Engineering the New Fire Pits

If you were at Outdoor University, hopefully you made it around to the outdoor cooking station for a campfire treat. But you probably didn’t stop and contemplate the mechanics of a campfire. Don’t worry: Our naturalist intern, Dom, took care of all that contemplation for you when he redesigned the fire pits this summer.

By Dominic Boyer

Dom and fellow naturalist intern Cody dig for one of the new fire pits.
Dom and fellow naturalist intern Cody dig for one of the new fire pits.
Now that the new fire pits at The Outdoor Campus are up and running, it’s time to provide a little insight into our design.

Our old fire pits followed the traditional approach, a rough circle dugout with the circumference lined with football sized rocks. The bottom of the pit was dirt and the ashy remains of many fires. While these pits served their purpose well, the thick layer of ash retained water and formed a layer of sludge days after the last rainfall. Consequently, the rocks began to slowly sink into the pit. As this layer of sludge was shoved out, the pits deepened. Less oxygen was able to fuel our fires, as the majority of the flames sat well below the existing ground level. The deepened pits made it harder to manage the coals, and the short diameter of the pit didn’t allow for very many kids to observe what was going on.

To address these concerns we planned for a larger diameter, a better drainage system to increase oxygen flow and a more prominent ring to clearly mark the safety boundaries of the pits.

Pea gravel lines the pit bottom, below the lava rock.
Pea gravel lines the pit bottom, below the lava rock.

Sandy had ordered two steel fire rings with a moveable grate. Since these rings were four feet in diameter, we began digging a seven foot circle in a spot farther from the existing trees to allow plenty of space for future tree growth without having to relocate the pits. Much of the sod we dug went into filling the old pit. That sod has since settled out, and the older pit location is barely noticeable.

One of the two completed fire pits.
One of the two completed fire pits.
The seven foot rings were dug a foot deep with a small sloped mound in the middle to drain water away from the center of the pit. Six inches of small pea gravel lined the pit. Another three inches of lava rock on top of that allowed for more air ventilation under the fire.

The steel rings were placed on top of those, and the lava rocks leveled out to be even with the ground level. This allowed for better air circulation as well as better drainage. The inside rock level is slightly higher than the outside to insure there will be no standing water in the pit, even if the entire seven foot circle is filled with water. The larger football sized rocks were then set against the steel ring to prevent the ring from moving and for visibility.

This fire pit's maiden voyage!
This fire pit’s maiden voyage!

So far, these rings have performed well, and hopefully they are up to many more seasons of smacos.


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