Idaho Administrative Code › Title IDAPA 58 - Environmental Quality, Department of › Rule 58.01.16 - WASTEWATER RULES › Section 58.01.16.430 - FACILITY AND DESIGN STANDARDS FOR MUNICIPAL WASTEWATER TREATMENT OR DISPOSAL FACILITIES - DESIGN AND CONSTRUCTION OF WASTEWATER PIPELINES

Current through August 31, 2023
01.
Design Capacity and Design
			 Flow
. In general, sewer capacities shall be designed for the estimated
			 ultimate tributary population, except in considering parts of the systems that
			 can be readily increased in capacity. (3-31-22)
02.
Details of Design and
			 Construction
. (3-31-22)
a. Minimum Pipe
			 Size. Minimum pipe size for gravity sewer mains shall be eight (8) inches in
			 diameter. Minimum pipe size for gravity sewer services shall be four (4) inches
			 in diameter. Pipe diameters larger than these minimums shall be based on
			 cleaning capability and hydraulic capacity, and shall conform with the required
			 planning documents. (3-31-22)
b.
			 Depth. Wastewater pipelines shall be installed sufficiently deep or
			 specifically designed to prevent freezing and to protect the facilities from
			 surface loading. (3-31-22)
c.
			 Buoyancy. Buoyancy of wastewater pipelines shall be considered and flotation of
			 the pipe shall be prevented with appropriate construction where high
			 groundwater conditions are anticipated. (3-31-22)
d. Slope. Gravity wastewater pipelines shall
			 be designed to have sufficient slope and velocity to "self clean" or transport
			 constituent solids to the treatment facility. Justification for these slopes
			 shall be included in the preliminary engineering report and shall be based on
			 widely used guidance documents or published friction coefficients and Manning's
			 formula. (3-31-22)
i. If the current or future
			 ownership of the system is by a city, county, quasi-municipal corporation or
			 regulated public utility and the velocities are less than self cleaning, the
			 owner shall, as a condition of the Department's approval of plans and
			 specifications, provide justification for the lower velocities and commit to,
			 at a minimum, annually service wastewater pipelines to flush, transport, or
			 remove solids from wastewater pipelines. This would include the use of cutting
			 tools for roots, vactor trucks, and any other method required to keep the
			 pipelines clean, intact and flowing. That commitment shall be in the form of a
			 letter from both the owner and the future owner entity stating said commitment,
			 and shall include a discussion of the current and future owners' capacity to do
			 said flushing. (3-31-22)
ii. If the
			 current or future ownership of the system is by a developer that is passing the
			 operation and maintenance on to a homeowner's association or other similar
			 entity, then the design shall not allow for velocities that are less than self
			 cleaning. (3-31-22)
e.
			 Materials. (3-31-22)
i. Any generally accepted
			 material for wastewater pipelines will be given consideration. The material
			 selected should be adapted to local conditions, such as: character of
			 industrial wastes, possibility of septicity, soil characteristics,
			 exceptionally heavy external loadings, abrasion, corrosion, and similar
			 problems. (3-31-22)
ii. Couplings
			 complying with applicable standard specifications shall be used for joining
			 dissimilar materials. (3-31-22)
iii. For new pipe materials for which
			 standards have not been established, the design engineer shall provide complete
			 pipe specifications and installation specifications developed on the basis of
			 criteria adequately documented and certified in writing by the pipe
			 manufacturer to be satisfactory for the specific application.
			 (3-31-22)
f. Installation.
			 Installation specifications shall contain appropriate requirements based on the
			 criteria, standards, and requirements established by industry in its technical
			 publications. Reference current edition of the Idaho Standards for Public Works
			 Construction for assistance in designing such specifications.
			 (3-31-22)
g. Joints and
			 Infiltration. (3-31-22)
i. The installation of
			 joints and the materials used shall be included in the specifications.
			 Wastewater pipeline joints shall be designed to minimize infiltration and to
			 prevent the entrance of roots throughout the life of the system. Reference
			 current edition of the Idaho Standards for Public Works Construction for
			 assistance in designing such specifications. (3-31-22)
ii. Service connections to the wastewater
			 pipeline main shall be water tight and not protrude into the wastewater
			 pipelines. If a saddle type connection is used, it shall be a device designed
			 to join with the types of pipe which are to be connected. All materials used to
			 make service connections shall be compatible with each other and with the pipe
			 materials to be joined and shall be corrosion proof.
			 (3-31-22)
h. Manholes.
			 Manholes shall be installed at the end of each line; at all changes in grade,
			 size, or alignment; at all intersections. Cleanouts may be used only for
			 special conditions and shall not be substituted for manholes nor installed at
			 the end of laterals greater than one hundred fifty (150) feet in length.
			 (3-31-22)
i. Testing. Testing shall
			 conform with Section 501.3.4
			 of the "Idaho Standards for Public Works Construction," incorporated by
			 reference into these rules at Section
			 004. (3-31-22)
j. Inverted Siphons. Inverted siphons shall
			 have not less than two (2) barrels or pipes. They shall be provided with
			 necessary appurtenances for maintenance, convenient flushing, and cleaning
			 equipment. Design shall provide sufficient head and appropriate pipe sizes to
			 secure sufficient velocities for design average flows. (3-31-22)
k. Wastewater Pipelines in Relation to
			 Surface Water Bodies. The top of all wastewater pipelines entering or crossing
			 surface water bodies shall be at a sufficient depth below the natural bottom of
			 the bed or otherwise designed to protect the wastewater pipeline. (3-31-22)
i. Wastewater pipelines located adjacent to
			 surface water bodies shall be located outside of the bed and sufficiently
			 removed therefrom to provide for future possible stream widening and to prevent
			 pollution by siltation during construction. (3-31-22)
ii. Structures. Wastewater pipeline outfalls,
			 headwalls, manholes, gate boxes, or other structures shall be designed to
			 address anticipated flood flows of the surface water bodies.
			 (3-31-22)
iii. Alignment.
			 Wastewater pipelines crossing surface water bodies should be designed to cross
			 the surface water body as nearly perpendicular to the surface water body flow
			 as possible and shall be free from change in grade. (3-31-22)
iv. Materials. Wastewater pipelines entering
			 or crossing surface water bodies shall be constructed of water transmission
			 pressure rated pipe with restrained joints conforming to Section
			 401.2.9 of the "Idaho Standards
			 for Public Works Construction," incorporated by reference into these rules at
			 Section 004, or other
			 suitable pipe with restrained joints capable of being installed to remain
			 watertight and free from changes in alignment or grade. Material used to
			 back-fill the trench shall be concrete slurry, stone, coarse aggregate, washed
			 gravel, or other materials which will not readily erode, cause siltation,
			 damage pipe during placement, or corrode the pipe. (3-31-22)
v. Siltation and Erosion. Construction
			 methods that will minimize siltation and erosion shall be employed.
			 (3-31-22)
l. Aerial
			 Crossings. Support shall be provided for all joints in pipes utilized for
			 aerial crossings. Restrained joints or structural casings are required.
			 (3-31-22)
m. Cross Connections
			 Prohibited. There shall be no physical connections between a public or private
			 potable water supply system and a wastewater pipeline, or appurtenance thereto,
			 which would permit the passage of any wastewater or polluted water into the
			 potable supply. No water pipe shall pass through or come into contact with any
			 part of a wastewater pipeline manhole. (3-31-22)
n. Protection of Water Sources, Supplies.
			 When wastewater pipelines are proposed in the vicinity of any drinking water
			 sources or supplies or other drinking water facilities, requirements of IDAPA
			 58.01.08, "Idaho Rules for Public Drinking Water Systems," shall be used to
			 confirm acceptable isolation distances. (3-31-22)
o. Non-Potable Pipelines in Relation to
			 Potable Water Pipelines. The Department will use the Memorandum of
			 Understanding with the Plumbing Bureau as guidance in determining the relative
			 responsibilities for reviewing service lines. The conditions of Subsections
			 430.02.o.i. and 430.02.o.ii.
			 shall apply to all potable services constructed or reconstructed after April
			 15, 2007 and where the Department or the QLPE is the reviewing authority.
			 (3-31-22)
i. Parallel installation
			 requirements. (3-31-22)
(1) Non-potable mains
			 in relation to potable mains: (3-31-22)
(a)
			 Greater than ten (10) feet separation: no additional requirements based on
			 separation distance. (3-31-22)
(b)
			 Ten (10) feet to six (6) feet separation: separate trenches, with potable main
			 above non-potable main, and non-potable main constructed with potable-water
			 class pipe. (3-31-22)
(c) Less than
			 six (6) feet separation: design engineer to submit data to the Department for
			 review and approval that this installation will protect public health and
			 environment and non-potable main constructed with potable-water class pipe.
			 (3-31-22)
(d) Non-potable mains are
			 prohibited from being located in the same trench as potable mains.
			 (3-31-22)
(e) Pressure sewage mains
			 shall be no closer horizontally than ten (10) feet from potable mains.
			 (3-31-22)
(2) New
			 non-potable services in relation to potable services, new non-potable services
			 in relation to potable mains, and new potable services in relation to
			 non-potable mains. (3-31-22)
(a) Greater than
			 six (6) feet separation: no additional requirements based on separation
			 distances. (3-31-22)
(b) Less than
			 six (6) feet separation: design engineer to submit data that this installation
			 will protect public health and the environment and non-potable service
			 constructed with potable water class pipe. (3-31-22)
(c) New potable services are prohibited from
			 being located in the same trench as non-potable mains or non-potable services.
			 (3-31-22)
ii.
			 Requirements for potable water mains or services crossing non-potable mains or
			 services. For the purposes of Subsection
			 430.02.o.ii., the term
			 "pipeline" applies to both mains and services. (3-31-22)
(1) Eighteen (18) inches or more vertical
			 separation with potable pipeline above non-potable pipeline: non-potable
			 pipeline joint to be as far as possible from the potable water pipeline.
			 (3-31-22)
(2) Eighteen (18) inches
			 or more vertical separation with potable water pipeline below non-potable
			 pipeline: Non-potable pipeline joint to be as far as possible from the potable
			 water pipeline, and non-potable pipeline must be supported through the crossing
			 to prevent settling. (3-31-22)
(3)
			 Less than eighteen (18) inches vertical separation: (3-31-22)
(a) Non-potable pipeline joint to be as far
			 as possible from the potable water pipeline; and either (3-31-22)
(b) Non-potable pipeline constructed with
			 potable water class pipe for a minimum of ten (10) feet either side of potable
			 pipeline with a single twenty (20) foot section of potable water class pipe
			 centered on the crossing; or (3-31-22)
(c) Sleeve non-potable or potable pipeline
			 with potable water class pipe for ten (10) feet either side of crossing. Use of
			 hydraulic cementitious materials such as concrete, controlled density fill, and
			 concrete slurry encasement is not allowed as a substitute for sleeving.
			 (3-31-22)
(d) If the potable
			 pipeline is below non-potable pipeline, the non-potable pipeline must also be
			 supported through the crossing to prevent settling.
			 (3-31-22)
(4) Pressure
			 sewage mains shall be no closer vertically than eighteen (18) inches from
			 potable mains. (3-31-22)
iii. Existing potable services in relation to
			 new non-potable mains, existing non-potable services in relation to new potable
			 mains, and existing potable services in relation to new non-potable services
			 shall meet the requirements of Subsection
			 430.02.o.ii., where
			 practical, based on cost, construction factors, and public health significance.
			 If the Department determines that there are significant health concerns with
			 these services, such as where a large existing service serves an apartment
			 building or a shopping center, then the design shall conform with Subsection
			 430.02.o.ii.
			 (3-31-22)