Bio-pond testing is a provisional method used by Metro Nashville to grade engineered soils for bio-ponds.
Ask your engineer or municipal inspector on how to sample as sampling depth and procedure can vary by job or contract.
This test provides the amount of soil that passes through a 2mm sieve and of the percent passing the 2mm sieve: organic content, sand, silt, and clay.
Soils with hard clay balls will have less passing the 2mm sieve as they act as rocks when dried, and do not break apart well.
Mulch may pass through the 2mm sieve as it will get ground, causing a bump in the reported organic matter content in the less than 2mm fraction.