Emilio describes the tedious work of building for the siege( [BBR] p.110):

… No rain fell from July 18 until August 13, which was favorable for the siege work, as the sand handled was dry and light. This dryness, however, rendered it easily displaced by the wind, requiring constant labor in re-covering magazines, bombproofs, and the slopes. The air too was full of the gritty particles, blinding the men and covering everything in camp.

By this date [8/13] twelve batteries were nearly ready for action, mounting in all twenty-eight heavy rifles, from thirty to three hundred pounders, besides twelve ten-inch mortars. … These works had been completed under fire from Sumter, Gregg, Wagner, and the James Island batteries, as well as the missiles of sharpshooters. Most of the work had been done at night. Day and night heavy guard details lay in the trenches to repel attack. The labor of transporting the heavy guns to the front was very great, as the sinking of the sling-carts deep into the sand made progress slow. Tons of powder, shot, and shell had been brought up, and stored in the service-magazines.