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1 To: From: Subject: Electronic Distribution Recipients MINNESOTA DEPARTMENT OF TRANSPORTATION Engineering Services Division Technical Memorandum No B-01 February 7, 2012 Jon M. Chiglo, P.E. Division Director, Engineering Services Use of Plastic Pipe for Storm Sewer and Culverts on Trunk Highways Expiration This Technical Memorandum supersedes B-01: Use of Plastic Pipe for Storm Sewer and Culverts on Trunk Highways, and will remain in effect until February 7, 2017 unless superseded or included in the MnDOT Drainage Manual prior to that date. Implementation The provisions contained in this Technical Memorandum are for immediate implementation on trunk highway projects. Introduction This Technical Memorandum is an update to Technical Memorandum No B-01. The Technical Memorandum is being revised in recognition of changes to AASHTO Load and Resistance Factor Design (LRFD) design and construction specifications and observations of performance issues for plastic pipe that resulted in the need to modify guidance. Purpose The purpose of this Technical Memorandum is to provide revised policy on the use of plastic pipe for storm sewer and culverts. Detailed information is given for the use of corrugated polyethylene (CP) pipe and polyvinyl chloride (PVC) pipe. Guidelines Use plastic pipe in accordance with the following guidelines if the pipe is located within MnDOT right of way. For pipe placed off of MnDOT right of way, such as a storm sewer outfall along a city street, or pipe located on property to be turned back to a local entity such as a frontage road, contact the local unit of government to determine the type(s) of pipe to include in the plan. Within the guidelines of this Technical Memorandum, use plastic pipe, which includes AASHTO Type S dual wall corrugated polyethylene (CP) and polyvinyl chloride (PVC), on all trunk highway projects as an alternative to reinforced concrete (RC) or corrugated steel (CS) pipe. When a watertight joint is specified for reinforced concrete pipe, it should be noted in the plan that the plastic pipe being provided as an alternative shall also have a watertight joint. Minimum plastic pipe installation requirements including maximum cover, minimum cover and minimum trench width are provided in the attachment titled Plastic Pipe Installation Requirements for Storm Sewer and Culverts. When culvert case treatments are specified for reinforced concrete pipe, plastic pipe shall also be installed with the same culvert case treatment. Do not use plastic pipe unless minimum cover requirements are met. Minimum cover is measured from the outside top of the pipe to the top of the road or ground surface. Minimum cover requirements are as follows: -MORE-

2 Technical Memorandum No B-01 Use of Plastic Pipe for Storm Sewer and Culverts on Trunk Highways February 7, 2012 Page 2 Minimum Cover feet (m) 1 Nominal Diameter inches (mm) Paved Roads Unpaved Roads Private Entrances Non-Roadway 2 12 (300) 3 (0.9) 2 (0.6) 1 (0.3) 1 (0.3) 15 (375) 3 (0.9) 2 (0.6) 1 (0.3) 1 (0.3) 18 (450) 3 (0.9) 2 (0.6) 1 (0.3) 1 (0.3) 24 (600) 3 (0.9) 2 (0.6) 1 (0.3) 1 (0.3) 30 (750) 3 (0.9) 2 (0.6) 2 (0.6) 1.5 (0.5) 36 (900) 3 (0.9) 2 (0.6) 2 (0.6) 1.5 (0.5) 42 (1050) 3 (0.9) 2 (0.6) 2 (0.6) 1.5 (0.5) 48 (1200) 3 (0.9) 2 (0.6) 2 (0.6) 1.5 (0.5) 1 Includes minimum of 12 compacted embedment material. 2 Topsoil and erosion control products are not included in minimum cover depth. All costs associated with using an alternative, such as differences in installation requirements including but not limited to deflection testing, dewatering, trench width, buoyancy prevention, fire mitigation, or embedment material specifications and quantities are included in the contract unit prices of the relevant pipe pay items. Plastic pipes should only be used in locations where end treatments are located beyond the design clear zone or meet safety guidelines for pipe ends so that they are not likely to be a roadside hazard or be damaged by errant vehicles leaving the roadway. Safety grates may interfere with required deflection testing and post-construction inspections. Use (CS) metal aprons for end treatments unless an alternative is specified in the plan. Plastic pipe is dependent on soil interaction for support. Adequate compaction must be attainable for the pipe to perform satisfactorily. Plastic pipe should not be used where groundwater may be encountered within the trench zone or where poor soils are encountered. Plastic pipe should not be used in locations with standing water without requirements for dewatering and in some cases buoyancy prevention. Plastic pipe is buoyant and may float. Plastic pipe requires deflection testing and post-construction inspections that cannot be completed if the pipe is submerged without dewatering. Pipes can be stabilized with anchors such as a concrete headwall or in-ground anchors; installations in these cases require a design detail in the plan. Where buoyancy potential exists and buoyancy prevention is not used, the required minimum cover will be the greater of the depths from the Minimum Cover Table and the Buoyancy Minimum Cover Requirement Table. Buoyancy Minimum Cover Requirement Nominal Diameter Inches (mm) Cover for PVC Feet (m) Cover for HDPE Feet (m) 12 (300) 1 (0.3) 1 (0.3) 15 (375) 1 (0.3) 1 (0.3) 18 (450) 1 (0.3) 1.5 (0.5) 24 (600) 1 (0.3) 1.5 (0.5) 30 (750) 1.5 (0.5) 2 (0.6) 36 (900) 2 (0.6) 2.5 (0.8) 42 (1050) 2 (0.6) 2.5 (0.8) 48 (1200) 2.5 (0.8) 3 (0.9) Plastic pipe should not be used where there is a likelihood of exposure to fire without fire mitigation. Fire mitigation alternatives include concrete slope paving, concrete headwall, and concrete aprons. Use of fire mitigation alternatives requires a design detail in the plan. -MORE-

3 Technical Memorandum No B-01 Use of Plastic Pipe for Storm Sewer and Culverts on Trunk Highways February 7, 2012 Page 3 As with all other drainage products, engineering judgment should be used in determining the suitability of using specific materials on individual projects. Plastic pipe is considered to be resistant to deterioration in corrosive soils and resistant to salts, alkalides and chlorides. When conditions warrant, additional locations beyond those identified in these guidelines may be considered; contact the State Hydraulics Engineer to discuss the options. Locations of plastic pipe installations shall be reported to the District Hydraulics Engineer. Storm Sewer The allowable diameters are (300 mm mm). In order to make it clear which pipes will have options, the allowable options shall be noted in the drainage tabulation for each reach of pipe. On the Statement of Estimated Quantities, the listed pay item will be reinforced concrete pipe. A note shall be provided on each appropriate pay item noting that plastic pipe may be used as an option. A note should be in the plan when a watertight joint is required. In the situation where some of the storm sewer pipe qualifies for the plastic pipe option and the remainder is reinforced concrete pipe, the pay item shall have a note on the estimate sheet showing how much pipe may be plastic. Plastic pipe can be used as storm sewer under pavement with no ADT restrictions. Centerline Culvert The maximum allowable diameter is 48 (1200 mm) for use under unpaved roads or when ADT is less than Centerline culverts shall have silt-tight joints unless designated as requiring watertight joints. A note should be in the plan when a watertight joint is required. In order to make it clear which pipes shall have options, the allowable options shall be noted in the drainage tabulation for each reach of pipe. On the Statement of Estimated Quantities, the listed pay item will be reinforced concrete pipe. A note shall be provided on each appropriate pay item noting that plastic pipe may be used as an option. Side Culvert The maximum allowable diameter is 48 (1200 mm) for use under entrances when ADT is less than In order to make it clear which pipes shall have options, the options should be noted in the drainage tabulation for each culvert. On the Statement of Estimated Quantities the listed pay item will be a generic pipe culvert and generic apron with a note indicating the applicable pipe options. To ensure adequate hydraulic capacity, applicable pipe options must be approved by the District Hydraulics Engineer. Questions For information on the technical contents of this memorandum, please contact Andrea Hendrickson at (651) Any questions regarding publication of this Technical Memorandum should be referred to the Design Standards Unit, DesignStandards.DOT@state.mn.us. A link to all active and historical Technical Memoranda can be found at To add, remove, or change your name on the Technical Memoranda mailing list, please visit the web page Attachments: A. Specifications for Corrugated Polyethylene Pipe Sewer B. Specifications for Polyvinyl Chloride Pipe Sewer C. Plastic Pipe Installation Requirements for Storm Sewer and Culverts -END-

4 TM B-01 Attachment A (2501) CORRUGATED POLYETHYLENE PIPE CULVERTS (2503) CORRUGATED POLYETHYLENE PIPE SEWER This work shall consist of furnishing and installing dual-wall corrugated polyethylene pipe and fittings in accordance with the plans, MnDOT Specifications, AASHTO M294, Section 12 of the AASHTO LRFD Bridge Design Specifications and the following: Before allowing vehicles or heavy construction equipment to travel over the pipe trench, maintain a minimum cover depth of material above the pipe of at least 2 feet [600 mm] and meeting the requirements of AASHTO LRFD Bridge Design Specifications, Section 30, Table A. MATERIALS AASHTO Type S corrugated polyethylene pipe and fittings shall be manufactured from high-density polyethylene (HDPE) virgin compounds. Clean reworked HDPE materials from the manufacturer s own production may be used by the manufacturer of HDPE pipe, provided that the pipe and fittings produced meet all the requirements of these special provisions, AASHTO M294 and Section 12 of the AASHTO LRFD Bridge Design Specifications. Each shipment of pipe shall be accompanied by a Certificate of Compliance, furnished by the pipe manufacturer, in accordance with MnDOT Specification Do not expose CP pipe to direct sunlight for a total time greater than 6 months after fabrication. Damaged pipe shall not be used. B. COUPLINGS Connections shall be made with bell and spigot joints. Bell and spigot joints shall use a gasket if necessary to make the joint soil-tight. At a minimum all joints will be soil-tight unless otherwise specified. When a silt-tight joint is specified, it will require a bell and spigot joint utilizing an elastomeric rubber seal (gasket) meeting ASTM F477 able to pass a laboratory pressure test of at least 2 psi (14 kpa). When a watertight joint is specified in the plans, it will be required that the joint meet the requirements of ASTM D3212 except as modified. The internal pressure test shall be performed at 10 psi (68 kpa) minimum with the pipe in straight alignment. The vacuum test is not required. The Engineer shall be provided a laboratory certification that the pipe coupler for each size of pipe meets or exceeds these requirements. The Engineer shall also be furnished shop drawings of each pipe coupler. C. DEFLECTION TESTING Evaluate pipe to determine whether the specific internal diameter of the barrel has been reduced more than 5%. Deflection testing shall be done no sooner than thirty days after installation and final fill. If the roadway surface will be paved before thirty days has passed, an additional preliminary deflection test will be required after a minimum of two feet of fill is placed and prior to the placement of pavement over the pipe; a second deflection test will still need to be completed thirty days after pipe installation. If the pipe fails the preliminary deflection test the pipe will be removed, reinstalled and retested prior to paving. Deflection testing for pipes with an inside diameter of 24 (600 mm) or less shall be performed by the Contractor using a nine-point mandrel approved by the Engineer. The diameter of the mandrel shall be 95% of the certified actual mean inner diameter of the pipe. The mandrel must be pulled through the pipe by non-mechanical means. Deflection testing of pipes with an inside diameter greater than 24 (600 mm) shall be inspected with a mandrel, or other method capable of making the deflection measurement that is approved by the Engineer. If direct measurements are allowed, locations will be selected randomly by the Engineer, but at a minimum, measurements will be taken every 10 feet (3 m) throughout the pipe length and at the pipe ends. In addition the pipe must be visually inspected and measurements taken at any location where anomalies or deflections are observed. Personnel making direct measurements must be in compliance with the confined space entry requirements. Pipe through which the mandrel does not pass or which direct measurement indicates there is more than 5% deflection will be considered unacceptable. New pipe or deformed pipe that is not damaged shall be re-laid. The relaid pipe shall be retested for deflection after five days or more. The Engineer will not accept pipe if the mandrel does not pass through it or if direct measurements indicate a deflection of more than 5 percent. Obstructions to deflection testing must be avoided or removed including dewatering of standing water sufficient to interfere with mandrel testing or safety grates installed prior to deflection testing. Include all costs associated with using an alternative, such as differences in installation requirements including but not limited to deflection testing, dewatering, trench width, buoyancy prevention, fire mitigation, or embedment material specifications and quantities are included in the contract unit prices of the relevant pipe pay items.

5 TM B-01 Attachment B (2501) POLYVINYL CHLORIDE PIPE CULVERT (2503) POLYVINYL CHLORIDE PIPE SEWER This work shall consist of furnishing and installing polyvinyl chloride (PVC) pipe and fittings in accordance with the plans, MnDOT Specifications, ASTM F794 and F949, Section 12 of the AASHTO LRFD Bridge Design Specifications and the following: Before allowing vehicles or heavy construction equipment to travel over the pipe trench, maintain a minimum cover depth of material above the pipe of at least 2 feet [600 mm] and meeting the requirements of AASHTO LRFD Bridge Design Specifications, Section 30, Table A. MATERIALS Corrugated polyvinyl chloride pipe and fittings shall be manufactured from polyvinyl chloride (PVC) compounds. Clean reworked PVC materials from the manufacturer s own production may be used by the manufacturer of PVC pipe, provided that the pipe and fittings produced meet all requirements of these special provisions, ASTM F794 and F949, and Section 12 of the AASHTO LRFD Bridge Design Specifications. Each shipment of pipe shall be accompanied by a Certificate of Compliance, furnished by the pipe manufacturer, in accordance with MnDOT Specification Damaged pipe shall not be used. B. COUPLINGS Connections shall be made with bell and spigot joints. Bell and spigot joints shall utilize a gasket if necessary to make the joint soil-tight. At a minimum all joints will be soil-tight unless otherwise specified. When a silt-tight joint is specified, it will require a bell and spigot joint utilizing an elastomeric rubber seal (gasket) meeting ASTM F477 able to pass a laboratory pressure test of at least 2 psi (14 kpa). When a water-tight joint is specified in the plans, it will be required that the joint meet the requirements of ASTM D3212 except as modified. The internal pressure test shall be performed at 10 psi (68 kpa) minimum with the pipe in straight alignment. The vacuum test is not required. The Engineer shall be provided a laboratory certification that the pipe coupler for each size of pipe meets or exceeds these requirements. The Engineer shall also be furnished shop drawings of each pipe coupler. C. DEFLECTION TESTING Evaluate pipe to determine whether the specific internal diameter of the barrel has been reduced more than 5%. Deflection testing shall be done no sooner than thirty days after installation and final fill. If the roadway surface will be paved before thirty days has passed an additional preliminary deflection test will be required after a minimum of two feet of fill is placed and prior to the placement of pavement over the pipe, a second deflection test will still need to be completed thirty days after pipe installation. If the pipe fails the preliminary deflection test the pipe will be removed and reinstalled prior to paving. Deflection testing for pipes with an inside diameter of 24 (600 mm) or less shall be performed by the Contractor using a nine-point mandrel approved by the Engineer. The diameter of the mandrel shall be 95% of the certified actual mean inner diameter of the pipe. The mandrel must be pulled through the pipe by non-mechanical means. Deflection testing of pipes with an inside diameter greater than 24 (600 mm) shall be inspected with a mandrel, or other method capable of making the deflection measurement that is approved by the Engineer. If direct measurements are allowed, locations will be selected randomly by the Engineer, but at a minimum, measurements will be taken every 10 feet (3 m) throughout the pipe length and at the pipe ends. In addition the pipe must be visually inspected and measurements taken at any location where anomalies or deflections are observed. Personnel making direct measurements must be in compliance with the confined space entry requirements. Pipe through which the mandrel does not pass or which direct measurement indicates there is more than 5% deflection will be considered unacceptable. New pipe or deformed pipe that is not damaged shall be re-laid. The re-laid pipe shall be retested for deflection after five days or more. The Engineer will not accept pipe if the mandrel does not pass through it or if direct measurements indicate a deflection of more than 5 percent. Obstructions to deflection testing must be avoided or removed including dewatering of standing water sufficient to interfere with mandrel testing or safety grates installed prior to deflection testing. Include all costs associated with using an alternative, such as differences in installation requirements including but not limited to deflection testing, dewatering, trench width, buoyancy prevention, fire mitigation, or embedment material specifications and quantities are included in the contract unit prices of the relevant pipe pay items.

6 TM B-01 Attachment C