Know your data sources.

Colorado CDPHE — Front-Range air quality, hazardous waste, voluntary cleanup, Superfund. - searchAirQualitySites ⭐ ~15.7K APCD facilities + ~359 CCND monitors merged - searchVoluntaryCleanup ⭐ ~1.7K VCUP + NAD applications. AppStatus: APPROVAL (1465) / WITHDRAWN / DENIAL / PENDING - searchHazardousWasteFacilities ~6.1K RCRA handlers (Generator_Status: VSG/SQG/N/LQG) - searchSuperfundSites ~31 NPL sites, getServiceInfo upstream quirks: Multi-server (AGOL + cohealthmaps.dphe.state.co.us). maps.dphe.state.co.us native UNREACHABLE externally. Air facility schema lean (5 fields, NO County). VCUP fields abbreviated (CityNam, RV_Nmbr). RCRA County UPPERCASE, maxRecordCount=1000.

Montana Department of Environmental Quality USTs + petroleum tank releases + MPDES water permits + air-quality monitoring + hazardous waste via gis.mtdeq.us/hosting. - searchUSTFacilities ⭐ 1.1K UST facility registry - searchTankReleases ⭐ 4.5K PTC cleanup events (Resolved/Open/Rescinded/Reopened) - searchWaterPermits ⭐ 2.7K MPDES discharge permits across 27 types - searchAirQualityMonitors ⭐ 21M hourly AQS readings (33 sites, PM25/O3/NO2/...) - searchHazardousWaste 3K RCRA generators §0: Native CRS 32100 (MT State Plane); outSR=4326. Host historically flaky — handler retries once. Most layers have NO county column (only Hazardous Waste does).

Pennsylvania DEP environmental — water, mining, hazardous waste, air. Same agency as pa-dep-oilgas, separate layers. - search303dImpairedStreams (~95K) ⭐ 303(d)-equivalent (impaired only). Filter use/cause/HUC - searchActMine ⭐ Anthracite + Bituminous + Industrial Mineral surface mine permits (~42K) - searchHazardousWasteSites (~16.9K Land Recycling Soil Media), searchAirEmissionSources (~61.3K), getServiceInfo upstream quirks: 303(d) layer 158 contains ONLY impaired streams (BLN_ATTAINED=N). Mining + Hazardous + Air layers have NO COUNTY column — silently dropped, use bbox/near or company/facility name. PERMIT_TYP freeform with 90+ values + typos. SITE_STATUS: ACTIVE / INACTIVE / ABANDONED / RECLAMATION COMPLETED / 'Unavaialble' [sic typo]. Air layer has only one PRIMARY_FACILITY_TYPE.