With its continued investment in the electrical transmission grid, ITC Holdings Corp. (ITC), the largest independent electrical transmission utility in the U.S., sought to take a closer look at its potential for harmful oil spills and how to mitigate damage if one should occur. The company understood a large spill not only could be harmful to the environment and a public relations nightmare, but it also could cost the utility millions of dollars in damages and cleanup costs. With this in mind, ITC engaged Burns & McDonnell to develop a program to identify, evaluate and design secondary oil-containment solutions that fit the needs of its expanding power grid network.
With the acquisition of existing transmission infrastructure from other companies being part of its transmission development portfolio, ITC wanted a program to identify secondary oil-containment improvement needs systemwide. The utility's infrastructure, acquired from different owners, used varying secondary-containment designs and philosophies.
To build its own program, ITC's environmental and engineering departments worked with their consultant, Environmental Consulting & Technology Inc., who assists ITC in the development and management of the utility's Spill Prevention Control and Countermeasure (SPCC) plans for all stations. A high-level study identified several high-priority sites where ITC thought it could make improvements. The study focused on the size and quantity of oil-containing equipment on-site, the means for potential spills to travel off-site and the potential environmental exposure of a spill. Additionally, ITC wanted to proactively ensure compliance with the U.S. Environmental Protection Agency (EPA) SPCC rules.
Secondary containment needs were reviewed for oil circuit breakers, reactors, transformers and other equipment containing large amounts of oil. The volume of oil in the equipment was considered in determining containment needs. Because higher-voltage equipment typically contains greater volumes of oil, sites handling high voltages were among those selected for further review. Large sites with multiple transformers and circuit breakers were chosen because they had a higher spill probability.
Sloping sites and those with storm-water drainage systems also were reviewed. The drainage systems typically included swales and perforated pipes installed throughout the stations for collection and routing of storm water off the site. The pipes either release storm water at the edge of the property or connect into a municipal sewer system. These systems are designed to handle large amounts of water, transferring it quickly outside the fence of the station and often off the property. While it is beneficial to keep a dry and easily maintained site, these pathways can have a significant impact during an oil spill. Sites with storm-water drainage systems that either drained off-site or connected into sewers were identified and selected for further review.
Infrastructure sites with sensitive environmental areas nearby also were studied in the selection process. These sensitive areas included bodies of water such as rivers, streams, lakes and ponds, and other areas that could be damaged by an oil spill, including wetlands, grasslands and wooded areas. The presence of such areas adjacent to a station creates the potential for a spill to have significant detrimental effects. Further, cleanup efforts could be more difficult and more costly.
Sites identified in the initial study were researched and physically inspected for containment and response characteristics. These characteristics included the proximity to and condition of the environmental areas, soil characteristics, drainage, response time, and condition of equipment and any existing secondary containment. Based on this evaluation, oil-containment needs were identified and solutions were evaluated to select an appropriate design alternative. ITC sought to implement solutions that could meet three criteria:
Require minimal maintenance
Use similar products to provide consistency and familiarity to its construction and operation crews\
Optimize investment by comparing costs to performance risks.
Site grading and topography were reviewed to determine the direction and rate at which an oil release would travel. Existing soil borings were reviewed or new ones were obtained to determine the subsurface profiles at each site. Depending on the soil characteristics and water table depth, different containment solutions were appropriate. For sites with pervious soils and for sites with high water tables, containment solutions needed to both prevent oil from flowing off-site and from infiltrating into the groundwater. The containment solution also needed to handle storm water that may collect in it and allow it to infiltrate or flow off-site as usual. Where pipe drainage systems were installed, containment solutions were designed to either prevent oil from entering the drainage system or intercepting it before discharging off-site.
Site locations, operation and maintenance schedules, and local infrastructure were reviewed to determine estimated response and cleanup times. Sites in rural areas were considered a higher risk with respect to spill response and confinement because of the likely delay in initially responding to and identifying a spill. Further, it would take longer for cleanup crews to reach, contain and clean up a spill.
The condition of oil-containing equipment and existing oil containment was examined. Old items were identified as having a higher potential for harmful spills. Existing oil-containment provisions were reviewed for condition and design to determine if repairs or modifications were needed. Prior to ITC ownership, many sites had minimal maintenance performed on the original containment solutions.
After the additional containment needs were identified and evaluated, solutions were designed based on effectiveness, maintenance, cost and constructability. No two sites were the same, so the containment designs and methods varied depending on the specific site conditions. The design evaluation also considered whether single equipment, multiple equipment or sitewide containment was appropriate, depending on the size of the site and location of the equipment.
Equipment requiring containment was reviewed for scheduled replacements. Some of it was already scheduled for replacement in the upcoming years. Oil-containing circuit breakers were the main component identified for scheduled replacement. The breakers were to be replaced with new SF6 breakers, which do not need oil containment. The replacement schedules for those pieces were expedited when possible.
At sites where it was not possible to prevent a potential oil flow into existing storm-water drainage systems, containment solutions were designed to intercept the oil before the discharge point. Drains were rerouted and manholes were installed with an AFL Industries stop valve. This system allows storm water to continue through while oil is captured. These systems are available in several sizes and easily installed with minimal site disturbance. Larger oil-water separation vaults also were used when more significant drainage areas required spill protection.
Belowground containment pits were put in place to capture spills at sites where pervious soil conditions were encountered or existing drainage systems existed. The pits were excavated, lined and then backfilled with washed stone. The required containment volume was achieved within the voids of the stone, and no above-grade modifications were needed.
To account for storm water captured in the system, C.I.Agent Barrier Boom was installed. This product uses granules embedded between two pieces of fabric that allow storm water to pass through but instantly solidify hydrocarbons on contact. Although this design was more expensive than some alternatives, primarily due to higher material and construction costs resulting from the greater amount of disturbance during installation, it was chosen because of its low maintenance requirements. Additionally, this solution did not obstruct access to the electrical equipment, although it did often require modifications to the existing grounding grid during installation.
In some areas, impervious clay soils prevented the use of infiltration for removal of storm water. Below-grade containments would have required the installation of pumps or drainage pipes. These were not preferred because of their maintenance and installation difficulties. Aboveground containments were implemented, including Strongwell walls or impervious berms constructed around the equipment. These containments were not filled with rock, thus they have a smaller footprint compared with below-grade designs. These designs also used C.I.Agent Barrier Boom for storm-water control. Windows were placed in the walls to allow storm water to flow from the containment off-site on the surface.
With the use of its secondary containment program, ITC has identified and prioritized many secondary oil-containment improvements throughout its system. It used cost-effective designs to provide long-term solutions with minimal operation and maintenance requirements. The program represents a sound, moderate investment in ITC's transmission system, helping the utility to be prepared should an oil spill occur at one of its sites. In the meantime, a modern transmission system improves service reliability, lowers the overall cost of delivered energy and allows new generation resources to interconnect to it.
Mike McNulty ([email protected]) is an environmental manager at ITC Holdings Corp. He is responsible for overall corporate compliance of ITC's environmental programs, with a focus on substations. He interacts with the engineering, planning and maintenance departments with respect to environmental requirements of new construction and ongoing maintenance. He sits on the IEEE Substations Committee Oil Containment Working Group, where he is currently updating IEEE Standard 980 - Containment and Control of Oil Spills in Substations. McNulty formerly worked as an environmental consultant before joining ITC and earned his bachelor's degree in environmental science from the University of Michigan-Dearborn.
Matthew Bauer ([email protected]) is a civil/structural engineer in the transmission and distribution division at Burns & McDonnell. He has worked with oil containment for clients across the United States and has five years of experience designing and managing substation projects. Bauer earned his BSCE degree from Iowa State University and is a registered professional engineer in Iowa and Michigan.
EPA Spill Prevention, Control and Countermeasure Rules
The Title 40, Code of Federal Regulations, Part 112 (40 CFR 112) governs oil-pollution prevention for the U.S. It establishes procedures, methods, equipment and other requirements to prevent the discharge of oil into or upon navigable waters. Navigable waters are defined in section 502(7) of the Federal Water Pollution Control Act and include lakes, rivers, streams, wetlands, wet meadows and natural ponds. Part 112 applies to, among other things, any owner or operator of a facility engaged in the use of oil and oil products, which, based on location, could reasonably be expected to discharge oil in quantities that may be harmful.
As defined in the regulation, the requirements apply to any facility with an aggregate aboveground storage capacity in containers greater than 55 gal (208 l) and an aboveground storage container threshold greater than 1,320 gal (4,997 l) or more. As required, the owner or operator or facility subject to part 112 must prepare in writing and implement a Spill Preventation, Control and Countermeasure plan typically reviewed and certified by a licensed professional engineer.
Exceptions to this include qualified facilities that either have no individual aboveground oil-storage container with a capacity greater than 5,000 gal (18,927 l) or a facility that has had no single discharge exceeding 1,000 gal (3,785 l) or no two discharges each exceeding 42 gal (159 l) within any 12-month period in the three previous years. These qualified facilities may self-certify their facility's plan.
Additionally, facilities with qualified oil-filled operational equipment as defined in part 112.7(k) may choose to implement alternative requirements to satisfy their general secondary containment. These alternatives include either providing a facility response plan under part 112.20 or a spill-contingency plan under part 109 and supplying a written commitment of manpower, equipment and materials required to expeditiously control and remove any quantity of oil discharged that may be harmful.
AFL Industries | www.aflindustries.com
Burns & McDonnell | www.burnsmcd.com
C.I.Agent | www.ciagent.com
Environmental Consulting & Technology Inc. | www.etcinc.com
Environmental Protection Agency | www.epa.gov
ITC Holdings Corp. | www.itc-holdings.com
Strongwell | www.strongwell.com