Project to rebury Wind Farm cables complex, costly
Ed. Note: With the project to rebury two sections of undersea cables about to get underway, The Block Island Times reached out to Block Island Wind Farm owner Ørsted, and National Grid, about the scope and complexity of the endeavor. Interview conducted by email by Lars Trodson. National Grid’s questions were answered by Ted Kresse, Director, Strategic Communications and Ørsted spokesperson Meaghan Wims.
BIT: Has a specific start date for the cable reburial been set?
NG: Teams from both National Grid and Ørsted are beginning to mobilize to the Island, with the staging of equipment and arrival of barges that will be used to replace the cables’ shore landings. The Horizontal Directional Drilling (HDD) and land-based conduit construction work at Town Beach is scheduled to begin in November and continue into December or January. The Ørsted HDD will occur first, followed by the National Grid HDD. This will create the new conduits (pipes) needed for the cable construction. The cable installation is scheduled to begin in late winter or early spring.
Ø: Ørsted’s scope of work will begin on October 15. All of the work will be conducted during the offseason. We are scheduled to finish the work prior to Memorial Day next year.
The drilling phase of the construction work at Town Beach is scheduled to begin this fall, with the near shore-based cable installation scheduled to begin in early spring.
As a reminder: The work entails replacing a segment of the cable, located from beneath the Town Beach parking lot out to roughly 3,100 feet offshore, with a new section that will be located adjacent to where the existing cable now sits. We will use a HDD process to reinstall the cable segment. HDD allows us to bury the cable even deeper – of about 30 feet - as compared to the current approximately four to eight feet – and it’s a common procedure for submarine cables such as this one. This is the right approach to address the recent challenges around sediment coverage over the cable.
The new cables will be spliced onto the existing cable that connects the island, the wind project and the mainland. The existing portions of the exposed cables are scheduled to be removed at the end of construction.
BIT: What is the cost estimate for National Grid’s portion of the project?
NG: The current estimate for National Grid’s work remains around $30 million.
Ø: Ørsted is taking sole responsibility for paying for this work. Ratepayers will not bear any of these costs. We are not disclosing our costs.
BIT: How many workers do you estimate, or know, will be working on the project? Will there be crews dedicated to specific jobs on the project?
NG: There will be roughly three dozen workers on-site assisting with the project.
Ø: We expect 20 to 30 people will be on shift at any one time.
BIT: Will the crews be working nights and on the weekends? (That was suggested early on to reduce the project’s timeframe.)
NG: During the HDD and cable phases of the project, most of the work will be done 24 hours per day, seven days a week. This is partially because some of the construction processes don’t lend themselves to interrupted construction, to try and avoid the worst part of the winter for at-sea work, and to maximize the ability to complete the project before summer 2021.
Ø: The operation will be 24 hours/seven days, working until completed.
BIT: How will the work crews be coordinated between Ørsted and National Grid? Both companies are working in close proximity and essentially trying to accomplish the same thing. Will you be sharing workers? Equipment?
NG: Ørsted and National Grid are in close coordination on both projects, including using the same contractor for the HDD.
Ø: We are working collaboratively with National Grid. The work will be sequential between the two projects. The crews will be the same for the HDD and onshore work, with separate teams for the cable installation.
BIT: While a small section of the cable was exposed a couple of years ago, has National Grid been tracking whether its cable has been exposed since then?
NG: We continue to monitor the cable for potential exposures. We have not had any additional exposures since the issue that arose in August 2018. For some time now, the cable has not been visible at Crescent Beach.
Ø: Ørsted has been monitoring the cable since the initial exposure and the cable has remained buried.
BIT: Are there any specific obstacles that National Grid engineers have identified that will pose a particular challenge for the on-site crews?
NG: Once the HDD begins, we will be drilling through a material referred to as “glacial till”, which is a mixture of sand, cobbles, boulders, and other materials that the glaciers left behind. This is one of the more difficult materials to drill through because of the mix of hard and soft materials. The contractor will be equipped with special drilling equipment to deal with this material.
Ø: The directional drill will be through glacial deposit, which is challenging but achievable.
BIT: Can you give us a glimpse into the equipment and materials that will be needed to complete the project?
NG: The effort includes replacing approximately 1,700 feet of National Grid’s sea2shore submarine cable that carries electricity between Block Island and mainland Rhode Island. In the next few weeks, teams for both National Grid and Ørsted will begin staging material and equipment to the island. There will be several barges brought to the island. Two barges and support boats will be staged off Crescent Beach for the HDD work. A support barge and smaller “work boats” will be staged in the Old Harbor to transfer material and workers from land to the offshore site. In the Fred Benson Beach Pavilion parking lot, a Horizontal Drilling Machine will be set up along with support equipment. The cable landings will be constructed using a horizontal directional drill (HDD), a common procedure for submarine cables such as these. The HDD will bury the cables at a depth of between 25 to 50 feet below the seafloor, as compared with the current four to six feet. This is deep enough to withstand changing ocean floor conditions and provide a continued reliable interconnection for Block Island and the Block Island Wind Farm for years to come. In the late winter/early spring, a different barge and cable handling ship will be brought to the island for the cable work. The new cables will be spliced onto the existing cable that connects the island, the wind project and the mainland.
Ø: There will be an onshore drilling rig in the southern Parking Lot on Corn Neck Road and an offshore rig stationed at the cable entry, also with a drilling rig onboard. Following the completion of this work, a cable installation vessel will arrive on site.
BIT: Will the project pose any specific traffic issues on Corn Neck Road or public access to the beach?
NG: Because of the size of the Horizontal Directional Drill Rig, we anticipate some impacts to the northbound lane of Corn Neck Road during the HDD process, primarily in November and December. We are in discussion with the town and R.I. Department Of Transportation over traffic mitigation plans. Alternating traffic may be necessary on Corn Neck Road during this time. Access to the beach will still be available, although some areas of the beach parking lot will be used for staging areas, which has been coordinated with the town.
Ø: We have requested a lane closure on Corn Neck Road during drilling. Access to the beach will be available for 10 cars in the southern parking lot.
BIT: Are there any specific health or safety issues that the public ought to be aware of during the work phase of the project?
NG: With any construction project, the public’s health and safety is a top priority for us. Any potential areas of caution will have proper signage posted warning the public of the construction zone.
Ø: The site will be secured and monitored. A section of the beach will be closed during a short period of time when we are fusing the pipe beneath the beach. In addition, all work crews will follow CDC COVID-19 guidelines regarding social distancing, masks and hygiene.
BIT: Is the spring 2021 timeline still in play for completion? Is the project planned out in phases? If so, can you tell us what those might be?
NG: Construction related activities will be ongoing throughout the fall and winter, with an anticipated completion date before Memorial Day 2021. Most of the HDD work will come in late fall and winter. Cable work will occur in spring 2021. Block Island and Rhode Island will continue to receive electricity from the wind farm during the construction, except for a brief outage in the spring, when the new cable will be spliced with the existing cable. During the National Grid cable and Block Island Wind Farm outage, Block Island Power Company (BIPCo) will provide the needed electrical power to the island utilizing its on-island diesel generation.
BIT: Does National Grid see any challenge in acquiring all the equipment and supplies it will need for the project?
NG: At this time, we do not foresee delays in acquiring the equipment and supplies needed. We’re hopeful that the pandemic will not impact the schedule.
Ø: All equipment and supplies have been procured and the project is on schedule.
BIT: Does the town of New Shoreham have any role to play to assist with the project in any way while it is ongoing?
NG: The town has been extremely cooperative in helping us coordinate the project and we thank them and the New Shoreham residents as we work to get the project completed before next summer.
Ø: The New Shoreham Town Council and Town Manager have been a great support to the projects and we have been in constant dialogue with them from the beginning. The town will provide updates to the community as the project continues.
BIT: There are two companies involved, so how is the project being managed? Co-managed or do you have a single project manager?
NG: There are project teams for both National Grid and Ørsted that meet regularly to discuss planning, next steps and coordinating with the construction team. We will also have weekly meetings with the town to keep them up to date on the work.
BIT: Is there anything that you would like to emphasize that we may have missed?
NG: We appreciate the R.I. Coastal Resources Management Council’s and Rhode Island Department of Environmental Management’s time and responsiveness on the permitting process to allow us to move forward as quickly as possible. National Grid and Ørsted also have worked in close collaboration with the Town of New Shoreham and the U.S. Army Corps of Engineers to receive the necessary permits and to keep stakeholders informed of the plans. Addressing the cable burial depth is a major priority for us, and, despite the pandemic, we are still on track to having it completed in time for next summer.