Gravity Sewers

PURPOSE: This rule specifies the minimum standards for the design of gravity sewers that are part of wastewater collection and treatment systems. This rule is to be used with rules 10 CSR 20-8.110 through 10 CSR 20-8.210. It does not address all aspects of design, and the design engineer may refer to other appropriate reference materials so long as these minimum standards set forth in this rule are met. PUBLISHER’S NOTE: The secretary of state has determined that the publication of the entire text of the material which is incorporated by reference as a portion of this rule would be unduly cumbersome or expensive. This material as incorporated by reference in this rule shall be maintained by the agency at its headquarters and shall be made available to the public for inspection and copying at no more than the actual cost of reproduction. This note applies only to the reference material. The entire text of the rule is printed here. (1) Applicability. Wastewater systems that utilize gravity sewers shall be designed based on criteria contained in this rule, published standards, applicable federal and state requirements, standard textbooks, current technical literature and applicable safety standards. In the event of any conflict between the above criteria, the requirement in this rule shall prevail. (A) This rule shall not apply to treatment units covered in 10 CSR 20-8.300. (B) This rule shall not apply to treatment units covered in 10 CSR 20-8.500. (2) Sanitary Sewers. Rain water from roofs, streets, and other areas and groundwater from foundation drains shall be excluded from all new sewers. (3) Details of Design and Construction. (A) Installation. Installation specifications shall contain appropriate requirements based on the criteria, standards, and requirements established by industry in its technical publications. Requirements shall be set forth in the specifications for the pipe and methods of bedding and backfilling thereof, so as not to damage the pipe or its joints, impede cleaning operations, and future tapping, nor create excessive side fill pressures and ovalation of the pipe, nor seriously impair flow capacity. 1. Slope. All sewers shall be designed and constructed to give mean velocities, when flowing full, of not less than two feet (2') per second. 2. Depth. All sewers shall either be covered with at least thirty-six inches (36") of soil, or sufficiently insulated with other material to prevent freezing and to protect them from superimposed loads. 3. Buoyancy. Buoyancy of sewers shall be considered and flotation of the pipe shall be prevented with appropriate construction where high groundwater conditions are anticipated. (B) Deflection test. No pipe shall exceed a deflection of five percent (5%) of the inside diameter. (C) Joints and Infiltration. 1. Service connections. Service connections to the sewer main shall be watertight and cannot protrude into the sewer. 2. Leakage tests. Leakage tests shall be specified for gravity sewers except polyvinyl chloride (PVC) pipe with a diameter of twenty-seven inches (27") or less. A. Water (hydrostatic) test. The leakage exfiltration or infiltration shall not exceed one hundred (100) gallons per inch of pipe diameter per mile per day for any section between manholes of the system. An exfiltration or infiltration test shall be performed with a minimum positive head of two feet (2'). The exfiltration or infiltration test shall conform to the test procedure described in ASTM C969 – 17 Standard Practice for Infiltration and Exfiltration Acceptance Testing of Installed Precast Concrete Pipe Sewer Lines, as approved and published April 1, 2017, for precast concrete pipe. This standard shall hereby be incorporated by reference into this rule, as published by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. This rule does not incorporate any subsequent amendments or additions. B. Air test. The air test shall conform to the test procedure described in ASTM C1103 – 14 Standard Practice for Joint Acceptance Testing of Installed Precast Concrete Pipe Sewer Lines, as approved and published November 1, 2014, for concrete pipe twenty-seven inches (27") or greater in diameter, and ASTM F1417 – 11a(2015) Standard Practice for Installation Acceptance of Plastic Non-pressure Sewer Lines Using Low-Pressure Air, as approved and published August 1, 2015, for plastic, composite, and ductile iron pipe. These standards shall hereby be incorporated by reference into this rule, as published by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. This rule does not incorporate any subsequent amendments or additions. (D) Bore or Tunnel. Where casing pipe is utilized it shall be constructed of steel with welded joints conforming to AWWA C200-17 Steel Water Pipe, 6 In. (150 mm) and Larger, as approved and published August 1, 2017, or ductile iron pipe with mechanical joints. This standard shall hereby be incorporated by reference into this rule, as published by American Water Works Association (AWWA), 6666 West Quincy Avenue, Denver, CO 80235-3098. This rule does not incorporate any subsequent amendments or additions. (4) Manholes. (A) Location. Manholes shall be installed— 1. At the end of each line; 2. At all changes in grade, size, or alignment; 3. At all sewer pipe intersections; and 4. At distances appropriate to allow for sufficient cleaning and maintenance of sewer lines. (B) Drop Type. 1. A drop pipe shall be provided for a sewer entering a manhole at an elevation of twenty-four inches (24") or more above the manhole invert. 2. When using precast manholes, drop connections must not enter the manhole at a joint. (C) Diameter. The minimum diameter of manholes shall be forty-two inches (42") on eight-inch (8") diameter gravity sewer lines and forty-eight inches (48") on all sewer lines larger than eight inches (8") in diameter. A minimum access diameter of twenty-two inches (22") (56 cm) shall be provided. Cleanouts shall be a minimum of eight inches (8") for pipes eight inches (8") in diameter or larger and equal to the diameter for pipes less than eight inches (8"). (D) Bench. No sewer, service connection, or drop manhole pipe shall discharge onto the surface of the bench. (E) Watertightness. Manholes shall be watertight, constructed, and installed in accordance with the manufacturer’s recommendations and procedures. (F) Inspection and Testing. 1. Vacuum testing, if specified for concrete sewer manholes, shall conform to the test procedures in ASTM C1244 – 11(2017) Standard Test Method for Concrete Sewer Manholes by the Negative Air Pressure (Vacuum) Test Prior to Backfill, as approved and published April 1, 2017, or the manufacturer’s recommendation. This standard shall hereby be incorporated by reference into this rule, as published by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. This rule does not incorporate any subsequent amendments or additions. 2. Exfiltration testing, if specified for concrete sewer manholes, shall conform to the test procedures in ASTM C969 – 17 Standard Practice for Infiltration and Exfiltration Acceptance Testing of Installed Precast Concrete Pipe Sewer Lines, as approved and published April 1, 2017. This standard shall hereby be incorporated by reference into this rule, as published by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. This rule does not incorporate any subsequent amendments or additions. (5) Protection of Water Supplies. (A) Cross Connections. There shall be no physical connections between a public or private potable water supply system and a sewer or appurtenance that would permit the passage of any wastewater or polluted water into the potable supply. (B) Relation to Water Works Structures. Sewers shall be laid at least fifty feet (50') in a horizontal direction from any existing or proposed public water supply well or other water supply sources or structures. Sewers must also comply with 10 CSR 23-3.010. AUTHORITY: section 644.026, RSMo 2016.* Original rule filed Aug. 10, 1978, effective March 11, 1979. Amended: Filed May 17, 1994, effective Dec. 30, 1994. Amended: Filed June 28, 2011, effective Feb. 29, 2012. Amended: Filed June 15, 2018, effective Feb. 28, 2019. *Original authority: 644.026, RSMo 1972, amended 1973, 1987, 1993, 1995.