DAR File No. 38271
This rule was published in the February 15, 2014, issue (Vol. 2014, No. 4) of the Utah State Bulletin.
Environmental Quality, Water Quality
Large Underground Wastewater Disposal (LUWD) Systems
Notice of Proposed Rule
(Repeal and Reenact)
DAR File No.: 38271
Filed: 01/31/2014 12:06:01 PM
Purpose of the rule or reason for the change:
The purpose of this filing is to repeal the existing Rule R317-5 by replacing old language and awkward organization with newer concepts and technologies, referencing Rule R317-4 in similar subsections and parallel rules.
Summary of the rule or change:
Some highlights of the new rule include: 1) the new draft is not a "stand-alone" rule. It incorporates specific provisions in the new Rule R317-4 that are also pertinent to Large Underground Wastewater Disposal (LUWD) systems. These include: a) definitions; b) material standards; c) horizontal setbacks shown in Table 2 in Rule R317-4; d) soil exploration pits and percolation tests; e) design requirements; f) construction and installation; and g) final inspection; 2) outline and contents of new draft closely resemble Rule R317-4; 3) the addition of new authority and purpose sections to comply with format of other rules; 4) the scope section details where an engineer needs to consider factors in design such as flow, waste strength, site characteristics, etc.; 5) emphasis on sound engineering concepts needed for designing these large wastewater systems in more sensitive areas of the state with shallow groundwater or poorer soils being mindful of the increased design flows (over 5,000 pgd); 6) the entire rule has waiver capability granted by the director as long as the proposal does not override "the safeguarding of public health, protection of water quality, or engineering practice"; 7) twelve new definitions with LUWD systems language are included; 8) the new section titled General Standards, Prohibition, Requirements and Enforcement closely resembles Rule R317-4; 9) the new section Feasibility Determination and Concept Approval closely resembles the part of Rule R317-4 that are also pertinent to LUWD systems. In the old rule, no direction was given for applications for approval in concept. All new applications will have to obtain a feasibility determination prior to applying for a construction permit. This will include: a) number of soil logs and percolation tests required (it was unclear in the old rule); b) ground water determination (nothing previously specified; c) ground slope detailed up to 35%, using the same language as Rule R317-4; 10) Engineering Reports, Plans and Construction Permits includes more details about contents of reports and plans that are needed for DWQ review: a) must be designed by a Utah PE and certified Level 3 Onsite Professional per R317-11; details in applications closely resemble Rule R317-4; 11) the Design Requirements section references incorporation of Rule R317-4, with two minor exceptions, and details components required for a LUWD system (same as existing Rule R317-5). Horizontal separation distance between bottom of absorption trenches and anticipated highest ground water table is increased to 48 inches, unless pre-treatment unit is installed, then the separation can be 24 inches; 12) construction and installation is a new section that incorporates Rule R317-4 as a reference; 13) final Inspection and Authorization to Use inspection section references Rule R317-4 and the requirements are more clearly explained when compared to the old version; 14) operation and maintenance section has been overhauled. Closely resembles Rule R317-4 using the same frequency and inspection components; and 15) the section of the Operating Permits and Annual Inspection Reports has been removed which details what information is required to submit in order to obtain an operating permit on existing systems. This is no longer necessary as all LUWD systems have been identified and have operating permits. The rest of this section has the same language as the existing rule, explaining operating permits for new systems and annual inspection reports. Details on the inspection report with new fields to record septic tank measurements, pressure squirt height, date of last pumping, etc., which were all previously required on an operating permit.
State statutory or constitutional authorization for this rule:
- Title 19, Chapter 5
Anticipated cost or savings to:
the state budget:
No impact to state budget is anticipated. Design of large underground wastewater systems are made by the private sector representing the engineering community and their clients.
This rule offers the Local Health Departments (LHDs) some aspects of administration of these systems, but it is strictly voluntary. Those LHDs not wanting to participate, which represent a majority of the counties in Utah, will still have the Division of Water Quality being the lead in review and administration. For those few counties asking for this authority, local ordinances with application fees should cover any of their costs.
As additional lots are developed, businesses involved in the design and construction of large underground wastewater disposal systems may show an increased need for their services and products.
persons other than small businesses, businesses, or local governmental entities:
This rule should not add any additional costs from the present rule. There is language that allows an engineer to seek a waiver from any section of this rule, provided sound engineering and equivalent environmental and public health protection is met.
Compliance costs for affected persons:
No difference in compliance costs is anticipated for affected persons since the overall requirements are nearly identical to the original rule, but have been better organized for easier reference.
Comments by the department head on the fiscal impact the rule may have on businesses:
There is no difference in the fiscal impact expected on businesses since most of the proposed changes are in rule organization and clarity.
Amanda Smith, Executive Director
The full text of this rule may be inspected, during regular business hours, at the Division of Administrative Rules, or at:Environmental Quality
Water QualityRoom DEQ, Third Floor
195 N 1950 W
SALT LAKE CITY, UT 84116
Direct questions regarding this rule to:
- Judy Etherington at the above address, by phone at 801-536-4344, by FAX at 801-536-4301, or by Internet E-mail at email@example.com
Interested persons may present their views on this rule by submitting written comments to the address above no later than 5:00 p.m. on:
This rule may become effective on:
Walter Baker, Director
R317. Environmental Quality, Water Quality.
R317-5. Large Underground Wastewater Disposal Systems.
1.1 SCOPE: These rules shall apply to large underground
disposal systems for domestic wastewater discharges which exceed
5,000 gallons per day (gpd) and all other domestic wastewater
discharges not covered under the definition of an "Onsite
wastewater disposal system" in R317-1-1.13. Usually these
systems should not be designed for over 15,000 gpd. In general,
it is not acceptable to dispose of industrial wastewater in an
underground disposal system.
1.2 ENGINEERING REPORT: An engineering report shall be
submitted which shall contain design criteria along with all
other information necessary to clearly describe the proposed
project and demonstrate project feasibility.
1.3 SUBMISSION OF PLANS FOR REVIEW: Plans for new large
underground wastewater disposal systems or extensions of existing
systems shall be submitted to the Director for review as required
by R317-1. All designs shall be prepared and submitted under the
supervision of a registered professional engineer licensed to
practice in the State of Utah and certified pursuant to R317-11.
A construction permit must be issued by the Director prior to
construction of the wastewater disposal system or the building(s)
to be served by the wastewater system. The system designer must,
following construction of the system, certify in writing that the
system was installed in accordance with the approved plans and
A. Local Health Department Requirements - it is the
applicant's responsibility to ensure that the Large
Underground Wastewater Disposal System (LUWDS) application to the
Division is in compliance with local health department
requirements reqarding the location, design, construction and
maintenance of an LUWDS prior to the applicant submitting a
request for a construction permit to the Director. Local Health
Departments may petition the Director to require local review for
compliance with local requirements prior to DWQ initiating its
review. Where the petition has been approved by the Director, the
applicant is required to submit documentation that the local
health department has approved the proposed LUWDS prior to
issuance of a construction permit.
1.4 OPERATION AND MAINTENANCE: Operation and maintenance
shall be provided by the owner to ensure the disposal system is
functioning properly at all times. An operating permit will be
required for all large underground wastewater disposal systems to
monitor that proper operation and maintenance is occurring for
the protection of the environment and public health. The
operating permit shall be issued by the Director or, by delegated
authority, by the local health department having jurisdiction,
and shall be effective for a period not to exceed 5 years from
the issuance date.
A. Operating Permit Required: The owner of a large
underground wastewater disposal system shall provide a written
notice of intent (NOI) to the Division of Water Quality and the
local health department having jurisdiction of its intent to
operate a large underground wastewater disposal facility. Those
systems currently in operation must submit the NOI no later than
January 1, 2010. New systems permitted under this rule must
submit the NOI prior to final inspection. The notice of intent
shall be specific for the operating permit and shall include the
1. Facility name and address; owner name, address, and
2. List of Facility Components, e.g., septic tank, pump
tank, gravel drainfield trench, gravelless chambers, pressure
3. Design flow (gallons per day) and number and type of
4. Type of waste treated and disposed, i.e., residential,
restaurant, other commercial establishment, etc.
5. Sketch plan of existing system showing major facility
B. Local Health Department Authority to Issue Operating
1. A local health department that currently has approval
from the Director to administer an alternative systems program
may obtain authority within its jurisdiction to administer
operating permits for large underground wastewater disposal
systems by submitting a written request to administer this
program. The request must include an agreement to implement and
enforce inspection, servicing, monitoring, and reporting
requirements of this rule.
2. Local health departments that have been delegated
authority to administer the operating permit program must submit
an annual report on or before September 1 of the calendar year,
to the Division of Water Quality containing:
(a) A list of LUWD systems under delegation.
(b) A summary listing the compliance status of each
system, showing those systems that are currently failing, and
those systems that have been repaired.
(c) A summary of any enforcement actions taken,
identifying those actions that are still pending, and those that
C. Annual Report. The owner shall summit an annual
covering the period of July 1 to June 30 (the "reporting
year") to the permitting agency no later than August 1 of
each year. In this report, the owner shall report the following
1. All information required to be submitted in the
2. Checklist of inspections performed including the date
of the inspection and a list of findings.
3. Packed Bed media system sampling results.
4. Signature of owner or certified operator, and
D. Owner Responsibility to Maintain System: The owner is
responsible for maintaining its large underground wastewater
disposal system and for performing periodic inspections and
servicing of its system. Inspections of conventional systems
(gravity, or pump to gravity) shall be not less than once each
reporting year, and inspections of at-grade, pressure, mound and
packed bed media systems shall be not less than twice each
reporting year. At a minimum, the owner is responsible for
inspecting these components of the various type of
1. Community septic tank or treatment unit - measure
sludge and scum levels, and pump when necessary.
2. Effluent filter - clean when necessary.
3. Inspect distribution box.
4. Inspect pump, floats, alarm and control panel, and
record flow or hour meter reading.
5. Disposal field - inspect for ponding or surfacing in
disposal area. Flush, clean, re-adjust to equal pressure in
E. Operation and Maintenance Manual Required: New systems
must have a written operation and maintenance document describing
the treatment and disposal system and outlining routine
maintenance procedures, including checklists and maintenance logs
needed for proper operation of the system. This document must be
available at the time of the final inspection on all new
F. Packed Bed Media System Sampling and Monitoring
The owner of a packed bed media system is responsible for
sampling and monitoring for COD (Chemical Oxygen Demand), TSS
(Total Suspended Solids) and TIN (Total Inorganic Nitrogen) at an
interval not exceeding six calendar months. Additional sampling
and monitoring may be required if it has been determined that
there is a potential for groundwater impacts. Effluent quality of
a grab sample, before discharge to a disposal method, shall not
exceed 75 mg/L COD or 25 mg/L TSS.
1. Effluent COD exceeding 75 mg/L or TSS exceeding 25
mg/L shall be followed up with weekly sampling commencing within
30 days until such time as two successive results are obtained
that are within these limits. Any two successive samples
resulting in exceedence of either 75 mg/L COD or 25 mg/L TSS
shall result in the system being deemed non-compliant requiring
further evaluation and a corrective action plan.
2. For non-complying systems, the permitting agency shall
require the order:
(a) all necessary steps such as maintenance servicing,
repairs, and/or replacement of system components to correct the
(b) effluent quality testing for COD and TSS shall
continue every week until two successive samples of COD and TSS
are found to be in compliance;
(c) payment of fees for additional inspections, reviews
(d) evaluation of the system design including
non-approved changes to the system, the wastewater flow, and
biological and chemical loading to the system;
(e) investigation of household practices related to the
discharge of chemicals into the system, such as photo-finishing
chemicals, laboratory chemicals, excessive amount of cleaners or
detergents, etc.; and
(f) additional tests or samples to troubleshoot the
1.5 LARGE UNDERGROUND WASTEWATER DISPOSAL SYSTEM
The drainage system of any building or establishment
covered herein shall receive all wastewater as required by
R309-100, the Utah Plumbing Code and shall have a connection to a
public sewer except when such sewer is not available for use, in
which case connection shall be made as follows:
A. To an underground wastewater disposal system found to
be adequate and constructed in accordance with requirements
B. To any other type of disposal system acceptable under
1.6 MULTIPLE UNITS UNDER SEPARATE OWNERSHIP: Multiple
Units Under Separate Ownership shall not be served by a common
large underground disposal system except when, based upon sound
engineering judgment, other alternatives are determined
infeasible. In such cases, a common subsurface system may be used
provided the following requirements are met:
A. The common subsurface disposal system and conveyance
sewers shall be under the sponsorship of a body politic.
B. The subsurface absorption system shall be designed and
constructed to provide duplicate capacity (two independent
systems). Each system shall be designed to accommodate the total
anticipated maximum daily flow. The duplicate systems shall be
designed with appropriate valving, etc., to allow for periodic
alternation of the use of each system.
C. Sufficient land area with suitable characteristics
shall be available to provide for a third absorption system
capable of handling the total maximum daily wastewater flow. This
area shall be kept free of permanent structures, traffic or soil
modification (See Section R317-5-3.1(L)).
D. The subsurface absorption system should be used only
until a more permanent system becomes available.
1.7 NEW PROCESSES AND METHODS OF DISPOSAL: Where unusual
conditions exist, other methods of disposal not described herein
may be employed if approved by the Director and by the local
health authority having jurisdiction. The approval will be based
on evidence of adequacy to meet water quality standards and other
requirements of the Code.
1.8 UNITS REQUIRED IN A LARGE UNDERGROUND WASTEWATER
DISPOSAL SYSTEM: The large underground wastewater disposal system
shall typically consist of the following:
A. A building sewer with cleanout.
B. A septic tank.
C. An effluent filter.
D. A pressurized subsurface disposal system. This may be
an absorption field, deep wall trenches, absorption beds, or, for
packed bed media applications, drip irrigation dispersal,
depending on location, topography, soil conditions and maximum
ground water level.
E. Accessibility components to insure proper maintenance
and servicing. These may include risers on tanks to the surface
of the ground, with firmly secured lids; and absorption field
F. Pressurized systems typically require a dosing chamber
or dosing tank and cleanouts at the end of pressurized
G. Additional components may also be required depending
on the waste stream characteristics and the need to provide
adequate protection to groundwater. These components may include
pretreatment devices such as grease traps, or may involve
secondary treatment using packed bed media systems.
1.9 LOCATION AND INSTALLATION: Location and installation
of the wastewater disposal system shall be such that with
reasonable maintenance it will function properly and will not
create a nuisance, health hazard or endanger the quality of any
waters of the State. Due consideration shall be given to the size
and shape of the area in which the system is installed, slope of
natural and finished grade, soil characteristics, maximum ground
water elevation, proximity of existing or future water supplies
or water courses, possible flooding and expansion potential of
the disposal system.
1.10 ISOLATION: The system shall be isolated as shown in
MINIMUM HORIZONTAL SEPARATION IN FEET (Undisturbed Earth) Building Septic Absorption Seepage Absorption Sewer Tank Field Pit or Bed Trench trench Drinking Water Supply Source Deep Well (a)100 100 100 100 100 Shallow Well or Spring (b) (b) (b) (b) (b) Domestic Water Supply Lines (c) 10 10 10 10 Ponds, Lakes, Reservoirs and Water Courses --- 25 (d) (d) (d) Foundation Walls 3 5 25 25 25 Land Drain Located upslope --- 10 20 20 20 Located downslope --- 25 100 100 100 Property Line 5 5 5 15 10 Seepage Pits (Trenches) --- 5 10 12(e) 10 Absorption beds --- 5 10 10 10 Absorption fields --- 5 (f) 10 10 Footnotes: (a) Sewers may be constructed within the 100 foot protective zone, provided the sewer construction meets the requirements of R309-106-2.3.4. (b) It is recommended that the listed concentrated sources of pollution be located at least 1,500 feet from shallow wells and springs. Any proposal to locate closer than 1,500 feet will be reviewed on a case-by-casebasis, taking into account geology, topography, existing land use agreements, designated use of water system (public or non-public) and potential for pollution of water sources. It is the responsibility of the water supply owner to establish an adequate protection zone in accordance with the applicable drinking water rules. Even separation of 1500 feet or greater from concentrated sources of pollution will not guarantee suitability of the water supply system. (c) The requirements stated in R317-5-1.13(F) must be met. (d) A minimum of 100 feet is desirable, but may be modified to a lesser or greater distance, depending on soil conditions or mitigating measures such as lining the water course with impervious material. (e) Seepage pits or seepage trenches must be installed within an established absorption zone. The absorption zone will be sized based on the ratio of ground surface area "GSA" to the required sidewall area "SWA". The GSA/SWA ratio must be at least 2.5. The trenches and pits shall be installed within the absorption zone such that the spacing between trenches will be equal. Spacing of 12 feet (sidewall to sidewall) shall be a minimum. Distance to the edge or boundary of the established absorption zone shall be a minimum of 15 feet. The system must also conform to all other separation requirements identified in Table 5-1. The required sidewall area "SWA" shall be computed based on the design application rate with the associated soil type depicted in Table 5-8. The ground surface area identified within the absorption zone will be a minimum of 2.5 times the required sidewall area. An example of a typical seepage trench design with variation is available from the Division. (f) See Table 5-4.
1.11 CONSTRUCTION INSPECTION: Approval to operate the
constructed/installed facilities shall be issued following a
final inspection by a representative of the Department of Health.
The facilities must be inspected after installation but prior to
1.12 CONSTRUCTION MATERIALS: Materials used in
construction of the system shall be durable, sound, and not
unduly subject to corrosion. Pipe, pipe fittings and similar
materials shall comply with the requirements of
1.13 WASTEWATER DRAINAGE LINE OR BUILDING SEWER:
Wastewater drainage lines (or building sewers) shall comply with
R309-100, the Utah Plumbing Code, or meet the following
requirements, whichever is more restrictive.
A. Any generally accepted material will be given
consideration, but material selected shall be suitable for local
conditions to include soil characteristics, external loadings,
abrasions and similar problems.
B. The lines shall have a minimum inside diameter of 4
inches, in which case they shall be laid on a minimum slope of
1.25 percent. For sewer lines serving more than one dwelling
unit, it is recommended that the line be sized greater than 4
inches in diameter. Lines of greater sizes should be designed for
a minimum velocity of 2 feet per second based on the pipe flowing
full. See R317-3 for calculation of flow velocities.
C. The lines shall have cleanouts every 50 feet and at
all changes in direction or grade, except where manholes are
installed every 400 feet and at every change in direction or
D. On 4-inch and 6-inch lines, two 45 degree bends with
cleanout will be acceptable in lieu of a manhole, and 90 degree
ells are not recommended.
E. The design of wastewater pump stations shall comply
with the requirements contained in R317-3.
F. Lines shall be separated from water service pipes in
separate trenches and by at least 10 feet horizontally. If the
local conditions prevent a 10 foot separation, or when sewer
lines must cross water lines, the two lines may be placed within
the 10 feet of each other, provided:
1. The bottom of the water service pipe, at all points,
shall be at least 18 inches above the top of the wastewater
drainage line at its highest point.
2. The water service pipe shall be placed in a separate
trench or the line should be placed on a shelf of undisturbed
soil to one side of the sewer line trench.
3. The number of joints in the service pipe shall be kept
to a minimum and the materials and joints of both the sewer line
and water service line shall be of a strength and durability to
prevent leakage under known adverse conditions. The joints
between the two lines shall be staggered to the extent
4. When it is impossible to obtain the proper horizontal
and vertical separation as stipulated above, both the water and
sewer line shall be constructed in accordance with the
requirements of R309-112.2.
1.14 ESTIMATES OF WASTEWATER QUANTITY: The maximum daily
wastewater flow to be disposed of should be determined as
accurately as possible, preferably by actual measurement. Where
this is not possible, Table 5-2 may be used to estimate the
ESTIMATED QUANTITY OF DOMESTIC WASTEWATER
TYPE OF ESTABLISHMENT GALLONS PER DAY Construction/work camps (semi-permanent) 60 per person Resort camps with limited plumbing 60 per person Country Clubs 25 per person Dwellings a. Boarding house 60 per person Additional kitchen waste for non-resident boarder 10 per person b. Boarding schools 75-100 per person c. Condominium 400 per unit d. Mobile home 400 per unit e. Single family dwelling 400 per day f. Rooming House 40 per person Highway Rest Areas (improved with restroom facilities) 5 per vehicle Hospitals 250 per bed Nursing Homes 200 per Bed Institutions other than Hospitals and Nursing Homes 75-125 per person Motels and Hotels 62 per person Industrial Buildings (exclusive of industrial waste) 15-35 per person Launderette (self-service) 50 per load Office Buildings a. With cafeteria 25 per employee b. Without cafeteria 15 per employee Recreational Vehicle Parks/ Campgrounds a. Sanitary stations for self-contained Vehicles 50 per space b. Independent spaces (temporary or transient with sewer connections) 125 per space c. Dependent spaces (temporary or transient with no sewer connections) 125 per space with service building including showers 35 per person (Campground) (1) with service building but no showers 85 per space 25 per person (Campground) d. Campground with no flush toilets 5 per person Restaurants 35 per seat a. Additional for bars and cocktail lounges 2 per person Schools a. Boarding 75 per person b. Day, without cafeteria, gymnasiums or showers 15 per person c. Day, with cafeteria, but no gymnasium or shower 20 per person d. Day, with cafeteria, gymnasium and shower 25 per person Service Station (per vehicle served) 5 per vehicle Ski Areas and Visitor Centers 5 per visitor
R317-5-2. Septic Tanks. 2.1 GENERAL REQUIREMENTS: Septic tanks shall be
constructed of durable materials designed to withstand expected
physical loads and corrosive forces. They shall be watertight and
designed to provide settling of solids, accumulation of sludge
and scum, and access for cleaning, as specified in the following
2.2 TANK CAPACITY: Septic tanks shall be sized on the
(1) V = 1.5Q for Q less than or equal to 1500
(2) V = 1125 + 0.75 Q for Q greater than 1500
V = liquid volume of tank in gallons
Q = (Maximum anticipated) wastewater discharge in gallons
2.3 TANK DIMENSIONS: In general, tank length should be at
least 2 or 3 times the width. Liquid depth of tanks shall be at
least 30 inches. A liquid depth greater than 6 feet shall not be
considered in determining tank capacity.
2.4 TANK COMPARTMENTS: Septic tanks may be divided into
compartments, or separate tanks may be installed in series, up to
a maximum of 3, provided the following requirements are
A. The volume of the first compartment or tank must equal
or exceed the volume of any other compartment.
B. No compartment or tank shall have an inside horizontal
dimension less than 24 inches.
C. Inlets and outlets shall be designed as specified for
tanks, except when a partition wall is used to form a
multi-compartment tank. Under such conditions, an opening in the
partition may be used to allow for flow between compartments,
provided the minimum dimension of the opening is 4 inches, the
cross-sectional area is not less than 30 square inches, and the
mid-point is below the liquid surface a distance approximately
equal to 40% of the liquid depth of the tank.
2.5 INLETS AND OUTLETS:
A. Inlets and outlets of tanks or compartments shall be
submerged or baffled to divert incoming flow toward the tank
bottom and minimize the discharge of sludge or scum in the
B. Sanitary Tees may be used in lieu of baffled inlet or
C. All outlet baffles shall extend below the liquid
surface a distance equal to approximately 40% of the liquid
depth. Space between the baffle top and the underside of the tank
cover shall be at least 1 inch.
D. Scum storage volume shall consist of 15% or more of
the required liquid capacity of the tank and shall be provided in
the space between liquid surface and top of inlet devices, which
shall be set at least 1 inch below the underside of the tank
E. Inlets and outlets shall allow free venting of tank
gases back through the drainage system.
F. The inlet invert shall be at least 1 inch above outlet
2.6 ACCESS TO TANK:
A. Access to inlet and outlet devices shall be provided
through properly placed openings not less than 18 inches in
minimum horizontal dimension.
B. The top of the tank shall be at least 6 inches below
C. If the top of the tank is located more than 18 inches
below finished grade, all access openings required by sub-section
(1) above, shall be extended to within 18 inches of the finished
2.7 ABANDONED SEPTIC TANKS: Septic tanks, cesspools and
seepage pits which are no longer in use shall be completely
pumped and filled with sand or soil.
2.8 DISCHARGE TO ABSORPTION SYSTEM: Septic tank effluent
shall be conducted to the absorption system through a watertight
sewer line meeting the requirements for wastewater drainage lines
as contained in R317-5-1.13(A), (B), and (F). Tees, wyes, or
other distributing devices may be used as needed. If a
distribution box is used, it shall be of sufficient size to
accommodate the necessary distribution line connections. Outlet
inverts shall be at the same elevation and at least 1 inch below
the inlet invert. Conveyance to the absorption system must be
adequately sized to handle peak hydraulic flow.
R317-5-3. Absorption Systems.
3.1 GENERAL REQUIREMENTS:
A. Suitable soil exploration, to a depth of about 10
feet, or at least 4 feet below the bottom of the proposed
absorption systems and percolation tests, shall be made to
provide information on subsoil conditions. Percolation tests and
soil exploration reports shall be completed and submitted as part
of the engineering report for the disposal facility. After
January 1, 2002, the soil evaluation and percolation tests must
be done in accordance with certification requirements in R317-11.
A minimum of 5 percolation tests must be conducted at different
sites for each disposal system. Additional tests may be required,
where necessary to adequately evaluate the total absorption
system or where there is significant variability in test results.
In general, the system will be sized based on the slowest
stabilized percolation test rate. Soil logs should be prepared in
accordance with the Unified Soil Classification System by a
qualified individual. Requirements outlined in R317-5-4.1 and
Table 5-8 will be helpful in developing this
B. Absorption devices, including seepage pits or
trenches, placed in sloping ground should be so constructed that
the horizontal distance between the distribution line and the
ground surface is at least 10 feet.
C. Soil having excessively high permeability, such as
gravel with large voids, affords little filtering and is
unsuitable for absorption systems. Percolation rates (R317-5-4.1)
of approximately 5 minutes per inch or less usually will not be
The extremely fine-grained "blow sand" found in
some parts of Utah is generally unsuitable for absorption systems
and should be avoided. If no choice is available, systems may be
constructed in such material, provided it is within the required
percolation range specified in this code, and the required area
is calculated on the minimum percolation rate (60 minutes per
inch for absorption fields and 30 minutes per inch for absorption
D. Absorption system excavations may be made by machinery
provided that the soil in the bottom and sides of the excavation
is not compacted. Strict attention shall be given to the
protection of the natural absorption properties of the soil.
Absorption systems shall not be excavated when the soil is wet
enough to smear or compact easily. All smeared or compacted
surfaces should be raked to a depth of one inch, and loose
material removed before the filter material is placed in the
absorption system excavation.
E. Effluent distribution lines or pipe shall be
perforated and should consist of 4-inch diameter pipe of
appropriate material which has demonstrated satisfactory results
for the given application. The distribution pipe shall be bedded
true to line and grade, uniformly and continuously supported on
firm, stable material.
F. The coarse material in the absorption system shall
consist of crushed stone, gravel, or similar material of
equivalent strength and durability. It shall be free from fines,
dust, sand or clay. The top of the stone or gravel shall be
covered with a pervious material such as an acceptable synthetic
filter fabric, a 2-inch compacted layer of straw, or similar
material before being covered with earth backfill to prevent
infiltration of backfill into the stone or gravel.
G. Distribution pipes placed under driveways or other
areas subjected to heavy loads shall receive special design
considerations to insure against crushing or disruption of
alignment. Absorption area under driveways or pavement shall not
be considered in determining the minimum required absorption
H. Absorption systems shall be backfilled with earth that
is free from debris and large rocks. The first 4 to 6 inches of
soil backfill should be hand placed. Distribution pipes shall not
be crushed or misaligned during backfilling. When backfilling,
the earth should be mounded slightly above the surface of the
ground to allow for settlement.
I. Heavy equipment shall not be driven in or over
absorption systems during backfilling or after
J. That portion of absorption system below the top of
distribution pipes shall be in natural soil. Under unusual
circumstances the Director may allow installation in acceptably
stabilized earth fill. The earth fill and location will have to
be evaluated on a case-by-case basis, taking into consideration
the soil characteristics and degree of consolidation of the fill
K. Soil and Ground Water Requirements. In areas where
absorption systems are to be constructed, soil cover must be
adequate to insure at least 4 feet of soil between bedrock or any
other impervious formation, and the bottom of absorption systems.
Maximum ground water elevation must be at least 2 feet below the
bottom of absorption systems and at least 4 feet below finished
L. Replacement Area for Absorption System. Adequate and
suitable land shall be reserved and kept free of permanent
structures, traffic, or adverse soil modification for replacement
of the absorption system. Suitability must be demonstrated
through soil exploration and percolation tests results.
3.2 ABSORPTION FIELDS: Absorption fields are the
preferred type of absorption system. They consist of a series of
gravel-filled trenches provided with perforated pipes designed to
distribute septic tank effluent into the gravel fill, from which
it percolates through the trench walls and bottom into the
surrounding sub-surface soil.
A. Design of absorption fields shall be as outlined in
Tables 5-3 and 5-4.
ABSORPTION FIELD CONSTRUCTION DETAILS
ITEMS UNITS MINIMUM MAXIMUM Number of lateral trenches 2 - Length of trenches Feet - 100 Width of trenches Inches 12 36 Slope of pipe (bottom) In./100 ft. Level Level Depth of coarse material: Under pipe Inches 6 - Under pipe located within 10 ft. of trees Inches 12 - Over pipe Inches 2 - Size of coarse material Inches 3/4 2-1/2 Depth of backfill over coarse material Inches 6 -
SIZE AND MINIMUM SPACING FOR ABSORPTION FIELD TRENCHES
Minimum Spacing of wall to Trenches Width of wall (ft.) trench at bottom (inches) 12 to 18 6.0 18 to 24 6.5 24 to 30 7.0 30 to 36 7.5
B. The minimum absorption area (total bottom area of
trenches) of the absorption field shall be determined from the
following equation but in no case the maximum allowable
application rate shall exceed 2.2 gallons per square foot per
Q = 5 / square root of t Where Q = maximum rate of effluent application to the soil in gallons per square foot per day t = stabilized percolation rate in minutes per inch Percolation tests shall be performed as specified in R317-5-4.1. Rates in excess of 60 minutes per inch indicate a soil unsuitable for absorption field construction. C. Wherever possible all trench bottoms should be
constructed at the same elevation. Distribution pipes and
trenches should be level and should be connected at both ends to
provide a continuous system. If ground surface slope is too steep
to permit a level installation, then a system of serial trenches
following land contours should be used, with each trench and
distribution pipe being constructed level but at a different
elevation. A schematic diagram showing the recommended layout of
trenches and distribution systems is available from the
1. The system should include drop boxes which should
generally conform to the detail in Appendix 1 and should operate
in such a manner that a trench will be filled with wastewater to
the depth of the gravel fill before the wastewater flows to the
next lower trench. The drop boxes shall be watertight and should
be provided with a means of access at the top.
2. The lines between the drop boxes should be a minimum
of 4 inches in diameter and should be watertight with direct
connections to the distribution box. They should be laid in a
trench excavated through undisturbed earth to the exact depth
required. Backfill should be carefully tamped.
3.3 ABSORPTION BEDS: Absorption beds consist of large
excavated areas provided with gravel fill in which effluent
distribution lines are laid. They may be used in place of
absorption fields when trenches are not considered desirable, and
shall conform to requirements applying to absorption fields,
except for the following:
A. They shall comply with construction details specified
in Table 5-5.
ABSORPTION BED CONSTRUCTION DETAILS
ITEM UNIT MINIMUM MAXIMUM Distance between distribution lines Feet - 6 Distance between distribution lines and wall Feet - 3 Depth to bottom of bed Feet 1-1/2 - Size of coarse material Inches 3/4 2-1/2 Depth of coarse material Under pipe Inches 6 - In bed within 10 ft. of trees Inches 12 - Over pipe Inches 2 - Depth of backfill over coarse material Inches 6 -
B. Required absorption area (total bottom area of bed)
shall be determined from the following equation, but in no case
shall it exceed 1.1 gallons per square foot per day.
Q = 2.5/square root of t
Where Q = maximum rate of effluent application to the
soil in gallons per square foot per day.
t = stabilized percolation rate in minutes per
Percolation tests shall be performed as specified in
R317-5-4.1. Rates in excess of 30 minutes per inch indicate a
soil unsuitable for absorption bed construction.
3.3 SEEPAGE PITS: If absorption fields or beds are not
feasible, seepage pits will be considered. These consist of deep
pits which receive septic tank effluent and allow it to seep
through sidewalls into the adjacent subsurface soil. Seepage pits
may be either hollow lined or filled with clean coarse material.
They shall conform to the following requirements:
A. Number and size of seepage pits required shall be
determined by calculation of seepage rate into each stratum of
soil encountered in pit sidewall by reference to Table 5-8. Only
pervious side-wall area below the inlet shall be considered. In
order to calculate a sidewall seepage rate a representative
number of soil explorations shall be evaluated to adequately
identify the type and depth of each soil stratum expected
throughout the absorption area. In general, a minimum of 5
explorations will be evaluated. This information shall be
provided in the engineering report.
B. For the purposes of confirming an appropriate sidewall
seepage rate, the owner shall submit a statement describing the
character and thickness of each stratum of soil encountered
during pit construction. Soil classification and assumed seepage
rates shall be as specified in Table 5-8 except when valid
seepage measurements are available.
C. The lining may be brick, stone, block or similar
materials, at least 4 inches thick, laid in cement mortar above
the inlet and with tight butted joints below the inlet. The
annular space between the lining and the earth wall shall be
filled with crushed rock or gravel varying in diameter from 3/4
inch to 2-1/2 inches.
D. A structurally sound and otherwise suitable top shall
be provided. Structural design and materials used throughout
shall assure a durable safe structure.
E. If more than one seepage pit is provided, the
installation may be operated in series or parallel with
distribution of effluent as specified in R317-5-2.1(G).
F. For hollow lined pits, the inlet pipe should extend
horizontally at least 1 foot into the pit with a tee to divert
flow downward and prevent washing and eroding the
G. For filled pits a thin layer of crushed rock or gravel
ranging from 3/4 to 2-1/2 inches in diameter, free from fines,
sand, clay or organic material shall cover the coarse material to
permit leveling of the distribution pipe.
SEEPAGE PITS CONSTRUCTION DETAILS
ITEM UNIT MINIMUM MAXIMUM Generals Distance between seepage pits feet 12(a) - Diameter of distribution pipe inches 4 - Size of coarse material inches 3/4 12 Bottom of pit to maximum ground water feet 2 - Bottom of Pit in unsuitable soil or bedrock formations feet 4 - Hollow-lined Pits: Width of annular space between lining and sidewall containing crushed rock (3/4 to 2-1/2 inches in diameter) inches 6 - Thickness of brick, or block linings inches 4(b) Filled Pits: Depth of coarse material: Under pipe feet 4 - Over distribution pipe inches 2 - Depth of backfill over material inches 6 - Footnotes: (a) See Table 5-1 (b) Pre-manufactured linings may be approved with thicknesses less than 4 inches.
3.5 SEEPAGE TRENCHES (MODIFIED SEEPAGE PITS):
Seepage trenches are considered as modified seepage pits
and consist of deep trenches filled with clean, coarse material.
They shall conform to the requirements applying to seepage pits
except for the following:
A. The effective sidewall absorption area shall be
considered as the outside surface of the seepage trench (vertical
sidewall area) calculated below the inlet or distribution pipe.
Only pervious sidewall area below the inlet shall be
SEEPAGE TRENCH DETAIL
ITEM UNIT MINIMUM MAXIMUM Seepage trench width feet 2 - Seepage trench length feet - 100 Effluent Distribution pipe Diameter inches 4 - Slope percent level level Distance between seepage trenches feet 12(a) - Footnote: (a) See Table 5-1.
SEEPAGE TRENCHES AND PITS
ALLOWABLE SIDEWALL SEEPAGE RATES
SYMBOL AND CHARACTER OF SOIL GALLONS/ BY UNIFIED SOIL CLASSIFICATION DAY/ SYSTEM SQ. FT. Hardpan or bedrock (including fractured bedrock with little or no fines). 0 GW Well graded gravels, gravel-sand mixtures little or no fines. 1.55 GP Poorly graded gravels or gravel-sand mixtures, little or no fines. 1.55 SW Well graded sands, gravelly sand, little or no fines. 1.20 SP Poorly graded sands or gravelly sands, little or no fines. 1.20 SM Silty sand, sand-silt mixtures. 0.8 GM Silty gravels, poorly graded gravel-sand-silt mixtures. 1.0 GC Clayey gravels, gravelly-sand-clay mixtures. 0.45(a) SC Clayey sands, sand-clay mixtures. 0.45(a) ML Inorganic silts and very fine sand, rock flour, silt or clayey find sands or clayey silts with slight plasticity. 0.45(a) MH Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic silts. 0.45(a)(b) CL Inorganic clays or low to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays. 0.45(a)(b) CH Inorganic clays of high plasticity, fat clays. 0 OL Organic silts and organic silty clays of low plasticity. 0 OH Organic clays of medium to high plasticity, organic silts. 0 PT Peat and other highly organic silts. 0 Other Impervious formations. 0 Footnotes: (a) For the purpose of this table, whenever there are reasonable doubts regarding the suitability and estimated absorption capacities of soils, percolation tests shall be conducted in those soils in accordance with R317-4-1. Soils within the same classification may exhibit extreme variability in permeability, depending on the amount and type of clay and silt present. The following soils categories, SC,GC, and ML, MH and CL soils, may prove unsatisfactory for absorption systems, depending upon the percentage and type of fines present. (b) These soils are usually considered unsuitable for absorption systems, but may be suitable, depending upon the percentage and type of fines in coarse-grained porous soils, and the percentage of sand and gravels in fine-grained soils.
R317-5-4. Percolation Tests.
A. General Requirements.
1. A percolation test measures the rate which subsurface
soil absorbs water for the purpose of identifying porous soil
strata and site suitability for absorption systems, and is also a
basis for estimating the design criteria of such systems to
insure a reasonably long lifespan.
2. While percolation tests constitute a valuable guide
for successful operation of disposal systems, considerable
judgment must be used in applying the results. Percolation test
results shall not be presumptive, prima facie, or conclusive
evidence as to the suitability for absorption systems. Such
percolation tests may be considered and analyzed as one of many
criteria in determining soil suitability for absorption systems.
There is no need for conducting percolation tests when the soil
or other site conditions are clearly unsuitable.
3. When percolation tests are made, such tests shall be
made at points and elevations selected as typical of the area in
which the absorption system will be located. Consideration should
be given to the finished grades of building sites so that test
results will represent the percolation rate of the soil in which
absorption systems will be constructed. After the suitability of
any area to be used for absorption systems has been evaluated and
approved for construction, no grade changes shall be made to this
area unless the health authority is notified and a reevaluation
of the area's suitability is made prior to the initiation of
B. Required Test Procedures.
1. Test results when required shall be considered an
essential part of plans for absorption systems and shall be
submitted on a signed "Percolation Test Certificate" or
equivalent, certifying that the tests were conducted in
accordance with these requirements, and indicating the depth and
rate of each test in minutes per inch, the date of the tests, the
logs of the soil exploration pits, a statement of the present and
maximum ground water table, and all other factors affecting
percolation test results. Percolation tests shall be conducted at
the owner's expense by or under the supervision of a
registered sanitarian, registered engineer, or other qualified
person approved by the health authority in accordance with the
(a) Conditions Prohibited for Test Holes.
Percolation tests shall not be conducted in test holes
which extend into ground water, bedrock, or frozen ground. Where
a fissured soil formation is encountered, tests shall be made
under the direction of the health authority.
(b) Number and Location of Percolation Tests.
One or more tests shall be made in separate test holes on
the proposed absorption system site to assure that the results
are representative of the soil conditions present.
Where questionable or poor soil conditions exist, the
number of percolation tests and soil explorations necessary to
yield accurate, representative information shall be determined by
the health authority and may be accepted only if conducted with
an authorized representative present.
(c) Type, Depth, and Dimensions of Test Holes.
Test holes shall be dug or bored, preferably with hand
tools such as shovels or augers, etc., and shall have horizontal
dimensions ranging from 4 to 18 inches (preferably 8 to 12
inches). The vertical sides shall be at least 12 inches deep,
terminating in the soil at an elevation 6 inches below the bottom
of the proposed absorption system.
2. Test Procedure for Sandy or Granular Soils
For tests in sandy or granular soils containing little or
no clay, the hole shall be carefully filled with clear water to a
minimum depth of 12 inches over the gravel and the time for this
amount of water to seep away shall be determined. The procedure
shall be repeated and if the water from the second filling of the
hole at least 12 inches above the gravel seeps away in 10
minutes, or less, the test may proceed immediately as
(a) Water shall be added to a point not more than 6
inches above the gravel.
(b) Thereupon, from the fixed reference point, water
levels shall be measured at 10 minute intervals for a period of 1
(c) If 6 inches of water seeps away in less than 10
minutes a shorter time interval between measurements shall be
used, but in no case shall the water depth exceed 6
(d) The final water level drop shall be used to calculate
the percolation rate.
3. Test Procedure for Other Soils Not Meeting the Above
The hole shall be carefully filled with clear water and a
minimum depth of 12 inches shall be maintained above the gravel
for at least a 4-hour period by refilling whenever necessary.
Water remaining in the hole after 4 hours shall not be removed.
Immediately following the saturation period, the soil shall be
allowed to swell not less than 16 hours or more than 30 hours.
Immediately following the soil swelling period, the percolation
rate measurements shall be made as follows:
(a) Any soil which has sloughed into the hole shall be
removed and water shall be adjusted to 6 inches over the
(b) Thereupon, from the fixed reference point, the water
level shall be measured and recorded at approximately 30 minute
intervals for a period of 4 hours unless 2 successive water level
drops do not vary more than 1/16 of an inch and indicate that an
approximate stabilized rate has been obtained.
(c) The hole shall be filled with clear water to a point
not more than 6 inches above the gravel whenever it becomes
(d) Adjustments of the water level shall not be made
during the last 3 measurement periods except to the limits of the
last water level drop.
(e) When the first 6 inches of water seeps away in less
than 30 minutes, the time interval between measurements shall be
10 minutes, and the test run for 1 hour.
(f) The water depth shall not exceed 6 inches at any time
during the measurement period.
(g) The drop that occurs during the final measurement
period shall be used in calculating the percolation
4. Calculation of Percolation Rate.
The percolation rate is equal to the time elapsed in
minutes for the water column to drop, divided by the distance the
water dropped in inches or fractions thereof.
5. Using Percolation Rate to Determine Absorption
The minimum or slowest percolation rate shall be used in
calculating the required absorption area.
C. Recommendations to Enhance Test Procedures.
1. Soil Exploration Pit Prerequisite to Percolation
Since the appropriate percolation test depth depends on
the soil conditions at a specific site, the percolation test
should be conducted only after the soil exploration pit has been
dug and examined for suitable and porous strata and ground water
table information. Percolation test results should be related to
the soil conditions found.
2. Test Holes to Commence in Specially Prepared
All percolation test holes should commence in specially
prepared larger excavations (preferably made with a backhoe) of
sufficient size which extend to a depth approximately 6 inches
above the strata to be tested.
3. Preparation of Percolation Test Hole. Carefully
roughen or scratch the bottom and sides of the hole with a knife
blade or other sharp pointed instrument in order to remove any
smeared soil surfaces and to provide an open, natural soil
interface into which water may percolate. Nails driven into a
board will provide a good instrument to scarify the sides of the
hole. Remove all loose soil from the bottom of the hole. Add up
to 3 inches of clean coarse sand or pea-sized gravel to protect
the bottom from scouring or sealing with sediment when water is
Caving or sloughing in some test holes can be prevented
by placing in the test hole a wire cylinder or perforated pipe
surrounded by clean coarse gravel.
4. Saturation and Swelling of the Soil. It is important
to distinguish between saturation and swelling. Saturation means
that the void spaces between soil particles are full of water.
This can be accomplished in a relatively short period of time.
Swelling is a soil volume increase caused by increase intrusion
of water into the individual soil particles. This is a slow
process, especially in clay-type soil, and is the reason for
requiring a prolonged swelling period.
5. Placing Water in Test Holes.
Water should be placed carefully into the test holes by
means of a small-diameter siphon hose or other suitable method to
prevent washing down the side of the hole.
6. Percolation Rate Measurement, General.
Necessary equipment should consist of a tape measure
(with at least 1/16-inch calibration) or float gauge and a time
piece or other suitable equipment. All measurements shall be made
from a fixed reference point near the top of the test hole to the
surface of the water.
KEY: water pollution, sewerage,
Date of Enactment or Last Substantive Amendment: [
September 24, 2015]
Notice of Continuation: June 18, 2012
Authorizing, and Implemented or Interpreted Law: 19-5
More information about a Notice of Proposed Rule is available online.
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For questions regarding the content or application of this rule, please contact Judy Etherington at the above address, by phone at 801-536-4344, by FAX at 801-536-4301, or by Internet E-mail at firstname.lastname@example.org.