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What is a Site Evaluation? How to Get Started

Updated: Sep 18, 2019

What is a Site Evaluation?

A Site Evaluation, also known as a Site & Soil Evaluation, mainly entails the necessary fieldwork performed to assess a piece of land to determine its suitability for the installation of an onsite sewage disposal system, a.k.a. septic system, septic tank system, drainfield, etc. For a site to be evaluated, physical features of the property and details of the planned development are taken into account in order to establish a potential drainfield location. These include the property dimensions and location, planned buildings and their uses, drinking water sources, surface water bodies, available topographic landforms and their slope, and existing soil conditions, but also the improvements and practices on adjacent properties.

Do I need a Site Evaluation?

If you are located outside a town or city where there are no public sewer utilities nearby and plan to build a structure that will have a water source and indoor plumbing, then a site evaluation will be a necessity. If you are purchasing raw, undeveloped rural land, then you will need a site evaluation, also known as a “perc test”. If you are planning to subdivide a property into two or more parcels of land outside of a town or city, then you will need one or more site evaluations. There are also other situations that require a site evaluation, often unique to the property and situation, but in short, if a septic system design is needed, then a site evaluation is a necessary step along the way.

The Site Evaluation Process

Site Evaluation

Upon entering the property, some of the initial aspects your soil consultant will want to observe are the property corners and boundaries, and the potential building site. From there your soil consultant will look for the most suitable landscape position to support a drainfield installation. Places that are not acceptable include many low areas, such as swales, drainage channels, some floodplains, and also deeply filled or disturbed areas, but undulating, irregular topography may also be excluded during a site evaluation. The planned use and capacity of the building is also considered when selecting a suitable location, so your soil consultant will verify that there is enough potential absorption area (drainfield footprint) available to support the proposed development.

Sanitary Survey

Once a suitable area has been selected to study, the surrounding area must be observed to ensure that setback distances to potential pollution receptacles can be maintained. This is done to avoid potential contamination of drinking water supplies, surface water, and the ground surface. Typically, a radius of 200 feet from the study area limits will be visually surveyed in order to see that this requirement can be met during a site evaluation.

Soil Evaluation

After the initial site selection steps have been completed, the soil characteristics within the selected study area will be mapped with several soil profile holes that are either bored with a hand auger or dug using a backhoe. This allows the subsurface soil boundaries to be visually and texturally evaluated at their naturally occurring depths. Soils that are unsuitable for the installation of a conventional type of drainfield are excluded by shifting the study area location, as needed, or the process may repeat at a new location altogether. After evaluating the soil profiles, the soil consultant can begin to assign a percolation rate for the best soil at whatever depth it occurs throughout the potential drainfield site. The soil ‘perc’ rate is the final piece of the equation needed to complete a septic system design, resulting in a staked layout, based on the natural topographic contours of the site. The soil profile holes are logged, a site sketch is prepared, and all pertinent site data is recorded.


From the moment you request a site evaluation anywhere within the greater Charlottesville area of Central Virginia, Shenandoah Soil Consulting (SSC) begins the evaluation process by researching online sources. This includes a review of the County’s GIS mapping website to gather information available about topographic and environmental features of the property. For an area that is known to have poor percolation rates, shallow rock, or other soil issues, your soil consultant may review soil mapping of the area to obtain a basic understanding of the soil series that occur in the vicinity, which can help identify potential areas to study and areas to be excluded as likely to be unsuitable, saving time and money for the client. However, while soil maps are sometimes a useful resource, the information they contain can also range from fairly generalized to inaccurate for this purpose, and cannot be considered a substitute for a thorough site and soil evaluation.

Hiring a Soil Consultant

The process for evaluating a property and finding a suitable location to install an onsite sewage disposal system may appear to be complicated and daunting, or perhaps you have hired soil consultants in the past and this not your first rural development project. SSC is pleased to work with a wide range of clients, taking the unknowns out of rural property development and transforming them into achieved objectives. SSC staff includes a DPOR licensed Master Alternative Onsite Soil Evaluator (AOSE), providing excellent service and attentively assuring client satisfaction, while keeping public health a priority. SSC will be happy to discuss your plans and provide you with a free quote.

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