A cross$-$section through a proposed municipal solid waste landfill is shown below. The design is clever $$ if the total head in the aquifer is greater than that at the base of the landfill $($as shown$),$ then there can be no outward flow of contaminants by advection since the groundwater is flowing into the landfill. In fact, the greater the head difference between the two, the greater the upward flow $$ which is even better from a contaminant transport point of view. But now think through what might be encountered when we go Calculate the maximum depth of excavation that can be permitted during construction for the conditions shown such that the restoring vertical forces are at least $1\mathrm{.}3$ times the disturbing vertical forces? Consider vertical equilibrium of a unit width of aquitard. Take ${}_{\text{s}\text{a}\text{t}}=21k\frac{N}{m^3}$ for the aquitard. $[$Answer $=13m]$to construct this cross$-$section