Current through Register Vol. 47, No. 5, March 10, 2024
A. The
size and design of the soil treatment area must be based on the results of the
site and soil evaluation, design criteria, and construction standards for the
proposed site and OWTS selected.
B.
At proposed soil treatment area locations where any of the following conditions
are present, the system must be designed by a professional engineer and
approved by the local public health agency:
1. For soil types 3A, 4, 4A, 5, R-0, R-1 and
R-2, and Treatment Levels TL2, TL2N, TL3, and TL3N as specified in Tables 10-1
and 10-1Aof this regulation;
2. The
maximum seasonal level of the ground water surface is less than four feet below
the bottom of the proposed infiltrative surface;
3. A limiting layer exists less than four
feet below the bottom of the proposed infiltrative surface;
4. The ground slope is in excess of thirty
percent; or
5. Pressure
distribution is used.
C.
Calculation of Infiltrative Surface of Soil Treatment Area
1. The infiltrative surface of a trench or
bed receiving any treatment level of effluent is only the bottom area. No
sidewall credit is allowed except in deep gravel trenches and seepage pits that
are permissible in repairs.
2.
Long-term acceptance rates (LTARs) are shown in Tables 10-1 and
10-1A.
3. Factors for adjusting the
size of the soil treatment area are in Tables 10-2 and 10-3.
4. The required area for a soil treatment
area is determined by the following formula:
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a. Adjusted Soil
Treatment Area = Required Soil Treatment Area x Size Adjustment
Factor(s).
b. Size adjustment
factors for methods of application are in Table 10-2.
c. Size adjustment factors for types of
distribution media are in Table 10-3.
d. A required soil treatment area receiving
TL1 effluent may be multiplied by one size adjustment factor from Table 10-2,
Table 10-3, or both.
e. A soil
treatment area receiving TL2, TL2N, TL3, or TL3N effluent must be pressure
dosed.
(1) For products that combine
distribution and higher level treatment within the same component, pressure
distribution of the effluent over the soil treatment area must be
used.
(2) TL2 - TL3N effluent may
be applied by gravity flow in soil types 3, 3A, 4, 4A, or 5 for designs where
reductions in the soil treatment area size or vertical/horizontal separation
reductions are not being requested.
f. The distribution media in Table 10-3 may
be used for distribution of higher level treatment system effluent, but an
additional reduction factor from Table 10-3 must not be used. Sizing reductions
for higher level treatment systems are achieved through increased LTAR's
provided in Table 10-1
Table 10-1 Soil Treatment Area Long-term Acceptance
Rates by Soil Texture, Soil Structure, Percolation Rate and Treatment
Level
Soil Type, Texture, Structure and Percolation
Rate Range
|
Long-term Gallons Acceptance Rate (LTAR); per
day per square foot
|
Soil Type
|
USDA Soil Texture
|
USDA Soil Structure-Type
|
USDA Soil Structure-Grade
|
Percolation Rate (MPI)
|
Treatment Level
11
|
Treatment Level
21
|
Treatment Level
2N1
|
Treatment Level
31
|
Treatment Level
3N1*
|
R
|
>35% Rock (>2mm): See Table
10-1A
|
>35% Rock (>2mm): See Table
10-1A
|
1
|
Sand, Loamy Sand
|
Single Grain
|
0 (Structureless)
|
5-15
|
0.80
|
1.40
|
1.40
|
1.55
|
1.55
|
2
|
Sandy Loam, Loam, Silt Loam
|
PR (Prismatic)
BK (Blocky)
GR (Granular)
|
2 (Moderate)
3 (Strong)
|
16-25
|
0.60
|
1.0
|
1.0
|
1.1
|
1.1
|
2A
|
Sandy Loam, Loam, Silt Loam
|
PR, BK,
GR Massive
|
1 (Weak)
0
(Structureless)
|
26-40
|
0.50
|
0.80
|
0.80
|
0.90
|
0.90
|
3
|
Sandy Clay Loam, Clay Loam, Silty Clay Loam
|
PR, BK, GR
|
2, 3
|
41-60
|
0.35
|
0.55
|
0.55
|
0.65
|
0.65
|
3A
|
Sandy Clay Loam, Clay Loam, Silty Clay Loam
|
PR, BK,
GR Massive
|
1
0
(Structureless)
|
61-75
|
0.30
|
0.45
|
0.45
|
0.55
|
0.55
|
4
|
Sandy Clay, Clay, Silty Clay
|
PR, BK, GR
|
2, 3
|
76-90
|
0.20
|
0.30
|
0.30
|
0.30
|
0.30
|
4A
|
Sandy Clay, Clay, Silty Clay
|
PR, BK,
GR Massive
|
1
0
(Structureless)
|
91-120
|
0.15
|
0.20
|
0.20
|
0.20
|
0.20
|
5
|
Soil Types 2-4A
|
Platy
|
1, 2, 3
|
121+
|
0.10
|
0.15
|
0.15
|
0.15
|
0.15
|
NOTE: Shaded areas require system design by a professional
engineer.
1 Treatment levels are
defined in Table 6-3.
* Higher long-term acceptance rates for Treatment Level 3N
may be allowed for OWTS required to have a discharge permit, if the capability
of the design to achieve a higher long-term acceptance rate can be
substantiated
Table 10-1A Design Criteria for Soils with High Rock Content
(Type "R" Soils)
1,2,3,4
Soil Type, Percentage of Rock,
LTAR, Distribution |
Required Sand or Media Depth
Relative to the Quality of Effluent Applied to the Distribution
System |
Soil Type
|
Percentage and Size of
Rock5
|
Maximum LTAR (Gal./sq.ft./ day)
|
Type of Distribution Required
|
Treatment Level
16
|
Treatment Level 2
|
Treatment Level 2N
|
Treatment Level 3
|
Treatment Level 3N
|
R-0
|
Soil Type7 1 with more
than 35% Rock (>2mm)
|
Unlined Sand Filter: 1.0 for "Preferred Sand
Media"; 0.8 for "Secondary Sand Media"
|
Pressure
Distribution8
|
Minimum 3-foot deep Unlined Sand Filter
|
Minimum 3-foot deep Unlined Sand Filter
|
Minimum 2.5-foot deep Unlined Sand Filter
|
Minimum 2.5-foot deep Unlined Sand Filter
|
Minimum 2-foot deep Unlined Sand Filter
|
R-1; Option 1
|
Soil Type7 2 - 5, >35
- 65% Rock (>2mm); with >=50% of the Rock <20 mm (3/4 inch)
|
Use TL1 LTAR from Table 10-1 for the soil type
corresponding to the soil matrix, with a maximum LTAR of 0.8
|
Pressure
Distribution8
|
Minimum 2-foot deep Unlined Sand Filter
|
Minimum 1-foot deep Unlined Sand Filter
|
Minimum 1-foot deep Unlined Sand Filter
|
Sand media not required
|
Sand media not required
|
R-1; Option 2
|
Soil Type7 2 and 2A,
>35 - 65% Rock (>2mm); with >=50% of the Rock <20 mm (3/4
inch)
|
The allowable LTAR's are defined in each individual
treatment level column in this Table
|
Pressure
Distribution8
|
Remove, mix, replace 4 feet of existing material;
with a maximum LTAR of 0.6
|
Remove, mix, replace 2 feet of existing material;
with a maximum LTAR of 0.7
|
Remove, mix, replace 2 feet of existing material;
with a maximum LTAR of 0.7
|
Remove, mix, replace 2 feet of existing material;
with a maximum LTAR of 0.8
|
Remove, mix, replace 2 feet of existing material;
with a maximum LTAR of 0.8
|
R-2
|
Soil Type7 2 - 5, >65
Rock (>2mm), OR >=50% of Rock >20 mm (3/4 inch)
|
Use TL1 LTAR from Table 10-1 for the soil type
corresponding to the soil matrix, with a maximum LTAR of 0.8
|
Timed, Pressure
Distribution8
|
Minimum 3-foot deep Unlined Sand Filter
|
Minimum 3-foot deep Unlined Sand Filter
|
Minimum 2.5-foot deep Unlined Sand Filter
|
Minimum 2.5-foot deep Unlined Sand Filter
|
Minimum 2-foot deep Unlined Sand Filter
|
1.
General guidance for Table 10-1A: The intent of the soil type R-0 is to define
a material that consists of a high percentage of rock, or rock fragments, and
has a percolation rate of less than 5 mpi. Soil types R-1 and R-2 consist of a
high percentage of rock or rock fragments, but have a percolation rate of
greater than 5 mpi. Soil types R-0 and R-2 are considered to be a "limiting
layer".
2. No sizing adjustments
are allowed for systems placed in type "R" soils. The maximum LTAR's are
provided in this table
3. The
design of type "R" soil treatment systems must conform to sections 43.11.C.2
and 3.
4. All systems installed in
a type "R" soil must be designed by a professional engineer.
5. The percentage of rock may be determined
by a gradation conducted per ASTM standard D 6913-17 (2017 version),
6. Type "R" soil treatment systems that are
designed per the criteria noted in the Treatment Level 1 column of this table
do not require O/M oversight by the LPHA.
7. The "Percentage and Size of Rock" column
references the soil types noted in Table 10-1.
8. Design of the pressure distribution system
for type "R" soils shall comply with the requirements of sections 43.11.C.2.b,
c, e, f, g, h and i.
D. Allowable Soil Treatment Area Sizing
Adjustments:
1. The soil treatment area size
determined by dividing the design flow rate by the long-term acceptance rate
may be adjusted by factors for method of treatment, soil treatment area design,
and type of distribution media.
2.
For the purpose of the table, a "baseline system," i.e. adjustment factor of
1.00, is considered to be Treatment Level 1 (TL1) applied by gravity to a
gravel-filled trench.
3. Sizing
adjustments for use of the higher level treatment categories listed in Tables
10-1 will only apply provided the system is inspected and maintained as
specified in the requirements of section 43.14.D , Permitting and Oversight of
Maintenance for Soil Treatment Area Reductions and Vertical and Horizontal
Separation Distance Reductions Based on Use of Higher Level Treatment.
Table 10-2 Size Adjustment Factors for Methods of
Application in Soil Treatment Areas Accepting Treatment Levels 1, 2, 2N, 3 and
3N Effluent
Type of Soil Treatment Area
|
Method of Effluent Application
from Treatment Unit Preceding Soil Treatment Area
|
Gravity
|
Dosed (Siphon or Pump)
|
Pressure Dosed
|
Trench
|
1.0
|
0.9
|
0.8
|
Bed
|
1.2
|
1.1
|
1.0
|
Table 10-3 Size Adjustment Factors for Types of
Distribution Media in Soil Treatment Areas for Treatment Level 1
Systems
Type of Soil Treatment Area
|
Type of Distribution Media Used in
Soil Treatment Area1
|
Category 1
|
Category 2
|
Category 3
|
Rock or Tire Chips
|
Other Manufactured Media
|
Chambers or Enhanced Manufactured Media
|
Trench or Bed
|
1.0
|
0.9
|
0.7
|
1.
All proprietary distribution products must receive acceptance and the
applicable reduction through Division review per the applicable requirements of
section 43.13.
E. Design
of Distribution Systems
1. General
a. The infiltrative surface and distribution
laterals must be level.
b. The
infiltrative surface must be no deeper than four feet below grade unless TL2 or
higher effluent is applied to the distribution media and the system is
inspected and maintained as specified in the requirements of section 43.14.D .
The depth of the infiltrative surface will be measured on the up-slope side of
the trench or bed.
c. Trenches must
follow the ground surface contours so variations in infiltrative surface depth
are minimized. Beds must be oriented along contours to the degree
possible.
d. Pipe for gravity
distribution must be no less than three inches in diameter.
e. A final cover of soil suitable for
vegetation at least ten inches deep must be placed from the top of the
geotextile or similar pervious material in a rock and pipe system, chamber, or
manufactured media up to the final surface grade of the soil treatment
area.
f. Following construction,
the ground surface must be graded to divert stormwater runoff or other outside
water from the soil treatment area. The area must be protected against erosion.
Subsurface drains upslope of the soil treatment area may be installed to divert
subsurface flow around the area.
g.
Backfilling and compaction of soil treatment areas must be accomplished in a
manner that does not impair the intended function and performance of the
storage/distribution media and soil and distribution laterals, allows for the
establishment of vegetative cover, minimizes settlement and maintains proper
drainage.
h. Dosing may be used for
soil treatment area distribution. The dose must be sized to account for the
daily flow and the dosing frequency.
2. Distribution Laterals; Must meet the
requirements of section 43.9.D as applicable.
a. Distribution between laterals in a soil
treatment area must be as level as possible. Uneven settling of portions of the
distribution system following construction must be addressed by provisions in
the design to adjust flows between laterals.
b. The maximum length of distribution
laterals must not exceed 150 feet.
c. Distribution laterals longer than 100 feet
must be pressure dosed or the application of the effluent must be at the center
of the lateral through a distribution box.
d. A local public health agency may limit the
length of distribution laterals to a maximum of 100 feet.
e. For absorption beds, the separating
distance between parallel gravity distribution laterals must not exceed six
feet (center-to-center), and a distribution lateral must be located within
three feet of each sidewall and endwall.
f. The end of a distribution pipe must be
capped, unless it is in a bed or trenches in a level soil treatment area, where
the ends of the pipes may be looped.
g. To promote equal distribution to the soil
treatment area, the forcemain or effluent pipe must be connected to as near to
the middle of the distribution header as possible. However it must be offset
from any distribution lateral to prevent preferential flow.
h. Orifices must be oriented downward unless
pressure distribution is used and provision for pipe drainage is
included.
3. Pressure
Distribution
a. Design of pressure
distribution systems must include:
(1) Dose
size and frequency for either proposed flows and soil type, or media long-term
acceptance rate;
(2) Pipe diameter
and strength requirements;
(3)
Orifice size and spacing;
(4) A 30
- 72 inch operating head at the distal end orifice;
(5) Pump/siphon information; Total Dynamic
Head; gallons/minute;
(6)
Drain-back volume from forcemain; and
(7) Calculations, or a design software
reference, that indicates the selected component sizing will provide equal flow
within each active zone of the distribution system, and provide no more than a
10% flow differential from the initial orifice to the most distal end orifice
within each zone.
b. The
separating distance between parallel distribution pipes in a pressure
distribution absorption bed must not exceed four feet, and the outer
distribution pipe must be located within two feet of each sidewall and endwall.
Specific requirements for the design of sand filters are noted in section 43.11
.C.2.
c. Flushing assemblies must
be installed at the distal end of each lateral and be accessible from finished
grade. A sweeping 90 degree or bends limited to 45 degree must be
provided.
d. A local public health
agency may require that all effluent be screened prior to discharging to a
pressure distribution system. This may be accomplished by an effluent screen in
the septic tank or pump chamber, or a filter placed on the discharge pipe from
the pump or siphon.
F. Soil Treatment Area Requirements
1. Trenches
a. Trenches must be three feet wide or
less.
b. The separating distance
between trenches must be a minimum of four feet sidewall-to-sidewall.
c. Distribution laterals used in a trench
must be as close to the center of the trench as possible.
2. Beds
a.
Maximum width for a bed must be 12 feet, unless the bed receives effluent
meeting Treatment Level 2 quality or better.
b. The separating distance between beds must
be a minimum of six feet sidewall-to-sidewall.
3. Serial and Sequential Distribution:
a. A serial or sequential distribution system
may be used where the ground slope does not allow for suitable installation of
a single level soil treatment area unless a distribution box or dosing chamber
is used.
b. The horizontal distance
from the side of the absorption system to the surface of the ground on a slope
must be adequate to prevent lateral flow and surfacing.
c. Adjacent trenches or beds must be
connected with a stepdown/relief pipe or a drop box arrangement such that each
trench fills with effluent to the top of the gravel or chamber outlet before
flowing to succeeding treatment areas.
4. Alternating Systems
a. An alternating system must have two or
more zones that must be alternated on an annual or more frequent
basis.
b. For repairs, each section
must be a minimum of 50 percent of the total required soil treatment area. For
new installations, each separate soil treatment area must meet the minimum
sizing requirements of this regulation.
c. A diversion valve or other approved
diversion mechanism that requires the owner or operator to manually alternate
zones of the OWTS may be installed on the septic tank effluent line allowing
soil treatment area sections to be alternated.
d. The diversion mechanism must be readily
accessible from the finished grade.
5. Sequencing Zone Systems
a. Sequencing zone systems have two or more
soil treatment area sections that are dosed on a frequent rotating
basis.
b. Where soil conditions are
similar between the sections, each section area must be the same size. If soil
conditions are such that long-term acceptance rates are different, each section
may be sized for the same dose, but different long-term acceptance
rates.
c. An automatic distribution
valve must be used.
d. Dosing of
each system must be evaluated by the design engineer based on projected daily
flow rates, number of zones, and soil types.
6. Inspection Ports
a. A 4-inch inspection port accessible from
ground surface must be installed at the terminal end of each lateral in a
trench system and at each corner of a bed system. The bottom of the inspection
port tube must extend to the infiltrative surface and not be connected to the
end of a distribution pipe.
b.
Inspection ports in chambers may be installed according to manufacturer's
instructions if the infiltrative surface is visible and effluent levels can be
observed from the inspection port
c.
Additional inspection ports connected to distribution pipes may be
installed.
d. In addition, a local
public health agency may require an inspection port at the initial end of each
lateral in a trench system.
e. The
top of inspection ports may be terminated below the final grade if each is
housed in a component such as a valve box for a lawn irrigation system and has
a removable cover at the ground surface.
G. Storage/Distribution Media
1. Rock and Pipe
a. The perforated pipe must be surrounded by
clean, graded gravel, rock, or other material of equal efficiency which may
range in size from 1/2 inch to 2 1/2 inches. AASHTO M 43-05 (2005 version) size
No. 3 coarse aggregate meets this specification.
b. At least six inches of gravel, rock or
other material must be placed below the pipe. The gravel, rock or other
material must fill around the pipe and be at least two inches above the top of
the distribution pipe.
c. The top
of the placed gravel or such material used must be covered with non-woven
permeable geotextile meeting a maximum thickness rating of 2.0 ounces per
square yard or equivalent pervious material. An impervious covering must not be
used.
2. Chambers
a. Chambers must be installed with the base
of the unit on in-situ soil or, if placed on acceptable media, the
manufacturer's installation instructions must be followed so as to prevent
chambers from settling into the media.
b. Installation must be according to
manufacturer's instructions.
c.
Effluent may be distributed by gravity, pump or siphon.
d. For width and square footage requirements,
refer to section 43.13.E.1.d.
3. Media, Enhanced, or Other Manufactured
a. Manufactured media must be installed with
the base on the in-situ soil or placed on acceptable media meeting the
manufacturer's specifications for proprietary distribution products or combined
treatment/distribution products.
b.
Installation must be according to manufacturer's instructions.
c. Pressure distribution is required for
TL2-TL3N effluent, unless otherwise noted in this regulation.
4. Driplines
a. The infiltrative surface area must be
calculated using the long-term acceptance rate for the site or a more
conservative value if recommended by the manufacturer.
b. Driplines must be installed on
manufacturer's spacing recommendations.
c. Drainback must be provided for all drip
lines, pipes and pumps.
d.
Provisions must be made to minimize freezing in the distribution pipes,
driplines, relief valves, and control systems.
e. Provisions must be made for filtering,
back-flushing, or other cleaning.
5. Tire Chips
a. The pipe may be surrounded with clean,
uniformly-sized tire chips.
b. Tire
chips must be nominally two inches in size and may range from 1/2 inch to a
maximum of four inches in any one direction.
c. Wire strands must not protrude from the
tire chips more than 0.75 inches.
d. Tire chips must be free from balls of wire
and fine particles less than two mm across.
e. The top of the tire chips used must be
covered with non-woven permeable geotextile meeting a maximum thickness rating
of 2.0 ounces per square yard or equivalent pervious material. An impervious
covering must not be used.
H. Soil replacement systems
The construction of a soil replacement system is permitted to
bring the soil treatment area into compliance with the requirements of this
regulation
1. When a soil type "R" is
removed, the following requirements must be met:
a. All added soil must comply with the
following specifications:
(1) Added soil must
meet the specifications of either "preferred" or "secondary" sand filter media,
as specified in section 43.11.C.2.
(2) The long-term applicable rates as
specified in Table 10-1A must be used. No additional sizing adjustments are
allowed.
(3) The depth of the added
media must comply with the requirements of Table 10-1A.
(i) In order to utilize the reduced vertical
separation requirements for TL2 or higher quality effluent, the local public
health agency must have a program for inspection and oversight as specified in
section 43.14.D.4.
(4) A
gradation of the sand media used must be provided. The gradation must be dated
no more than one month prior to the installation date. However, a gradation of
the actual material placed in the excavation is recommended.
(5) All added soil must be completely settled
prior to installation of components as specified and approved by the design
engineer.
(6) Pressure distribution
must be used.
2. The removal and reinstallation of in-situ
soil may only be allowed where the soils are determined to be a soil type "R-1"
(Option 2). The design must comply with the requirements for this soil type
noted in Table 10-1A (Soil Type R-1, Option 2).
3. When a sand media is added to soil
treatment area or to an excavation where a soil type 1-5 (Table 10-1) is the
underlying soil, the following requirements must be met:
a. Added soil must meet the specifications of
either "preferred" or "secondary" sand filter media, as specified in section
43.11.C.2.d.
b. Unless the design
follows the criteria for a sand filter or mound system design as required in
section 43.11, the TL1 long-term acceptance rate for the receiving soil must be
used.
c. A gradation of the sand
media used must be provided. The gradation must be dated no more than one month
prior to the installation date. However, a gradation of the actual material
placed in the excavation is recommended.
d. All added soil must be completely settled
prior to installation of components.
I. Repairs
1. When space is not available or if there
are other site limitations that preclude other soil treatment area options for
OWTS repairs, wide beds, deep gravel trenches, deep beds and seepage pits may
be considered for repairs only. Other options are vaults or higher level
treatment systems, if the local board of health permits them.
2. Repairs to failing systems must conform to
setbacks identified in Table 7-1 when possible. When this is not possible using
all available methods described above, the jurisdiction with authority may
permit reductions to setbacks. At no point will a setback reduction be approved
by the jurisdiction less than what the existing separation is to existing OWTS.
In maximizing this setback distance, all methods available in section 43.10.I.1
must be utilized including but not limited to the use of Higher Level
Treatment, wide beds, seepage pits, etc., where allowed. Any setback reduction
beyond what the existing failing system presents must be approved by the local
board of health as outlined in section 43.4.O , if the local board of health
has opted to allow variances.
3.
Wide Beds: For repairs, beds may be wider than 12 feet without being required
to receive effluent meeting Treatment Level 2 quality or better.
4. Deep Beds: For repairs, the infiltrative
surface of a bed may be no deeper than five feet. Size adjustments as provided
for in Tables 10-2 and 10-3 must not be applied. System sizing will be based
strictly on the soil type and corresponding LTAR.
5. Deep Gravel Trenches
a. The length of an absorption trench may be
calculated by allowance for the sidewall area of additional depth of gravel in
excess of six inches below the bottom of the distribution pipe according to the
following formula:
Click to view
image
Where:
L = length of trench prior to adjustment for deep
gravel
W = width of trench in feet
D = additional depth in feet of gravel in excess of the
minimum required six inches of gravel below the distribution pipe
b. Maximum allowable additional
depth is five feet.
c. Percolation
tests or soil profile test pit excavations must be performed at the proposed
infiltrative surface depth.
d. Size
adjustments as provided for in Tables 10-2 and 10-3 must not be applied to deep
gravel trenches.
6.
Seepage Pits
a. For repairs, potential for
risk to public health and water quality may be evaluated by the local public
health agency. If risk is low in the determination of the local public health
agency, a seepage pit without higher level treatment may be used.
b. If the risks are not low, higher level
treatment of at least TL2 must be attained prior to discharge to these systems
for final dispersal.
c. A seepage
pit must consist of a buried structure of precast perforated concrete, or
cinder or concrete block laid dry with open joints.
(1) Pits must be provided with both vertical
sidewall and top supporting structural concrete or other material of equal
structural integrity.
(2) The
excavation must be larger than the structure by at least 12 inches on each side
and may not exceed 5 feet beyond the structure wall.
(3) The over-excavated volume must be filled
with clean, graded gravel or rock, which may range in size from ½ inch
to 2 ½ inches. AASHTO M 43-05 (2005 version) size No 3 coarse aggregate
meets this specification.
(4) The
capacity of the pit must be computed on the basis of long-term acceptance rates
determined for each stratum penetrated. The weighted average of the results
must be used to obtain a design figure.
(5) Soil strata in which the percolation is
slower than 30 minutes per inch must not be used for absorption or seepage.
These strata must not be included in the weighted average to determine the
long-term acceptance rate.
(6) The
infiltrative surface of the pit is the vertical wall area (based on dug
perimeter) of the pervious strata below the inlet plus the bottom of the
excavated area.
(7) The bottom of
the pit excavation must be greater than four feet above a limiting
layer.
d. Pits must be
separated by a distance equal to three times the greatest lateral dimension of
the largest pit. For pits over 20 feet in depth, the minimum space between pits
must be 20 feet.
e. The
requirements for the design and construction of seepage pits for the treatment
and dispersal of on-site wastewater on new sites is defined in section
43.12.C.
7. Wastewater
Ponds
a. Construction of new wastewater ponds
is prohibited.
b. For repairs of an
existing wastewater pond, the potential for risk to public health and water
quality may be evaluated by the local public health agency. If risk is low in
the determination of the local public health agency, the repair of a wastewater
pond may be permitted, however the following criteria must be followed:
(1) A septic tank must precede the wastewater
pond.
(2) The depth of the design
volume of the wastewater pond must be at least five feet.
(3) A wastewater pond must have two feet of
free board above the design volume of the pond.
(4) A wastewater pond must be fenced to keep
out livestock, pets, vermin, and unauthorized people.
(5) Wastewater ponds must be designed on the
basis of monthly water balance including design flow, precipitation,
evaporation, and seepage.
(6)
Wastewater ponds must be constructed so the seepage out of the bottom or sides
does not exceed 1/32 of an inch per day. If this limit cannot be achieved using
compacted natural soil materials including soil additives, an impermeable
synthetic membrane liner must be used.
(7) If the evapotranspiration does not exceed
the rate of inflow of effluent from the structure, a soil treatment area
meeting the requirements of this regulation must be installed to accept the
excess flow.
(8) Maintenance must
include preventing aquatic and wetland plants from growing in or on the edge of
the pond, protecting sides from erosion, and mowing grasses on the berm and
around the pond.
(9) Wastewater
ponds must be designed by a professional engineer.
8. Vaults
a. The allowable use of vaults for repairs in
a local jurisdiction is determined by the local board of health.
b. Criteria for vaults are in section 12.C.
of this regulation.
9.
Higher Level Treatment Options
a. Reduction
in required soil treatment area for repairs is possible with higher level
treatment only where the local public health agency meets the requirements of
section 43.14.
b. Design criteria
for higher level treatment systems are in section 43.11.
10. Remediation Systems
a. The intent of a remediation technology or
process is to sufficiently increase the infiltration rate through the
infiltrative surface at the bottom of an existing trench or bed and restore
permeability to the soil below. Treatment levels as defined in Table 6-3 are
not granted to remediation technologies.
b. A local public health agency may permit
the use of remediation technologies or processes to address an existing failure
or malfunction within a soil treatment area.
c. The use of a remediation technology or
process constitutes an alteration to the OWTS, and therefore the owner must
obtain a permit for this work from the local public health agency.
d. Upon approval of the local public health
agency, a system owner may choose to try a remediation technology or process to
see if an existing problem with the soil treatment area will be resolved. The
system owner bears the risk and cost of this attempt and is aware that an
additional repair may be required.
e. Remediation technologies and processes
must not adversely affect groundwater, surface water, any existing components,
the long-term effectiveness of the soil treatment area, or the
environment.
f. If the remediation
technology or process does not correct the problem with the system, a
conforming OWTS must be installed per the requirements in this regulation
within a time frame determined by the local public health agency.
g. The local public health agency may require
monitoring and/or maintenance of the remediation technology or process as a
stipulation of permit issuance.