Section 58.01.16.430 - FACILITY AND DESIGN STANDARDS FOR MUNICIPAL WASTEWATER TREATMENT OR DISPOSAL FACILITIES - DESIGN AND CONSTRUCTION OF WASTEWATER PIPELINES01.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.02.Details of Design and Construction.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.b. Depth. Wastewater pipelines shall be installed sufficiently deep or specifically designed to prevent freezing and to protect the facilities from surface loading.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.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. 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.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. e. Materials. 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.ii. Couplings complying with applicable standard specifications shall be used for joining dissimilar materials.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.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.g. Joints and Infiltration.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.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.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.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.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.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. 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.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.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.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.v. Siltation and Erosion. Construction methods that will minimize siltation and erosion shall be employed.l. Aerial Crossings. Support shall be provided for all joints in pipes utilized for aerial crossings. Restrained joints or structural casings are required.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.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.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.i. Parallel installation requirements.(1) Non-potable mains in relation to potable mains: (a) Greater than ten (10) feet separation: no additional requirements based on separation distance.(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.(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.(d) Non-potable mains are prohibited from being located in the same trench as potable mains.(e) Pressure sewage mains shall be no closer horizontally than ten (10) feet from potable mains.(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. (a) Greater than six (6) feet separation: no additional requirements based on separation distances.(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.(c) New potable services are prohibited from being located in the same trench as non-potable mains or non-potable services.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. (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.(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) Less than eighteen (18) inches vertical separation:(a) Non-potable pipeline joint to be as far as possible from the potable water pipeline; and either(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(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.(d) If the potable pipeline is below non-potable pipeline, the non-potable pipeline must also be supported through the crossing to prevent settling.(4) Pressure sewage mains shall be no closer vertically than eighteen (18) inches from potable mains.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.Idaho Admin. Code r. 58.01.16.430