10/ 2 7 / 2011 1 MEMORANDUM

TO: Conrad Chin, U.S. Environmental Protection Agency, OAQPS

FROM: Beth Friedman, Jeff Harris, and Brad Nelson, EC/R

DATE : October 2 7 , 2011

SUBJECT: Draft Technology Review for the Ferroalloys Production Source Category

This memorandum summarizes the results of an analysis to identify developments in practices, processes, and control technologies for emissions sources of hazardous air pollutants (H AP) from the ferroalloys production source category. This analysis is part of EPA’s review efforts in accordance with section 112(d)(6) of the Clean Air Act (CAA). This memorandum is organized as follows:

1.0 Background 1.1 Requirements of Section 112(d)(6) of the CAA 1.2 Description of the Ferroalloys Production Source Category and Requirements of the Current NESHAP 2.0 Developments in Practices, Processes and Control Technologies
2.1 Stack Emissions 2.2 Fugitive Emissions
3.0 Recommended Re visions Based on Developments in Practices, Processes and Control Technologies
3.1 Stack Emissions 3.2 Fugitive Emissions
4.0 Conclusions

1.0 BACKGROUND
1.1 Requirements of Section 112(d)(6) of the CAA Section 112 of the CAA requires EPA to establish technology

- based standards for sources of HAP. These technology

- based standards are often referred to as maximum achievable control technology, or10/ 2 7 / 2011 2 MACT, standards. Section 112 also contains provisions requir ing EPA to periodically revisit these standards. Specifically, paragraph 112(d)(6) states:

(6) REVIEW AND REVISION.

– The Administrator shall review, and revise as necessary (taking into account developments in practices, processes, and contr ol technologies), emissions standards promulgated under this section no less often than every 8 years.

1.2 Description of the Ferroalloys Production Source Category and Requirements of the
Current NESHAP
The current National Emissions Stand ards for Hazardous Air Pollutants (NESHAP) for Ferroalloys Production: Ferromanganese and Silicomanganese was promulgated on May 20, 1999 (64 FR 27450) and codified at 40 CFR part 63, subpart XXX. The 1999 NESHAP (40 CFR 63.1650(a)) applies to all
new and existing ferroalloys production facilities that manufacture ferromanganese or silicomanganese and are major sources or are co

- located at major sources of HAP emissions. The rule’s product

- specific applicability reflected the only known major source at the time of promulgation.

Today, there are two ferroalloys production facilities subject to the MACT rule. No new manganese ferroalloys production facilities have been built in over 20 years, and we anticipate no new ferroalloys production facilities in the foreseeable future, alth ough one facility is currently exploring expanding operations.

Ferroalloys are alloys of iron in which one or more chemical elements (such as chromium, manganese, and silicon) are added into molten metal. Ferroalloys are consumed primarily in iron and st eel making and are used to produce steel and cast iron products with enhanced or special properties.

HAP generating processes at Ferroalloys facilities include electrometallurgical (furnace) operations (primary and tapping), other furnace room operations (ladle treatment and casting)
, raw material handling and product handling. HAP are emitted from ferroalloys production as process emissions, process fugitive emissions, and outdoor fugitive dust emissions.

Process emissions are the exhaust gases from the control devices, primarily the furnace control device, metal oxygen refining control device and crushing operations control device. The HAP in process10/ 2 7 / 2011 3 emissions are primarily composed of metals (mostly manga nese, arsenic, nickel, lead, mercury and chromium) and also may include organic compounds that result from incomplete combustion of coal or coke that is charged to the furnaces as a reducing agent. There are also process metal HAP emissions from the produc t crushing control devices. Process fugitive emissions occur at various points during the smelting process (such as during charging and tapping of furnaces and casting) and are assumed to be similar in composition to the process emissions. Outdoor fugitive dust emissions result from the entrainment of HAP in ambient air due to material handling, vehicle traffic, wind erosion from storage piles, and other various activities. Outdoor fugitive dust emissions are composed of metal HAP only.

The MACT rule appli es to process emissions and process fugitive emissions from the submerged arc furnaces, the metal oxygen refining process, and the product crushing equipment and outdoor fugitive dust emissions sources such as roadways, yard areas, and outdoor material sto rage and transfer operations. For process sources, the NESHAP specifies numerical emissions limits for particulate matter (as a surrogate for non

- mercury metal HAP) from the electric (submerged) arc furnaces (including primary and tapping emissions), depen ding on furnace type, size, and product being made. Particulate matter emission limits (again as a surrogate for non

- mercury metal HAP) are also in place for the metal oxygen refining process and product crushing and screening equipment. Table 1 is a summa ry of the applicable limits.

The 1999 NESHAP established a building opacity limit of 20 percent that is measured during the required furnace control device performance test. The rule provides an excursion limit of 60 percent opacity for one 6

- minute perio d during the performance test. The opacity observation is focused only on emissions exiting the shop due solely to operations of any affected submerged arc furnace. In addition, blowing taps, poling and oxygen lancing of the tap hole; burndowns associated with electrode measurements; and maintenance activities associated with submerged arc furnaces and casting operations are exempt from the opacity standards.

. For outdoor fugitive dust sources, the 1999 NESHAP requires that plants operate according to an ou tdoor fugitive dust control plan that describes in detail the measures that will be put in place to control outdoor fugitive dust emissions from the individual outdoor fugitive dust sources at the facility

.10/ 2 7 / 2011 4 Table 1 . Emission Limits in Subpart XXX

New or Reconstructed or Existing Source Affected Source Applicable PM Emission Standards

New or reconstructed Submerged arc furnace 0.23 kilograms per hour per megawatt (kg/hr/MW) (0.51 pounds per hour per megawatt (lb/hr/MW) or 35 milligrams per dry standard cubic meter (mg/dscm) (0.015 grains per dry standard cubic foot (gr/dscf)
Existing Open submerged arc furnace producing ferromanganese and operating at a furnace power input of 22 megawatts (MW) or less 9.8 kg/hr (21.7 lb/hr)

Existing Open submerged arc furnace producing ferromanganese and operating at a furnace power input greater than 22 MW 13.5 kg/hr (29.8 lb/hr)

Existing Open submerged arc furnace producing silicomanganese and operating at a furnace power input greater than 25 MW 16.3 kg/hr (35.9 lb/hr)

Existing Open submerged arc furnace producing silicomanganese and operating at a furnace power input of 25 MW or less 12.3 kg/hr (27.2 lb/hr)

Existing Semi

- sealed submerged arc furnace (primary, tapping, and vent stacks) producing ferromanganese 11.2 kg/hr (24.7 lb/hr)

New, reconstructed, or existing Metal oxygen refining process 69 mg/dscm (0.03 gr/dscf)

New or reconstructed Individual equipment associated with the product crushing and screening operation 50 mg/dscm (0.022 gr/dscf)

Existing Individual equipment associated with the product crushing and screening operation 69 mg/dscm (0.03 gr/dscf)10/ 2 7 / 2011 5 2.0 DEVELOPMENTS IN PRAC TICES, PROCESSES AND CONTROL TECHNOLOGIES Our technology review focused on the identification and evaluation of developments in practices, processes, and control technologies that have occurred since the 1999 NESHAP was promulgated. In cases where the technology review identified such developments, we conducted an analysis of the technical feasibility of applying these developments, along with the estimated impacts (costs, emissions reductions, risk reductions, etc.) of applying these developments. 1 We then made decisions on whether it is necessary to propose amendments to the regulation to require any of the identified developments.

Based on our analyses of the data and information collected by the ICR and our general understanding of the industry and other available information on potential controls for this industry, we identified several potential developments in practices, processes, and control technologies. For the purpose of this exercise, we considered any of the following to be a “developme nt”:

• Any add

- on control technology or other equipment that was not identified and considered during development of the 1999 NESHAP.

• Any improvements in add

- on control technology or other equipment (that were identified and considered during development of the 1999 NESHAP) that could result in significant additional
emissions reduction.

• Any work practice or operational procedure that was not identified or considered during development of the 1999 NESHAP.

• Any process change or pollution prevention alternativ e that could be broadly applied to the industry and that was not identified or considered during development of the 1999 NESHAP.

In addition to reviewing the practices, processes, or control technologies that were not considered at the time we developed t he 1999 NESHAP, we reviewed a variety of data sources in our evaluation of whether there were additional practices, processes, or controls to consider for the Ferroalloys Production industry. Among the data sources we reviewed were the NESHAP for various i ndustries that were promulgated after the 1999 NESHAP. We reviewed the regulatory requirements and/or technical

1 Details of costs and emissions reductions are available in Cost Impacts for the Ferroalloys Source Category , available in the docket for the Ferroalloys Production source category10/ 2 7 / 2011 6 analyses associated with these regulatory actions to identify any practices, processes, and control technologies considered in these efforts tha t could possibly be applied to emissions sources in the Ferroalloys Production source category, as well as the costs, non

- air impacts, and energy implications associated with the use of these technologies.

Additionally, we requested information from faci lities regarding developments in practices, processes, or control technology. Finally, we reviewed other information sources, such as s tate or local permitting agency databases and industry

- supported databases. The results of these analyses are presented i n the following sections.

Although not a development in technology, we also considered the feasibility of reducing emissions from pollutants that were not identified and regulated under the 1999 NESHAP, which focused solely on metal HAP. These pollutants are mercury, polycyclic aromatic hydrocarbons (PAH), hydrochloric acid (HCl), and formaldehyde.

2.1 Stack Emissions The current NESHAP specifies emissions limits for metal HAP (using PM as a surrogate) from stacks. This section of the technology review will focus on developments in practices, processes, and control technologies applicable to emissions of metal HAP and organic compounds from stacks.

2.1.1

. Metal H AP Emissions from Stacks Based on a review of the ICR responses, the most common control te chnology employed by the industry
to control emissions of PM as well as non

- mercury metal HAP from furnace , metal oxygen refining, and crushing/sizing stacks is fabric filtration (or baghouses). Several types of baghouses are currently used by the industry , with cleaning mechanisms including shaker, pulse jet, and reverse air, and including positive pressure and large custom negative pressure baghouses. One facility also uses a ventur i
scrubber on one of their furnace stacks. T he results from the ICR test p rogram showed that all of the sources of stack emissions are emitting at significantly lower levels than their MACT permitted levels.10/ 2 7 / 2011 7 2.1.2

. H Cl and F ormaldehyde E missions from F urnace S tacks Although HCl and formaldehyde emissions limits are not specified in the current NESHAP, we investigated technologies available for prevention and/or control of HCl and formaldehyde emissions
from furnace stacks

. . No facilities in the source category use add

- on control devices or work p ractices to limit emissions of these pollutants beyond what is normally achieved as co

- control of the emissions with particulate matter control device. There are available add

- on control devices, such as dry sorbent injection (DSI ) ( lime injection ) that is believed to be a viable control technology to reduce HCl
emissions from furnaces

. The DSI control system works by injecting a sodium

- based powder such as, Trona (Na 2 CO 3 ) or sodium bicarbonate (NaHCO 3 ) into the flue gas duct upstream of a baghouse used
for particulate control

. For the acid gases, the NaHCO 3 or Na 2 CO 3 reacts with HCl to form sodium chloride (NaCl), carbon dioxide (CO 2 ) and water (H 2 O)

. The NaCl is a solid which can be removed from the exhaust stream using a particulate control device

. This technology is currently used to reduce acid gas emissions from coal

- fired boilers and achieves up 90 percent reduction of HCl .

The capital cost for DSI is estimated to be quite high, both because of expensive sorbent material and
because t he use of sodium

- based DSI also affects the marketability and beneficial use of baghouse fly ash, which is currently used in the concrete, wallboard and asphalt products industries as well as road and bridge construction. The collected fly ash from DSI technologies would need to be disposed of in a landfill, and would prevent the current practice of reusing or selling baghouse dust and the resulting
waste reduction benefits.

A ctivated carbon (also called activated carbon injection) is a possible control technology f or formaldehyde emissions. However, the same disadvantages apply in terms of baghouse dust
contamination as for HCl control. Other c ontrol technologies used to reduce formaldehyde emissions include thermal incineration and catalytic oxidation

. However, the se control technologies are not technologically or economically feasible for EAF emissions because of the high volume of exhaust gas
that would need to be treated

.

2.1.3

. Mercury Emissions from Furnace Stacks Although mercury emissions limits are not spe cified in the current NESHAP, we investigated technologies available for prevention and/or control of mercury emissions from furnace stacks

. No10/ 2 7 / 2011 8 facilities in the source category use add

- on control devices or use work practices to limit emissions of

mercury emissions beyond what is normally achieved as co

- control of the emissions with the particulate
matter control device. We estimated that the bulk of mercury emissions are emitted from the furnace control devices as measured during the ICR test program. Bec ause of the magnitude of mercury emissions (estimated to be 540 pounds per year (lb/yr) at one plant and 140 lb/yr at the other plant), we evaluated potential add

- on control in the form of carbon beds or activated carbon injection. Based on
discussions with a vendor 2 , we determined that using a fixed bed carbon system for treating th e high
flow rate from furnace control devices is neither feasible n or practical.

The use of activated carbon injection is being considered in other recent NESHAP such as the Utility MACT NESHAP and the Portland Cement NESHAP, and mercury reductions of up to 90 percent should be achievable at ferroalloys production facilities. Based on our experience with mercury controls for
other combustion sources s uch as boilers, we conclude that activated carbon injection is a viable control technology in the Ferroalloys Production source category . However, we recognize the potential concern that use of these controls upstream of the particulate matter control devi ce may pose issues with fabric filter dust contamination or sludge contamination and may result in some waste products being classified as Resource Conservation and Recovery Act (RCRA) waste. In addition, some companies re

- use or sell their baghouse dust ( primarily for use in cement kilns). There is concern that even if the material meets quality standards, that re

- introduction of the dust into a furnace or kiln would cause the mercury to become unbound from the carbon and be emitted into the atmosphere.

Because of these concerns, w e reviewed control options that included putting the mercury controls downstream of the existing furnace baghouse to avoid the potential issues associated with upstream controls. Under this scenario, the activated carbon injecti on system would be followed by a “polishing” baghouse to capture the activated carbon for disposal. In the case of an existing furnace scrubber, we assumed the source could put the activated carbon injection system upstream of the scrubber, the carbon
woul d be captured by the scrubber and the resulting sludge treated according to the existing treatment process at the plant. Based on discussion with a vendor 3 and other control technology experts at EPA , we do not believe that the resulting carbon waste in ei ther scenario would trigger the RCRA compliance

2 Calgon Carbon Contact Report, August 17, 2011. 3 Albemarle Contact Report, August 22, 2011.10/ 2 7 / 2011 9 concerns raised by the companies. This is because once the mercury absorbs to the activated carbon, it will stay there until heated above 400 degrees Fahrenheit. The captured activated carbon should pass the Toxicity Characteristic Leaching Procedure test, which is an EPA test method used to characterize waste
as either hazardous or non

- hazardous for the purpose of disposal. 4 Therefore, the captured activated carbon would unlikely be considered hazardous waste and can be disposed of in a landfill.

2.1.4

. Polycyclic A romatic H ydrocarbons from F urnace S tack s Although PAH emissions limits are not specified in the current NESHAP, we investigated technologies available for prevention and/or control of PAH emissions from furnace stacks. Like mercury, no existing facilities in the source category control PAH or use work practices to limit emissions of PAH emissions beyond what is normally achieved by modest co

- control of the emissions with the particulate ma tter control device. Also like mercury, these pollutants may be controlled with a ctivated carbon injection technology. Because of this, emission reductions could be achieved via co

- control at no additional costs.

2.2 Fugitive Emissions
As outlined in se ction 1.2 of this memorandum, the pollutants emitted from fugitive emissions sources in this source category occur at various points during the smelting process (such as during charging and tapping of furnaces and casting) and are assumed to be similar in composition to the process emissions. Outdoor fugitive dust emissions result from the entrainment of HAP in ambient air due to material handling, vehicle traffic, wind erosion from storage piles, and other various activities. Outdoor fugitive
dust emission s are composed of metal HAP only.

2.2.1

. Metal HAP emissions from process fugitives
W e evaluated several options to improve and increase the capture and control of process fugitive sources. The two main options involve either local ventilation or building ventilation. Local ventilation is common in this industry, but performance varies due to design of the capture system, maintenance practices and control device capacity. Industry representatives have expressed concern that extensive retrofitting of local ventilation is complicated at existing facilities because of the need for material

mov ement using large overhead cranes and ladles.

4 Albemarle Contact Report, August 22, 2011.10/ 2 7 / 2011 10 We evaluated several options to improve capture of fugitive emissions via improvements in hood design and the addition of new capture systems (with emissions ducted to new or existing control devices). We
al so identified a furnace building ventilation system at a ferrosilicon producer, using a similar production process. This “system” is basically an enclosure of the furnace building with evacuation of
emission to a control device. We evaluated an option to enclose the furnace building(s) and evacuate the emissions to a control device(s) similar to the system used at the ferrosilicon producing facility
described above.

2.2.2

. Outdoor Fugitive Dust Emissions The existing rule has a requirement for an outdoo r fugitive dust control plan. We are unable to quantify HAP emissions from outdoor fugitive dust sources and did not identify any additional procedures or controls that could be expected to have a significant impact on these emissions.

3.0 RECOMMENDED REVISIONS BASED ON DEVELOPMENTS IN PRACTICES, PROCESSES, AND CONTROL TECHNOLOGIES Based on the analyses presented above, we are recommending the following revisions to the current NESHAP with regards to stack and fugitive emissions from the Ferroalloys Pro duction source category.

3.1 Stack Emissions
3.1.1

. Metal H AP Emissions from Stacks
As described in section 2.1.1 of this memorandum, the concentrations of PM emissions in stacks reported by this industry in the ICR are far below the level specified in the current NESHAP, indicating improvements in the control of PM emissions since promulgation of the current NESHAP. Our analysis indicates that this is primarily a result of improved performance of baghouses (and a scrubber at one facility.) Therefore, we recommend revising the current NESHAP to reflect the level of performance currently being achieved by facilities that implement well

- performing baghouses to control emiss ions of
PM and metal HAP from stacks.

We calculated the proposed emission limits based on a MACT floor UPL analysis, resulting in a proposed existing source furnace stack PM emissions limit of 24 mg/dscm and proposed new source
furnace stack emissions lim it of 9.3 mg/dscm. We also calculated a proposed stack emission limit of 1310/ 2 7 / 2011 11 mg/dscm for crushing and screening equipment that would apply to both new and existing sources.

The metal oxygen refining operation is a unique process, and so we only have a sin gle ICR test data point. Therefore, we calculated a proposed emissions limit for this source using the 99 percent UPL from the test data, resulting in a proposed limit of 3.9 mg/dscm that would apply to new and existing metal oxygen refining operation sour ces.

Based on our analyses, we expect that no additional controls would be required for the facilities to comply with these proposed PM limits.

3.1.2

. H Cl and F ormaldehyde E missions from F urnace S tacks
As described in section 2.1.2, there is an available add

- on control device believed to be a possible control technology to reduce HCl emissions from furnaces ( DSI )

. However, because of high capital cost and the likelihood that implementation of sorbent injection would prevent the current practice of reusing or selling baghouse dust and the resulting waste reduction benefits , we determined that it is not a feasible option for the Ferroalloys Production source category.

T he capital cost for DSI is estimated to be $10 per kilowatt for coal

- fired boil ers 5

. Converting this cost to an EAF produces an estimated capital cost of $625,000 for a 25 megawatt EAF 6

. However, the major cost of DSI systems is the sorbent 7

. The DSI control technology has a relatively high operating cost, which ranges from $3.4 to $ 5 per kilowatt

- year ($/kW

- yr) 8 , which averages to a cost of $263,000 a year for a 25 megawatt EAF

. In addition, there are currently only a few suppliers of Trona, which is primarily
mined in the western United States

. Therefore, transporting the supply of Trona to facilities in the eastern United States could increase the delivered cost of Trona from $150 per ton to approximately $200 per ton.

5 URS, Assessment of Technology Options Available to Achieve Reductions of Hazardous Air Pollutants, April 5, 2011. 6 Assumes 40 percent efficiency for the coal

- fired boiler. 7 Sargent & Lundy, IPM Model

– Revisions to Cost and Performance for APC Technologies, Dry Sorbent Injection Cost Development Methodology Final, August 2010. 8 URS, Assessment of Technology Options Available to Achieve Reductions of Hazardous Air Pollutants, April 5, 2011.10/ 2 7 / 2011 12 The use of sodium

- based DSI also affects the marketability and beneficial use of baghouse fly ash,
which is currently used in the concrete, wallboard and asphalt products industries as well as road and bridge construction

. This is because sodium

- based dry sorbents are soluble and contribute greatly to the
available alkali content

. As a result, fly ash produced w ith emissions controls systems employing
sodium

- based DSI technologies exceed the available alkali criteria established by the American Association of State Highway and Transportation Officials for concrete

. Therefore, the collected fly ash
from DSI techno logies would need to be disposed of in a landfill, and would prevent the current practice of reusing or selling baghouse dust and the resulting waste reduction benefits.

A ctivated carbon (also called activated carbon injection) is a possible control tech nology for formaldehyde emissions. However, the same disadvantages apply in terms of baghouse dust
contamination as for HCl control. We recognize the potential for some co

- control of formaldehyde emissions that would be achieved by using activated carbon i njection to control mercury emissions, but we were unable to quantify those reductions. Other c ontrol technologies used to reduce formaldehyde emissions include thermal incineration and catalytic oxidation

. However, these control technologies are
not techn ologically or economically feasible for EAF emissions because of the high volume of exhaust gas that would need to be treated.

3.1.3

. Mercury Emissions from Furnace Stacks As described in section 2.1.3 above, activated carbon injection is an available a dd

- on control device believed to be a viable control technology to reduce mercury emissions from furnaces

.

Using the concentrations of mercury in stacks reported by this industry in the ICR, we calculated a MACT floor (or 99 percent UPL) for exhaust mercury concentrations from existing furnaces to be 80 μg/dscm at 2 percent CO 2 . This MACT floor limit is higher than the actual emissions measured during the ICR performance tests at each plant. Therefore, we ant icipate that both of the existing sources would be able to meet this limit without installing additional controls. Because of our limited data set, we considered setting a MACT limit for existing sources based on the performance of the best performing

sou rce ( i.e. , based upon the test data used to calculate the MACT floor for new sources) such that the MACT limit for existing sources would be the same as the UPL MACT limit for new sources ( i.e. , 1610/ 2 7 / 2011 13 μg/dscm). We believe this level could be achieved by an ac tivated carbon injection system, which is a proven technology for mercury control.

3.1.4

. Polycyclic A romatic H ydrocarbons from F urnace S tack s As described in section 2.1.4 above, as with mercury, PAHs may be controlled with a ctivated carbon injection technology. Based on available stack test data for PAH and applying the 99 percent UPL, we
calculate d that the MACT floor limit for PAHs would be 887 μg/dscm. We also evaluated control performance that could be achieved via co

- co ntrol of mercury emissions with activated carbon injection as a beyond

- the

- floor option. Based on information from carbon vendors, an activated carbon system that is designed to achieve a 90 percent reduction in mercury emissions (which we expect would be applied to meet the proposed mercury standard discussed above) should also achieve a high degree of reduction in PAH with no additional costs. Assuming a 90 percent reduction from the calculated 99 percent UPL of 887 μg/dscm, the resulting limit would be 8 9 μg/dscm. Thus, a proposed limit for PAHs of 89 μg/dscm could be achieved with the same controls needed for mercury with no additional costs.

3.2 Fugitive Emissions
3.2.1

. Metal HAP emissions from process fugitives As described in section 3.2.1 above, we evaluated an option to enclose the furnace building(s) and evacuate the emissions to a control device(s). Based on that evaluation, we believe that it is feasible to install enclosures and have the fugitive emissions at the ridge vents of the shop build ing collected under negative pressure and ducted to a control device, with a PM emissions limit at the control device stack
outlet set at the same level as for the furnace stacks. This would allow sources the option to duct some or all process fugitive emi ssions to an existing furnace control device if it has excess capacity.

However, recognizing that there may be other control measures that could achieve equivalent emissions reductions that we have not yet identified, and to provide some flexibility for facilities to determine the best approach to reduce their emissions, we are also proposing an equivalent alternative compliance approach. Facilities can design an equivalent alternative approach (e.g., local capture, controls
, work practices) to achieve eq uivalent emissions reductions. Compliance would be demonstrated using fenceline monitoring to show that the ambient concentration of manganese at the facility boun dary is
less than 0.1 μg/m 3 on a 60

- day rolling average

.10/ 2 7 / 2011 14 We propose to set the fenceline concentration level to reflect the equivalent level of emissions control
that we estimate will be achieved with the requirement to enclose the furnace building(s) and evacuate the emissions to a control device(s). According to the risk assessment , the maximum modeled chronic
noncancer inhalation target

- organ

- specific hazard index ( TOSHI ) value is 2 after full enclosure and
evacuation of emissions based on the post

- control modeling analysis. This means that the modeled

concen tration at the maximum impact location after these controls are in place would be 0.1 μg/m 3

, which is 2 times higher than the current value of the reference concentration ( RfC ) for manganese. Therefore, achieving and maintaining a manganese level of 0.1 μg/m 3 at the facility boundary is proposed as the equivalent alternative standard to minimize fugitive emissions of HAP metals

..

We are also proposing a change in the building opacity limit as an indication of performance of the capture system operation. This change is described in a separate memorandum, Draft Selection of Opacity Limits for the Ferroalloys Production Source Category , available in the docket for the Ferroalloys Production source category

.

3.2.2

. Outdoor Fugitive Dust Emissions
As described in section 3.2.2 above, w e are unable to quantify HAP emissions from outdoor fugitive dust sources and did not identify any additional procedures or controls that could be expected to have a significant impact on these emissions

. Existing require ments that that plants operate according to an outdoor fugitive dust control plan are still in effect.

4.0 CONCLUSIONS This review identified several developments in practices, processes, or control technologies that have been implemented in this source category since promulgation of the current NESHAP. O ur analysis
indicates that both facilities have significantly reduced stack emissions of metal HAP compared to allowable levels, primarily through improved performance of baghouses.

Based on our review, we conclude that it is feasible and cost

- effective for facilities to achieve a n existing source furnace stack PM emissions limit of 24 mg/dscm and new source furnace stack emissions limit of 9.3 mg/dscm. We also conclude that a stack PM emission limit of 13 mg/dscm for10/ 2 7 / 2011 15 new and existing crushing and screening equipment is reasonable

. Our analyses indicate that a s tack
emission limit for PM of 3.9 mg/dscm is achievable for new and existing metal oxygen refining operations.

We conclude that a mercury emission limit from EAF of 16 μg/dscm is feasible for new and existing sources, requiring some sources to implement activated carbon injection

. We also conclude that a PAH
emission limit from EAF of 89 μg/dscm is feasible for new and existing sources, taking into account co

control from controls which may be implemented for mercury. We conclude that it is feasible for all
facilities to enclose the furnace building(s) and evacuate the emissions to a control device(s) to limit
f ugitive emissions , with PM emission limits equal to those for furnace s

. As described above, we also recommend that the proposed rule should include an equivalent alternative fenceline concentration limit.

We believe that these controls and measures are cost

- effective measures that reflect achievable performance for this industry. Details of the costs and emissions reductions associated with these
measures are available in Cost Impacts for the Ferroalloys Source Category , available in the docket for
the F erroalloys Production source category

.