“Last root-ball before lunch!” thought Joe the plumber, as he ran the snake up the sewer lateral toward a tangle of roots and tissue. The cutting tool spinning at the end of the snake hung up a bit, but the motor powered it through the blockage all the way up under the foundation of the house. As he rewound the coil, Joe didn’t notice that leading the rush of water down past the lateral cleanout were scraps of yellow plastic, the color of the toy dump truck up on the front porch of the house. In the downstairs laundry room, a cat slept on the warm dryer where a load of socks and jeans tumbled. Silently, natural gas began to seep from the washing machine drain and spread out in a sulfur-scented layer across the concrete floor.
As replacement and expansion of natural gas facilities has accelerated in recent years, Distribution Integrity Management Programs (DIMP) across the country have been faced with managing the increased risk of cross bores. A gas cross bore as an intersection of a sewer main or lateral by a gas distribution main or supply line, which compromises the integrity of one or both utilities (Figure 1). They typically result from gas installation by trenchless methods. Undiscovered cross bores can lead to sewer line blockage, eventually prompting cleaning activity. This presents a risk of the gas line being damaged by sewer cleaning equipment. A dangerous concentration of gas could then accumulate in sewer facilities or in structures.
 Natural gas is explosive in concentration between approximately 5% and 15% by volume of air, the lower and upper explosive limits (LEL and UEL) of methane.
Figure 1. Residential property cross bore depiction. (Source: callbeforeyouclear.com)
In response to guidance from regulators, many natural gas providers have updated field procedures to prevent the creation of new cross bores in trenchless gas construction. Proactive cross bore discovery programs are becoming popular as a way of identifying potential leaks in legacy distribution systems before they occur and jeopardize safety. Our experience has proven that advanced data management is essential to mitigate cross bore risk.
G2-IS has defined a better process
G2 Integrated Solutions (G2-IS), from its Concord, CA location, designs and leads cross bore risk management programs, leak and corrosion surveys and other inspection services aligned with PHMSA and API regulatory compliance.
Since 2011, G2-IS has designed and run cross bore safety inspection programs for major gas distribution pipeline utilities. Our experience evaluating over 150,000 potential gas and sewer line conflicts lead to the data management advancements discussed here, which support client plans to accomplish over 4 million evaluations of customers’ and other properties.
Asset-Centric Assessment Process
Searching video footage collected in sewer pipe for intruding gas pipe is what a typical legacy cross bore inspection program requires. Best results can be achieved by giving inspectors the ability to update status based on their work in the field and managing each sewer pipe segment and property parcel as an individual asset. Such a process, managed in our new software tool is the basis of best practices for running a cross bore safety program that reduces risk to a minimum.
The critical difference between standard practice and using our new system is verifiable proof of the elimination of cross bore risk in each case. A custom software dashboard with a Geographic Information System (GIS) map interface gives authorized inspectors, managers and clients a personalized view of the tasks and data relevant to their work at each stage of an asset’s inspection cycle. A single parcel record within the system can pass from assignment, to permit queue, to access permission, to discovery of a cross bore, to repair by the gas company, and back to the inspector to verify cross bore-free status, all without ever changing hands or communication delays.
The tool eliminates all data transfer by email and the human error that is prone to, and automates many QC operations. As we will see, it reduces uncertainty and risk at each stage of a legacy cross bore inspection process.
Safety is the primary driver of the effort, yet cost controls are also important. A risk-informed process that prioritizes inspections only where gas service construction records and as-built drawings indicate a potential for conflict with sewer systems limits the scope and costs. Records give evidence of bored or drilled installations, or pipe material (plastic, polyethylene) commonly installed without trenching. However, data loses relevance unless results of records analysis are securely and accurately related to the gas and sewer assets at a specific location.
The ID of each parcel is the link between the property location in GIS and the digitized gas construction records, which are visible through the map interface. First the GIS locates each parcel relative to manholes and digitized sewer mains. Then the digitized as-built and gas records are tied to the parcel ID. GIS also helps to efficiently cluster assignments together, giving inspectors a series of addresses to inspect in sequence. Camera operator and truck ID are linked to each parcel. All subsequent permit, notification, and inspection data are tied to the same record in the database making decisions and results easily traceable to the supporting evidence.
Qualified inspectors view the GIS map database through the software interface as they systematically check inside sewer mains and laterals with robotic CCTV video equipment (Figure 2). It is of utmost importance to enforce and verify the use of standardized operating procedures (SOPs) that ensure all sewer pipe segments, including previously unknown/unmapped segments will be inspected and their inspection data added to the database.
 Closed Circuit Television captures video recording including location and descriptive data.
Figure 2. CCTV sewer inspection with a remote controlled lateral launch camera collects evidence that identifies gas cross bores or verifies their absence. (Source: G2-IS (cross bore video frame) and Envirosight LLC (lateral launch camera)
Each segment of sewer main between manholes is counted as a single asset. As an operator launches the remote controlled camera from the main into a lateral tap, he draws a schematic lateral line between the main and the parcel, linking them in the system map interface. Each lateral drawn represents a new asset with its new ID tied to the parcel ID, and both IDs link to the video file.
Following our SOP:
- The video camera frame includes the lateral asset ID, the measured locations of segment endpoints and distances of lateral assessment observations along the pipe segment.
- A wye junction may indicate a branch lateral connection. The camera operator draws a second lateral segment in the map at the wye location, forming a second pipe asset ID. A branch must be video inspected just like any lateral.
- Encountering a p-trap or blockage triggers a procedure to schedule a push-camera crew to collect video of the section of pipe the lateral launch camera cannot pass through. If the lateral is not completed with push-cam footage, cleaning may be scheduled before reattempting to clear the lateral.
- Some blockages have to be approached from the other side by pushing a camera downstream from the structure. This SOP involves scheduling access with the property owner.
- Records of each action are tracked with the asset IDs in the database, as are traffic permit forms and other location specific information.
- Assignments will not be confirmed as complete without video and other valid records attached to the record in the system. Ultimately, a video or legitimate exception will be stored in the GIS system with asset IDs for each pipe asset on every assigned parcel.
 The SOPs and experience of NASSCO certified sewer inspectors with specialized lateral assessment qualifications produce the most reliable inspection data.
Better Communication and Process Control
An asset-centric assessment database dashboard results in more complete and timely work. Inspectors in their camera trucks can prevent return trips because they have a more immediate view of the inspection status of each assigned asset on a block (Figure 3 & Figure 4). Any incomplete segments or gaps are immediately reported to operators for on-site correction, and tracked to prevent unnecessary re-inspection. Computer workstations in the inspection trucks are connected by Wi-Fi or wireless cellular, and when outside a wireless coverage area they can work with the system offline.
Figure 3. Color coding of assigned parcels indicates inspection status to operators in the field. Red parcel indicates assignment has been issued but asset is “unresolved”. (Source: G2-IS)
The integrated workflow management system can prompt people with task reminders. This moves tasks along, as each responsible party submits their part and the next action in the process is automatically shown to the next person responsible in their task list. Each participant has data visibility according to log in permissions, and each decision and transfer of responsibility is traceable. Eliminating email hand-offs can increase productivity approximately 20%.
Planning work areas with GIS enables the location-based tracking of CCTV video inspection, repair status, evaluation of risk factors, and statistical reporting. Automated data validation includes crosschecking addresses and parcel IDs in assignment databases against the inspection data returned from inspection crews. Acceptance criteria filter out inadequate and corrupt data files, and questionable results receive closer examination. Videos are reviewed by trained technicians in the office to monitor visibility of the pipe circumference, unobscured by low light, standing water, debris and other pipe conditions.
Inspector supervisors resolve technical problems in the field, ensure safety, coordinate the permit process, and communicate with stakeholders and property owners. They also make daily reports on all aspects of work, each linked in the GIS system to the affected pipe asset ID and parcel ID. A gas engineer will review reports, video images and other evidence to determine when to excavate a cross bore and perform repairs. As assets change status, their depiction in the system map view changes color. They appear green when video and report data show acceptable evidence of completion.
The decisions DIMP leaders make about risk tolerance are grounded in reality by inspection data. GIS data has to first be entered correctly before it can be managed. Most inspection operations not using asset centric processes rely on data handed off to specialists in the office and a fairly long feedback loop, typically with error prone email data transfer built in.
Forms of verifiable proof:
- Engineering Records – As-builts and other construction records showing the basis of decisions, used to determine whether or not to inspect specific sewer mains and laterals.
- Inspection Videos – Linked to parcel polygons and addresses, providing evidence for decisions regarding repair or clearance, and demonstrating the absence of cross bores in pipe assets.
- Field Forms and Data – Cross bore discovery and repair, pipe damage, building access and findings requiring research or a decision by a gas engineer.
Each analyst’s throughput can increase as hours are saved by automated validation of field work data, reports and videos against the reference GIS and decision making model incorporating acceptance criteria.
- Detailed gas service record review identifies which locations to inspect, saving the cost of inspection, GPS collection, QC, forms, and results validation, at parcels where the gas installation record shows extremely low likelihood of impacting sewer lines.
- Automatically catching and completing all parts of work assignments while on site saves costs of second or third trips to the site to finish incomplete inspections.
- Sewer inspection video analysis performed by qualified personnel and compliant with industry standards gets the most value out of the video review sampling process and reduces re-inspections.
- Traceable and secure systems for managing data, documents and reports to stakeholders save time and frustration searching for evidence of status, because it is all tied to specific assets related to specific locations and addresses.
The G2-IS asset-centric database approach profoundly improves transparency, traceability, verification and confidence in each phase of the asset data lifecycle. The data is continually updated and made available to authorized stakeholders through a web interface. DIMP leaders can easily find the status and records relevant to any address in case of inquiry or audit. They can also query the data to highlight trends and help refine the criteria used in decision making. For example, they may want to analyze all installations by a specific crew in a specific time frame.
Verifiably complete records of inspections of all potential sewer and natural gas asset conflicts within program scope are readily available to present as evidence that the cross bore safety inspection program is well controlled, giving DIMP leaders confidence they are taking prudent precautions to make the gas distribution system safer from cross bore risk.
Figure 4. The color of parcels and pipe assets indicates their inspection status at a glance. Green means inspection is complete and status is “resolved”. Yellow means “partial inspection”, as may occur when a lateral is blocked with debris. Red means asset status is “unresolved.” (Source: G2-IS)
The G2-IS asset-centric assessment data management techniques and tools described in this article help natural gas service providers avoid the common pitfalls of a typical manually controlled legacy cross bore inspection program and ensure maximum elimination of cross bore risk, with less cost. Tracking each parcel assigned and each pipe segment observed as assets with the system can prevent costly delays and rework by providing field operators with prompt status information for each gas asset. Most importantly, natural gas distribution risk management decisions can be made with confidence based on complete and highly accurate inspection data.
For more information, or to see a demonstration of G2’s asset management software application within a cross bore safety program, please visit g2-is.com/crossbore.