Cayuga Island Record DEC 932008

What was found

Mercury, pesticides, and a pathway into the house

The contaminants in this record are named, but not quantified. DEC has published the list and the exceedance; it has not published a single concentration. That distinction governs this whole page.

Last verified 11 September 2026 No concentrations in the public record

The contaminants named in the record

Two sources name substances: DEC’s own fact sheets, and reporting by the Niagara Gazette. They are listed separately below because they do not carry the same weight.

Substances named in connection with the West Rivershore Drive investigation. An agency naming a contaminant is a finding; a newspaper naming one is reporting.
Substance Named by Where
Mercury NYSDEC Primary 1992–93 assessments and the 2025–26 investigation1
Pesticides NYSDEC Primary 1992–93 assessments and the 2025–26 investigation1
“Other contaminants”, unspecified NYSDEC Primary Fact sheet wording, both 2026 updates1
Lead Niagara Gazette Reporting 15 and 20 June 202654
BHC (benzene hexachloride) Niagara Gazette Reporting 15 June 20265
PCBs Niagara Gazette Reporting 20 June 20264
Other organic chemicals Niagara Gazette Reporting 15 and 20 June 202654
Why there are no numbers here

DEC’s September 2026 update states that sampling results were “provided directly to the property owners.”1 No per-property or per-contaminant concentrations appear anywhere in the public file. Any figure you see attached to this story — a parts-per-million value, a multiple of a standard — did not come from the public record. This site publishes none.

Where in the ground it sits

DEC describes the material as mostly subsurface soil rather than at the surface.5 That matters for how people could be exposed: it points away from casual surface contact and toward two other routes — disturbing the ground, and vapour moving upward into buildings.

As of 1 September 2026, DEC states that results from participating properties “confirmed some impacts to indoor air and soil.”1 Both routes, in other words, are now documented as real at some addresses.

The mechanism

Soil vapour intrusion

This is the term that runs through every DEC document about the site, and it is worth understanding precisely. New York State defines it as the process by which chemicals in the ground can enter the indoor air of a building through its basement, crawlspace or slab.112

Buried volatile chemicals evaporate into the air spaces between soil particles. That soil gas moves toward lower pressure — and a heated building is usually at slightly lower pressure than the ground beneath it. Gas follows cracks, utility penetrations and sump openings into the lowest level, then distributes through the house. Nothing has to be spilled or handled for it to happen; the material can sit undisturbed metres down.

It is also why DEC’s sampling programme pairs two measurements at once: a sub-slab sample of the gas directly beneath the floor, and an indoor air sample inside the living space. One without the other cannot tell you whether what is in the ground is getting in.

Cross-section of the west end of Cayuga Island A schematic section through the western tip. A band of fill containing industrial material sits beneath houses on ground that was added to the island, reaching about seventeen feet below the surface, over native river deposits. Arrows show soil vapour rising from the fill through a basement slab into indoor air. To the right, a dashed line marks the approximate original shoreline and the pre-existing ground of the island. Niagara River approx. original shoreline Added to the island early 1900s, and again 1958–1962 Pre-existing ground Indoor air Basement Slab soil vapour Fill containing industrial material mercury, pesticides and others Native river deposits original island ground 0 ft 5 10 15 20 depth below ground surface
Schematic, drawn to the one depth figure in the public record. The fill band is set to about 17 feet because that is the deepest fill DEC’s contractor logged in 2022 at Griffon Park, across the Little River — fill in five borings between 5 and 17 feet below ground surface, containing clear and brown glass, metal, cloth, brick fragments, cinder and wood.10 No comparable boring log has been published for the island itself, and the depth, thickness and extent of fill under West Rivershore Drive are exactly what DEC’s second phase of investigation is meant to establish.1 Treat the section as an illustration of the pathway, not a survey of any property.

Follow the pathwayHover or tap any layer of the section to read what the record actually says about it. Nothing here is a measurement of any individual property.

01
Contaminants sit in the fill

Buried industrial material in the soil beneath and around a property.

02
Some of them turn to vapour

Volatile chemicals evaporate from soil and groundwater into the air spaces in the ground.

03
Vapour collects under the slab

It moves upward and gathers beneath the basement floor, crawlspace or slab — the sub-slab space DEC samples.

04
It enters the indoor air

Through cracks, joints and utility penetrations. This is the pathway DEC confirmed had impacts at participating properties in September 2026.1

The sampling programme

What DEC actually tests, and what each test answers

DEC and DOH built a three-part plan for properties on the western tip. Each part answers a different question.1

The three components of DEC’s property sampling plan, as described in its fact sheets.
What is sampled How The question it answers
Surface soil Up to four locations per property, by hand digging or augering15 Is there anything in the ground people touch — gardens, lawns, where children play?
Sub-slab soil vapour and indoor air Paired samples, one beneath the floor and one in the living space1 Are chemicals underground getting into the air inside the building?
Sump water Collected from homes that have a sump1 Is groundwater moving through the fill and arriving inside the house?

What an exceedance of a screening level means

DEC’s December 2025 results showed “exceedances of DEC screening levels in residential settings for several contaminants.”1 A screening level is a decision threshold, not a line between safe and poisoned. Exceeding one is what obliges an agency to look further; it does not by itself establish that anyone has been harmed, and staying under one does not prove nobody could be.

It is also why DEC’s language shifted between February and September 2026. In February the agency was investigating a possibility. By September it reported that findings had “confirmed some impacts to indoor air and soil” at participating properties.1 That is a change in what is established, and it is the reason the investigation grew rather than closed.

Health questions go to DOH

This site does not assess health risk, and cannot. New York State’s Department of Health runs a Bureau of Environmental Exposure Investigation, named in DEC’s fact sheet as the contact for exactly these questions: beei@health.ny.gov.1 DOH also publishes general guidance on soil vapour intrusion.12

A note on discipline

The July 2026 data that is not summarised here

On 23 July 2026 DEC posted an analytical report for Griffon Park covering soil, sediment and groundwater samples that reached Pace Analytical Services on 17 June 2026. The suite was broad: volatile and semivolatile organics, 1,4-dioxane, organochlorine pesticides, PCBs, total metals, anions and general chemistry.11

The document’s own title carries the word unvalidated. Laboratory data becomes usable for decisions only after a validation step that checks holding times, blanks, duplicates, recoveries and qualifiers. Until DEC completes that, any figure pulled from those tables could move or be rejected outright.

So the report is indexed in the document library and linked in full, and not one number from it appears on this site. When DEC posts validated results, they will be summarised here with the date they were validated.

Sources on this page

  1. NYSDEC, West Cayuga Island — Site Investigation Update (1 September 2026); and Investigation (9 February 2026). Primary
  2. Mark Scheer, “Two decades since DEC last probed Cayuga Island contaminants”, Niagara Gazette, 20 June 2026. Reporting
  3. Mark Scheer, “DEC: chemical sampling underway on west end of Cayuga Island”, Niagara Gazette, 15 June 2026. Reporting
  4. NYSDEC, Field Activities Report — Inactive Landfill Initiative, Griffon Park, 9 March 2023. Primary
  5. NYSDEC / Pace Analytical Services, Griffon Park July 2026 Analytical Report (unvalidated), 23 July 2026. Primary
  6. New York State Department of Health, Soil Vapor Intrusion. Primary