To obtain reproducible results with a soil percolation test, it is very important to:

To obtain reproducible results with a soil percolation test, soaking the hole with water before the test is crucial. This step ensures that the soil is at a consistent moisture level, which is essential for accurately assessing how well water drains through the soil. If the soil is dry or has varying moisture levels, the results may fluctuate significantly, leading to unreliable data regarding the percolation rate.

Saturating the soil helps eliminate variability caused by differing initial conditions, and it allows the tester to observe the soil's true drainage capacity once it is fully saturated. This process mimics conditions that would occur in a real-world scenario where the soil is expected to interact with water, ensuring that the test reflects typical performance.

While the other options may have their own merits, they do not directly contribute to the integrity of the percolation testing process in the same way that pre-soaking does. Adding gravel, for example, can alter how water interacts with soil but does not prevent variability in soil conditions across tests. Cross-referencing with soil maps may provide helpful insights about soil types but cannot ensure the consistency required for repeatable results. Lastly, repeating the test or using dual pits could help confirm findings but relies on the initial conditions being controlled, which is