Difference between revisions of "403 - Drainage Structures"

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<center><span STYLE="font: 40pt arial;">'''Drainage Structures'''</span></center>
 
<center><span STYLE="font: 40pt arial;">'''Drainage Structures'''</span></center>
  
−
<center>[http://mdotcf.state.mi.us/public/specbook/files/2012/403%20Drainage%20Structures.pdf 2012 STANDARD SPECIFICATIONS FOR CONSTRUCTION - SECTION 403]</center>
 
  
  
−
==GENERAL==
+
==[[#GENERAL|GENERAL DESCRIPTION]]==
  
−
Drainage structures refer to manholes, catch basins, leaching basins, inlets and drop inlets as detailed on Standard Plan R-1 series or on project plans.
+
=== Definitions of Terms ===
 +
'''Aggregate:''' Aggregate refers to the stone used as the foundation of infrastructure. It typically consists of sand, gravel, crushed stone, or recycled materials like concrete.
  
−
A drainage structure shall not be placed within 5 feet (1.5 m) of the spring point of a street return so that the transverse joint will function properly.
+
'''Catch Basin:''' A catch basin is an inlet drainage structure located within a roadway or in the greenbelt adjacent to a roadway designed to capture storm water runoff. Catch basins have sumps below the outlet pipe to allow for debris washed into the catch basin to settle out before the water flows into the storm sewer system.  
  
−
Careful attention to grades and positioning of the footing from offset stakes is required, or the catch basin will not fit curb and gutter alignment. The inspector should observe or check all takeoff measurements made by the workmen.  Excavation for this type of structure is included with the structure, regardless of how it is backfilled.
+
'''Concrete:''' Concrete is a composite material made of cement, aggregate (such as sand or gravel), water, and sometimes admixtures. It is one of the most widely used construction materials, known for its strength, durability, and versatility.
  
−
Protection of adjacent sidewalk, curb or gutter, or other items not required to be removed, but endangered by sloping to the angle of repose, is the responsibility of the Contractor under subsection [http://mdotcf.state.mi.us/public/specbook/files/2012/107%20Legal%20Rel,%20Resp%20to%20Public.pdf 107.07] of the Standard Specifications for Construction (Protection and Restoration of Property), and the Contractor should be so reminded prior to commencing work.
+
'''Concrete Admixtures:''' Concrete admixtures are chemical additives added to concrete mixes to modify its properties or enhance its performance. Admixtures can improve workability, strength, durability, and other characteristics of concrete.
  
 +
'''Dense-Graded Aggregate:''' Dense-graded aggregate is a mixture of aggregates with an even distribution of different size aggregates.
 +
Drop Inlet: A drop inlet is a specialized part of a drainage structure used when an abrupt change of the flow line within the structure must be made. The drop can be made either inside or just outside of the structure. It is characterized by additional piping which aids to abruptly change the flow of water into a drainage structure.
  
−
==MATERIALS==
+
'''External Rubber Gaskets:''' External rubber gaskets are flexible sealing elements placed around the joints of pipes or culverts to create a watertight seal. They are typically placed with an appropriate type of primer for the gasket.
  
−
<span style="color: red"> -Reserved- </span>
+
'''Geotextile:''' Geotextile is a specialized fabric with the capacity to filter, separate, reinforce, and facilitate drainage in roadway applications.
 +
 
 +
'''Granular Material Classes II, IIA, IIAA, III, and IIIA:''' Granular Material Classes II, IIA, IIAA, III, and IIIA refer to different gradations or classifications of granular materials used in construction. These classifications are based on particle size distribution and properties such as compaction characteristics and permeability.
 +
 
 +
'''Leach Basin:''' A leach basin is an inlet drainage structure typically located in a greenbelt; it is designed to capture storm water runoff. Leach basins have a loose bottom, typically comprised of aggregate, which allow water to infiltrate into the ground.
 +
 
 +
'''Manhole:''' A manhole is a drainage structure used to alter the flow direction, combine multiple inlet pipes, or separate a long run of pipe. They have a flow channel in the bottom of the structure to aid in the direction of flow within the structure.
 +
 
 +
'''Mortar, Type R-2:''' Mortar, Type R-2 is a classification of masonry mortar specified by ASTM C270. It is a medium-strength mortar suitable for use in reinforced masonry, load-bearing walls, and other structural applications.
 +
 
 +
'''Precast Concrete:''' Precast concrete is produced by casting concrete in a mold or form to be cured in a controlled environment, which is then transported to the construction site for use.
 +
 
 +
=== General Overview ===
 +
Drainage structures play a crucial role in managing water flow and preventing water-related damage. They ensure excess water, whether from rainfall, snowmelt, or other sources, is effectively channeled away from roads, buildings, and other infrastructure and eventually discharged to a body of water such as ditches, basins, streams, rivers, or lakes. Properly designed drainage systems help maintain the structural integrity of roads by preventing water accumulation that can weaken the roadway.
 +
 
 +
{{top}}
 +
 
 +
==[[#MATERIALS|MATERIALS]]==
 +
All materials must meet acceptance requirements in the [https://www.michigan.gov/mdot/Business/Construction/Materials-Source-Guide Material Source Guide] and be listed on the Contractor-provided Material Source Lists in the project files.
 +
 
 +
Materials associated with the installation of drainage structures are to meet the sections listed in [https://mdotwiki.state.mi.us/images_construction/9/95/2020-Standard-Specifications-Construction.pdf#page=231 Subsection 403.02 of the Standard Specifications for Construction] or applicable special provisions.
 +
 
 +
=== Description of Materials ===
 +
==== Granular Material (Class II, IIA, IIAA, III, and IIIA) ====
 +
Granular backfill, often comprised of sand, is used to fill the space around existing or new features and the existing ground. Refer to [https://mdotwiki.state.mi.us/images_construction/9/95/2020-Standard-Specifications-Construction.pdf#page=816 Section 902 of the Standard Specifications for Construction] for material requirements.
 +
 
 +
==== Brick and Block ====
 +
Brick and block are rectangular in shape and typically made of concrete. Blocks tend to be larger than bricks and may have hollow cores for lighter weight or insulation.
 +
 
 +
==== Adjustment Rings ====
 +
# Adjustments rings used to bring the drainage structure cover to the proper finished elevation include: Metal adjustor ring.
 +
# Precast concrete adjusting ring.
 +
# Masonry in a full mortar bed.
 +
# Alternate adjustor selected from the Qualified Products List within the [https://www.michigan.gov/mdot/Business/Construction/Materials-Source-Guide Material Source Guid]e
 +
Precast concrete adjustment rings must meet AASHTO M199 and be a minimum of 4 inches thick.
 +
 
 +
==== Geosynthetics ====
 +
Geosynthetics are synthetic fabrics made from materials like polypropylene or polyester, primarily used for separating materials, such as a sand subbase and an aggregate base. Geosynthetics, such as biaxial geogrids, can provide stabilization to a road base by interlocking with aggregate materials to improve overall stability. In some cases, geosynthetic fabrics are used to facilitate the drainage of storm water that infiltrates the road base by directing the water to an underdrain system or to ditches. These materials are important because they enhance the structural integrity of infrastructure, reduce the need for additional material layers, improve drainage, and extend the lifespan of roadways by reducing soil movement and providing necessary reinforcement.
 +
 
 +
===== Woven Geotextile Fabric =====
 +
Woven geotextile fabric can be made of polyester or polypropylene slit films, fibrillated yarns, or monofilaments. Individual threads are woven to create strong geotextile fabric used for separation and reinforcement. The texture is an easily seen coarse weave. Woven geotextiles are semi-impermeable. Due to their poor permeability, woven geotextiles should not be used in areas where vertical drainage is critical.
 +
{|
 +
|+
 +
|-
 +
| [[File:Woven_Geotextile_Fabric_Close-Up.jpg|200px|thumb|center|Woven Geotextile Fabric Close-Up]] || [[File:Woven_Geotextile_Fabric_Roll.jpg|200px|thumb|center|Woven Geotextile Fabric Roll]]
 +
|}
 +
 
 +
===== Non-Woven =====
 +
Non-woven geotextile fabric is made of synthetic materials such as polyester or polypropylene fibers. Short and long fibers are bound together through needle punching or other methods, and heat treatment is usually applied to improve strength. The texture is similar to felt material. Non-woven fabric is more permeable than woven fabric and is used for filtration and separation.
 +
{|
 +
|+
 +
|-
 +
| [[File:Non-Woven_Geotextile_Fabric_Close-Up.jpg|200px|thumb|center|Non-Woven Geotextile Fabric Close-Up]] || [[File:Non-Woven Geotextile Fabric Roll.jpg|200px|thumb|center|Non-Woven Geotextile Fabric Roll]]
 +
|}
  
 +
=== Pictures of Materials ===
  
−
==CONSTRUCTION==
+
<gallery>
 +
Sound-earth-3.jpg|''Sound Earth''
 +
Class_III_Granular_Material_(Sand).jpg|''Granular Material Class III (Sand)
 +
403 (2).jpg|''Concrete Brick''''
 +
403 (3).jpg|''Type I Portland Cement''
 +
403 (13).jpg|''Precast Concrete Structure with Flat Top (Left Structure) and with Cones (Middle and Right Structures)''
 +
401-012.jpg|Class II Sand
 +
</gallery>
  
 +
{{top}}
  
−
===Construction Methods===
+
==[[#EQUIPMENT|EQUIPMENT]]==
 +
The following of equipment can be used:
 +
* Excavator
 +
* Backhoe
 +
* Front end loader
 +
* Occasionally bulldozer and vibratory roller for aggregate compaction
 +
* Plate compactor
 +
* Ho-Pac attachment
 +
* Gas powered rammer tamping machine
 +
* Air powered pogo thumper hammer
 +
* Sand/stone box
 +
* Portable cement mixer
 +
* Cement/mortar mixing tub
 +
* Portable generator
 +
* Electric submersible pump
 +
* Trash pump
 +
* Pipe laser
 +
* Transit or laser level
 +
* Leveling/grade pole
 +
* Electric impact wrench
 +
* Pipe/spud bar
 +
* Small hand tools (shovel, level, pipe “cutoff” saw, etc.)
 +
* Direct tap machine
  
−
Excavation for drainage structures is to be performed in accordance with subsection [http://mdotcf.state.mi.us/public/specbook/files/2012/206%20Exc,%20Backfill%20for%20Str.pdf 206.03] of the Standard Specifications for Construction.
+
=== Pictures of Equipment ===
 +
<gallery>
 +
Excavator-4.jpg|''Excavator''
 +
Laser transit.jpg|''Laser Transit''
 +
401-017.jpg|''Portable Concrete Mixer''
 +
401-018.jpg|''Plate Compactor''
 +
403 (10).jpg|''Placing a Precast Drainage Structure Unit''
 +
403 (11).jpg|''Coring a Storm Sewer Pipe to Install a Structure on Top of the Pipe''
 +
</gallery>
 +
{{top}}
  
−
The concrete portions of the drainage structures are constructed according to subsection [http://mdotcf.state.mi.us/public/specbook/files/2012/706%20Str%20Conc%20Construction.pdf 706.03] of the Standard Specifications for Construction. Concrete is not to be cast when the temperature of the concrete is above 90°F (32°C).
+
==[[#PRECONSTRUCTION|PRECONSTRUCTION]]==
 +
Prior to the start of construction, the Inspector should perform the following:
 +
# Inspect the structures and material upon arrival to site.
 +
#* Verify the materials meet the requirements contained in the plans, specifications, and any addenda.
 +
#** The structures must be accompanied by the manufacturer’s certification, tested stock reports, or other requirements as specified in the [https://www.michigan.gov/mdot/business/construction/materials-quality-assurance-procedures Materials Quality Assurance Procedures Manual].
 +
#** Visually inspect the structures and materials for defects originating from the manufacturing process or occurring during delivery and unloading at the site (such as cracks, fractures, exposed rebar, deformities, etc.). Any damaged should be promptly rejected by the Engineer.
 +
# Verify approved shop drawings, dewatering plans, temporary cofferdams, and all applicable documents that require approval were submitted by the Contractor.
 +
#* Review pipe diameters and structure height to verify a pipe does not conflict with the cone or flat top section of the structure.
 +
# Verify the survey stakes are placed according to the plans and the appropriate invert elevations, rim elevations, and pipe and structure IDs are labeled on the stakes.
 +
#* Ensure proper offset stakes are placed as stakes placed in the location of the proposed culvert will be removed when excavation begins.  
 +
# Verify existing underground utility markings.  
 +
#* Take note of any potential utility crossings and reference the plans and profiles to ensure minimum clearances are met.
 +
# Review the plans and the Special Provision for Maintenance of Traffic. There may be restrictions or staging requirements for installation. Installation restrictions are typically associated with staging requirements on a project and access to side streets and driveways.
 +
# Hold an onsite meeting with the Contractor to discuss:
 +
#* The construction method that will be used to complete the work.
 +
#* Concerns with utilities that may be near the excavation and require additional care.
 +
#* Required traffic control measures, proximity of traffic to the work area, and maintaining driveways during construction.
 +
#* Communication required if impacting residents or businesses during installation.
 +
#** Residents and businesses should be contacted if there will be disruptions to services. Coordination by the Contractor with impacted users may be required if disruption is necessary.
 +
#* Review local ordinances.
 +
#* Disposal of excavated material and material stockpile locations. The Contractor should provide authorization letters to the Engineer noting material stockpile and disposal locations.
 +
#* Soil erosion and sedimentation control measures that will be utilized to minimize soil erosion and subsequent sedimentation.
 +
#* Obtaining geosynthetic material samples for testing.
 +
#* Methods for securing the site during work operations and at the end of each workday.  
  
 +
{{top}}
  
−
====Placing Brick and Block Masonry====
+
==[[#CONSTRUCTION|CONSTRUCTION]]==
 +
=== Excavation ===
 +
Construction of drainage structures begins with excavation. Excavation may include the removal of an existing drainage items, such as structures, sewers, culverts, etc. or removal of pavement. Removal quantities should be recorded as required in the specifications. Perform excavation for constructing, adjusting, and temporarily lowering drainage structures, precast manhole tees, manhole bases, and manhole risers in accordance with [https://mdotwiki.state.mi.us/images_construction/9/95/2020-Standard-Specifications-Construction.pdf#page=163 Subsection 206.03.A of the Standard Specifications for Construction].
  
−
Masonry with mortar is not to be placed when the air temperature is at 36°F (2°C) and falling. Any work damaged by frost is to be removed and replaced.
+
=== Dewatering ===
 +
Dewatering of the excavation may be required if either the groundwater elevation or water in the existing drainage feature is inundating the trench bottom. If pumps are employed to control the water, proper soil erosion and sedimentation control should be employed as well. Running the discharge of a pump through a filter bag is a common requirement. In some cases, multiple filter bags may be required. Direct discharge of pumped water to a watercourse is prohibited.
  
−
The first set of bricks or blocks is placed on a full bed of mortar.  The bricks or blocks are then laid in courses with mortar joints 0.5 inch (13 mm) thick ± 0.1 inch (3 mm). Mortar joints should be of uniform thickness throughout the structure. Joints are staggered by half the length of the brick or block on adjoining courses.  The joints should be struck off and pointed so that the exposed surface is true and smooth.
+
=== Bedding ===
 +
Precast concrete footings must be supported by a compacted 6-inch granular subbase as specified in the [https://mdotjboss.state.mi.us/stdplan/getStandardPlanDocument.htm?docGuid=b5c9ac71-4455-44d2-b61a-7d29a2507c0a Standard Plan R-1 series].
  
−
A 0.5 inch (15 mm) thick plaster coat of mortar shall be applied to the outer surface of all structures and to the inner surface below the outlet flow line on all catch basins with traps and sumps. The joints should be raked, and the brick or block is to be wet prior to placing the plaster coat. The brick or block surface should be allowed to sufficiently dry to provide for proper bonding of the plaster coat.
+
=== Concrete Construction ===
 +
The Contractor must construct concrete portions of drainage structures in accordance with [https://mdotwiki.state.mi.us/images_construction/9/95/2020-Standard-Specifications-Construction.pdf#page=395 Subsection 706.03 of the Standard Specifications for Construction]. They cannot cast drainage structures if the concrete temperature is above 90°F.
  
 +
=== Brick and Block Masonry ===
 +
Masonry with mortar cannot be placed when the air temperature is at 36°F and falling. Any work damaged by frost is to be removed and replaced at no cost to the contract.
  
−
====Brick====
+
The Contractor will place the first set of bricks or blocks on a full bed of mortar. The bricks or blocks are then laid in courses with mortar joints 0.5 inch thick, ± 0.1 inch. Mortar joints should be of uniform thickness throughout the structure. Joints must be staggered by half the length of the brick or block on adjoining courses. The joints should be struck off and pointed so that the exposed surface is true and smooth.
 +
The Contractor should rake the joints and wet the brick or block prior to placing the plaster coat. A 0.5-inch-thick plaster coat of mortar must be applied to the outer surface of all structures and to the inner surface below the outlet flow line on all catch basins with traps and sumps. The brick or block surface must be allowed to sufficiently dry to provide for proper bonding of the plaster coat.
  
−
All brick shall be thoroughly wet.  The brick surface should be allowed to dry sufficiently enough to prevent slipping on the mortar.  Broken or chipped brick should not be used on the faces of the structure.  A course made of headers should be placed a minimum of every seventh course.
+
[[File:403 (12).jpg|300px]]
  
 +
''Construction of a Block Drainage Structure''
  
−
====Precast Reinforced Concrete Units====
+
=== Precast Units ===
 +
The Contractor should use cast-in-place concrete in accordance with [https://mdotwiki.state.mi.us/images_construction/9/95/2020-Standard-Specifications-Construction.pdf#page=232 Subsection 403.03.A.2 of the Standard Specifications for Construction] or precast concrete footings. Construct precast reinforced concrete units in accordance with the contract and the [https://mdotjboss.state.mi.us/stdplan/getStandardPlanDocument.htm?docGuid=b5c9ac71-4455-44d2-b61a-7d29a2507c0a Standard Plan R-1 series]. Seal the joints with mortar in accordance with [https://mdotwiki.state.mi.us/images_construction/9/95/2020-Standard-Specifications-Construction.pdf#page=232 Subsection 403.03.A.3 of the Standard Specifications for Construction] or use butyl rubber sealant that conforms to ASTM C990.
  
−
Precast reinforced concrete units are to be constructed according to the standard plan or as detailed on the plans. The joints shall be sealed with mortar as described above for Placing Brick and Block Masonry.
+
The footings shall be either cast-in-place or precast concrete in accordance with the [https://mdotjboss.state.mi.us/stdplan/getStandardPlanDocument.htm?docGuid=b5c9ac71-4455-44d2-b61a-7d29a2507c0a Standard Plan R-1 series]. Precast concrete footings must be supported on a compacted 6-inch granular material Class II layer.  
  
−
The footings shall be either poured-in-place or precast concrete.  Precast concrete footings must be supported by placing them on a compacted 6 inch (150 mm) subbase of Granular Material Class II.
+
Flow channels may not come precast in all manhole structures. Prior to final acceptance, a flow channel must be installed in all manholes regardless of whether the structure is precast or cast-in-place at the site.
  
 +
{|
 +
|+
 +
|-
 +
| [[File:403 (13).jpg|300px]] || [[File:403 (14).jpg|300px]]
 +
|-
 +
| ''Precast Concrete Drainage Structures'' || ''Placement of Precast Drainage Structures''
 +
|}
  
−
===Backfilling Drainage Structures===
+
=== Steel Reinforcement ===
 +
The Contractor must install steel reinforcement as required in accordance with [https://mdotwiki.state.mi.us/images_construction/9/95/2020-Standard-Specifications-Construction.pdf#page=395 Subsection 706.03 of the Standard Specifications for Construction] and the [https://mdotjboss.state.mi.us/stdplan/getStandardPlanDocument.htm?docGuid=b5c9ac71-4455-44d2-b61a-7d29a2507c0a Standard Plan R-1 series].
  
−
Backfilling is to be done in accordance with subsection [http://mdotcf.state.mi.us/public/specbook/files/2012/401%20Pipe%20Culverts.pdf 401.03] of the Standard Specifications for Construction and as described under [[401 - Culverts|Section 401, Backfilling of Culverts]] of this manual.
+
=== Inlet and Outlet Pipes ===
 +
The Contractor must extend inlet and outlet pipes through the outside wall surface of the manhole a sufficient length to allow for pipe connections. The bell must be removed from the first length of the outlet pipe projecting through the wall of the manhole. Masonry or other approved product must be used to create a seal around the pipes to prevent leakage.
  
 +
A good seal around pipes entering the drainage structure is key to preventing infiltration into the system. Ideally, the hole in the drainage structure is 3 to 6 inches wider than the pipe so only mortar is needed to seal the joint between the structure and the pipe. If the hole is too larger for just mortar to fill, non-corrosive spacers, such as brick and block, can be used to fill the void. The mortar seal around the pipe should appear smooth. This is typically completed using a brush dipped in water to prevent the mortar from sticking to the brush.
  
−
===Adjusting Drainage Structures===
+
Refer to [https://mdotwiki.state.mi.us/images_construction/9/95/2020-Standard-Specifications-Construction.pdf#page=210 Section 401] and [https://mdotwiki.state.mi.us/images_construction/9/95/2020-Standard-Specifications-Construction.pdf#page=221 Section 402] of the Standard Specifications for Construction for additional information on pipe placement.
  
−
Refer to subsection [http://mdotcf.state.mi.us/public/specbook/files/2012/403%20Drainage%20Structures.pdf 403.04] of the Standard Specifications for Construction, as well as any special provisions included in the proposal, for information on adjusting drainage structures.
+
Additionally, underdrains may be required to be tapped into drainage structures. Refer to [https://mdotwiki.state.mi.us/images_construction/9/95/2020-Standard-Specifications-Construction.pdf#page=239 Section 404 of the Standard Specifications for Construction] for additional information.
 +
 +
=== Backfilling Drainage Structures ===
 +
Backfilling must be done in accordance with [https://mdotwiki.state.mi.us/images_construction/9/95/2020-Standard-Specifications-Construction.pdf#page=214 Subsection 401.03.D of the Standard Specifications for Construction] and the [https://mdotjboss.state.mi.us/stdplan/getStandardPlanDocument.htm?docGuid=b5c9ac71-4455-44d2-b61a-7d29a2507c0a Standard Plan R-1 series].
  
−
Final adjustment of the drainage structures within the HMA pavement section should be made immediately before the placement of the top course or overlay, if only one course is applied. Adjustments made after the final top course is applied shall be constructed according to the details on the plans. The pay item of '''Drainage Structure Cover, Adjust, Case 1 (or Case 2)''' applies when the elevation of the cover is changed up or down 6 inches (150 mm) or less. The cover should be adjusted to the required elevation by supporting it on a metal ring adjustor, on a concrete collar, or on masonry in a full mortar bed. Adjusted covers shall be held firmly in place.
+
Granular material Class III must be used in backfilling around structures that fall within the 1:1 influence from the edge of the pavement or back of curb.
 +
 
 +
The Inspector will perform density checks to assure 95% compaction is achieved.
 +
 
 +
=== Drainage Structure Covers ===
 +
The Contractor will provide and install new covers, including frames and grates, on new or existing structures as called for in the plans. Castings are to be set onto a full bed of mortar. The mortar must be pointed up and any voids filled for both the inside and outside of the casting. The finished mortar should have a smooth continuous finish.
 +
 
 +
Drainage structure cover types can be located in the Standard Plans as noted in following table. The required structure cover type is typically indicated in the plan view of the project plans or the associated table for drainage work. All covers requiring bolts must have bolts installed and tightened prior to final acceptance.  
  
 
{| class="wikitable"
 
{| class="wikitable"
 +
|+
 +
|-
 +
! Standard Plan Series !! Cover Type
 +
|-
 +
| R-7 || COVER B
 
|-
 
|-
−
!
+
| R-8 || COVER C
−
<center>'''Item'''</center>
 
−
!
 
−
<center>'''Description'''</center>
 
 
|-
 
|-
−
|
+
| R-8X || COVER CX
−
'''Drainage Structure Cover, Adjust, Case 1'''
 
−
|
 
−
Applies to structures located within existing pavement, curb or curb and gutter.
 
 
|-
 
|-
−
|
+
| R-9 || COVER D
−
'''Drainage Structure Cover, Adjust, Case 2'''
+
|-
−
|
+
| R-9X || COVER DX
−
Applies to structures located outside the existing pavement, curb, or curb and gutter.
+
|-
 +
| R-10 || COVER E
 +
|-
 +
| R-12 || COVER G
 +
|-
 +
| R-14 || COVER J
 +
|-
 +
| R-15 || COVER K
 +
|-
 +
| R-18 || COVER Q
 +
|-
 +
| R-20 || COVER R
 +
|-
 +
| R-20X || COVER RX
 +
|-
 +
| R-22 || COVER V
 +
|-
 +
| R-23 || COVER W
 +
|-
 +
| R-24 || COVER VG
 
|}
 
|}
  
−
The adjacent pavement, curb, or curb and gutter should be removed and replaced to the existing grades or to the required elevations. Sawcutting of the existing pavement, curb, or curb and gutter where required are included in the item '''Drainage Structure Cover, Adjust, Case 1'''. Removal and replacement of pavement adjacent to the adjusted structure is also included in this pay item. Removal and replacement of curb and gutter adjacent to the adjusted structure is not included in the pay item and will be paid for separately with the use of other pay items. Placement of new covers on existing structures requires payment for the item '''Drainage Structure Cover, Adjust, Case 1 (or Case 2)''' as well as for the item '''Drainage Structure Cover'''.
+
=== Adjusting Drainage Structure Covers ===
 +
Refer to [https://mdotwiki.state.mi.us/images_construction/9/95/2020-Standard-Specifications-Construction.pdf#page=233 Subsection 403.03.C] and [https://mdotwiki.state.mi.us/images_construction/9/95/2020-Standard-Specifications-Construction.pdf#page=234 Subsection 403.03.D of the Standard Specifications for Construction], as well as any special provisions included in the proposal, for information on adjusting drainage structure covers.
 +
 
 +
Adjusting drainage structure covers applies when the new elevation of the cover is different from the existing elevation. Adjustment is included for a change no greater than 6 inches. If exceeding 6 inches in elevation change, refer to Subsection 403.03.D of the Standard Specifications for Construction for additional adjustment. All unsound portions of the structure must be removed in accordance with the Engineer’s direction.
 +
The Contractor must adjust the cover to the required elevation by supporting it on one of the following:
 +
# Metal adjustor ring
 +
# Precast concrete adjusting ring
 +
# Masonry in a full mortar bed
 +
# Alternate adjustor selected from the Qualified Products List within the [https://www.michigan.gov/mdot/Business/Construction/Materials-Source-Guide Material Source Guide]
 +
 
 +
Final adjustment of the drainage structures within the HMA pavement section should be made immediately before placement of the top course or overlay, if only one course is applied. Adjustments made after the final top course is applied shall be constructed according to the details on the plans. The adjacent pavement, curb, or curb and gutter should be removed and replaced to the existing grades or required elevations. Adjusted covers shall be held firmly in place. Placement of new covers is paid for separately. Drainage structure cover adjustment fall into two cases:
 +
 
 +
* Case 1 – Drainage Structure Cover Adjust:
 +
** Applies to structures located within existing pavement, curb, or curb and gutter.
 +
** Includes:
 +
*** Sawcutting the existing pavement, curb, or curb and gutter.
 +
*** Removing and replacing the adjacent pavement.
 +
*** Adjusting the cover up to 6 inches in elevation.
 +
** Curb and gutter removal and replacement is paid for separately.
 +
** [https://mdotjboss.state.mi.us/SpecProv/getSSSPDocumentById.htm?projNum=704577&fileName=20SP-403A-02.pdf Special Provision Adjusting Drainage Structure, Case 1, Modified (20SP-403A-02)] is a commonly used alternative method for performing Case 1 drainage structure cover adjustments. This method involves a rotary coring method instead of sawcutting.
 +
 
 +
* Case 2 – Drainage Structure Cover Adjust:
 +
**Applies to structures located outside the existing pavement, curb, or curb and gutter.
 +
**Includes:
 +
***Adjusting the cover up to 6 inches in elevation.
 +
 
 +
=== Drainage Structure Taps ===
 +
Refer to [https://mdotwiki.state.mi.us/images_construction/9/95/2020-Standard-Specifications-Construction.pdf#page=234 Subsection 403.03.E of the Standard Specifications for Construction] and any applicable special provisions included in the proposal for information on taps.
 +
 
 +
If tapping an existing drainage structure is required, the Contractor will cut an opening into the receiving structure at least equal to the outside diameter of the inlet pipe plus 6 inches and insert the pipe. The Contractor will pack a layer of mortar at least 3 inches thick around the inlet pipe and strike it smooth with the inner wall of the receiving structure. If the existing drainage structure is damaged by Contractor operations during tapping, it must be repaired or replaced at no cost to the contract.
 +
 
 +
Tap directly to a sewer or culvert in accordance with [https://mdotwiki.state.mi.us/images_construction/9/95/2020-Standard-Specifications-Construction.pdf#page=225 Subsection 402.03.D of the Standard Specifications for Construction].
  
 +
=== Cleanout of New Structures ===
 +
Drainage structures, including catch basins, manholes, leaching basins, and drop inlets installed for the project must be maintained throughout the duration. They may require cleaning by a Vac Truck or other methods. At the time of final acceptance, drainage structures must be free of silt, debris, and other deleterious material. During final inspection, each drainage structure should be marked to indicate it is in an approved condition. Cleaning of new structures is not a separate pay item.
  
−
==MEASUREMENT AND PAYMENT==
+
=== Cleanout of Existing Structures ===
 +
The Contractor should perform the initial inspection with the Inspector to determine if cleaning of existing structures is required. The Inspector should create a log of existing structures to track cleaning and damage, especially damage that may become worse by the cleaning process. Cleaning methods may need to be adjusted to decrease the likelihood of existing damage worsening. Damage should also be communicated to the Engineer to determine needed repairs.
 +
 
 +
Cleaning of drainage structures and leads includes removing sand, silt, and debris and prevent further contamination of the leads. The Contractor should clean the downstream drainage structure nearest the trunk sewer and place a temporary bulkhead so the trunk sewer remains clear. Upstream drainage structures and leads should only be cleaned after cleaning and bulkheading the downstream drainage structure.
 +
 
 +
The Contractor must dispose of waste generated from the cleaning process in accordance with the [https://mdotwiki.state.mi.us/images_construction/9/95/2020-Standard-Specifications-Construction.pdf#page=235 Subsection 403.03.G.1 of the Standard Specifications for Construction].
 +
 
 +
{{top}}
 +
 
 +
==[[#INSPECTION & TESTING|INSPECTION & TESTING]]==
 +
=== Inspection ===
 +
The Inspector should utilize, at a minimum, the following tools to perform the required inspection:
 +
* Measuring wheel
 +
* 100-foot tape measure or longer
 +
* 25-foot tape measure
 +
* Chaining pin
 +
* 6-foot stick ruler
 +
* 4-foot level
 +
* Working plans
 +
* Survey equipment
 +
* Camera
 +
The Inspector should take the following steps during construction:
 +
# Verify the correct drainage structure is used in accordance with the plans.
 +
#* Verify the drainage structure is free of defects or damage. All damage caused by the Contractor’s negligence must be repaired in accordance with [https://mdotwiki.state.mi.us/images_construction/9/95/2020-Standard-Specifications-Construction.pdf#page=485 Section 712 of the Standard Specifications for Construction] and at no cost to the contract.
 +
#* Verify the proper diameter of structure is supplied (diameter measurement is based on the inside diameter).
 +
#* Verify the correct number, size, and location of holes for pipe are formed in the structure.
 +
#* It is good practice to paint marks in 10-inch increments on the structure to ensure backfill is being placed appropriately.
 +
# Observe installation of the drainage structure is in accordance with manufacturer’s recommendations.
 +
#* Pay particular attention to structures in the curb line to prevent a gap between the interior edge of the structure and the face of casings such as the “Cover J” that does not have a flange at the edge of metal (E/M) face.
 +
#* Ensure the opening in the drainage structure is aligned with the curb line.
 +
#* For structures not within a curb line, align the structure opening so it is out of the wheel path of a vehicle, if possible.
 +
# Monitor excavation of the trench to ensure the drainage meets the elevation requirements shown on the plans.
 +
# Verify all bedding and backfill of excavated trenches is clean, dry, and meets design requirements.
 +
# Verify there is no debris in the drainage structure before installation.
 +
# Verify the lift holes are filled with mortar and waterproofed prior to backfilling.
 +
# Verify flow channels are installed in all manholes.
 +
# When the Contractor is connecting two structure sections, ensure:
 +
#* The structure joint is clean.
 +
#* The required joint seal is installed.
 +
#** If a gasket is used, verify the gasket is in accordance with the manufacturer’s recommendation and lubricated prior to assembly. (Butyl gaskets do not require lubrication prior to assembly.)
 +
#* The joint is seated properly.
 +
# Obtain grade shots and document the grades on the as-built plans.
 +
# Verify passing density shots are obtained on each lift of backfill material.
 +
# Record the density testing results of the backfill material in accordance with the [https://www.michigan.gov/mdot/-/media/Project/Websites/MDOT/Business/Construction/Standard-Specifications-Construction/CFS-Manuals/Density-Testing-Inspection-Manual.pdf?rev=6ea61069b3b649e5bbd9362f000a4e0b&hash=44138356CA520616DF23E2E1D8E49AE0 Density Testing and Inspection Manual] using the field established maximum density for the material being tested. The minimum testing frequency is shown in Appendix K (backfill) of this manual. The testing frequencies listed are minimums that are satisfactory for acceptance. However, it is emphasized that project conditions normally require more frequent testing for proper density control.
 +
# Compare the approved Material Source List with the tags on the geosynthetic to verify the appropriate material has been delivered to site.
 +
 
 +
=== Testing ===
 +
For evaluation of aggregate materials, use only certified aggregate sampling and testing technicians. Refer to the [https://www.michigan.gov/mdot/-/media/Project/Websites/MDOT/Business/Construction/Standard-Specifications-Construction/CFS-Manuals/Procedures-Aggregate-Inspection.pdf?rev=e2f19aadca344460afca48b7b9ddb31e&hash=5D3CB25E2CD084FACCFD616004CCEB82 Procedures for Aggregate Inspection manual] and project specifications for testing requirements and frequencies. The Engineer should track the approved testing of installed aggregate and coordinate with the respective testing lab to ensure the required number of aggregate tests for the project are being completed.
 +
Perform density testing on compacted backfill. All backfill, regardless of material used, is to be compacted to 95% of the maximum unit weight. The Inspector should ensure the minimum number of required density tests are being performed per the [https://www.michigan.gov/mdot/-/media/Project/Websites/MDOT/Business/Construction/Standard-Specifications-Construction/CFS-Manuals/Density-Testing-Inspection-Manual.pdf?rev=6ea61069b3b649e5bbd9362f000a4e0b&hash=44138356CA520616DF23E2E1D8E49AE0 Density Testing and Inspection Manual].
 +
 
 +
==== Geosynthetics ====
 +
Section 910.03 of the [https://www.michigan.gov/mdot/Business/Construction/Materials-Source-Guide Material Source Guide] specifies testing requirements for geosynthetics. If testing is required, allow for up to 28 days for it to be completed. Geotextile materials must meet the requirements of [https://mdotwiki.state.mi.us/images_construction/9/95/2020-Standard-Specifications-Construction.pdf#page=902 Section 910 of the Standard Specifications for Construction].
 +
 
 +
==== Precast Concrete Drainage Structures ====
 +
All precast structures must come from an approved manufacturer. Reference the plans for dimensions for all precast components.
 +
 
 +
==== Existing Site Material ====
 +
It is possible that material from the project site may be re-used for backfilling. However, the material must be stockpiled, and the required testing completed. The Contractor should complete gradation testing of samples taken from the stockpile. The respective MDOT material lab will confirm if the gradation of the onsite material meets the requirements for the desired backfill material. The material can be used only after acceptance by MDOT.
 +
 
 +
{{top}}
 +
 
 +
==[[#MEASUREMENT, DOCUMENTATION & PAYMENT|MEASUREMENT, DOCUMENTATION & PAYMENT]]==
 +
=== Measurement and Payment ===
 +
Refer to [https://mdotwiki.state.mi.us/images_construction/9/95/2020-Standard-Specifications-Construction.pdf#page=236 Subsection 403.04 of the Standard Specifications for Construction] for direction regarding measurement and payment for drainage structures.
 +
In general, drainage structures are paid for by each unit installed for the required inside diameter. Excavation, dewatering, joint wrapping, and backfill are covered within the drainage structure item. Drainage structures include the cost for supplying a concrete footing and up to 8 feet in depth for the structure.
 +
 
 +
For manholes to be considered complete, a flow channel must be installed within the structure.
 +
 
 +
Some items, like additional depth for drainage structures over 8 feet deep or manhole risers, are paid by the foot of depth required.
 +
 
 +
=== Documentation ===
 +
The primary report required for the payment of drainage structures, adjustments, and cleanout is the Daily Work Report (DWR). The Inspector should note in the remarks section of the report the condition of the base material during placement, material verification, and equipment and manpower used. The size of the structure placed and the invert elevations at all openings should be recorded for as-built records.
 +
The DWR should also note the following:
 +
# Additional depth measured for payment on drainage structures.
 +
# Final length of the lead cleaning and total quantity of structure cleaning.
 +
# Once the work is completed:
 +
#* Survey or other approved methods for verification construction conforms with the project documents.
 +
#* Volume and tonnage of bedding and backfill material placed.
 +
 
 +
[https://mdotjboss.state.mi.us/webforms/GetDocument.htm?fileName=1900.pdf Form 1900, Aggregate Inspection Daily Report], will need to be completed for every sublot of aggregate to track gradation acceptance.
 +
 
 +
[https://mdotjboss.state.mi.us/webforms/GetDocument.htm?fileName=0582B.pdf Form 0582B, Moisture & Density Determination - Nuclear Method], is used to record density testing results.
 +
 
 +
Delivery tickets must be verified for the source of material against the approved Material Source List. Each ticket must include the required information. Refer to [https://mdotwiki.state.mi.us/images_construction/9/95/2020-Standard-Specifications-Construction.pdf#page=110 Subsection 109.01.B.6 of the Standard Specifications for Construction] for the information required on each ticket.
 +
 
 +
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 +
 
 +
==[[#LOCAL AGENCY PROJECTS|LOCAL AGENCY PROJECTS]]==
  
 
<span style="color: red"> -Reserved- </span>
 
<span style="color: red"> -Reserved- </span>
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{{top}}
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 +
==[[#RAIL PROJECTS|RAIL PROJECTS]]==
 +
 +
<span style="color: red"> -Reserved- </span>
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{{top}}
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{{top}}
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[[Category:Construction Manual]]
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[[Category:Division 4]]
 +
[[Category:Section 403]]
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[[Category:New CM Format]]

Latest revision as of 17:22, 20 August 2025

403
Drainage Structures


GENERAL DESCRIPTION

Definitions of Terms

Aggregate: Aggregate refers to the stone used as the foundation of infrastructure. It typically consists of sand, gravel, crushed stone, or recycled materials like concrete.

Catch Basin: A catch basin is an inlet drainage structure located within a roadway or in the greenbelt adjacent to a roadway designed to capture storm water runoff. Catch basins have sumps below the outlet pipe to allow for debris washed into the catch basin to settle out before the water flows into the storm sewer system.

Concrete: Concrete is a composite material made of cement, aggregate (such as sand or gravel), water, and sometimes admixtures. It is one of the most widely used construction materials, known for its strength, durability, and versatility.

Concrete Admixtures: Concrete admixtures are chemical additives added to concrete mixes to modify its properties or enhance its performance. Admixtures can improve workability, strength, durability, and other characteristics of concrete.

Dense-Graded Aggregate: Dense-graded aggregate is a mixture of aggregates with an even distribution of different size aggregates. Drop Inlet: A drop inlet is a specialized part of a drainage structure used when an abrupt change of the flow line within the structure must be made. The drop can be made either inside or just outside of the structure. It is characterized by additional piping which aids to abruptly change the flow of water into a drainage structure.

External Rubber Gaskets: External rubber gaskets are flexible sealing elements placed around the joints of pipes or culverts to create a watertight seal. They are typically placed with an appropriate type of primer for the gasket.

Geotextile: Geotextile is a specialized fabric with the capacity to filter, separate, reinforce, and facilitate drainage in roadway applications.

Granular Material Classes II, IIA, IIAA, III, and IIIA: Granular Material Classes II, IIA, IIAA, III, and IIIA refer to different gradations or classifications of granular materials used in construction. These classifications are based on particle size distribution and properties such as compaction characteristics and permeability.

Leach Basin: A leach basin is an inlet drainage structure typically located in a greenbelt; it is designed to capture storm water runoff. Leach basins have a loose bottom, typically comprised of aggregate, which allow water to infiltrate into the ground.

Manhole: A manhole is a drainage structure used to alter the flow direction, combine multiple inlet pipes, or separate a long run of pipe. They have a flow channel in the bottom of the structure to aid in the direction of flow within the structure.

Mortar, Type R-2: Mortar, Type R-2 is a classification of masonry mortar specified by ASTM C270. It is a medium-strength mortar suitable for use in reinforced masonry, load-bearing walls, and other structural applications.

Precast Concrete: Precast concrete is produced by casting concrete in a mold or form to be cured in a controlled environment, which is then transported to the construction site for use.

General Overview

Drainage structures play a crucial role in managing water flow and preventing water-related damage. They ensure excess water, whether from rainfall, snowmelt, or other sources, is effectively channeled away from roads, buildings, and other infrastructure and eventually discharged to a body of water such as ditches, basins, streams, rivers, or lakes. Properly designed drainage systems help maintain the structural integrity of roads by preventing water accumulation that can weaken the roadway.

[top of page]

MATERIALS

All materials must meet acceptance requirements in the Material Source Guide and be listed on the Contractor-provided Material Source Lists in the project files.

Materials associated with the installation of drainage structures are to meet the sections listed in Subsection 403.02 of the Standard Specifications for Construction or applicable special provisions.

Description of Materials

Granular Material (Class II, IIA, IIAA, III, and IIIA)

Granular backfill, often comprised of sand, is used to fill the space around existing or new features and the existing ground. Refer to Section 902 of the Standard Specifications for Construction for material requirements.

Brick and Block

Brick and block are rectangular in shape and typically made of concrete. Blocks tend to be larger than bricks and may have hollow cores for lighter weight or insulation.

Adjustment Rings

  1. Adjustments rings used to bring the drainage structure cover to the proper finished elevation include: Metal adjustor ring.
  2. Precast concrete adjusting ring.
  3. Masonry in a full mortar bed.
  4. Alternate adjustor selected from the Qualified Products List within the Material Source Guide

Precast concrete adjustment rings must meet AASHTO M199 and be a minimum of 4 inches thick.

Geosynthetics

Geosynthetics are synthetic fabrics made from materials like polypropylene or polyester, primarily used for separating materials, such as a sand subbase and an aggregate base. Geosynthetics, such as biaxial geogrids, can provide stabilization to a road base by interlocking with aggregate materials to improve overall stability. In some cases, geosynthetic fabrics are used to facilitate the drainage of storm water that infiltrates the road base by directing the water to an underdrain system or to ditches. These materials are important because they enhance the structural integrity of infrastructure, reduce the need for additional material layers, improve drainage, and extend the lifespan of roadways by reducing soil movement and providing necessary reinforcement.

Woven Geotextile Fabric

Woven geotextile fabric can be made of polyester or polypropylene slit films, fibrillated yarns, or monofilaments. Individual threads are woven to create strong geotextile fabric used for separation and reinforcement. The texture is an easily seen coarse weave. Woven geotextiles are semi-impermeable. Due to their poor permeability, woven geotextiles should not be used in areas where vertical drainage is critical.

Woven Geotextile Fabric Close-Up
Woven Geotextile Fabric Roll
Non-Woven

Non-woven geotextile fabric is made of synthetic materials such as polyester or polypropylene fibers. Short and long fibers are bound together through needle punching or other methods, and heat treatment is usually applied to improve strength. The texture is similar to felt material. Non-woven fabric is more permeable than woven fabric and is used for filtration and separation.

Non-Woven Geotextile Fabric Close-Up
Non-Woven Geotextile Fabric Roll

Pictures of Materials

  • Sound Earth

  • Granular Material Class III (Sand)

  • Concrete Brick''

  • Type I Portland Cement

  • Precast Concrete Structure with Flat Top (Left Structure) and with Cones (Middle and Right Structures)

  • Class II Sand

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EQUIPMENT

The following of equipment can be used:

  • Excavator
  • Backhoe
  • Front end loader
  • Occasionally bulldozer and vibratory roller for aggregate compaction
  • Plate compactor
  • Ho-Pac attachment
  • Gas powered rammer tamping machine
  • Air powered pogo thumper hammer
  • Sand/stone box
  • Portable cement mixer
  • Cement/mortar mixing tub
  • Portable generator
  • Electric submersible pump
  • Trash pump
  • Pipe laser
  • Transit or laser level
  • Leveling/grade pole
  • Electric impact wrench
  • Pipe/spud bar
  • Small hand tools (shovel, level, pipe “cutoff” saw, etc.)
  • Direct tap machine

Pictures of Equipment

  • Excavator

  • Laser Transit

  • Portable Concrete Mixer

  • Plate Compactor

  • Placing a Precast Drainage Structure Unit

  • Coring a Storm Sewer Pipe to Install a Structure on Top of the Pipe

[top of page]

PRECONSTRUCTION

Prior to the start of construction, the Inspector should perform the following:

  1. Inspect the structures and material upon arrival to site.
    • Verify the materials meet the requirements contained in the plans, specifications, and any addenda.
      • The structures must be accompanied by the manufacturer’s certification, tested stock reports, or other requirements as specified in the Materials Quality Assurance Procedures Manual.
      • Visually inspect the structures and materials for defects originating from the manufacturing process or occurring during delivery and unloading at the site (such as cracks, fractures, exposed rebar, deformities, etc.). Any damaged should be promptly rejected by the Engineer.
  2. Verify approved shop drawings, dewatering plans, temporary cofferdams, and all applicable documents that require approval were submitted by the Contractor.
    • Review pipe diameters and structure height to verify a pipe does not conflict with the cone or flat top section of the structure.
  3. Verify the survey stakes are placed according to the plans and the appropriate invert elevations, rim elevations, and pipe and structure IDs are labeled on the stakes.
    • Ensure proper offset stakes are placed as stakes placed in the location of the proposed culvert will be removed when excavation begins.
  4. Verify existing underground utility markings.
    • Take note of any potential utility crossings and reference the plans and profiles to ensure minimum clearances are met.
  5. Review the plans and the Special Provision for Maintenance of Traffic. There may be restrictions or staging requirements for installation. Installation restrictions are typically associated with staging requirements on a project and access to side streets and driveways.
  6. Hold an onsite meeting with the Contractor to discuss:
    • The construction method that will be used to complete the work.
    • Concerns with utilities that may be near the excavation and require additional care.
    • Required traffic control measures, proximity of traffic to the work area, and maintaining driveways during construction.
    • Communication required if impacting residents or businesses during installation.
      • Residents and businesses should be contacted if there will be disruptions to services. Coordination by the Contractor with impacted users may be required if disruption is necessary.
    • Review local ordinances.
    • Disposal of excavated material and material stockpile locations. The Contractor should provide authorization letters to the Engineer noting material stockpile and disposal locations.
    • Soil erosion and sedimentation control measures that will be utilized to minimize soil erosion and subsequent sedimentation.
    • Obtaining geosynthetic material samples for testing.
    • Methods for securing the site during work operations and at the end of each workday.

[top of page]

CONSTRUCTION

Excavation

Construction of drainage structures begins with excavation. Excavation may include the removal of an existing drainage items, such as structures, sewers, culverts, etc. or removal of pavement. Removal quantities should be recorded as required in the specifications. Perform excavation for constructing, adjusting, and temporarily lowering drainage structures, precast manhole tees, manhole bases, and manhole risers in accordance with Subsection 206.03.A of the Standard Specifications for Construction.

Dewatering

Dewatering of the excavation may be required if either the groundwater elevation or water in the existing drainage feature is inundating the trench bottom. If pumps are employed to control the water, proper soil erosion and sedimentation control should be employed as well. Running the discharge of a pump through a filter bag is a common requirement. In some cases, multiple filter bags may be required. Direct discharge of pumped water to a watercourse is prohibited.

Bedding

Precast concrete footings must be supported by a compacted 6-inch granular subbase as specified in the Standard Plan R-1 series.

Concrete Construction

The Contractor must construct concrete portions of drainage structures in accordance with Subsection 706.03 of the Standard Specifications for Construction. They cannot cast drainage structures if the concrete temperature is above 90°F.

Brick and Block Masonry

Masonry with mortar cannot be placed when the air temperature is at 36°F and falling. Any work damaged by frost is to be removed and replaced at no cost to the contract.

The Contractor will place the first set of bricks or blocks on a full bed of mortar. The bricks or blocks are then laid in courses with mortar joints 0.5 inch thick, ± 0.1 inch. Mortar joints should be of uniform thickness throughout the structure. Joints must be staggered by half the length of the brick or block on adjoining courses. The joints should be struck off and pointed so that the exposed surface is true and smooth. The Contractor should rake the joints and wet the brick or block prior to placing the plaster coat. A 0.5-inch-thick plaster coat of mortar must be applied to the outer surface of all structures and to the inner surface below the outlet flow line on all catch basins with traps and sumps. The brick or block surface must be allowed to sufficiently dry to provide for proper bonding of the plaster coat.

403 (12).jpg

Construction of a Block Drainage Structure

Precast Units

The Contractor should use cast-in-place concrete in accordance with Subsection 403.03.A.2 of the Standard Specifications for Construction or precast concrete footings. Construct precast reinforced concrete units in accordance with the contract and the Standard Plan R-1 series. Seal the joints with mortar in accordance with Subsection 403.03.A.3 of the Standard Specifications for Construction or use butyl rubber sealant that conforms to ASTM C990.

The footings shall be either cast-in-place or precast concrete in accordance with the Standard Plan R-1 series. Precast concrete footings must be supported on a compacted 6-inch granular material Class II layer.

Flow channels may not come precast in all manhole structures. Prior to final acceptance, a flow channel must be installed in all manholes regardless of whether the structure is precast or cast-in-place at the site.

403 (13).jpg 403 (14).jpg
Precast Concrete Drainage Structures Placement of Precast Drainage Structures

Steel Reinforcement

The Contractor must install steel reinforcement as required in accordance with Subsection 706.03 of the Standard Specifications for Construction and the Standard Plan R-1 series.

Inlet and Outlet Pipes

The Contractor must extend inlet and outlet pipes through the outside wall surface of the manhole a sufficient length to allow for pipe connections. The bell must be removed from the first length of the outlet pipe projecting through the wall of the manhole. Masonry or other approved product must be used to create a seal around the pipes to prevent leakage.

A good seal around pipes entering the drainage structure is key to preventing infiltration into the system. Ideally, the hole in the drainage structure is 3 to 6 inches wider than the pipe so only mortar is needed to seal the joint between the structure and the pipe. If the hole is too larger for just mortar to fill, non-corrosive spacers, such as brick and block, can be used to fill the void. The mortar seal around the pipe should appear smooth. This is typically completed using a brush dipped in water to prevent the mortar from sticking to the brush.

Refer to Section 401 and Section 402 of the Standard Specifications for Construction for additional information on pipe placement.

Additionally, underdrains may be required to be tapped into drainage structures. Refer to Section 404 of the Standard Specifications for Construction for additional information.

Backfilling Drainage Structures

Backfilling must be done in accordance with Subsection 401.03.D of the Standard Specifications for Construction and the Standard Plan R-1 series.

Granular material Class III must be used in backfilling around structures that fall within the 1:1 influence from the edge of the pavement or back of curb.

The Inspector will perform density checks to assure 95% compaction is achieved.

Drainage Structure Covers

The Contractor will provide and install new covers, including frames and grates, on new or existing structures as called for in the plans. Castings are to be set onto a full bed of mortar. The mortar must be pointed up and any voids filled for both the inside and outside of the casting. The finished mortar should have a smooth continuous finish.

Drainage structure cover types can be located in the Standard Plans as noted in following table. The required structure cover type is typically indicated in the plan view of the project plans or the associated table for drainage work. All covers requiring bolts must have bolts installed and tightened prior to final acceptance.

Standard Plan Series Cover Type
R-7 COVER B
R-8 COVER C
R-8X COVER CX
R-9 COVER D
R-9X COVER DX
R-10 COVER E
R-12 COVER G
R-14 COVER J
R-15 COVER K
R-18 COVER Q
R-20 COVER R
R-20X COVER RX
R-22 COVER V
R-23 COVER W
R-24 COVER VG

Adjusting Drainage Structure Covers

Refer to Subsection 403.03.C and Subsection 403.03.D of the Standard Specifications for Construction, as well as any special provisions included in the proposal, for information on adjusting drainage structure covers.

Adjusting drainage structure covers applies when the new elevation of the cover is different from the existing elevation. Adjustment is included for a change no greater than 6 inches. If exceeding 6 inches in elevation change, refer to Subsection 403.03.D of the Standard Specifications for Construction for additional adjustment. All unsound portions of the structure must be removed in accordance with the Engineer’s direction. The Contractor must adjust the cover to the required elevation by supporting it on one of the following:

  1. Metal adjustor ring
  2. Precast concrete adjusting ring
  3. Masonry in a full mortar bed
  4. Alternate adjustor selected from the Qualified Products List within the Material Source Guide

Final adjustment of the drainage structures within the HMA pavement section should be made immediately before placement of the top course or overlay, if only one course is applied. Adjustments made after the final top course is applied shall be constructed according to the details on the plans. The adjacent pavement, curb, or curb and gutter should be removed and replaced to the existing grades or required elevations. Adjusted covers shall be held firmly in place. Placement of new covers is paid for separately. Drainage structure cover adjustment fall into two cases:

  • Case 1 – Drainage Structure Cover Adjust:
    • Applies to structures located within existing pavement, curb, or curb and gutter.
    • Includes:
      • Sawcutting the existing pavement, curb, or curb and gutter.
      • Removing and replacing the adjacent pavement.
      • Adjusting the cover up to 6 inches in elevation.
    • Curb and gutter removal and replacement is paid for separately.
    • Special Provision Adjusting Drainage Structure, Case 1, Modified (20SP-403A-02) is a commonly used alternative method for performing Case 1 drainage structure cover adjustments. This method involves a rotary coring method instead of sawcutting.
  • Case 2 – Drainage Structure Cover Adjust:
    • Applies to structures located outside the existing pavement, curb, or curb and gutter.
    • Includes:
      • Adjusting the cover up to 6 inches in elevation.

Drainage Structure Taps

Refer to Subsection 403.03.E of the Standard Specifications for Construction and any applicable special provisions included in the proposal for information on taps.

If tapping an existing drainage structure is required, the Contractor will cut an opening into the receiving structure at least equal to the outside diameter of the inlet pipe plus 6 inches and insert the pipe. The Contractor will pack a layer of mortar at least 3 inches thick around the inlet pipe and strike it smooth with the inner wall of the receiving structure. If the existing drainage structure is damaged by Contractor operations during tapping, it must be repaired or replaced at no cost to the contract.

Tap directly to a sewer or culvert in accordance with Subsection 402.03.D of the Standard Specifications for Construction.

Cleanout of New Structures

Drainage structures, including catch basins, manholes, leaching basins, and drop inlets installed for the project must be maintained throughout the duration. They may require cleaning by a Vac Truck or other methods. At the time of final acceptance, drainage structures must be free of silt, debris, and other deleterious material. During final inspection, each drainage structure should be marked to indicate it is in an approved condition. Cleaning of new structures is not a separate pay item.

Cleanout of Existing Structures

The Contractor should perform the initial inspection with the Inspector to determine if cleaning of existing structures is required. The Inspector should create a log of existing structures to track cleaning and damage, especially damage that may become worse by the cleaning process. Cleaning methods may need to be adjusted to decrease the likelihood of existing damage worsening. Damage should also be communicated to the Engineer to determine needed repairs.

Cleaning of drainage structures and leads includes removing sand, silt, and debris and prevent further contamination of the leads. The Contractor should clean the downstream drainage structure nearest the trunk sewer and place a temporary bulkhead so the trunk sewer remains clear. Upstream drainage structures and leads should only be cleaned after cleaning and bulkheading the downstream drainage structure.

The Contractor must dispose of waste generated from the cleaning process in accordance with the Subsection 403.03.G.1 of the Standard Specifications for Construction.

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INSPECTION & TESTING

Inspection

The Inspector should utilize, at a minimum, the following tools to perform the required inspection:

  • Measuring wheel
  • 100-foot tape measure or longer
  • 25-foot tape measure
  • Chaining pin
  • 6-foot stick ruler
  • 4-foot level
  • Working plans
  • Survey equipment
  • Camera

The Inspector should take the following steps during construction:

  1. Verify the correct drainage structure is used in accordance with the plans.
    • Verify the drainage structure is free of defects or damage. All damage caused by the Contractor’s negligence must be repaired in accordance with Section 712 of the Standard Specifications for Construction and at no cost to the contract.
    • Verify the proper diameter of structure is supplied (diameter measurement is based on the inside diameter).
    • Verify the correct number, size, and location of holes for pipe are formed in the structure.
    • It is good practice to paint marks in 10-inch increments on the structure to ensure backfill is being placed appropriately.
  2. Observe installation of the drainage structure is in accordance with manufacturer’s recommendations.
    • Pay particular attention to structures in the curb line to prevent a gap between the interior edge of the structure and the face of casings such as the “Cover J” that does not have a flange at the edge of metal (E/M) face.
    • Ensure the opening in the drainage structure is aligned with the curb line.
    • For structures not within a curb line, align the structure opening so it is out of the wheel path of a vehicle, if possible.
  3. Monitor excavation of the trench to ensure the drainage meets the elevation requirements shown on the plans.
  4. Verify all bedding and backfill of excavated trenches is clean, dry, and meets design requirements.
  5. Verify there is no debris in the drainage structure before installation.
  6. Verify the lift holes are filled with mortar and waterproofed prior to backfilling.
  7. Verify flow channels are installed in all manholes.
  8. When the Contractor is connecting two structure sections, ensure:
    • The structure joint is clean.
    • The required joint seal is installed.
      • If a gasket is used, verify the gasket is in accordance with the manufacturer’s recommendation and lubricated prior to assembly. (Butyl gaskets do not require lubrication prior to assembly.)
    • The joint is seated properly.
  9. Obtain grade shots and document the grades on the as-built plans.
  10. Verify passing density shots are obtained on each lift of backfill material.
  11. Record the density testing results of the backfill material in accordance with the Density Testing and Inspection Manual using the field established maximum density for the material being tested. The minimum testing frequency is shown in Appendix K (backfill) of this manual. The testing frequencies listed are minimums that are satisfactory for acceptance. However, it is emphasized that project conditions normally require more frequent testing for proper density control.
  12. Compare the approved Material Source List with the tags on the geosynthetic to verify the appropriate material has been delivered to site.

Testing

For evaluation of aggregate materials, use only certified aggregate sampling and testing technicians. Refer to the Procedures for Aggregate Inspection manual and project specifications for testing requirements and frequencies. The Engineer should track the approved testing of installed aggregate and coordinate with the respective testing lab to ensure the required number of aggregate tests for the project are being completed. Perform density testing on compacted backfill. All backfill, regardless of material used, is to be compacted to 95% of the maximum unit weight. The Inspector should ensure the minimum number of required density tests are being performed per the Density Testing and Inspection Manual.

Geosynthetics

Section 910.03 of the Material Source Guide specifies testing requirements for geosynthetics. If testing is required, allow for up to 28 days for it to be completed. Geotextile materials must meet the requirements of Section 910 of the Standard Specifications for Construction.

Precast Concrete Drainage Structures

All precast structures must come from an approved manufacturer. Reference the plans for dimensions for all precast components.

Existing Site Material

It is possible that material from the project site may be re-used for backfilling. However, the material must be stockpiled, and the required testing completed. The Contractor should complete gradation testing of samples taken from the stockpile. The respective MDOT material lab will confirm if the gradation of the onsite material meets the requirements for the desired backfill material. The material can be used only after acceptance by MDOT.

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MEASUREMENT, DOCUMENTATION & PAYMENT

Measurement and Payment

Refer to Subsection 403.04 of the Standard Specifications for Construction for direction regarding measurement and payment for drainage structures. In general, drainage structures are paid for by each unit installed for the required inside diameter. Excavation, dewatering, joint wrapping, and backfill are covered within the drainage structure item. Drainage structures include the cost for supplying a concrete footing and up to 8 feet in depth for the structure.

For manholes to be considered complete, a flow channel must be installed within the structure.

Some items, like additional depth for drainage structures over 8 feet deep or manhole risers, are paid by the foot of depth required.

Documentation

The primary report required for the payment of drainage structures, adjustments, and cleanout is the Daily Work Report (DWR). The Inspector should note in the remarks section of the report the condition of the base material during placement, material verification, and equipment and manpower used. The size of the structure placed and the invert elevations at all openings should be recorded for as-built records. The DWR should also note the following:

  1. Additional depth measured for payment on drainage structures.
  2. Final length of the lead cleaning and total quantity of structure cleaning.
  3. Once the work is completed:
    • Survey or other approved methods for verification construction conforms with the project documents.
    • Volume and tonnage of bedding and backfill material placed.

Form 1900, Aggregate Inspection Daily Report, will need to be completed for every sublot of aggregate to track gradation acceptance.

Form 0582B, Moisture & Density Determination - Nuclear Method, is used to record density testing results.

Delivery tickets must be verified for the source of material against the approved Material Source List. Each ticket must include the required information. Refer to Subsection 109.01.B.6 of the Standard Specifications for Construction for the information required on each ticket.

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LOCAL AGENCY PROJECTS

-Reserved-

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RAIL PROJECTS

-Reserved-

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