That's an excellent and practical question! From my experience with public space management, the depth—or more accurately, the internal height—of the bin is a critical factor, but it works in combination with other features. There isn't a single universal measurement, as needs vary between a busy city park and a suburban backyard.
The primary goal is to prevent contents from being easily accessed by wind, animals like raccoons or crows, or accidental tipping. For a standard 30-50 gallon wheeled bin, an internal height of at least 30 inches (about 76 cm) is a good baseline. This depth creates a "well" that makes it difficult for most animals to reach the bottom without fully entering the bin, which a secured lid should prevent.
However, depth alone isn't enough. The design of the lid is arguably more important. A tight-fitting, locking, or spring-loaded lid that only opens with a foot pedal or hand lever is essential. For areas with persistent wildlife, like bears, specialized bins with locking clasps are mandatory, regardless of depth.
Key considerations:
* Anchor it: A deep bin is useless if it can be knocked over. Bins should be anchored or placed in a secure holder.
* Don't overfill: The most common failure is an overfilled bin with a propped-open lid. The effective "depth" becomes zero.
* Material Matters: Heavy-duty, smooth plastic or metal resists chewing and clawing better than thin materials.
In summary, aim for a bin with a minimum internal depth of 30 inches, but always pair it with a robust, secure lid and proper anchoring. It's this integrated system—depth, lid, and stability—that effectively prevents litter from being pulled out.