4-14 Section 402. Storm Sewers
402.01. Description This work consists of constructing storm sewers of the size and class required, including excavation, bedding, and backfill. The following terms apply to this section: Type HE. An elliptical pipe placed with the major axis in the horizontal direction. Type VE. An elliptical pipe placed with the major axis in the vertical direction. 402.02. Materials Provide materials in accordance with the following sections : Granular Material Class II, III , IIIA ......................................................... 902 Aggregate 6A, 17A, 34R , 46G .............................................................. 902 Sewer Pipe ............................................................................................ 909 Sealers for Sewer Joints ....................................................................... 909 Steel Pipe (for jacking in place) ............................................................. 909 Geosynthetics ....................................................................................... 910 Concrete, Grade 3000 ........................................................................ 1004 Mortar, Type R -2 ................................................................................. 1005 Select pipe with watertight joint systems from the Qualified Products List. Storm sewers are divided into five classes, as specified in Table 402-1. If the contract specifies only the size and class of sewer, select and provide an alternative storm sewer pipe allowed in Table 402-1. For types of sewer material that are required but are not included in Table 402-1, the contract will specify the type and size of sewer material. A higher strength or greater thickness of sewer may be substituted for the minimum required sewer strength or minimum required thickness. MDOT Standard Specifications for Construction Section 402
4-15 Table 402- 1: Pipe Alternatives for Storm Sewer Classes
Type of Pipe Storm Sewer Class ( depth of c over, feet(a)) Class A Sewer (1–10)(b)(c) Class B Sewer (>10–16) Class C Sewer (>16–23) Class D Sewer (>23–33)(c) Class E Sewer (1–3)(c)(d) Reinforced concrete(e) II III IV V IV Nonreinforced concrete(f) 1 3 No No No Corrugated and spiral r ibbed al -alloy(g) Yes Yes Yes Yes No Corrugated and spiral r ibbed s teel(h) Yes Yes Yes Yes No Dual-wall polymer -precoated galvanized s teel Yes Yes Yes Yes No Smooth -lined c orrugated plastic (CPE)(i) Yes(j)(k) Yes(k)(l) No No No Corrugated polyvinyl c hloride (CPV )(m) Yes(j)(k) Yes(k)(l) No No No
a.Cover, including the pavement structure is defined as the height of fill above the top of the pipe measured to final grade.
b.Class A sewer applies when the sewer is outside the influence of proposed pavement or is beneath the influence of proposed pavement and the depth of cover is >3 feet but ≤10 feet.
c.Special design is required for depths of cover <1 foot and >33 feet.
d.Class E Sewer applies when the sewer is beneath the influence of proposed pavement and the depth of cover is ≤ 3 feet.
e.Roman numerals refer to class of reinforced concrete pipe i n accordance with AASHTO M170.
f.Arabic numerals refer to the class of nonreinforced concrete pipe in accordance with AASHTO M86.
g.Allowed for 12 - to 66 -inch spiral ribbed and 12- to 18 -inch helically corrugated 2⅔ by ½ inch aluminum alloy pipe only.
h.Allowed for 12 - to 84 -inch spiral ribbed and 12- to 18 -inch helically corrugated 2⅔ by ½ inch steel pipe only.
i.Provide CPE in accordance with AASHTO M294, Type S polyethylene pipe.
j.Allowed only for 36 -inch -diameter pipe and under for CPE and CPV pipes. At least 3 feet of cover.
k.Refer to the Class A, B and F Bury Plastic Pipe Qualified Products List for approved manufacturers and products.
l.Allowed only for 12 - to 24 -inch diameter CPE and CPV pipes.
m.CPV must conform to AASHTO M304. MDOT Standard Specifications for Construction Section 402
4-16 402.03. Construction
A.Excavation, Trench Construction, and Sewer Bedding . Perform trench construction using methods that meet the health and safety requirements specified in subsection 104.07. Excavate the trench as shown on the plans or as determined by the Engineer. Construct the trench width to at least the minimum width shown in the MDOT Standard Plan R -83 series and wide enough to provide free working space and allow com paction of the backfill around the pipe. Shape the bottom of the trench to support the pipe uniformly. Place bedding using uncompacted granular material Class IIIA to t he required elevation. Where unstable soil conditions or obstructions other than rock require excavation of the trench below the elevation detailed on the plans , undercut, backfill, and compact the trench as directed by the Engineer. Use 6A, 17A, 34R , or 46G aggregate as backfill material for undercutting due to unstable soil conditions. Use 34R aggregate for bedding material instead of granular material Class IIIA. Place the backfill up to 4 inches below the proposed bottom of the pipe. The completed w ork will be paid for as Trench Undercut and Backfill according to subsection 402.04.E. During sewer construction, maintain and protect existing live utilities. Minimize service interruptions and coordinate with the local municipality or utility company. Immediately repair or replace utilities interrupted during sewer co nstruction as directed by the Engineer.
B.Repair of Damaged Coated Surfaces. Repair coated pipe surfaces damaged during pipe transportation, handling, or installation, a t no additional cost to the Department . Complete repair of galvanized pipe surfaces in accordance with subsection 716.03.E or as approved by the Engineer . Repair other coated sewer pipe surfaces as directed by the Engineer.
C.Laying and Jointing Pipe . Lay storm sewers as shown on the plans with bells or grooves upgrade and ends fully and closely jointed. Provide a full, firm bearing along the length of each pipe section. Wrap all pipe joints with geotextile blanket. Use geotextile at least 36 inches wid e and center it on the joint. Overlap the ends of the geotextile blanket at least 12 inches. Remove and replace pipe damaged by Contractor operations. After trench backfill and compaction is complete, mandrel test replaced CPE and CPV pipe. Remove and re- lay sewer sections show ing signs of settlement or poor horizontal or vertical alignment as determined by the Engineer at no additional cost to the Department. MDOT Standard Specifications for Construction Section 402
4-17 1. Corrugated Plastic Pipe (CPE and CPV). Provide homing marks on
CPE and CPV pipe sections and joint material to show the correct alignment of the pipe sections and joint material during field installation. After trench backfill and compaction is complete, the Engineer will select at least 50% of the installed length of each size of CPE and CPV pipe for deformation testing. Provide the labor and equipment that are required to com plete the testing. Unless otherwise approved by the Engineer, perform the mandrel test within 10 work days prior to pavement surfacing or completion of final grade. Use a nine-point mandrel with a diameter equal to 95 % of the nominal pipe diameter. Provide the Engineer with a proving-ring to verify the mandrel size. Pull the mandrel through the pipe by ha nd using non-mechanical means and without damaging the pipe. The Contractor may use laser profile technology to measure deflection as an approved alternative to mandrel testing. Remove and reinstall or replace pipe with a nominal diameter reduced by at least 5% at no additional cost to the Department. Reinstall only undamaged pipe. Do not reinstall pipe without the Engineer ’s approval. The Contractor is responsible for all expenses and delays caused by reinstallation or replacement of pipe.
2.Concrete Pipe . Install reinforced concrete elliptical pipe with the longer axis placed horizontally unless otherwi se required. Install Type HE elliptical pipe with the longer axis within 5 degrees of horizontal. Install Type VE elliptical pipe with the longer axis within 5 degrees of vertical. Install circular concrete pipe with elliptical reinforcement so the lift holes or manufacturer ’s marks are on the top of the pipe. Place pipe so the lift holes or manufacturer ’s marks desig nating the top and bottom of the pipe are no more than 5 degrees from the vertical plane through the longitudinal axis of the pipe. After installing the pipe, seal the lift holes with concrete plugs and waterproof.
3.Metal Pipe . Provide metal pipe with helic al corrugations with a continuous lock seam in accordance with subsection 909.05. MDOT Standard Specifications for Construction Section 402
4-18 Use of dissimilar types of base metal (steel or aluminum alloy) or
dissimilar types of coatings on steel (zinc or aluminum) in a single line of pipe is prohibited. Construct ion between dissimilar metal type pipes is not allowed unless a drainage structure is used to transition between the two dissimilar type metal s. Changing materials at the drainage structure is allowed if the roughness coefficients have been adjusted accordingly. Use coupling bands of the same base metal and coating metal as the pipe.
D.Sewer Taps. Make connections to storm sewers owned by count ies, municipalit ies, or drain commission s in accordance with the regulations of the owner and as required by the contract. If a conflict exists between the owner ’s regulations and these specifications, the owner ’s regulations will take precedence. For existing storm sewers with plugs or bulkheads , remove plugs or bulkheads without damaging the existing sewer and make watertight joint connections. Remove material in accordance with subsection 204.03.B . If tapping an existing pipe, cut an opening in the receiving pipe at least 6 inches larger than t he outside diameter of the inlet pipe. Insert the inlet pipe and cut flush with the inner wall of the receiving pipe. Pack a layer of mortar at least 3 inches thick around the inlet pipe and strike smooth with the inner wall of the receiving pipe. Encase t he inlet pipe on the outside of the connection with concrete to provide bearing under the pipe. Repair or replace existing pipe damaged by Contractor tapping operations at no additional cost to the Department. Do not direct tap sewer inlet pipes with outsi de diameters greater than half the inside diameter of the trunk sewer. Construct a manhole structure for these taps in accordance with section 403. Obtain the Engineer ’s approval before using other methods of tapping existing sewers.
E.Sewer Bulkheads. Construct sewer bulkheads using Grade 3000 concrete or brick or block masonry. Extend the bulkhead at least 1 foot into the pipe from the inner wall of the drainage structure. Construct masonry bulkheads in accordance with subsection 403.03. A.
F.Backfilling. Backfill in accordance with subsection 401.03.D .
G.Sewer Jacked in Place. Jack sewers in place in accordance with subsection 401.03.G .
H.Disposal of Surplus Material. Take possession and dispose of surplus material in accordance with subsection 205.03.P . MDOT Standard Specifications for Construction Section 402
4-19 I. Cleanout. Maintain storm sewers installed on the project. Verify that
installed sewers are free of silt, debris, and other deleterious material at the time of final acceptance and in accordance with section 209.
J.Video Inspection of Sewer Pipe . Use closed circuit television to inspect required storm sewers. Dewater or divert flow in sewers for inspection. Video inspection is not required for extensions of existing catch basin leads less than 20 feet. After backfilling and compacting the trench, and within 10 working days prior to pavement surfacing or completion of final grade, conduct the inspection of sewers under pavement unless otherwise approved by the Engineer. For sewers not under pavement, a fter backfilling and compacting the trench, conduct the inspection as close to project completion as possible but allow time for corrective action as determined by the video inspection and directed by the Engineer.
1.Traffic Control . Obtain the Engineer ’s approval of traffic control measures at least 5 days before beginning work. Propose a traffic control plan in accordance with the Michigan Manual of Uni form Traffic Control Devices (MMUTCD) and the maintaining traffic plans in the contract . Unless otherwise approved by the Engineer, keep traffic lanes open. For necessary lane or shoulder closures, use traffic control measures in accordance with the traffic control plan.
2.Equipment . Use a camera designed and constructed for inspecting sewers and equipped with the following features:
a.A pan and tilt head external to the main body of the camera to allow inspection of the sewer joints and cracks or other defects;
b.Lighting to allow a clear picture of the perimeter of the pipe; and
c.Underwater operation capable of producing a picture quality that is satisfactory to the Engineer.
d.Show or document camera magnification at all t imes in the video. If the Engineer determines the video quality is not satisfactory, re-inspect the pipes to obtain acceptable results at no additional cost to the Department. Use continuous running video capable of recording audio and video information. Include the date (month, day , and year) and camera location. Provide a continuous record of the sewer section from manhole to manhole or from end to end. Use high quality, color, digital MDOT Standard Specifications for Construction Section 402
4-20 format at a standard play speed. Obtain the Engineer ’s approval
before using other recording media.
3.Sewer Flow Control. For video inspection, p rovide flow control to bring the depth of flow in the sewer pipe to within the range specified in subsection 402.03.J. 6.a. Before starting work , submit the proposed method of sewer flow control to the Engineer for approval .
a.Depth of Flow. Lower the depth of flow in the sewer during the videotaping operation to less than 2 inches. Reduce flow by plugging or blocking the flow or by pumping the flow and bypassing the pipe section during inspection, as approved by the Engineer.
b.Plugging or Blocking. Insert a sewer line plug into the line upstream of the section undergoing inspection. Use a plug designed to allow the release of portions of the flow. During video inspection, reduce the flow depth to 2 inches. Restore norm al flow after completing the work. Meter flow discharge to prevent erosion.
c.Pumping and Bypassing. For pumping and bypassing, supply the pumps, conduits, and other equipment to divert the flow around the sewer section undergoing inspection. Provide a bypas s system with a capacity to handle existing flow plus additional flow that may occur during a rain event. Provide the labor and supervision required to set up and operate the pumping and bypassing system.
d.Flow Control Precautions. If the flow in a sewer li ne is plugged, blocked, or bypassed, protect the sewer lines from damage that may result from sewer surcharging. Do not cause flooding or damage to public or private property while controlling sewer flow .
4.Procedure . Move the camera through the line at a rate no greater than 0.5 feet per second, stopping as required to doc ument the joint and pipe conditions. Use winches, cable, powered rewinds, or other devices that do not obstruct the camera view or interfere with proper documentation of the pipe conditions. Adjust the camera to travel above the level of the flow in the pipe. If the camera encounters a dip in the pipe such that the water rises above the springline of the p ipe or if the camera lens becomes submerged, withdraw the camera and re-insert it from the other end as far as possible. Do not back the camera into a pipe undergoing inspection. Measure the distance to the location of defects above ground using a meter device. Marking defect locations on the cable to measure the MDOT Standard Specifications for Construction Section 402
4-21 distance to defects is not allowed. Provide a distance meter with an
accuracy within 1 foot and check using a walking meter, roll -a-tape, or other device.
5.Documentation . Provide the inspection to the Engineer in a digital format . Include a written log of damages or installation defects, including pipe deformation, cracking, joint separation, corrosion, perforation, and other features identified in the video. Provide a digital copy of the log to the Engineer. Locate the damage or defect by meter marking of the video in the inspection log. Label the videos to describe the reaches of sewer or culverts contained in the videos, including street location and manhole numbers. If manhole numbers are not provided, assign a numbering system to allow identification in the inspection report and video. 402.04. Measurement and Payment Pay Item Pay Unit Sewer, Cl __, __ inch, Tr Det __ ........................................................ Foot Sewer, Reinf Conc Ellip, (shape) Cl __, (rise) by (span) inch, Tr Det __ ............................................................................... Foot Sewer, Cl __, __ inch, Jacked in Place ............................................. Foot Sewer Tap, __ inch ........................................................................... Each Sewer Bulkhead, __ inch ................................................................. Each Trench Undercut and Backfill .................................................. Cubic Yard Dewatering System, Trench .............................................................. Foot Video Taping Sewer and Culv Pipe ................................................... Foot
A.Sewer and Sewer, Reinforced Concrete Elliptical. The Engineer will measure Sewer and Sewer, Reinf Conc, Ellip of the size, class, and trench deta il required, in place from center to center of manholes, catch basins, or inlets. The unit price for Sewer and Sewer, Reinf Conc, Ellip includes the cost of excavation, backfill, and geotextile blanket.
B.Sewer, Jacked in Place. The Engineer will measure Sewer, Jacked in Place of the size and class required, by length, as determined by multiplying the number of units jacked by the commercial laying length. The unit price for Sewer, Jacked in Place includes the cost of excavating the pit; providing and installing sheeting, bracing, and other safety devices; providing jacking equipment; drainage and dewatering; and other items associated with the operation.
C.Sewer Tap. The Engineer will measure Sewer Tap based on the inlet pipe size required, by each tap into an existing system. If tapping an existing sewer line using a drainage structure, the Department will pay for one sewer tap in addition to the drainage structure. MDOT Standard Specifications for Construction Section 402
4-22 D. Sewer Bulkhead . The Engineer will measure only sewer bulkheads for
storm sewers with a diameter larger than 12 inches. The cost of constructing sewer bulkheads for pipes with a diameter less than or equal to 12 inches or constructed as part of abandoning or removing drainage structures as shown on the plans is included in the unit prices for related pay items. The Department will pay separately for bulkheading pipes greater than 12 inches.
E.Trench Undercut and Backfill . The Engineer will measure Trench Undercut and Backfill by calculating the volume from the length, depth, and width of undercut authorized by the Engineer and shown on the plans. The Engineer will not make allowance for sloping the sides of the trench. The unit price for Trench Undercut and Backfill includes the cost of excavation and disposal of material and providing, placing, and compacting 6A, 17A, 34R , or 46G aggregate to the bottom of trench elevation shown on the plans.
F.Rock Excavation. The Engineer will measure and the Department will pay separately for rock excavation in accordance with subsection 205.04.
G.Dewatering System, Trench. If the contract does not include a pay item for Dewatering System, Trench and the Contractor uses a dewatering syste m, the Department will not pay separately f or the system but will consider the cost to be included in the unit price for related pay items.
H.Trenchless. The Engineer may authorize trenchless methods , in place of open-cut construction methods. The Department will delete or proportionally reduce pay item quantities required for corresponding open-cut construction from the contract if the Engineer authorizes trenchless methods . The Department will not make an adjustment in the pay items of Minor Traf Devices or Traf Regulator Control. Payment for the work performed by trenchless methods will not exceed the unit price bid for the open- cut method. If the Engineer authorizes trenchless installation, Obstructions will be removed in accordance with subsection 718.03 .F.2. Additional payment or delays for removal of obstructions will not be considered.
I.Video Taping Sewer and Culvert Pipe . The unit price for Video Taping Sewer and Culv Pipe includes the cost of dewatering, flow control, video inspection, and documentation. The Department will pay separately for traffic maintenance and control in accordance with subsection 812.04. MDOT Standard Specifications for Construction Section 402
4-23 J. Obstructions. Engineer will measure, and the Department will p ay for the
removal of obstructions, which require the use of special procedures at the unit price for Obstruction Removal in accordance with subsection 718.04.D.
Source: Michigan Standard Specifications for Construction, 2020 Edition. Pages 220–229 of 1,146.