Published: April 21, 2021

All conduits not covered by the Bridge Inspection Manual will be covered by the Conduit Management Manual (CMM).

1. Procedures and Locations

A logical sequence for inspecting culvert and storm drains helps ensure that a thorough inspection will be conducted. In addition to the components, the inspector should also look for high water marks, changes in the drainage area, settlement of the roadway, and other indications of potential problems. In this regard, the inspection of a culvert or storm drain is like the inspection of a bridge.

For typical installations, it is usually convenient to begin the field inspection with general observations of the overall condition of the conduit and inspection of the approach roadway. The inspector should start at the outlet end and inspect the embankment, waterway, headwalls, wingwalls, and barrel. The inspector should then move to the inlet end. The following sequence is applicable to all culvert and storm drain inspections:

• Review available information and safety concerns
• Observe overall condition of the site
• Inspect approach roadway and embankment
• Inspect waterway
• Inspect end treatments
• Inspect barrel

General observations of the condition of the culvert or storm drain site should be made while approaching the area. The purpose of these initial observations is to familiarize the inspector with the conduit. They may also point out a need to modify the inspection sequence or indicate areas requiring special attention. The inspector should also be alert for changes in the drainage area that might affect runoff characteristics. It is recognized that accessibility, confined space issues, and traffic control present serious challenges to storm drain inspections.

Most defects are first detected by visual inspection. If possible, a close-up, hands-on inspection is preferred. The types of defects to look for when inspecting the barrel will depend upon the type of conduit being inspected. In general, barrels should be inspected for cross-sectional shape and barrel defects such as joint defects, seam defects, plate buckling, lateral shifting, differential movement, missing or loose bolts, corrosion, excessive abrasion, material defects, and localized construction damage.

Portions of conduits that are being supported or strengthened by temporary members will be rated based on their actual condition, i.e. the temporary members are not considered in the rating of the item.

The load carrying capacity will not be used in evaluating condition items. The fact that a culvert or storm drain was designed for less than current legal loads and may be posted will have no influence upon condition ratings.

2. Stationing and Orientation

Locations in sectional pipe can be referenced by using pipe joints as stations to establish the stationing of specific cross-sections. Stations should start with number 1 at the outlet and increase going upstream to the inlet. The location of points on a circular cross section can be referenced like hours on a clock. The clock should be oriented looking upstream. On structural plate corrugated metal conduits, points can be referenced to bolted circumferential and longitudinal seams.

3. Conduit Inspection Qualifications and Definitions

Conduit Inspector: The inspector is an individual with experience in culvert and storm drain design, installation, or maintenance activities. The inspector must complete the Conduit Inventory and Inspection Class. Only a Bridge Engineer is exempt from needing to take the Class.

Responsibilities:

• Perform Inventory, Routine, Interim and Storm drain Inspections
• Document the findings
• Report any immediate or emergency needs
• Log into the Collector App and submit Inventory(s) and Inspection(s) or sign and date the CR-86 and CR-87 forms.

Bridge Engineer: A Professional Engineer with extensive background in bridge, culvert, and storm drain design, repair, and maintenance. Example: District Bridge Engineer, Structures Engineer, etc. provide assistance and technical expertise to the Conduit Inspection Reviewer regarding structural issues.

Responsibilities:

• Conduct detailed inspections of conduits identified by others as having significant defects
• Perform load rating analyses when warranted
• Recommend appropriate measures to reduce or remove the cause of the defect

Bridge Inspector: A person qualified to inspect bridges in the state of Ohio per the Ohio Department of Transportation Bridge Inspection Manual.

4. Conduit Inspection Skills

Inspector must be capable of climbing, traversing slopes and crawling inside conduit barrels with diameters as small as 48 inches without difficulty. They must have the ability to print legibly and to read conduit plans, visualize details, draw technical sketches, and operate a camera. They must possess a mechanical aptitude and a working knowledge in the use of measuring devices such as rules, tapes, protractors, and calipers. The inspector must always have an awareness of potential hazards and exhibit a serious attitude toward safety precautions to be taken while entering and inspecting conduits. The inspector must approach each task sincerely and with the proper motivation since their judgment and thoroughness is relied upon to guarantee public safety and to protect public investment with respect to culverts and storm drains.

5. Conduit Inspection Equipment

The inspector should be equipped with a safety vest, hard hat, eye protection, gloves, high power flashlight(s), hip waders, pocket tape, 100 ft. tape, sounding rod, chipping hammer, calipers, micrometer, pH meter, camera, binoculars, magnifying glass, mirror, ladder, marking tools, gas detection equipment, safety harness, fall arrest tripod, safety line, etc.

Difficulty of access to any portion of the conduit should not prevent a thorough inspection. However, an inspector should not unnecessarily jeopardize their safety and should arrange for equipment and assistance as deemed necessary.

6. Remote Video Inspection

ODOT has remotely operated video inspection equipment available to aid in inspecting conduits where manned entry is not safe or possible. The equipment is operated and maintained by Districts 1, 4, 6, & 8. The equipment is available to all ODOT Districts upon request to one of the Districts listed above. The use of such camera equipment is an additional tool for assessing conduit condition. The rating system outlined in this manual will still be used to rate conduits inspected using the remote video inspection equipment.

7. Types of Inspections

With safety being a primary concern during inspection procedures, the inspector should consult Figure 1 Conduit Entry Class Flow Chart prior to entering a culvert or storm drain.

Based on the Entry Class criteria, many conduits will be a Class A. A Class A conduit inspection is performed without requiring entry of the conduit. A visual inspection of the conduit will be made from both ends.

Inventory Inspection: An Inventory Inspection is the first inspection of a culvert or storm drain when it becomes a part of the conduit inventory. Certain elements of an Inventory Inspection may also apply when there has been a modification to the conduit. Example: widening, lengthening, etc. The purpose of this inspection is twofold. First, an Inventory Inspection collects the data required to fill out the CR-87 Conduit Inventory Report. Second, the Inventory Inspection determines the baseline structural conditions by inspecting and recording the condition of the conduit on the CR-86 Conduit Inspection Report. When possible, a review of existing plans or historical data should be used to aid in performing the Inventory Inspection. It is during this inspection that any critical elements are noted for subsequent focus and assessments are made of other conditions that may later warrant special attention.

The Office of Hydraulic Engineering recommends taking four photos during your Inventory Inspection. Recall your Collector App training to ensure your photos are saved to the Inventory table of said CFN.

• Outlet end of conduit
• Outlet end picture of down stream
• Inlet end of conduit
• Inlet end picture of down stream

Routine Inspection: This is a regularly scheduled inspection consisting of enough observations and measurements to determine the physical and functional condition of the conduit. A Routine Inspection should identify any developing problems, changes in the Inventory data, changes in previously recorded conditions, and ensure that the conduit continues to satisfy present service requirements.

The Routine Inspection must fully satisfy the requirements of the Ohio Department of Transportation Conduit Management Manual with respect to inspection frequency, updating of the Inventory data, and the qualifications of the inspection personnel. When possible, these inspections are generally conducted up-close, hands-on for the entire conduit.

The results of a Routine Inspection are to be fully documented in the Collector App or on the CR-86 form along with any photographs taken during the inspection. Comments should note if there may be a need for maintenance, repair, or a need for an Interim Inspection.

The Office of Hydraulic Engineering recommends taking at least one photo during your Routine Inspection.

• Picture to show general condition of conduit (minimum)
• Additional photos as necessary to document poor condition location(s)

Damage Inspection: This is an unscheduled inspection to assess structural damage. The scope of the inspection must be for determining if there is a need for emergency load restrictions or closure of the conduit to traffic, and to assess the level of effort necessary to make a repair. The amount of effort expended on this type of inspection will vary significantly depending upon the extent of the damage. If major damage has occurred, inspectors must evaluate damaged elements, section loss, make measurements of misaligned sections, and check for any loss of foundation support.

If deemed necessary, a Bridge Engineer will perform a more detailed inspection. Proper documentation, verification of field measurement and calculations, and perhaps a more refined analysis to establish or adjust interim load restrictions are required follow-up procedures. An awareness of the potential for litigation must be exercised in the documentation of Damage Inspections.

The Office of Hydraulic Engineering recommends taking as many photos as necessary to document damage location(s).

Interim Inspections: This is an inspection scheduled at the discretion of the individual responsible for conduit inspection activities. An Interim Inspection is used for monitoring a known or suspected deficiency and can be performed by any qualified inspector familiar with the conduit. The individual performing an Interim Inspection must be carefully instructed regarding the nature of the known deficiency and its functional relationship to satisfactory conduit performance. In this circumstance, guidelines and procedures on what to observe or measure or both must be provided and a timely process to interpret the field results must be in place.
 
The determination of an appropriate Interim Inspection frequency should consider the severity of the known deficiency. Records should be kept of each visit to the conduit site for purposes of inspection, even when cursory in nature.

The Office of Hydraulic Engineering recommends taking at many photos as necessary to document poor condition location(s).

8. Frequency of Inspection

At a minimum, OHE requires the following inspection routine:

• Inspect all conduits with a span of 12 inches up to and including 48 inches prior to a roadway resurfacing or every 10 years.
• Inspect all conduits with a span greater than 48 inches but less than 120 inches every 5 years.
• Inspect all conduits that have a General Appraisal of 4 or less annually.

New and Rehabilitated Conduits:

Perform an Inventory Inspection for all newly installed or rehabilitated conduits within 30 days of work completion. For rehabilitated conduits, this will include modifying the inventory to reflect the modifications made to the conduit. In both cases, an inspection is to be performed to rate the structural condition of the conduit.

9. Critical Findings

Whenever the General Appraisal of a conduit is rated 2 or less the Inspector must immediately contact their District Bridge Engineer. The District Bridge Engineer will perform their own inspection and recommend restrictions, corrective actions, closure or a combination. Additionally, an E-mail, through an automated overnight script, will be sent to the District Bridge Engineer and TAM Coordinator.

Coding the Conduit Inspection on Collector App or CR-86 Form

Condition Rating Guidelines

Culverts and storm drains are to be inspected and rated according to these guidelines for the following inspection items. The items with a bold outline on the CR-86 Conduit Inspection Report will be used to determine the overall General Appraisal (GA) for the conduit. The General Appraisal will be the lowest of all of the bold box ratings on the CR- 86 form. Additionally, the GA will be auto populated by an overnight script so long as all relevant Inventory and Inspection items have been populated. Inspections performed with the Collector App. follow the same logic however there are no bold box indicators. Refer to CMM when necessary. Also note that Headwall and Scour may or may not dictate the GA. The Inspector must refer to the Headwall and Scour sections when making this determination. The inspector should use the comments section to note the location and description of any serious defects.

R - Item 1. Level of Inspection

Indicate the level of inspection used.

R - Item 2. Material

Material Rating is used to rate the general material condition of the conduit. Conduits are to be inspected for:

1. Deterioration to barrel material
2. Cracks
3. Dents and Localized Damage

If the conduit has been extended, code the worst condition of the most predominant material under the traveled lanes.

Deterioration – Abrasion and corrosion are the primary causes of deterioration.

Corrosion is the deterioration of metal due to electrochemical or chemical reactions. Conduits are subject to corrosion in certain aggressive environments.

Abrasion is the wearing a way of conduit materials by the erosive action of bedload carried in the stream. Abrasion is generally most serious in steep areas where high flow rates carry sand and rocks that wear away the conduit invert. Abrasion can also accelerate corrosion by wearing away protective coatings.
Corrosion and abrasion of conduits can be serious problems with adverse effects on structural performance. Damage due to corrosion and abrasion is a common cause for conduit replacement. The condition of the metal in corrugated metal conduits and any coatings, if used, should be considered when assigning a rating to the conduit barrel.
 
The inspection should include visual observations of metal corrosion and abrasion. As steel corrodes it expands considerably. Relatively shallow corrosion can produce thick deposits of scale. A geologist's pick-hammer can be used to scrape off heavy deposits of rust and scale permitting better observation of the metal. A hammer can also be used to locate unsound areas of exterior corrosion by striking the conduit wall with the pick end of the hammer. When severe corrosion is present, the pick will deform the wall or break through it. Protective coatings should be examined for abrasion damage, tearing, cracking, and removal. The inspector should document the extent & location of surface deterioration problems.
Metal conduits may be paved with concrete inverts. These paved concrete inverts are usually floating slabs used to carry water. Invert slabs provide protection against abrasion, corrosive conditions, erosion and undercutting, and are also used to improve hydraulic efficiency. Concrete inverts are used in circular, as well as other conduit shapes Concrete invert slabs should be checked for undermining and damage such as spalls, open cracks, and missing portions. The significance of the damage will depend upon its effect on the footings and corrugated metal.

Metal conduits may have a concrete pedestal with concrete Footings. The concrete material is to be evaluated using the rating scale for abutments. Longitudinal settlement effects will be rated under alignment and transverse movements will be rated under the shape factor.

Cracks - Cracking may occur in conduit materials and can indicate overloading resulting in small, localized, failures in shear, flexure, or simply damage during installation.

In metal conduits, cracking may occur along bolt holes of longitudinal seams and can be serious if allowed to progress. These cracks are most serious when accompanied by significant deflection, distortion, and other conditions indicative of backfill or soil problems.

In concrete conduits, reinforcing steel is designed to assume some of the imposed loads. Therefore, small hairline cracks, widths less than 1/8 inch, are expected and are not cause for alarm. The location of cracking in concrete conduits can indicate the type of problems being experienced. In concrete pipe, longitudinal cracks at the 3, 6, 9, and 12 o’clock positions indicate flexure cracking caused by poor side support. Longitudinal cracking in the invert at the 5 and 7 o’clock positions indicate shear cracking caused by poor haunch support. Likewise, cracking at the 11 and 1 o’clock positions may be the result of shear forces from above the conduit. Transverse cracks may also occur and are usually the result of non-uniform bedding or fill material causing point loads on the pipe.

• Hairline cracking: Small hairline cracks with widths less than 1/8 inch are common and are not cause for alarm. Look for moisture, leakage, and staining
• Scaling: Gradual but continuing loss of mortar and aggregate over an area due to the chemical breakdown of the cement bond.
• Delamination: Subsurface separation of concrete into layers.
• Efflorescence: A combination of calcium carbonate leached out of the cement paste and other recrystallized carbonate and chloride compounds.

Plastic pipe materials may experience splits. A split, rip, tear, or crack is any separation in the wall material other than at a designed joint.

For all conduit materials, any amount of cracking should be recorded, and the appropriate rating assigned from the rating condition tables.

Dents and Localized Damage - All conduits should be inspected for localized damage caused by construction procedures or from maintenance forces. For flexible pipe, wall damage such as dents, bulges, creases, cracks, and tears can be serious if the defects are extensive and can impair either the integrity of the barrel in ring compression or permit infiltration of backfill. Small, localized examples are not ordinarily critical. When the deformation type damages are critical, they will usually result in a poorly shaped cross section.

The inspector is to document the type, extent, and location of all significant wall damage defects. When examining dents in corrugated steel conduits, the opposite side of the plate should be checked, if possible, for cracking or debonding of the protective coating.

NOTE: The condition of the ends of the conduit do not govern the condition rating. The inspector will determine the general material condition rating based on the portion of the conduit which is underneath the influence of the roadway or which affects the roadway surface.

Material - Corrugated Metal Conduit or Casing

Material - Concrete Conduit or Clay

Material - Masonry Conduit

Material - Plastic Conduit

R - Item 3. Conduit Alignment

Conduits not on Footings: Used for the rating of precast segments, corrugated metal pipe that has been coupled or banded together, and plastic pipe. The alignment rating for the conduit is to account for irregularities longitudinally to the barrel. The conduit barrel is to be inspected for discontinuities and settlement between adjacent conduit segments.

Conduits on Footings: Concrete footing can be used in structural plate arches, long-span arches, and 3-sided box culverts. Metal footings are occasionally used for the arch and box conduit shapes. The “superstructure” depends on the footing to transmit the vertical load into the foundation. A metal plate arch is usually bolted in a base channel and is secured in the footing. Precast units are grouted into a keyway of the footing. Cast-in-place units may be poured continuously. Settlement may show up as severe cracking, spalling, or crushing across the footing at the critical spot, however, there may be deterioration of the concrete or masonry footings that is not related to settlement.

Definitions:

• Differential settlement – One section of the footing settles more than the rest of the footing.
• Rotational settlement- The footing starts to tip in either direction due to lateral forces or undermining.
• Uniform settlement- The whole footing settles and will not ordinarily affect flexible conduits.

Conduit alignment for Masonry conduits is to be rated for continuity between adjacent stones.

Conduit Alignment - Concrete, Corrugated Metal and Plastic Conduits

Conduit Alignment - Masonry Conduits

R - Item 4. Shape (Flexible Conduits Only)

The barrel of the conduit is to be inspected for evidence of flattening, buckling, bulging, out-of-roundness, and other signs that the shape is not equal to original design. The Shape rating is used for flexible conduits and left blank for rigid conduits. Shape is the most critical factor to consider when evaluating flexible conduits. Rigid conduits do not deflect appreciably before cracking or fracturing and therefore shape inspections are not performed. Defects in the conduit barrel for rigid conduits will be rated under other items.

The shape inspection should begin by approaching the conduit from the ends and sighting the sides and top. Also check for signs of pavement depression, guardrail movement, or gaps between headwalls and the pipe barrel. The cross-sectional shape of the conduit barrel should be observed and measured when inspecting flexible conduits. The shape rating for the conduit is to account for irregularities transverse to the conduit barrel.

Significant changes in shape since the last inspection should be carefully evaluated, even if the conduit is still in good condition. Dimensional checks should be made for suspect conduits, and these dimensions should be monitored over time. If there is instability of the backfill, the pipe will continue to change shape. A critical area for the inspection of long span metal conduits is at the 2 o’clock and 10 o’clock locations. An inward bulge at these locations may indicate potential failure of the conduit.

When distortion or curve flattening is apparent, the extent of the flattened area, in terms of arc length, length of conduit affected, and the location of the flattened area should be described in the inspection report. The length of the chord across the flattened area and the middle ordinate of the chord should be measured and recorded. The chord and middle ordinate measurements can be used to calculate the curvature of the flattened area using the formula shown in the appendix.

For conduit with shallow cover, the inspector shall make observations of the conduit with a few live loads passing over it. Discernible movement in the conduit may indicate possible instability and a need for more in-depth investigation.

The number of measurement locations depends upon the size and condition of the conduit. Long-span conduits should normally be measured at the end and at 25-foot intervals. Measurements may be required at more frequent intervals if significant shape changes are observed. The smaller pipe conduits can usually be measured at longer intervals than long- span conduits.

Hinging- Used to describe yielding of the material due to excessive bending moment in the pipe wall. Pipe wall exhibits a sharp crease pointed inward or outward. Hinges usually form at the 3 o’clock and 9 o’clock positions.

Arches
Arches are fixed on concrete footings, usually below or at the springline. The springline is the line connecting the outermost points on the sides of a conduit. This difference between pipes and arches means that an arch tends to deflect differently during the placement of backfill. Backfill forces tend to flatten the arch sides and peak its top because the springline cannot move inward like the wall of a round pipe. As a result, important shape factors to look for in an arch are flattened sides, peaked crown, and a flattened top arc.
 
Another important shape factor in arches is symmetry. If the arch was erected with the base channels not square to the centerline, it can cause a racking of the cross section. A racked cross-section is one that is not symmetrical about the centerline of the conduit. One side tends to flatten; the other side tends to curve more while the crown moves laterally and possibly upward. If these distortions are not corrected before backfilling the arch, they usually get worse as backfill is placed.

Arches in fair to good condition will have the following characteristics: A good shape appearance with smooth and symmetrical curvature, and a rise within three to four percent of design. Marginal condition would be indicated when the arch is significantly non- symmetrical, arch height is five to seven percent less than design, or arch height is five to seven percent greater than design, or when side or top plate flattening has occurred such that the plate radius is 50 to 100 percent greater than design. Arches in poor to critical condition will have a poor shape appearance with significant distortion and deflection, extremely non-symmetrical shape, severe flattening, radius more than 100 percent greater than design, of the sides or top plates, or a rise more than eight percent greater than the design rise or more than eight percent less than the design rise. Guidelines for measurements are given in the appendix.

Corrugated Metal Box Culverts
The key shape factor in a box culvert is the top arc. The design geometry is clearly very “flat” to begin with and therefore does not allow much room for deflection. The span at the top is also important and can only tolerate very minor increases.
The side plates often deflect slightly inward or outward. Generally, an inward deflection would be the more critical as an outward movement would be restrained by soil.
Shape factors to be checked visually include flattening of the top arc, outward movement of sides, or inward deflection of the sides. The inspector should note the visual appearance of the shape and should measure and record the rise and the horizontal span at the top of the straight legs. If the rise is more than 1 ½ percent of the design rise or less than 1 ½ percent of the design rise, the curvature of the large top radius should be checked. Guidelines for measurements are given in the appendix.

Plastic Pipe
There are several definitions that are unique to describing shape defects in plastic pipe.

• Deflection - A deviation from the original design shape without the formation of sharp peaks or valleys.
• Buckling - A bend, warp or crumpling. The following are forms of buckling:
• Hinging - Used to describe yielding of the material due to excessive bending moment in the pipe wall. Pipe wall exhibits a sharp crease pointed inward or outward. Hinges usually form at the 3 o’clock and 9 o’clock positions.
• Wall Crushing - Used to describe yielding in the wall produced by excessive compressive stresses. Pipe wall exhibits a wrinkled effect.
• Dimpling - Used to describe a wavy or waffling pattern that occurs in the inner wall of the pipe due to local instability

Shape - Corrugated Metal Conduits

Shape - Plastic Pipe Conduits

R - Item 5. Seams or Joints

Key factors to look for in the inspection of seams and joints are indications of backfill infiltration and water exfiltration. Excessive seepage through an open joint can cause soil infiltration or erosion of the surrounding backfill material reducing lateral support. Inspection will require a flashlight. Open joints may be probed with a small rod or flat rule to check for voids. Joint defects shall be recorded with locations indicated on the Conduit Inspection Report.

Joint defects may include:

1. Open joints
2. Seepage at the joints
3. Surface sinkholes over the conduit

Seepage along the outside of the conduit barrel may remove supporting material. This process is referred to as “piping”, since a hollow cavity similar to a pipe is often formed. Piping can also occur through open joints. Piping is controlled by reducing the amount and velocity of water seeping along the outside of the conduit barrel. This may require watertight joints and, in some cases, anti-seep collars. Good backfill material and adequate compaction of that material are also important.

Corrugated Metal Structural Multi-Plate Conduit

All bolted splice seams should be checked for loose, missing or severely corroded bolts, cusping at overlap, and tears or cracks in metal at the bolt lines.

Circumferential Seams - The circumferential seams in helical pipe, like joints in factory pipe, do not carry ring compression thrust in the pipe. They do make the conduit one continuous conduit. Distress in these seams is rare and will ordinarily be the result of a severe differential deflection or distortion problem or some other manifestation of soil failure. For example, a steep sloping conduit through an embankment may be pulled apart longitudinally if the embankment moves down. Plates should be installed with the upstream plate overlapping the downstream plate to provide a “shingle” effect in the circumferential seam. Seam distress is important to note during inspections since it would indicate a basic problem of stability in the fill. Circumferential seam distress can also be a result of foundation failure, but in such cases should be clear by the vertical alignment.

Longitudinal Seam Defects in Structural Plate Conduits - Longitudinal seams should be visually inspected for open seams, cracking at bolt holes, plate distortion around the bolts, bolt tipping, cocked seams, cusped seams, and for significant metal loss in the fasteners due to corrosion. In riveted or spot-welded pipes, the seams are longitudinal and carry the full ring compression in the pipe. These seams must be sound and capable of handling high compression forces. When inspecting the longitudinal seams of bituminous-coated corrugated metal conduits, cracking in the bituminous coating may indicate seam separation.
 
Seam Defects in Structural Plate Conduits:

1. Loose Fasteners - Seams should be checked for loose or missing fasteners. For steel conduits the longitudinal seams are bolted together with high-strength bolts in two rows; one row in the crests and one row in the valleys of the corrugations. These are bearing type connections and are not dependent on a minimum clamping force of bolt tension to develop interface friction between the plates. Fasteners in steel structural plate may be checked for tightness by tapping lightly with a hammer and checking for movement. For aluminum structural plate, the longitudinal seams are bolted together with normal strength bolts in two rows with bolts in the crests and valleys of both rows. These seams function as bearing connections, utilizing bearing of the bolts on the edges of holes and friction between the plates.
2. Misaligned and Cusped Seams - The longitudinal seams of structural plate are the principal difference from factory pipe. The shape and curvature of the conduit is affected by the lapped bolted longitudinal seam. Improper erection or fabrication can result in misaligned or cusped seams. Slight cases of these conditions are common and frequently not significant. However, severe cases can result in failure of the seam or conduit. When a cusped seam is significant the conduit's shape appearance and key dimensions will differ significantly from the design shape and dimensions. The cusp effect should cause the conduit to receive very low ratings on the shape inspection if it is a serious problem. A cusped seam can result in loss of backfill and may reduce the ultimate ring compression strength of the conduit.
3. Seam Cracking - Cracking along the bolt holes of longitudinal seams can be serious if allowed to progress. As cracking progresses, the plate may be completely severed, and the ring compression capability of the seam lost. This could result in deformation or possible failure of the conduit. Longitudinal cracks are most serious when accompanied by significant deflection, distortion, and other conditions indicative of backfill or soil problems. Longitudinal cracks are caused by excessive bending strain, usually the result of deflection. Cracking may occasionally be caused by improper erection practices such as using bolting force to “lay down” a badly cocked seam.
4. Bolt Tipping - The bolted seams in structural plate conduits only develop their ultimate strength under compression. Bolt tipping occurs when the plates slip. As the plates begin to slip, the bolts tip, and the bolt holes are plastically elongated by the bolt shank. High compressive stress is required to cause bolt tipping. Conduits have rarely been designed with loads high enough to produce a ring compression that will cause bolt tip. However, seams should be examined for bolt tip particularly in conduits under higher fills. Excessive compression on a seam could result in plate deformations around the tipped bolts and failure is reached when the bolts are eventually pulled through the plates.

Corrugated Metal, Concrete, and Plastic Pipe
Joints are rated for factory pipe and serve to maintain the water conveyance of the conduit from section to section, to keep the pipe sections in alignment, keep the backfill soil from infiltrating, and to help prevent sections from pulling apart.

Masonry Conduits
Joints are rated for masonry conduits for mortar cracks, water exfiltration, backfill infiltration, vegetation in the cracks, and misalignment due to lack of mortar.

Seams or Joints - Corrugated Metal/Multi-plate

NOTE: Write in the comments section the size of the cusps, gaps, and the number and length of cracks.

Seams or Joints - Concrete, Plastic Pipe, and Masonry Conduits

R - Item 6. Slab

This item is for slab top culverts only. Do not use for precast 3 or 4 sided conduits.

The slab is the primary load-carrying member and should be inspected top and bottom for evidence of leakage, deterioration and structural adequacy. The edge of the slab, approximately the first 12 inches, will not govern the condition rating.

Visually inspect the concrete deck for cracks, spalls, and other defects. Hammers and chain drags can be used to detect areas of delamination. A delaminated area will have a distinctive hollow “clacking” sound when tapped with a hammer or revealed with a chain drag. A hammer hitting sound concrete will result in a solid “pinging” type sound.

Documentation should be placed on the form stating if the reinforcing steel bars are exposed on all surfaces. Note length, number of bars exposed, and location.

Common concrete deck defects may include:

• Cracking
• Scaling – the gradual disintegration of a concrete surface due to the failure of the cement paste caused by chemical attack or freeze/thaw cycles
• Delamination – subsurface separation of concrete into layers
• Spalling – depressions in concrete caused by a separation of a portion of the surface concrete, revealing a fracture parallel with or slightly inclined to the surface
• Efflorescence – deposits on concrete or brick caused by crystallization of carbonates brought to the surface by moisture in the masonry or concrete
• Honeycombs – areas in concrete where mortar has separated and left spaces between the coarse aggregate, usually caused by improper vibration during concrete construction
• Pop-outs – conical fragments broken out of a concrete surface by pressure from reactive aggregate particles
• Wear
• Collision damage
• Abrasion – wearing or grinding away of material by friction; usually caused by sand, gravel, or stones carried by wind or water
• Steel Reinforcing corrosion – the general disintegration of metal through oxidation

Slab

R - Item 7. Abutments

This item is for slab top culverts, Conduit Shape Code 8, only. Do not use for precast 3 or 4 sided conduits.

An abutment is a substructure unit located at the ends of a bridge or slab culvert. Its function is to provide end support for the bridge and to retain the approach embankment. Wingwalls are also located at the ends of a bridge or culvert. Their function is only to retain the approach embankment and not to provide end support for the bridge. Wingwalls are considered part of the abutment component only if they are integral with the abutment. When there is an expansion joint or construction joint between the abutment and the wingwall, that wingwall is defined as an independent wingwall and not considered in the evaluation of the abutment component. The wingwall will be rated under Item 8. Headwalls.,

Inspection procedures for abutments involve examining material deterioration and settlement. However, because stability is a paramount concern, checking for various forms of movement are required.

The most common problems observed during the inspection of abutments are:

• Vertical movement
• Lateral movement
• Rotational movement
• Material defects
• Scour of the foundation
• Drainage system malfunction

Abutment - Concrete

Abutment - Masonry

R - Item 8. Headwalls

Headwalls, endwalls, and wingwalls are designed to retain the embankment, prevent water from undermining the conduit ends, prevent piping around the conduit, and improve the hydraulic capacity of the conduit.

The inlets and outlets ends of a conduit may require protection to withstand the hydraulic forces exerted during peak flows. Inlet ends of flexible pipe conduits, which are not adequately protected or anchored, may be subject to entrance failures due to buoyant forces. The outlet may require energy dissipaters to control erosion and scour and to protect downstream properties. High outlet velocities may cause scour which undermines the endwall, wingwalls, and conduit barrel. This erosion can cause end-section drop-off in rigid sectional pipe conduits.

Seepage along the outside of the conduit barrel may remove supporting material. This process is referred to as “piping”, since a hollow cavity similar to a pipe is often formed.

All headwalls, endwalls, and wingwalls are checked for deterioration, settlement, undercutting and signs of failure. End treatments should be inspected like any other structural component. Their effectiveness can directly affect the performance of the conduit.

Check for evidence of scour or undermining around footings and at the inlet and outlet of the conduit.

Stone end treatment types use wingwalls to retain the embankment around the conduit opening. Check stone masonry piers for mortar cracks, water and vegetation in the cracks, and for spalled, split, loose, or missing stones. Wingwalls should be inspected to ensure they are in proper vertical alignment. Wingwalls may be tilted due to settlement, slides, or scour. Refer to the abutment section for rating guidelines for masonry wingwalls.

The most common types of end treatments for conduits are:

• Concrete wall type (half or full height)
• Projections
• Mitered
• Pipe end section

Projections - The inspector should indicate the location and extent of any undercutting around the ends of the barrel. The depth of any scouring should be measured with a probing rod. In low flow conditions, scour holes have a tendency to fill up with debris or sediment. If no probing rod is used, an inspector could mistakenly report less scour than has taken place.

Mitered Ends - Inspection items for mitered ends are the same as for projecting ends. Additional care should be taken to measure any deformation of the end. Mitering the end of corrugated pipe conduit reduces its structural capacity.

Pipe End Sections - These are typically used on relatively small conduits. For inspection purposes, treat the pipe end section as you would a projected end.

The inspection locations and procedures for most wingwalls are similar to those listed in the abutment section. Many of the problems that occur in abutments are also common in wingwalls, including:

• Vertical movement
• Material Defects
• Lateral movement
• Scour
• Rotational movement
• Drainage Systems

NOTE: This item is only considered a bold box on the CR-86 form if the structure is determined to be headwall critical based Inventory Items 29 through 32 and Figure 5 Headwall Critical or the judgment of the inspector. A full-height headwall or integral wingwall that is located close to the edge of the roadway and is acting to retain the roadway embankment such that a failure would cause immediate collapse of the paved surface should govern the General Appraisal for the conduit. In contrast, a non-integral, separated from the headwall by an expansion joint or construction joint that is further from the edge of the roadway is not as important to the stability of the conduit, so its condition should not govern the General Appraisal.

Headwalls

R - Item 9. End Conduit

End Conduits include catch basins, inlets, manholes, junction chambers, or other conduits that may occur at the end of a storm drain. Headwalls are not included under this item and should be rated under Item 8. These conduits should be examined for their structural condition, connection with the conduit, and their ability to convey water.

End Structures

Channel

This item describes the physical conditions associated with the flow of water both through the conduit and in the channel immediately upstream and downstream of the conduit. Inspection items such as stream stability and the condition of the channel, riprap, and slope protection will be rated. Be particularly concerned with visible signs of excessive water velocity, which may cause the undermining of slope protection or footings, erosion of banks, and realignment of the stream, which may result in immediate or potential problems. Accumulation of drift and debris on the superstructure and substructure should be noted on the inspection form and included in the condition rating.

R - Item 10. Channel Alignment

The channel should align with and cause the stream to flow through the center of the conduit. The channel alignment inspection is intended to note changes in the channel that cause the flow or channel to shift over time. The conduit may have more than one channel flowing to the inlet. Example: ditches alongside the roadway. The channel alignment will be governed by worst case.

The channel alignment is not to be rated down if the alignment was designed to be at severe angles. If the channel is designed for severe angles and the conduit is showing signs of distress, then the appropriate item should reflect this.

Channel Alignment

R - Item 11. Channel Protection

The method, if any, used to protect the channel banks from scour and other degradation caused by the stream action. Note and rate the condition of all channel protection.

Channel Protection

R - Item 12. Conduit Waterway Blockage

Contraction scour and stream bed degradation can be increased due to inadequate waterway area. The geometry of the conduit barrel, the amount of debris carried by the channel during high water periods, and the adequacy of freeboard should be considered in determining waterway adequacy. Check for scour of the stream bed and banks, the formation of sandbars or debris which could change the direction of flow, or other obstructions which could influence the adequacy of the waterway opening. Accumulation of drift and debris at the orifice of the conduit should be noted on the inspection form and included in the condition rating.

Some conduits installed in recent years were intentionally placed below the normal streambed elevation. This is done to promote the formation of a natural stream bottom through the conduit barrel and is required in some streams for migratory fish species. The burial of the invert should be noted in the construction plans on the conduit detail sheets. When inspecting such conduits, the Conduit Waterway Blockage rating should not be down rated if the conduit was originally designed with a buried invert.

Conduit Waterway Blockage

R - Item 13. Scour

The removal of a streambed or bank area by stream flow is called scour. If not addressed, scour can lead to the undermining of footings, headwalls, and conduit end sections through the continual removal of supporting material. Eventually, serious structural problems such as piping and the rotation of footings can take place as additional supporting material is removed. The inspector should indicate the location and extent of any undercutting around footings, headwalls, wingwalls, and the end sections of the conduit. Scour holes can eventually cause cantilevered pipe end sections to detach and collapse or bend down, restricting stream flow. The depth of any scouring should be measured with a probing rod. In low flow conditions, scour holes tend to fill up with debris or sediment.

Conduits supported by footings, such as 3-sided box culverts and arches without an invert slab are scour critical conduits. Check for evidence of scour and undermining of the footings and for indication of footing rotation.

NOTE: This item is only considered a bold box on the CR-86 form if it is a scour critical structure. Conduits supported by footings, 3 sided boxes, arches, and short span structures, are scour critical and therefore a bold box on the CR-86. Generally, the scour rating of conduits not supported by footings should not govern the General Appraisal of the conduit unless a threat to the roadway exists. This should be determined based upon the judgment of the inspector.

Scour

Approaches

A smooth transition is important for the reduction of impact forces acting upon the conduit and for safe driving conditions. The inspector is to note any difference in elevation between pavement over and around the conduit area. The inspector should also make note and report any concerns relating to the following:

1. Roadway alignment
2. Presence of an adequate shoulder profile
3. Safety features

Defects in the approach pavement, guardrail, and embankment may be indicators of possible structural or hydraulic problems in the conduit. The approach pavement, guardrail, and embankment should be inspected for the following conditions:

1. Sag in roadway or guardrail
2. Cracks in pavement
3. Pavement patches or evidence that roadway has settled
4. Erosion or failure of side slopes

Approach roadways should be examined for sudden dips, cracks, and sags in the pavement. These usually indicate excessive deflection of the conduit or inadequate compaction of the backfill material. New pavement can temporarily hide approach problems. It is advisable for the inspector to have previous inspection reports that may indicate the age of the present overlay.

It is important to note that not all defects in the approach roadway are necessarily due to structural or hydraulic issues in the conduit. For Example, deterioration of the pavement may be due to excessive traffic and no other reason. The inspector should keep in mind that the purpose of rating the approach items to is to look for indicators of problems in the conduit below, not to rate the approach conditions due to issues unrelated to conduit inspection.

R - Item 14. Pavement

Rate the condition of the pavement within 50 feet of the conduit.

Pavement

R - Item 15. Guardrail

The inspector should look for any sag, rotation, or misalignment of the guardrail, within 50 feet of the conduit, that may indicate settlement or an embankment slip. The purpose of guardrail inspection is to look for indication of potential problems with the conduit below, not to rate the material condition of the guardrail itself.

Guardrail

R - Item 16. Embankment

The general condition of the approach embankment, up to 50 feet away from conduit, is to be inspected for indications of settlement, bulging, erosion from stream scour, and saturation from entrapped water due to poor drainage.

The embankment around the conduit entrance and exit should be inspected for slide failures. Check for debris at the inlet and outlet and within the conduit.

Embankment

General Appraisal and Operational Status

This is a two-part item. The first box is for coding the general overall condition of the conduit. The second box is for coding the operational status of the conduit.

C - General Appraisal (GA)

The General Appraisal (GA) will be auto populated by an overnight script so long as all relevant Inventory and Inspection items have been populated. Headwall and Scour may or may not dictate the GA. The Inspector must refer to the Headwall and Scour sections when making this determination.

R - Operational Status

O - Comments

A comments section is provided for the inspector to note any details regarding the inspection. The inspector should note the location and severity of specific defects here. This section should also be used to briefly explain any judgment used on the part of the inspector when assigning ratings. If more room is needed, the back of the form may be used to record notes.

C - Inspected By & Inspection Date

The Conduit Inspector is to sign and date the Inspection report (CR-86). The Conduit Inspector will also type or print their name directly under their signature. When utilizing the Collector App, your login will be your signature and when you submit your record it will be date and time stamped.

Note: The Conduit Inspector must meet the qualifications listed at the beginning of section: III Conduit Inspection; 3. Conduit Inspection Qualifications and Definitions.