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Table of Contents - Training Module
Disclaimer / Notice
- The following notes and comments are those of the authors and do not necessarily reflect the views and policies of NC DENR. The authors welcome and encourage any comments or feedback from any interested person or party. Please email comments or call us:
tom.mckinney@ncmail.net
(910) 486-1541 ext. 615
sally.mckinney@ncmail.net
(910) 486-1541 ext. 605
- Truck Mix emission factors versus Central Mix emission factors.
- Arsenic data for NC Air Toxics versus PM10 data for Facility Classif.
- Prohibitory Small (2Q .0809) for Concrete Batch Plants
- TPER versus AAL.
- 2Q .0711 versus 2D .1100.
- Maximum actual emissions versus potential emissions.
- New Facility or Modification with Net Increase in TAP emissions.
- Triggering 2Q .0711 versus Triggering 2D .1100.
- Modeling inputs (emission sources, rates, locations, stack data, etc.).
- 2Q .0711 permit condition versus 2D .1100 permit condition.
- Arsenic data provided for silos and truck/central mix area.
- Arsenic data for cement/suppl weigh hopper not separated from truck/central mix data.
- Arsenic emission estimates for the silos based on EPA2001 data.
- Arsenic emission estimates for the truck/central mix based on ATC2005 data.
- For modeling Arsenic, uncontrolled truck/central mix area treated as volume source.
- For controlled truck/central mix, 50% modeled as volume source, 50% modeled as point source.
- Facility classif. based only on sum of silos and cement/suppl weigh hopper PM10 data.
- PM10 emissions for silos and cement/suppl weigh hopper based on EPA2001 factors.
- DAQ uses sand/aggr weigh hopper data to estimate cement/suppl weigh hopper emissions.
- Prohibitory Small (2Q .0809) option if silos and cement/suppl weigh hopper are controlled.
- Sand/Aggr handling and weigh hopper treated as insig. activities for permits.
- Calculations for 2D .0515 are based on EPA2001 data.
- DAQ uses sand/aggr weigh hopper data to estimate cement/suppl weigh hopper emissions.
(Truck Mix, 120 yd3/hr, No Loadout Controls, Controls on WH/CementSilo/SupplSilo)
- Question 1: Was this a new facility or modification with a net increase in TAPs?
Answer: Yes. This was a new facility (relocation of an existing plant) with a net increase in arsenic and other trace TAP emissions.
- Question 2: Did the existing permit include 2Q .0711 or 2D .1100?
Answer: No. This was a greenfield (relocation of existing concrete batch plant) receiving a new permit (R00).
- Question 3: Would any TAPs, with a net increase in emissions, exceed the TPERs?
Answer: Yes. The maximum actual facility-wide emissions of arsenic would exceed the TPER if the facility produced more than 880 cubic yards per year. Based on the modified 2005 DAQ spreadsheet, this reflects the following arsenic emissions data: SupplSilo = 0.00005 lbs/yr; CementSilo = 0.0000008 lbs/yr; and Truck Mix = 0.0159 lbs/yr. We have included the silo emissions in the facility-wide comparison to the TPER since the ATC2005 test does not reflect emissions from the loading of the silos.
- Therefore: Rather than accept a limit of 880 yd3 per year in their permit, the facility decided to conduct dispersion modeling.
- Question 4: Which emission rates are used to conduct the modeling?
Answer: The modified 2005 DAQ spreadsheet provides the following arsenic emission rates for a maximum production of 20,000 yd3 per year, which modeling shows will keep the facility just below the AAL for arsenic: SupplSilo = 0.0012 lbs/yr; CementSilo = 0.000017 lbs/yr; and Truck Mix = 0.36 lbs/yr. The cement silo and supplement silo arsenic emissions are based on EPA2001 emissions factors and the truck mix arsenic emissions are based on ATC2005. The DAQ modeled the truck mix emissions as a volume source.
- Therefore: Rather than accept a limit of 880 yd3 per year in their permit, the facility decided to conduct dispersion modeling and have a much higher limit on production.
- Question 5: What were the results of the modeling?
Answer: The modeling showed that the facility complies with the AAL for arsenic as long as production does not exceed 20,000 yd3 per 12-month period.
- Therefore: The dispersion modeling was approved by DAQ and the 2D .1100 toxics condition for arsenic was placed in the permit. The permit condition included the 20,000 yd3 per 12-months limit and required annual reporting of concrete production. The facility is classified as small since the Title V potential emissions, based on the spreadsheet, are less than 100 tpy. The EPA2001 silo emission factors were used for the 2D .0515 calculations.
- Inspections: The inspector should verify that the emission sources, rates, and stack parameters match the modeling inputs and permit condition AND verify that the 2D .1100 requirements are being met.
- What If: If the facility makes changes that will increase emissions or alter the emission locations or stack parameters for arsenic, they must demonstrate to DAQ that the AAL will not be exceeded.
(Central Mix, 200 yd3/hr, with Central Controls for CentralMix/WH/CementSilo/SupplSilo)
- Question 1: Was this a new facility or modification with a net increase in TAPs?
Answer: Yes. This was a new facility with a net increase in arsenic and other trace TAP emissions.
- Question 2: Did the existing permit include 2Q .0711 or 2D .1100?
Answer: No. This was a greenfield receiving a new permit (R00).
- Question 3: Would any TAPs, with a net increase in emissions, exceed the TPERs?
Answer: Possibly. The maximum actual facility-wide emissions of arsenic would exceed the TPER if the facility produced more than 54,000 cubic yards per year. Based on the modified 2005 DAQ spreadsheet, this reflects the following arsenic emissions: SupplSilo = 0.003 lbs/yr; CementSilo = 0.00005 lbs/yr; and Central Mix = 0.013 lbs/yr. We have included the silo emissions in the facility-wide comparison to the TPER since the ATC2005 testing does not reflect emissions from the loading of the silos.
- Therefore: The facility decided to accept a 54,000 cubic yards per year limit, with annual reporting, to be included as a 2Q .0711 condition in their permit. This is essentially a "toxics avoidance" permit condition.
- Inspections: The inspector should check facility records and the annual report to verify that the 2Q .0711 production limit was not exceeded.
- What If: If the facility wants to increase production above 54,000 cubic yards per year, they must conduct dispersion modeling (2D .1100) to assure that the arsenic AAL is not exceeded at the property boundary.
(Truck Mix, 150 yd3/hr, with Central Controls for TruckMix/WH/CementSilo/SupplSilo)
- Question 1: Was this a new facility or modification with a net increase in TAPs?
Answer: Yes. This was a new facility with a net increase in arsenic and other trace TAP emissions.
- Question 2: Did the existing permit include 2Q .0711 or 2D .1100?
Answer: No. This was a greenfield receiving a new permit (R00).
- Question 3: Would any TAPs, with a net increase in emissions, exceed the TPERs?
Answer: Possibly. The maximum actual facility-wide emissions of arsenic would exceed the TPER if the facility produced more than 33,000 cubic yards per year. (See modified 2005 DAQ spreadsheet.)
- Therefore: Rather than accept a limit of 33,000 yd3 per year in their permit, the facility decided to conduct dispersion modeling.
- Question 4: Which emission rates are used to conduct the modeling?
Answer: The modified 2005 DAQ spreadsheet provides the following arsenic emission rates for a maximum production of 110,000 yd3 per year, which modeling shows will keep the facility just below the AAL for arsenic: total Truck Mix area arsenic emissions = 0.053 lbs/yr. The silo arsenic emissions are not modeled individually since those emissions are routed to the central control system. However, the silo arsenic emissions make a small contribution to the total truck mix area arsenic emissions and were included in the total. The DAQ modeled 50% of the total truck mix arsenic emissions (0.027 lb/yr) as a fugitive volume source and the other 50% of the emissions (0.027 lb/yr) as a point source associated with the control device.
- Therefore: Rather than accept a limit of 33,000 yd3 per year in their permit, the facility decided to conduct dispersion modeling.
- Question 5: What were the results of the modeling?
Answer: The modeling showed that the facility complies with the AAL for arsenic as long as production does not exceed 110,000 yd3 per 12-month period.
- Therefore: The dispersion modeling was approved by DAQ and the 2D .1100 toxics condition for arsenic was placed in the permit. The permit condition included the 110,000 yd3 per 12-months limit, based on central controls, and required annual reporting of concrete production. Based on the modified 2005 DAQ spreadsheet, the Title V potential emissions exceed 100 tpy. However, since the emissions from the silos and the cement and supplement weigh hopper are controlled, the facility was able to use 2Q .0809 for prohibitory small to avoid a synthetic minor classification. The EPA2001 silo emission factors were used for the 2D .0515 calculations.
- Inspections: The inspector should verify that the emission sources, rates, and stack parameters match the modeling inputs and permit condition AND verify that the 2D .1100 requirements are being met.
- What If: If the facility makes changes that will increase emissions or alter the emission locations or stack parameters for arsenic, they must demonstrate to DAQ that the AALs will not be exceeded.
(Truck Mix, 120 yd3/hr, No Loadout Controls, Controls on WH/CementSilos, No Supplement)
- Question 1: Was this a new facility or modification with a net increase in TAPs?
Answer: Yes. This was a new facility with net increase in arsenic and other trace TAP emissions.
- Question 2: Did the existing permit include 2Q .0711 or 2D .1100?
Answer: No. This was a greenfield receiving a new permit (R00).
- Question 3: Would any TAPs, with a net increase in emissions, exceed the TPERs?
Answer: Yes. The maximum actual facility-wide emissions of arsenic would exceed the TPER if the facility produced more than 880 cubic yards per year. This production limit is identical to Example 1 above, even though the facility does not use supplement. This is because the arsenic emissions total from the truck mix is several orders of magnitude greater than the arsenic emissions from a hypothetical supplement silo. Future testing and analysis may provide DAQ with data to better characterize the truck mix arsenic emissions for a facility that does not use supplement.
- Therefore: Rather than accept a limit of 880 yd3 per year in their permit, the facility decided to conduct dispersion modeling.
- Question 4: Which emission rates are used to conduct the modeling?
Answer: The modified 2005 DAQ spreadsheet provides the following arsenic emission rates for a maximum production of 250,000 yd3 per year, which modeling shows will keep the facility just below the AAL for arsenic: CementSilo1 = 0.00014 lbs/yr; CementSilo2 = 0.00014 lbs/yr; and Truck Mix area = 4.5 lbs/yr. The cement silo arsenic emissions shown on the modified 2005 DAQ spreadsheet are divided between the two cement silos. The silo arsenic emissions are based on EPA2001 and the truck mix arsenic emissions are based on ATC2005. The DAQ modeled the truck mix emissions as a volume source.
- Therefore: Rather than accept a limit of 880 yd3 per year in their permit, the facility decided to conduct dispersion modeling.
- Question 5: What were the results of the modeling?
Answer: The modeling showed that the facility complies with the AAL for arsenic as long as production does not exceed 250,000 yd3 per 12-month period.
- Therefore: The dispersion modeling was approved by DAQ and the 2D .1100 toxics condition for arsenic was placed in the permit. The permit condition included the 250,000 yd3 per 12-months limit and required annual reporting of concrete production. The facility is classified as small since the Title V potential emissions, based on the spreadsheet, are less than 100 tpy. The EPA2001 silo emission factors were used for the 2D .0515 calculations.
- Inspections: The inspector should verify that the emission sources, rates, and stack parameters match the modeling inputs and permit condition AND verify that the 2D .1100 requirements are being met.
- What If: If the facility makes changes that will increase emissions or alter the emission locations or stack parameters for arsenic, they must demonstrate to DAQ that the AAL will not be exceeded.
(Truck Mix, 120 yd3/hr, No Loadout Controls, Controls on WH/CementSilo/SupplSilo)
- Question 1: Was this a new facility or modification with a net increase in TAPs?
Answer: No. This was a permit renewal.
- Question 2: Did the existing permit include 2Q .0711 or 2D .1100?
Answer: No. Looking back over the past 4 years there is no history of a modification with a net increase in TAPs. The last permit revision was in 2000 for a permit renewal. The greenfield permit was issued in 1998, but this was prior to the DAQ procedural changes (during 2001-2002 period) that began the possible triggering of toxics modeling for arsenic at concrete batch plants.
- Question 3: Did the permit review indicate they have ever exceeded the TPERs?
Answer: Yes. They have exceeded the TPER values, but 2Q .0711 and 2D .1100 have never been triggered.
- Therefore: The facility continues to be "grandfathered" for toxics.
- Inspections: The inspector should verify that the facility has not made a modification since October 2001 that would require a permit application and a review of toxics.
- What If: If the facility makes a modification with a net increase in TAPs, they must accept an annual production limit in their permit or conduct dispersion modeling (2D .1100) to assure that the AAL for arsenic is not exceeded at the property boundary.