Guide To Soil And Septic For Land Buyers

If your land isn’t connected to a municipal sewer system, you’ll need a septic system to treat and dispose of household wastewater.  Here’s a breakdown of what you need to know:

1. How Septic Systems Work

A septic system treats wastewater on-site. It consists of a septic tank and a drain field. The septic tank separates solids from liquids, and the drain field filters the wastewater through the soil before it re-enters the environment. Proper soil drainage is critical for the system to function effectively. It typically consists of two main components:

A. Septic Tank: The Primary Treatment Unit

The septic tank is a watertight container, typically made of concrete or fiberglass, that receives all the wastewater from your home. It acts as the primary treatment unit, where solids settle to the bottom, forming a layer of sludge, and lighter materials, such as grease and oils, float to the top, creating a layer of scum. The middle layer contains partially clarified wastewater. 

B. Drainfield (Leach Field): The Soil’s Role in Filtration

The partially treated wastewater from the septic tank flows into the drainfield, also known as a leach field. The drainfield consists of a series of underground trenches lined with perforated pipes. The wastewater is slowly released from these pipes into the surrounding soil. As the wastewater percolates through the soil, it undergoes further treatment. Soil particles filter out remaining solids, while microorganisms in the soil break down organic matter and remove harmful pathogens. 

2. Soil Percolation Test

A percolation test, commonly known as a “perc” test, measures the soil’s ability to absorb water. This test is typically required for septic system permits and helps determine the size and design of your drainfield. A qualified professional will conduct the perc test by digging holes in the proposed drainfield area, filling them with water, and measuring the rate of water absorption. The perc test results are used to calculate the soil’s percolation rate, which is a key factor in determining the appropriate size and type of septic system.

3. Types of Septic Systems: Tailoring to Your Land

The type of septic system best suited for your property depends on a variety of factors, including soil characteristics, site conditions, local regulations, and your budget. Here are some common types of septic systems:

A. Conventional System – The conventional septic system is the most common type, consisting of a septic tank and a trench or bed drainfield. It relies on gravity to move wastewater from the septic tank to the drainfield. This system is typically suitable for properties with well-drained soils and a sufficiently deep water table. A conventional septic system is typically installed at a single-family home or small business. According to a study by the National Small Flows Clearinghouse (2018), conventional systems account for approximately 70% of all septic systems in the United States.

• • Standard System (Gravel Trenches) – These are the traditional and most widely used type of conventional system and are common for homes with plenty of space and good soil drainage. . They consist of a series of trenches filled with gravel, with perforated pipes laid within the trenches to distribute the wastewater. The text on the image mentions that you need at least 36 inches of suitable soil depth for this type of system, and it gives a ballpark cost estimate of $6,500 to $8,500.
    
    
  • Modified Conventional System (Chamber System) – Chamber systems are a more modern variation of the conventional system. Instead of gravel-filled trenches, they utilize prefabricated chambers that are connected to form a network for wastewater distribution. These chambers offer several advantages over gravel systems.. Chamber systems can be a good option for properties with limited space, as they often require less excavation than gravel systems. The cost of a chamber system typically ranges from $7,000 to $10,000, depending on similar factors as standard systems.

B. Panel Block System – This system offers a middle ground between the standard and chamber systems. It uses precast concrete panels to create the drainfield, which can be a good option if you have a smaller usable soil area but still have decent soil depth. It’s also a bit more robust than a standard gravel system. The cost for this type of system usually falls somewhere between $7,000 and $12,000.

C. Mound System – In areas with poor soil conditions, such as slowly permeable soils or a high water table, a mound system may be necessary. This system elevates the drainfield above the natural ground level using a mound of engineered soil. This raises the drainfield above any limiting layers. Mound systems are often used in areas with poorly drained soils, which account for approximately 10% of the land area in the United States (USDA NRCS, 2023). This can be a more expensive option, typically ranging from $10,000 to $20,000 or more.

D. Aerobic Treatment Unit (ATU) – This is the high-tech solution for wastewater treatment. An aerobic treatment unit (ATU) utilizes oxygen to enhance the breakdown of organic matter in the wastewater, making it a good choice for areas with sensitive environments or strict regulations. However, it comes with a higher price tag, often ranging from $15,000 to $30,000 or more.

4. Local Regulations

Familiarize yourself with the specific regulations and permitting requirements for septic systems in your area. Contact your local health department or building department to obtain this information. These regulations may dictate the types of systems allowed, minimum lot size requirements, setback distances from water bodies and property lines, and other crucial considerations. For example, some counties may require a minimum lot size of one acre for a conventional septic system, while others may have stricter regulations for properties located near sensitive water bodies (USEPA, 2002).