(a) Flow Design Basis. An owner must use the requirements of this section to design a gravity collection system.
(1) A collection system must be designed to transport the peak flow from the service area, plus infiltration and inflow. The design must minimize inflow and infiltration. Flow calculations must be included in the engineering report.
(2) The flow calculations must include the details of the average flow, the flow peaking factor, and the infiltration and inflow.
(3) The flow calculations must include the flow expected in the wastewater treatment facility immediately upon completion of construction and at the end of a 50-year period following construction.
(b) Gravity Pipe Materials.
(1) An owner must identify in the engineering report the proposed gravity collection system pipe with its appropriate American Society for Testing and Materials (ASTM), American National Standards Institute (ANSI), or American Water Works Association (AWWA) standard numbers for both quality control (dimensions, tolerances, pipe stiffness, dimensional ratio, etc.) and installation (bedding, backfill, etc.).
(2) The selection of gravity collection system pipes must be based on:
(c) Joints for Gravity Pipes.
(1) The specifications for joints for gravity pipes must include the materials and methods used in making joints.
(2) Materials used for gravity pipe joints must prevent inflow, infiltration, and root entrance. A joint must:
(3) The specifications must include ASTM, AWWA, ANSI, or other appropriate national reference standards for the pipe joints.
(d) Separation Distances.
(1) Collection system pipes must be installed in trenches separate from water supply trenches.
(2) Wherever possible, a collection system pipe must be located below a water supply pipe. If a collection system pipe cannot be located below a water supply pipe, the owner must justify in the engineering report why it is not possible to locate the collection system pipe below the public water supply pipe.
(3) Wherever possible, collection system pipes and manholes must be located at least nine feet from all water supply pipes. If a collection system pipe or manhole cannot be located at least nine feet away from a water supply pipe, the owner must justify in the engineering report why it is not possible to provide at least nine feet of separation. Table C.1. in Figure: 30 TAC §217.53(d)(3) provides a reference to paragraphs in this subsection that apply if a collection system pipe or manhole cannot be located at least nine feet away from a water supply pipe.
(4) If a collection system pipe is located above a water supply pipe and runs parallel to the water supply pipe, each portion of the collection system pipe within nine feet of the water supply pipe must be encased. The casing pipe must be constructed of at least 150 per square inch (psi) pressure class pipe that:
(5) If a collection system pipe crosses above a water supply pipe, each portion of the collection system pipe within nine feet of the water supply pipe must either be encased in a casing pipe according to subparagraph (A) of this paragraph, or must be constructed using at least 150 psi pressure class pipe according to subparagraph (B) of this paragraph.
(6) If a collection system pipe is located below a water supply pipe and runs parallel to the water supply pipe, each portion of the collection system pipe within nine feet of the water supply pipe must either be constructed using at least 150 psi pressure class pipe according to subparagraph (A) of this paragraph, or must be encased in a casing pipe according to subparagraph (B) of this paragraph.
(7) If a collection system pipe crosses below a water supply pipe, each portion of the collection system pipe within nine feet of the water supply pipe must either be constructed using at least 150 psi pressure class pipe according to subparagraph (A) of this paragraph, or must be encased in cement-stabilized sand according to subparagraph (B) of this paragraph, or must be encased in a casing pipe according to subparagraph (C) of this paragraph.
(8) If a nine-foot separation distance between a manhole and a water supply pipe cannot be achieved, the manhole must either:
(e) Building Laterals and Taps. Building laterals and taps must:
(1) include a manufactured fitting that prevents infiltration and root entrance;
(2) prevent service lines from protruding into the collection system pipe; and
(3) protect the mechanical and structural integrity of a collection system.
(f) Bore or Tunnel for Crossings. The spacing of supports for carrier pipe through casings must maintain the grade, slope, and structural integrity of the pipe as required by subsection (k) of this section.
(g) Corrosion Potential of Collection System Pipes.
(1) The engineering report must include calculations or other information that demonstrate the structural integrity of a pipe during the minimum 50-year design life cycle if a pipe or an integral structural component of a pipe has potential to deteriorate when subjected to corrosive internal conditions, or if a pipe or component does not have a corrosion resistant liner or protective coating installed by the pipe manufacturer.
(2) If the corrosion analysis indicates that corrosion will reduce the functional life of the pipe to less than 50 years based on the structural analysis in subsection (k) of this section, then the pipe must have a lining or protective coating that will extend the functional life to 50 years.
(h) Odor Control. An owner shall implement odor control measures necessary to prevent a collection system from becoming a nuisance.
(i) Active Geologic Faults.
(1) An owner shall identify all active faults within the boundaries of the collection system project and minimize the number of collection system lines crossing faults.
(2) An owner shall not install a collection system service connection within 50 feet of an active fault.
(j) Capacity Requirements.
(1) An owner must ensure that a collection system's capacity is sufficient to serve the estimated future population of the area served by the project, including institutional, industrial, and commercial flows.
(2) An owner must include calculations in the engineering report that demonstrate the hydraulic capacity of a collection system, accounting for the peak flow of domestic wastewater, peak flow of wastewater from industrial sites, and maximum expected infiltration rates.
(3) An owner must ensure that the collection system has capacity to prevent a surcharge.
(4) An owner must ensure that a gravity pipe is at least 6.0 inches in diameter.
(5) Any connection between a stormwater collection system and a wastewater collection system is prohibited.
(6) An owner may use the data from an existing collection system for design purposes. In the absence of existing data, a design must use data from a system with similar characteristics, including:
(7) New collection systems. Cont'd...