Repairing Culverts in a Post-Irene World

Top: The North Hollow Road culvert was damaged during Tropical Storm Irene. Bottom: This newly installed culvert is a 50-foot-long pipe arch that is over 15 feet wide, allowing for fish passage and deemed large enough to handle high-water events. Photos by Greg Russ.

All too often, discussions about culverts center around two different objectives. There’s the practical side: designing and sizing a structure that will protect roads. And then there’s the ecological side: what role this obstruction plays in the lives of fish and other wildlife seeking passage up- or downstream. As environmental consciousness has developed over the decades, these goals have come to overlap, but few towns can afford to replace functional culverts with more expensive animal-friendly ones.

Things changed, though, in the wake of Tropical Storm Irene, when massive culvert failure forced towns throughout New England and New York to pay a lot more attention to the pipes under the roads. As towns pick up the pieces, an opportunity to reconsider culvert design has arisen, and people are realizing what’s in the best interest of fish may also be in the best interest of towns.

The rub is still, of course, money. The Federal Emergency Management Agency (FEMA) has funds available to applicants affected by the storm for in-kind replacements (replacing culverts to their pre-storm status), which makes sense from a penny-pinching perspective, but is sort of like replacing a bald tire that blew out on your car with another bald tire. Bigger, better culverts that allow fish to move as needed and can handle high-water events cost a great deal more and can strain towns’ already thin budgets.

The town of Rochester, Vermont, is working around the funding challenges by teaming up with the White River Partnership (WRP) – a nonprofit organization formed to improve the health of the White River watershed – and the U.S. Fish and Wildlife Department, which has access to additional federal funding. (Most notable is the National Fish Passage Program, a federal program with a $126 million annual budget that’s designed to chip away at the estimated eight million barriers to fish that exist nationwide.)

Prior to the storm, WRP had identified three top-priority culverts that were barriers to brook trout and in need of redesign. Over the years, spring floodwaters had rushed through undersized pipes like a fire hose, eroding the riverbed and causing the water level to drop until the culverts perched several feet above the surface, preventing fish from getting upstream to spawn.

Project manager Greg Russ walked me through the process, using a culvert on Rochester’s Marsh Brook as an example. The pre-flood structure consisted of two 36-inch culverts, installed side by side, crossing under North Hollow Road. They blew out during Irene, damaging both the surrounding roads and the brook. As Russ explained, the town had three options (see below):

Rochester decided on Option 3. Before the project began, U.S. Fish & Wildlife Service fisheries biologists electroshocked fish downstream of the project site. They marked 100 stunned brook trout by clipping the back fin. About two weeks after the project was completed, the biologists went back to the site and shocked fish both in the culvert and upstream about 100 feet. The group found three brook trout in the culvert, and another 15 upstream. Of the 18 fish, 10 had the clipped fin, meaning that fish passage through this culvert has been restored.

So how does this culvert work stack up to other such projects in the Northeast?

“Other towns are replacing [culverts] to the FEMA project worksheet standards,” Mary Russ, WRP’s executive director, said. “We’ve gotten calls from at least three other towns that want to be part of our program. Many have experienced two floods in the past four years and are replacing the same roads and culverts that have washed out before. They understand that culverts built to the town’s codes are not big enough to handle high water events.”

Not every town has the extra money, or political will, to pursue such upgrades, but the Rochester project serves as a good example of the costs involved and the potential benefits of larger, more fish-friendly culvert design.

“Rivers and streams are systems that move more than water; they’re not just ditches,” said Greg Russ. “We have national infrastructure problems, but if we’re smarter about how we replace things, we’ll be better off.”

Option 1

The Status Quo: FEMA replaces like with like.
Description: Replace two damaged 36-inch, 50-foot-long culverts with two new 36-inch, 50-footlong culverts.
Culvert Cost : $8,000
Total Project Cost : $18,000
Cost to Town: $900*
Pro: Lowest cost option.
Con: Barrier to fish; doesn’t allow sediment or debris to pass; undersized structure at risk of failure during future high-water events.

Option 2

The Partial Resilient Upgrade: FEMA uses 406 Hazard Mitigation** to upgrade culvert to meet Vermont codes and standards.
Description: Replace two damaged 36-inch, 50-foot-long culverts with one 60 inch, 50-foot-long culvert.
Culvert Cost : $11,000
Total Project Cost : $21,000
Cost to Town: $1,050*
Pro: Increase hydraulic capacity to the maximum flow expected in the next 25 years.
Con: Barrier to fish; doesn’t allow sediment or debris to pass; undersized structure at risk for failure during future high-water events.

Option 3

The Flood Resilient Upgrade: Project partners use outside funds to upgrade culvert to the Vermont Agency of Natural Resources General Stream Alteration Permit guidelines.
Description: Replace two damaged 36-inch, 50-foot-long culverts with a 15-foot, 4-inch-wide, 50-foot-long pipe arch (a “squashed pipe,” where the bottom buried portion is flatter) buried 3 feet; rebuild stream bed through the new culvert using US Forest Service Stream Simulation protocols.
Culvert Cost : $19,000 ($11,000 of the culvert cost will be paid by FEMA; project partners pay the balance of $8,000.)
Total project cost : $65,000 (including a $19,000 culvert + $46,000 for construction, road rebuild, and inlet/outlet riprap costs; $26,000 of the total cost will be paid by project partners).
Cost to Town: $1,950 (5% of the $39,000 balance; FEMA pays rest of balance)
Pro: No longer a barrier to fish; culvert sized to handle sediment, debris, and future flood events.
Con: Expense. Takes longer to design and implement than Options 1 and 2.

*Town cost = 5% of FEMA project worksheet, which includes the cost of the culvert and installation.
**406 Mitigation occurs when a federal disaster is declared and FEMA provides additional funds to improve the facility’s ability to resist similar damage in the future.

 
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