Concrete Slab Here comes the concrete truck, which dwarfs the observatory project! We calculated about 5.5 yards of concrete needed for the pour, but ordered 6 to cover the variations in the trench dimensions. For instance, the trench width varied between 9" and 11". Better to have too much than too little. The mix was air-entrained concrete with fiber reinforcing, which means we didn't have to worry about steel rebar or wire mesh. The Concrete Truck Arrives Filling the Foundation Trench Filling the trench was pretty easy; the chute from the truck was able to reach all the corners with the driver's controls. The forms were filled and then struck off with a 2x6 as a screed. John's Working Hard Screeding the Concrete Slab The slab was smoothed with a magnesium bull float and a hand trowel. When it had firmed up a bit, the anchor bolts were installed at the predetermined locations. They were simply 1/2" galvanized bolts 8" long with large washers at the end. Smoothed with the Float and Installing Anchor Bolts Troweling Around the Anchor Bolts The 18" sonotube around the pier isn't set very far into the dirt and isn't anchored with stakes, so we used a few spacers to ensure that it didn't shift from the weight of the concrete. Some empty Coke cans filled the job perfectly! The pier was also covered in plastic wrap so that any stray concrete wouldn't stick to it. Pretty Much Finished Note the Coke Can Spacer An edger tool gives the concrete a professional look and also helps the forms separate from the slab later. At this point, there's only one more thing to do... An Edger Gives it a Professional Look John and Julie with the Masterpiece! ...add our initals! And the date, which just happened to be my 24th birthday: 28 July 2001. Finally, the slab was covered with a waterproof tarp to keep the moisture in and help the concrete cure. It will stay covered for several days. Couldn't Forget the Initials in the Cement! Covered with a Tarp to Keep Moisture In