Utah Administrative Code, Rule R317-4, Section R317-4-6 - Design Requirements | Utah Administrative Code

(1) An onsite wastewater system may not be suitable in some areas and situations. Location and installation of each system shall be such that with reasonable maintenance, it shall function in a sanitary manner and may not create a nuisance, public health hazard, or endanger the quality of any waters of the state. In determining a suitable location for each system, due consideration shall be given to such factors as:

(a) the minimum setbacks in Section R317-4-13 Table 2;

(b) size and shape of the lot;

(c) slope of natural and final grade;

(d) location of existing and future water supplies;

(e) depth of ground water and bedrock;

(f) soil characteristics and depth;

(g) potential flooding or storm catchment;

(h) possible expansion of the system; and

(i) future connection to a public sewer system.

(2) Any onsite wastewater system, including the replacement area, shall conform to the minimum setback distances in Section R317-4-13 Table 2.

(3) Any absorption system, including the replacement area, shall conform to the ground slope requirements in Section R317-4-4.

(4) Any design for an onsite wastewater system shall include an estimate of wastewater quantity.

(a) The wastewater quantity estimate for a single-family dwelling shall be a minimum of 300 gallons per day for 1 or 2 bedroom, and 150 gallons per day for each additional bedroom.

(b) For any non-residential facility, the quantity of wastewater shall be determined accurately, preferably by actual measurement. Metered water supply figures for similar installations can usually be relied upon, providing the non-disposable consumption, if any, is subtracted. Where this data is not available, the minimum design flow figures in Section R317-4-13 Table 3 shall be used to make estimates of flow.

(c) In no event shall the anticipated maximum daily wastewater flow exceed the capacity for which a system is designed.

(5) Effluent shall be treated to levels at or below the defined parameters of non-domestic effluent before being discharged into an absorption system.

(6) Building sewer shall meet the following requirements:

(a) The building sewer shall have a minimum inside diameter of 4 inches and shall comply with the minimum standards in Section R317-4-13 Table 4. If the sewer leaving the house is 3 inches, the building sewer may be 3 inches.

(b) Building sewers shall be laid on a uniform minimum slope of not less than 1/4 inch per foot or 2.08% slope.

(c) The building sewer shall have a minimum of one cleanout and cleanouts every 100 feet.

(i) A cleanout is also required for each aggregate horizontal change in direction exceeding 135 degrees.

(ii) 90 degree ells are not recommended.

(d) The building sewer shall be separated from water service pipes in separate trenches, and by at least 10 feet horizontally, except that they may be placed in the same trench when all the following conditions are met.

(i) The bottom of the water service pipe, at all points, shall be at least 18 inches above the top of the building sewer.

(ii) The water service pipe shall be placed on a solid shelf excavated at one side of the common trench with a minimum clear horizontal distance of at least 18 inches from the sewer or drain line.

(iii) The number of joints in the water service pipe should be kept to a minimum, and the materials and joints of both the sewer and water service pipes shall be of strength and durability to prevent leakage under adverse conditions.

(iv) If the water service pipe crosses the building sewer, it shall be at least 18 inches above the latter within 10 feet of the crossing. Joints in water service pipes should be located at least 10 feet from such crossings.

(e) Each building sewer placed under driveways or other areas subjected to heavy loads shall receive special design considerations to ensure against crushing or disruption of alignment.

(7) Each septic tank shall meet the requirements of Subsection R317-4-14(1) Appendix A and be approved by the division. Septic tanks shall be constructed of sound, durable, watertight materials that are not subject to excessive corrosion, frost damage, or decay. They shall be designed to be watertight, and to withstand all expected physical forces.

(a) A septic tank that serves a non-residential facility shall have a liquid capacity of at least 1-1/2 times the designed daily wastewater flow. In all cases the capacity shall be at least 1,000 gallons.

(b) The capacity of a septic tank that serves a single-family dwelling shall be based on the number of bedrooms that can be anticipated in the dwelling served, including the unfinished space available for conversion as additional bedrooms. Unfinished basements shall be counted as a minimum of one additional bedroom.

(i) The minimum liquid capacity of the tank shall be 1,000 gallons for up to three bedroom homes.

(ii) The minimum liquid capacity of the tank shall be 1,250 gallons for four bedroom homes.

(iii) Two hundred fifty gallons per bedroom shall be added to the liquid capacity of the tank for each additional bedroom over four bedrooms.

(c) The regulatory authority may require a larger capacity than specified in this subsection as needed for unique or unusual circumstances.

(d) Multiple septic tanks may be installed in series.

(i) No tank in the series may be smaller than 1,000 gallons.

(ii) The capacity of the first tank shall be at least two-thirds of the required total septic tank volume. If a compartmented tank is used, the compartment of the first tank shall have this two-thirds capacity. A membrane bioreactor system may include the balance tank as a second tank in series where the volume of the balance tank is included in the total required septic tank liquid storage capacity.

(iii) The connecting pipe between each successive tank shall meet the slope requirements of the building sewer and shall be unrestricted except for the inlet to the first tank and the outlet for the last tank.

(iv) The maximum number of tanks and compartments in series may not exceed three.

(e) Each septic tank inlet or outlet device shall conform to the following:

(i) Approved tanks with offset inlets may be used where they are warranted by constraints on septic tank location.

(ii) Multiple outlets from septic tanks shall be prohibited unless preauthorized by the regulatory authority.

(iii) A gas deflector may be added at the outlet of the tank to prevent solids from entering the outlet pipe of the tank.

(f) Any septic tank may have an effluent screen installed at the outlet of the terminal tank. The screen shall prevent the passage of solid particles larger than a nominal 1/8 inch diameter sphere. The screen shall be easily removable for routine servicing by installing a riser to the ground surface, with an approved cover. An effluent screen is required for each non-domestic wastewater system, unless screening is achieved by some other means acceptable to the regulatory authority.

(g) Adequate access to the tank shall be provided to facilitate inspection, pumping, servicing, and maintenance, and shall have no structure or other obstruction placed over it and shall conform to all the following requirements.

(i) Watertight risers are required, extending to within 6 inches of the surface of the ground when soil covering the septic tank is greater than 6 inches. Preferably, the riser should be brought up to the final grade to encourage periodic servicing and maintenance.

(A) If a septic tank is located under paving or concrete, risers shall be extended up through the paving or concrete.

(B) If non-domestic wastewater is generated, risers shall be extended to the final grade.

(ii) The inside diameter of the riser shall be a minimum of 20 inches.

(iii) Each riser cover shall be designed and constructed in such a manner that:

(A) it may not pass through the access openings;

(B) it shall be child-proof when closed;

(C) it shall prevent entrance of surface water, dirt, or other foreign materials; and

(D) it shall seal odorous gases in the tank.

(iv) Each riser shall be constructed of durable, structurally sound materials that are approved by the regulatory authority and designed to withstand expected physical loads and corrosive forces.

(v) When a septic tank capacity exceeds 3,000 gallons, a minimum of two access risers shall be installed.

(h) Each septic tank installation located in a high groundwater area shall conform to the following additional requirements:

(i) Each septic tank located in a high groundwater area shall be designed with the appropriate weighted or anti-buoyancy device to prevent flotation in accordance with the manufacturer's recommendations.

(ii) The building sewer inlet of a septic tank may not be installed at an elevation lower than the highest anticipated groundwater elevation.

(A) If the tank serves a mound, packed bed, or membrane bioreactor alternative system and has an electronic control panel capable of detecting water intrusion, the building sewer inlet of the tank may be installed below the maximum anticipated groundwater elevation.

(B) Any component below the anticipated maximum ground water elevation shall be water tightness tested.

(i) The minimum depth of cover over a septic tank shall be at least 6 inches and a maximum of 48 inches at final grading. For unusual situations, the regulatory authority may allow deeper burial provided the following conditions are met.

(A) Each septic tank shall be approved by the division for the proposed depth and burial cover load.

(B) Each riser shall:

(I) be installed over each access opening of the inlet and outlet baffles or sanitary tees; and

(II) conform to Subsection R317-4-6(7)(g), except each riser shall be at least 24 inches in diameter.

(8) A grease interceptor tank or automatic grease removal device may be required by the regulatory authority to receive the drainage from fixtures and equipment with grease-laden waste. It shall be sized according to the current Plumbing Code.

Any grease interceptor tank or automatic grease removal device installed in the ground shall conform to Subsection R317-4-6(7)(g) for accessibility and installation, except risers are required and shall be brought to the surface of the ground. Each interior compartment shall be accessible for inspecting, servicing, and pumping.

(9) Installation of each pump and recirculation tank shall conform to the following:

(a) Each pump or recirculation tank shall be constructed of sound, durable, watertight materials that are not subject to excessive corrosion, frost damage, or decay. The tank shall be designed to be watertight, and to withstand all expected physical forces;

(b) Pump tank volume shall have a liquid capacity adequate for the minimum operating volume that includes the dead space, dosing volume, and surge capacity, and shall have the emergency operation capacity of:

(i) storage capacity for the system design daily wastewater flow;

(ii) at least two independent power sources with appropriate wiring installed; or

(iii) other design considerations approved by the regulatory authority that do not increase public health risks if pump failure occurs.

(c) Each tank shall conform to Subsection R317-4-6(7)(g) for accessibility and installation, except risers are required and shall be brought to the surface of the ground. Each interior compartment shall be accessible for inspecting, servicing, and pumping; and

(d) Each outlet of any septic tank upstream of each pump tank shall be fitted with an effluent screen, unless a pump vault is used in a pump tank.

(10) A pump vault may be used when approved by the regulatory authority.

(a) The vault shall be constructed of durable material and resistant to corrosion.

(b) The vault shall have an easily accessible screen with 1/8 inch openings or smaller.

(c) Each component of the vault shall be accessible from the surface.

(d) When a pump vault is used in a septic tank:

(i) The tank size shall be increased by the larger of the following:

(A) two hundred fifty gallons; or

(B) ten percent of the required capacity of the tank.

(ii) At least two independent power sources with appropriate wiring, or other design considerations approved by the regulatory authority that do not increase public health risks, shall be installed.

(iii) The maximum drawdown within the tank shall be no more than 3 inches per dose.

(11) Each pump shall be designed as detailed in Subsection R317-4-14(2) Appendix B.

(12) When any onsite wastewater system is required to have effluent sampling or receives non-domestic wastewater, the system shall include a sampling port at an area approved by the regulatory authority capable of sampling effluent before the absorption system.

(13) Each effluent sewer shall conform with the following:

(a) The effluent sewer shall have a minimum inside diameter of 4 inches and shall comply with the minimum standards in Section R317-4-13 Table 4;

(b) The effluent sewer shall extend at least 5 feet beyond the septic tank before entering the absorption system;

(c) The effluent sewer shall be laid on a uniform minimum slope of not less than 1/4 inch per foot or 2.08% slope. When it is impractical, due to structural features or the arrangement of any building, to obtain a slope of 1/4 inch per foot, a sewer pipe of 4 inches in diameter or larger may have a slope of not less than 1/8 inch per foot or 1.04% slope when approved by the regulatory authority;

(d) The effluent sewer line shall have cleanouts at least every 100 feet; and

(e) Each effluent sewer placed under a driveway or other area subjected to heavy loads shall receive special design considerations to ensure against crushing or disruption of alignment.

(14) An absorption system shall consist of one or more absorption trenches, absorption beds, deep wall trenches, or seepage pits.

Absorption trenches may be standard trenches, chambered trenches, or bundled synthetic aggregate trenches.

(a) Each absorption system shall meet general requirements.

(i) A replacement area for each absorption system shall have adequate and suitable land which shall be reserved and kept free of permanent structures, traffic, or adverse soil modification for 100% replacement of each absorption system. If approved by the regulatory authority, the area between standard trenches or deep wall trenches may be regarded as replacement area. In lieu of a replacement area, two complete absorption systems shall be installed with a diversion valve. The valve shall be accessible from the final grade. The valve should be switched at least annually.

(ii) The site of the initial and replacement absorption system shall be protected and may not be covered by asphalt, concrete, structures, or be subject to vehicular traffic, or other activity that would adversely affect the soil, such as construction material storage, or soils storage. This protection applies before and after construction of the onsite wastewater system.

(iii) Each absorption system shall be sized based on Section R317-4-13 Table 5 or R317-4-13 Table 6.

(iv) Many different criteria may be used in designing an absorption system, the choice depending on the size and shape of the available areas, the capacity required, and the topography of the dispersal area.

(A) Each absorption system shall comply with the setbacks in Section R317-4-13 Table 2.

(B) An absorption system may be placed in sloping ground. Any absorption system placed in 10% or greater sloping ground shall be designed so that there is a minimum of 10 feet of undisturbed earth measured horizontally from the bottom of the distribution line to the ground surface. This requirement does not apply to drip irrigation.

(C) That portion of the absorption system below the top of distribution pipes shall be in undisturbed natural earth.

(D) All piping, chambers, and the bottoms of absorption system excavations shall be designed level.

(E) Distribution pipe for gravity-flow absorption systems shall be 4 inches in diameter and shall comply with the minimum standards in Section R317-4-13 Table 4.

(I) The pipe shall be penetrated by at least two rows of round holes, each 1/2 inch in diameter, and located at about 6 inch intervals. The perforations should be located at about the five o'clock and seven o'clock positions on the pipe.

(II) The open ends of the pipes shall be capped.

(F) Absorption system laterals should be designed to receive proportional flows of wastewater.

(G) Drain media shall be covered with a barrier material before being covered with earth backfill.

(H) The following prohibitions shall apply to the design of an absorption system:

(I) In any gravity-flow absorption system with multiple distribution lines, the effluent sewer may not be in direct line with any one of the distribution pipes, except where drop boxes or distribution boxes are used.

(II) Any section of distribution pipe laid with non-perforated pipe may not be considered in determining the required absorption area.

(III) Perforated distribution pipe may not be placed under a driveway or other area subjected to heavy loads. A deep wall trench or filled seepage pit may be allowed beneath an unpaved driveway on a case-by-case basis by the regulatory authority, if the top of the distribution pipe is at least 3 feet below the final ground surface.

(b) Effluent distribution devices may be used to distribute effluent evenly throughout an absorption system.

(i) A distribution box may be used on level or nearly level ground. Each distribution box shall be watertight and constructed of durable, corrosion resistant material. Each distribution box shall be designed to accommodate an inlet pipe and the necessary distribution lines.

(A) The outlet inverts of the distribution box may not be less than 1 inch below the inlet invert.

(B) Each distribution box shall have a riser brought to final grade.

(ii) Each drop boxes shall be watertight and constructed of durable, corrosion resistant material and may be used to distribute effluent within the absorption system and shall meet the following requirements:

(A) Each drop box shall be designed to accommodate an inlet pipe, an outlet pipe leading to the next drop box, except for the last drop box, and one or two distribution pipes leading to the absorption system.

(B) The inlet pipe to the drop box shall be at least 1 inch higher than the outlet pipe leading to the next drop box.

(C) The invert of the distribution pipes shall be 1 through 6 inches below the outlet invert. If there is more than one distribution pipe, their inverts shall be at exactly the same elevation.

(D) Each drop box shall have a riser brought to final grade.

(iii) Effluent may be pumped to an absorption system.

(A) If a pump is used to lift effluent to an absorption system, the pump tank or pump vault shall meet the requirements of Subsection R317-4-6(9) or R317-4-6(10) and the pump and controls shall meet the requirements of Subsection R317-4-14(2) Appendix B.

(B) Pumping to an absorption system may not warrant any reductions to the absorption area.

(iv) Any tee, wye, ell, or other distributing device may be used as needed to distribute proportional flow to the branches of the absorption system. A clean out or other means of access from the surface shall be provided for any such device.

(c) Effluent shall be distributed evenly throughout an absorption system using various methods.

(i) In a location where the slope of the ground over the absorption system area is relatively flat, absorption trenches should be interconnected to produce a closed loop system and the trenches shall be installed at the same elevations.

(ii) If a non-closed loop design is used, effluent shall be proportionally distributed to each lateral.

(iii) Serial or sequential distribution may be used in absorption systems designed for sloping areas, or where absorption system elevations are not equal.

(A) Serial trenches shall be connected with a drop box or watertight overflow line in such a manner that a trench shall be filled before the effluent flows to the next lower trench.

(B) The overflow line shall be a 4-inch solid pipe with direct connections to the distribution pipes. It should be laid in a trench excavated to the exact depth required. Care must be exercised to ensure a block of undisturbed earth remains between trenches. Backfill should be carefully tamped.

(iv) Pressure distribution to an absorption system shall conform to the following general requirements:

(A) All requirements stated elsewhere in this rule for design, setbacks, construction and installation details, performance, repairs, and abandonment shall apply.

(B) Each system that uses this method shall be designed by a person certified at Level 3 in accordance with Rule R317-11.

(I) The designer shall submit details of all system components with the necessary calculations.

(II) The designer shall provide to the local health department and to the owner operation and maintenance instructions that include the minimum inspection levels in Section R317-4-13 Table 7 for the system.

(C) When a system utilizing pressure distribution exists on a property, notice of the existence of that system shall be recorded in the chain of title for that property.

(D) Pressure distribution may be permitted on any site meeting the requirements for an onsite wastewater system if conditions in this rule can be met. Pressure distribution should be considered when:

(I) effluent pumps are used;

(II) the flow from the dwelling or structure exceeds 3,000 gallons per day;

(III) soils are a Type 1 or have a percolation rate faster than five minutes per inch; or

(IV) soils are a Type 5 or have a percolation rate slower than 60 minutes per inch.

(E) The Utah Guidance for Performance, Application, Design, Operation and Maintenance: Pressure Distribution Systems document shall be used for design requirements, along with the following:

(I) Dosing pumps, controls and alarms shall comply with Subsection R317-4-14(2) Appendix B.

(II) Pressure distribution piping, pressure transport, manifold, lateral piping, and fittings shall meet PVC Schedule 40 standards or equivalent.

(III) The ends of lateral piping shall be constructed with sweep elbows or an equivalent method to bring the end of the pipe to final grade. The ends of the pipe shall be provided with threaded plugs, caps, or other devices acceptable to the regulatory authority to allow for access and flushing of the lateral.

(d) Each absorption system shall be designed according to the requirements for the specific absorption method selected.

(i) An absorption system shall be designed to follow the ground surface contours so that variation in excavation depth shall be minimized. The excavations may be installed at different elevations, but the bottom of each individual excavation shall be level throughout its length.

(ii) Each absorption system should be constructed as shallow as is possible to promote treatment and evapotranspiration.

(iv) Observation ports may be placed to observe the infiltrative surfaces of the trenches or beds.

(v) Absorption trenches shall conform to the following:

(A) The minimum required effective absorption area shall be calculated using Section R317-4-13 Table 5 or R317-4-13 Table 6.

(B) The effective absorption area of absorption trenches shall be calculated as the total bottom area of the excavated trench system in square feet.

(C) The minimum number of absorption trenches shall be two.

(D) The maximum length of an absorption trench, not including any connecting trench shall be 150 feet.

(E) The minimum spacing of absorption trenches from wall to wall shall be 7 feet.

(F) The minimum width of each absorption trench excavation shall be 24 inches.

(G) The maximum width of each absorption trench excavation shall be 36 inches.

(H) The minimum depth of each absorption trench excavation below the original, natural grade shall be 10 inches.

(I) The minimum depth of soil cover over each absorption trench shall be 6 inches.

(J) The minimum separation from the bottom of each absorption trench to:

(K) the anticipated maximum ground water table shall be 24 inches; and

(L) to unsuitable soil or bedrock formations shall be 48 inches.

(vi) Each standard trench shall conform to the following:

(A) The top of any distribution pipe may not be installed above original, natural grade.

(B) The distribution pipe shall be centered in the absorption trench and placed the entire length of the trench.

(C) Drain media shall extend the full width and length of the trench to a depth of at least 12 inches.

(D) The minimum depth of drain media under the distribution pipe shall be 6 inches.

(E) The minimum depth of drain media over the distribution pipe shall be 2 inches.

(F) The minimum depth of cover over the barrier material shall be 6 inches.

(vii) Each chambered trench shall conform to the following:

(A) Each chamber shall be certified under the International Association of Plumbing and Mechanical Officials (IAPMO) standard for plastic leaching chambers.

(B) The minimum required effective absorption area of chambered trenches shall be calculated:

(I) using 36 inches for Type A Chambers; and

(II) using 24 inches for Type B Chambers.

(C) The minimum required effective absorption area of chambered trenches shall be calculated using Section R317-4-13 Table 5 or R317-4-13 Table 6 and may be reduced by 30%.

(D) The chambered trenches shall be designed and installed in conformance with manufacturer recommendations, as modified by this rule.

(E) Type A chambers shall have:

(I) a minimum width of 30 inches; and

(II) a maximum trench excavation width of 36 inches.

(F) Type B chambers shall have:

(I) a minimum width of 22 inches; and

(II) a maximum trench excavation width of 24 inches.

(G) The minimum elevation of the inlet pipe invert from the bottom of the chamber shall be 6 inches.

(H) Each chambered trench shall have a splash plate under the inlet pipe or another design feature to avoid unnecessary channeling into the trench bottom.

(I) Any inlet and outlet effluent sewer pipe shall enter and exit the chamber endplate.

(J) The minimum depth of cover over any chamber shall be 12 inches. The depth of cover may be reduced to no less than 6 inches, if approved by the regulatory authority, considering the protection of absorption systems as required in Subsection R317-4-6(14)(a)(ii), and other activities, as determined by the authority.

(viii) Each bundled synthetic aggregate trench shall conform to the following:

(A) Each synthetic aggregate bundle shall meet IAPMO Standards for the General, Testing and Marking and Identification of the guide criteria for Bundled Expanded Polystyrene Synthetic Aggregate Units.

(B) The effective absorption area of a bundled synthetic aggregate trench shall be calculated as the total bundle length times the total bundle width in square feet.

(C) Each bundled synthetic aggregate trench shall be designed and installed in conformance with manufacturer recommendations, as modified by this rule.

(D) Only 12-inch diameter bundles are approved in this rule.

(E) For bundles with perforated pipe the minimum depth of synthetic aggregate under pipe shall be 6 inches.

(F) The width of each bundled synthetic aggregate trench shall require:

(I) three bundles laid parallel to each other with the middle bundle containing perforated pipe when designed for a 3 foot trench; or

(II) two bundles placed on the bottom, with another bundle containing perforated pipe placed on top of the other two bundles.

(G) The minimum depth of cover over the bundles shall be 12 inches. The depth of cover may be reduced to no less than 6 inches, if approved by the regulatory authority, considering the protection of absorption systems as required in Subsection R317-4-6(14)(a)(ii), and other activities, as determined by the authority.

(ix) Each absorption bed shall conform to the requirements applicable to absorption trenches, except for the following:

(A) The minimum required effective absorption area shall be calculated using Section R317-4-13 Table 5 or R317-4-13 Table 6.

(B) The effective absorption area of absorption beds shall be considered as the total bottom area of the excavated bed system in square feet.

(C) An absorption bed may be built over naturally existing soil types per Section R317-4-13 Table 5 or R317-4-13 Table 6.

(D) The bottom of the entire absorption bed shall be level.

(E) The distribution pipes or chambers shall be interconnected to produce a closed loop distribution system.

(F) The minimum number of laterals in an absorption bed shall be 2.

(G) The maximum length of laterals in an absorption bed shall be 150 feet.

(H) The maximum distance between laterals shall be 6 feet.

(I) The minimum distance between laterals and sidewalls shall be 1 foot.

(J) The maximum distance between laterals and sidewalls shall be 3 feet.

(K) The minimum distance between absorption beds shall be 7 feet.

(L) The minimum depth of an absorption bed excavation from original, natural grade shall be 10 inches.

(M) Absorption beds with drain media shall conform to the following:

(I) The minimum depth of drain media under a distribution pipe shall be 6 inches.

(II) The minimum depth of drain media over a distribution pipe shall be 2 inches.

(III) The minimum depth of cover over the barrier material shall be 6 inches.

(N) Each absorption bed with chambers shall require:

(I) Chambers shall be installed with sides touching, no separation allowed.

(II) All chambers shall be connected in a closed loop distribution system.

(III) The outlet side of the chamber runs shall be connected through the bottom port of the end plates.

(IV) No absorption area reduction factor shall be given for using chambers in absorption beds.

(V) The minimum depth of cover over the chambers shall be 12 inches.

(x) Each deep wall trench shall conform to the following:

(A) The minimum required effective absorption area shall be calculated using Section R317-4-13 Table 5 or R317-4-13 Table 6.

(B) The effective absorption area of deep wall trenches shall be calculated using the total trench vertical sidewall area below the distribution pipe. The bottom area and any highly restrictive or impervious strata or bedrock formations may not be considered in determining the effective sidewall absorption area.

(C) If a percolation test is used, it shall be conducted in accordance with Subsection R317-4-14(4) Appendix D and in the most restrictive soil horizon.

(D) The maximum length of any trench, not including any connecting trench, shall be 150 feet.

(E) The minimum spacing of trenches from wall to wall shall be 12 feet, or three times the depth of the media under the distribution pipe, whichever is the larger distance.

(F) Each deep wall trench shall:

(I) have a minimum effective sidewall depth of 2 feet;

(II) have a maximum effective sidewall depth of 10 feet; and

(III) allow only suitable soil formation depth when calculating the absorption area.

(G) The minimum width of each trench excavation shall be 24 inches.

(H) The minimum separation from the bottom of each deep wall trench to:

(I) the anticipated maximum ground water table shall be a minimum of 48 inches; and

(II) unsuitable soil or bedrock formations shall be a minimum of 48 inches.

(I) Drain media shall cover the coarse drain media to allow for leveling of the distribution pipe and shall extend the full width and length of the trench.

(J) The minimum depth of drain media shall be 12 inches.

(K) The minimum depth of drain media under the distribution pipe shall be 6 inches.

(L) The minimum depth of drain media over the distribution pipe shall be 2 inches.

(M) The minimum depth of cover over the barrier material shall be 6 inches.

(N) The distribution pipe shall be centered in the trench and placed the entire length of the trench.

(O) The horizontal setback distance to any property line shall be a minimum of 10 feet.

(xi) A seepage pit shall be considered as a modified deep wall trench and shall conform to the requirements applicable to deep wall trenches, except for the following:

(A) The effective absorption area of a seepage pit shall be calculated using the total pit vertical sidewall area below the distribution pipe. The bottom area and any highly restrictive or impervious strata or bedrock formations may not be considered in determining the effective sidewall absorption area.

(B) The minimum diameter of a seepage pit shall be 3 feet.

(C) Each seepage pit shall:

(I) have a minimum effective sidewall depth of 4 feet;

(II) have a maximum effective sidewall depth of 10 feet; and

(III) allow only suitable soil formation depth when calculating the absorption area.

(D) In each pit filled with coarse drain media, the perforated distribution pipe shall run across each pit. A layer of drain media shall be used for leveling the distribution pipe. The entire pit shall be completely filled with coarse drain media to at least the top of any permeable soil formation to be calculated as effective sidewall absorption area.

(E) Each hollow-lined seepage pit shall conform to the following:

(I) For each hollow-lined pit, an inlet pipe shall extend horizontally at least 1 foot into the pit.

(II) The annular space between the lining and excavation wall shall be filled with crushed rock or gravel ranging from 3/4 through 6 inches in diameter and free of fines, sand, clay or organic material. The maximum fines in the gravel shall be 2% by weight passing through a US Standard #10 mesh or 2.0 millimeter sieve.

(III) The minimum width of annular space between lining and sidewall shall be 12 inches.

(IV) The minimum thickness of reinforced perforated concrete liner shall be 2-1/2 inches.

(V) The minimum thickness of reinforced concrete top shall be 6 inches.

(VI) The minimum depth of drain media in the seepage pit bottom shall be 6 inches.

(VII) Minimum depth of cover over seepage pit top shall be 6 inches.

(VIII) A reinforced concrete top shall be provided.

(IX) When the cover over any seepage pit top exceeds 6 inches, risers shall conform to Subsection R317-4-6(7)(g) for accessibility.

(15) Alternative onsite wastewater systems include at-grade, mound, packed media, sand lined trench, and membrane bioreactor systems. A packed bed media system may be an intermittent sand filter, a recirculating sand filter, a recirculating gravel filter, a textile filter or a peat filter.

(a) An alternative onsite wastewater system shall conform to applicable requirements stated elsewhere in this rule for design, setbacks, construction and installation details, performance, repairs and abandonment shall apply unless stated differently for a given alternative system.

(i) An absorption area for each alternative onsite wastewater system shall be sized based on Section R317-4-13 Table 5 or R317-4-13 Table 6 except as specified in this section.

(ii) Each alternative onsite wastewater system shall be designed by a person certified at Level 3 in accordance with Rule R317-11.

(A) The designer shall submit details of all system components with the necessary calculations.

(B) The designer shall provide to the local health department and to the owner operation and maintenance instructions that include the minimum inspection levels in Section R317-4-13 Table 7 for the system.

(iii) When an alternative system exists on a property, notice of the existence of that system shall be recorded in the chain of title for that property.

(b) The design each alternative onsite wastewater system shall be designed according to the requirements for the specific alternative system selected.

(i) Absorption trenches and absorption beds may be used in an at-grade system. Each at-grade system shall conform to the requirements applicable to absorption trenches and absorption beds, except for the following:

(A) Horizontal setbacks in Section R317-4-13 Table 2 are measured from edge of trench sidewall, except at property lines, where the toe of the final cover shall be 5 feet or greater in separation distance to a property line.

(B) The minimum number of observation ports provided within absorption area shall be 2. The ports shall be installed to the depth of the trench or bed.

(C) The depth of each absorption excavation below natural grade shall be 0-10 inches.

(D) The minimum cover over the absorption area shall be 6 inches.

(E) The maximum slope of natural ground surface shall be 4%.

(F) The maximum side slope for above ground fill shall be four horizontal to one vertical shall be a 25% slope.

(G) Where final contours are above the natural ground surface, the cover shall extend from the center of the wastewater system at the same general top elevation for a minimum of 10 feet in all directions beyond the limits of the absorption area perimeter, before beginning the side slope.

(ii) Each mound system shall conform to the following:

(A) The design shall generally be based on the Wisconsin Mound Soil Absorption System: Siting, Design and Construction Manual, January 2000 published by the University of Wisconsin-Madison Small-Scale Waste Management Project, with the following exceptions.

(B) The minimum separation distance between the natural ground surface and the anticipated maximum ground water table shall be 12 inches.

(C) A mound system may be built over naturally existing soil types per Section R317-4-13 Table 5 or R317-4-13 Table 6 provided the minimum depth of suitable soil is:

(I) 36 inches between the natural ground surface and bedrock formations or unsuitable soils; or

(II) 24 inches above soils that have a percolation rate faster than one minute per inch.

(D) The minimum depth of sand media over natural soil shall be 12 inches.

(E) The maximum slope of natural ground surface shall be 25 %.

(F) The separation distances in Section R317-4-13 Table 2 are measured from the toe of the final cover.

(G) The effluent loading rate at the sand media to natural soil interface shall be calculated using Section R317-4-13 Table 5 or R317-4-13 Table 6.

(H) The effluent entering a mound system shall be at levels at or below the defined parameters of non-domestic effluent.

(I) The minimum thickness of aggregate media around the distribution pipes of the absorption system shall be the sum of 6 inches below the distribution pipe, the diameter of the distribution pipe and 2 inches above the distribution pipe or 10 inches, whichever is larger.

(J) The cover may not be less than 6 inches in thickness, and shall provide protection against erosion, frost, storm water infiltration and support vegetative growth and aeration of distribution cell.

(K) A minimum of three observation ports shall be located within the mound at each end and the center of the distribution cell. At least one port shall be installed at the gravel-sand interface, and one port at the sand-soil interface.

(L) Mounds shall use pressure distribution. The Utah Guidance for Performance, Application, Design, Operation and Maintenance: Pressure Distribution Systems document and Subsection R317-4-6(14)(c)(iv) shall be used for design requirements. See Subsection R317-4-14(2) Appendix B for pump and control requirements.

(iii) Each packed bed media system shall conform to the following design criteria:

(A) For a single-family dwelling the design shall be based on a minimum of 300 gallons per day for two bedrooms and 100 gallons per day for each additional bedroom.

(B) All other flow estimates shall be based on Subsection R317-4-6(4).

(C) Special design considerations shall be given for non-domestic effluent.

(D) Effluent shall be uniformly distributed over the filter media using pressure distribution.

(E) A packed bed media absorption system may be placed where the minimum separation distance between the natural ground surface and the anticipated maximum ground water table is 12 inches.

(F) A packed bed media absorption system may be built over naturally existing soil types per Section R317-4-13 Table 5 or R317-4-13 Table 6 provided the minimum depth of suitable soils:

(I) above soils that have a percolation rate faster than one minute per inch is at least 24 inches; and

(II) at least 36 inches between the natural ground surface and bedrock formations or unsuitable soils; or

(III) there is at least 18 inches between the natural ground surface and bedrock formations or unsuitable soils, determined by an evaluation of infiltration rate and hydrogeology from a professional geologist or engineer that is certified at the appropriate level to perform onsite wastewater system design and having sufficient experience in geotechnical engineering based on the detailed subsurface geology of the vicinity, the hydrogeology of the vicinity, and the cumulative hydrogeological effect of all existing and future onsite wastewater systems within the area.

(G) A non-chemical disinfection unit, capable of meeting laboratory testing parameters in Table 7.3, and a maintenance schedule consistent to Section R317-4-13 Table 7.1 and R317-4-13 Table 7.3, shall be used in excessively permeable soils.

(H) Conformance with the minimum setback distances in Section R317-4-13 Table 2, except for the following that require a minimum of 50 feet of separation:

(I) watercourses, lakes, ponds, reservoirs;

(II) non-culinary springs or wells;

(III) foundation drains, curtain drains; or

(IV) non-public culinary grouted wells, constructed as required by Title R309.

(I) The minimum required effective absorption area shall be calculated using Section R317-4-13 Table 5 or R317-4-13 Table 6 and may be reduced by 30%. The use of chambered trenches with a packed bed media system may not receive additional reductions as allowed in Subsection R317-4-6(14)(d)(v).

(J) The bottom of the absorption system shall have a vertical separation distance of at least 12 inches from the anticipated maximum ground water table.

(K) A minimum of two observation ports shall be provided within the absorption area.

(L) Drip irrigation absorption may be used for packed bed media absorption system effluent dispersal based on type of soil and drip irrigation manufacturer's recommendations.

(I) Materials shall be specifically designed and manufactured for onsite wastewater applications.

(II) Non-absorption components shall be installed per Section R317-4-6 and Section R317-4-13 Table 2.

(iv) Each intermittent sand filter system shall conform to the following:

(A) Either sand media or sand fill may be used.

(I) The minimum depth of sand media or sand fill shall be 24 inches.

(II) The effective size of the sand media or sand fill shall be 0.35-0.5 millimeters.

(III) The uniformity coefficient of the sand media or sand fill shall be less than 4.0.

(IV) The maximum fines passing through #200 sieve shall be 1%.

(B) The maximum application rate per day per square foot of media surface area shall be:

(I) 1.0 gallons for sand media; or

(II) 1.2 gallons for sand fill.

(C) The maximum dose volume through any given orifice for each dosing shall be 2 gallons.

(D) Effluent entering an intermittent sand filter shall be at levels at or below the defined parameters of non-domestic effluent.

(v) Each recirculating sand filter system shall conform to the following:

(A) The minimum depth of washed sand shall be 24 inches.

(B) The effective size of the media shall be 1.5-2.5 millimeters.

(C) The uniformity coefficient shall be less than 3.0.

(D) The maximum fines passing through a #50 sieve shall be 1%.

(E) The maximum application rate per day per square foot of media surface area shall be 5 gallons.

(vi) Each recirculating gravel filter system shall conform to the following:

(A) The minimum depth of washed gravel shall be 36 inches.

(B) The effective size of the media shall be 2.5-5.0 millimeters.

(C) The uniformity coefficient shall be less than 2.0.

(D) The maximum fines passing through a #16 sieve shall be 1%.

(E) The maximum application rate per day per square foot of media surface area shall be 15 gallons.

(vii) Each textile filter system shall conform to the following:

(A) Media shall be an approved geotextile fabric.

(B) The maximum application rate per day per square foot of media surface area shall be 30 gallons.

(viii) Each peat filter system shall conform to the following:

(A) The minimum depth of peat media shall be 24 inches.

(B) The maximum application rate per day per square foot of media surface area shall be 5 gallons.

(ix) Each sand lined trench system shall conform to the following:

(A) The minimum depth of suitable soil or saprolite between the sand media in trenches and the anticipated maximum ground water table shall be 12 inches.

(B) Each sand lined trench system may be built over naturally existing:

(I) soil types 1 through 4; or

(II) soils or saprolite with a percolation rate between 1 and 60 minutes per inch.

(C) The minimum depth of suitable soil or saprolite shall be:

(I) 36 inches between the sand media in trenches and bedrock formations or unsuitable soils; or

(II) 24 inches above soils or saprolite that have a percolation rate faster than one minute per inch.

(D) Each sand lined trench shall conform to the requirements applicable to absorption trenches except for the following:

(I) For each trench in suitable soil, the minimum required effective absorption area shall be calculated using Section R317-4-13 Table 5 or R317-4-13 Table 6.

(II) For each trench in saprolite, the minimum required effective absorption area shall be based on percolation rate using Section R317-4-13 Table 5. This rate shall be determined by conducting percolation tests. The soil shall be allowed to swell not less than 24 hours or more than 30 hours;

(III) The use of chambered trenches with a sand media system may not receive additional reductions as allowed in Subsection R317-4-6(14)(d)(v).

(IV) The maximum width of an absorption trench excavation shall be 36 inches.

(V) The entire trench sidewall shall be installed in natural ground. An at-grade system design may not be allowed.

(VI) The minimum depth of sand media shall be 24 inches.

(VII) Each sand lined trench with drain media shall have a minimum depth of 6 inches of drain media under the pressure lateral distribution pipe.

(VIII) Each sand lined trench with drain media shall have a minimum depth of 2 inches of drain media over pressure lateral distribution pipe.

(IX) The minimum depth of soil cover or saprolite over drain media shall be 6 inches.

(X) For each sand lined trench with Type A chambers. the minimum depth of soil cover or saprolite over chambers shall be 12 inches.

(XI) The minimum number of observation ports per trench shall be 1.

(E) Effluent shall be uniformly distributed over the sand media using pressure distribution. Pressure distribution design shall generally be based on the Utah Guidance for Performance, Application, Design, Operation and Maintenance: Pressure Distribution Systems document.

(x) Each membrane bioreactor system installed as part of an alternative onsite wastewater system is intended to be installed as a complete unit. The design of any the treatment tank and all accessory components, treatment pods, aerators, blowers, pumps, membranes, and control panel shall conform to manufacturer specifications specific to the daily flows and wastewater strength proposed to be treated. Each membrane bioreactor system shall conform to the following:

(A) For a single-family dwelling the design shall be based on a minimum of 300 gallons per day for two bedrooms and 100 gallons per day for each additional bedroom.

(B) All other flow estimates shall be based on Subsection R317-4-6(4).

(C) Special design considerations shall be given for non-domestic effluent.

(D) Each membrane bioreactor system installed shall meet the requirements listed in Subsection R317-4-6(7).

(E) Each septic, equalization, recirculation, pump, or other tanks used in conjunction with any membrane bioreactor system shall meet the requirements listed in Section R317-4-6.

(F) MBR tank volume shall have a liquid capacity adequate for the minimum operating volume that includes the dead space, dosing volume, and surge capacity, and shall have the emergency operation capacity of:

(I) storage capacity for the system design daily wastewater flow;

(II) at least two independent power sources with appropriate wiring installed; or

(III) other design considerations approved by the regulatory authority that do not increase public health risks if pump failure occurs.

(G) Each membrane bioreactor system shall have a minimum of two membrane filter units installed in a manner that any unit can be maintained independently of other filter membrane units.

(H) Each membrane bioreactor overflow shall discharge directly to the septic tank.

(I) Each membrane bioreactor unit shall be installed according to manufacturer's specifications.

(J) Any membrane bioreactor system constructed above ground shall be housed in an easily accessible service building that is climate controlled. The service building shall meet the appropriate permitting and setback distances required by the building authority.

(K) Each membrane bioreactor absorption system shall conform to the following:

(I) The minimum separation distance between the natural ground surface and the anticipated maximum groundwater table shall be 12 inches.

(II) An absorption system receiving effluent from a membrane bioreactor may be built over naturally existing soil types per Section R317-4-13 Table 5 or R317-4-13 Table 6 provided the minimum depth of suitable soils above soils that have a percolation rate faster than one minute per inch is 24 inches.

(III) An absorption system receiving effluent from a membrane bioreactor may be built over naturally existing soil types per Section R317-4-13 Table 5 or R317-4-13 Table 6 provided the minimum depth of suitable soils between the natural ground surface and bedrock formations or unsuitable soils is 36 inches.

(IV) An absorption system receiving effluent from a membrane bioreactor may be built over naturally existing soil types per Section R317-4-13 Table 5 or R317-4-13 Table 6 provided the minimum depth of suitable soils between the natural ground surface and bedrock formations or unsuitable soils is at least 18 inches between the natural ground surface and bedrock formations or unsuitable soils determined by an evaluation of infiltration rate and hydrogeology from a professional geologist or engineer that is certified at the appropriate level to perform onsite wastewater system design and having sufficient experience in geotechnical engineering based on the subsurface geology of the vicinity, the hydrogeology of the vicinity, and the cumulative hydrogeological effect of all existing and future onsite wastewater systems within the area.

(L) A non-chemical disinfection unit, capable of meeting laboratory testing parameters in Table 7.3, and a maintenance schedule consistent to Sections R317-4-13 Table 7.1 and R317-4-13 Table 7.3, shall be used in excessively permeable soils.

(M) Conformance with the minimum setback distances in Section R317-4-13 Table 2, except for the following that require a minimum of 50 feet of separation:

(I) watercourses, lakes, ponds, reservoirs;

(II) non-culinary springs or wells;

(III) foundation drains, curtain drains; or

(IV) non-public culinary grouted wells, constructed as required by Title R309.

(N) The minimum required effective absorption area for an absorption system receiving effluent from a membrane bioreactor system shall be calculated using Section R317-4-13 Table 5 or R317-4-13 Table 6 and may be reduced by 30%.

(O) The use of chambered trenches with any membrane bioreactor system may not receive additional reductions as allowed in Subsection R317-4-6(14)(d)(vii)(C).

(P) The bottom of the absorption system shall have a vertical separation distance of at least 12 inches from the anticipated maximum groundwater table.

(Q) A minimum of two observation ports shall be provided within the absorption area.

(R) Drip irrigation absorption may be used for membrane bioreactor absorption system effluent dispersal based on type of soil and drip irrigation manufacturer's recommendations.

(S) Materials shall be specifically designed and manufactured for onsite wastewater applications.

(T) Non-absorption components shall be installed per Sections R317-4-6 and R317-4-13 Table 2.

(U) A membrane bioreactor manufacturer shall submit NSF/ANSI Standard 40 - Residential Wastewater Treatment Systems certification for any model proposed to be approved for use in Utah. The division may approve any membrane bioreactor model as equivalent to an NSF certified model, if the manufacturer submits a written recommendation bearing the seal of a professional engineer licensed to practice in Utah who is certified as a Level 3 Onsite Professional as defined in Rule R317-11.

Utah Administrative CodeTopic - Environmental QualityTitle R317 - Water QualityRule R317-4 - Onsite Wastewater SystemsSection R317-4-6 - Design Requirements

Utah Administrative Code
Topic - Environmental Quality
Title R317 - Water Quality
Rule R317-4 - Onsite Wastewater Systems
Section R317-4-6 - Design Requirements