$11\mathrm{.}7$A sewer project entails the installation of $2,850$ lf of $8-$in$.$ sewer pipe. A backhoe equipped with a $1\mathrm{.}2$ cy capacity bucket will be used to excavate the trench $3$ ft wide to an average depth of $8$ ft through common earth that is expected to swell $25\%.$ This size machine works at $17$ sec per cycle and it is estimated that the trenching operation will operate at a $45$ min per working hour efficiency. A $12-$ft long trench shield will be used to shore the excavation so workers can enter the trench and it takes the crew an additional $2$ min every $12$ ft to move the trench shield along the trench as it's being excavated. Each section of pipe is $10$ ft long and workers can assemble each joint of pipe in $1\mathrm{.}8$ min. The pipe will be laid on $4$ in$.$ of pipe bedding material and this same material will fill the trench to $1$ ft above the top of the pipe. The rest of the trench can be backfilled using the same excavated material and any excess material can be disposed of on site at no additional cost. The crew can backfill and compact the trench with native material at a rate of $60$ cy$/$hr$.$ What is the estimated production rate of the pipe$-$laying operation in ft$/$hr$?$

$11\mathrm{.}8$For a horizontal directional drill project, how much drilling fluid is required for a $12-$in diameter, $900$ ft long borehole installed through a high plasticity clay?