Nonmetallic Mining Calculations Based on 1998 Nonmetallic Mining Agreement

Beginning in 1995, DNR worked with the Wisconsin Road Builders Association (now Wisconsin Transportation Builders Association), Aggregate Producers of Wisconsin (APW) and independent nonmetallic mining operators to determine an emission calculation scheme that could be applied consistently throughout the State of Wisconsin. Nonmetallic mining agreements were written in 1996, 1997, and 1998. DNR and the industry agreed to meet and update the 1998 agreement when USEPA updated emission factors in either AP42 (exit DNR) Section 3.3 Gasoline and Diesel Industrial Engines (exit DNR) or Section 11.19.2 Crushed Stone Processing (exit DNR). Although USEPA updated Section 11.19.2 (exit DNR) there has been no plans to meet between DNR and industry to discuss the updating of the 1998 agreement which is contained in the document, Nonmetallic Mining Air Emissions Guidance For the Development of the 1998 Air Emissions Inventory (PDF, 217KB), DNR Publication Number: PUBL-AM-268-98, January 1999. DNR uses the 1998 Nonmetallic Mining Agreement to calculate air emissions from existing and new crushing spreads. DNR also uses this agreement for calculating emissions for equipment that is used in other source categories. For example, conveyors are not only used by crushing spreads but also hot mix asphalt plants.

The agreement defined a typical crushing spread, identified the pollutants emitted at each piece of equipment, and assigned fugitive dust control efficiencies of 50%, 75%, or greater than 90%. As part of the agreement, DNR and industry developed a training course in which all or portions of the training course needed to completed annually in order for a crushing spread to obtain a greater than 50% control efficiency on pieces of equipment identified in the 1998 nonmetallic mining agreement. After the 1998 nonmetallic mining agreement was signed, DNR and industry worked further on determining what comprised haul road emissions. You may download the training course or nonmetallic mining agreement information either as single documents or bundled documents from this web site.

Typical Crushing Spread

DNR and the industry agreed there are many pieces of equipment that could comprise a rock crushing spread but that some of these pieces of equipment were common for all portable crushing spreads. The typical crushing spread was defined by the amount of rock output by the crushing spread.

  1. Crushing spread that produces under 50,000 tons of rock per year has the following minimum configuration
    • One primary crusher
    • Two conveyors
    • One loader
    • One unpaved haul road
    • One storage pile
  2. Crushing operation that produces more than 50,000 tons of rock per year and less than 300,000 tons of rock per year.
    • One primary crusher
    • One secondary crusher
    • One screen
    • One unpaved haul road
    • Four conveyors
    • Two storage piles
    • One loader
  3. Each crushing spread that produces more than 300,000 tons of rock per year
    • One primary crusher
    • One secondary crusher
    • One tertiary crusher
    • Three screens
    • One loader
    • One unpaved road
    • Six conveyors

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Air Pollutant Emissions

The agreement limited the SO2, NOx, CO, and ROG emissions to a few pieces of equipment and defined the PM and PM10 emissions for the additional pieces of equipment. Each emission factor was established and attached to a Source Classification Code (SCC). The SCC is used by the DNR computer database to assign emission factors to a certain piece of equipment and then calculate the emissions for that piece of equipment.

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Fugitive Dust Control Efficiency

DNR and the industry agreed that each particulate matter emitting process from a crushing spread should receive a fugitive dust control efficiency based on dust controls and the personnel trained to control fugitive dust at the crushing spread. The 1998 agreement set three different tiers of control (50%, 75%, greater than 90%). The emission factors listed in the particulate matter and PM10 tables in the 1998 agreement (PDF, 217KB) (pages 20-25) were adjusted upward so that when the control efficiency is applied the emission factors are correct. For example, the 50% particulate matter emission factor written in the table (page 20) is 0.00035 lb PM/ton of process throughput. The actual AP42 emission factor is 0.000175 lb PM/ton of process throughput. The emission factor is identical depending on the control efficiency assigned :

  • 50% control efficiency-Emission = throughput (tons stone ) * 0.00035 lb/ton stone * (1-0.50)
  • 0% control efficiency -Emission = throughput (tons stone ) * 0.000175 lb/ton stone * (1-0.00)

Tier 1 Control -50%

Because Wisconsin has regular precipitation (rain,snow), industry and DNR agreed that a 50% control would be assigned to all dust generating equipment in a crushing spread. This is an automatic control efficiency and the owner or operator of the crushing spread does not need to supply supporting information to achieve the 50% control efficiency. The facility is required to keep records for different pieces of equipment:

  • Screening, primary crushing, secondary crushing, tertiary crushing, fines crushing, loading grizzly-Document yearly throughput.
  • Conveyor transfer points-Document yearly throughput and minimize drop height
  • Haul to crusher using loader, haul truck traffic on unpaved haul roads, mine truck traffic on unpaved haul roads, stockpiles fed by unloading trucks-Document yearly throughput and speed control

Tier 2 Control - 75%

The crushing spread is assigned a 75% control efficiency for each dust generating piece of equpment if it meets personnel training requirements. The crushing spread must have an "On-site Fugitive Dust Observer" on-site during the nonmetallic mining operation or the operation is not eligible for the 75% control. The on-site fugitive dust observer must participate in a training course developed by DNR in cooperation with WTBA and APW , or complete another DNR approved training program to recognize when fugitive dust control measures need to be taken and what measures are appropriate. Once the person completes the training the on-site fugitive dust observer needsto sign the table in Appendix F of the 1998 agreement, keep that record at the crushing plant, and supply this training record to a DNR inspector during the site visit for verification of this training requirement. The training course consists of a training document (PDF, 706KB) with an accompanying film clip entitled "Pardon My Dust". [Please call Ralph Patterson at 608-267-7546 for a copy of a CD containing this film clip.] The training is supposed to be completed each year. The 1998 agreement allows one person to be the "trainer" for people working on different crushing spreads run by the same company. The facility is required to keep records for different pieces of equipment:

  • Screening, primary crushing, secondary crushing, tertiary crushing, fines crushing, loading grizzly-Document yearly throughput, log daily dust suppression activities and/or meteorological conditions at the site, and have on-site fugitive dust observer present during hours of crushing spread operation.
  • Conveyor transfer points-Document yearly throughput, log daily dust suppression activities and/or meteorological conditions at the site, properly maintain dust suppression equipment, and have on-site fugitive dust observer present during hours of crushing spread operation.
  • Haul to crusher using loader, haul truck traffic on unpaved haul roads, mine truck traffic on unpaved haul roads, stockpiles fed by unloading trucks-Document yearly throughput; record water truck use, street sweeper use, or use of alternative dust control measures and/or documentation of meteorological conditions; implement speed control at crushing site; and have on-site fugitive dust observer present during hours of crushing spread operation.

Tier 3 Control - Greater than 90%

For emission inventory purposes, DNR interprets greater than 90% control as 91% control. The intent of this dust suppression credit was to reward companies that have minimal visible emissions and therefore minimal dust. The requirements for greater than 90% control is the same as the 75% control requirements with two additions:

  • The company needs to have a "Visible Emission Reader" on staff. A "visible emission reader" is a person designated by the facility who has been certified at least once in the last twelve months to identify varying levels of visible emissions, using USEPA Method 9 criteria.
  • The company must document visible emissions at or below 10% once per 8 hour shift at site.

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Haul Road Emissions

Haul road emissions were discussed in depth with the nonmetallic mining industry in 1999, 2000, and 2001. Haul road emissions were characterized as any particulate emission from a haul road. Most of these emissions were entrained dust emissions from truck and loader traffic. The questions discussed by DNR and the industry were:

  • Who is responsible for reporting haul road emissions?
  • Are haul road emissions direct or indirect sources of particulate matter?

Based on further discussions with the industry and DNR, haul road emissions are categorized:

  • Indirect Source Haul Road Emissions

    • The entrance road should be accounted as an indirect source similar to other facilities that attract motor vehicles. These emission sources are currently not reportable under Chapter NR 438, Wis. Adm. Code.

  • Direct Source Haul Road Emissions

    • Emissions from the pit haul road to the crusher; crushing operation; and loading, unloading or stockpiling of materials are direct sources of particulate matter. These sources are assigned directly to the crusher. These emission sources are reportable under Chapter NR 438, Wis. Adm. Code

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Documents and Training

DNR and the nonmetallic mining industry developed a number of pieces of information applicable to the 1998 Nonmetallic Mining Agreement that you may download from this web page:

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Last Revised: Thursday January 08 2009