CSI: Engineers

Curtis Edwards, P.E.
Vice President
Pountney Psomas
San Diego, California

A water pipeline ruptures; the resulting sinkhole causes a street collapse in the middle of a major urban thoroughfare. Firefighters, paramedics and police are immediately on the scene to secure the site and ensure public safety.

Another set of first responders consists of public works professionals as well as management, operations and maintenance personnel from a myriad of stakeholders. They are challenged with securing the damaged infrastructure, routing traffic, and minimizing further damage to their own facilities and adjacent property. In addition to site safety, they can be responsible for everything from water quality and erosion control in the event of a water main break, to control of sewage discharge into natural waterways in the event of a sewage spill.

Understandably, operations and maintenance personnel are highly motivated to immediately remove the damage and begin repairs ASAP to get the infrastructure quickly back in service.

They have more to worry about than properly documenting an incident scene.

Facing substantial risk
Yet, public agencies and utilities owning and maintaining major infrastructure face substantial risk when infrastructure failures cause property damage and/or personal injury. The jurisdictions and/or the individuals damaged will want to establish responsibility for a variety of reasons, including potential litigation and monetary damages.

A failed 30-inch diameter asbestos cement (AC) pipe was reassembled to observe installation and post-installation conditions in order to identify failure modes.

Public works professionals and utilities personnel are typically not focused on pinpointing the exact cause of the failure, the parties or individuals that may have contributed to the failure, or the collection of site evidence that might ultimately be used for the allocation of blame or costs. The broken infrastructure components are hauled away (frequently to a land disposal site), photographs may or may not be taken, witnesses may or may not be interviewed, and most physical evidence may be quickly lost, damaged, or compromised.

Major frustrations and problems can occur when thorough documentation of the failure zone does not take place before the failed infrastructure is repaired. Incomplete documentation of a failure location can lead to incomplete information, speculation and false conclusions when it is time to sort out the potential causes and responsibilities for the incident. Repairs made prior to proper documentation can destroy critical evidence. Such circumstances can add to additional legal expense and increased exposure to risk and liability. It can even mean the responsible party is not allocated damages from the failure.

Documenting the scene
Ideally, once the incident scene has been secured and access permitted by emergency personnel, a documentation team made up of forensic engineers, in coordination with public works and utilities personnel, should begin collection of data within the failure zone before significant repairs are undertaken. Visiting the site as soon as possible after the failure, the forensic engineer:

  • Directs that the repair crews do as little as possible until measurements are taken and the site is photographed.

  • Identifies witnesses who might have observed the site conditions prior to or during the incident.

  • Identifies Underground Service Alert (USA) utility location markings.

  • Observes the repair process and preserves sections of broken pipe, and/or other physical evidence.

  • Documents where broken pipe was found, its condition prior to removal, marks it for future reference, and requires that it be preserved as evidence.

  • Collects and reviews copies of documents that may be vital information in reconciling the cause of a failure: contractor's contract, construction as-built drawings of the broken infrastructure, reference drawings of adjacent infrastructure.

  • Compares the in-situ condition with the construction documents in an effort to establish if the original installation procedures may have contributed to the failure.

  • Collects documents related to construction on any adjacent project to establish or refute potential contributory negligence.

These activities employ the latest in digital photography, GPS and digital imagery technologies. HazMat-trained survey crews may be dispatched to measure the location and extent of low-level hazardous materials spills.

Resolving responsibility
Thorough documentation of the physical evidence of the scene is critical. This information will be vitally important in establishing the cause and responsibility for the failures that occurred.

A case in point: After a large potable water main failed adjacent to a sewer construction zone in a Southern California city, a forensic engineer was immediately called to the site to document the in-situ condition prior to the repairs. He arranged for a survey crew to field-measure the proximity and relative elevation of the remaining sections of water main with respect to the sewer. To approximate the mode of failure, the pieces of broken water main pipe in the sinkhole were located, measured, photographed, and marked. He also interviewed and collected documentation from the city resident engineer overseeing a contractor working on an adjacent sewer construction project.

After the field investigations were finished, the forensic engineer collected the reference construction drawings and crosschecked everything against the daily reports, diaries, and site photographs taken by the resident engineer. Ultimately, he established that the sewer contractor contributed to unanticipated settlement of the water main, which resulted in its subsequent failure. Armed with this information, the city then approached the contractor and its insurance company for compensation.

Documentation of the physical scene can do much more than pinpoint responsibility for infrastructure failure. By leading to improvements in operations and maintenance procedures and by supporting the development of new design standards, it can minimize the reoccurrence of the failure.

It may be counterintuitive to not clear away the damage and immediately initiate repairs, but in the long run it is well within the public interest to get the forensic engineer on the scene first.

A leader in the infrastructure forensics field, Curtis Edwards has dealt with dozens of cases over the last 20 years. He can be reached at (858) 576-9200 or cedwards@pcg-psomas.com. San Diego-based Pountney Consulting Group merged with Psomas in 2004.