Natural Resources Wales is investigating after almost 21 hours of storm overflow sewage was discharged over 48 hours during the Bank Holiday weekend at two North Wales beauty spots.

During the most recent Bank Holiday Llyn Padarn - a Site of Special Scientific Interest due to its marine life - was subject to 12 hours and 45 minutes of storm sewage discharge across Sunday and Monday, as hundreds of visitors were settling in for their half-term break.

Over the same period the River Ogwen saw eight hours of sewage discharge due to the heavy rain.

These outlets are the responsibility of Dŵr Cymru Welsh Water and are designed to ensure storm water in sewers does not back up into homes. But such lengthy periods of use - and the fact that they carry within them sewage and wastewater - have raised concerns about public and environmental safety as tourists return to the area.

Dŵr Cymru Welsh Water's own live online storm overflow map recorded the discharges and stated that the water company's High Spill Investigation programme is looking into the cases.

Both Llyn Padarn and the River Ogwen are also monitored by Natural Resources Wales to ensure water quality remains within acceptable safe ranges.

Euryn Roberts, Senior Environment Officer for Natural Resources Wales said it was aware of the discharges over the Bank Holiday weekend and is investigating.

"Keeping rivers and bathing waters clean and safe for people and wildlife is an important part of the work that we do," he said.  

"Following the recent heavy rainfall Dŵr Cymru has confirmed that there were storm discharges in the Bethesda area, which have now stopped. 

"We issue permits for storm overflows to regulate when they can discharge, to ensure they operate within the parameters set in the permit.

"We also received reports from a member of the public about possible recent discharges into Llyn Padarn and Llyn Nantlle. Both of these concerns are currently being investigated."

Llyn Padarn is owned by Cygnor Gwynedd. It said it had no concerns about the water quality after discussions with Dŵr Cymru Welsh Water. 

"We can confirm that we have been in discussion with Dŵr Cymru Welsh Water and there have been no concerns shared about a change in the quality of the water," said a spokesperson for Cyngor Gwynedd.

"Llyn Padarn is closely monitored by Natural Resources Wales and the water quality of the lake has been consistently good over the last few years." 

Dŵr Cymru Welsh Water said that it had plans to improve storm overflow management to reduce the potential impact in the area, but it was awaiting approval for the measures from the regulator. 

"We currently have plans for £30 million of investment on six projects to improve storm overflows and wastewater treatment works in this area for the next investment period, 2025-30, subject to Ofwat approval," Dŵr Cymru Welsh Water said in a statement.

"All of these are geared towards improving water quality and include an £8m project to reduce harm from the storm overflow at Nantlle No5.

"As a company, we take our responsibility for protecting bathing waters seriously and in the decade to 2025 alone we will have invested over £1.4billion in our wastewater system. This has helped ensure that Wales’ amazing coastline is blessed with a quarter of the UK’s Blue Flag beaches despite having just 15% of its coastline. 

"Llyn Padarn is Wales’ only designated inland bathing water and continues to meet ‘Excellent’ bathing water quality standards. The latest Bathing Water results also showed that 98% of the designated bathing waters meet stringent quality standards – with almost three quarters of them meeting the highest ‘Excellent’ water quality standard.  

"We are continuing to invest heavily in projects to improve the environment – with £200 million spent in the past year alone – as we follow through on the vision we set out when we published our River Water Quality Manifesto last year.

"This work is being done in challenging circumstances as we face the reality of climate change, with wet weather, extreme weather events and named storms becoming the new normal. 

"We know though how important water quality is to our customers, which is why we plan to invest £4bn, including £2.5bn on environmental projects, in our next investment period 2025-30."  

Natural Resources Wales encourages anyone concerned about incidents that may impact the quality of rivers and bathing water to call their incident hotline on 0300 065 3000 or fill out their online ‘report it’ form at