Here's the current agreement between UPS and Teamsters: https://teamster.org/sites/teamster.org/files/6161478090_mas...

See articles 22, 40, and 41. $11 is current part-time package handler pay (preload), drivers are almost exclusively (with a few exceptions) full time employees, and max out at close to $30/hr. Locals can and do negotiate this higher, that's the national minimum. Also, a huge priority for the union is ensuring that UPS doesn't start using part time drivers instead of FT drivers.

Seasonals shouldn't make less, unless you're counting the $125 union initiation fee that everyone has to pay - a bit silly that it applies to them, probably a great money maker.