Canada-based Lucara Diamond Corp has pushed out the completion date for its underground expansion project (UGP) at the Karowe mine, in Botswana, by a year-and-a-half and increased its capital cost to reach completion by $136-million.

The UGP, which is designed to access the highest value portion of the Karowe orebody and to extend the mine life to at least 2040, will now only be completed by the first half of 2028, instead of the previously anticipated date of the second half of 2026.

As a result, the forecast of costs to completion increased by 25% to $683-million.

The management update to the UGP schedule and budget, issued on Monday, follows a slower-than-planned ramp-up to expected sinking rates and to account for time incurred to date, as well as for anticipated future grouting programmes.

The grouting took longer than planned, owing to a combination of high-water volumes in the sandstone lithologies between 870 m and 752 m above sea level, combined with technical challenges associated with the transition to main sinking.

"Lucara has made tremendous progress on the Karowe underground expansion project, despite many challenges over the last year as we transitioned into the main sink phase of the underground development. Schedule delays due to longer-than-anticipated grouting activity have impacted the project timeline, however, the grouting methodology selected has proven to be effective in controlling water inflows. 

“As we transition out of the sandstones early in the fourth quarter of 2023, we look forward to meeting planned sinking rates,” says CEO Eira Thomas.

She also stresses that the project remains technically and economically feasible and that its major shareholder remains supportive of the asset.

In a Lucara statement, Adam Lundin comments that the Karowe expansion remains highly economic, despite the delays incurred. “As Lucara's largest shareholder, we remain fully supportive of the company."