Contaminated Soil & Groundwater

Many construction sites sit on land that was once a gas station, factory, dry cleaner, railyard or dump. Digging there can release fuel vapors, solvents, heavy metals and other contaminants into the air, onto skin and into water. Workers can be harmed without warning, and mistakes can create costly cleanup and legal problems. Knowing the signs and the rules protects both people and the environment.

• Construction
• Excavation
• Environmental

Common contaminants

• Petroleum: gasoline, diesel, oil and fuel leaks from tanks and spills. Gasoline contains benzene. See Benzene.
• Solvents: degreasers and dry-cleaning fluids such as trichloroethylene (TCE) and perchloroethylene (PCE). Vapors can rise into buildings. See Solvents.
• Metals: lead, arsenic, cadmium, chromium and mercury from industry, old paint, smelters and slag. See Lead, Cadmium and Mercury.
• Other chemicals: PCBs, pesticides, coal tar, creosote, PFAS and industrial waste.
• Asbestos, old debris and fill with building materials. See Asbestos.
• Landfill gas: methane and hydrogen sulfide from decomposing waste, which can explode or asphyxiate. See Hydrogen Sulfide.
• Unexploded items, drums and buried containers may be hidden.

Signs you may have hit contamination

• Odors: fuel, solvent, chemical, sweet, sewage or rotten egg smells.
• Discolored soil: stained, black, green, blue, orange or oily soil, or a sheen on water in the trench.
• Buried items: drums, tanks, pipes, batteries, slag, ash, debris or trash.
• Stressed or dead vegetation on the site, and soil that looks or feels unusual.
• Symptoms in workers: headaches, dizziness, nausea, burning eyes or throat, skin irritation or a metallic taste.
• Instrument readings, such as a photoionization detector (PID) or gas meter alarm. See Gas Detectors.

Before the dig: find out first

• Review environmental reports, such as a Phase I environmental site assessment (history review) and any Phase II (sampling), and ask the owner what’s known about the site. Check if the site is a former gas station, factory, landfill or dry cleaner.
• Plan for it: if contamination is expected, the owner or contractor should prepare a health and safety plan, a soil and groundwater management plan and a waste plan, with the right trained people.
• Check regulations. Federal, state and local rules (such as EPA, state environmental agencies) govern how contaminated soil is tested, handled, moved and disposed of. Permits and notifications may be needed.
• Call 811 and check for buried tanks and utilities. See Call 811 and underground tank removal.
• Train workers on the known hazards and how to recognize unexpected ones. See Hazard Communication.

HAZWOPER training

• OSHA’s Hazardous Waste Operations and Emergency Response (HAZWOPER) standard (29 CFR 1910.120, and 1926.65 for construction) applies to workers at hazardous waste sites, cleanup sites and some emergency responses. See HAZWOPER.
• It requires a site-specific safety and health plan, site characterization, air monitoring, medical surveillance, decontamination and training. Most cleanup workers need 40 hours of initial training, and others need 24 or 8 hours depending on their exposure, plus annual refreshers. See Medical Surveillance Requirements.
• Ordinary construction work on a site with some contamination may not trigger HAZWOPER, but unknown hazards found during digging can. Ask the employer and the competent person.

Controlling exposure

• Air monitoring: test for vapors, oxygen, flammable gas and toxic gases before and during digging, and in trenches and confined spaces. See Trench Atmospheres and LEL & Flammable Gas Detection.
• Dust and vapor control: wet down soil, cover stockpiles, limit open excavations, and use ventilation or vapor suppressants, as the plan calls for. Keep dust from blowing offsite.
• Engineering controls first, then work practices, and then PPE. See Hierarchy of Controls.
• PPE based on the hazards: chemical-resistant gloves, boots and coveralls, eye and face protection, and respirators where needed, with training and fit testing. See Chemical-Protective Clothing and Respiratory Protection.
• No eating, drinking or smoking in work areas, and wash hands and face before breaks. See Sanitation.
• Decontamination: set up a clean zone and a wash station, clean boots and equipment before leaving, and bag contaminated PPE. Don’t take dirty clothes or boots home. See Take-Home Contamination.
• Fire and explosion controls where flammable vapors are present: eliminate ignition sources and use proper equipment. See Hazardous (Classified) Locations.

Handling soil and water

• Segregate soils. Keep clean and contaminated soil separate, with labeled stockpiles on liners, covered, and surrounded by berms to stop runoff. Don’t mix them, or you may turn a large clean pile into a contaminated one.
• Test and characterize excavated soil before disposal or reuse. Waste rules determine where it can go: a landfill, a treatment facility or reuse onsite.
• Transport and manifests: contaminated soil may need licensed haulers, covered trucks, tire cleaning and paperwork. Hazardous waste has strict rules.
• Groundwater: contaminated water in a trench can’t simply be pumped onto the ground or into a storm drain. It may need testing, treatment, permits and special discharge. See Dewatering and Stormwater & SWPPP.
• Protect the neighborhood: control dust, odors, noise, truck traffic and runoff. Notify neighbors when needed.

If you find an unexpected spill or buried tank

1. Stop work and move people upwind and away.
2. Isolate and mark the area, and eliminate ignition sources if there are fuel or gas odors.
3. Notify your supervisor and the site owner. Follow your emergency plan. See Spill Response and Emergency Action Plans.
4. Environmental agencies must usually be notified of releases of oil, hazardous substances or a leaking tank, and the owner or responsible party handles this.
5. Don’t move, pump, open or burn drums and tanks. Wait for qualified people to sample and manage them.
6. Get medical help for anyone with symptoms. See Chemical Exposure First Aid.

Contaminated soil checklist

• Site history and environmental reports reviewed; plans and permits in place
• Workers trained on hazards; HAZWOPER training where it applies
• Air monitored; engineering controls, PPE and decontamination set up
• Suspect odors, stains, drums or tanks cause an immediate stop and a report
• Soil and water segregated, tested and disposed of under the rules
• No food or drink in work areas; clean-up before leaving

Last updated: October 4, 2026