Block Island's cable enters its second decade

How the link actually works

If you live year round in the town of New Shoreham, or just spend summers out on Block Island, your lights now run on the same mainland grid that serves Providence and Westerly. That changed in the winter of 2016, when a submarine cable (an insulated power line laid along the sea floor) tied the island to the Rhode Island coast for the first time. Before that, the island made its own power with diesel generators, and paid some of the highest electric rates in the country for the privilege. The cable, built alongside the five-turbine Block Island Wind Farm (roughly 30 megawatts total, by the developer's public figures), is now ten years old and quietly carrying the island's whole supply.

The line most people mean is the Block Island Transmission System, sometimes called sea2shore. It runs roughly 20 miles, by public descriptions, from the island to a landing near Scarborough Beach in Narragansett and on to a mainland substation. It is a single circuit that moves power both directions: the island draws from the mainland most hours of the year, and the wind farm's output flows the other way when the wind is up. One circuit means there is no built-in redundancy, which is the backup path that takes over on its own if the main one fails. If that cable goes down, the island does not get a second wire. It gets its old diesel plant back.

The honest math on one cable

A buried marine cable is engineered to last a long time, commonly quoted at something like 25 to 40 years, so ten years in it is not old, but it is no longer new either. Age alone is not the real worry. The shallows are. Near the island's beaches the export cable became exposed where the sand shifts, and crews had to rebury sections, at last public report to Rhode Island regulators. Sand moves, storms rearrange the bottom, and the parts of the route closest to shore are the parts most likely to need attention.

A second cable would buy true redundancy, and there is no public commitment to build one. So the plan leans on inspection, scheduled maintenance windows, and keeping the diesel units ready. Whether that is enough depends on one number nobody can promise in advance: how fast a damaged subsea cable can be fixed. Marine cable repair can take weeks, sometimes months, depending on the specialized vessel being available and the weather over Block Island Sound cooperating. For a nor'easter in February, neither is a safe bet, and that is exactly why the old generators still turn over.

What the diesel years taught

For decades the Block Island Power Company ran diesel generators to keep the island lit. They were reliable in the narrow sense that they almost always ran, and miserable in every other sense: loud, expensive, and burning something on the order of a million gallons of fuel a year by the company's past public accounts. Residents who were here before 2017 remember the rates and the hum. The cable did not just lower the bill. It changed what the island's power felt like day to day.

The lesson islanders tend to repeat is a plain one: backup you own beats backup you only assume. The diesel plant staying in service is not nostalgia. It is the island's insurance policy against its single wire, and it is the reason a long cable outage would be a hardship rather than a disaster. That makes a boring question, whether those generators stay maintained and fueled, one of the more important ones a New Shoreham ratepayer can ask.

Worth watching this month

1. Watch ISO New England's winter outlook and any cold-snap alerts for the regional grid, which is routine seasonal business but worth a glance before a hard freeze.

2. Watch for the state's distribution utility, Rhode Island Energy, to file any Block Island reliability or capital plan at the Rhode Island Public Utilities Commission, with no date set and nothing guaranteed to appear.

3. Watch for scheduled cable inspection or maintenance windows announced for the sea2shore line, most of which are routine and planned well ahead.

4. Watch the nor'easter and coastal storm forecasts through late fall, since the near-shore cable segments are the ones weather tends to expose.

5. Watch whether the diesel generators get run for a test or an actual fallback this winter, a small sign that the island's backup is being kept honest.