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Subsurface sewage disposal systems (SSDS) consist of a house sewer, a septic
tank followed by a leaching system, any necessary pumps and siphons, and a
groundwater control system upon which the operation of the leaching system
depends. This interpretation focuses mainly on the septic tank leaching field
and groundwater control system
Soil Potential Ratings
Soil potential ratings indicate the relative quality of a soil for a
particular use compared to other soils in a given area, in this case
the State of Connecticut.
The rating criteria were developed by a committee of State and local
sanitarians, engineers, and installers. The soils data was provided by
the USDA Natural Resources Conservation Service (NRCS), and the performance
and site conditions for a typical system were defined. This information
provided a standard against which various combinations of properties of
soils within Connecticut could be compared.
The engineering and installation practices used to overcome various soil
limitations were listed, and their costs estimated. This information was
used to identify limitations and costs associated with installing an SSDS
on each soil in Connecticut. Soils with no or minor limitations for the
installation of an SSDS were rated the highest. Conversely, soils requiring
extensive site modification and design were rated the lowest. The ease of
system installation, and therefore cost, formed the basis of the rating scheme.
Rating Classes
The rating class definitions refer to installation of an SSDS that meets
State and local health code regulations. Soils with high potential have
characteristics that meet the performance standard. A typical system can
be installed at a cost of "x", which represents the going rate for installing
an SSDS. The actual value of x varies depending upon many factors unrelated
to soil properties.
The cost of installing a leaching field is expressed as a multiple of x and
called the cost factor. For example, a cost factor of 3x to and 3.5x means
that the estimated cost of installing a leaching field in the particular
soil ranges from 3 to 3.5 times more than that of installing a field in a
soil with high potential. The cost factors provide relative estimates of
the costs of installing an SSDS.
The soil potential ratings and associated cost factors, assuming a typical
system, are defined below.
High Potential - These soils have the best combination of characteristics
or have limitations that can be easily overcome using standard installation practices.
The cost factor is 1x to 2.0x.
Medium Potential - These soils have significant limitations, such as low
percolation rate, that generally can be overcome using commonly applied designs.
The cost factor ranges from 2.0x to 2.5x.
Low Potential - These soils have one or more limitations, such as low percolation
rate and depth to seasonal high water table, that require extensive design and
site preparation to overcome. The cost factor ranges from 2.5x to 3.5x.
Very Low Potential - These soils have major soil limitations, such as depth to
bedrock, that require extensive design and site preparation to overcome. A permit
for an SSDS may not be issued unless the naturally occurring soils meet the minimal
requirements outlined in the State health code. It is unlikely that these soils
can be improved sufficiently to meet State health code regulations. The cost factor
ranges from 4.25x to 6.0x.
Extremely Low Potential - These soils have multiple major limitations, such as
flooding and depth to seasonal high water table, which are extremely difficult
to overcome. A permit for an SSDS may not be issued unless the naturally occurring
soils meet the minimal requirements outlined in the State health code. It is
unlikely that these soils can be improved sufficiently to meet State health code
regulations.
Not Rated - Areas labeled Not Rated have soil characteristics that show extreme
variability from one location to another. The work needed to overcome adverse soil
properties cannot be estimated. These areas commonly are urban land complexes or
miscellaneous areas. An on-site investigation is required to determine soil
conditions at the site.
This data set is a digital soil survey and generally is the most
detailed level of soil geographic data developed by the National
Cooperative Soil Survey. The information was prepared by digitizing
maps, by compiling information onto a planimetric correct base
and digitizing, or by revising digitized maps using remotely
sensed and other information.
This data set consists of georeferenced digital map data and
computerized attribute data. The map data are in a soil survey area
extent format and include a detailed, field verified inventory
of soils and miscellaneous areas that normally occur in a repeatable
pattern on the landscape and that can be cartographically shown at
the scale mapped. The soil map units are linked to attributes in the
National Soil Information System relational database, which gives
the proportionate extent of the component soils and their properties.