During a perc test simulation, once the water level falls from 12” to 9”, what is the significance of this measurement?

The measurement of the water level falling from 12 inches to 9 inches during a perc test simulation is significant because it represents the threshold at which the calculation for the percolation rate begins. This drop indicates that water is moving through the soil, and the difference in depth over a specified time period can be used to determine how quickly water is infiltrating the soil.

Essentially, the rate at which the water level decreases from a certain depth is critical in understanding the soil’s ability to absorb and transmit water, which is vital for assessing soil suitability for septic systems or other drainage designs. The measurement taken after this initial drop provides the necessary data to calculate the percolation rate accurately, reflecting the drainage characteristics of the soil being tested.