Saturated Mound Development on Sloping Clay Layers Due to a Finite Source: An Analytical Solutiona

Abstract

Sloping clay layers beneath percolation ponds can cause infiltrating waste water to pond and move in directions not predicted by vertical infiltration equations. This paper presents a method for estimating the potential of percolation sumps located over sloping clay layers to interact with nearby ground-water resources. The analytical solution developed is for steady-state conditions and includes a procedure to estimate the time needed to reach steady state. The fundamental assumption used in the mathematical development requires that elevation-head gradients be much larger than pressure-head gradients. A method for testing the validity of this assumption is also included. An example calculation was performed for percolation sumps on the Naval Petroleum Reserves No. 1 in Elk Hills, California. That analysis shows that under the assumptions used, a sump exclusion zone on the Elk Hills is required to protect ground-water resources within the adjacent San Joaquin Valley.