"Once completed, stage one of the project will strengthen the main body of the church while ensuring the tower will pose no risk to life in a severe earthquake," he said.
Work on stage one was able to go ahead after $230,000 was donated or pledged to the church, while stage two would cost around $100,000 and would start as funding became available, he said.
"Further fundraising will be necessary before the tower can be completely strengthened as part of stage two of the project, but the church can be reopened at the completion of stage one regardless," he said.
Sutherland hoped the church would be ready for a reopening ceremony on St Mary's Day, on August 15.
For members of the local subcommittee, that would bring a partial end to a long ordeal that has included an eight-month setback after a spike in estimated costs for the project.
After the church was closed by the standing committee of the Diocese of Waiapu at Easter in 2014, the subcommittee was formed and, in September of 2016, it obtained a detailed seismic assessment from an Auckland-based engineering firm which found the church could be brought up to the minimum rating for around $250,000.
The subcommittee then began a fundraising drive and, seven months after banking its first donation, it had successfully raised more than $200,000 - enough for the strengthening work to begin and for the Waiapu Board of Trustees to grant permission for the work to go ahead.
However, after having detailed designs drawn up based on the initial proposal, the subcommittee members were "horrified" to receive an estimate for $550,000.
After approaching Win Clark, consultant engineer for the Historic Places Trust, now Heritage NZ, to peer review the documentation, he suggested completing the work in two stages to reduce costs.
That allowed the subcommittee to amend the original plan to make it viable, with a signed contract put in place in February this year for the work to start.