Dominion’s Strategic Underground Program

At the end of August 2011, Atlantic Hurricane Irene left severe damages on the east coast. Then, in June 2012, a derecho event (defined as a long-lived, rapidly moving line of thunderstorms that produces damaging winds) hit the Midwest and Mid-Atlantic, becoming one of the worst derechos in United States History. In each of these events, approximately 1 million of Dominion Energy’s customers were left without power for extended periods of time in part due to downed trees over powerlines. With customer satisfaction in mind, it was in the wake of these natural disasters that Dominion decided to act proactively and begin undergrounding overhead distribution wires. A study period for creating and implementing an undergrounding program in Virginia began between 2012 and 2013, ultimately leading to the creation of its Dominion’s Strategic Underground Program (SUP) on January 1, 2014, the first large-scale undergrounding program in the United States. Since its creation, Dominion has undergrounded nearly 2,000 miles of the most vulnerable (outage-prone) overhead lines in Virginia. Dominion’s ambitious goal is to convert 4,000 miles of overhead utilities to underground supply in Virginia. While considering undergrounding in North Carolina as well, their current plans involve a more modest scope, possibly ranging between 200 to 300 miles.  

Identifying areas to underground

“If you’ve ever worked storm, and I worked storms in the early and mid-2000s, you know where to go. You go back to the same places every time.”- Les Carter, Fortnightly

Dominion’s approach to choosing which areas take priorities for undergrounding is simple– identifying the most outage-prone areas. Not only is this approach most logical in order to reduce the number of customers without power (therefore increasing safety for the largest possible audience), it also helps reduce economic costs by reducing the number of locations they have to restore power to following severe weather events. Additionally, this means in areas that are not yet undergrounded, power should be restored faster because the areas that previously required large restoration efforts no longer require it post-undergrounding.   

Following the findings of the 2012-2013 study phase prior, Dominion decided to take a targeted approach that focuses on undergrounding tap (AKA lateral) lines, or the lines that run alongside streets and in private backyards to reach homes and businesses, rather than all available overhead distribution wires such as mainline wires (three phase lines that are up to 5 times more expensive to convert). Another benefit of this approach is that lateral lines in residential and natural areas are more likely to be surrounded by trees, and therefore more at risk of being damaged during storms. By looking at the 10-year performance history of their tap lines, Dominion found that 20% of their tap lines were responsible for two-thirds of  power outages– these are the 4,000 miles that Dominion is hoping to underground as part of their SUP.  

Customer communication and community buy-in

Because Dominion’s focus is on undergrounding tap lines that are mainly located in residential areas and private property, Dominion faces a unique challenge: community buy-in. For undergrounding to occur on private property, Dominion must obtain easements (a legal document granting permission for Dominion to perform undergrounding on public or private land) from property owners for installation, maintenance, and repair because they do not rely on eminent domain. In other words, without customers agreeing to provide an easement, no undergrounding can occur. For Dominion, this translates to customer service and satisfaction being a top priority. Even with the creation of new internal roles solely dedicated to this task, Marketing and Communications Coordinators, twenty to twenty-five percent of projects cannot be completed due to the inability to obtain easements.  

One of the most unique aspects of Dominion’s SUP is how they adapt to customer needs. To obtain easements, Dominion has utilized the following approaches to maintain customer satisfaction: 

• Avoiding infrastructure and utility damage: Dominion utilizes 811/municipal locating services to identify other private utility lines such as water and gas. Going further, Dominion works with property-owners to identify other personal underground property such as sprinkler systems, septic tanks, and even electric dog fences to make the undergrounding process as seamless as possible. 
• Communication: Once the undergrounding process is initiated, communication with homeowners occurs at least every 60-90 days via mail, post cards, door hangers, phone calls, and in person visits. These communications include information on the benefits of undergrounding and an overview of the undergrounding process, information on the easement process, customer satisfaction surveys, project updates, projected timelines, informational meetings, planned power outages, and if damages occurred. These communications are meant to improve transparency and formulated to appeasing customers. Dominion Energy has developed an underground communication process flow and has worked with many utility companies by provided templates to help improve efficacy in other locations.  
• Augmented reality: While undergrounding partially removes unsightly overhead wiring (see section on telecommunications partners for more information), it does require a pad mount transformer that will serve between six to eight customers to be placed on one of the property owner’s ground. Because of the visual impact, Dominion gives those customers a couple of options as to where the transformer will be located and complementing this by providing an augmented reality view of what the equipment would look like on their property.  
• Property restoration: Even with horizontal drilling that does not impact landscaping and tree roots, undergrounding can be slightly intrusive and impact lawns where the boring equipment lay and where transformers are placed. Dominion always restores property to the same condition it was found in by replanting grass. This property restoration may even occur if parts are back ordered due to supply chain issues slowing the undergrounding process. 

Technical considerations

There are many ways to underground utility wires. The best method for undergrounding is dependent on many considerations, including the structure and geology of the land and the type of utility line being buried. Dominion relies on a process called Horizontal Directional Drilling (HDD) in which cables are installed in a predetermined underground path. HDD is an alternative to trench undergrounding, where trenches are dug, powerlines are placed within, and the trench is covered back up. Trenching is much more ecologically and visually intrusive but is often chosen as a method because of its cheaper cost. HDD is a better option in areas where there are many underground obstacles like other utilities and where surface damaged needs to be minimized, making the residential areas Dominion works in a prime candidate. Despite a higher upfront cost associated with HDD, Dominion benefits from this approach by decreasing impacts to the customer’s property.  

When HDD undergrounding is done in residential areas, other underground utilities need to be avoided. When the underground cable crosses public utilities, additional holes need to be hand-dug in a process called potholing. Potholing exposes the other underground utilities so that the new electrical cable is cleared.  

Challenges

Supply chain  

Like many industries post COVID-19, supply chain issues are one of the biggest challenges Dominion faced. In some cases, Dominion is installing cable and conduit but having to wait until back-logged parts such as transformers are received to finish the project. While construction crews wait for parts, they are restoring the property so that the customers do not have to look at half-finished construction sites. While supply chain issues are slowly getting better and are set to correct in 2024, this limitation initially slowed their undergrounding goals.  

Telecommunication partners 

Electrical lines are just one type of utility that attach to overhead poles. Telecommunications companies also use overhead poles and wires. Dominion tries to work with telecom and cable companies to place their lines underground at the same time of electrical undergrounding, but there are many instances where they do not participate. In these instances, the transformer and electrical lines would be removed, and the pole shortened, but the pole itself would remain (Figure 1). While this reduces visual blight, it does not completely get rid of it– lowering overall customer satisfaction and illustrating why buy-in from telecommunication companies is important for creating more scenic areas.  

Fig. 1 

 

Regulatory challenges and methods 

Creating a new undergrounding program can be a daunting task. To propel their ambitious undergrounding goals forward, Dominion worked with the Virginia legislature to pass key legislation. For example, in 2014, Virginia Code §56-585.1 was amended such that Dominion could recover expenditures related to the program through a rider, marking the first instance of distribution investments receiving rider treatment in Virginia. This law was further amended in 2018 to provide additional guidelines regarding the expenses associated with underground projects, such that it created thresholds for SUP spending. Specifically, these updates established thresholds on the amount of money that can be spent for each mile of underground utilities and for each customer benefiting from these underground services. Additionally, In 2017, §56-466.2 was passed as part of the Virginia Electric Utility Regulatory Act, outlining the transition of overhead distribution lines to underground facilities. The legislation required Dominion to notify cable operators when relocating overhead distribution lines underground and allowed cable operators to choose between relocating their facilities underground or keeping them overhead. The legislation also addressed ownership and maintenance of utility poles and provided a legal framework for continued use of overhead facilities. Ultimately, the legislation aimed to enhance electric service reliability by transitioning existing overhead distribution lines to underground infrastructure in a cooperative and regulated manner, while ensuring clear legal guidelines and collaborator participation. 

Despite state legislation being passed, Dominion still needs to seek approval from the Virginia SCC because of the SCC’s role as the regulatory body responsible for implementing the legislation passed by the General Assembly. While the legislation provides the overarching framework for the undergrounding program, the SCC plays a crucial role in overseeing its implementation. Dominion’s SUP required approval from the SCC because it involved substantial investments in infrastructure and had implications for customer rates. Specifically, Dominion Energy sought permission from the SCC to add a specific charge to customer bills to recover the expenses related to undergrounding existing overhead distribution lines, i.e., a “rider.” 

In recent years, Dominion’s filings and the regulatory process have become more routine due to changes in the regulatory landscape. Initially conceived in 2013, the SUP was initiated when Dominion operated under fixed base rates, meaning they did not regularly submit rate cases. However, starting in 2018, Dominion resumed regular rate cases, transitioning to a triennial rate case schedule, which significantly impacted the regulatory process. Subsequent filings for the SUP have been for discrete phases of the program, ranging in size, and have incorporated mandated cost thresholds on a per-mile and per-customer basis. Dominion has diligently ensured that its filings meet legislative thresholds, resulting in SCC approval in recent proceedings, which typically involve interrogatories, hearings, and final rulings within approximately nine months of filing. 

Addressing socioeconomic inequities

In areas with undergrounding programs such as Virginia and North Carolina, many customers are eager for undergrounding to occur in their neighborhoods for both the increased resiliency following storms and the aesthetic benefits surrounding undergrounding. Additionally, in drought-prone places like California, many people are also worried about the increased risk of wildfires in areas where downed utility wires may ignite flames. Thus, with so many benefits of undergrounding it is no surprise that many people are impatient for undergrounding to be completed in their neighborhoods.  

However, research has shown that historically marginalized communities and lower socioeconomic areas are more at risk of damage during infrastructure development and are often excluded from undergrounding, and thus the associated scenic, safety, and resiliency benefits. For example, recent research using machine learning found that in California, undergrounding was more likely to occur in richer neighborhoods and that the overhead lines in poorer neighborhoods were more fire-prone.   

Dominion takes a unique yet powerful approach to dealing with energy inequity. When choosing which tap lines to underground, Dominion’s approach is to only consider one piece of information: which lines are most prone to power failure. This means that the bias in choosing which neighborhoods to underground in is completely omitted– neighborhoods are not chosen because they have more political and economic pull, only power outages influence the decision. In other words, undergrounding is a performance-based decision rather than a community-based decision. While this approach does not directly consider the discrepancies faced by historically marginalized neighborhoods during conception, Dominion has shown that this approach effectively address inequity. In fact, by completing studies after completion to ensure certain neighborhoods are not being favored, Dominion has found that their method has resulted in undergrounding progressing equally across both race and income.  

Measuring Impacts

“If a tree falls where there was an overhead power line, but the utility converted it to underground, would it have caused an outage and how long would it have taken to restore?”– Karen Kinslow, Former Dominion Director of Grid Resiliency and Undergrounding.   

Here, Karen, formerly of Dominion’s undergrounding program, notes that it is hard to measure the impacts of their undergrounding program directly because it requires them to know what did not happen. Anecdotally, following severe weather events in recent years, Dominion has received feedback from customers whose neighborhoods have been undergrounded that their power was unfaltering. On-the-ground servicemen have likewise reported that many neighborhoods requiring restoration no longer require it.   

However, to measure success more robustly, Dominion likewise utilizes data analytics in conjunction with community response to evaluate success. Their approach is to compare where outages were after major events after undergrounding has been completed versus where outages were historically before undergrounding was completed in storms that have a restoration period of 72 hours or more. 

Specifically, after significant storm events where a total length of restoration (TLR) period is at least 72 hours, Dominion conducts an in-depth analysis that uses a failure rate approach to gauge the SUP’s effectiveness. Using the company’s grid system, they track storm paths and outage data to estimate outage rates on candidate tap lines. On their grid, they can see areas where there was a transformer outage (assumed to be due to the storm) and areas where there were no outages. Special attention is then given to the grids with no outages as these may indicate one of two things: the storm did not pass through, or the storm passed through yet power did not fail. If 3 or more surrounding grids did have transformer outages, then it is assumed that the storm did pass through those areas but did not result in transformer damage. Once the storm’s path is determined, Dominion then determines how unconverted devices (overhead) performed by calculating an outage/failure rate that represents the performance of overhead transformers that they are interested in converting to underground per mile of unconverted SUP candidate tap lines. This failure rate is then applied to converted lines to estimate how restoration time was reduced due to undergrounding, and further projected out to get an estimate of restoration time will be further reduced once all proposed undergrounding is completed. Then, using an estimate of fuse restoration jobs per hour as a metric, Dominion can calculate how many hours are added to TLR due to lack of undergrounding. 

An example presented in Dominion Energy’s 2023 Annual Report was that of a major snowstorm characterized by high winds that occurred on January 3, 2022. This storm was especially damaging due to the high winds and wet snow that clings to trees, resulting in more tree outages and 250,000 customers without power.  Actual restoration time was 5.13 days, making this storm eligible for Dominion’s failure rate analysis.  

In this analysis, Dominion found that 1,764 miles of unconverted tap lines were affected by the storm. Then, they estimated performance by calculating a failure rate of 0.16 events per mile of exposed line (284 outage events on candidate tap lines divided by the 1,764 unconverted miles). This failure rate was then applied to 1,005 miles of converted lines that were impacted by the storm by multiplying the two values, resulting in 162 avoided outages. This computation was again performed on the proposed lines for undergrounding and found that SUP completion would result in 284 avoided outage events. Using a value of 12.1 fuse restoration jobs per hour, they found that the 162 avoided outages saved 13 hours to the restoration time (162/12.1=13.3) and that the proposed areas of undergrounding would save in the future 24 hours of restoration time (284/12.1=23.5). Thus, Dominion concluded that completing undergrounding would lead to a 27% reduction of TLR from 5.67 days to 4.14 days (Figure 2). However, they note that this drastic reduction may actually be a conservative value, the 12.11 fuse restoration jobs per hour rate may be higher in areas with inaccessible locations and that their calculations are dependent on storm path such that deviation lowers TLR reduction values.   

Fig. 2 

Citations

“Dominion Energy Strategic Underground.” YouTube, September 21, 2022. https://www.youtube.com/watch?v=UXc5VKML9SQ&t=190s.  

“Dominion Energy’s Strategic Underground Program Podcast – Episode 1.” YouTube, October 20, 2021. https://www.youtube.com/watch?v=rPCYxTZrLqY.  

“Dominion Energy’s Strategic Underground Program Podcast – Episode 10.” YouTube, October 18, 2022. https://www.youtube.com/watch?v=uLUfSYr9-8Q.  

“Grid Resiliency and beyond Podcast – Episode 1.” YouTube, January 24, 2023. https://www.youtube.com/watch?v=ResYdit59HQ.  

Guidelines for use of electric transmission rights of way. Accessed September 6, 2023. https://cdn-dominionenergy-prd-001.azureedge.net/-/media/pdfs/global/projects-and-facilities/electric-projects/virtual-open-house/dom-guidelines-use-electric-trans-right-of-way-easements.pdf?la=en&rev=5f9e323022bb47128055e56589f2ef9e&hash=3A9A29E23805F74A89A93470E3F171DA.  

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“Title 56. Public Service Companies.” § 56-466.2. Undergrounding existing overhead distribution lines; relocation of facilities of cable operator. Accessed September 6, 2023. https://law.lis.virginia.gov/vacode/title56/chapter15/section56-466.2/.  

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