Most soil interpretations and perc tests are conducted and evaluated using soil profiles from 5 foot hand augers (boring depth may vary upon site conditions). Some areas do require a larger profile viable through backhoe pits depending on site conditions. Typically, if the land is too rocky to dig a hole with hand augers we require a backhoe on site for our soil/landscape interpretations.
In some cases we use an instrument called a constant-head permeameter to measure the soil’s ability to transmit water through pores and between particles. This is called hydraulic conductivity (K). We measure the saturated hydraulic conductivity (Ksat) in soil by continuously supplying water into the permeameter. Flow rate measurements are recorded periodically throughout the test until it reaches equilibrium. Using Darcy’s Equation and the field measured numbers we can then determine K. Calculating the geometric mean of the individual Ksat calculations will determine the Ksat of the test area. Using soil descriptions and Ksat test values the permeability-limiting factors can be determined.
