Percolation test crucial to parcel subdivision

Land owners should watch absorption rate of soil and look at management areas

By Lauren Bunting Contributing Writer

(Aug. 18, 2023) Land owners looking to subdivide existing parcels should understand the soil testing process, commonly referred to as a percolation, or “perc,” test, as well as management areas and their significance.

A percolation test is a test to determine a soil’s absorption rate, hence the term “perc” test.

All of the soils within our county are considered seasonal soils, meaning they have a fluctuating seasonal water table. Some fluctuate more than others.

Even soils that are considered well drained, or having seasonal high-water tables between 4 to 6 feet or more, can still have significant surface silt or clay in our area. The silt and clay affect the soils’ percolation rate. Soils are required to meet a percolation rate of less than 60 minutes per inch in the upper soils. The “wet-season” in Worcester County is whenever the majority of the county’s 16 monitoring wells are within 0.5 standard deviation of the wet season mean. Typically, this falls from November to May. It may not be “in-season” during that whole time and never has been, but it fluctuates.

The county’s monitoring wells are always read along with a particular site project as a comparison. The county wells have been monitored for 20 to 30 years, so data is well established. In soils with water tables closer to the surface, the management area of the county becomes important. Applications for soil evaluations in Worcester County are due every year by Dec. 31.