Texas Administrative Code › Title 30 - ENVIRONMENTAL QUALITY › Part 1 - TEXAS COMMISSION ON ENVIRONMENTAL QUALITY › Chapter 317 - DESIGN CRITERIA PRIOR TO 2008 › Section 317.2 - Sewage Collection System

Current through Reg. 49, No. 28; July 12, 2024
(a)
				General requirements.
(1) Design. Sewer lines
				shall be designed for the estimated future population to be served, plus
				adequate allowance for institutional and commercial flows. The collection
				system design shall provide a minimum structural life cycle of 50 years. The
				collection system design shall provide for the minimization of anaerobic
				conditions. Design procedures for the minimization of anaerobic conditions
				outlined in the United States Environmental Protection Agency (EPA) Design
				Manual for Odor and Corrosion Control in Sanitary Sewerage Systems and
				Treatment Plants (EPA/625/1-85/018), American Society of Continuing Education
				(ASCE) Manual of Engineering Practice Number 69 (MEP-69), or other appropriate
				references, should be followed. The owner of the collection system shall
				provide inspection under the direction of a Texas registered professional
				engineer during construction and testing phases of the project. All collection
				systems to be located over the recharge zone of the Edwards Aquifer shall be
				designed and installed in accordance with Chapter 213 of this title (relating
				to Edwards Aquifer) in addition to these rules.
(2) Pipe selection. The choice of sewer pipe
				shall be based on the chemical characteristics of the water delivered by public
				and private water suppliers, the character of industrial wastes, the
				possibilities of septicity, the exclusion of inflow and infiltration, the
				external forces, internal pressures, abrasion, and corrosion resistance. For
				all installations, if a pipe as a whole or an integral structural component of
				the pipe will deteriorate when subjected to corrosive internal conditions, a
				corrosive resistant coating or liner acceptable to the commission shall be
				installed at the pipe manufacturing facility unless the final engineering
				design report, including calculations and data, submitted by the engineer
				demonstrates that the design and operational characteristics of the system will
				maintain the structural integrity of the system during the minimum life cycle.
				The sewer pipe to be used shall be identified in the plans and technical
				specifications 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, etc.) and installation (bedding, backfill, etc.).
(A) Flexible pipe. The engineer shall submit
				an engineering report that includes the method of defining the modulus of soil
				reaction, (E'), for the bedding material, (E'b), and the
				natural soil (E'n), or other specific information to
				quantify the effect of the in-situ material on the effective modulus,
				(E'e). The report shall also include design calculations
				for E'e, prism load, live loads, long-term deflection,
				strain, bending strain, buckling, and wall crushing. The design calculations
				shall include all information pertinent to the determination of an adequate
				design including, but not limited to: pipe diameter and material with reference
				to appropriate standards, modulus of elasticity, tensile strength, pipe
				stiffness or ring stiffness constant converted to pipe stiffness as described
				below, Leonhardt's zeta factor or E'e from another
				acceptable method, the conversion factor used to obtain vertical deflection
				when using the Modified Iowa Equation, trench width, depth of cover, water
				table elevation, etc. Pipe stiffness shall be related to Ring Stiffness
				Constant (RSC), when necessary, by the following equation:
Attached
				  Graphic
(B)
				Rigid pipe. The engineer shall submit an engineering report that includes the
				trench width, water table, and depth of cover, etc. For rigid conduits the
				minimum strengths for the given class shall be noted in the appropriate
				standard for the pipe material. For the purpose of this section, rigid pipe is
				defined as concrete, vitrified clay, or ductile iron pipe.
(C) Other pipe materials may be considered on
				a case-by-case basis by the executive director. The design and installation of
				such materials shall generally follow the guidelines for flexible or rigid pipe
				with appropriate exceptions.
(3) Jointing material. The materials used and
				methods to be applied in making joints shall be included in the technical
				specifications. Materials used for sewer joints shall have a satisfactory
				record of preventing infiltration and root entrance. Rubber gaskets, polyvinyl
				chloride (PVC) compression joints, high compression polyurethane, welded or
				other types of factory made joints are required.
(4) Testing of installed pipe. An
				infiltration, exfiltration, or low-pressure air test shall be specified. Copies
				of all test results shall be made available to the executive director upon
				request. Tests shall conform to the following requirements.
(A) Infiltration or exfiltration tests. The
				total exfiltration, as determined by a hydrostatic head test, shall not exceed
				50 gallons per inch diameter per mile of pipe per 24 hours at a minimum test
				head of two feet above the crown of the pipe at the upstream manhole. When
				pipes are installed below the groundwater level an infiltration test shall be
				used in lieu of the exfiltration test. The total infiltration, as determined by
				a hydrostatic head test, shall not exceed 50 gallons per inch diameter per mile
				of pipe per 24 hours at a minimum test head of two feet above the crown of the
				pipe at the upstream manhole, or at least two feet above existing groundwater
				level, whichever is greater. For construction within the 25-year flood plain,
				the infiltration or exfiltration shall not exceed ten gallons per inch diameter
				per mile of pipe per 24 hours at the same minimum test head. If the quantity of
				infiltration or exfiltration exceeds the maximum quantity specified, remedial
				action shall be undertaken in order to reduce the infiltration or exfiltration
				to an amount within the limits specified.
(B) Low pressure air test. The procedure for
				the low pressure air test shall conform to the procedures described in ASTM
				C-828, ASTM C-924, ASTM F-1417, or other appropriate procedures, except for
				testing times. The test times shall be as outlined in this section. For
				sections of pipe less than 36-inch average inside diameter, the following
				procedure shall apply unless the pipe is to be joint tested. The pipe shall be
				pressurized to 3.5 per square inch (psi) greater than the pressure exerted by
				groundwater above the pipe. Once the pressure is stabilized, the minimum time
				allowable for the pressure to drop from 3.5 pounds per square inch gauge to 2.5
				pounds per square inch gauge shall be computed from the following equation. The
				test may be stopped if no pressure loss has occurred during the first 25% of
				the calculated testing time. If any pressure loss or leakage has occurred
				during the first 25% of the testing period, then the test shall continue for
				the entire test duration as outlined in this subparagraph or until failure.
				Lines with a 27-inch average inside diameter and larger may be air tested at
				each joint. Pipe greater than 36-inch diameter must be tested for leakage at
				each joint. If the joint test is used, a visual inspection of the joint shall
				be performed immediately after testing. The pipe is to be pressurized to 3.5
				psi greater than the pressure exerted by groundwater above the pipe. Once the
				pressure has stabilized, the minimum time allowable for the pressure to drop
				from 3.5 pounds per square inch gauge to 2.5 pounds per square inch gauge shall
				be ten seconds.
Attached
				  Graphic
(C)
				Deflection testing. Deflection tests shall be performed on all flexible pipes.
				For pipelines with inside diameters less than 27 inches, a rigid mandrel shall
				be used to measure deflection. For pipelines with an inside diameter 27 inches
				and greater, a method approved by the executive director shall be used to test
				for vertical deflections. Other methods shall provide a precision of plus or
				minus two-tenths of 1.0% (0.2%) deflection. The test shall be conducted after
				the final backfill has been in place at least 30 days. No pipe shall exceed a
				deflection of 5.0%. If a pipe should fail to pass the deflection test, the
				problem shall be corrected and a second test shall be conducted after the final
				backfill has been in place an additional 30 days. The tests shall be performed
				without mechanical pulling devices. The design engineer should recognize that
				this is a maximum deflection criterion for all pipes and a deflection test less
				than 5.0% may be more appropriate for specific types and sizes of pipe. Upon
				completion of construction, the design engineer or other Texas registered
				professional engineer appointed by the owner shall certify to the executive
				director that the entire installation has passed the deflection test. This
				certification may be made in conjunction with the notice of completion required
				in § 317.1(e)(1) of this title (relating to General Provisions). This
				certification shall be provided for the commission to consider the requirements
				of the approval to have been met.
(i) Mandrel
				sizing. The rigid mandrel shall have an outside diameter equal to 95% of the
				inside diameter of the pipe. The inside diameter of the pipe, for the purpose
				of determining the outside diameter of the mandrel, shall be the average
				outside diameter minus two minimum wall thicknesses for outside diameter
				controlled pipe and the average inside diameter for inside diameter controlled
				pipe, all dimensions shall be per appropriate standard. Statistical or other
				"tolerance packages" shall not be considered in mandrel sizing.
(ii) Mandrel design. The rigid mandrel shall
				be constructed of a metal or a rigid plastic material that can withstand 200
				psi without being deformed. The mandrel shall have nine or more "runners" or
				"legs" as long as the total number of legs is an odd number. The barrel section
				of the mandrel shall have a length of at least 75% of the inside diameter of
				the pipe. A proving ring shall be provided and used for each size mandrel in
				use.
(iii) Method options.
				Adjustable or flexible mandrels are prohibited. A television inspection is not
				a substitute for the deflection test. A deflectometer may be approved for use
				on a case-by-case basis. Mandrels with removable legs or runners may be
				accepted on a case-by-case basis.
(5) Bedding: trenching, bedding, and
				backfill. The width of the trench shall be minimized, but shall be ample to
				allow the pipe to be laid and jointed properly and to allow the backfill to be
				placed and compacted as needed. The trench sides shall be kept as nearly
				vertical as possible. As used herein, a trench shall be defined as that open
				cut portion of the excavation up to one foot above the pipe. The engineer shall
				specify the maximum trench width. The width of the trench shall be sufficient,
				but no greater than necessary, to ensure working room to properly and safely
				place and compact haunching materials. The space must be wider than the
				compaction equipment used in the pipe zone. A minimum clearance of four inches
				below and on each side of all pipes to the trench walls and floor shall be
				provided. Bedding Classes A, B, or C, as described in ASTM C 12 (ANSI A 106.2),
				Water Environment Federation (WEF) Manual of Practice (MOP) Number 9 or
				American Society of Civil Engineers (ASCE) MOP 37 shall be used for all rigid
				pipes, provided that the proper strength pipe is used with the specified
				bedding to support the anticipated load(s). Embedment Classes IA, IB, II, or
				III, as described in ASTM D-2321 (ANSI K65.171) shall be used for all flexible
				pipes, provided the proper strength pipe is used with the specified bedding to
				support the anticipated load, except that ASTM D-2680 may be used if the pipe
				stiffness is 200 psi or greater. Secondary backfill shall be of suitable
				material removed from excavation except where other material is specified.
				Debris, large clods or stones greater than six inches in diameter, organic
				matter, or other unstable materials shall not be used for backfill. Backfill
				shall be placed in such a manner as not to disturb the alignment of the pipe.
				Where trenching encounters extensive fracture or fault zones, caves, or
				solutional modification to the rock strata, construction shall be halted and an
				engineer shall provide direction to accommodate site conditions. Water line
				crossings shall be governed by special backfill requirements specified in
				§ 317.13 of this title (relating to Appendix E--Separation
				Distances).
(6) Site inspections.
				The executive director shall, on a random basis, perform site
				inspections.
(7) Protecting public
				water supply. Water lines and sanitary sewers shall be installed no closer to
				each other than nine feet between outside diameters. Where this cannot be
				achieved, the sanitary sewer shall be constructed in accordance with §
				317.13 of this title and §
										290.44(e)(1)
				of this title (relating to Water Distribution). Separation distances between
				sanitary sewer systems and water wells, springs, surface water sources, and
				water storage facilities shall be installed in accordance with the requirements
				of §290.41(c)(1), (d)(1), (e)(1)(C), and (e)(3)(A), and §
										290.43(b)(3)
				of this title (relating to Water Sources; and Water Storage, respectively), as
				appropriate. Where rules governing separation distance are in conflict, the
				most strict rule shall apply. No physical connection shall be made between a
				drinking water supply, public or private, and a sewer or any appurtenance. An
				air gap of a minimum of 18 inches or two pipe diameters, whichever is greater,
				shall be maintained between all potable water outlets and the maximum water
				surface elevation of sewer appurtenances. All appurtenances shall be designed
				and constructed so as to prevent any possibility of sewage entering the potable
				water system.
(8) Excluding surface
				water. Proposals for the construction of combined sewers will not be approved.
				Roof, street, or other types of drains which will permit entrance of surface
				water into the sanitary sewer system shall not be acceptable.
(9) Active geologic faults. For systems to be
				located in areas of known active geologic faults, the design engineer shall
				locate any faults within the area of the collection system and the system shall
				be laid out to minimize the number of sewers crossing faults. Where crossings
				are unavoidable, the engineering report shall specify design features to
				protect the integrity of the sewer. Consideration should be given to joints
				providing maximum deflection and to providing manholes on each side of the
				fault so that a portable pump may be used in the event of sewer failures.
				Service connections within 50 feet of an active fault should be
				avoided.
(10) Erosion control.
				Erosion or sedimentation control that minimizes the effects of runoff shall be
				provided during the construction phase of a project. This requirement will be
				reviewed on a case-by-case basis.