I think it’s possible the current mayor is intentionally trying to bring up the number of detainees in Rikers when he can probably afford to use other means to track them. But it’s also possible that 3000 is not a sufficient capacity/number of beds. Seems like perhaps the thing to do would be to consider additional complementary jails or expansion of the current jails they plan on building to allow for more capacity. The latter might be less feasible given the timeline since that might be a major change to the scope of those construction projects.

Inevitably someone will ask why are they closing Rikers. You can read about it here: https://rikers.cityofnewyork.us/faq/