$11\mathrm{.}9$A project requiring the trenchless installation of $1,100$lf of $16-$in$.$steel casing pipe will be performed using horizontal directional drilling. Based on the selected size and type of rig, the crossing can be completed by first drilling a $10-$in$.$pilot hole and then reaming a $22\text{'}\text{'}$borehole while pulling back the pipe. The soil will be a medium stiff, low plasticity clay and the drilling fluid will be mixed to a $50$sec$/$qt viscosity. The HDD rig is equipped with an $85$gpm mud pump. Estimate the drilling productivity in lf$/$hr for both the pilot bore and the final reamed hole.