Soil Evaluation

It is necessary to have suitable soil if the drainfield is to function properly. Simply speaking, the most suitable soil would be well-drained sandy soil. However, there is great variation in types of soils within Livingston County. It is essential that a careful check be made of soil and drainage conditions before planning the installation and use of onsite sewage systems. The occurrence of saturated soil, or ground water, is an important factor since the sewage systems drainfield must be installed in well drained soil, at least 4 feet above the highest ground water elevation, in order to function properly. In selecting a building site, factors such as soil drainage, permeability, topography and ground water must be considered and are best determined by a soil evaluation.

No. A soil evaluation is a more extensive measure that involves the identification of varying soil horizon depths, soil texture, and seasonal water tables. A “perk” test, short for percolation test, uses water to determine the percolation rate in a soil. They are very time consuming and difficult to perform with consistency.​

The soil evaluation can be scheduled when you or your contractor/agent submit the application at the Environmental Health office. Appointments can usually be scheduled within 5 – 7 business days of receiving a complete application. However, during certain seasonal peak construction times, it may take up to 10 business days to schedule the soil evaluation. Remember, it is your responsibility to coordinate the appointment with the excavating contractor so they are aware of the appropriate date, time and location of the soil evaluation.

The evaluation is performed by digging test holes, each generally a minimum of 8 feet deep, in the area of the proposed sewage system. In some instances the holes may be dug 20 feet deep if suitable soils are not encountered at shallower depths. The Sanitarian will determine how many holes must be dug in order to be assured that the area is acceptable. Typically, this is a minimum 4,000 square foot area (i.e., 40′ X 100′.) The Sanitarian observes the excavation looking for these items:

• A consistent layer, at least 3 feet thick, of naturally occurring permeable soil (sand). The formation must be less than 20 feet below original ground surface and may not be acceptable if water is present.
• Evidence of a seasonal high water table.
• Example Plot Plan to area wells, surface water, structures, easements, and property lines.
• Topography, vegetation and drainage patterns.
• Other site characteristics may be considered at the Sanitarian’s discretion.

You should have an idea of where you would like to have the sewage system placed prior to the soil evaluation. However, the Sanitarian or excavating contractor may suggest a different area if the original area selected appears unsuitable. Keep in mind that the Sanitarian’s role on the site is to provide expertise and guidance to assist the homeowner or builder in making these decisions.

The Sanitarian, excavating contractor, and property owner or his/her designated representative must be on site during the evaluation. Important decisions will need to be made and it is a good idea for the property owner to be present. At a minimum, you are encouraged to select your desired home location and drainfield area.

The time it takes to complete a thorough evaluation depends on the depth, location, and availability of an approvable soil formation, as well as the equipment and expertise of the excavating contractor. Your application gives the Sanitarian approximately an 1.5 hours of field time to complete the evaluation. If a considerable amount of extra time is needed, a new application and fee may be required.

An approval area is an area defined during the soil evaluation for the location of an onsite sewage system. The approval area includes room for the current drainfield and future expansion or replacement. It is important that this area be preserved and it is highly recommended that this area be staked or flagged if you do not intend to build right away.

Typically, a soil evaluation is good indefinitely as long as no major changes are made to the property and the test pit locations can be identified. Changes made to the property line location, parcel size, grading changes, drainage changes, and soil mining can void the soil evaluation approval.

Results of the soil evaluation generally fall into 1 of 3 categories: Approval, Denial, and Further Evaluation Needed.

• Approval: The site is approved for construction of a sewage system. The Sanitarian will provide you with written notification indicating the property is approved in writing within a few days. Once your site is approved, you may apply for your permits.
• Denial: The site is not approved for an onsite sewage system. If your site is not approved, the Sanitarian will discuss with you what options exist for your site. You will also receive a written copy of a denial letter in the mail within a few days. The denial letter will list your options based on your site conditions. Please review the denial letter and keep it for further reference.
• Further Evaluation Needed: An approval area could not be located within the time constraints of the evaluation. Contact the Environmental Health office at (517) 546-9858 to make a follow-up appointment. Depending on the circumstances, an additional application and fee may be required.
• Parcel Splits: In instances where the property is to be split, surveying test pit locations will be required prior to receiving written approval. When five or more parcels are proposed, and each is less than 5 acres, additional requirements apply. In this case, it is advisable to contact your area Sanitarian prior to starting your project.