$(10$ points$)$ Suppose a deep and fairly homogenous soil is going to be used to dispose of septic tank wastewater that contains $10m\frac{g}{L}$ of soluble $P$ in the form of phosphate. An adsorption isotherm is measured for the soil, from which the total sorption capacity of the soil is estimated to be $200mg\frac{P}{K}g$ soil. The $600$ liters of wastewater that is generated each day is evenly disposed of over a $70$ square meter area. Estimate the depth of phosphate movement in the soil after ten years, and make a decision whether a shallow well $(10$ meters$)$ deep at the edge of the disposal area could become contaminated with phosphate. Assume that the bulk density of the soil $(B_d)=1\mathrm{.}5k\frac{g}{m^3}.$ Density, as always, is defined as mass per unit volume. You can assume that a $6$ inch depth of soil, measured over a surface acre will weigh $2$ million pounds.

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