Santa Clara County more than doubled its enrollment targets for the Affordable Care Act, a.k.a. Obamacare, driving up revenue for the Valley Health and Hospital System.

In the first five months of the fiscal year, Santa Clara Valley Medical Center’s on-call and overtime pay for doctors took a staggering leap, going from an average of less than $20,000 a month in 2011-12 to $967,000 this fiscal year. The Board of Supervisors will discuss the $1 billion health agency’s drastic uptick in costs—4,835-percent increase in per-month, on-call wages— as well as other issues at Tuesday’s meeting.