[Ord. No. 11-0248 §1, 8-9-2011]
The intent of this Article is to provide minimum standards for
site evaluations based upon evaluation of the soil characteristics,
namely texture, color, structure, drainage and depth. Criteria, also,
is given for sizing standard systems and some alternative systems.
[Ord. No. 11-0248 §1, 8-9-2011]
Nothing in this code or Article shall require the Code Official
to allow an installation based upon the criteria contained in this
Article. Whenever morphology tests and these criteria are used, the
size of the proposed system or suitability of a site shall be based
upon which criteria produce the most conservative system. This type
of evaluation shall be conducted by a licensed on-site soil evaluator
in determining soil morphological characteristics in the field.
[Ord. No. 11-0248 §1, 8-9-2011]
A.
An
investigation of a proposed soil absorption site shall consider the
following factors:
1.
Topography and landscape position;
2.
Soil characteristics (morphology) which includes texture, structure,
porosity, consistence, color and other physical, mineral and biological
properties of various horizons, and the thickness and arrangement
of the horizons in the soil profile;
3.
Soil drainage, which includes both external (surface) and internal
(soil);
4.
Soil depth;
5.
Restrictive horizons; and
6.
Available space.
[Ord. No. 11-0248 §1, 8-9-2011]
[Ord. No. 11-0248 §1, 8-9-2011]
A.
Uniform
slopes less than fifteen percent (15%) shall be considered suitable
with respect to topography. When slopes are less than two percent
(2%), provisions shall be made to insure adequate surface drainage.
When slopes are greater than four percent (4%), the absorption lines
shall follow the contour of the ground.
1.
Uniform slopes between fifteen percent (15%) and thirty percent (30%)
shall be considered provisionally suitable with respect to topography,
if the soils are thirty-six (36) inches or more thick. Slopes within
this range may require installation of interceptor drains upslope
from the soil absorption system to remove all excess water that might
be moving laterally through the soil during wet period.
2.
Slopes greater than thirty percent (30%) shall be considered unsuitable
except when a thorough study of the soil characteristics indicates
that a soil absorption system will function satisfactorily and sufficient
ground area is available to properly install such a system. Slopes
greater than thirty percent (30%) may be classified as provisionally
suitable when all of the following conditions are met:
a.
The slope can be terraced or otherwise graded or the absorption lines
located in naturally occurring soil to maintain a minimum ten (10)
foot horizontal distance from the absorption trench and the top edge
of the fill embankment;
b.
The soil characteristics can be classified as suitable or provisionally
suitable to a depth of at least one (1) foot below the bottom of the
absorption trench;
c.
Surface water runoff is diverted around the absorption field so that
there will be no scouring or erosion of the soil over the field;
d.
If necessary, ground water flow is intercepted and diverted to prevent
the water from running into or saturating the soil absorption system;
and
e.
There is sufficient ground area available to install the septic tank
system with these modifications.
3.
Complex slope patterns and slopes dissected by gullies and ravines
shall be considered unsuitable to topography.
4.
Areas subject to frequent flooding shall be considered unsuitable
to landscape positions.
5.
Depressions shall be considered unsuitable with respect to landscape
positions except when specifically approved by the Code Official.
6.
The surface area on or around a ground absorption system sewage treatment
and treatment system shall be landscaped to provide adequate drainage.
The interception of perched or lateral ground water movement shall
be provided where necessary to prevent soil saturation on or around
the ground absorption sewage treatment and treatment system.
[Ord. No. 11-0248 §1, 8-9-2011]
A.
Soil
borings or pits shall be taken at the site to be used for soil absorption
systems. These borings shall be taken to a depth of forty-eight (48)
inches or as required to determine the soil characteristics. Soil
borings or pits and core samples shall be evaluated and a determination
made on the suitability of the soil to treat and absorb septic tank
effluent. The important soil characteristics, which shall be reviewed
by the Code Official, are as follows:
1.
The relative amounts of the different sizes of mineral particles
in a soil are referred to as soil texture. All mineral soils are composed
of sand, two-hundredths (0.02) to five-hundredths (0.05) millimeters
in size; silt, which includes intermediate-sized particles that cannot
be seen with the naked eye but feel like flour when pressed between
the fingers, five-hundredths (0.05) to two-thousandths (0.002) millimeter
in size; or clay, which is extremely small in size and is the mineral
particle that gives cohesion to a soil, less than two-thousandths
(0.002) millimeters in size or a combination of these. The texture
of the different horizons of soils may be classified into five (5)
general groups and shall be used for determining the application rates
shown in Table 613.15(a).
a.
Soil Group I. Sandy texture soils contain more than
seventy percent (70%) sand-sized particles in the soil mass. These
soils do not have enough clay to be cohesive. Sandy soils have favorable
sewage application rates, but may have a low filtering capacity leading
to malfunction due to contamination of ground water. The sandy group
includes the sand and loamy sand soil textural classes and shall generally
be considered suitable in texture.
b.
Soil Group II. Coarse loamy texture soils contain
more than thirty percent (30%) sand-sized particles and fewer than
twenty percent (20%) clay-sized particles in the soil mass. They exhibit
slight or no stickiness. The coarse loamy group includes sandy loam
and loam soil textural classes and shall generally be considered suitable
in texture.
(1)
Sandy loam. Sandy loam feels gritty and forms
a ball that can be picked up with the fingers and handled with care
without breaking.
(2)
Loam. Loam may feel slightly gritty but does
not show a fingerprint and forms only short ribbons ranging from twenty-five
hundredths (0.25) to fifty-hundredths (0.50) inches in length. Loam
will form a ball that can be handled without breaking.
c.
Soil Group III. These fine loamy texture soils contain
fewer than forty percent (40%) clay-sized particles and not more than
thirty percent (30%) sand-sized particles in a soil mass. This group,
also, is limited to less than thirty-five percent (35%) clay when
the clay minerals exhibit high shrink/swell characteristic and exhibit
slight to moderate stickiness. The fine loamy group includes sandy
clay loam, silt loam, clay loam and silty clay loam textural classes
and shall generally be considered provisionally suitable in texture.
(1)
Silt loam. Silt loam feels floury when moist
and will show a fingerprint but will not ribbon and forms only a weak
ball.
(2)
Silt. Silt has a floury feel when moist and
sticky when wet but will not ribbon and forms a ball that will tolerate
some handling.
(3)
Sandy clay loam. Sandy clay loam feels gritty
but contains enough clay to form a firm ball and may ribbon to form
seventy-five hundredths (0.75) to one (1) inch pieces.
(4)
Silty clay loam. Silty clay loam is sticky
when moist and will ribbon from one (1) to two (2) inches. Rubbing
silty clay loam with the thumbnail produces a moderate sheen. Silty
clay loam produces a distinct fingerprint.
(5)
Clay loam. Clay loam is sticky when moist.
Clay loam forms a thin ribbon of one (1) to two (2) inches in length
and produces a slight sheen when rubbed with the thumbnail. Clay loam
produces a non-distinct fingerprint. There are two (2) major types
of clays — non-expandable and expandable. The non-expandable
clays, when wet, are slightly sticky to sticky; when moist, are friable
to firm; and when dry, they are slightly hard to hard. The non-expandable
clays (Group IVa) shall generally be considered provisionally suitable
in texture. The expandable clays, when wet, are very sticky and very
plastic and, when moist, these clays are very firm to extremely firm
and, when dry, are very hard to extremely hard. The expandable clays
(Group IVb) shall be considered unsuitable in texture.
d.
Soil Group IV. These clayey texture soils contain
forty percent (40%) or more clay-sized particles and include sandy
clay, silty clay and clay. This group may also include clay loam and
silty clay loam when the clay fraction is greater than thirty-five
percent (35%) and of a high shrink/swell nature.
(1)
Sandy clay. Sandy clay is plastic, gritty and
sticky when moist and forms a firm ball and produces a thin ribbon
to over two (2) inches in length.
(2)
Silty clay. Silty clay is both plastic and
sticky when moist and lacks any gritty feeling. Silty clay forms a
firm ball and readily ribbons to over two (2) inches in length.
(3)
Clay. Clay is both sticky and plastic when
moist, produces a thin ribbon over two (2) inches in length, produces
a high sheen when rubbed with the thumbnail and forms a strong ball
resistant to breaking.
e.
Soil Group V. This soil group may be of any texture,
however, the most predominant are cherty and very cherty clays, silt
loams and silty clay loams. The amount of rock fragments in these
soils is of a concern in areas of residual soils overlying highly
permeable bedrock where ground water could become contaminated. In
general, soils with less than fifty percent (50%) rock fragments will
be considered suitable. In general, soils with greater than fifty
percent (50%) rock fragments over highly permeable bedrock will be
considered unsuitable.
Soils with greater than fifty percent (50%) rock fragments will
be considered provisionally suitable if geological limitations are
not severe.
f.
The soil texture shall be estimated by field testing.
2.
Soil consistency. Soil consistency is comprised
of the attributes of soil material, typically clay, expressed by the
degree and kind of cohesion and adhesion or by the resistance to deformation
or rupture.
a.
Soil consistency when wet shall be considered as follows:
(1)
Stickiness. Stickiness is the quality of adhesion
to other objects. For field evaluation of stickiness, wet soil material
is pressed between the thumb and finger and its adherence noted. Degrees
of stickiness are described as follows:
(a)
Slightly sticky. After pressure, soil material
adheres to both thumb and finger but comes off one or the other cleanly.
It is not appreciably stretched when the digits are separated;
(b)
Sticky. After pressure, soil material adheres
to both thumb and finger and tends to stretch somewhat and pull apart
rather than pulling free from either digit; and
(c)
Very sticky. After pressure, soil material
adheres to both thumb and finger and is decidedly stretched when they
are separated; and
(2)
Plasticity. Plasticity is the ability to change
shape continuously under the influence of an applied stress and to
retain the impressed shape on removal of the stress. For field determination
of plasticity, the soil material shall be rolled between the thumb
and finger to observe whether or not a wire or thin rod of soil can
be formed. Degree of resistance to deformation at or slightly above
field capacity is as follows:
b.
Soil consistency when moist. Consistence when moist
is determined at a moisture content approximately midway between air
dry and field capacity. At this moisture content, most soil materials
exhibit a form of consistency characterized by a tendency to break
into smaller masses rather than into powder; some deformation prior
to rupture; absence of brittleness; and ability of the material after
disturbance to cohere again when pressed together. To evaluate this
consistency, a mass that appears slightly moist shall be selected
and attempt made to crush in the hand.
(1)
Friable. Soil material crushes easily under
gentle to moderate pressure between thumb and finger, and coheres
when pressed together.
(2)
Firm. Soil material crushes under moderate
pressure between thumb and finger but resistance is distinctly noticeable.
(3)
Very firm. Soil material crushes under strong
pressure; barely crushable between thumb and finger.
(4)
Extremely firm. Soil material crushes only
under very strong pressure; cannot be crushed between thumb and finger
and must be broken apart bit by bit.
c.
Soil consistency when dry. The consistency of soil
materials when dry is characterized by rigidity, brittleness, maximum
resistance to pressure, more or less tendency to crush to a powder
or to fragments with rather sharp edges, and inability of crushed
material to cohere again when pressed together. For evaluation, the
air-dry mass shall be selected and broken in the hand.
(1)
Slightly hard. Weakly resistant to pressure,
easily broken between thumb and finger.
(2)
Hard. Moderately resistant to pressure; can
be broken in the hands without difficulty but is barely breakable
between thumb and finger.
(3)
Very hard. Very resistant to pressure; can
be broken in the hands only with difficulty; not breakable between
thumb and finger.
(4)
Extremely hard. Extremely resistant to pressure;
cannot be broken in the hands.
3.
Soil structure. In many soils, the sand, silt and
clay particles tend to cling or stick to one another to form a ped
or a clump of soil. This is known as soil structure. Soil structure
may have a significant effect on the movement of effluent through
a soil. Structure is usually not important in Soil Groups I and II,
and these types of soils shall generally be considered suitable as
to structure. The three (3) kinds of soil structure that are most
significant in movement of sewage effluent through Groups III and
IV soils are block-like, platy and the absence of soil structure or
massive conditions. These kinds of soil structure are described as
follows:
a.
Block-like soil structure. In Groups III and IV
soils, if the soil exhibits many peds of angular and subangular peds,
then the soils have block-like structure. The sewage effluent may
move between the cracks of these types of peds. Block-like structure
in Groups III and IV soil frequently is destroyed by mechanical excavating
equipment manipulating the soil when it is too wet. Trenches for absorption
lines being placed in Groups III and IV soils with block-like structure
should only be dug when the soils are moist or dry. Block like soil
structure in Groups III and IV soils shall be considered provisionally
suitable;
b.
Platy soil structure. If Groups III and IV soils
fall out into plate-like sheets, then the soil would have platy structure.
Water or effluent movement through these soils would be extremely
slow, and the structure shall be considered unsuitable; and
c.
Absence of soil structure. Some Groups II, III and
IV soils are massive and exhibit no structural aggregates. In these
kinds of soils, water or effluent movement would be negligible. This
structure shall be considered unsuitable.
[Ord. No. 11-0248 §1, 8-9-2011]
A.
All
of the criteria in 19 CSR 20-3-060(7)(E — J) shall be determined
to be suitable, provisionally suitable or unsuitable as indicated.
If all criteria are classified the same, that classification shall
prevail. Where there is a variation in classification of the several
criteria, the following shall be used in making the overall site classification.
The lowest of the uncorrectable characteristics will determine the
overall site classification. The Code Official shall make this determination:
1.
If the topography is classified as unsuitable, it may be reclassified
provisionally suitable under the conditions outlined in 19 CSR 20-3-060(7)(E);
2.
If the soil texture is classified as unsuitable, the overall classification
will be unsuitable regardless of the other criteria unless the provisions
of 19 CSR 20-3-060(6)(K) are met;
3.
If the soil structure is classified as unsuitable, the overall classification
will be unsuitable regardless of the other criteria unless the provisions
of 19 CSR 20-3-060(6)(K) of this code are met;
4.
When soil thickness is classified as unsuitable, it may be reclassified
as provisionally suitable under the conditions outlined in 19 CSR
20-3-060(7)(H);
5.
When the restrictive horizon is classified unsuitable, it may be
reclassified as provisionally suitable under the conditions outlined
in 19 CSR 20-3-060(6)(K); and
6.
When drainage (ground water level) is unsuitable, it may be reclassified
as provisionally suitable under the conditions outlined in 19 CSR
20-3-060(7)(G).
[Ord. No. 11-0248 §1, 8-9-2011]
A.
Soils
with seasonally high water tables are of major concern in evaluating
sites for sewage effluent treatment. These are the soil areas that
give good sewage absorption rates during dry seasons of the year but
force sewage effluent to the surface during the wetter seasons.
1.
The depth of the seasonal high water table can commonly be recognized
by those examining soil profiles. The criteria for recognition of
high water tables is that of soil color. Subsurface horizons that
are in colors of reds, yellows and browns generally indicate good
soil aeration and drainage throughout the year. Subsurface horizons
that are in colors of gray, olive or bluish colors indicate poor aeration
and poor soil drainage. These dull or grayish colors may occur as
a solid mass of soil or may be in mottles of localized spots. The
volume of grayish color is indicative of the length of time that free
water stands in that soil profile. There are soils that have light-colored
mottles, which are relic from the light-colored rock from which the
soils have weathered. These soils would not have high water tables,
so one must distinguish between a true soil composed of sand, silts
and clays, or the rock material that may still exist in the soil profile.
Similarly, there are also some soils with surface or subsurface eluvial
horizons with light colors, which can be unrelated to drainage conditions.
2.
Any soil profile that has the grayish colors of chroma 2 or less
(Munsell color chart) indicative of high water tables, or is either
subject to periodic high water, within twenty-four (24) inches of
the surface, or is less than twelve (12) inches between the proposed
trench bottom and the high water table, shall be considered unsuitable
as to drainage. Soils where the seasonally high water table is less
than forty-eight (48) inches and more than twenty-four (24) inches
below the naturally occurring surface shall be considered provisionally
suitable for soil drainage, provided there remains at least twelve
(12) inches of soil between the proposed trench bottom and the seasonally
high water table. Soils where the seasonally high water table is greater
than forty-eight (48) inches below the naturally occurring surface
shall be considered suitable for soil drainage. Drainage systems installed
for ground water lowering shall be maintained so that a minimum separation
of one (1) foot occurs between the absorption trench bottom and the
seasonally high water table. For extensive drainage systems, such
as ground water lowering in subdivisions, easements shall be recorded
and shall have adequate width for reasonable egress and ingress for
maintenance.
[Ord. No. 11-0248 §1, 8-9-2011]
The thickness of soils to rock which are classified as suitable
or provisionally suitable in texture and structure, shall be at least
forty-eight (48) inches when conventional soil absorption systems
at conventional depths are to be utilized. Soil thickness greater
than forty-eight (48) inches shall be considered as suitable as to
soil thickness. Soil thickness less than forty-eight (48) inches and
greater than thirty-six (36) inches shall be considered provisionally
suitable. Where special design and installation modifications can
be made to provide at least two (2) feet of naturally occurring soil
below the bottom of the absorption trench, these soils may be reclassified
as provisionally suitable in thickness.
[Ord. No. 11-0248 §1, 8-9-2011]
A.
Restrictive
horizons in soil are recognized by their apparent resistance in excavation
or in the use of a soil auger. Restrictive horizons may occur as fragipans
or claypans. The fragipan is a layer that owes its hardness mainly
to extreme density or compactness as opposed to high clay content
or cementation. The layer is typically dense and brittle. Although
fragments are friable when removed, when in place the material is
so dense that water moves through it very slowly. Unlike fragipans,
the claypan is a compact, slowly permeable layer in the subsoil having
a much higher clay content than the overlying material. A sharply
defined boundary exists between the claypan and the overlying material.
Claypans are typically hard when dry and plastic and sticky when wet.
1.
Restrictive horizons that are greater than six (6) inches thick severely
restrict the movement of water and sewage effluent and do not adequately
respond to ground water lowering drainage systems. Where these horizons
are less than six (6) inches thick, they do not severely restrict
the movement of water and sewage effluent, but rather indicate the
presence of a seasonally high water table and may be modified after
special investigation.
2.
Soils in which restrictive horizons are six (6) inches or more in
thickness and at depths greater than forty-eight (48) inches below
the ground surface shall be considered suitable as to depth to restrictive
horizons. Restrictive horizons six (6) inches or more in thickness
and at depths between forty-eight (48) inches and twenty-four (24)
inches shall be considered provisionally suitable as to depth to restrictive
horizons. Restrictive horizons six (6) inches or more in thickness
encountered at depths less than twenty-four (24) inches below the
ground surface shall be considered unsuitable as to depth to restrictive
horizons.
[Ord. No. 11-0248 §1, 8-9-2011]
A.
The
site evaluation should include consideration of any other applicable
factors involving environmental principles including:
1.
The potential environmental hazard of possible failures of soil absorption
systems involving large quantities of sewage, which would dictate
larger separation distances than the minimums specified in this code;
and
2.
The potential environmental and health hazard of possible massive
failures of soil absorption systems proposed to serve large numbers
of residences, as in residential subdivisions or mobile home parks.
[Ord. No. 11-0248 §1, 8-9-2011]
A.
Sites
classified as suitable may be utilized for a ground absorption sewage
treatment and treatment system consistent with this code. A suitable
classification generally indicates soil and site conditions favorable
for the operation of a ground absorption sewage treatment and treatment
system or has slight limitations that are readily overcome by proper
design and installation.
1.
Sites classified as provisionally suitable may be utilized for a
ground absorption sewage treatment and treatment system consistent
with this code but with moderate limitations. Sites classified provisionally
suitable require some modifications and careful planning, design and
installation for a ground absorption sewage treatment and treatment
system to function satisfactorily.
2.
Sites originally classified as unsuitable may be used for soil absorption
treatment systems, provided engineering, hydrogeologic and soil studies
indicate to the Code Official that a suitable septic tank system or
a suitable alternate system can reasonably be expected to function
satisfactorily. These sites may be reclassified as provisionally suitable
upon submission to the Code Official and meeting the requirements
in 19 CSR 20-3-060(6)(K) of this code.
