How a Septic Tank Site Evaluation is Performed?

By: Adrianna Noton

When a property for either a home or commercial building is evaluated for a septic tank installation, the inspector is checking to see if the site is suitable for onsite waste water disposal. An evaluation is very important because it helps protect homeowners from incurring costs in the future if there is a problem due to the location of the septic tank, and it protects the public and environment by ensuring the waste water will be disposed of and returned to the water table in a clean and healthy manner. Below is a general guide on how a septic tank site evaluation is performed:

1. A professional certified to evaluate septic sites will come to the property to do the septic site evaluation. The professional assesses the near by water sources and environmental considerations to make sure there is no health or safety hazard if the septic tank is installed. For instance, the inspector does not want waste water flowing into a creek or into a well.

2. Once the site area has been assessed, the inspector will assess the various levels of soil up to five feet into the ground. The homeowner will have hired an excavator to come out and dig a pit prior to the evaluation. The inspector will assess whether the soil conditions will support a septic tank. The soil assessment will look at such qualities as "soil texture" and "soil structure." The inspector will determine if the soil will allow for a large enough drain-field for the water that will be returned to the ground after being treated in the septic tank.

3. A soil percolation test, or PERC test, will be performed to determine the rate in which soil absorbs a specific volume of water. This is done to make sure the soil is appropriate for a soak-away, and to make sure that the soak-away is designed correctly. It will also indicate the size of the septic system to be used and how it will be designed. To perform a percolation test, a set of holes are dug 300mm square and 300mm below the proposed outlet from the septic tank or sewage treatment plant. The sides of the holes are mixed before the holes are pre-soaked. A controlled amount of water is poured in the hole and the test reading is based on how long it takes the soil to absorb the water added to the hole. A percolation test is considered to have failed if the results are fewer than 12 or over 100 seconds/mm drop. As well, a percolation test should not be carried out during bad weather, and if it is performed during the summer, then the number of times performing the test should be increased depending on the recent weather.

4. Once approved, that is, the results show proper adsorption, the septic marking points will be added to a survey to show where the septic tank will be located, As well, the area chosen will be free of trees and tree roots, underground cables, and away from buildings, property lines, or water sources such as creeks.

Septic tanks are required for any business or home. A Septic Tank Site Evaluation is mandatory to ensure the safety of the public and the environment. By understanding what the inspection involves, a homeowner can better prepare and budget for the expense.