Foundry Sand Reuse in Colorado

Planning to reuse spent foundry sand in Colorado? This guide covers the rules that apply, the tests that decide how the sand can be managed, and what CDPHE 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 Colorado, CDPHE approves uses not on its pre-approved list by issuing a Beneficial Use Determination (BUD).

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.

Colorado’s beneficial use rule

Colorado’s beneficial use rule is 6 CCR 1007-2, Part 1, Section 8.6. CDPHE keeps four tables that the rule relies on:

1. Table 1A: Category 1 total elemental analysis;
2. Table 1B: Category 1 and 2 analyte mobility analysis;
3. Table 2: allowed beneficial uses by category; and
4. Table 3: pre-approved beneficial uses.

A use on Table 3 needs no prior approval if it meets the Section 8.6.2 standards. Table 3 lists specific materials, such as coal fly ash, waste tires, reclaimed asphalt and concrete, lead-free glass, and steel slag. Spent foundry sand is not on Table 3, so its reuse needs a BUD from CDPHE.

For a BUD, the sand must be characterized and must not be hazardous waste. CDPHE then assigns a category:

1. Category 1: results below the Table 1A and 1B levels.
2. Category 2: results below the Table 1B mobility levels.
3. Category 3: non-hazardous waste used to solidify liquid waste at the same permitted disposal facility.

Every use must follow engineering or product specifications, show a benefit, and actually replace a commercial product or raw material. It may not harm groundwater quality.

Stockpiles have a limit. At least 90 percent of the recyclable material received and in storage must be recycled, measured over a three-year rolling average.

Applying to CDPHE

• Who files: the waste generator or user submits characterization results, the proposed category, and estimated quantities before the use begins.
• How: use CDPHE’s “Application for a solid waste beneficial use determination.” Consult the division at (303) 692-3320 before you start.
• Attachments: describe the sand, how it is generated, the proposed use, and storage methods. Compare it with the material it replaces. Estimate the quantity and include any local government acceptance.
• Fees: CDPHE charges a review fee of $125 per hour, whether or not it approves. It invoices the fee in the calendar quarter after it issues the BUD.
• Changes: file the same form to re-characterize a material or modify an existing BUD.
• After approval: re-test on the rule’s schedule and submit results within 30 days. File an annual report by March 1. CDPHE may revoke the approval if the performance standards are not met.

CDPHE Hazardous Materials and Waste Management Division: (303) 692-3320, cdphe.hmrecycling@state.co.us.

Hazardous waste determination

Colorado’s hazardous waste rules are 6 CCR 1007-3. Part 261 identifies and lists hazardous waste, and Part 262 sets standards for generators.

Colorado adds an annual Solid and Hazardous Waste Commission fee. Small and large quantity generators pay it by September 15 each year (6 CCR 1007-3, Part 6, § 6.04).

Under 6 CCR 1007-3, § 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, CDPHE, 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.

For a BUD, CDPHE requires total elemental analysis for Category 1 and mobility analysis for Categories 1 and 2. Use EPA SW-846 methods unless CDPHE approves others, and show the sand suits the use by geotechnical or other suitable methods.

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.

CDPHE decides uses outside Table 3 case by case. Check any destination and proposed use with CDPHE before scheduling delivery.

After characterization, use Table 2 to find the uses allowed for your sand’s category. Waste may not go below groundwater or into permanent standing water unless it is part of a solidified use shown not to affect groundwater. 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. Plan volumes to meet the 90 percent recycling rate over a three-year rolling average. Before you stop a beneficial use, remove stored waste and notify CDPHE in writing.

Keep the waste determination, lab reports, the BUD, and the receiving site’s acceptance together. Record tonnage shipped, dates, and destinations. Beneficial use operations keep records on site for at least the previous three years.

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 CDPHE BUD for that sand and use.
5. Get written acceptance and arrange pickup.

Common questions

Rules and guidance

• 6 CCR 1007-2, Part 1: Solid Waste Sites and Facilities
• CDPHE: Application for a solid waste beneficial use determination
• CDPHE: Beneficial use Table 3, pre-approved uses
• 6 CCR 1007-3, Part 261: Identification and Listing of Hazardous Waste
• 6 CCR 1007-3, Part 6: Solid and Hazardous Waste Commission Fees
• 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