The impact of thousands of newly routed flights over Richmond Park has been almost completely ignored in Heathrow airport’s environmental impact report on its plans for a third runway, campaigners have said.

As the consultation on Heathrow’s expansion approached closure on Friday, environmental campaigners said the effect of the expansion on the biodiversity, tranquility and environment on the park had yet to be properly addressed.

Richmond Park, established in the 17th century, is a site of special scientific interest and a national nature reserve stretching over 1,000 hectares (2,470 acres). The Friends of Richmond Park group is demanding the airport carries out a full environmental impact assessment of the expansion on the park.

Documents prepared for the Heathrow airspace and future operations consultation, which follows MPs’ approval of the third runway last year, indicate that 47 arrivals an hour and between 17 and 47 departures would fly directly over the park at below 900 metres. Heathrow’s flights are currently capped at 480,000 a year and it wants to increase this by 25,000 in 2021 and further when the third runway is built.

Environmental campaigners say the noise and pollution would be disastrous for the sensitive wildlife and the tranquillity of an area visited by more than 5.5 million people a year. They say thousands of nocturnal animals in the park would be threatened, including 11 of the UK’s 17 bat species, all of which are protected by law, as well as little and tawny owls.

Richard Gray, of Friends of Richmond Park, said: “In spite of the importance of Richmond Park and the impact of the expansion on it, the park is almost completely absent from the preliminary environmental information report in the expansion consultation documents.

“Where Richmond Park is covered, some of results are just not credible. The noise increase from 47 arriving aircraft per hour and a big increase in departing aircraft is estimated to be only 1 to 3dB. For tranquility, the park is mentioned specifically as having ‘relative tranquility’ but the impact of the proposals is expected to be negligible/slight – a strange conclusion when the proposals are for noisy flights over the quietest place in London.

“The charity demands that Heathrow include a proper assessment of Richmond Park in the full EIA/ES [environmental impact assessment/environmental statement]. Without that, the inspector will not have all the relevant material available to make a fully informed decision and Heathrow may face a legal challenge.”

Green campaigners have been granted the right to continue their legal action against the expansion in an appeal next month. The legal challenge has been brought by the mayor of London, Sadiq Khan, Friends of the Earth, Greenpeace and local authorities.

Boris Johnson, who as a backbench MP threatened that he would lie down in front of the bulldozers to stop the expansion, has hinted that he will follow the court challenge with lively interest.

MPs approved the Heathrow expansion plans by a margin of 415 votes to 119 last June.

Heathrow airport has been contacted for comment.