Snowy Hydro, developer of the proposed multi-billion dollar pumped hydro scheme, has sought fast-tracked environmental approval for pilot works that would disturb 114 hectares of a national park and excavate about 750,000 cubic metres of rock.

The company, now fully owned by the Commonwealth, is seeking to avoid having exploratory works related to the so-called Snowy 2.0 project declared a controlled action by the federal environment department, according to its lodged claim. Controlled actions involve closer environmental scrutiny and could delay the venture.

Snowy wants to carve out 236 hectares of the Kosciuszko National Park – 114 hectares of which it would disturb – in order to drill to determine rock conditions for an underground power station. This stage could turn out to be "one of, if not the most, challenging areas for the design of Snowy 2.0", the corporation said.

Paul Broad, Snowy's chief executive, told Fairfax Media the proposed works had been "designed in a way that avoids and minimises environmental impacts wherever possible".

The steps include choosing a road access route that avoided effects on identified threatened species, such as the smoky mouse. External experts "believe the exploratory works avoid significant impacts to matters protected under the [Environment Protection and Biodiversity Conservation] Act", he said.