Percolation “Perc” Test
Involves excavating a small hand-dug hole to a pre-determined depth. The hole is filled with water up to 6 inches from the bottom. The amount of time it takes for the water to drop a pre-determined interval (usually one inch) is measured and the test is repeated 7 times. A formula is then used to determine the percolation rate in minutes per inch.

Soils Investigation
This involves hiring a backhoe to dig some test holes up to 8 ft deep so the soils can be observed on the property to determine the septic capacity. If there is septic capacity, the soils investigation can also determine what kind of leach field(s) would be appropriate and approximately where they would be located. Often an engineer from the VT Agency of Natural Resources (VT ANR) and a representative from the town government is invited to observe the test holes.

Greywater
Typically the water which goes down the drain in a dwelling or business from sinks, showers, laundry or other uses other than a toilet.

Blackwater
Typically the waste which is flushed down the toilet in a dwelling or business.

Septic Tank
This is the first step in treatment of wastewater where an on-site disposal system is used. The wastewater flows to the septic tank where the solids settle to the bottom and the floating materials rises to the top. The tank is designed with baffles so that only the liquid in the middle leaves the septic tank. The solids and floating material must be pumped out by a septage hauler, typically every 2-3 years.

Pre-treatment Unit
A mechanical unit which filters and/or aerates the wastewater after it leaves the septic tank and before it goes to the leach field. Often, this kind of system can allow the leach field size to be reduced. A constructed wetland, when approved, can often be used as a pre-treatment unit to reduce the leach field size.

Leach Field
After the wastewater is treated in a septic tank and possibly a pre-treatment unit, it flows by gravity or is pumped to a leach field for disposal in the ground and treatment in soil before it reaches the groundwater. There are several types of leach fields which vary in size, height and expense. The two most common are described below.

In-Ground Septic System
A leach field which consists of perforated pipes buried in a disposal trench or disposal bed of gravel. A distribution box usually distributes the wastewater equally between the different perforated pipes.

Mound Septic System
A leach field where the disposal trench or bed is raised above the ground to maintain the proper distance from the water table or bedrock. This is used on wetter or more limited sites. The disposal trench or bed is installed into a mound of specified sand. The mound can be 3 to 5 feet at its highest.

Replacement Area
A second area where the soils are adequate for a leach field for the project. This area is noted on the design plans so that the area remains undisturbed. If the original leach field fails and cannot be repaired, the replacement area can then be used.

Septic Capacity
The ability to support one or more leach fields for on-site sewage disposal for one or more residences. See soils investigation above.

Constructed Wetland
A constructed wetland is an artificial wetland which is constructed to pre-treat the effluent from the septic tank before it goes to the leach field. In Vermont, these are constructed so that water never rises above the surface. The wetland plants are typically planted in a bed of compost. Below the compost is a layer of gravel. Perforated pipes disperse the effluent into the gravel so that the plant roots can feed on it. Some systems use a patented aeration system to enhance wastewater treatment. Often, in the summer, there is no effluent from the wetland. When there is, it is pumped to a leach field. An aerated wetland system has recently been approved by the state on a pilot basis. This kind of system can now be designed into a project without an additional permitting process.

Composting Toilet
This is a dry toilet. A ‘flush’ usually consists of adding a cup full of wood shavings, chopped straw or leaves. The waste usually drops to a bin in the basement of the house where it composts. There are several brands of manufactured composting toilets. Some have baffles which make sure that the newest waste and the oldest waste don’t mix. This assures that the end product is more thoroughly composted. Some toilets have small fans which run continuously to maintain proper air flow for decomposition. Some toilets have small electric heaters to keep the ‘compost’ warmer than the ambient temperature and to speed up decomposition.

Information provided on this website is not to be construed as professional advice. Please call us or email us about your unique project.