The first step in protecting our underground assets is to evaluate their conditions. NASSCO members offer high-tech cameras and other equipment, services, software, and methods to access buried infrastructure and identify any areas of potential failure before they become a problem. NASSCO’s Pipeline Assessment Certification Program (PACP™) allows field workers to use a common language to classify conditions and record their level of severity. These results are then used to determine the best course of action to maintain or rehabilitate a compromised pipe, or section of pipe. With PACP as a prerequisite, laterals and manholes may also be assessed using NASSCO’s Lateral Assessment Certification Program (LACP™) and Manhole Assessment Certification Program (MACP™).
Sanitary sewer overflows (SSOs) are most often caused by the long-term buildup of roots, fats, oils or grease within a pipe. An acoustic inspection is a cost-effective way to detect blockages before an overflow or maintenance issue occurs. A transmitter is installed in a manhole that transmits a series of tones through the air gap within the pipe. A receiver is installed in an adjacent manhole and it listens for degradation in tones compared to a clean pipe. The data are analyzed in less than three minutes and rate the severity of the blockage on a scale from 0 to 10.
CCTV & Assessment Equipment
The most basic information needed to define pipeline rehabilitation requirements is the condition of the sewer pipe from a structural, maintenance, and physical dimension perspective. The most important tool for assessing the condition of a sewer pipe is by means of a detailed internal television inspection (CCTV). Yet, the growth of our communities with their associated new underground infrastructure, along with rehabilitation of existing pipe installations, has generated a growing need for more detailed dimensional inspection techniques.
CCTV (Closed Circuit Television) Inspection is one of the most effective methods used to determine the condition of existing and newly installed pipelines such as gravity flow sewers, above ground industrial piping, gas distribution piping and water mains from a structural, maintenance and physical perspective.
CCTV can be used to:
• Determine structural conditions
• Identify shape and material of construction
• Identify O&M and structural defects
• Locate service laterals
• Identify Infiltration & Inflow (I&I)
• Locate obstructions like roots, grease, debris and cross bores
There are many CCTV cameras available on the market, which function in a variety of pipe sizes. The rule of thumb is that a camera designed for a small pipe size should not be used in larger pipe because the quality of the picture will be significantly diminished. Larger pipe should be surveyed by a camera system designed specifically for that application. Adequate lighting, centering, and focus are critical to a good video picture and a good inspection. Today’s cameras with their remotely controlled focus and iris functions, light adjustments and the ability to pan and rotate provide the customer with excellent clarity and quality. Major advancements include color CCTV, DVDs, pan and tilt heads, self-leveling cameras and software to manage CCTV video, defect codes, database and photos.
Today, a wide array of CCTV and remote inspection technologies are available and utilize state-of-the-art methods such as sonar, infrared, laser profiling, panoramic imaging, gas detection, 3D modeling, wireless remote control and robotic cutters.
Impact Echo Testing
Testing concrete pipes is a critical element of utility efforts to develop cost management strategies and identify, repair or replace weak elements before they fail. NDT (non-destructive testing) uses sonic/ultrasonic techniques to conduct internal and external testing of concrete pipes to evaluate the structural integrity and identify pipe thinning due to internal hydrogen sulfide corrosion or external carbonization. Hundreds of miles of large diameter (48 to 120 inch) concrete water mains and hundreds of sections of concrete wastewater pipes have been evaluated using the impact echo technology. Internal sonic/ultrasonic impact echo and pulse velocity measurements are used to determine the integrity, strength, and condition of the core concrete and if broken pre-stressing wires have slipped and core concrete is delaminated from the cylinder. For wastewater pipes sonic/ultrasonic measurements are made on the exterior of an excavated pipe to determine if concrete core has thinned and weakened due to hydrogen sulfide corrosion.
Laser and Sonar
The need for more detailed dimensional inspection techniques is now being met with laser profiling in open pipes and sonar profiling of water filled pipes that cannot be easily drained or bypassed. Dimensional analysis using these technologies reveals and quantifies absolute diameters, ovality, offsets, cracks and discontinuities in a pipe structure that effect the life and performance of the pipe line. This dimensional information is just now starting to be used by the engineering and design agents to accept, evaluate and design new, existing or rehabilitated pipe structures.
The systems consist of the laser profiler attachment, calibration equipment and analysis software. A light ring is projected onto the pipe wall and recorded onto DVD for analysis in the field or in the office. The system is capable of inspecting from 6” to 72” pipelines. When used as a video survey tool it can provide accuracies up to 1 mm while measuring pipe size, deformation, erosion, encrustation, debris, grease, flows, joint displacement, lateral protrusion, surface damage and holes.
Attention to proper equipment calibration and operator training are issues that are being addressed by the industry to raise the level of confidence in the data produced through the laser profiling technology.
Lateral assessment is a vital component in the inspection, maintenance and renovation of collections systems. The CCTV Inspection is generally done using one of two methods; inserting a small diameter camera designed for 3-inch to 6-inch pipelines via a clean-out towards the mainline, or using a robotic mainline/lateral inspection camera system that launches a camera from the mainline connection up towards the building connection/clean-out. Newer equipment now has the capability of panning and tilting the lateral camera while inspecting lateral pipes; as well as laser profiling the lateral pipe ensuring the right sized liner is installed during lateral pipe renewal projects.
Assessment data gathered by either of these two methods (typically in a standardized format, such as LACP®, to merge with mainline assessment data) is used to determine the need and/or appropriate methods for long-term successful renovation of the collection system.
Pipe and Ground Penetrating Radar
Pipe penetrating radar (PPR) is the underground in-pipe application of ground penetrating radar (GPR), a non-destructive testing method that can detect defects and cavities within and outside mainline diameter (>18 in / 450mm) non-metallic (reinforced concrete, vitrified clay, PVC, HDPE, etc.) underground pipes. PPR has the unique ability to map pipe wall thickness and deterioration including voids outside the pipe, enabling accurate predictability of needed rehabilitation or the timing of replacement.
Ground Penetrating Radar (GPR) is a geophysical method that sends electromagnetic radar pulses into the ground to image the subsurface. GPR is typically used to detect buried utilities, potential voids and sinkholes, and bedrock and geologic hazards. When GPR encounters a buried object, a signal is returned to the receiver where signal variations are recorded.
Side-scanning relies on the proven inspection crawler platform to gather visual data from within a pipe. However, it implements digital image processing technology to deliver richer visual information in a format that is easier to analyze. Side-scanning also relies on software to manipulate video frames into a flat digital scan. This scan resembles a long mural or scroll, and it bears an image where length corresponds to the length of the pipe, and where height represents the full circumference of the pipe, from 0 to 360 degrees. These scans capture a level of detail far greater than conventional video, and present it in a format that is easier to review and analyze. Rather than sit through hours of inspection video, an analyst can view an entire length of pipe at one time, quickly pinpointing problem areas and making annotations and measurements directly on them.
After the CCTV inspection on the pipe, lateral or manhole is completed, what happens to the video and collected condition information? Previously it used to sit in boxes or shelves in a closet somewhere but now everyone realizes that data is too valuable, to too many people, not to share it between departments. With the NASSCO coding standard it is easy to share that data with other software programs. With a published list of codes and a data dictionary outlining field requirements, the NASSCO transfer file can be easily imported into a variety of other software programs. Most have added a standard import process for bringing the survey data into their management software so that costs can be easily tracked and additional work orders created for repair work or other scheduled maintenance.
Many of the data collection software vendors have incorporated an interface with GIS to access survey detail from the GIS program by the engineering staff in the office. The user can select the pipe on the map and open the video for playback. Some interfaces include the survey history of the pipe allowing the user to track the conditions and their changes over time. Usually the collection database can be “searched” and pipes highlighted in the GIS program that contain specific conditions or pipe grades making it much easier to plan additional work like repairs or jetting.
The data is also used by the GIS departments to verify that the map data is correct. Many maps have been created from old, historic mapping data and may not relate to actual in ground conditions. GPS coordinates can be collected in the field during an inspection and saved in the NASSCO inspection format. Other asset details like location, diameter, material, lining, and pipe lengths are also collected. This information can be exported so the GIS department can update their maps. Buried manholes that are found are added to the map creating new assets, both manhole and pipes.
Many engineering firms have built analysis modules to search these databases and make recommendations based on built-in risk assessments. It is not enough to know there is a fracture or a hole in the pipe, it is also important to consider the risk of failure of that particular pipe. Factors like public impact, environmental impact, age, and cost of repair versus replacement are all considered and built into their analysis.
When NASSCO introduced the PACP® standard in 2002, training the inspector to understand the different conditions was a major component of the program. Since then NASSCO established a re-certification program that each inspector will take every three years to bring them up to date on the new codes added for different survey types like grouting and storm inspections, as well how to handle new technology like scanning cameras and laser inspections.