Culverts and ditching

Vermont's permit chain for a culvert or ditch

Identify the road authority and the proposed use of its right-of-way. Under 19 V.S.A. §1111, the Agency handles State highways and the selectboard handles town highways. Confirm the applicable access or work permit and its actual conditions before excavation.

A stream crossing, wetland or floodplain can require additional review. Contact the regional River Management Engineer for the crossing and ask the applicable town and state offices about the site. Determine construction and maintenance responsibility from the road classification, permit and adopted policy rather than assuming that every driveway culvert has the same owner.

What culverts do differently

A culvert solves a different problem: it lets concentrated water, from a ditch, a stream, or a drainage swale, continue flowing underneath a crossing point like a driveway or road, so the surface above remains usable while the water passes through undisturbed below.

Culvert sizing is critical and often underestimated. A pipe too small for the actual flow volume during a significant storm will back up water on the uphill side, potentially flooding an area or, if the water finds another path, washing out the driveway or road surface entirely around the undersized pipe.

Why maintenance and sizing both matter

Both ditches and culverts need periodic maintenance, clearing accumulated sediment, leaves and debris that reduce their carrying capacity over time, since a feature that was correctly sized when installed can still fail if it's allowed to silt up or clog with organic material.

Sizing needs to account for realistic significant-storm flow, not typical conditions, because the whole point of these features is handling the concentrated water that shows up during heavy rain or rapid snowmelt. Undersizing for cost savings is a common mistake that shows its consequences during exactly the storms when reliable drainage matters most. Whose job the upkeep is, the homeowner's or the town's, is its own question with a specific Vermont statutory answer, not just a matter of who happens to notice the problem first.

Driveway culverts

Driveway culverts provide a passage beneath an access route where it crosses a roadside ditch or natural drainage path, keeping the driveway from blocking that flow. Installation involves excavating a trench across the driveway's width at the crossing point, setting a pipe at the correct depth and slope to match the ditch's existing grade, and backfilling and compacting before finishing the surface above. Getting depth and slope right matters as much as pipe size.

A culvert set too shallow risks being crushed by traffic, while one without adequate fall won't drain correctly and accumulates sediment faster. Many Vermont towns require a permit for this work, particularly where a driveway meets a town road, since the town wants the culvert to not compromise its own road drainage.

Checking first avoids a costly redo. Confirm the road owner’s access requirements.

Why a culvert is needed at a driveway crossing

Wherever a driveway crosses a roadside ditch or natural drainage swale, that water needs somewhere to go. A driveway built without a culvert either dams the flow, causing it to pool and potentially flood the ditch and surrounding area, or forces the water over the driveway surface itself, which erodes the material and undermines the structure over repeated storms.

This makes a culvert less of an optional upgrade and more of a functional necessity anywhere this crossing situation exists. Skipping it doesn't eliminate the water's need to flow, it just relocates the problem to wherever the water ends up going instead.

What installation involves

The process starts with excavating a trench across the driveway at the correct width and to the depth needed for both proper burial cover and matching the ditch's existing grade on both sides of the crossing, since the pipe needs to connect smoothly to the flow it's intercepting.

The pipe is set with adequate slope to keep water moving through instead of pooling inside it, then backfilled with appropriate material and compacted correctly before the driveway surface is finished above. Skipping proper compaction is a common shortcut that leads to settling and surface problems over the culvert later.

Depth, sizing and permits

Burial depth needs to provide adequate cover to protect the pipe from being crushed under vehicle loads, particularly for driveways that see heavier vehicles like delivery trucks or emergency vehicles. A shallow culvert under a residential driveway is more vulnerable than one correctly buried to standard depth.

Check with your town office before starting the work.

Check cover and the crossing type before buying pipe

The 2024 Better Roads Manual recommends 18–24 inches of fill over a culvert where possible in its perennial-stream installation guidance. Treat that as scoped guidance, not a substitute for the manufacturer’s load and cover requirements or a site-specific crossing design.

Before ordering, record the crossing type, existing inlet and outlet elevations, road and shoulder width, fill depth and expected traffic. If the crossing carries a stream, involve the regional River Management Engineer; aquatic passage and stream continuity are part of the design, not just storm capacity.

What size culvert do I need for my driveway?

It comes from the watershed feeding that specific crossing point, converted into an expected peak flow for a significant storm, never a generic off-the-shelf size regardless of how the crossing looks.

What happens if I don't install a culvert where one is needed?

The driveway either blocks the water's flow, causing it to pool and potentially flood the ditch and surrounding land, or the water flows over the driveway surface, eroding and undermining it over time.

Can I install a driveway culvert myself?

For a small residential driveway, it's within reach for some capable homeowners, though proper sizing, depth and slope matter enough that many choose a contractor experienced with local requirements.

What material should I use for a driveway culvert?

Corrugated metal or an HDPE-type plastic pipe are the two common choices, and the decision comes down to cost, expected vehicle loading, and whatever your town's specific requirements call for.

How much does it cost to install a driveway culvert?

Cost depends on pipe size, length, depth, and site access. The excavation cost guide breaks down typical Vermont ranges for this kind of work.

Can a driveway culvert be too big?

A larger pipe is not a complete design. Cover, fill stability, inlet and outlet elevations, stream continuity and aquatic passage still matter. Select the crossing with the road authority or River Management Engineer where applicable.

How do I know if my existing driveway culvert is failing?

Sediment buildup reducing flow, visible settling or cracking of the surface above it, or the pipe itself showing corrosion or a crushed section are all signs it's due for a closer look.

Does the slope of my driveway affect culvert installation?

Yes. The culvert needs to match the ditch's existing grade on both sides of the crossing to keep water flowing smoothly through it rather than creating a dam effect at either end.

Can a driveway culvert freeze in a Vermont winter?

It's possible in extreme cold if flow is minimal, though adequate burial depth and continued water flow through the pipe prevent this from being a routine problem for most installations.

Sizing a culvert

Sizing a culvert: correctly sizing a culvert starts with calculating the drainage area, or watershed, feeding water to that specific crossing point, the total land whose runoff reaches that ditch or stream at the crossing, since a larger contributing watershed means more water arrives during a storm, requiring a larger pipe regardless of how modest the crossing looks. From the watershed size, an engineer or experienced contractor estimates peak flow during a significant storm, using regional rainfall intensity data specific to Vermont, then selects a pipe diameter with capacity to handle that peak flow with a safety margin instead of sizing to the calculated minimum. Sizing needs the actual watershed, hydraulic conditions and crossing requirements.

Neither appearance nor a guessed minimum is sufficient. An undersized culvert works fine in normal conditions and fails exactly when it matters, during the storm it was never sized for. Getting this right upfront is far cheaper than replacing a washed-out driveway after failure.

Why watershed size, not crossing appearance, determines sizing

A crossing point that looks modest, a small ditch, a seemingly minor stream, can still be draining a large watershed area upslope, meaning it carries far more water during a significant storm than its everyday appearance would suggest. This is the core reason guessing culvert size based on how the crossing looks day-to-day is unreliable.

Calculating the actual contributing watershed area, done using topographic maps or on-site assessment by someone trained to identify drainage boundaries, is the necessary first step before any meaningful sizing calculation can happen. Skip this and every later number is a guess.

The minimums a Vermont town sets, and how to size above them

Vermont's model Town Road and Bridge Standards, which towns adopt as their own, set a minimum diameter of 15 inches for a new driveway culvert and 18 inches for a new roadway culvert, and the road foreman can require more. A driveway that joins a town road also needs an access permit that the road foreman approves. Check your town's adopted standard, because towns edit the model.

Above the minimum, size for the flow. The rational method estimates peak flow in cubic feet per second as Q = C x i x A, where C is a runoff coefficient (about 0.3 for woods and pasture, 0.9 for pavement), i is the design rainfall intensity in inches per hour from NOAA's Atlas 14 for the site and A is the watershed in acres.

Overtopping requires investigation: blockage, tailwater, inlet control, storm size and flow assumptions can all contribute. Do not diagnose the watershed error from overtopping alone.

From watershed to pipe size

Once watershed area is known, regional rainfall intensity data, how much rain a storm of a given significance produces in that specific area of Vermont over a given time period, is used to estimate peak flow volume the culvert will need to handle during that storm.

A pipe diameter is then selected with capacity exceeding that calculated peak flow by a reasonable safety margin, instead of sizing exactly to the calculated minimum, since real-world factors like partial blockage from debris or a slightly larger-than-designed-for storm both eat into a culvert's effective capacity over its service life.

Why undersizing is the costly mistake, not oversizing

Pipe diameter alone does not establish a sound crossing. Inlet and outlet control, cover, alignment, fill stability and aquatic passage can determine the structure and installation details. An undersized culvert, in contrast, performs fine during normal conditions, which is exactly what makes the mistake so easy to make and so easy to miss until it's too late.

The failure only shows up during the significant storm the culvert was supposed to be sized for, at which point water backs up, potentially floods the surrounding area, or finds another path around the crossing and washes out the driveway or road. A far more expensive fix than the modest extra cost of correct sizing would have been.

Can I size a culvert myself without an engineer?

For a small, straightforward residential driveway crossing, an experienced contractor can often size it reasonably well. A larger or more complex watershed benefits from formal engineering calculation.

What happens if I guess at culvert size instead of calculating it?

You risk an undersized culvert that performs fine in normal conditions but fails during the significant storm it should have been sized to handle, causing flooding or a washout.

Does a bigger watershed always mean a bigger culvert?

Yes, all else equal. More contributing drainage area means more water reaches the crossing during a storm, which the culvert needs sufficient capacity to handle.

How much of a safety margin should a culvert have above calculated flow?

This varies by specific project and local practice. Sizing with some margin above the bare calculated minimum accounts for real-world factors like partial debris blockage that reduce effective capacity over time.

Is it worth paying for engineering to size a culvert correctly?

Yes. The modest additional cost of proper sizing calculation is far cheaper than replacing a washed-out driveway or road after an undersized culvert fails during a significant storm.

Does climate change affect how culverts should be sized in Vermont?

Some current guidance accounts for trends toward more intense storm events, which is worth discussing with whoever is doing your sizing calculation instead of relying solely on older historical rainfall data.

Can an existing culvert be resized without full replacement?

Not really. If an existing culvert is undersized, the practical fix is replacing it with a larger pipe instead of modifying the existing one. Capacity is fundamentally set by pipe diameter.

How do I find out my property's watershed area?

A contractor or engineer can assess this using topographic maps and on-site evaluation, identifying the drainage boundaries that determine how much land contributes runoff to your specific crossing point.

Does culvert length affect sizing along with diameter?

Length affects installation cost and some flow characteristics. But diameter, driven by calculated peak flow capacity, is the primary sizing factor. Length is more about the specific crossing's width.

Roadside ditches and water bars

Roadside ditches and water bars: roadside ditches are graded open channels running alongside a road or driveway, intercepting surface runoff before it can flow across and erode the road surface, carrying that water along a controlled path to a discharge point or culvert crossing. Water bars are a related feature: small diagonal ridges or channels built across a driveway, road or trail to divert surface water off to the side at intervals, preventing it from gathering volume and velocity as it runs down a slope. On a town-maintained road, ditch maintenance is the town's job.

On a private driveway, it falls to the owner. A neglected ditch that fills with sediment loses capacity and can back water up onto the ground it was meant to protect. Water bars are important on a steep, unpaved Vermont driveway or road, since without them, runoff gains speed and erosive power running straight downhill, cutting ruts and washing away surface material that's expensive to keep replacing.

What ditches do and why they need upkeep

Diverting runoff into a maintained ditch protects the road material from erosion, which is a significant factor in how long an unpaved rural road or driveway lasts.

Sediment, fallen leaves, and vegetation growth all gradually reduce a ditch's carrying capacity over time, so periodic clearing, ideally before spring runoff and after major storms, keeps the ditch performing at its designed capacity instead of allowing gradual degradation to go unnoticed until it causes an actual flooding or erosion problem.

What water bars specifically solve

On any sloped, unpaved surface, water running straight downhill gains speed and volume as it travels, and that increasing velocity is what gives it the erosive power to cut ruts, wash out surface material, and eventually create serious, expensive-to-repair damage. Water bars interrupt this process by diverting the flow off to the side at regular intervals before it can build up damaging speed.

They're built as small diagonal ridges or shallow channels angled across the sloped surface, and their spacing and angle matter. Too far apart and water still gains too much speed between bars. Poorly angled and they don't effectively redirect flow off the road or driveway surface.

Who's responsible and what neglect costs

On a public, town-maintained road, ditch maintenance falls to the town as part of its road maintenance responsibilities. On a private driveway or road, which covers most individual Vermont properties beyond where they meet a town road, the property owner is responsible for maintaining their own ditches and water bars.

Neglecting this maintenance doesn't just risk a single dramatic failure. It's more often a gradual degradation where a slowly filling ditch or missing water bars lead to incrementally worse erosion each season, until what would have been a simple annual clearing job becomes a significant, costly repair or reconstruction project.

Why does my steep driveway keep eroding?

It likely lacks adequate water bars or ditching to divert runoff before it gains damaging speed running straight downhill. This is one of the most common causes of ongoing erosion on sloped, unpaved surfaces.

How far apart should water bars be spaced?

Spacing depends on the slope's steepness and length. Steeper grades need more frequent water bars to prevent runoff from building up too much speed and volume between them.

Can I install water bars myself?

For a straightforward driveway, a capable homeowner can install basic water bars, though getting the angle and spacing right for effective diversion benefits from some experience or guidance.

What happens if I don't maintain my driveway's ditches?

They gradually fill with sediment and vegetation, losing capacity over time, which can eventually cause water to back up onto the driveway surface itself rather than being carried away as intended.

Does Vermont require water bars on steep private driveways?

Requirements vary by town and specific circumstances, particularly for new driveway permits on steep grades. Check with your local town office for any applicable requirements.

Can a poorly maintained ditch damage a road's foundation?

Yes. Water that should have been carried away by a functioning ditch instead saturates the road base or surface material, weakening it and accelerating the road's overall deterioration.

Is there a difference between a water bar and a culvert?

Yes. A water bar diverts surface water off a sloped surface at intervals. A culvert lets concentrated water pass underneath a crossing point. They solve different, though related, drainage problems.

How do I know if my ditches are correctly sized?

If they're regularly overwhelmed during normal rainstorms, backing up water onto the road or driveway, they may be undersized for the actual drainage area feeding them. A contractor can assess and recommend resizing if needed.

Can erosion from poor ditching affect my septic system?

Indirectly, if the erosion or resulting saturation reaches near the septic system's location. Overall property drainage, including ditches and water bars, is part of protecting the septic system's surrounding conditions.

Headwalls and outlets

Headwalls and outlets: a headwall is a structure, concrete, stone, or a manufactured end section, built at the inlet or outlet end of a culvert to serve two related functions: stabilizing surrounding soil against erosion where the concentrated flow enters or, especially, exits the pipe, and improving hydraulic performance by smoothing flow into and out of the pipe instead of letting it churn against unstabilized earth. Outlet erosion is the more common concern in practice, since water exiting a culvert moves with concentrated velocity and, without protection, can scour out surrounding soil, undermining the pipe over time or creating a growing erosion gully downstream. Not every installation needs a formal engineered headwall, a smaller, lower-flow driveway culvert might be adequately protected with simple riprap (placed stone) at the outlet, but larger culverts, those on steeper grades with higher outlet velocity, or ones where erosion has already become visible, benefit from or require more substantial headwall protection.

Why the outlet end is the bigger concern

Water exiting a culvert has been concentrated and often accelerated by its passage through the pipe, meaning it hits the ground at the outlet with more erosive energy than the same volume of water would have spread across a natural channel. This concentrated force is what makes outlet erosion, sometimes called scour, a common and progressive problem if left unaddressed.

Left unprotected, this scouring can progressively undermine the soil supporting the culvert pipe itself, potentially compromising the crossing's structural stability over time, in addition to creating an expanding erosion gully that becomes its own separate problem downstream of the original crossing.

When a Vermont site needs outlet protection, and what it costs

Identify the crossing authority. Check its inlet and outlet requirements. The actual access and stream authorizations determine the required protection; one universal headwall detail cannot be assumed.

Ice blockage, scour and movement can damage an inlet or end section. Specify the foundation, bedding, anchorage, erosion protection and outlet under the selected design and the road authority’s requirements. Compare the complete crossing scope.

Include excavation, pipe, end treatments, traffic arrangements and restoration. A pipe-only price omits much of the work.

What headwall protection looks like

For smaller, lower-flow installations like a modest residential driveway culvert, simple riprap, placed stone sized appropriately to resist being moved by the expected flow velocity, at the outlet is often adequate protection against erosion, providing a stable, energy-dissipating surface for water to exit onto.

Larger culverts, installations on steeper grades where water exits with higher velocity, or crossings that have already shown erosion problems benefit from more substantial engineered headwall structures. Poured concrete or precast concrete end sections specifically designed to stabilize the soil and manage the higher-energy outflow.

When it's worth the added cost

The decision to invest in a more substantial headwall versus simpler riprap protection comes down to the specific site's flow characteristics and consequences of erosion. A larger watershed feeding a higher-velocity outlet, or a location where erosion could threaten a structure or significant infrastructure, justifies the added upfront cost.

A site already showing signs of outlet erosion, a growing gully, exposed or undermined pipe, is past the point of preventive consideration and needs remediation now, since ongoing scour will continue to worsen and become more expensive to fix the longer it's left unaddressed.

What is riprap and when is it used instead of a headwall?

Have the designer specify stone size, placement and the downstream transition for the expected flow. Loose stone selected by appearance alone is not a drainage design. It's a simpler, often adequate alternative to a full headwall for smaller culverts.

How do I know if my culvert outlet needs better erosion protection?

Visible signs like a growing erosion gully, exposed pipe, or undermined soil at the outlet indicate existing protection is inadequate and needs upgrading before the problem worsens further.

Can outlet erosion damage the culvert pipe itself?

Yes. Keep people and vehicles away from a visibly undermined crossing. Have the outlet, supporting ground and erosion protection assessed before placing more fill over the problem.

How much does a headwall cost?

Cost varies significantly with size and material. Simple riprap protection is relatively inexpensive, while a substantial engineered concrete headwall for a larger culvert costs considerably more.

Does the inlet end of a culvert need protection too?

Sometimes, though it's a lesser concern than the outlet since water entering the pipe hasn't yet been concentrated and accelerated the way it has by the time it exits.

Can I add riprap or a headwall to an existing culvert without erosion protection?

Yes. Retrofitting erosion protection to an existing culvert outlet is a common and worthwhile repair, especially if erosion has already started to become visible.

What determines whether I need riprap or a full headwall?

Flow velocity at the outlet, driven by watershed size and the grade the culvert sits on, along with the consequences if erosion did occur. Higher-stakes or higher-flow situations warrant more substantial protection.

Can a headwall improve how well a culvert functions?

Yes, to some degree. A correctly designed headwall can smooth water flow into and out of the pipe, slightly improving hydraulic performance in addition to its primary erosion-protection role.

Should I hire a professional to assess my culvert's erosion protection?

For any culvert showing signs of erosion, or a larger installation with significant flow, yes. A professional can assess actual conditions and recommend appropriately sized protection instead of guessing.

Who's responsible for a driveway culvert

Who is responsible for a driveway culvert in Vermont depends on its function and the conditions of the access permit for the access. Installing or altering a driveway culvert in a town road's right-of-way requires a written permit from the selectboard under 19 V.S.A. sections 304(a)(21) and 1111, and most towns attach driveway-access or curb-cut standards to that permit covering drainage and slope. The property owner builds and maintains the culvert under those conditions.

The town's responsibility runs to the roadside ditches and culverts carrying the road's drainage, not the private driveway crossing serving one property. A town-culvert damage claim depends on the applicable repair duty and statutory limitations; section 987 requires timely signed written notice.

Retain incident and notice-delivery records for advice on an actual claim. Road class matters too: Class 1-3 highways carry state-funded maintenance standards; Class 4 roads and trails get less, and a trail gets no town maintenance obligation at all.

The permit that makes the driveway culvert legal

Any construction, installation or alteration of a driveway, ditch, culvert, fence or other structure inside a town road's right-of-way needs a written permit from the town selectboard, under 19 V.S.A. sections 304(a)(21) and 1111. That includes the driveway culvert itself, since the crossing sits inside the strip of land the town controls even though the driveway beyond it is private property.

Most towns fold specific driveway-access or curb-cut standards into that permit. Covering drainage (proper culvert installation and slope) and safety (sight lines, angle of entry, distance from intersections). The permit is what the selectboard uses to make sure a new driveway culvert doesn't compromise the road's own drainage system, which is the town's actual interest in the crossing.

Who builds and maintains it, versus who owns the road it sits under

The right-of-way belongs to the town, but a driveway culvert crossing within it exists to serve one property, not the traveling public. Under the permit conditions most towns issue, the property owner is the one who builds the culvert to the town's specified standard and who then maintains it, clearing debris, watching for settling, replacing it if it fails, since it is the private driveway's own drainage structure, not part of the road's drainage system.

The town's maintenance obligation runs to the roadside ditches and culverts that carry the road's own drainage along and across the highway, which is a separate structure from the driveway crossing even where the two sit close together. Confirm which is which with your specific town before assuming either way, since the exact line can be written into a town's own highway ordinance or curb-cut policy instead of being identical everywhere.

When the town is liable for a culvert problem

A defect nobody could reasonably have known about doesn't create town liability merely by happening on a town road.

Damage from driving a vehicle over the posted weight limit across a bridge or culvert is excluded from town liability entirely, regardless of the culvert's condition.

Why the road's class changes what to expect

Vermont divides town highways into four classes, and the class determines how much maintenance a road, and the culverts and ditches serving it, gets. Class 1, 2 and 3 highways carry state highway aid tied to the town meeting real maintenance standards, under 19 V.S.A. section 306, so culvert and ditch upkeep on those roads is comparatively predictable.

Class 4 roads are maintained only to the extent the town's own necessity, the public good and residents' convenience call for, which many towns spell out in a written Class 4 road policy rather than leaving to case-by-case judgment. Trails are a separate category again. The town has no maintenance responsibility on a trail at all, culverts and bridges included, under 19 V.S.A. sections 301(c) and 302(a)(5), so a driveway off a trail gets no town drainage support whatsoever.

A damage notice needs more than the date

Section 987 specifies a signed written notice to one or more selectboard members within 20 days, identifying when and where the damage occurred, the alleged bridge or culvert insufficiency and the claim for satisfaction. Contact an attorney promptly if making a claim; this deadline is not a guarantee of recovery.

The section excludes recovery for crossing with a vehicle exceeding legal or posted weight limits. Keep photographs, the location, incident records and any permit or maintenance correspondence without entering unsafe water or a damaged crossing.

Is the town liable if my car is damaged by a bad culvert on a town road?

A potential claim depends on the town’s repair duty and the limitations in 19 V.S.A. sections 985 and 987. Section 987 requires signed written notice to a selectboard member within 20 days, identifying the time, place, alleged insufficiency and intent to seek satisfaction; it also addresses vehicles over legal or posted weight limits. Obtain advice on the actual incident rather than assuming a maintenance responsibility guarantees recovery.

Does a Vermont town have to fix a culvert on a Class 4 road?

Class 4 roads are maintained only to the extent the town's necessity, the public good and residents' convenience require, which is far less predictable than Class 1-3 highways. Ask the town for the road classification and applicable maintenance policy before arranging work or assuming a public maintenance obligation.

Is a Vermont town responsible for maintaining culverts on a trail?

Do not assume a trail comes with town culvert maintenance. Confirm its recorded highway classification and the responsible party before planning repair or replacement. A driveway off a trail gets no town drainage support.

What Vermont law requires a permit for driveway access to a town road?

19 V.S.A. sections 304(a)(21) and 1111 give the selectboard authority to issue right-of-way permits for driveways, culverts, ditches and similar structures, and most towns attach their own drainage and safety standards to that permit.

Can a Vermont town revoke my driveway access permit later?

Yes, in some circumstances. 19 V.S.A. section 1111(f) authorizes a selectboard to eliminate previously permitted access and require a shared or common frontage road as a condition of a new permit as an area develops further.

How long do I have to report culvert damage to a Vermont town?

Written notice needs to reach a member of the selectboard within 20 days of the incident, or the town cannot be held liable for the damage under 19 V.S.A. section 987, regardless of whether the culvert was defective.

Does Vermont town culvert liability cover damage from an overweight vehicle?

No. Damage suffered from crossing a bridge or culvert with a vehicle over its posted weight limit is specifically excluded from town liability under 19 V.S.A. section 987, no matter the culvert's condition.

What's the difference between Class 1, 2, 3 and 4 town highways in Vermont?

Classes 1-3 receive state highway aid tied to the town meeting real maintenance standards under 19 V.S.A. section 306; Class 4 roads get discretionary maintenance based on the town's own necessity and the public good, often set out in a town policy.

Does my town's driveway culvert permit tell me how to maintain it?

Often yes. Many towns fold driveway-access or curb-cut standards into the permit, covering how the culvert must be installed (drainage, slope) even though ongoing upkeep afterward is the property owner's job.

Where do I find my town's specific driveway culvert or curb-cut rules?

The town's highway ordinance or a separate curb-cut policy adopted by the selectboard is where these standards are written. The town office or town clerk can provide a copy before you apply for a permit.