Arguably not the same industry (but devastatingly adjacent): have a look at FedEx warehouses. Recently as low as $13.xx/hr, same sort of grueling work, plus the privilege of not knowing whether you'll need to show up at 4:00 AM or 7:00 AM. You don't get to know that until the night before, when you call a phone number around 8 or 9 to listen to a recorded message that will tell you. (Even then, you might show up only to find tape over the time clocks with a note that they're going to be starting later, after all, with the expectation that you'll just hang out off the clock in the meantime and then start at the new designated time.¹) And you have no idea how long you'll be working, either (except that it won't be 8 hours). 5–6 hours is possible. ~3 hours is probable. So you'll need to work 6 or 7 days just for the chance that you might get close to 30 hours. Ridiculously high turnover, as expected.
1. Yes, really. This is begging for a DoL inquiry; "Package Handlers are always paid for TIME WORKED [...] In the future please meet with your manager before just leaving. Thank you." — says a FedEx Ground facility's Area Manager, "Crystal", in an email.