Guideline for Culvert Safety Management

Appendix - Guideline for Culvert Safety Management with Clarification Comments on Grey Background

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Appendix - Guideline for Culvert Safety Management with Clarification Comments on Grey Background - January 2012

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Section Analysis 0.2 - Scope 

This Guideline outlines the minimum components to be included in a CSMP.

Section Analysis 0.4 - Responsibility

The responsibility for safe railway operations over any culvert lies with the railway authority. The railway authority is responsible for complying with the Scope of this Guideline, Part A - General. If a culvert supports tracks owned by two or more railway companies, then the railway companies are jointly responsible for compliance with this part.

If during a visual inspection there is a situation noted that could impact safe railway operations, the railway authority is to notify the party responsible and ensure that effective remedial action has been carried out. If required, TC can be notified as well of the safety issue in order to help facilitate a resolution to the issue, particularly in the event when one of the parties fails to recognize their responsibilities.

Section Analysis 1.1 - Safety Management Systems

When a railway company is not the railway authority for the track over which it operates, that railway company must implement and maintain a system to ensure that the railway authority, over who's track they operate, demonstrates conformance with its CSMP and that safe railway operations are maintained with respect to culverts. This may include, but not be limited to, a review of the railway authority's internal safety audit for culverts.

Section Analysis 2.3 - Railway Engineer

A Railway Engineer is responsible for the development of all inspection procedures, reviews inspection reports, and determines whether culverts are being inspected according to the applicable procedures and frequency, and reviews any items noted by an inspector as required. He/she shall also take responsibility for design, construction, evaluation or alteration work and procedures to be followed in association with a railway work that affects safety of culverts.

Section Analysis 2.4 - Culvert Inspector

This section proposes the qualifications that a Culvert Inspector should meet. Effective inspection of culverts is essential to preserving their integrity and serviceability. Culvert Inspectors must be able to understand and follow the inspection procedure, including accessing inspection points on a culvert, measuring components and any changes, describing conditions found in a standard, unambiguous manner, and detecting the development of conditions that are critical to the safety of the culvert. Culvert Inspectors should have a good understanding of how each type of culverts (i.e. rigid culverts e.g. concrete or steel pipes and flexible culverts e.g. corrugated steel pipes, plastic pipes such as PVC, etc.) function hydraulically and structurally. It is essential that a Culvert Inspector who detects a potential hazard to the safe railway operations should be authorized by the railway authority to place appropriate restrictions on the operation of traffic pending review as necessary by a Railway Engineer. A Railway Engineer should ensure that there is a process in place, which may include audits, field trips and training of a Culvert Inspector, to assure the quality of the inspections reported.

Section Analysis 2.5 - Designation of Individuals

This section proposes that each railway authority designate class of individuals as qualified Railway Engineers and Culvert Inspectors, and provide a recorded basis for each designation in effect. The railway authority should record designations of each class of individuals, whether employees, consultants or contractors. If a consultant or contractor has several individuals performing the described functions under a contract or other engagement, then one or more individuals should be designated as being responsible to the railway authority for the work performed under that engagement, with the others working under the responsible charge of that individual.

Section Analysis 3.2 and 3.3 - Design and Installation of New Culverts and Replacement and Repair of Existing Culverts

This section is not intended to be all-inclusive. The intent of this section is to highlight the important of design and installation of new or replacement culverts. Railway companies should consult manufacturer's installation instructions pertaining to their individual products. Additionally, industry standards or guidelines, such as AREMA, are available to assist railway companies in the design and installation of culverts.

Culverts are primarily constructed to convey water through a railway or other embankment. A culvert that does not perform this function properly may jeopardise safe railway operations, cause excessive property damage, or even loss of life. The hydraulic requirements of a culvert usually determine the size, shape, slope, inlet and outlet treatments of a culvert. Culvert hydraulics can be divided into two general design elements. The first is a hydrological analysis to determine the design discharge or the amount of runoff the culvert should be designed to convey. The second is a hydraulic analysis to select a culvert, or evaluate whether an existing culvert is capable of adequately conveying the design discharge.

Good quality backfill material, proper placement technique and adequate compaction are of critical importance when installing a culvert. It is imperative that the culvert installation crew is knowledgeable and skilful of sound culvert installation techniques and equipped with proper material(s) and equipment(s). It is important that railway companies provide proper training to their culvert installation crew.

Section Analysis 4.1 - Scope

Types of inspections include but are not limited to visual, detailed, scour, hydraulic, underwater, special, etc.

Section Analysis 4.3 - Scheduling of Culvert Inspections

a. The railway authority should conduct regular comprehensive structural inspections of each culvert at least once every five years, and maintain records of those inspections that include the date on which the inspection was performed, the precise identification of the culvert inspected, the items inspected, an accurate description of the condition of those items, and a narrative of any inspection item that is found by an inspector to be a potential problem.

A culvert should be inspected more frequently than the period referenced in paragraph above when a Railway Engineer or his designate determines that such is necessary. The responsibility for adequate inspection remains with the railway authority, with the conditions prescribed by a Railway Engineer. The inspection regime for every culvert should be determined from its condition, configuration, environment and traffic levels.

b. Any culvert that has not been in railway service and has not been inspected in accordance with this section should be inspected and the inspection report reviewed by a Railway Engineer prior to the resumption of railway service. The inspection frequency requirements of paragraph a. do not apply to culverts that are not in service, but that does not relieve a railway authority from responsibility for any damage to outside parties that might be caused by the condition of a culvert.

Section Analysis 4.4 - Culvert Inspection Procedures

Each railway authority's CSMP should specify the procedure to be used for inspection of different sizes and types of culverts, including safe work procedures for inspection personnel (i.e. confined space, etc.). A Railway Engineer or his designate should specify the culvert inspection procedures. The culvert inspection procedures should provide reasonable assurance that the level of detail is appropriate for the size and configuration of the culvert. Additionally, the culvert inspection procedures should be designed to detect, report, and protect deterioration and deficiencies before they present a hazard to safe railway operations. The responsibility for adequate inspection remains with the railway authority, with the conditions prescribed by a Railway Engineer or his designate.

Section Analysis 4.5 - Special Inspections

It is essential that traffic be protected from possible culvert failure caused by damage from an unusual event. The railway authority should have in place a means to receive notice of such an event and a procedure to conduct an inspection following such an event.

A Railway Engineer may be required to supplement his/her competencies with outside expertise to provide for a reasonable level of culvert safety, (e.g. geotechnical, hydraulic, hydrological or underwater inspection).

Section Analysis 4.6 - Submerged Culverts

Each railway authority's CSMP should provide for the detection of deterioration of culvert components that are submerged or subject to water flow. The condition of culvert components located under water is usually not evident from above. A means to determine their condition might be as simple as using a measuring rod, or might call for periodic or special diving inspections. Advanced technology might also provide devices that can be used to determine underwater conditions.

It is recognized that not all culverts require an underwater inspection. The intent in this section is that if a culvert is deemed by a Railway Engineer to be susceptible to conditions that will require underwater inspections, provisions and procedures should be put in place to satisfy this section of the Guideline.

Where underwater inspection equipment is ineffective due to murky water conditions, a Railway Engineer may consider a diving inspection for a larger diameter culvert to determine its condition. For smaller diameter culverts the railway authority could monitor the track and embankment on an ongoing basis and look for any signs of culvert failure as soon as it occurs. This monitoring should also include a yearly documented inspection.

Section Analysis 4.8 - Culvert Inspection Records

a. Each railway authority to which this part applies should keep a record of each inspection that is performed on those culverts under this part.

b. A culvert inspection has little value unless it is recorded and reported to the individuals who are responsible for the ultimate determination of the safety of the culvert. Culvert Inspectors may use a variety of methods to record their findings as they move about the culvert. These include, but are not limited to, notebooks, voice recordings, having another individual transcribe notes, and photographs. These notes and other items are usually compiled into a prescribed report form at the end of the day or at the conclusion of the inspection.

c. Delineates the essential elements that should be addressed and reported in any culvert inspection report.

Section Analysis 4.9 - Review of Culvert Inspection Reports

A Railway Engineer or his designate should review inspection reports and determine whether culverts are being inspected according to the applicable procedures and frequencies, and review any items noted by a Culvert Inspector as exceptions.

Section Analysis 4.10 - Culvert Hazard Identification and Risk Assessment

Safety issues and concerns associated with culverts include, but are not limited to:

a. Waterway adequacy;

The stream channel and drainage area should be evaluated for the following:

  1. Changes in stream channel alignment, which may reduce hydraulic capacity or cause scour. A change in the direction of flow or its velocity can contribute to failures of a culvert. Wing walls and barrels can break off due to settlement caused by scour.
  2. Changes in upstream land use such as clearing, deforestation, significant construction and new development, channel improvements and removal of dams may change the peak flow rates and stream stability. Similarly, obstructions downstream from a culvert that back water up to the culvert may also affect the performance of the culvert or cause saturation of the road bed.
  3. Excessive bank erosion, stream channel aggradation/degradation may be indicative of a change in water flow.
  4. A high water marks indicate that a culvert may be inadequately sized, which increases the potential for flooding damage or track flooding. Culverts should be checked during or immediately after peak flows -to determine whether water has ponded, adjoining properties are flooded, or the track is flooded.'
  5. Water should flow in and out of a culvert smoothly and without interference or obstruction. Channel obstructions such as deposits of debris, ballast, driftwood, mudslides, beaver dams, and organic growth, affects the hydraulic capacity of a culvert.

If any of the above condition exists railway authority should perform hydrological and hydraulic analysis to determine if a culvert is adequately sized.

b. Slope stability/Ground Hazardous;

This inspection should be conducted by a geotechnical engineer to identify, assess and monitor ground hazards. Ground hazards include but not limited to landslides, subsidence, snow and ice conditions as well as hydraulic erosion hazards. Frequency and locations to be inspected is dependent on the current conditions and the assessed likelihood and severity of the ground hazard. If conditions warrant, helicopter inspections should be conducted to inspect and assess potential hazards such as but not limited to rock falls, debris flows, earth flows, avulsions (shifted streams) and river erosion hazards. Railway authority should take appropriate action as directed by the geotechnical engineer if emergent conditions are identified; immediate action should be taken to mitigate the threat.

c. Beaver activity;

Railway authorities should implement a beaver control program where warranted to mitigate hazards imposed by beaver activity. Beaver dams located upstream and downstream from the track, in streams that flow under or near the track represent a potential hazard. The primary hazard caused by beaver activity is washouts. It also results in gullying or seepage erosion of the railway grade. Railway authorities should regularly inspect for beaver dams and take appropriate actions if conditions are hazardous. An aerial survey of beaver dams may be required in the spring and fall of each year to support ground inspections.

d. Debris and sediment blocking culverts;

It is essential that the culvert be able to handle the design flow. If the culvert is blocked with deposits of debris, driftwood, organic growth (including beaver dams) or sediment, the culvert may be inadequate to handle design flows. This may result in excessive ponding, flooding of nearby properties, and washouts of track and embankment. Accumulations of debris sediment in the stream may cause scour of the stream banks and embankments, or could cause changes in the channel alignment. Thus it is imperative that railway authorities remove deposits of debris and sediment blockings if it poses a threat to safe railway operations and property.

e. Snow and ice conditions blocking culverts;

Similarly snow and ice can prevent proper drainage by blocking a culvert and impeding flow. Railway authorities should take appropriate actions when such conditions warrant to protect safe railway operations.

f. High water condition;

Areas subjected to frequent or historic conditions of high or rapidly moving water, such as flash floods, may be protected with detection devices to sense the rise or velocity of water in or near culverts, which may be inadequate to carry the total storm runoff. The track bed may be washed away or flooded and in such cases significant damage could occur. When such conditions are imminent, washout protection devices would provide sufficient warning to stop all nearby trains.

Similar in nature to washout protection is the high water detection device, which detects the rate-of-rise and absolute level of water around particularly vulnerable locations such as culverts, which could face inundation by rapid storm runoff conditions. Conventional rain gages could also be utilized to provide early warning of impending high water conditions.

g. Severe weather conditions;

Railway authorities should monitor weather conditions and weather warnings and follow-up with special patrols for culvert inspections, including drainage assessments for the specific warning areas. Weather monitoring is an effective way to plan for any adverse situation.

Railway authorities should remain vigilant of events, including but not limited to heavy precipitation, spring runoff, high river levels and/or higher than normal flow conditions, etc. When such conditions exist, inspections should be performed and appropriate measures taken before and after the event to protect safe railway operations. Culverts should be re-evaluated to confirm both structural integrity and the ability to effectively accommodate water flow under the track.

h. Highly corrosive and abrasive environments;

Water and soil related corrosion and abrasion are the two main forms of deterioration experienced by culvert materials.

Certain soil and water conditions have a strong relationship to accelerated culvert deterioration. Metal culverts are subject to corrosion in certain aggressive environments. The pH and electrical resistivity of soil and water provide an indication of the likelihood of corrosion. Railway authorities should establish guidelines in terms of pH and resistivity that are based on local conditions and performance.

Abrasion may remove any protective coating on the metal, exposing the core material to chemical and further abrasive attack. Corrosion forces may perforate the pipe from either the water or soil side, weakening its structural capacity. Also, exfiltration or infiltration of material and water through these holes may create voids around the culvert pipe, undermining the supporting backfill material and further weakening its structural integrity.

The effects of water-side abrasion and corrosion are easy to assess (since they are visible); however, soil side corrosion is not as apparent (since they are not visible - corroded fasteners, or rust emanating from the seams may indicate soil side corrosion). Corrosion and abrasion of corrugated metal culverts can be a serious problem with adverse effects on structural performance. Railway authorities should be cognisant of aggressive environment and should have a plan in place to monitor, address, and implement special inspection methods in those environments.

i. Buried culverts (culverts "not found" but exist on Railway Company's inventory);

Culvert Inspectors should report any inventoried culverts they are unable to locate and report these locations to the Railway Engineer. A Railway Engineer is responsible for determining the effect this may have on drainage in the area and safe railway operations.

Culverts that are not found may result in inadequate drainage or culvert failure, which could impact safe railway operations. Railway authorities should make every effort to locate such culverts and update their inventory.

j. Deferred work;

A Railway Engineer should perform an evaluation and risk analysis prior to deferring any culvert work.

k. Inadequate culvert length.

Culvert extension may be required as a result of proposed bank widening, stream deepening, track lift, etc.

Section Analysis 6.2 - Audits, General

To verify the effectiveness of a CSMP, it is necessary to have processes for, and conduct, internal audit.

Internal audit should include:

  1. Each railway authority's CSMP should incorporate provisions for an inspection audit to determine whether the inspection provisions of the program are being followed, and whether the program itself is effectively providing for the continued safety of the subject culverts.
  2. The inspection audit should include an evaluation of a representative sampling of culvert inspection reports and determine whether the reports accurately describe the conditions of the culvert inspected.

Section Analysis 6.3 - Documents and Data Management

Each railway authority should keep records (standards, procedures, drawings, inspection reports, evaluations, etc.) under this part and make those documents and records available for inspection and reproduction upon request. Access to the documents and records of the CSMP is required for carrying out regulatory oversight.