Arbor Hills: Surface-Methane SEM Exceedances

No walk track on the public record for routine quarterly surveys. The routine surveys publish exceedance locations only, not where crews walked.

Q2 2025

Exceedances shown0

Highest reading0

Type

Methane concentration

5005k50k150k+ ppm

Regulatory limit: 500 ppm above background. Every marker on this map is at or above it.

Marker size and color scale with methane concentration on a shared log scale (500 to 150,000+ ppm), so a Q2-2025 dot and a June-2026 dot mean the same thing at the same size.

perimeter air monitor (MS-1 to MS-6) and the Ridge Wood school monitor

SEM5000 walk track (toggle above; targeted inspections only)

Units: June-16 and the routine quarterly values are ppm over background; the Sept-25 hit list is raw ppm (background is about 1 to 2 ppm, negligible at this scale), so the shared log scale compares like with like.

These are documented exceedances under 40 CFR 63.1958(d) and 63.1960(c)(4). An exceedance is a reading at or above 500 ppm; it is not, on its own, a declared violation. Routine exceedances shown here were all cleared on re-monitoring.