SECTION 4020 - STORM SEWERS

 

PART 1 - GENERAL

 

1.01 SECTION INCLUDES

 

A. Storm Sewers

 

B. Abandonment of Storm Sewers

 

1.02 DESCRIPTION OF WORK

 

A. Construct storm sewers.

 

B. Abandon storm sewers.

 

1.03 SUBMITTALS

 

Comply with Division 1 - General Provisions and Covenants.

 

1.04 SUBSTITUTIONS

 

Comply with Division 1 - General Provisions and Covenants.

 

1.05 DELIVERY, STORAGE, AND HANDLING

 

Comply with Division 1 - General Provisions and Covenants.

 

1.06 SCHEDULING AND CONFLICTS

 

Comply with Division 1 - General Provisions and Covenants.

 

1.07 SPECIAL REQUIREMENTS

 

None.

 

1.08 MEASUREMENT AND PAYMENT

 

A. Storm Sewer:

 

1. Trenched:

a. Measurement: Each type and size of pipe installed in a trench will be measured in linear feet along the centerline of the pipe from center of intake or manhole to center of intake or manhole. Where the end of the pipe discharges to a ditch or waterway, measurement will be to the end of the pipe, exclusive of aprons. Lengths of elbows and tees will be included in the length of pipe measured.

b. Payment: Payment will be made at the unit price per linear foot for each type and size of pipe.

c. Includes: Unit price includes, but is not limited to, trench excavation, dewatering, furnishing bedding material, placing bedding and backfill material, joint wrapping, wyes and other fittings, pipe joints, pipe connections, testing, and inspection.

 

2. Trenchless:

a. Measurement: Each type and size of pipe installed by trenchless methods will be measured in linear feet along the centerline of the pipe.

b. Payment: Payment will be made at the unit price per linear foot for each type and size of pipe.

c. Includes: Unit price includes, but is not limited to, furnishing and installing pipe; trenchless installation materials and equipment; pit excavation, dewatering, and placing backfill material; pipe connections; testing; and inspection.

 

B. Storm Sewer with Casing Pipe:

 

1. Trenched:

a. Measurement: Each type and size of pipe installed with a casing pipe in a trench will be measured in linear feet along the centerline of the casing pipe from end of casing to end of casing.

b. Payment: Payment will be made at the unit price per linear foot for each type and size of pipe.

c. Includes: Unit price includes, but is not limited to, furnishing and installing both carrier pipe and casing pipe, trench excavation, dewatering, furnishing bedding material, placing bedding and backfill material, furnishing and installing annular space fill material, casing spacers, pipe connections, testing, and inspection.

 

2. Trenchless:

a. Measurement: Each type and size of pipe installed by trenchless methods with a casing pipe will be measured in linear feet along the centerline of the casing pipe from end of casing to end of casing.

b. Payment: Payment will be made at the unit price per linear foot for each type and size of carrier pipe.

c. Includes: Unit price includes, but is not limited to, furnishing and installing both carrier pipe and casing pipe; trenchless installation materials and equipment; pit excavation, dewatering, and placing backfill material; casing spacers; furnishing and installing annular space fill material; pipe connections; testing; and inspection.

 

C. Removal of Storm Sewer:

 

1. Measurement: Each type and size of pipe removed will be measured in linear feet from end to end.

 

2. Payment: Payment will be made at the unit price per linear foot for each type and size of pipe removed.

 

3. Includes: Unit price includes, but is not limited to, removal, disposal, and capping (if specified) of pipe.

 

D. Connection to Existing Manhole or Intake: Connections to existing manhole or intake will be measured and paid according to Section 6010, 1.08.

 

E. Storm Sewer Abandonment:

 

1. Plug: Plugging storm sewers is incidental to other work and will not be paid for separately.

 

2. Fill and Plug:

a. Measurement: Each size of pipe filled and plugged will be measured in linear feet from end of pipe to end of pipe.

b. Payment: Payment will be at the unit price per linear foot for each size of pipe filled and plugged.

 

PART 2 - PRODUCTS

 

2.01 STORM SEWERS

 

A. Reinforced Concrete Pipe (RCP):

 

1. Comply with ASTM C 76.

 

2. Minimum Class III, Wall B (Iowa DOT Class 2000D).

 

3. Use tongue and groove joints with cold applied bituminous or rubber rope gasket jointing materials, unless otherwise specified. If specified, use rubber O-ring or profile gasket complying with ASTM C 443.

 

4. If specified, wrap exterior of each joint with engineering fabric.

 

B. Reinforced Concrete Arch Pipe (RCAP):

 

1. Comply with ASTM C 506.

 

2. Minimum Class A-III (Iowa DOT Class 2000D).

 

3. Use tongue and groove joints with cold applied bituminous or rubber rope gasket jointing materials, unless otherwise specified.

 

4. If specified, wrap exterior of each joint with engineering fabric.

 

C. Reinforced Concrete Elliptical Pipe (RCEP):

 

1. Comply with ASTM C 507.

 

2. Minimum Class HE III (Iowa DOT Class 2000D) or Class VE III (Iowa DOT Class 2000D).

 

3. Use tongue and groove joints with cold applied bituminous or rubber rope gasket jointing materials, unless otherwise specified.

 

4. If specified, wrap exterior of each joint with engineering fabric.

 

D. Reinforced Concrete Low Head Pressure Pipe (RCPP):

 

1. Comply with ASTM C 361; minimum Class C 25.

 

2. Use tongue and groove joints. Comply with ASTM C 361 for rubber O-rings or profile gaskets.

 

E. Polyvinyl Chloride Pipe (PVC):

 

1. Use pipe complying with the following:

a. Types of PVC pipes:

1) Corrugated exterior, smooth interior, ASTM F 949.

2) Solid wall, ASTM D 3034 or ASTM F 679.

3) Closed profile, ASTM F 1803.

4) Composite, ASTM D 2680.

b. PVC plastic meeting ASTM D 1784, Cell Classification 12454. Do not exceed 10 parts by weight per 100 of PVC resin in the compound for additives and fillers, including but not limited to stabilizers, antioxidants, lubricants, and colorants.

c. Minimum pipe stiffness of 46 psi.

d. Integral bell and spigot joints with elastomeric seals according to ASTM D 3212 and ASTM F 477.

 

2. Do not use in the right-of-way. Use only outside the right-of-way in public utility easement areas where no utilities exist or are proposed (running parallel or crossing) or where the trench for the PVC pipe will not be disturbed, and where the Engineer allows.

 

F. High Density Polyethylene Pipe (HDPE):

 

1. Use pipe complying with the following:

a. AASHTO M 294, Type S corrugated exterior and smooth interior.

b. ASTM D 3350 minimum resin Cell Classification 335420 C.

c. Minimum pipe stiffness at 5% deflection according to ASTM D 2412.

d. Integral bell and spigot joints with elastomeric seals complying with ASTM F 477.

e. Maximum 5% deflection of the average inside diameter by testing after installation according to Section 4060, 3.05.

 

2. Do not use in the right-of-way. Use only outside the right-of-way in public utility easement areas where no utilities exist or are proposed (running parallel or crossing) or where the trench for the HDPE pipe will not be disturbed, and where the Engineer allows.

 

G. Corrugated Metal Pipe (CMP):

 

1. Use pipe complying with the following:

a. AASHTO M 36, Type I.

b. Zinc coating complying with AASHTO M 218.

c. Corrugated steel circular section with annular or helical corrugations.

d. Gage of pipe according to Iowa DOT Standard Road Plan RF-32 or as specified in the contract documents.

e. Coupling bands with annular or helical corrugations to match pipe ends.

 

2. Do not use in the right-of-way. Use only outside the right-of-way in public utility easement areas where no utilities exist or are proposed (running parallel or crossing) or where the trench for the CMP will not be disturbed, and where the Engineer allows.

 

H. Spiral Rib Pipe:

 

1. Use pipe complying with the following:

a. ASTM A 760 Type 1R.

b. Corrugation profile of 3/4 inch by 3/4 inch by 7 1/2 inches.

c. Type 2 aluminized steel complying with ASTM A 929.

d. Minimum thickness of 0.064 inch. Use gage of pipe according to manufacturer's requirements or as specified in the contract documents.

e. Coupling bands complying with manufacturer's recommendations.

 

2. Do not use in the right-of-way. Use only outside the right-of-way in public utility easement areas where no utilities exist or are proposed (running parallel or crossing) or where the trench for the spiral rib pipe will not be disturbed, and where the Engineer allows.

 

I. Coated Corrugated Metal Pipe:

 

1. Use in corrosive soil or effluent conditions, or where specified in the contract documents or required by the Engineer.

 

2. Comply with AASHTO M 274. Use gage of pipe according to Iowa DOT Standard Road Plan RF-32 or as specified in the contract documents.

 

3. Do not use in the right-of-way. Use only outside the right-of-way in public utility easement areas where no utilities exist or are proposed (running parallel or crossing) or where the trench for the coated CMP will not be disturbed, and where the Engineer allows.

 

J. Corrugated Metal Arch Pipe (CMAP):

 

1. Use pipe complying with the following:

a. AASHTO M 36, Type II.

b. Zinc coating complying with AASHTO M 218.

c. Corrugated steel Type I pipe reformed into a pipe-arch having an approximately flat bottom.

d. Coupling bands with annular corrugations or helical corrugations to match pipe ends.

e. Gage of pipe according to Iowa DOT Standard Road Plan RF-32.

 

2. Do not use in the right-of-way. Use only outside the right-of-way in public utility easement areas where no utilities exist or are proposed (running parallel or crossing) or where the trench for the CMAP will not be disturbed, and where the Engineer allows.

 

K. Spiral Rib Arch Pipe:

 

1. Use pipe complying with the following:

a. ASTM A 760 Type IIR.

b. Corrugation profile of 3/4 inch by 3/4 inch by 7 1/2 inch.

c. Type 2 aluminized steel complying with ASTM A 929.

d. Minimum thickness of 0.064 inch. Use gage of pipe complying with manufacturer's requirements or as specified in the contract documents.

e. Coupling bands complying with the manufacturer's recommendations.

 

2. Do not use in the right-of-way. Use only outside the right-of-way in public utility easement areas where no utilities exist or are proposed (running parallel or crossing) or where the trench for the spiral rib arch pipe will not be disturbed, and where the Engineer allows.

 

L. Jointing Material for Concrete Pipe:

 

1. Bituminous Jointing Material: Use a cold-applied mastic sewer joint sealing compound recommended by the manufacturer for the intended use and approved by the Engineer. Comply with AASHTO M 198.

 

2. Rubber Rope Gasket Jointing Material: Comply with ASTM C 990.

 

3. Rubber O-ring or Profile Gasket: Comply with ASTM C 443 (for RCP) or ASTM C 361 (for RCPP).

 

M. Bituminous Joint Primer: Material intended for use in priming concrete joints. Comply with the requirements of ASTM D 41.

 

N. Engineering Fabric: Comply with Iowa DOT Article 4196.01.

 

O. Non-Shrink Grout: Comply with Iowa DOT Materials I.M. 491.13.

 

2.02 CASING PIPE

 

Comply with Section 3020, 2.02 for casing pipe requirements.

 

PART 3 - EXECUTION

 

3.01 EXAMINATION

 

A. Verify measurements at site; make necessary field measurements to accurately determine pipe makeup lengths or closures.

 

B. Examine site conditions to ensure construction operations do not pose hazards to adjacent structures or facilities.

 

3.02 PIPE INSTALLATION

 

A. General:

 

1. Clean pipe interior and joints prior to lowering into trench. Keep pipe clean during construction.

 

2. Begin at the lowest point in the line. Lay groove or bell end pointing upstream unless otherwise specified.

 

3. Place pipe with lifting holes at the top of the pipe and fill lift hole with non-shrink grout or manufactured plugs.

 

4. Assemble joints as specified by the pipe manufacturer. When specified, wrap exterior of storm sewer pipe joints with engineering fabric.

 

5. Use a saw to cut ends of pipe flush with inside wall of manholes, intakes, and structures. Do not use hammer or other means to break pipe.

 

6. Provide manholes and intakes as specified in the contract documents.

 

7. Use watertight stopper, plug, or other approved means to protect the exposed upstream ends of the pipe and prevent soil sediment from entering the storm sewer system.

 

B. Trenched:

 

1. Excavate trench and provide pipe bedding and backfill material as specified in Section 3010. If RCEP is used, provide pipe bedding as specified in the contract documents.

 

2. Prepare trench bottom to design line and grade so that only minor movement of the pipe is necessary after installation.

 

3. Lay pipe to design line and grade. Set field grades to invert of pipe.

 

4. Provide uniform bearing for full pipe barrel length. Excavate bell holes as necessary for uniform support of pipe barrel on bedding material.

 

5. Do not lay pipe in water or on saturated soil or bedding, or allow water to rise in trench around pipe prior to placing backfill material.

 

6. Do not disturb installed pipe and bedding when using movable trench boxes and shields. Block or anchor pipe as necessary to prevent joint displacement.

 

C. Trenchless: Comply with Section 3020.

 

3.03 STORM SEWER INSTALLED WITHIN A CASING PIPE

 

Comply with Section 3020, 3.04 for installation of storm sewer within casing pipe.

 

3.04 PIPE JOINTING

 

A. General:

 

1. Clean joint surfaces to remove soil or foreign material prior to jointing pipe.

 

2. Assemble joints according to pipe manufacturers recommendations. Use equipment that does not apply damaging forces to pipe joints.

 

B. Reinforced Concrete Pipe (RCP), Reinforced Concrete Arch Pipe (RCAP), and Reinforced Concrete Elliptical Pipe (RCEP):

 

1. Use cold applied bituminous or rubber rope gasket jointing materials unless otherwise specified.

a. Apply joint material to entire tongue, or to top half of tongue and bottom half of groove, in sufficient quantity to fill the joint. Close the joint between pipes.

b. Fill remaining voids in the joint, both inside and outside of pipe, with joint material. Smooth the joint material on the inside of pipes 24 inches and larger.

 

2. If a rubber O-ring or profile gasket is specified for RCP, coat the rubber gasket and joint with soap-based lubricant immediately prior to closing the joint.

 

3. If wrapped pipe joint is specified, comply with Figure 4020.211. Secure engineering fabric in place to prevent displacement while placing backfill material.

 

4. Place pipe such that joint openings on the outside or inside of the pipe do not exceed 1/8 inch at the bottom and 5/8 inch at the top.

 

C. Reinforced Concrete Low Head Pressure Pipe (RCPP); Polyvinyl Chloride Pipe (PVC) and Corrugated PVC Pipe; and High Density Polyethylene Pipe (HDPE): Coat gasket and joint with soap-based lubricant immediately prior to closing the joint.

 

D. Corrugated Metal Pipe (CMP) and Corrugated Metal Arch Pipe (CMAP): Lap coupling bands to form a tightly closed joint upon installation.

 

E. Connections between Dissimilar Pipes:

 

1. Use manufactured adapters or couplings approved by the Engineer.

 

2. Where adapters or couplings are not available, the Engineer may authorize use of a concrete collar as shown in Figure 4020.211.

 

3.05 TOLERANCES

 

The following tolerances apply to utilities installed by open trench construction. For trenchless construction, comply with Section 3020.

 

A. Do not allow horizontal and vertical alignment to vary from design line and grade at any structure by more than 1% of the inside diameter of the pipe or 1/4 inch, whichever is larger.

 

B. Do not allow the horizontal alignment of the pipe to vary from design line at any point along the pipe by more than 1% of the inside diameter of the pipe.

 

C. Low spots holding water exceeding the following depths for each pipe size will be considered unacceptable and must be removed and reinstalled to proper grade.

 

Pipe Diameter

Maximum Low Spot Depth

8

1/2

10

1/2

12

3/4

15

3/4

18 and Larger

5% of Pipe Diameter*

* Measured to the nearest 1/2

 

3.06 CONFLICTS

 

A. Horizontal Separation of Gravity Sewers from Water Mains:

 

1. Separate gravity storm sewer mains from water mains by a horizontal distance of at least 10 feet unless:

         The top of a sewer main is at least 18 inches below the bottom of the water main, and

         The sewer is placed in a separate trench or in the same trench on a bench of undisturbed earth at a minimum horizontal separation of 3 feet from the water main.

 

2. When it is impossible to obtain the required horizontal clearance of 3 feet and a vertical clearance of 18 inches between sewers and water mains, the sewers must be constructed of water main materials meeting the requirements of Section 5010, 2.01. However, provide a linear separation of at least 2 feet.

 

B. Separation of Sewer Force Mains from Water Mains: Separate storm sewer force mains and water mains by a horizontal distance of at least 10 feet unless:

 

1. The force main is constructed of water main materials meeting a minimum pressure rating of 150 psi and the requirements of Section 5010, 2.01 and

 

2. The sewer force main is laid at least 4 linear feet from the water main.

 

C. Separation of Sewer and Water Main Crossovers:

 

1. Vertical separation of storm sewers crossing under any water main should be at least 18 inches when measured from the top of the sewer to the bottom of the water main. If physical conditions prohibit the separation, the sewer may be placed not closer than 6 inches below a water main or 18 inches above a water main. Maintain the maximum feasible separation distance in all cases. The sewer and water pipes must be adequately supported and have watertight joints. Use a low permeability soil for backfill material within 10 feet of the point of crossing.

 

2. Where the storm sewer crosses over or less than 18 inches below a water main, locate one full length of sewer pipe of water main material or reinforced concrete pipe (RCP) with flexible O-ring gasket joints so both joints are as far as possible from the water main.

 

3.07 STORM SEWER ABANDONMENT

 

A. Plug:

 

1. Prior to placing the sewer plug, the Engineer will verify the sewer line is not in use.

 

2. Construct sewer plug by completely filling the end of the pipe with concrete. Force concrete into the end of the pipe for a distance of 16 inches, or one-half the pipe diameter, whichever is greater.

 

B. Fill:

 

1. Prior to filling the sewer, the Engineer will verify the sewer line is not in use.

 

2. If specified in the contract documents, fill the line to be abandoned with flowable mortar or CLSM (comply with Section 3010) by gravity flow or pumping.

 

3.08 CONNECTION TO EXISTING MANHOLE OR INTAKE

 

Comply with Section 6010, 3.05.

 

3.09 CLEANING, INSPECTION, AND TESTING

 

Clean, inspect, and test according to Section 4060.

 

END OF SECTION