A plan has been proposed for Government House to address concerns about potential damage to Black Watch Pass.

The draft voluntary Conservation Management Plan called for the removal of invasive and pest plants from the western border of the property in an effort to prevent their root systems from eroding the nearby cliff face.

Planning documents stated that the applicants were aware of two noteworthy events in the past 18 months at the site that highlighted the problem in the area.

“On or before October 13, 2023, there was a rockfall from height approximately 40 to 50 feet involving approximately ½ to one cubic yard of pieces of bedrock and sand,” the documents said.

“There would have almost certainly been quite large pieces of stone that fell and a fair amount of the debris travelled as far as across the road and on to the far sidewalk.

“The other event was a dead casuarina, maybe a 15 to 20-footer with an approximate eight to 10-inch trunk, hanging almost completely vertically, upside down, over the edge and was more than likely being held by some of its dead roots atop the verge approximately 30 to 40 feet up.”

The documents said that while the area was subject to a previous CMP, submitted in 2014, it was not managed in accordance with its recommendations, causing the area to become overrun with invasive species including Mexican pepper, casuarinas and several Indian laurels.

“These are all Category 1 invasives,” the documents said. “These three are fast-growing woody trees with extremely aggressive root systems.

“As time progresses, the number of instances/occurrences of rockfall and fallen casuarinas will only increase.”

The proposal called for the cutting of paths to the clifftop verge wide enough to accommodate the necessary equipment before removing all vegetation within ten feet of the clifftop and all invasives within 20 feet of the cliff.

Native and endemic plants close to the cliff face would be replanted elsewhere on Government House grounds where possible, with a list kept of all native and endemic plants that cannot be saved.

“A planting scheme will be undertaken under the advice and guidance of the Department of Environment and Natural Resources, co-ordinated with Government House, and will be the subject of a separate contract,” the documents added.

The project would require some scaling works that will require the closure of Blackwatch Pass for “periods of currently unknown duration”.