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Superfund / NPL site · EPA Superfund SEMS through latest publishNPL Final

Upper Tenmile Creek Mining Area

This site is currently on the EPA Superfund National Priorities List and remains under federal cleanup oversight. Most-cited contaminant of concern: Arsenic.

Rimini Road, Helena, Montana · ZIP 59601 · EPA ID MTSFN7578012

See Lewis And Clark ContaminantsEquity contextHow we read Superfund data
CLEANUP TIMELINE

Listing-date and cleanup-phase enrichment from EPA's per-site SEMS profile is queued for a follow-up ingest pass. Until then, this section will populate from EPA's published timeline data.

Anomaly engine

Notable Signals

No notable signals at this Superfund site for the current ingest. Cleanup-phase and SEMS-action flags are deferred to a follow-up engineering pass.

Contaminants of concern · per EPA SEMS

What's In This Site

Each row pairs a contaminant with the medium it was found in (the exposure pathway). Hover any named contaminant for an agency-cited health-risk summary. Cited count = number of SEMS decision records (RODs and related) that name the pair.

ContaminantPathwayCited
ArsenicHealth riskIARC Group 1 carcinogen via inhalation and ingestion. EPA MCL 10 µg/L; chronic exposure causes skin, lung, bladder cancer and cardiovascular disease. (IARC, EPA, ATSDR)Groundwater2
CadmiumGroundwater2
LeadHealth riskNeurotoxin. Even low childhood exposure impairs cognitive development; chronic adult exposure damages kidneys and the cardiovascular system. (EPA, ATSDR)Groundwater2
ZincHealth riskGenerally low acute toxicity. Chronic high-dose exposure disrupts copper absorption and immune function. (ATSDR)Groundwater2
AluminumHealth riskInhaled aluminum fumes can cause lung scarring (aluminosis); high cumulative exposure has been linked to neurological effects. (NIOSH)Surface Water1
ArsenicHealth riskIARC Group 1 carcinogen via inhalation and ingestion. EPA MCL 10 µg/L; chronic exposure causes skin, lung, bladder cancer and cardiovascular disease. (IARC, EPA, ATSDR)Leachate1
ArsenicHealth riskIARC Group 1 carcinogen via inhalation and ingestion. EPA MCL 10 µg/L; chronic exposure causes skin, lung, bladder cancer and cardiovascular disease. (IARC, EPA, ATSDR)Sediment1
ArsenicHealth riskIARC Group 1 carcinogen via inhalation and ingestion. EPA MCL 10 µg/L; chronic exposure causes skin, lung, bladder cancer and cardiovascular disease. (IARC, EPA, ATSDR)Soil1
ArsenicHealth riskIARC Group 1 carcinogen via inhalation and ingestion. EPA MCL 10 µg/L; chronic exposure causes skin, lung, bladder cancer and cardiovascular disease. (IARC, EPA, ATSDR)Solid Waste1
ArsenicHealth riskIARC Group 1 carcinogen via inhalation and ingestion. EPA MCL 10 µg/L; chronic exposure causes skin, lung, bladder cancer and cardiovascular disease. (IARC, EPA, ATSDR)Surface Water1
CadmiumLeachate1
CadmiumSediment1
CadmiumSolid Waste1
CadmiumSurface Water1
CopperHealth riskInhaled copper fumes cause metal-fume fever; chronic ingestion above EPA's 1.3 mg/L action level damages the liver. (EPA)Groundwater1
CopperHealth riskInhaled copper fumes cause metal-fume fever; chronic ingestion above EPA's 1.3 mg/L action level damages the liver. (EPA)Surface Water1
IronGroundwater1
IronLeachate1
IronSurface Water1
LeadHealth riskNeurotoxin. Even low childhood exposure impairs cognitive development; chronic adult exposure damages kidneys and the cardiovascular system. (EPA, ATSDR)Leachate1
LeadHealth riskNeurotoxin. Even low childhood exposure impairs cognitive development; chronic adult exposure damages kidneys and the cardiovascular system. (EPA, ATSDR)Sediment1
LeadHealth riskNeurotoxin. Even low childhood exposure impairs cognitive development; chronic adult exposure damages kidneys and the cardiovascular system. (EPA, ATSDR)Soil1
LeadHealth riskNeurotoxin. Even low childhood exposure impairs cognitive development; chronic adult exposure damages kidneys and the cardiovascular system. (EPA, ATSDR)Solid Waste1
LeadHealth riskNeurotoxin. Even low childhood exposure impairs cognitive development; chronic adult exposure damages kidneys and the cardiovascular system. (EPA, ATSDR)Surface Water1
ManganeseHealth riskExcess inhalation can cause manganism, a Parkinson-like neurological disorder. (ATSDR)Groundwater1
ManganeseHealth riskExcess inhalation can cause manganism, a Parkinson-like neurological disorder. (ATSDR)Leachate1
ManganeseHealth riskExcess inhalation can cause manganism, a Parkinson-like neurological disorder. (ATSDR)Surface Water1
MercuryHealth riskNeurotoxin. Methylmercury bioaccumulates up the food chain and damages the developing nervous system. (EPA, ATSDR)Groundwater1
MercuryHealth riskNeurotoxin. Methylmercury bioaccumulates up the food chain and damages the developing nervous system. (EPA, ATSDR)Solid Waste1
ZincHealth riskGenerally low acute toxicity. Chronic high-dose exposure disrupts copper absorption and immune function. (ATSDR)Leachate1

Showing the top 30 pairs by SEMS citation count. 3 additional (contaminant, pathway) pairs are recorded for this site.

Drinking-water linkage · SDWIS

No Groundwater PWSes Serving Communities Within 3 Miles

No SDWIS public water systems drawing groundwater (or mixed sources) serve a community whose centroid sits within 3 miles of this site. Empty results are not a guarantee of non-impact — distance is computed to served-place centroids, and SDWIS does not expose individual wellhead locations.

Methodology: served-city centroid (TIGER 2020) is used as the PWS coordinate. Source-water classification from SDWIS primary_source_code; only groundwater and mixed-source systems are queried. Click any system above for its full SDWIS profile.

Equity context · ACS 2018-2022 block-group demographics

Who Lives Near This Site

Lewis And Clark County, Montana (no Census block groups within 1 mile and no host city — falling back to containing county): a population of 71,487. Why we surface this →

POPULATION SHARE
9.4%

Low-income

POPULATION SHARE
10.3%

People of color

POPULATION SHARE
5.6%

Under age 5

POPULATION SHARE
19.5%

Over age 64

Source: Census ACS 2018-2022 (5-year) + USEPA-clone EJ blockgroup stats (raw indicators + EJ disparity mirror). NPL site proximity contributes to the national EJ pattern; indicator-level percentile and disparity scores are surfaced on the county page and the state page.

Source. EPA Superfund Enterprise Management System (SEMS) · retrieved 2026-05-07. SEMS is a federal public-domain dataset under 17 USC §105.

What this is not. We report EPA's published Superfund record — site listing, status, and contaminants of concern as named in EPA's decision documents. We do not perform site visits, independent air or water sampling, or current-state health-risk assessment. NPL listing reflects EPA's Hazard Ranking Score at a point in time; it does not by itself describe present-day exposure.