Sanitary sewers are conduits that carry liquid and water-carried wastes from homes, commercial facilities, industrial plants and institutions to a treatment plant for the express purpose of protecting our environment, safeguarding health, and improving our comforts and quality of life.

Concrete pipe is the most widely used and accepted permanent product of all sanitary sewer materials. It makes up the greater portion of the sanitary sewer system in most major cities in the United States. Sanitary sewers require that pipe meet infiltration limits, meet the strength conditions of any depth of backfill and superimposed load, and provide resistance to the effects of sewage.

Recommended Standard Specification

1. Scope

1.1 – This specification covers reinforced concrete pipe intended to be used for the conveyance of waste water.

2. Referenced Documents

2.1 ASTM Standards:

C 76     Reinforced Concrete Culvert, Storm Drain, and Sewer Pipe
C 361   Reinforced Concrete Low-Head Pressure Pipe
C 443   Joints for Circular Concrete Sewer and Culvert Pipe, Using Rubber Gaskets
C 655   Reinforced Concrete D-Load Culvert, Storm Drain, and Sewer Pipe
C 822   Definitions of Concrete Pipe and Related Products
C 969   Infiltration and Exfiltration Acceptance Testing
C 1103 Joint Acceptance Testing of Installed Pre-cast Concrete Pipe Sewer Lines

3. Terminology

3.1 Definitions – For definitions of terms relating to concrete pipe, see Definitions C 822.

4. Materials

4.1   Reinforced Concrete Pipe – Reinforced concrete pipe shall be manufactured in accordance with ASTM C 76 or ASTM C 655. The manufacturer of the reinforced concrete pipe shall be on the Illinois Department of Transportation’s “List of Certified Plants.”
4.2   Pipe Class – The class of pipe shall be as shown on the plans.
4.3   Lift Holes – Lift holes shall not be permitted.
4.4   Joints – Joints shall conform to ASTM C 443 or C 361.
4.5   Gaskets – The gaskets shall be installed in accordance with the manufacturer’s recommendations. Prior to commencing installation, the contractor shall submit to the engineer:

4.5.1 – Manufacturer’s literature on the type of gasket to be used.
4.5.2 – Manufacturer’s literature on the type of lubricant to be used.
4.5.3 – Manufacturer’s recommended installation procedures, including equalization techniques.

4.6 Fittings – Fittings shall conform to the strength and water tightness requirements placed upon mainline pipe.

5. Excavation

5.1 Trench Depth – The trench shall be excavated to a firm foundation at least 4 inches below the bottom of the pipe so that the flow line of the finished sewer will be at the depth and grade specified by the engineer.

5.2 Trench Width – For trench depths of less than 5 ft. and when sheeting or shoring is not required, the trench shall be excavated 18 inches wider than the external diameter of the pipe. For trench depths of 5 ft. or more and when sheeting or shoring is required, the trench width shall be 3 ft. wider than the external diameter of the pipe.

6. Bedding

6.1 – Bedding material (pea gravel, crushed stone or washed gravel with at least 95% passing the 1″ sieve) shall be placed at least 4″ thick on the bottom of the trench. If any unyielding foundation is encountered, the minimum thickness shall be increased to 8 inches.

7. Installation

7.1 Handling – The contractor shall handle the pipe with care and avoid chipping or cracking the pipe.

7.2 Laying Pipe – The contractor shall keep the trench free from water during installation. The laying of pipe shall proceed upgrade, with spigot or tongue ends pointing in the direction of flow. The ends of the pipe shall be carefully cleaned before they are lowered into the trench. Each pipe shall be carefully aligned horizontally and vertically with the previous pipe and the joint pulled home. Care shall be taken to assure the gasket remains in its intended position.

8. Backfilling

8.1 Haunch – As soon as possible the entire width of the trench shall be backfilled with pea gravel, crushed stone or washed gravel (with at least 95% passing the 1″ sieve) to the pipe springline. Special care shall be taken to completely fill the space under the pipe. A flowable backfill mixture, described as controlled low strength material (CLSM), may be used.

8.2 Backfill – The remainder of the trench shall be backfilled to the natural grade or finished surface. This material may consist of material excavated from the trench. Care shall be taken to avoid disturbing the pipe.

8.3 Special Considerations – In areas where the trench will be under pavements, curbs, shoulders, sidewalks or other structures, granular material will be used to fill the entire trench. The granular material will be placed and compacted to the satisfaction of the engineer. A flowable CLSM may be used when high relative densities are desired.

9. Acceptance Testing

9.1 Types of Testing – Testing for acceptance of reinforced concrete pipe shall be conducted by one of the following methods:

9.1.1 – Water exfiltration, ASTM C 969
9.1.2 – Water infiltration, ASTM C 969
9.1.3 – Joint testing, ASTM C 1103

9.2 Test Sections – Unless otherwise specified or directed by the engineer, the first 1200 feet (or the entire length if the project is less than 1200 feet) shall be tested before additional excavation is permitted. If the initial section does not pass, it shall be repaired and retested until a satisfactory result is obtained. Excavation shall not proceed beyond the first 1200-foot section until satisfactory results are obtained.

In the event the first 1200-foot section did not pass the test on the first trial, the next section of sanitary sewer approximately 1200 feet long shall also be tested, repaired if necessary, and restored until a satisfactory result is obtained. Additional excavation shall not be started until this section has passed.

When favorable test results are obtained on the first trial for a full 1200-foot section, the engineer may designate additional sections for testing. The engineer reserves the right to select the location and lengths of additional test sections. All testing will be performed within 30 days of backfilling.

9.3 Water Exfiltration – The test shall be conducted in accordance with ASTM C 969.
9.4 Water Infiltration – The test shall be conducted in accordance with ASTM C 969.
9.5 Joint Acceptance Testing – The test shall be conducted in accordance with ASTM C 1103

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