NOTE: Please read through the lab
handout ("Supplemental Laboratory - On-site Percolation Test") that was handed
out to you in class to familiarize yourself with the lab objectives, methods, and
procedures.
This tutorial will help you better
understand percolation testing methods, regulations, and data interpretation - and it will
help you answer the questions at the end of your lab.
One of the main causes of domestic drinking water contamination is septic system failure - some people pollute their own drinking water every time they flush. The purpose of a septic system and leach field is to filter and purify domestic waste-water so that the water is clean before it returns to the local groundwater system:
Source: U. of Georgia
The best way to avoid septic system failure is to properly design the system for existing soil conditions - which requires an on-site soil analysis. One way to better assess on-site conditions is to perform a percolation test:
Source: U. of Georgia
For a better explanation of how septic systems interact with the groundwater cycle, check this University of Georgia Cooperative Extension Website.
Some states do not require a percolation test, and rely on visual inspection methods only. The Landman (Private Environmental Consultant) Site gives an explanation of the Visual Inspection Method, and its applications in Michigan.
Other states feel that visual soil analysis and Soil Conservation Service soil survey data is not enough to determine on-site conditions, and percolation testing is mandated. This Kansas State University site shows how visual analysis may not be enough - download and peruse their "Soil Evaluation for Home Septic Systems" document (.PDF Format) if you are able. It contains the source for the Soil Conservation Chart and Graph we will be using in the lab.
You should be somewhat familiar with the different percolation test methods from reading the lab handout. We will be using the Fixed Distance Method, since it is the most popular method nationwide, and is the preferred method in New York State. For a demonstration of the applications of the method locally, check out this Cayuga County Conservation District - Wastewater Management Program site.
Many states, especially western states, use the Fixed Time Method primarily. The Solano County (California) Department of Environmental Management site gives a good general overview of percolation testing, and details the Fixed Time Method.
With the variety of methods and regulations nationwide comes confusion and controversy over which method is best - when in doubt, consult your state, county, and local health and building regulations. An interesting article from the University of Massachusetts explains why the percolation test should be used as a design tool, rather than as a "Build" - "Don't Build" site suitability determination: Life and Death of a Building Lot Subject to Perc.
These two links show how percolation testing data can be interpreted and applied:
Groundwater Pollution Primer - Virginia Tech. Civil Engineering Department
University of Nebraska - Lincoln,
Cooperative Extension Pamphlet G80-514-A
Sometimes, soils may percolate too fast, or too slow. This Land Surveying firm in New Hampshire gives a good explanation of the ramifications of extremely fast and extremely slow percolation rates: Rollins Land Survey . A link on their site will take you to the New Hampshire percolation testing regulations at the New Hampshire Department of Environmental Services site.
Some states have very rigidly defined regualtions and methods for perfoming percolation tests including:
Maryland
Colorado
(Gunnison County)
Tennessee
(Click the Percolation Test Procedures Link)
Nevada
Your Introductory Soils Textbook, The Nature and Property of Soils - Brady/Weil, has a section on percolation tests (Green Copies pp 253-4).
Both your book and the internet links above will help you answer
some of the questions at the end of this lab.
BACK to the Introductory Soils Syllabus
AUTHOR: Kurt Heiss
Forest Resources Management -
Hydrology & Watershed Management (MPS)
Grad. Office: B7 Marshall
Mailbox: 211 Marshall
E-mail: kheiss@syr.edu