Important/significant foundation soil physical properties

1
Important/significant foundation soil physical
properties
Color Texture Structure Consistence Coarse
fragments Reaction
2
Important/significant foundation soil physical
properties

• Soil reaction - The acidity or alkalinity status
  of a soil. Soils that are acid have an acid
  reaction those that are not acidic (basic) have
  an alkaline reaction.
• Coarse fragments coarse sand, pebbles, gravel,
  cobble, stones, rocks particles with a diameter
  gt ¼ dont hold water!

3
Soil reaction a qualitative or quantitative
assessment, based on visual observation of soil
reaction to weak (10) hydrochloric acid or a
commercially available test kit, or based on a
color comparison to known references.
4
Soil reaction what and why? What testing the
soil reaction will provide an indication of
whether the soil material is acidic, basic
(alkaline, containing carbonate salts), or
neutral. The scale a measure of the hydrogen
ion activity, i.e., the concentration of hydrogen
in the soil solution. Scale ranges from 0 (very
acidic) to 14 (very alkaline) Why - the acidity,
alkalinity, or basicity of the soil is a function
of 1) the geologic parent material, 2)
climate/weather particularly rainfall, 3) the
predominant vegetation, and 4) the drainage,
leaching, or historic wetting conditions of the
soil. Why the acidity or alkalinity will
influence the life of the septic system, the
functioning of the biofiltration process it also
reveals the circumstances of the soil property.
5
Soil reaction and the drain field Assessing
reaction Typically, the measure of soil
reaction is whether the soil reacts,
effervesces, when the soil comes in contact with
weak hydrochloric acid. Under such circumstances,
the effervescences is caused by a reaction
between hydrochloric acid and calcium carbonate,
i.e., limestone. This reaction no
effervescence pH lt 7.0 weak effervescence - pH
7.47.8, mildly alkaline moderate effervescence
- pH 7.98.4, moderately alkaline strong
effervescence - pH 8.59.0, strongly alkaline
violent effervescence - pH gt 9.0, very strongly
alkaline The presence of calcium carbonate,
i.e., limestone, indicates that the parent
material is sedimentary, that rainfall-induced
leaching has occurred to a depth approximated by
the depth of limestone accumulation, that
cementing agents are likely present in the soil.
6
In contrast, highly acidic soil indicates
granitic parent material, abundance of
alumino-silicates or acid-forming minerals
(iron), excessively leached soils, or
accumulations of excessive amounts of organic
matter associated with poor or inadequate
drainage and absence of oxidation of organic
material, i.e., peat bogs. None of these
conditions is conducive to properly functioning
drain fields either because of excessive
drainage, lack of drainage, or a hostile
environment for a functioning drain field.
7
About coarse fragments coarse fragments
facilitate good internal drainage this is one
purpose of the gravel envelope, whiere it is used
to facilitate drainage away from the drain
line. However, once water has drained away from
the line, the objective is to provide a storage
mechanism and retention time in the soil for
biodegradation of organics and destruction of
bacteria and viruses in the waste water.
Gravel doesnt hold water thats the point!
10 coarse fragments means 5 reduction in pore
space 20 coarse fragments means 10 reduction
in pore space
8
AB
A
C
9
Min 10 to seasonally high water table Max
7-10 coarse fragments below the depth of the
drain field
10
Questions?