Wastewater, Earthmoving, Erosion Control
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Soil Percolation & Training
Percolation testing involves investigating the soils at a particular location and determining the site’s suitability for the disposal of wastewater or stormwater. A percolation test is always required for any new septic system (“individual wastewater disposal system” or “IWDS”), and is almost always required for earthmoving and erosion control (“One Start”) permit applications.
Why are percolation tests required?
Percolation tests provide critical information for the sizing of septic systems and stormwater “ponding basins” because those types of systems rely on the ability of soil to absorb water. If a percolation rate is just guessed at, or a contractor fails to notice restrictive soil conditions, the final result may be a system that fails 6 months after it is built, or a system that is built larger and more costly than necessary. Although the cost of a percolation test may seem like an unpleasant expenditure, it is far less than the cost of replacing a failed leaching field, or the construction of an over sized stormwater infiltration system.
How to obtain a percolation test
Starting in July 2007, DEQ began requiring that all percolation tests must be performed by qualified individuals. A qualified percolation tester is a person who has attended training provided by DEQ and passed an examination proving their knowledge of percolation testing procedures and basic soils information. If you are paying for a percolation test, make sure the tester has been authorized by DEQ first – they can show you a numbered certificate if you ask. For most single-family homes, only one percolation test pit is required. For other types of projects, three or more percolation test pits are required in order to obtain good results. Additionally, in certain types of soils a “deep observation pit” may need to be dug, in order for the percolation tester to obtain enough information to make their final design recommendations.