Khoemacau Project
Silver stream deliveries from Khoemacau were approximately 115,210 ounces for the three months ended March 31, 2022. First concentrate was shipped in mid-July 2021 from Khoemacau and we received our first silver stream deliveries during the quarter ended September 30, 2021.
According to Khoemacau Copper Mining (Pty.) Limited (“KCM”), average monthly underground production increased consistently during the quarter ended March 31, 2022, from approximately 3,900 tons per day in January to approximately 6,300 tons per day in March. KCM reported that issues experienced in the quarter ended December 31, 2021, related to stope ore production and workforce availability associated with COVID-19 were largely resolved during the quarter ended March 31, 2022.
KCM expects that the mining rate will continue to increase steadily from current levels and reach full sustained production by the fourth quarter of 2022, absent further COVID-19 impacts. With the results experienced so far during the ramp-up period, KCM continues to expect that at full production Khoemacau will produce 171,000 to 182,000 tons of high-grade copper and silver concentrate a year, containing approximately 66,000 to 72,000 tons of payable copper and 1.8 to 2.0 million ounces of payable silver, over an approximate 20-year mine life from Zone 5.
During the quarter ended March 31, 2022, our interest in the payable silver from Khoemacau increased from 90% to 100% upon the draw by KCM of the remaining $26.5 million stream advance payments. After the final draw on March 14, 2022, we hold the right to receive 100% of the payable silver produced from Khoemacau until the delivery of 40.0 million silver ounces, and 50% thereafter. We will pay a cash price equal to 20% of the spot silver price for each ounce delivered; however, if KCM achieves mill expansion throughput levels above 14,300 tons per day (30% above current mill design capacity), we will pay a higher ongoing cash price for silver ounces delivered in excess of specific annual thresholds.
Mount Milligan
Gold stream deliveries from Mount Milligan were approximately 10,000 ounces for the three months ended March 31, 2022, compared to approximately 12,200 ounces for the three months ended March 31, 2021. Decreased gold deliveries resulted from differences in the timing of shipments and settlements during the periods.
Copper stream deliveries from Mount Milligan were approximately 2.7 million pounds during the three months ended March 31, 2022, compared to approximately 3.4 million pounds during the three months ended March 31, 2021. Decreased copper deliveries resulted from differences in the timing of shipments and settlements during the periods.
On January 18, 2022, Centerra Gold Inc. (“Centerra”) reported updated guidance for Mount Milligan. Centerra expects gold production at Mount Milligan during calendar 2022 of between 190,000 and 210,000 ounces of gold, compared to the previously issued guidance range of 170,000 to 190,000 ounces and actual calendar 2021 production of 196,400 ounces. Centerra also expects copper production in calendar 2022 to be in the range of 70 to 80 million pounds compared to the previous guidance range of 90 to 100 million pounds and actual calendar 2021 production of 73.3 million pounds. Centerra expects gold and copper production for calendar 2022 to be back-end weighted, with the first half of the calendar year representing approximately 40% of the metal production total while the second half of the calendar year representing up to approximately 60% of the metal production total. Centerra reported that the changes to expected gold and copper production at the Mount Milligan mine are due to planned mine sequence changes. Centerra also reported that a new National Instrument 43-101 (“NI 43-101”) technical report for Mount Milligan is expected to be issued in the second quarter of calendar 2022.
Centerra also reported that it obtained an amendment to the Mount Milligan mine environmental assessment certificate in January 2022, which will allow access to long-term surface water sources for the life of the project, subject to the receipt of ordinary course permits. In addition, according to Centerra, water inventory in the tailings storage facility as of March 31, 2022, combined with the incoming freshet in the second quarter of calendar 2022, is expected to secure continued operations for a period of 12 months or longer.
Further, Centerra reported mineral reserves and mineral resources for Mount Milligan for the year ended December 31, 2021. Centerra disclosed that compared to the year ended December 31, 2020, proven and probable mineral reserves decreased by 310,000 ounces of contained gold and 101 million pounds of contained copper, primarily due to mining