The process of vaccinating tens of thousands of people on Denton County’s waitlist is underway this week at Texas Motor Speedway in Fort Worth.

Denton County held the first of three vaccine clinics on Feb. 2, with more to follow later this week. In total, the county’s public health department plans to give roughly 30,000 doses at these events—three times the number administered the previous week.

“The ability to vaccinate 10,000 individuals in one day is a monumental task,” Matt Richardson, the county’s public health director, said in a statement. “We are thankful for the support from Texas Motor Speedway, various cities generously providing additional staffing, and staff from multiple Denton County departments working in unison to provide mass vaccination to our community.”

The county had been preparing for weeks to significantly scale up its vaccination efforts. The county administered just under 10,000 shots last week, and 6,000 the week before, according to previous county reports.

Richardson had also told county commissioners that his department was searching for suitable venues for larger drive-thru clinics like the ones held this week at Texas Motor Speedway.

The county continues to ask for volunteers—with both medical and non-medical backgrounds—to help administer vaccines through its Medical Reserve Corps program.

To receive a dose at one of these clinics, people who qualify are first required to register through Denton County’s online vaccine portal. This adds them to the county’s waitlist, which is currently open primarily to medical personnel, people who are at least 65 years old, or those age 16 and older who have a chronic medical condition.