Natrona, WY
Transparent derived index from EPA TRI / SDWIS / Superfund extracts: not an official EPA rating. Fixed caps: facilities ≤25 pts (50+ = max), log10 releases ≤25 pts, Superfund ≤25 pts (5/site), health-violation systems ≤15 pts (3/system), high-chemical facilities ≤10 pts. Bands: High ≥60, Moderate ≥30. See methodology.
Environmental data for Natrona in Wyoming · Population: 79,735
TRI sites such as Hf Sinclair Casper Refining LLC; Championx-Evansville Plant 108; Dura-Line; SDWIS systems such as CASPER, CITY OF; MILLS, CITY OF; BAR NUNN, TOWN OF; NPL sites such as Mystery Bridge Rd/U.S. Highway 20 anchor Natrona, WY's EPA extract. Derived burden score 49/100 (Moderate Risk) uses fixed national caps on density, log release volume, Superfund count, and health-flagged systems - not an official EPA rating.
Health-flagged SDWIS rows in Natrona include MILLS, CITY OF; NATRONA COUNTY INT'L AIRPORT; POISON SPIDER I&S DISTRICT, while Hf Sinclair Casper Refining LLC leads reported TRI pounds among local Form R filers. AQS median AQI 43 / peak 136 in 2024.
Burden score 49/100 (Moderate Risk) is the only weighted composite on this page. The tables below list every TRI facility, SDWIS system, and Superfund site EPA has on record for Natrona -- not just the names called out above -- reproducing the disclosure history as filed, not a current-safety verdict. Extract current as of 2026-08-25.
Release-over-release change
What changed for Natrona, WY: EPA TRI 2023 reporting year
Same facilities, both years
+2.8%
9 facilities that filed in 2022 and 2023
Whole inventory
+11.1%
45.2 thousand lb → 50.2 thousand lb, every facility that filed
Between the two reporting years, 1 facility filed for the first time and 0 stopped filing. Facilities entering or leaving the inventory are excluded from the same-facility comparison above.
- Natrona, WY's total reported releases rose from 45.2 thousand lb in 2022 to 46.4 thousand lb in 2023, based on EPA TRI filings.
- Natrona, WY's off-site transfers fell from 3.5 thousand lb in 2022 to 90 lb in 2023, based on EPA TRI filings.
- Natrona, WY's air releases rose from 41.5 thousand lb in 2022 to 46.3 thousand lb in 2023, based on EPA TRI filings.
- Natrona, WY's chemicals reported fell from 36 in 2022 to 34 in 2023, based on EPA TRI filings.
Air Quality History (2020–2024)
EPA Air Quality Index (AQI) data showing how many days per year fall into each air quality category.
| Year | Good | Moderate | Unhealthy (SG) | Max AQI |
|---|---|---|---|---|
| 2024 | 282 (77%) | 78 | 6 | 136 |
| 2023 | 344 (94%) | 20 | 1 | 102 |
| 2022 | 317 (87%) | 48 | 0 | 97 |
| 2021 | 282 (77%) | 77 | 6 | 125 |
| 2020 | 316 (86%) | 46 | 4 | 124 |
Source: EPA Air Quality System (AQS) Annual AQI by County AQI categories: Good (0-50), Moderate (51-100), Unhealthy for Sensitive Groups (101-150), Unhealthy (151-200), Very Unhealthy (201-300), Hazardous (301+)
For real-time air quality readings and pollutant breakdowns in Wyoming, see the EPA's AirNow.gov.
Water Systems (22)
| System | System pop (SDWIS) | Violations |
|---|---|---|
| CASPER, CITY OF | 59,000 | 0 |
| MILLS, CITY OF | 4,050 | 9 |
| BAR NUNN, TOWN OF | 4,000 | 0 |
| EVANSVILLE, TOWN OF | 2,873 | 0 |
| VISTA WEST WATER COMPANY | 1,600 | 0 |
| PIONEER WATER & SEWER DISTRICT | 1,500 | 0 |
| NATRONA COUNTY INT'L AIRPORT | 423 | 2 |
| RIVERSIDE MOBILE HOME COURT | 330 | 0 |
| MIDWEST, TOWN OF | 325 | 0 |
| AIR BASE ACRES I&S DISTRICT | 236 | 0 |
| POISON SPIDER I&S DISTRICT | 200 | 1 |
| EDGERTON, TOWN OF | 195 | 0 |
| LEX MOBILE HOME PARK | 172 | 0 |
| SANDY LAKE ESTATES I&S DISTRICT | 150 | 0 |
| PLEASANT VIEW WATER COMPANY | 130 | 0 |
| COUNTRYSIDE COURT | 125 | 2 |
| SOUTH RIVERSIDE ACRES WTR IMPR DIST | 125 | 0 |
| THIRTY-THREE MILE ROAD I&S DISTRICT | 100 | 0 |
| LAKEVIEW I&S DISTRICT | 62 | 0 |
| MILE-HI I&S DISTRICT | 48 | 1 |
| BROKEN WRENCH LLC | 30 | 9 |
| CENTRAL WY REGIONAL WATER SYSTEM JPB | 25 | 0 |
TRI Facilities (12)
| # | Facility | Total Releases |
|---|---|---|
| 1 | Hf Sinclair Casper Refining LLC | 110.8K lbs |
| 2 | Championx-Evansville Plant 108 | 62.5K lbs |
| 3 | Dura-Line | 40.2K lbs |
| 4 | Custom Fiberglass Inc | 32.2K lbs |
| 5 | Excal Inc. | 7.6K lbs |
| 6 | Tallgrass Midstream LLC - Casper Gas Plant & Compressor Stat | 3.7K lbs |
| 7 | Joy Global Evansville Wy | 765 lbs |
| 8 | Truenorth Steel-Casper | 480 lbs |
| 9 | Knife River Casper | 112 lbs |
| 10 | Knife River Materials Yard | 58 lbs |
| 11 | Halliburton Casper Field Camp | 0 lbs |
| 12 | Halliburton Casper Baroid | 0 lbs |
Superfund Sites (1)
| Site Name | Status | HRS Score |
|---|---|---|
| Mystery Bridge Rd/U.S. Highway 20 | Deleted NPL Site | 32.10 |
Cities in Natrona (6)
Frequently Asked Questions
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What does this county environmental profile show?
This county environmental profile rolls up EPA Toxics Release Inventory facility reports, Safe Drinking Water Information System public-water-system filings, and Superfund National Priorities List sites for the county boundary defined by the U.S. Census Bureau. Facility counts reflect facilities with a reporting address inside the county, not where downstream environmental effects may be observed. Population figures are from the most recent Census ACS 5-year estimate. The county detail page is updated whenever the upstream EPA programs publish revised data; see the methodology page for the documented ingest cadence and the editorial choices governing how aggregations are computed.
Read our methodology - how this data is sourced, computed, and verified.