Where every record comes from
Each layer is a separate public source with its own date, geography and meaning. This page says what each one is, how it was processed, and what it cannot support.
Principles
- Records, not scores. Counts are records; sources overlap and are not unique facilities.
- Labeled evidence. Every source is tagged measured, modeled, agency record, agency estimate, facility self-report, community mapped or archived geometry.
- No record is not proof of absence. Empty results are shown differently from areas we do not cover.
- Extent is not a danger radius. The 30-mile regional air search follows EPA's toxic-release modeling distance; it is where we stop looking, not where effects stop.
How to read the dates
Source date means the year, sampling date or reporting period in the original record. Retrieved date means when NimbyCheck downloaded it. Page update means when our explanation changed. A recent download or page update does not make an older measurement current.
Editorial responsibility
Kostas maintains NimbyCheck through Synthesis Benefits LLC. Guidance is prepared from the linked agency publications; source dates, units, status wording and coverage limits are checked against those records. Automated checks cover counts, matching and page behavior. This is not independent field verification or review by a licensed environmental professional. Address Brief narratives use a language model constrained to the source records; the automated validation does not replace professional review.
Corrections and disagreements
If a location, status or explanation looks wrong, send the record link and the original agency document through Contact & corrections. Source-backed corrections take precedence over our interpretation. For current property conditions, obtain the latest agency file and ask the responsible professional.
Sources
| Source | Evidence kind | Scope | Date | Limits |
|---|---|---|---|---|
| MassDEP waste facilities | Agency record | Massachusetts | June 2024 dataset | Land-disposal polygons and transfer / combustion points; includes historical sites. Not all waste operations. |
| MassDEP tier-classified sites | Agency record | Massachusetts | Retrieved September 12, 2026 | Tier-classified records only, not every spill or cleanup. Individual status dates not supplied. |
| EPA Superfund National Priorities List | Agency record | United States | Retrieved 2026-10-03 | Proposed, listed and deleted NPL sites with status dates. A site point, not a plume boundary. |
| EPA ECHO hazardous-waste (RCRA) facilities | Agency compliance record | MA, NH, VT, ME, CT, RI, NY | Retrieved 2026-10-03 | Treatment, storage and disposal facilities and current significant non-compliers only; ordinary generators are omitted. |
| EPA Toxics Release Inventory | Facility self-report | MA map pins · 7-state regional context | Reporting years 2023–2024 | Facility self-reported chemical releases with units preserved. Reporting does not itself mean violation or exposure; pounds are not concentrations. |
| EPA ECHO Clean Air Act facilities | Agency compliance record | MA, NH, VT, ME, CT, RI, NY | Retrieved 2026-10-03 | Air-program status, compliance and enforcement fields. A violation can be procedural or emissions related; the detailed facility report says which. |
| EPA AQS PM2.5 monitors | Measured | 7-state region | 2025 annual summaries as retrieved | Measured regulatory monitors. A monitor reports its own location; values are never interpolated to a home. |
| EPA UCMR 5 PFAS occurrence | Measured | 7-state region, public water systems | UCMR 5 (2023-2025), retrieved 2026-10-03 | Sample results at treatment or entry points, aggregated per system. Small systems were only partly surveyed; private wells are not covered. |
| EPA SDWIS drinking-water violations | Agency record | 7-state region, community and non-transient systems | Health-based violations since 2021-01-01, retrieved 2026-10-03 | Health-based (MCL, MRDL, treatment-technique) violations with compliance status. Monitoring and reporting violations are excluded. |
| FEMA National Flood Hazard Layer | Agency map, live | United States | Live query per search | Effective mapped flood zones at the selected point. Not a building elevation or an insurance determination. |
| MassDEP estimated water service areas | Agency estimate | Massachusetts | Service-area vintage per system | Estimated community-system boundaries with a confidence flag. Does not verify a household connection or a private well. |
| BTS National Transportation Noise Map | Modeled | United States | 2022 model year | Modeled 24-hour average aviation, rail and road noise, shown as a regional overlay. The publisher says it must not be used to predict noise at an individual home. |
| EPA Map of Radon Zones | Agency estimate | Massachusetts counties | EPA spreadsheet, May 2024 posting | County-level potential. EPA states the map must not be used to decide whether a home should be tested; every home can test. |
| HIFLD transmission archive | Archived geometry | Massachusetts clip | Per-feature dates; often several years old | Archived geometry. Coverage of underground lines is incomplete. Distances do not measure EMF. |
| OpenStreetMap / Geofabrik | Community mapped | Massachusetts | Extract September 11, 2026 | Community-mapped cameras, communications nodes/ways and motorway/trunk/primary roads. Not field-verified. Indoor/private-tagged cameras excluded. © OpenStreetMap contributors, ODbL 1.0. |
| EFF Atlas of Surveillance | Agency record | United States · agency records | Publisher update August 27, 2026 | Documented agency technology use, not device locations or a complete inventory. Original sources can be older. CC BY attribution. |
| MassDEP estimated sewer service areas | Agency estimate | Massachusetts; watershed boundaries extend across state lines | Service year and confidence supplied per boundary | Estimated boundaries do not confirm a property connection or prove septic use outside them. |
| MassDEP Activity and Use Limitation sites | Agency record | Massachusetts; watershed boundaries extend across state lines | Publisher snapshot August 2025; filing dates per site | Approximate site points, not legal restriction boundaries. Unlocated and later filings may be missing. Verify the recorded instrument. |
| MassGIS major watersheds | Agency record | Massachusetts; watershed boundaries extend across state lines | June 2000 watershed delineation | Surface drainage context, not a groundwater plume, drinking-water service area or proof of downstream exposure. |
| MassGIS property tax parcels | Agency record | Massachusetts | Live query; fiscal year per parcel | Approximate assessor polygons, not a boundary survey. Parcel geometry is sent to FEMA to check mapped flood overlap. |
| Massachusetts registered sex offender totals by city · historical aggregate | Published aggregate | Ten cities only; other municipal counts are not supplied | Table labeled 2024; source footnote August 5, 2024 | FFY2025 Byrne JAG narrative, Table 7, page 24. Published city totals, not current online Level 2/3 search counts. No individual records or locations are collected. |
Processing
- Geometry is projected to Massachusetts State Plane for distances; distances are to the mapped point, line or site boundary.
- Waste layers keep separate identifiers per MassDEP layer, so a waste-to-energy plant co-located with a transfer station appears in both categories.
- TRI rows are grouped per facility with units preserved; dioxin-like compounds reported in grams are never summed with pounds. ECHO air-program records are linked to TRI facilities by TRI ID; for incinerators and landfills, ECHO records within 300 m are shown and labeled as matched by location only.
- UCMR 5 PFAS results are aggregated per public water system; the PFAS6 sum is computed within a single sample only.
- SDWIS violations are health-based violations with compliance periods beginning 2021 or later, for active community and non-transient systems.
- OpenStreetMap cameras tagged indoor or private are excluded; missing tags are not proof of public ownership.
- Agency surveillance records (EFF Atlas) are never turned into device pins.
Investigation priority and property checks
Records are ordered by serious compliance flags, documented cleanup or release findings, current or unresolved source status, historic or closed records, and other mapped infrastructure. Source type and distance break ties. Each card states the reasons. Location-only air-record matches do not establish the selected facility's compliance. This is an investigation order, not a health-risk score.
Parcel boundaries come from MassGIS. Water and sewer service areas are estimates, not confirmed connections. AUL site points flag documents to review; they do not establish which parcel is legally restricted. Watersheds describe surface drainage, not groundwater contamination or a measured impact area. See the original sources under Data & coverage.
Updates and corrections
Time-varying sources are refreshed monthly by a scheduled job that rebuilds the data and restarts the service only when tests pass; the update history is shown under Data & coverage on the map. Corrections submitted through the contact form are checked against the original source.
Known limits
- Map layers cover Massachusetts only; the regional air context covers MA, NH, VT, ME, CT, RI and NY; Superfund and flood lookups are national.
- Communications structures are not a complete cell-tower inventory. No verified Flock device inventory is claimed.
- Flood zones are queried for the map point and, where a parcel match is available, across an approximate tax parcel. Neither is a surveyed building or elevation.
- Water service boundaries are MassDEP estimates with a confidence flag; they do not verify a household connection.