Concern over NRW assessment of Llanberis hydro power site
Concerns have been raised over a decision to award environmental permits to a planned hydro power plant in Llanberis, Gwynedd.
Natural Resources Wales (NRW) gave Snowdonia Pumped Hydro (SPH) permission to empty standing rainwater from two disused quarries at Glyn Rhonwy into Nant y Betws and Llyn Padarn.
But the Snowdonia Society has criticised its assessment of the site.
NRW said it was "confident in its permit decision."
The plans for the £100m hydro plant are being considered by the UK Planning Inspectorate, with a decision expected this month.
The society has written to the Secretary of State for Business, Energy and Industrial Strategy (BEIS), Greg Clark to raise concerns over NRW's decision to grant the permits under its statutory powers.
The letter, seen by BBC Wales, said: "We believe there is doubt whether NRW has exercised its consultee responsibilities properly in this case."
In its decision document NRW said: "A full assessment of the application and its potential to affect the site, protected species and protected habitats has been carried out as part of the permitting process."
But the society called this "demonstrably incorrect."
It said the developer's assessment of the water to be discharged from the quarries was based on a small number of samples, with none from the silt residues at the bottom of the pits.
The Snowdonia Society director, John Harold, said: "We are appalled that the NRW has not required the developer to collect a full suite of samples.
"NRW has failed to take a precautionary approach, and also, appears to have ignored concerns expressed by its own internal consultees."
Sian Williams, NRW head of operations in north west Wales said they only issue an environmental permit "if they are satisfied that the company's plans prove they will operate safely, without harming the environment or local communities".
"We are confident in our permit decision as explained in the decision document found on our website," she said.
Ms Williams added: "Llyn Padarn is a vitally important natural asset for the area. It's important for wildlife, for people and the local economy.
"We have offered Snowdonia Society an opportunity to discuss this decision with us."
There are also concerns that the pits contain unexploded munitions, as the area was home to a former RAF ammunitions store that was cleared in the 1970s.
Mr Harold added: "The body which should protect the environment of Wales is in effect passing the buck to planners" and has left the Department for BEIS to "deal with the complex environmental risk assessment for munitions and their residues at Glyn Rhonwy".
A BEIS spokesperson said: "The government recognises the potential for storage technologies, including pumped hydro, which is why we have worked with other organisations to invest more than £80m in research and development since 2012, and are actively seeking to remove barriers to the industry.