The Old Croton Aqueduct Easement: What Westchester Homeowners Need to Know

Permits & Code
Written By Brandon Cavanagh
WESTCHESTER RIVERTOWNS The Old Croton Aqueduct Easement What Westchester homeowners need to know before renovating, building, or buying near the path DESIGN AND BIZ

There is a narrow strip of New York State Parks right-of-way running continuously down the spine of the Westchester Rivertowns. It crosses through the backyards of houses in Croton-on-Hudson, Ossining, Briarcliff Manor, Sleepy Hollow, Tarrytown, Irvington, Dobbs Ferry, Hastings-on-Hudson, and Yonkers. Many of the property owners whose deeds it crosses do not know it is there until they try to put up a fence, build an addition, regrade a driveway, or sell the house — at which point the easement quietly becomes the most consequential regulatory layer on the project. This guide walks through what the Old Croton Aqueduct easement actually is, what it restricts, who reviews work within it, and the practical implications for any Westchester homeowner whose property touches the path. (For the broader Westchester permits and code reality these aqueduct-related rules fit inside of, see our 2026 Westchester renovation permits and code guide.)

What the Old Croton Aqueduct Actually Is

The Old Croton Aqueduct was constructed between 1837 and 1842 to carry drinking water from the Croton River in northern Westchester to reservoirs in Manhattan. It is an elliptical tunnel approximately 8.5 feet tall by 7.5 feet wide, constructed of iron piping encased in brick masonry, running 41 miles south almost entirely by gravity flow at a slope of about 13 inches per mile. When it opened on October 14, 1842, it was the first major public water supply for New York City and one of the largest civil engineering projects in the country to date. It was decommissioned as a drinking water source in 1955, after the New Croton Aqueduct (opened 1890) and later supply infrastructure replaced it.

In 1968 the northernmost 26 miles of the corridor (from Croton Gorge Park south to the Yonkers / New York City line) was transferred to New York State and became the Old Croton Aqueduct State Historic Park, administered by the Taconic Region of the NYS Office of Parks, Recreation and Historic Preservation. The aqueduct tunnel itself is largely intact underground. The surface above the tunnel was developed over time into a continuous 26.2-mile public trail — popular with walkers, runners, and cyclists — that traces the original route through Westchester. The aqueduct was designated a National Historic Landmark in 1992.

The Easement, Not the Path

The aqueduct trail you see on the surface is the public-facing piece of a larger legal arrangement. The State of New York holds a permanent right-of-way along the route of the tunnel through hundreds of private parcels. The width and configuration of the protected strip vary by parcel — defined by the original recorded easement documents for each property. The underlying land within that strip is, in most cases, still owned in fee by the individual property owners on either side of the corridor. What the State holds is the perpetual right to maintain, repair, and protect the aqueduct infrastructure underneath, plus the public's right to walk the trail above.

For a Westchester homeowner, that means the practical situation is: you own the land within the easement strip but you cannot use it the way you would use the rest of your property. You cannot build structures on it. You cannot dig deep within it. You cannot fence across the trail. You cannot block public access. And any work that touches the easement — even setting a fence post adjacent to it — requires review and approval by the Old Croton Aqueduct State Park staff at NYS Parks before your local building department will issue a permit. (For the broader permit landscape that this easement review stacks on top of, see the 2026 Westchester permits guide; for how easement-related complications affect cost and timeline, see our 2026 cost guide.)

Which Westchester Properties Are Affected

The aqueduct enters Westchester at the Croton Dam in the Town of Cortlandt and runs continuously southward through every Rivertown municipality before crossing the Bronx border in southern Yonkers. The corridor passes through:

  • Cortlandt and Croton-on-Hudson — enters at the Old Croton Dam area, runs through Croton Gorge Park and down through the village.
  • Ossining — crosses through residential neighborhoods; the Sing Sing Kill Bridge over the aqueduct is one of the most visible OCA structures in the village.
  • Briarcliff Manor (Scarborough area) and Sleepy Hollow — passes through residential areas; Ventilator No. 10 (north of Scarborough Road) is one of 21 surviving stone ventilators along the route.
  • Tarrytown — runs along the edge of downtown and through residential blocks east of the village center.
  • Irvington — crosses residential properties throughout the village.
  • Dobbs Ferry — the corridor runs through residential streets; the 1857 Keeper's House on Walnut Street (the only original Keeper's House open to the public) sits directly on the aqueduct and now serves as a visitor center.
  • Hastings-on-Hudson — passes through hillside residential neighborhoods; many village properties are crossed by the easement.
  • Yonkers — runs through residential areas in the northern part of the city before crossing the Bronx border.

If you live in any of these communities and your property is anywhere near the aqueduct trail — even if you have never walked it — there is a real chance the easement crosses your parcel. (For the Hastings-specific renovation rules including how the easement plays out in that village, see our Hastings-on-Hudson renovation guide.)

What You Can and Cannot Do Within the Easement

The clearest framing of what the easement allows and prohibits comes directly from NYS Parks: the State holds the right to protect the aqueduct infrastructure and maintain public access to the trail. Anything that interferes with either of those rights requires review, and most such activities are not permitted.

Not allowed within the easement strip

  • New structures of any kind — sheds, gazebos, pool houses, garages, additions to the main house that extend into the strip.
  • Excavation that could affect the tunnel below — typically anything deeper than light grading.
  • Permanent fencing that crosses the trail or blocks public access.
  • Pools, hot tubs, septic tanks, leach fields, in-ground utility runs.
  • Asphalt or concrete paving over a significant area.
  • Trees with substantial root systems planted directly over the tunnel.

Allowed with NYS Parks approval

  • Driveway and walkway crossings of the easement strip (with constraints on width and surface).
  • Some landscaping, including shrubs and small plantings that do not obstruct the path.
  • Maintenance of existing legal pre-easement structures that happen to encroach (some pre-1968 structures are grandfathered).
  • Utility crossings (subject to depth and method of installation review).
  • Fencing parallel to the trail that does not block public access.

The Review Process When Your Project Touches the Easement

Any permitted work within or adjacent to the easement requires sign-off from the Old Croton Aqueduct State Park office, part of the NYS Office of Parks, Recreation and Historic Preservation, before your local building department will issue a permit. The practical sequence:

  1. Your architect or surveyor identifies the easement strip on your parcel — typically via a recorded easement document referenced in your deed, a property survey that shows the easement line, or a direct request to NYS Parks for a corridor map.
  2. Your project drawings show the easement boundary and clearly indicate where work falls inside vs. outside the strip.
  3. You (or your architect) submit a written request to the Old Croton Aqueduct State Park office describing the work and showing how it interacts with the easement.
  4. NYS Parks reviews and either approves, conditionally approves with modifications, or denies the request.
  5. The local building department incorporates the NYS Parks approval into their permit review and will not issue the building permit without it.

Review by NYS Parks typically takes 4–10 weeks depending on the complexity of the proposed work and the responsiveness of the State office. That timeline stacks on top of your local building permit review and any architectural review board cycle, meaning easement-affected projects often see 12–20 weeks of additional pre-construction calendar relative to comparable projects without easement exposure. (For the broader Westchester project timeline, see our 2026 Westchester renovation guide.)

Five Surprises Homeowners Discover Mid-Project

These are the situations that derail aqueduct-adjacent renovations most reliably:

  • Mid-design discovery. The architect produces a schematic addition that extends into the easement, then the surveyor flags it. Redesign work + lost time + potentially scrapped scope.
  • Pre-existing structure problem. A garage, shed, or porch was built decades ago partially within the easement. Pre-1968 grandfathered status can be defensible but is not automatic. Any substantial alteration or expansion of the encroaching structure can trigger a re-review.
  • Septic conflict. The existing septic field, or the only feasible location for a replacement field, falls inside the easement. NYS Parks will not approve a septic system within the strip, and your local building department will not waive the requirement. This is one of the most common project killers.
  • Tree removal trigger. A large tree directly over the tunnel is identified as a risk to the masonry below. NYS Parks may require removal, and your local tree ordinance may require replacement plantings outside the easement.
  • Sale-related discovery. A buyer's surveyor identifies the easement during due diligence, leading to price renegotiation, contract delays, or a deal collapse. Sellers who did not know about the easement during their ownership are sometimes blindsided.

How to Find Out If Your Property Has the Easement

Three reliable ways to confirm:

  1. Order a current land survey. A NY-licensed surveyor will identify the easement from recorded documents and show its location on your parcel. Cost typically $1,500–$3,000. The single most reliable answer.
  2. Review your deed and title insurance policy. The easement is recorded in the chain of title for any affected parcel. Look for references to "Aqueduct Commission," "City of New York," or "State of New York" easements in the deed schedule or title policy exceptions.
  3. Contact the Old Croton Aqueduct State Park office. NYS Parks maintains corridor maps and can confirm whether your address is within the affected zone. Useful for a quick preliminary check before commissioning a survey.

If you are buying a Rivertown property and the easement matters to your renovation plans, make a survey contingency explicit in your purchase contract. (See our pre-purchase checklist framework for older homes — the principles apply to Rivertown homes with easement exposure.)

Other Westchester Renovation Guides

Frequently Asked Questions

How wide is the Old Croton Aqueduct easement?

It varies by parcel and is defined by the original recorded easement document for each property. The State holds the right-of-way along the masonry tunnel below; the exact dimensions on your specific parcel will appear on a current land survey or in your recorded deed and title policy.

Can I build an addition over the aqueduct?

No. New structures are not permitted within the easement strip. Any addition needs to be designed and located entirely outside the easement, which on small lots can materially constrain what is feasible. Some pre-1968 structures that encroach are grandfathered, but substantial alteration of those structures often triggers re-review.

Does the easement affect my property value?

It can, in both directions. The constraints reduce the buildable area of the parcel, which is a real cost. But the public trail running along the corridor is also widely viewed as an amenity, and Rivertown property values reflect the proximity to it. Net effect depends on the parcel.

Who do I contact at NYS Parks to review my project?

The Old Croton Aqueduct State Historic Park office, part of the NYS Office of Parks, Recreation and Historic Preservation. Your architect or surveyor will typically handle the initial outreach as part of the permit submission package.

How long does NYS Parks review take?

Typically 4–10 weeks depending on project complexity. That review stacks on top of your local building permit review and any architectural review board cycle, often adding 12–20 weeks of additional pre-construction calendar relative to comparable projects without easement exposure.

Should I get a survey before buying a Rivertown house?

Yes, especially if the parcel is anywhere within a few hundred feet of the aqueduct trail. A current land survey is the single most reliable way to confirm whether the easement crosses the property and how much of the lot it consumes. Cost is typically $1,500–$3,000 — modest insurance against a six-figure problem later.

Sources

Brandon Cavanagh
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