My husband and I did exactly what you are describing this past spring. here’s what we learned:
– renting a jackhammer at home depot is pretty easy. 4 hour rental was about $60. neither of us had operated one before and it turned out relatively easy and manageable. Gloves and goggles are necessary, but it’s totally doable. we took out a slab about the size of a parking space, 6″ deep, with an even deeper border – sounds bigger than yours – and it took 4-5 hours. i bet yours will go faster.
– commercial hauling costs a ton. I couldn’t believe some of the quotes we got! it is totally worth it to take it to fort totten yourself, assuming you are a DC resident (although no one asked for our proof of residency when we got there). The fort totten web page is helpful for specifics. We rented a truck at home depot, brought the truck back to the house, loaded it up, drove it to fort totten on a saturday morning, and dumped it all out. No charge, except for the home depot truck rental. (Get one of the pick up trucks, if possible. Fort totten doesn’t like enormous moving-style trucks coming in.)
– I bet you could get your project done in a saturday, if you start early enough. (Fort totten closes at 3pm on saturdays.) I highly recommend braving the jack hammer rental and hauling yourself to fort totten. it’s easy and inexpensive!