February 17, 2015
Pipe Inspection Technology Keeps Civil War-Era Sewer Pipe Undisturbed During Sewer Separation Project
Those of us who work in an industry with underground infrastructure know how difficult it can be to keep track of them all. While newer installations of pipe, structures and conduit often come standard nowadays with CADD drawings, detailed as-builts and GPS coordinates, items installed prior to the electronic age came with no such things. Location descriptions depended upon the skill of the assigned draftsman, the memory of the construction staff, and even the day of the week the work was completed.
So what happens when historic asset location information must be checked to ensure proper accuracy?
Such was the case the summer of 2013 in Fort Wayne, Ind., where large diameter brick sewers dating back to the Civil War era still snake their way under the center of this bustling metropolis. The mapped location of one such pipe — a 72-in. diameter, double-ringed brick sewer installed in 1867 — came into question the as the City embarked on a significant downtown sewer separation project.
Several new storm sewer pipes, ranging from 30 to 42 in. in diameter, were to be installed in proximity of the historic brick combination sewer pipe, as well as several new storm structures including an oversized 84-in. diameter storm manhole.
During the design phase of the sewer separation project, engineers referred to Fort Wayne’s Geographic Information System (GIS) maps to identify known existing underground infrastructure in the sewer separation project area. As the location of the work involved one of the City’s major thoroughfares, it was critical that the new storm pipes and structures neither compromised nor conflicted with the existing 72-in. brick pipe. But how accurate could illustrations of a pipe installed nearly a century and a half ago truly be?
To find out, City engineers turned to their dedicated counterparts at Fort Wayne City Utilities Water Pollution Control Maintenance and Stormwater Maintenance (WPCM/STM) Department. WPCM/STM is comprised of 74 employees responsible for the maintenance and repairing of existing sanitary and combination sewer systems in Fort Wayne’s sewer service area, as well as the stormwater infrastructure within City limits. Fort Wayne City Utilities’ sanitary and combination sewer system is comprised of approximately 1,360 miles of pipes and serves a population of approximately 240,000, and its stormwater system is comprised of approximately 538 miles of pipe.
A request was made to have the location and path of the 72-in. brick sewer identified and marked above ground prior to finalization of the design plans. WPCM/STM has a well-established closed-circuit televising (CCTV) program led by inspection supervisor Johnnie Robinson. Residing in its stables are three CCTV Sprinter vans fitted with RapidView’s IBAK camera systems, which utility crews have been operating for nearly a decade now. Each van carries an Orion camera with built-in radio sonde/transmitter and steerable tractor with robotic lift for small- to medium-diameter pipes, and an Orpheus camera with built-in radio sonde/transmitter and steerable tractor with robotic lift capable of televising medium- to large-diameter pipe. Also stocked on each vehicle is one of IBAK’s manhole adaptors, which can be used with the Orpheus camera heads in place of a standard tractor for structure or stationary inspections.
Inspection details and video recordings are collected in the trucks using PIPELOGIX CCTV software by Pipeline Assessment and Certification Program (PACP) certified operators. Data is stored on portable hard drives in the trucks and then transferred to the City’s main server when crews return to the office.
Robinson’s inspection group is known for its ingenuity when it comes to televising tricky or difficult locations, and this project would be no exception. Upon receiving the request, Robinson and his staff visited the future jobsite to do an initial assessment of the work area. They identified that the manholes that would serve as access points for the televising work were each approximately 16 to 18 ft deep, with flow levels varying between 6 and 12 in. deep.
While the IBAK Orpheus system with its large wheel kit setup is designed to operate in 72-in. diameter pipes, the group was concerned with the possibility of displaced bricks and/or other unseen obstructions lying hidden in the murky flow. Additionally, with no guarantees that the sewer pipe followed the exact path indicated on the GIS maps, the TV operators at WPCM/STM were unsure if the steerable tractor would be able to navigate underground turns through the flow and possible obstructions without worry of the tractor tipping and/or becoming stuck. After much discussion and deliberation, the group came up with a unique solution: It was time to go old school, with a modern day flair.
One of WPCM/STM’s most senior and experienced employees was selected to make a confined space entry and walk the 72-in. brick sewer. This eliminated the concern for possible tractor tipping and/or the device becoming stuck.
While a visual of the pipe would help identify its path underground, it would not meet the engineering group’s request to mark the sewer’s path above ground. This is where the IBAK system came into the picture. The employee would carry an IBAK manhole adaptor device fitted with an Orpheus camera head but minus the typical fiberglass pole attachments. Because the camera head has a built-in radio transmitter, crews above ground would be able to trace the camera’s — and thus, the sewer pipe’s — path.
On May 8, 2013, after much collaboration between engineering and the maintenance crews, the pipe location and marking event began. While a confined space entry crew was getting in position to walk the sewer and monitor the project from both above and below ground, additional crews were deployed above ground for traffic control, radio signal detection and spray paint marking of the pipe’s path on the roadway. Approximately 450 ft of 72-in. sewer pipe was televised using this hybrid sewer televising method. Two-way radios kept above and below ground staff in communication as the employee walking the sewer would stop and angle the camera to collect a visual of all lateral pipes connected to the brick sewer.
While the process was slow and rather tedious, it went off without a hitch and provided engineering with invaluable information. Had the exact path of the sewer pipe not been traced, the 84-in. diameter storm manhole would have been in direct conflict with the historic 72-in. combination pipe. Thus, excavation based only on early map assumptions could have proven catastrophic and likely led to the closing of a major road artery leading into downtown Fort Wayne.
Instead, the engineering group was able to take the collected information and adjust their designs well before construction began. After modifying the proposed location of the large storm manhole and readjusting its connecting pipes for slope, the sewer separation project’s design was approved and moved into the construction phase. Care was taken to minimize soil disturbance near the path of the 72-in. sewer, and traffic disruption was kept to a minimum.
Through the coordination of efforts between design engineers, maintenance crews and construction contractors, the new storm sewer installation was declared a success.
Not all discovery projects run as smoothly as the aforementioned example. As with any underground infrastructure, too often companies are digging “blind” all the while hoping that no conflicts will be found and/or other utilities hit. Using the vast array of equipment available today, coupled with the knowledge and experience of our dedicated workforce, utilities have the ability to make the overall process run more smoothly while protecting some of our oldest and most critical pieces of infrastructure.
Karen M. Morris, M.P.A., is program manager with Fort Wayne City (Indiana) Utilities.