However the plan which would extend the gallery into parkland will require 18 large trees to be chopped down.

Orange City Council has been recommended to approve a development application for the work at its meeting on Tuesday night.

A report to the council said the extension would create increased gallery, artwork conservation and storage space, a new 75-seat theatre, a loading dock, plant room, a lobby and corridors.

"The proposed development will further enhance social, cultural and educational facilities within the civic precinct of the city," it said.

"The key planning issues identified in the staff assessment report relate to tree removal, off-street car parking, contamination and urban design."

It said the 18 trees included river she-oaks and their removal was "not considered an ideal planning outcome."

However the report argued the public benefit achieved by the new development would 'counterbalance' the removal of the trees.

It said replacement trees would be planted around the gallery site.

The report also states increasing the building by the size proposed should involve demand for an extra 20-44 off-street car parking spaces, but none will be provided.

It said council staff accepted the expansion will not greatly increase visitor numbers and big events, such as exhibition openings, usually occurred outside of business hours.

The report said there was sufficient parking available in the nearby council car park. It also said a new car park was proposed to be located opposite the North Court in Peisley Street.

The proposed theatre will also be restricted to gallery-related activities.

The theatre would be used during exhibition openings, for audio-visual exhibitions and for lectures and talks by artists.

The building's design will feature four rectangular shapes fronting Peisley Street with a solid wall facing into the Northcourt.

A planetarium and the new home for the Orange Conservatorium have been proposed to take up space nearby.

The report said there were no heritage, Indigenous-heritage related or environmental reasons to oppose the development.

It said while the trees would be removed the plan would not harm the environment in the area.

"The land is not located in an area of high biodiversity value. The land is a highly disturbed urban environment," it said.

"The development is not likely to give rise to any significant impact upon any endangered ecologically community, threatened species or their habitat."

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