We custom designed and built the fire pit

This looks really great! Is that a drop in fire pit pan? Is the door for a propane tank? If so, does it use just a typical propane tank from a gas grill? Any idea how long a tank would last?

Our company custom built the fireplace on site.

If you are looking for an off-the-shelf burner system that you can finish out like above, you can look here:
http://americanfyredesigns.com/fire-urns/burner-systems/
Or here:
http://www.firegearoutdoors.com/products/outdoor/outdoor-firepit-burners/

These are good, American-made products and include the correct controls. I recommend going through a hearth professional ( find one here: http://nficertified.org/pages_consumers/consumers-1.cfm ) to help you avoid some frustrating and perhaps dangerous mistakes.

By the way, the American Fyre Designs rectangular burner is 110,000 BTUs, so a 20# cylinder will last less than 4 hours

Beautiful work, Christopher Developments.