and locate the source of this misconnection to a commercial property, and to ensure this can be addressed.”