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Percolation test results
are not readily translated into field saturated hydraulic conductivity (K<sub>fs</sub>). However, an acceptable approximation can be made by accounting for the soil texture and by making measurements under non-saturated conditions<ref>Reynolds, W.D., Galloway, K., and Radcliffe, D.E. (2015). "The relationship between perc time and field-saturated hydraulic conductivity for cylindrical test holes.", National Onsite Wastewater Recycling Association (NOWRA) 2015 Onsite Wastewater Mega-Conference, Virginia Beach, VA, USA, November 3-6, 2015</ref>.
The required calculations have been written into an easy to use spreadsheet, formatted for printing:
* Shovel or other excavation apparatus
# Place 5 cm of clean fine gravel in the bottom of the hole. If the sidewalls are likely to collapse, use a paper basket to support the sidewalls.
#Place a piece of white plastic or similar provided with clear marks at 12.5 and 15 cm (5" and 6") from the bottom of the test hole prior to adding the gravel. For greater accuracy a float and pointer arrangement can be set up.
# If the soil contains considerable amounts of silt or clay, and certainly for any soil with “clay” as part of the texture description, the test holes should be pre-soaked before proceeding with the test. Pre-soaking is accomplished by keeping the hole filled with water for 4 hours or more. The water should be added carefully and slowly to avoid disturbing the soil (including the sidewall soils). The test should be carried out immediately after pre-soaking;
# Open the tube until the paper is in contact with the sidewalls of the test hole, then roll the top of the tube over to stiffen it.
# After placing the tube in the hole, place the plastic marker and add the base gravel layer.