The underground reservoir is covered in vegetation
Plans to build almost 100 homes at a reservoir have been rejected because the scheme would have had a detrimental impact on deer and breeding birds.
Thames Water hoped to sell its Bath Road site in Reading to developers with planning permission for houses.
At a meeting on Wednesday, councillors revealed they rejected the water firm's plans for 12 reasons, which included ensuring the wildlife was protected.
Thames Water said it was "disappointed" it is considering an appeal.
More houses needed
Opponents had argued the 5.4 acre (2.2 hectare) underground reservoir, which is covered in vegetation, was a "green lung" for the town.
The council also received more than 400 letters of protest in opposition.
The proposal was unanimously rejected in a vote by councillors who voiced a variety of concerns including that the development "would result in the loss of an area of lowland mixed deciduous woodland and the loss of large numbers of important trees on the site".
The councillors also predicted the proposed extension to the Grade II Listed water tower would, because of its "bulk and inappropriate use of materials", be an "unsightly addition to the tower [and] of detriment to its character and setting".
The number of flats - 40% - was considered excessive because the borough has "a most pressing need for two and three bedroom semi-detached or terraced family houses with gardens".
Councillors also revealed the application did not demonstrate fully that the homes would be energy efficient in compliance with Code for Sustainable Homes standard.