Thank you, Ann, and good morning, everyone. I would like to thank the participants for taking the time to join us and to welcome Alberto Reyes, our new Chief Operating Officer, to the call. Following my opening remarks, Kim Perry, our Chief Financial Officer, will describe our financial results. I will then provide you with a picture of our plans for the balance of 2021 and a few closing remarks, and then we will be able to take your questions.
Before discussing the operating results, we want to note that our operations team continues to demonstrate their ability to be nimble and adaptive operators, all while focusing on excellent environmental, social and governance practices. Notwithstanding an excellent work culture, there were 2 lost time incidents at the Don David Gold Mine during second quarter. While these incidents did not result in serious injury, measures are ongoing to reinforce adherence to safety protocols and to strengthen the safety culture. Accordingly, a series of programs are underway to improve the overall culture of safety.
Turning to our infrastructure projects. We made significant construction progress on our filtration plant and dry stacks tailings project, which is targeted for completion in Q3. As we've noted, the dry stack tailings will accelerate reclamation of certain areas of the open pit mine, provide efficient storage of tailings, and, importantly, reduce water consumption, as approximately 80% of the processed water will be recycled and available for use.
During the quarter we completed 156 meters of underground development on the northern and southern exploration drifts. From these exploration drifts we completed over 3,400 meters of diamond drilling in 12 drill holes. Surface drilling on the Aguila project is ongoing, with 2069 meters of diamond drilling in 2 bowls. Exploration activities were focused on the Switchback vein system, which extends for over 1 kilometer of strike length and remains open both along strike and down dip, and as well as parallel structures to this system. Most notably, the Sandy vein system, which is located between the Switchback and Arista systems. Exploration drilling mainly targeted expansion and delineation of the principal Soledad vein to define additional resources, as well as step-out drilling on the parallel Sandy system of veins for resource expansion. Drilling is also targeting strike extensions of the Arista system beyond the current mine plan.
We have also renewed our focus on near-mine exploration with surface geological mapping and rock chip sampling in the Cerro Colorado area, notably in the vicinity of Aguila open pit and as well the surrounding area with additional drilling planned for these areas in the second half of 2021.
Turning to the second quarter operating results. I'm pleased to report that Gold Resource sold approximately 5,700 ounces of gold, 270,000 ounces of silver, 365 tonnes of copper, 1,200 tonnes of lead and 3,200 tons of zinc. During the second quarter, we processed ore at an average rate of 1,500 tonnes per day compared to 1,950 per day in 2020. While it was lower quarter-over-quarter, it was consistent with our mine plan for the year. The base plant continues to provide substantial efficiencies by the returning of processing waste to underground workings as backfill.
During the second quarter, we processed ore with average gold and silver grades as 10% and 11% higher respectively than the same period last year. Overall base metal grades were lower during the 3 months ended June 30, 2021. As a result of a change in the mine plan necessitated by challenging ground conditions encountered in the first quarter. We are happy that these challenges have been overcome, and our mine plan is back on track.
With that, I will turn the call over to Kim to discuss our financial results.