Sources of Potential Water Resource Contamination

Q: What are examples of Category I contamination sources?

A: Septic tanks, cesspools, injection wells, land applications (wastewater, sludge).

Q: How do septic tanks potentially contaminate groundwater?

A: Through leaks that release bacteria, pathogens, and nutrients, potentially causing HABs.

Q: What risks are associated with injection wells?

A: Induced seismicity, groundwater contamination, accidental leakage, land subsidence.

Q: What are some uses for injection wells?

A: Hazardous waste storage, brine disposal, artificial recharge, solution mining, enhanced oil recovery.

Q: What are examples of Category II contamination sources?

A: Landfills, surface impoundments, mining tailings, illegal dumps, radioactive disposal sites, USTs, graveyards.

Q: What risks do landfills pose to groundwater?

A: Contamination by toxic metals, ammonia, organic compounds, pathogens, and emission of greenhouse gases (CH₄, CO₂).

Q: Why are graveyards considered potential contamination sources?

A: Leachate may contain pathogenic bacteria and viruses that seep into groundwater.

Q: What are examples of Category III contamination sources?

A: Pipelines, overland transport (trains, trucks).

Q: What incident is associated with Category III risks?

A: East Palestine, OH train derailment – concerns over dioxin exposure and bioaccumulation.

Q: What are examples of Category IV contamination sources?

A: Irrigation return flow, pesticide/herbicide application, road construction, de-icing salts, feedlots, urban runoff, mining effluents.

Q: What is the long-term concern with de-icing salt in aquifers?

A: Contamination can persist and accumulate over 20+ years.

Q: What causes Acid Mine Drainage (AMD)?

A: Mining effluents leading to oxidation of sulfide minerals, releasing metals and acidity.

Q: What are examples of Category V sources?

A: Production wells, water wells, oil and gas wells.

Q: How can these sources induce contamination?

A: They alter subsurface flow paths and may allow pollutants to migrate into clean aquifers.

Q: What are examples of Category VI sources?

A: Saltwater intrusion, groundwater-surface water interaction, natural leaching enhanced by human activities.

Q: How can human activity increase natural leaching?

A: Through land use changes, deforestation, or altering redox conditions (e.g., arsenic mobilization).

Category I

Sources Designed to Discharge Substances

Category II

Sources Designed to Store, Treat, or Dispose Substances

Category III

Sources Retaining Substances During Transport

Category IV

Sources Discharging Substances as a Byproduct of Other Activities

Category V

Sources Providing a Conduit or Flow Path

Category VI

Naturally Occurring Sources Exacerbated by Human Activity