January 2011 Vol. 238 No. 1
Features
Guidelines For Successful LDC Pipe Replacement Programs
This article focuses on steps in developing a successful pipe replacement program at a local distribution company (LDC). It will review the elements of a distribution integrity management program (DIMP) plan relative to pipe replacement and will discuss: 1) the common criteria used to develop a program, 2) how to rank and prioritize pipe segments, 3) tips for creating a program timetable, 4) importance and usefulness of partnering with state and local officials, 5) efficiencies gained by creating simplified and practical standards, 6) identifying program resources, and 7) developing a program communications plan.
DIMP Regulations
DIMP does not require LDCs to implement a replacement program but as companies develop their DIMP plans some may choose to implement a replacement program or accelerate an existing program. Here are the seven elements of a DIMP plan and how they may relate to a replacement program:
1) Knowledge: Operators must develop an understanding of their distribution systems and identify pipeline characteristics and materials which may include Cast iron, Bare Steel, PVC, ABS and other high risk pipe materials.
2) Identify Threats: Operators must identify threats that affect or could potentially affect their distribution pipeline. These threats may include corrosion of bare steel pipe and cracking of cast iron pipe.
3) Evaluate And Rank Risks: Operators must evaluate the risks to their pipeline and the relative importance of each threat. There is a greater threat of corrosion to bare steel then to coated and protected steel.
4) Measures To Address Risks: Operators must determine and implement measures to reduce the risks from failure of their pipeline. These measures must include an effective leak management program which may identify higher leak incidence rates on bare steel and cast iron pipe.
5) Measure Performance: Operators must develop and monitor performance measures to evaluate the effectiveness of their integrity management program. One of the mandatory measures is the number of hazardous leaks eliminated or repaired categorized by material. Again this may identify higher leak incidence rates on bare steel and cast iron pipe.
6) Periodic Evaluation And Improvement: Operators must reevaluate risks and threats on their entire pipeline at least every five years and consider the relevance of threats in one location to other areas of their systems. Comparing bare steel and cast iron areas to protected steel and plastic areas of the system may show greater leakage in the bare steel and cast iron areas.
7) Report Results: Operators must report annually the number of hazardous and total leaks eliminated or repaired. One method of eliminating leaks is to replace leaking pipe.
Replacement Criteria
The first step in preparing a replacement program is to select and assess the pipe segments to be replaced. There is more than 100,000 miles of bare steel and cast iron main in service. These are the most common pipe materials selected for replacement. Most programs begin by identifying and quantifying various conditions and threats found in the distribution system. Some of these conditions and threats typically include: 1) poor pressure areas – which can lead to customer outages and restricted growth; 2) high risk densely populated areas; 3) leak and maintenance histories – indicating leaks by cause and pipe material; 4) less than desirable soils – clay, organic and corrosive soils; 5) environmental problems – areas prone to flooding or land slides; and 6) recent or proposed adjacent or encroaching construction – activities which could result in unreported damage and undermining.
Ranking And Prioritization
When condition and threat information is identified and quantified, the next step is to rank and prioritize the selected pipe segments. There are commercially available replacement decision applications to assist in selecting replacement candidates using LDC defined risk factors.
Some LDCs use algorithms they have developed internally to rank and prioritize pipe segments for replacement. Either method typically utilizes: 1) leak incidence rate – leaks/mile; 2) segment location – urban, suburban, downtown; 3) surface conditions – wall-to-wall paved areas vs. open field; 4) population density; and 5) economics – regional replacement costs.
Prioritizing individual projects may be done by replacing the worst segments first and thereby reducing future O&M expenses. Some LDCs prefer to replace large contiguous areas where they may uprate to a higher system pressure.
Coordinating main replacement projects with public works projects promotes better relations with public officials and can help reduce resurfacing costs by sharing those costs with public improvement projects.
Program Timeline
Once the total footage of pipe for replacement has been determined, the next step is to determine the program timeframe and the expected annual replacement footage. We have seen programs developed for time periods ranging from five to 20 years and annual replacement footage expectations of between 25,000 feet and 500,000 feet, or about five to 100 miles per year.
An influence on determining this timeline is the duration of the construction season which may be limited by weather conditions especially at northern LDC locations and the amount of capital dollars available. Both will govern the annual footage to be replaced.
Jurisdictional Collaboration
It is always advisable to get early buy-in from the jurisdictional community which can lead to support for cost recovery and construction coordination. Public utility commissions are normally interested in programs which promote improved reliability and safety. They also look for replacement programs that generate reductions in O&M spending due to replacing leaking pipes.
An important topic to discuss with PUC officials is a mutually agreeable rate case strategy which includes replacement-cost recovery.
Working with public works officials long before construction begins can prove to be beneficial to program success. Departments of Public Works do not appreciate last-minute surprises when it comes to construction activity in their public rights-of-way. They appreciate and expect adequate notification of a major replacement program in their jurisdiction. Coordinating pipe replacement in a ROW scheduled for public improvement can help avoid digging up newly resurfaced roads in the future. You can also take the opportunity to negotiate a streamlined permitting process and share the costs of surface restoration.
Design And Construction Standards
It may be beneficial to review your design standards and consider using a simplified design approach to reduce design time and cost. An early saver of time and costs is determining what level of detail is really needed. Permitting agencies require a certain level of detail on permit drawings and that will normally determine the overall drawing detail.
Some LDCs have been successful in negotiating a more streamlined approach for permit drawings. Some have conducted beneficial meetings with their construction contractors to determine what level of detail a crew actually needs on construction plans. They have found that much of the detail they provide on the drawings is considered not necessary by their construction contractors.
LDCs with multiple regions and operating centers have found construction standards, materials and installation methods vary from location to location within the same company. Take the opportunity to make sure your company not only has practical standards but they are being followed consistently company-wide.
Program Resources
Determining program resources early in the process is important to allow sufficient time to acquire or free up resources required for a successful program. Internal resources will be needed to develop and manage the program and oversee construction contractors. If replacement design and engineering is outsourced, then the requisite number of contractor personnel must be determined based on the amount work to be designed each year and how long in advance of construction the projects need to be designed.
Engineering and design contractors can commit to a short ramp-up time and can adjust to varying workload levels. There are several firms experienced in pipeline replacement program design.
Not only do construction contractors’ resources need to be established but the process to bid and procure contractor services needs to be decided. LDCs with multiple-year replacement programs typically use block bids or multi-year contracts to gain best pricing through economies of scale.
Ensuring that the proper materials are available in sufficient supply throughout the construction season is essential in minimizing stock outs which cause delays to construction crews.
Standardization of materials follows along the same lines as design and construction standards. Take the time to establish standards for pipe, fittings and materials and ensure they are being stocked and used company-wide.
Program Communications Plan
Communicating the program purpose and expectations to key stakeholders is essential for a successful program. Internal communications should be provided to, at least: 1) operations, 2) design, 3) supply chain, and 4) customer call center.
The operations group and the engineering group are normally involved in program development. The knowledge and experience of subject-matter experts from these groups are invaluable to the success of the program.
Purchasing and Materials Management departments need to be aware of material and resource needs. Call Center personnel need to be aware of the program in order to properly respond to customer inquiries relative to the construction activities in their neighborhood.
External communications are needed to achieve buy-in and support from PUCs, DPWs and local officials. Commitment and backing from these groups can lead to positive rate recovery, blanket permitting and less burdensome restoration requirements. The residents can be made aware of the locations and timing of construction activities via letters, company website or newspaper articles.
Contractors need to be made aware of the program resource needs well in advance of construction to allow them sufficient time to allocate additional crews and equipment.
Author
Les Goodman is vice president of EN Engineering based in Glen Burnie, MD. He has more than 30 years of experience in natural gas engineering, operations and maintenance. He can be reached at 703-477-4812 or lgoodman@enengineering.com.
Acknowledgement
This article is based on a presentation from the 2010 AGA Operations Conference held in New Orleans, LA.
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