Ohio Admin. Code 3701-29-15 - General soil absorption standards
(A)
Soil absorption
components shall be designed to minimize the risk of exposure to sewage
effluent, contamination of groundwater and surface water and provide for:
(1)
Treatment of
effluent through infiltration and movement through an adequate thickness of
unsaturated soil before the effluent reaches ground water or an aquifer, highly
permeable materials directly connected to groundwater, flow restrictive layers,
the land surface, or surface water; and
(2)
Dispersal of
treated effluent in the landscape to prevent surfacing or ponding of treated or
partially treated effluent.
(B)
A STS design
shall consider all site conditions identified in the soil evaluation and
designs shall ensure all requirements of this rule are met.
(C)
The minimum
vertical separation distance, unsaturated in situ soil, permissible effluent
quality and distribution method shall be selected from paragraphs (D), (E), (F)
and (G) of this rule as determined from the soil evaluation. Table 2 summarizes
these requirements.
Table 2. VSD and in situ soil requirements
|
Paragraph |
Limiting Condition |
Minimum VSD (inches) |
Minimum unsaturated in situ soil within infiltrative distance (inches) |
|
(D) |
Limiting condition not specified in this table |
18 |
8 |
|
(E)(1) |
Fractured and/or Karst bedrock |
36 |
12 |
|
(E)(2) |
Ground water or aquifer |
36 |
12 |
|
(E)(3) |
Other limiting conditions identified in soil evaluation or by the board of health as having high risk of not meeting 3701-29-15 (A) |
36 |
12 |
|
(F) |
Highly weathered soils with weak structure or low to very low permeability developed on the low lime till plains are present |
24 |
8 |
|
(G) |
Perched seasonal water if not established by board of health |
12 |
8 |
|
(G) |
Perched seasonal water as established by a board of health |
6 |
6 |
(D)
Except for paragraphs (E), (F) (G) and (H) of this
rule, the required minimum vertical separation distance shall be eighteen
inches, and the required minimum unsaturated in situ soil thickness within the
infiltrative distance shall be eight inches, to all limiting
conditions.
(E)
The required minimum vertical separation distance of
thirty-six inches and the required minimum in situ soil thickness of twelve
inches within the infiltrative distance shall be required when the following
site conditions are present:
(1)
Fractured and karst bedrock;
(2)
Groundwater or
an aquifer; or
(3)
Other limiting conditions identified in the soil
evaluation or otherwise identified by the board of health as having a high risk
of not meeting the requirements of paragraph (A) of this rule.
(F)
The
required minimum vertical separation distance of twenty-four inches, and the
required minimum in situ soil thickness of eight inches within the infiltrative
distance shall be required to seasonal water table when highly weathered soils
with weak structure or low to very low permeability developed on the low lime
till plains are present.
(G)
Except for paragraphs (E), (F) and (H) of this rule,
when a seasonal water table is present, the board of health may establish a
vertical separation distance no less than six inches and no greater than
eighteen inches, with a required minimum thickness of in situ soil within the
infiltrative distance of no less than six inches when effluent is discharged to
the soil absorption component. Unless otherwise established by the board of
health, the vertical separation distance to the seasonal water table shall be
twelve inches, and the required minimum thickness of in situ soil beneath the
infiltrative surface shall be eight inches when effluent is discharged to the
soil absorption component.
(H)
A board of
health may establish the required minimum vertical separation distance of
greater than zero inches and less than six inches, and the required minimum in
situ soil thickness within the vertical separation distance of greater than
zero inches and less than six inches where the seasonal water table is present
and the sewage effluent is pretreated to less than one thousand fecal coliform
CFU per one hundred milliliters. The infiltrative surface shall not be placed
below the depth of the seasonal water table.
(I)
Soils defined as
highly permeable materials within the infiltrative distance cannot be used to
meet the vertical separation and in situ soil requirements of this
rule.
(J)
When no limiting condition or flow restrictive layer
is present beneath the infiltrative surface, the soil absorption component
shall be placed at a depth to promote oxygen exchange and improved treatment of
effluent.
(K)
The vertical separation distance required in
paragraphs (D), (E), (F), (G) and (H) of this rule may be reduced using soil
depth credits allowed in paragraph (L) of this rule or met through the use of
an engineered drainage system to uniformly lower the level of the seasonal
water table, provided the soil absorption component is installed with the
required minimum in situ soil thickness and the soil depth is adequate to
accept and treat all effluent from the system.
(L)
Soil depth
credits for infiltrative surface elevation, pretreatment pathogen reduction,
low pressure distribution and/or timed micro-dosed distribution shall be used
as follows and in accordance with this chapter:
(1)
A one-to-one
equivalency soil depth credit shall apply to soil absorption components that
elevate the infiltrative surface above the ground surface to meet the required
VSD through the use of sand fill material as specified in
appendix
B to rule
3701-29-15 of the Administrative
Code, or other materials as approved by the director.
(2)
Soil depth
credits shall apply for pathogen reduction by pretreatment components as
authorized by the director for effluent meeting the fecal coliform treatment
standards and pretreatment component requirements of rule
3701-29-14 of the Administrative
Code.
(3)
A soil depth credit of twelve inches shall apply when
distribution to the soil absorption area provides for timed micro-dosing
controlled at each point of application not to exceed one quarter gallon per
dose using a uniformly spaced orifice density applying no more than one gallon
per four square feet of infiltrative area for each point of application per
day. A soil absorption component in compliance with the requirements of
appendix
C to rule
3701-29-15 of the Administrative
Code shall be eligible for this soil depth credit when the provisions of this
paragraph are met.
(4)
A soil depth credit of six inches shall apply when low
pressure distribution to the soil absorption area provides for time dosed,
uniform distribution of effluent to the infiltrative surface of leaching
trenches when the provisions of rule
3701-29-15.1 and
Appendix
A to rule
3701-29-15 of the Administrative
Code are met.
(M)
Low pressure or drip distribution of effluent shall be
used in accordance with this chapter, required design specifications, and as
follows:
(1)
Low pressure or drip distribution shall be required when applying effluent to
the sand fill infiltrative surface of a soil absorption component, or when
required by the product approval.
(2)
Low pressure or
drip distribution may be required by a board of health when the site and soil
conditions at the location of the proposed soil absorption component present a
significant risk for the surfacing of effluent, or where effluent may reach
ground water or an aquifer before adequate treatment is achieved . Conditions
where a board of health may require low pressure or drip distribution shall
include, but is not limited to the presence of highly permeable materials
directly connected to ground water or an aquifer, shallow limiting conditions,
and soils with slow to very slow permeability.
(N)
The soil
absorption component area shall be of adequate size and configuration to
disperse the effluent and prevent public health nuisance conditions. When
determining the size and configuration of the soil absorption component area
the following minimum requirements shall be met:
(1)
Soil
infiltration loading rates, including basal loading rates for sand fill
systems, shall be based on effluent quality and on soil structure, grade and
shape, texture, and consistence and shall be determined through reference to
soil evaluation information and the loading rate estimates in table 3 of this
rule.
(a)
The
selection of soil loading rates based on effluent quality shall be limited to a
rate for septic tank effluent or a rate for pretreated effluent meeting the
CBOD5 and TSS standard under rule
3701-29-14 of the Administrative
Code.
(b)
The structure, texture, structural grade and
consistence of the most limiting in situ soil layer within six inches of the
infiltrative surface, or basal surface if applicable, shall be used to
determine a soil loading rate, unless the soil layers below the upper six
inches are significantly less permeable.
(c)
The selected
soil loading rate for the site shall be used to determine the total square feet
of infiltrative surface or basal area required for the soil absorption
component. The daily design flow is divided by the selected soil loading rate
to calculate the minimum square feet of infiltrative surface area required for
soil absorption.
Table Soil Infiltration Loading Rates
|
Soil Characteristics |
Soil Infiltration Loading Rate (gpd/ft2) |
||||
|
Texture |
Structure |
CBOD5 |
|||
|
Shape |
Grade |
>25mg/L (septic tank effluent) |
<=25mg/L (Pretreated effluent) |
Row |
|
|
COS, S, LCDS, LS |
- |
0SG |
0.8 |
1.6 |
1 |
|
FS, VFS, LPS, LVFS |
- |
0SG |
0.4 |
1 |
2 |
|
CSL, SL |
- |
0M |
0.2 |
0.6 |
3 |
|
PL |
1 |
0.2 |
0.5 |
4 |
|
|
2.3 |
0 |
0 |
5 |
||
|
PR/BK/GR |
1 |
0.4 |
0.7 |
6 |
|
|
2.3 |
0.6 |
1 |
7 |
||
|
FSL, VFSL |
-- |
0M |
0.2 |
03 |
S |
|
PL |
- 1.2. 3 |
0 |
0 |
9 |
|
|
PR/BK/GR |
1 |
0.2 |
0.6 |
10 |
|
|
2.3 |
0.4 |
O.S |
11 |
||
|
L |
-- |
0M |
0.2 |
0.5 |
12 |
|
PL |
1,2,3 |
0 |
0 |
13 |
|
|
PR/BK/GR |
1 |
0.4 |
0.6 |
14 |
|
|
2.3 |
0.6 |
0.8 |
15 |
||
|
SIL |
-- |
0M |
0 |
0.2 |
16 |
|
PL |
1,2,3 |
0 |
0 |
17 |
|
|
PR/BK/GR |
1 |
0.4 |
0.6 |
IS |
|
|
2.3 |
0.6 |
O.S |
19 |
||
|
SCL,CL,SICL |
-- |
0M |
0 |
0 |
20 |
|
PL |
1,2, 3 |
0 |
0 |
21 |
|
|
PR/BK/GR |
1 |
0.2 |
0.3 |
22 |
|
|
2.3 |
0.4 |
0.6 |
23 |
||
|
SC. C, SIC |
-- |
0M |
0 |
0 |
24 |
|
PL |
1.2.3 |
0 |
0 |
25 |
|
|
PR/BK/GR |
1 |
0 |
0 |
26 |
|
|
2,3 |
0.2 |
0.3 |
27 |
||
(d)
When the total square feet of infiltrative surface or
basal area required for a replacement system or alteration of an existing
system cannot be met based on the daily design flow, the system design may
allow the storage of effluent combined with time dosing and low pressure
distribution to control and reduce the daily dose of effluent flow to the soil
absorption area to a daily dose flow that is less than the daily design flow.
The daily dose flow to the soil absorption area is then divided by the site
soil loading rate to calculate the total square feet of infiltrative surface
area required for the soil absorption component. For purposes of this rule,
daily dose flow means the maximum amount of effluent that can be applied to the
soil absorption component based on the site and soil conditions in accordance
with this chapter.
(2)
The HLLR shall
be used to determine the minimum required length of the soil absorption
component or basal area parallel to surface contours and shall be based on soil
characteristics, land slope, site conditions, infiltrative distance, and the
nature and depth to limiting conditions.
(a)
The HLLR shall
be determined based on the soil evaluation information with reference to table
4 to determine the rate based on the soil conditions, slope and infiltrative
distance.
(b)
The minimum length of the soil absorption component
shall be determined by dividing the daily design flow by the hydraulic linear
loading rate selected from table 4 of this rule.
Table 4: Hydraulic Linear Loading Rate Table
|
Soil Characteristics |
Hydraulic Linear Loading Rate (gpd/ft) |
|||||||||||
|
Slope 0-4% |
Slope 5-9% |
Slope >10% |
||||||||||
|
Texture |
Structure |
Infiltrative Distance (inches) |
Infiltrative Distance (inches) |
Infiltrative Distance (inches) |
||||||||
|
Shape |
Grade |
8-12 |
1224 |
2448 |
8-12 |
12-24 |
2448 |
8-12 |
12-24 |
24-48 |
Row |
|
|
COS, S, LCOS, LS |
-- |
0SG |
4.0 |
5.0 |
6.0 |
5.0 |
6.0 |
7.0 |
6.0 |
7.0 |
8.0 |
1 |
|
FS, VFS, LFS, LVFS |
-- |
0SG |
3.5 |
4.5 |
5.5 |
4.0 |
5.0 |
6.0 |
5.0 |
6.0 |
7.0 |
2 |
|
CSL, SL |
-- |
0M |
3.0 |
3.5 |
4.0 |
3.6 |
4.1 |
4.6 |
5.0 |
6.0 |
7.0 |
3 |
|
PL |
1 |
3.0 |
3.5 |
4 0 |
3.6 |
4.1 |
4.6 |
4.0 |
5.0 |
6.0 |
4 |
|
|
2, 3 |
5 |
|||||||||||
|
PR/BK/GR |
1 |
3.5 |
4.5 |
5.5 |
4.0 |
5.0 |
6.0 |
5.0 |
6.0 |
7.0 |
6 |
|
|
2,3 |
3.5 |
4.5 |
5.5 |
4.0 |
5.0 |
6.0 |
5.0 |
6.0 |
7.0 |
7 |
||
|
FSL, VFSL |
-- |
0M |
2.0 |
2.3 |
2.6 |
2.4 |
2.7 |
3.0 |
2.7 |
3.2 |
3.7 |
8 |
|
PL |
1, 2, 3 |
9 |
||||||||||
|
PR/BK/GR |
1 |
3.0 |
3.5 |
4.0 |
3.3 |
3.8 |
4.3 |
3.6 |
4.1 |
4.6 |
10 |
|
|
2, 3 |
3.3 |
3.8 |
4.3 |
3.6 |
4.1 |
4.6 |
3.9 |
4.4 |
4.9 |
11 |
||
|
L |
-- |
0M |
2.0 |
23 |
2.6 |
2.4 |
2.7 |
3.0 |
2.7 |
3.2 |
3.7 |
12 |
|
PL |
1, 2, 3 |
13 |
||||||||||
|
PR/BK/GR |
1 |
3.0 |
3.5 |
4.0 |
3.3 |
3.8 |
4.3 |
3.6 |
4.1 |
4.6 |
14 |
|
|
2, 3 |
3.3 |
3.8 |
4.3 |
3.6 |
4.1 |
4.6 |
3.9 |
4.4 |
4.9 |
15 |
||
|
SIL |
-- |
0M |
2.0 |
2.5 |
3.0 |
2.2 |
2.7 |
3.2 |
2.4 |
2.9 |
3.4 |
16 |
|
PL |
1, 2, 3 |
17 |
||||||||||
|
PR/BK/GR |
1 |
2.4 |
2.7 |
3.0 |
2.7 |
3.0 |
3.3 |
3.0 |
3.5 |
4.0 |
18 |
|
|
2, 3 |
2.7 |
3.0 |
3.3 |
3.0 |
3.5 |
4.0 |
3.3 |
3.8 |
4.3 |
19 |
||
|
SCL, CL, SICL |
-- |
0M |
20 |
|||||||||
|
PL |
1, 2, 3 |
21 |
||||||||||
|
PR/BK/GR |
1 |
2.0 |
25 |
3.0 |
2.2 |
2.7 |
3.2 |
2.4 |
2.9 |
3.4 |
22 |
|
|
2, 3 |
2.4 |
2.9 |
3.4 |
2.7 |
3.0 |
3.3 |
3.0 |
3.5 |
4.0 |
23 |
||
|
SC, C, SIC |
-- |
0M |
24 |
|||||||||
|
PL |
1, 2, 3 |
25 |
||||||||||
|
PR/BK/GR |
1 |
26 |
||||||||||
|
2, 3 |
2.0 |
2.5 |
3.0 |
2.2 |
2.7 |
3.2 |
2.4 |
2.9 |
3.4 |
27 |
||
(c)
The soil horizon selected to determine the hydraulic
linear loading rate shall also meet the following requirements and may be
adjusted as follows with approval from the board of health:
(i)
The most
restrictive soil horizon within the infiltrative distance shall be used to
determine the HLLR;
(ii)
Low permeability soil horizons located between the
infiltrative surface and the limiting condition may be excluded from the
calculation of HLLR if the cumulative thickness is less than twenty per cent of
the infiltrative distance upon concurrence of the designer and the board of
health.
(iii)
Any soil horizon below the depth of the required
minimum VSD may be considered to be a limiting condition when selecting the
HLLR.
(d)
Adjustments to the HLLR for designs shall be
considered by the designer and may be required by the board of health based on
the following site conditions:
(i)
Where the infiltrative distance is less than eight
inches, the HLLR may be decreased to reduce the risk of flooding of the trench
bottoms, seepage at the toe of mounds or saturating the soil around drip
tubing. Designs shall also consider decreasing the HLLR where the flow
restrictive layer, seasonal water table or infiltrative surface is less than
eight inches below the original ground surface to reduce the risk of inadequate
dispersal of sewage and surfacing of effluent; or
(ii)
When the
distance to the limiting condition falls near the boundary between the columns
for infiltrative distance on table 4 of this rule, designers and boards of
health may choose the appropriate HLLR or modify the HLLR.
(e)
HLLR
for STS designs with greater than twenty-four inches of in situ soil within the
infiltrative distance may be adjusted with concurrence of the designer and the
board of health as follows:
(i)
Up to two gallons per day per foot may be added to the
selected HLLR value in table 4 of this rule where fractured glacial till is the
uppermost limiting condition.
(ii)
Up to three
gallons per day per foot may be added to the selected HLLR value in table 4 of
this rule where fractured bedrock is the uppermost limiting condition or highly
permeable material is present above the limiting condition not to exceed ten
gallons per day per foot.
(iii)
Up to three
gallons per day per foot may be added to the selected HLLR value in table 4 of
this rule where no limiting condition is present within sixty inches of the
natural ground surface.
(f)
If site and soil
conditions indicate horizontal subsurface flow volumes will be greater than
normal, the minimum horizontal isolation distances shall be increased in
undisturbed areas around the perimeter or downslope of the soil absorption
component as necessary for adequate dispersal and prevention of surface
seepage.
(g)
A soil absorption component may be split into two or
more portions or zones to meet the required HLLR for each portion or
zone.
(h)
The calculated length along contour for soil
absorption components using the linear loading rates specified in table 4 of
this rule can be decreased up to ten per cent for new construction on existing
lots upon the effective date of the rules, and up to thirty per cent for
replacement sites to allow installation based solely on site limitations. Where
reductions in length along contour between twenty and thirty per cent are
allowed, low pressure or drip distribution of effluent into the soil absorption
component shall be required as specified in rule
3701-29-15.1 and appendix
A,
B
or C
to rule 3701-29-15 of the Administrative
Code as applicable. Perimeter drains may also be required to facilitate
subsurface drainage away from the site.
(i)
Alternative
methods to determine the HLLR and length along contour may include the use of
analytical solutions developed by Khan, et al. (1976), Hantush (1967), and
Finnemore and Hantzsche (1983) or numerical finite element or finite difference
computer models capable of simulating flow of water in saturated and
unsaturated systems. The use of alternative methods shall be detailed in the
system design with approval by the board of health.
(O)
General requirements for designing a STS soil absorption component are as
follows:
(1)
Effluent dispersal components shall be oriented parallel to natural surface
contours and shall not be sited on slopes exceeding limitations specified in
this chapter or applicable design manuals or product specification as
referenced in accordance with this paragraph;
(2)
The use of
perimeter drains, and/or an increase in the extent of fill beyond the edge of
elevated shallow trenches, mounds or drip distribution systems may be required
by a board of health when the flow restrictive layer is less than twelve inches
from the original ground surface, the depth to seasonal water table is less
than eight inches below the original ground surface, or when the infiltrative
surface is less than eight inches below the original ground
surface;
(3)
On sites where the installation of zones within the
same system or multiple systems directly upgradient from each other on the same
slope is unavoidable, there should be no less than fifty feet between soil
absorption components unless ground water mounding or flow models are used to
support lesser or greater separation distances. The designer and the board of
health shall ensure that proper spacing and dispersal of effluent occurs in the
landscape and does not create a public health nuisance;
(4)
Observation
ports shall be provided to monitor the infiltrative surface of the soil
absorption component as required in this chapter or approval by the director
and when determined to be necessary by the board of health;
(5)
Site
modification that requires the use of fill material either for soil absorption
or between soil absorption components shall follow manufacturer's
specifications as applicable and shall comply with the following:
(a)
When the trench
depth design results in the distribution product or media extending above
natural grade of the in situ soil, fill material placed between the trenches
after installation of the distribution media shall be of silt loam, loam, sand,
loamy sand or sandy loam texture. Fill material shall be applied in a manner
that protects and creates an interface with the underlying in situ soil and
prevents compaction of material between trenches;
(b)
Fill material
applied to the natural ground surface prior to the excavation of leaching
trenches for the purpose of creating trench sidewall shall be sand, loamy sand,
or sandy loam texture soil capable of maintaining trench sidewall stability
during installation and shall be applied in a manner that both protects and
creates an interface with the underlying in situ soil; and
(c)
Unless evaluated
as suitable, fill material shall not be present in the vertical separation
distance below the infiltrative surface of soil absorption components. Careful
consideration shall be given prior to siting soil absorption components in
settled non-compacted fill material including but not limited to strip mine
spoils to determine the development of pedogenic features and its suitability
for soil absorption. Over time, fill material may develop the characteristics
of soil; however, it shall be thoroughly evaluated for such characteristics, in
addition to treatment and dispersal capacities;
(6)
Designs shall
prevent damage to components or operational failures due to freezing
temperatures; and
(7)
The STS design for a soil absorption component may
include referenced design manuals, proprietary soil absorption component
specifications including those for gravelless and chamber products, or
alternative aggregate product specifications provided these do not conflict
with this chapter. Unless an available internet source for any referenced
manual or specification is included in a STS design, the design manual,
proprietary soil absorption component specifications, or alternative aggregate
product specifications shall accompany the plan. Inclusion of referenced
resources does not substitute for critical information or calculations required
for board of health approval of a STS design.
(P)
Installation
shall be conducted by a registered installer in a manner consistent with an
approved STS design to assure proper operation and future servicing or
monitoring of the soil absorption component.
(1)
Areas designated
for installation and replacement shall be undisturbed and be protected from
damage or disturbance. If any disturbance or damage has occurred, installation
shall not proceed and the registered installer shall contact the owner,
designer, and the board of health.
(2)
Soil moisture
conditions shall be evaluated at the time of installation throughout the soil
absorption area. The excavation or preparation of the soil infiltration
interface, such as a trench or basal area, shall not proceed when there is a
risk of smearing, compaction, or clogging of pore spaces as demonstrated by any
of the following:
(a)
A wire test in the field where the soil crumbles when
rolled between the palms of the hands before a wire one-eighth inch in diameter
can be formed;
(b)
When the moisture content is less than the plastic
limit as established in ASTM standard D4318; or
(c)
Other means
established by the board of health.
(3)
Proprietary soil
absorption components or alternative aggregate product specified in an approved
STS design shall be installed in accordance with the manufacturer's
installation instructions or product specifications and the approved STS design
provided these do not conflict with this chapter.
(4)
Baseline records
including but not limited to system startup reports, and any soil absorption
component O&M instructions shall be provided by the installer to both the
owner and the board of health as a condition of installation
approval.
(Q)
STS soil absorption components shall be operated,
maintained, and monitored as required by the operation permit issued by the
board of health to assure compliance with the requirements of this
chapter.
(R)
A board of health may not issue a variance to
paragraphs (E) and (H) of this rule.
Replaces: 3701-29-10, 3701-29-11
Notes
Promulgated Under: 119.03
Statutory Authority: 3718.02
Rule Amplifies: 3718.02
Prior Effective Dates: 7/1/1974, 7/1/77, 7/2/07, 7/30/07
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