Some Rivers Have a 31-Day Legal Window for In-Water Work

By Ed Brannigan, Marine contractor. Reviewed by Dana Whitcombe, technical reviewer.

Marine Construction | Boat Lift Installation October 15th, 2009. The Tar River was low and clear, and the permit nailed to the dock had one sentence highlighted: 'In-water work permitted from October 1 through October 31.' I had a vibratory hammer on the barge and a skid steer in the marsh, and we had 17 more feet of sheeting to drive before the window closed. The pile driver is loud, but the silence when you read a deadline like that is louder. That job was a bulkhead replacement for a marina in Greenville, NC. We'd bid it in June, assuming we could pile-drive anytime from spring to fall. But the North Carolina Wildlife Resources Commission had signed off on a 31-day window that ran through October, and after that, no underwater work. The water temp was still 62 degrees, and the stripers were staging downriver, but the law didn't care about the thermometer. We worked from first light to last light and made it by two days. That's the pattern on a lot of rivers from the Gulf to the Atlantic: a narrow, non-negotiable slot when you can touch the bottom. This post is about what that window actually means, why it's 31 days instead of a season, and how to keep your project from collapsing into the year after.

What a 31-day window is (and isn't)

A 31-day window is not a statewide blanket. It's written into your US Army Corps of Engineers permit or state water quality certificate. It specifies the exact dates when equipment can be in the water, not just the work area. On the Tar, it was October 1 through October 31. That means no disturbance of the riverbed outside those dates. The window is set so that adult fish aren't spawning, eggs aren't in the gravel, and larvae have moved out. It's a compromise between keeping a river alive and letting people build things on it. And it's non-negotiable.

Why 31 days? Follow the fish

Why 31 days? Follow the fish. On the Atlantic coast, anadromous species like American shad and river herring run up rivers in the spring. They spawn in freshwater, and the juveniles drop back down to the ocean in the summer. By October, the adults are gone and the hungry juvenile fish have moved out of the shallows. That's when you get a legal slice of time to disturb the bottom. In rivers with a longer migration—say, a multi-month run of blueback herring—the window might stretch to 60 days. In a river that's critical habitat for a listed sturgeon, you might get no window at all. The 31-day number is calibrated to the specific species in that specific river. It's also built around water temperature. If the river is too warm, spawning happens later, and the window shifts. The agency computes it from decades of riffle samples. The 31 days you're given are the days when the river is empty of the things we're trying to protect.

How to plan a project around a 31-day box

You don't schedule in-water work. You schedule around it. Step one: find the window before you bid. Call the state agency or check the Corps' public notice. Step two: stage everything on land before the window opens. I had sheets, wales, and piles stacked on the marsh by the end of September. Step three: have a second crew on standby if you're renting equipment. A broken packer costs you a day, and a day is a fourth of the window. Step four: define the boundaries. Does the window end at midnight on October 31, or at 5 PM? Does it allow you to drive a pile at 2 PM on the 31st, or is the last workday the 30th? Read the permit language. And know this: after the window closes, you can't even have a pump running in the river. The water must return to natural.

The cost of missing the window

I've watched a contractor eat a six-figure loss because he assumed the window was a formality. He drove a few piles on November 2. The state inspector showed up at 8 AM with a stop-work order. The fine was $25,000, the remaining piles had to be pulled, and the marina ended up doing the job the following summer with a cofferdam, doubling the cost. No grace period. No weather allowance. The permit doesn't include a 'project delay' clause. Some states do offer a variance for public safety—a failing bridge, a broken water main—but that process takes months and requires a public notice. You'll never get one approved after the fact.

Advice from 30 years of working to the calendar

Treat the window like a tide. It comes, it goes, and you better have your work done. You can extend a day with a lighting plant, but you can't extend a month with an excuse. When you're talking to a client, put the window dates in big red letters in the contract. If the owner wants a dock in May, you have to tell them: the permit says you get it in October, or not at all. That's not a project delay; that's a river's way of telling you who truly controls the schedule. After 30 years, I still call the agency before every job to double-check the dates. Because the one thing I've learned is that the river doesn't care about your plans. It only cares about the fish.

Frequently Asked Questions

Can I dry-ft a pile if I miss the window? No. If the pile touches the riverbed, it's in-water work. Some agencies allow work in the 'footprint' of an existing structure if you're replacing it, but that's rare and you need a separate authorization. Does the 31-day window apply to riprap and demolition too? Yes. Any activity that disturbs the bed or bank is covered. That includes dredging, pile driving, rock placement, and even removal of old materials. The only exception is if you're working from an existing pier and don't disturb the bottom. How do I find out the exact window for my river? Look at your Corps of Engineers permit conditions—it's usually in Section 6. Or ask the state environmental agency's water quality division. They'll tell you the species-specific dates. Don't rely on your subcontractor's guess.