Soil Testing and Soil Safety for Urban Gardens
Do you need to test your soil?
Few places require a soil test, but landlords, cities, funders and insurers often ask for one. Use this chart to decide.
- Do you know the full history of the site?If it was always a house lot, a farm field or park, the risk is lower but not zero. If it was a vacant lot, a gas station, a factory, a rail yard, a dump or a lot with a demolished building, assume you need to test. Go to step 2.
- Is the lot near older buildings, a busy road or treated wood?Paint from before 1978, car exhaust from the leaded gasoline era, and old treated lumber are common sources of lead, arsenic and other metals. Go to step 3.
- Will children, sales or food donations be involved?Children touch and eat soil, and sold or donated produce brings extra responsibility. Test before you start. Go to step 4.
- Is the lot owned by a city, land bank or landlord?Ask what environmental reports already exist. A prior Phase 1 or Phase 2 assessment may answer part of your question; see Phase 1 and 2 site assessments. Go to step 5.
- Order the right test and read it carefully.A pH or nutrient test will not show lead. See how to test for lead and contaminants. Go to step 6.
- Match the plan to the result.Low results can mean growing in the ground with good habits. Higher results mean raised beds, barriers and clean soil. See contaminated soil options.
Two different kinds of soil test
Many gardeners order a cheap test, see a green result and think the soil is safe. Garden tests and contaminant tests answer different questions.
| Test type | What it measures | Does it show lead or other contaminants? |
|---|---|---|
| Soil pH test | Acidity or alkalinity of the soil. Useful because pH affects plant growth and how soil metals behave. | No. |
| Basic fertility test (extension lab) | pH, major nutrients such as phosphorus and potassium, organic matter and lime or fertilizer advice. | Usually not, unless you add a metals package. |
| Lead or heavy metals test | Total lead and often arsenic, cadmium, chromium and other metals in parts per million. | Yes, for the metals listed on the report. |
| Environmental (contaminant) screening | Metals plus organic chemicals such as petroleum compounds and PAHs, chosen from the site history. | Yes, for the chemicals tested. |
| Phase 2 site assessment | Professional sampling and analysis of soil and sometimes groundwater, designed from a Phase 1 review. | Yes, and it documents where and how much. |
The EPA makes the same point in its guidance for gardens on former brownfield sites: environmental testing differs from the soil test conventionally done for plant health. Ask the lab which contaminants its package covers before you pay.
Where contamination comes from
Start with the history of the site and the lots around it. Contamination can come from the lot itself or blow and wash in from next door.
| Source | What may be in the soil | Where to look for it |
|---|---|---|
| Paint from before 1978 | Lead | Soil near the walls of older houses, garages and fences, especially where paint flaked or old buildings were scraped or burned. |
| Roads and heavy traffic | Lead, zinc and PAHs | Soil near busy streets and old highways. |
| Treated lumber and railroad ties | Arsenic, chromium, copper and creosote compounds | Old raised beds, fences, decks and rail corridors. |
| Burning of trash or buildings | PAHs, dioxins and metals | Former burn piles and sites of demolished or burned buildings. |
| Petroleum spills and tanks | PAHs, benzene, toluene and xylene | Former gas stations, garages and tank locations. |
| Commercial and industrial use | Solvents, petroleum, lead and other metals | Former dry cleaners, metal shops, factories and rail yards. |
| Pesticides | Lead, arsenic and mercury in historical products, and chlorinated pesticides | Former orchards, nurseries and lots with heavy past spraying. |
| Fill, compost and sludge | A mix, depending on the source | Imported topsoil or fill of unknown origin. |
The numbers you will see, and what they mean
People quote lead numbers as if they were garden rules. They are not. Know where each number comes from.
| Number | Where it comes from | What it means for a garden |
|---|---|---|
| 200 ppm and 100 ppm | EPA residential soil lead guidance of January 17, 2024 for Superfund and RCRA corrective action sites. Use 200 ppm, or 100 ppm when another source of lead is present, such as lead water service lines or lead-based paint. | A screening level, not a cleanup standard and not a garden rule. It helps decide when to look closer, and many gardeners use it as a caution line. |
| 400 ppm | The older EPA residential screening level, and still the figure in many fact sheets and older guidance. | Often quoted for gardens, but it was replaced for EPA site work in 2024. Do not assume it is safe for children. |
| 400 ppm and 1,200 ppm | 40 CFR 745.65(c), the federal lead-based paint hazard standard: bare soil in a child play area at 400 ppm or more, or the average of the rest of a yard at 1,200 ppm or more. | A housing rule about lead hazards around homes, not a standard for growing food. |
| State or city levels | Some states and cities publish their own screening values or garden guidance. | Ask your state environmental or health agency. They can differ from the federal numbers. |
No federal rule defines a safe soil level for growing food. EPA guidance for urban agriculture says there are no definitive standards for soil contaminant levels that fit the conditions and management of agricultural sites. This is why a good garden plan combines a test, the site history and common-sense habits, rather than one number.
What to do with the result
| Result | Usual approach | Read more |
|---|---|---|
| Low lead and no other concerns | Grow in the ground, keep soil covered with mulch or plants, wash and peel produce, keep adding compost, and retest every few years or after any major change. | See raised beds and cleanup. |
| Middle range or a history concern | Use raised beds with a barrier and clean soil, cover bare ground, keep children away from bare soil, and consider a deeper environmental test. | See testing for contaminants. |
| High lead or other contaminants | Do not grow food in the ground. Talk to your state environmental agency and a qualified professional before using the site, and consider another site. | See Phase 1 and 2 site assessments. |
These bands are not legal limits. Your state may publish its own approach, and a lab or health department can help you read a particular result. The EPA also suggests repeat testing after you add soil amendments, to confirm that the amendment controlled contaminant levels and that no new contaminated material came in with it.
Who is responsible for contaminated soil?
Responsibility depends on who owns the land, what the lease says and what the law of your state provides. A few practical points apply almost everywhere:
- The owner of contaminated land usually faces the legal duty to address it. A gardener who only leases or borrows land generally should not take on that duty by contract without advice.
- A lease or license should say who tested, who pays for testing, what happens if the result is high, and whether you may build raised beds. See land access.
- If you buy land, a Phase 1 site assessment can help you show that you made proper inquiry before the purchase. See Phase 1 and 2 site assessments.
- If you run a garden for others, tell gardeners the results in writing and set rules about children, bare soil and handwashing. See liability and insurance and volunteer liability.
- If you sell or donate produce, check market and food-safety rules; see food, agriculture and health.
Many states have programs that help evaluate or clean up contaminated property, often called voluntary cleanup or brownfields programs. Ask your state environmental agency whether one covers your site. EPA Brownfields assessment grants can pay for property-specific testing, but only governmental entities can receive them, so a community group usually needs a city or state partner.
Rules by city and state
Soil safety is a patchwork. A city may require a soil test to register a community garden, approve a garden on city land or issue a permit, and many have no requirement at all. A state may have screening values, cleanup programs or health department guidance. When you search for local rules, look at these places:
- your city or county garden program, parks department or land bank, which often sets conditions for gardens on public land (see also adopt-a-lot programs);
- your zoning and planning department for permits that mention environmental review;
- your state environmental protection or natural resources agency for screening values and cleanup programs;
- your state health department for lead guidance, and your county extension office for lab lists and sampling instructions.
Checklist before you plant food
- Write down the history of the lot and what stood on neighboring lots.
- Ask the owner for any Phase 1 or Phase 2 report.
- Order a lead and metals test, plus a contaminant package if the history calls for it.
- Take samples the way the lab asks (see the testing guide).
- Decide: grow in the ground, use raised beds with clean soil, or choose another site.
- Put the results and your decision in writing and share them with gardeners.
- Retest after adding soil, after construction nearby or every few years.
Frequently asked questions
Do I have to test my soil before starting a community garden?
Federal law does not require it. Your city, landlord, funder or insurer may. Testing is still the best way to know whether the soil is safe for food, especially on a vacant lot.
How do I test soil for a community garden?
Take samples from several spots and depths as the lab instructs, send them to a laboratory that tests for metals, and ask which contaminants fit your site history. See the testing guide.
What is a safe level of lead in garden soil?
There is no federal safe level for food growing. EPA’s 2024 screening levels are 200 ppm, or 100 ppm if another source of lead is present, for residential Superfund and RCRA sites. Lower is better, and children are the main concern.
Is 400 ppm lead safe for a vegetable garden?
400 ppm was the older EPA screening level and is still widely quoted. EPA lowered its residential screening level to 200 ppm in 2024, so 400 ppm should not be treated as a safe line, especially where children play.
Does a pH test show lead?
No. A pH test measures acidity. You need a lead or metals test, which a university extension or environmental lab can run.
What contaminants should I test for in an urban garden?
Lead first. Then arsenic and other metals if there was treated wood or pesticides, and PAHs and petroleum compounds if there were fuel tanks, garages or burning. The site history decides.
Is a vacant lot safe to garden on?
Not necessarily. Vacant does not mean clean. Check the history, ask for reports and test. A city partner may be able to test through an EPA Brownfields assessment program.
Do raised beds solve the problem?
They reduce contact with contaminated ground when built with a barrier and clean soil, but they can pick up dust and fall-out over time, so keep surrounding ground covered and retest. See raised beds and cleanup.
Who pays for soil testing?
The owner, the garden group, a funder, a city program or sometimes a government grant. Some university extension programs and health departments run low-cost or free testing; ask in your state.
Who is liable if someone gets sick from garden soil?
It depends on ownership, the lease, what was known and state law. Keep records of tests and communications, share results with gardeners and review liability and insurance.
Can I sell vegetables grown in soil with some contamination?
Selling food brings food-safety rules and possible liability. Markets or buyers may ask for soil test results. Do not sell or donate produce from soil with high results. See food, agriculture and health.
What if I rent the land and the soil is bad?
Tell the landlord in writing, ask who is responsible for testing and cleanup, and do not plant in the ground until you know. A lease should address soil conditions.
Does the EPA have a rule for gardens?
EPA publishes guidance and screening levels, including guidance on brownfields and urban agriculture, but no enforceable federal soil limit for gardens.
Official sources
- U.S. EPA, memorandum on updated residential soil lead guidance for CERCLA sites and RCRA corrective action facilities, January 17, 2024
- U.S. EPA, Know Before You Grow: Understanding Site Risks for Garden and Growing Activities (EPA-560-F-21-201, October 2021)
- U.S. EPA, Brownfields and Urban Agriculture: Interim Guidelines for Safe Gardening Practices (EPA 560/S-11/001, 2011)
- Code of Federal Regulations, Title 40, section 745.65 (lead-based paint hazards)
- Agency for Toxic Substances and Disease Registry (ATSDR) toxicological profiles for lead and other contaminants
- Your state environmental agency, state health department and university extension office
- Not checked for this page: individual city soil testing requirements, state screening values and the full text of the EPA interim guidelines