Pumping Test near Basement

[EngMan40]

I performed a pumping test near a basement with an active drainage system. the pumping test was within the cone of depression of the basement which produced a cone within a cone. The initial cone of depression invalidates one of the assumptions in the Dupuit equation. Is there a modified equation that accounts for such initial conditions? Trying to be on th safe side, would the equation give me in this case - a higher or a lower K value than a pumping test with level groundwater?