Foundry Sand Reuse in Montana

Planning to reuse spent foundry sand in Montana? This guide covers the rules that apply, the tests that decide how the sand can be managed, and what DEQ needs before the sand can be reused.

Key terms

Spent foundry sand

Foundries bond silica sand into molds and cores for casting metal. The sand is reused many times in the plant. Spent foundry sand is molding and core sand that can no longer make molds or cores.

Green sand and chemically bonded sand

Green sand is bonded with clay, usually bentonite, plus water and additives such as carbon. Chemically bonded sand uses resin binders. Most cores are chemically bonded. The binder system affects what the spent sand contains.

Beneficial reuse

Beneficial reuse puts a waste material to productive use instead of disposing of it. In Montana, DEQ issues a beneficial use determination (BUD) for an industrial or manufacturing by-product used in a specific way.

TCLP

The Toxicity Characteristic Leaching Procedure (EPA Method 1311) measures how much of certain contaminants can leach from a sample. It is one part of deciding whether a waste is hazardous.

What’s in your spent sand?

Spent sand carries what the casting process added: binder residue, metal fines, and burnt core material. The alloy matters most. Sand from iron, steel, and aluminum foundries is the most commonly reused. Sand from leaded brass and bronze foundries is often regulated as hazardous waste.

Keep each stream separate. Baghouse dust, shotblast fines, cupola slag, broken cores, and core room sweepings need their own evaluation. Mixing them into spent sand can change how the whole load is managed. Track the alloys cast, the binder system, and any process changes.

Montana’s beneficial use process

Montana DEQ sets out its process in its Guide to Beneficial Use Determinations. Under ARM 17.50.508, a person needs a license before disposing of solid waste or operating a solid waste management system. An approved BUD exempts the applicant from that license for the specific use identified.

The by-product must be nonhazardous and used in the form in which it is generated. A by-product that needs treatment or reprocessing before reuse is not eligible for a BUD. That work is resource recovery, which needs a license. DEQ judges each proposal case by case. The product and end use must:

1. protect human health and the environment;
2. be a use rather than disposal, consistent with the Integrated Waste Management Plan;
3. substitute effectively for an analogous raw material or commercial product;
4. need no decontamination or treatment;
5. have a demonstrated, sustainable market and need;
6. divert waste from disposal and save resources or energy;
7. meet target contaminant levels; and
8. be used in a product or activity where contaminants are chemically bound.

The guide lists coal combustion residue and lime kiln dust as currently eligible. DEQ reviews all other by-products, including foundry sand, case by case. A BUD covers the use of material from the identified source, for the applicant. DEQ considers like material from other sources separately.

Applying to DEQ

• Who files: the person proposing the use. The form lets the applicant identify as the waste generator, a broker, an end user, or other.
• When: get DEQ approval before using the sand. Until then, it remains a solid waste.
• How: complete DEQ’s BUD application form, print it, and mail it with all attachments to the Solid Waste Section in Helena. No fee is required.
• What to include: the sand, its source and generating process, its proposed use, and its benefits. Add how it will be transported, stored, and used, the chemical and physical traits of the sand and the end product, and the estimated annual volume.
• Also include: proof of a sustainable market, proof the sand meets industry standards for the material it replaces, a materials control plan, and a contingency plan.
• Review time: DEQ decides in writing within 90 days of a complete application.
• Conditions: DEQ may set limits on site location, setbacks, depth to groundwater, and volume. It may also require follow-up testing, monitoring, or a risk evaluation.
• After approval: file an annual report by April 1. DEQ may revoke a BUD if its basis was wrong or no longer valid, for a violated condition, or for a public nuisance.

DEQ Solid Waste Program: (406) 444-5300.

Hazardous waste determination

Montana’s hazardous waste rules adopt the federal rules by reference. Under ARM 17.53.105, references to 40 CFR Parts 124, 260–268, 270, 273, and 279 mean the edition revised on July 1, 2025.

Under 40 CFR 262.11, the foundry must decide whether its spent sand is hazardous:

1. Make the determination at the point of generation, before mixing or dilution. Repeat it if the waste may have changed.
2. Check whether the waste is excluded from the hazardous waste rules.
3. Check whether it matches a listed hazardous waste.
4. Check for hazardous characteristics, including toxicity. Use knowledge of the materials and process, testing, or both. Test when knowledge alone is not enough.

Small and large quantity generators must keep records supporting the determination for at least three years after the waste was last sent for treatment, storage, or disposal.

TCLP testing and limits

Tell the lab the alloys cast, the binder system, and which streams the sample includes. Use representative samples. Agree on the sampling plan with the lab, DEQ, and the receiving site before collecting.

A waste is hazardous for toxicity if its TCLP extract meets or exceeds any limit in 40 CFR 261.24. The limits for the RCRA metals are:

Passing TCLP addresses toxicity for the substances tested. It does not approve reuse or rule out other reasons a waste may be hazardous. See material testing for sampling basics.

Consult DEQ before sampling for a BUD. Its analyses may include total metals, organics, PCBs, TCLP, SPLP (EPA Method 1312), or a neutral water leach test (ASTM D3987-06).

Finding a reuse destination

EPA’s 2014 risk assessment found three uses protective of health and the environment for silica-based spent sand from iron, steel, and aluminum foundries: manufactured soil, soil-less potting media, and road subbase. EPA and USDA support those uses. The finding does not cover sand from brass or bronze foundries, olivine sand, or sand mixed with other foundry wastes such as baghouse dust or cupola slag. EPA defers to state programs, so the state rules on this page still decide each use.

DEQ decides reuse case by case. Check any destination and proposed use with DEQ before scheduling delivery.

When you talk to DEQ, describe the proposal using the example uses in its BUD guide. For example, will the sand replace a raw material in cement, concrete, or asphalt pavement, or serve as confined fill under a paved lot or road? Get the receiving site’s specifications and written acceptance. If reuse is not cleared, arrange disposal that fits the waste determination.

Worker protection

• Silica: foundry sand is mostly crystalline silica. OSHA’s general industry standard, 29 CFR 1910.1053, sets a permissible exposure limit of 50 µg/m³ of respirable crystalline silica as an 8-hour average. Exposure assessment starts at the 25 µg/m³ action level.
• Construction use: crews placing sand as fill or subbase fall under the construction silica standard, 29 CFR 1926.1153.
• Lead: brass and bronze foundries that cast leaded alloys also follow OSHA’s lead standard, 29 CFR 1910.1025.
• Dust: control dust during shakeout, storage, and loading.

Storage and records

Store spent sand on a defined pad or in bins, control dust and runoff, and keep other foundry wastes out. The BUD application must describe the type of storage, the maximum inventory, and run-on and run-off controls. DEQ may set volume limits in the BUD.

Keep the waste determination, lab reports, DEQ approvals, and the receiving site’s acceptance together. Record tonnage shipped, dates, and destinations. The annual report covers the amount used, the uses and locations, test results, and where any resulting waste went.

Before pickup

1. Identify the alloys cast, sand and binder systems, separate streams, monthly volume, and plant location.
2. Make the hazardous waste determination and complete the required tests.
3. Choose a destination and get its material specifications.
4. File or confirm the DEQ BUD for that sand, source, and use.
5. Get written acceptance and arrange pickup.

Common questions

Rules and guidance

• Montana DEQ: Solid Waste Program
• Montana DEQ: Guide to Beneficial Use Determinations and Application Form
• Montana DEQ: BUD Annual Reporting Form
• ARM 17.50.508: Application for Solid Waste Management System License
• ARM 17.53.105: Incorporation by Reference (hazardous waste)
• 40 CFR 262.11: Hazardous waste determination
• 40 CFR 261.24: Toxicity characteristic
• EPA Method 1311: TCLP
• EPA: Beneficial Uses of Spent Foundry Sands
• EPA: Risk Assessment of Spent Foundry Sands in Soil-Related Applications
• 29 CFR 1910.1053: Respirable crystalline silica
• 29 CFR 1926.1153: Respirable crystalline silica in construction