Environmental Programs
The Advantages of Holding Tanks
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Malfunctioning Systems & Troubleshooting
Homeowner's Manual for Onsite Wastewater Management Systems
Environmental Services
Onsite Wastewater Management Systems Program
Soil Evaluation
Soil
is the most important part of a septic system as it is an excellent
medium for treating wastewater. A detailed assessment of a proposed
site and its soil resources is essential for designing an onsite
wastewater treatment system that will treat wastewater for decades.
1.
Role of Soil in Effluent Renovation
Wastewater
delivered to soil from a septic tank contains a number of
contaminants (organic matter, soluble nutrients and a variety of
microorganisms) that need to be removed before the wastewater joins
with surface or groundwater. The role of soil is to remove
contaminants by natural physical, chemical and biological processes
that are active in healthy soil.
2.
Required Soil Conditions
Since
many of the natural processes required to treat wastewater depend on adequate aeration, unsaturated soil is essential for wastewater treatment.
Hence the soil must be
sufficiently permeable for water to move through and beyond the soil profile.
Adequate depth of soil ensures the wastewater is in contact with
soil material for a sufficient period of time for treatment to take
place. Information on the depth of soil and the ability of the soil to accept and transmit water
(permeability) provides the basis for assessing the suitability of
soil for wastewater treatment.
Together with
information on the amount of wastewater produced, soil depth and
permeability are used to design the form and size of the soil
adsorption system.
3.
Limiting Layers
The
depth and nature of the limiting layer is critical to the selection
and design of an onsite wastewater management system. Limiting
layers are zones in or below the soil where limitations occur. Many soils do not provide adequate depth above materials that
restrict water and air movement, or are seasonally saturated with
water. Some soil layers are too permeable for good contact between
soil and effluent. Limiting layers and conditions in
4.
Soil Depth
In
Manitoba a minimum of 1 metre (3.25 feet) of unsaturated soil
present beneath the wastewater distribution system is needed to
treat wastewater before contact with a limiting layer.
5.
Permeability
The ability of soil to transmit water has traditionally been described as its permeability. Permeability
is often estimated from other soil properties including texture,
structure, consistency and color.
Hydraulic
conductivity is a quantitative parameter (a number) that
indicates water transmission. Hydraulic conductivity varies with the
soil moisture content, but is frequently measured by first
saturating the soil.
6. Site Assessment
Soil
and site assessment involves the following series of steps:
-
Studying local soil information from the province’s soil maps
-
Conducting a visual assessment of the site to identify landscape features
-
Probing the soil to delineate soil resources on the lot
-
Excavating soil borings and pits to prepare profile descriptions of major soils on the lot
-
Matching the soil resource to appropriate treatment technology through a suitability assessment
Physical and chemical properties of the soil materials related to water and air movement and storage, root growth, and biological activity need to be investigated to gain an understanding of the quality of the available soil materials for wastewater treatment.
