Foundry Sand Reuse in Wisconsin

Planning to reuse spent foundry sand in Wisconsin? This guide covers the rules that apply, the tests that decide how the sand can be used, and what DNR 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. Wisconsin’s rule calls it “beneficial use”: using an industrial byproduct in a productive manner. Ferrous, steel, and aluminum foundry sand is a listed industrial byproduct.

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.

Wisconsin’s NR 538 foundry sand rules

Wisconsin’s beneficial use rule is ch. NR 538, Beneficial Use of Industrial Byproducts. It lists ferrous, steel, and aluminum foundry sand as an industrial byproduct (NR 538.03(8)). Foundry sand means spent silica-based molding and core sand from metal casting. It includes dry baghouse and wet collector sand fines collected at the foundry during casting (NR 538.03(6)).

An industrial byproduct must come from an industrial process and have consistent physical and chemical properties. Material that was previously disposed of or landfilled is not an industrial byproduct. Hazardous waste is outside NR 538 (NR 538.02(1)).

Foundry sand that is characterized and used in compliance with NR 538 is exempt from solid waste licensing under s. 289.31, Stats., and from chs. NR 500 to 528 (NR 538.05). The exemption covers the people who generate, use, transport, or store it.

Eligible use groups

NR 538.08 sets the eligible uses from the test results. The water leach standards in Appendix Table 1 have two columns. Column B decides which uses are eligible. Column A decides how far fill must stay above groundwater.

• Contained or converted uses: open to all foundry sand that is determined not hazardous and tested under NR 538.06.
• Geotechnical fill and construction uses: sand below Table 1, Column B.
• Unconfined uses: sand below Table 1, Column B and the Table 2 bulk standards.
• Nonmetallic mine reclamation fill: select foundry sand, or sand below Table 1, Column A.

Select foundry sand

Select foundry sand is a higher grade defined in NR 538.03(12m). It is spent green molding sand, resin bonded molding sand, or core sand. Its main parts are silica sand, bentonite clay, and carbon additives such as bituminous coal, gilsonite, and cellulose.

It may include nominal amounts of spent riser sleeves and ceramic filters. It may not include uncured chemically bonded sand, or debris beyond trace amounts. It must test below Table 1, Column B.

Request the designation with your initial certification or recharacterization. Send evidence of segregation, such as process flow diagrams, written handling and segregation procedures, or byproduct management summaries (NR 538.06(3)(f)). DNR replies within 10 business days. If it does not respond in that time, concurrence is considered granted.

Select foundry sand can be used as fill in nonmetallic mine reclamation. In other geotechnical fill, it needs 3 feet of separation from groundwater instead of 5 (NR 538.12(2)).

Case-specific approvals

Under NR 538.09, DNR may approve or conditionally approve a use that falls outside the chapter’s listed uses or standards. DNR may require a case-specific approval when sand gets deliberate processing after accumulation. Size reduction, sorting, and adding water for handling or dust control do not count (NR 538.06(2)).

If you mix separate byproducts, each one must be eligible for the final use of the mixture, unless DNR approves otherwise in writing (NR 538.06(4)). If DNR finds a material is not an industrial byproduct, or a use is not beneficial, approval comes through chs. NR 500 to 528 instead.

Certifying with DNR

• Who files: the generator or the generator’s designee. A person the generator designates, such as a broker, may submit project notifications.
• When: file an initial certification before any beneficial use. File one for any byproduct not previously approved for eligible uses, for any byproduct whose generating process has changed, and before setting up a storage facility (NR 538.14(1)).
• How: characterize the sand under NR 538.06 and report the results on the Initial Certification, Form 4400-197.
• Contents: generator name, address, and contact; a description of each byproduct, the process that makes it, and its estimated annual volume; test results and the eligible uses they support; hazardous waste determination records; and authorization for DNR to inspect and sample. Sign a certification that the information is true and the performance standards will be met.
• Review: DNR replies in writing within 10 business days. It may concur, ask for more information or analysis, require a case-specific approval, or not concur. If DNR does not respond in 10 business days, concurrence is considered granted.
• After concurrence: many eligible uses can proceed without specific approval. Some geotechnical fill projects need written notice and DNR concurrence first.
• Recertification: recharacterize every 4 years and after a process change that could change eligible uses. Submit within 60 days after receiving results that point to a change in eligible uses. Results that confirm the current uses may go with the annual certification (NR 538.14(2)).
• Annual certification: report the previous calendar year by April 1. List the volume used for each type of use. If you gave or sold sand to someone else, list each recipient’s name, address, volume, and intended uses (NR 538.14(3)). DNR uses an online reporting system; Form 4400-198 is available for those who cannot use it.

DNR beneficial use program: dnrbeneficialusereporting@wisconsin.gov, or Beneficial Use Coordinator - WA/5, PO Box 7921, Madison, WI 53707-7921.

Hazardous waste determination

Wisconsin’s hazardous waste rules are chs. NR 660 to 679 of the Wisconsin Administrative Code. Their section numbers follow 40 CFR. The toxicity characteristic is NR 661.0024.

NR 538 requires this determination before any other step. Each byproduct must first be shown not to be hazardous waste using a method under NR 662.011. Send the supporting records with the initial certification (NR 538.06(3)(b)). They may include sampling and analysis, safety data sheets, published information, process flow diagrams, profiles from past handling, or supported process knowledge.

Under Wis. Admin. Code NR 662.011, 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.

NR 538 testing and TCLP 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, DNR, 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.

NR 538 adds its own tests. Take a representative sample at the point of accumulation nearest to where the sand is generated. Run the ASTM D3987-12 water leach test and a bulk analysis. Use EPA SW-846 methods unless DNR approves others in writing. Report the limit of detection and limit of quantitation with each result (NR 538.06(3)).

A result at or above a standard counts as an exceedance. When a standard falls below the lowest achievable detection limit, NR 538.08(6) sets how to read the result.

Eligible uses for foundry sand

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.

Once DNR concurs with your certification, the uses in NR 538.10 that your results support may proceed. Each use must meet the structural and physical specifications and accepted engineering practice for that use. Many fill, base, and surface uses are prohibited in residential areas.

• Contained or converted: ingredients in cement, lightweight aggregate, concrete, ceramics, asphalt pavement, and other products DNR approves in writing. Also stabilization agents for waste going to a licensed landfill, and daily cover or internal structures at lined landfills with leachate collection. Alternate daily cover may have no more than 15% silt and clay sized material and no layer over 6 inches thick.
• Geotechnical fill: subgrade fill under commercial, industrial, or non-residential institutional buildings and under paved lots and private roads. Also covered fill for berms, trails, sporting venues, limited use parking, and access lanes; transportation embankments; and nonmetallic mine reclamation. Subgrade fill for residential buildings is prohibited.
• Livestock operations: foundry sand may line manure, feed, or process wastewater storage structures, or serve as fill under livestock housing. Build to NRCS standards and local ordinances (NR 538.10(2)(d)).
• Construction: paved public roadway subgrade fill up to 4 feet deep; base aggregates that meet WisDOT Section 301; utility trench backfill under pavement; filling abandoned tanks, vaults, or tunnels; slabjacking; flowable fill; and bonded surface course. Keep these out of standing water and areas that need dewatering.
• Unconfined: unbonded surface course up to 6 inches thick, with a 25-foot vegetated buffer to navigable water. Also “winter weather road abrasive” on roads with a rural cross-section, and manufactured soil blends.
• Manufactured soil: blends made with spent silica-based sand from iron, steel, and aluminum foundries may contain no more than 50% foundry sand by weight. They must be meant as a commercial or consumer product. Bulk land application on farm fields falls under ch. NR 518.

Geotechnical fill limits

• Send DNR written notice and get concurrence before any project over 5,000 cubic yards and any nonmetallic mine reclamation project. DNR replies within 10 business days; no reply means concurrence is granted (NR 538.14(6)).
• Keep fill at least 3 feet above groundwater for select foundry sand or sand below Column A. Keep it 5 feet above for sand between Columns A and B, and for mine reclamation.
• Do not place fill in floodplains or below the ordinary high-water mark without DNR’s prior written approval.
• Keep projects over 5,000 cubic yards at least 100 feet from water wells, unless DNR concurs with a smaller distance.
• Where fill is not under a building or pavement, cover it with 2 feet of native soil, including 4 inches of topsoil. Keep vegetated slopes no steeper than 3:1.
• Finish placement and final cover within 12 months of first accepting sand, or 16 months if the site is fenced and signed. Phase longer projects.
• Projects using 100,000 cubic yards or more need a case-specific approval.
• Projects over 30,000 cubic yards need a newspaper public notice at least 30 business days before starting (NR 538.18).
• Give each property owner written notice before placing fill, and send DNR a copy. Over 10,000 cubic yards, record an affidavit with the register of deeds within 60 business days after placement (NR 538.22).
• Mine reclamation also needs an approved NR 135 reclamation plan that provides for the fill.

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. NR 538.16 sets the storage design. Sand below Table 1, Column B needs a pad of impervious surface, compacted soil, or at least one foot of aggregate. Sand above Column B needs an impervious pad, or a clay pad under at least one foot of gravel, surrounded by curbs or berms.

Mark the storage area and line three sides with curbs, blocks, or berms. Enclosed storage, such as a building, silo, or roll-off box, is exempt. Temporary off-site staging is limited to 16 months, with written notice to DNR of the location, start date, and volume. Haul in leak-proof vehicles, cover loads as needed, and recover any spills.

Keep the waste determination, lab reports, DNR concurrences, and the receiving site’s acceptance together. Record tonnage shipped, dates, and destinations. Keep records of where sand was used as geotechnical fill for 5 years after use (NR 538.14(8)). Keep determination records for at least 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 run the NR 538 water leach and bulk tests.
3. File Form 4400-197 and get DNR concurrence on the eligible uses.
4. Choose a destination, get its material specifications, and file any required project notice.
5. Get written acceptance and arrange pickup.

Common questions

Rules and guidance

• Wisconsin DNR: Beneficial use of industrial byproducts
• Ch. NR 538: Beneficial Use of Industrial Byproducts
• Ch. NR 538 Appendix: Characterization standards
• DNR WA-1769: Guidance for the Beneficial Use of Industrial Byproducts
• DNR Form 4400-197: Initial Certification
• DNR Form 4400-198: Annual Certification
• NR 662.011: Hazardous waste determination and recordkeeping
• NR 661.0024: Toxicity characteristic
• 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