BART Discussion. Regional/State/Local Modelers Workshop May 17, 2006 San Diego, CA

Transcription

1 BART Discussion Regional/State/Local Modelers Workshop May 17, 2006 San Diego, CA EPA Office of Air Quality Planning and Standards Contacts: Todd Hawes Kathy Kaufman

2 Disclaimer The following presentation represents the current views and ideas of the EPA management agencies staff and does not necessarily represent the official position of EPA. Editorial comments are those of the presenter and do not necessarily reflect the views or opinions of anyone else. 2

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5 Summary of the BART Process 1. ID BART eligible sources 2. ID which of those are subject to BART Reasonably anticipated to cause or contribute to any visibility impairment in Class I areas (e.g. CALPUFF modeling) 3. Determine the BART controls, if any Note that BART Guidelines are just guidance Only binding on >750 MW EGUs (> 200 MW at 750 MW plants); provide lots of flexibility 5

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7 Individual Source Modeling BART <CALPUFF> <CALPUFF> B-E sources y y y Cause or Contribute Subject to BART 5 factors - (controls) BART= Control Exempt BART=no Control 7

8 Reasonable Progress RPG is the foundation of the RH program The Goal is a return to natural visibility background conditions by 2064 Progress means: Improvement in visibility for the most impaired (i.e., 20% worst) days. No degradation in visibility for the least impaired (i.e., 20% best) days BART is part of RP 8

9 Rate To Achieve Natural Conditions in 60 Years (under 308) Example Baseline 30 (Visibility impairment in Deciviews) x x Required Analysis for 1st Implementation Period Natural 12 Ultimate CAA goal Long Term Strategy for Reasonable Progress BART is and independent part of Reasonable Progress Year 9

10 1. Identifying BART-Eligible Sources BART-Eligible if: Any emission units in one of the 26 PSD categories (e.g. EGUs, industrial boilers, kraft pulp mills, refineries, portland cement plants,etc) Any units in existence on 8/7/77 and began operation after 8/7/62 Is the PTE of any visibility impairing pollutant, summed across all units, > 250 TPY? 10

11 CLASS I AREAS WITH BART ELIGIBLE UNITS 250 TONS/YR AND ABOVE Class I areas buffer_zones_50km out from surrounding area buffer_zones_100km out from surrounding area buffer_zones_300km out from surrounding area BART Source Units: SO2 NonEGU BART Units with SO2 > 250 tons/yr. NOx NonEGU BART Units with NOx >250 tons/yr. EGU BART Units with SO2 or NOx >250 tons/yr 96 facilities (245 units) -4.5 million TPY SO million TPY Nox CAIR - 78 facilities (199units) -4.0 million TPY SO million TPY Nox EGU BART UNITS >250 tons/yr. April 20, 2005 OAQPS final version 11

12 12 BART Source Units: buffer_zones_300km out from buffer_zones_100km out from buffer_zones_50km out from Class I EGU BART Units with SO2 or NOx >250 tons/yr NOx NonEGU BART Units with NOx >250 tons/yr. SO2 NonEGU BART Units with SO2 > 250 tons/yr. surrounding area surrounding area surrounding area areas nonegu (SO2&NOx) BART UNITS >250 tons/yr. April 20, 2005 OAQPS final version CLASS I AREAS WITH BART ELIGIBLE UNITS 250 TONS/YR AND ABOVE SO2 158 units, 450K TPY NOx 557 units, 422 K TPY

13 13 BART Source Units: buffer_zones_300km out from buffer_zones_100km out from buffer_zones_50km out from Class I EGU BART Units with SO2 or NOx >250 tons/yr NOx NonEGU BART Units with NOx >250 tons/yr. SO2 NonEGU BART Units with SO2 > 250 tons/yr. surrounding area surrounding area surrounding area areas EGU & nonegu (SO2&NOx) BART UNITS >250 tons/yr. April 20, 2005 OAQPS final version CLASS I AREAS WITH BART ELIGIBLE UNITS 250 TONS/YR AND ABOVE

14 2. Subject to BART Which BART Eligible Sources Are Subject to a BART control evaluation? Does the B-E Source Cause or Contribute to visibility impairment in a Class I area (i.e. is Subject to BART)? Three Options for the Subject to BART test: State assumes that all BART-eligible sources will cause or contribute to visibility impairment at any Class I area. State demonstrates all BART-eligible sources will not cause or contribute to visibility impairment at any Class I area. Exempt individual sources <CALPUFF> 14

15 2. Subject to BART (cont.) BART Exemption - Which Sources Cause or Contribute to Impairment? Set a contribution threshold (0.5 dv or lower) Run CALPUFF for all BART-eligible units at the Source Compare results to the threshold Max. 24 hr impacts compared to natural background; 98 th percentile value is used If the source impact threshold (e.g. 0.5 dv) then it is Subject to BART Otherwise, (e.g 0.5) source is exempt from BART May also use the Model Plant exemption 15

16 2) Subject to BART (cont.) Low Hurdle for BART-Eligible Sources Exemption step is conservative Just because a source is Subject to BART does not mean controls are required 16

17 3. Determine the Controls, if any (Subject to BART) If the Source Causes or Contributes to Visibility Impairment then Conduct an engineering review to determine a control technology to set an emission limit (BART) For each source, State must consider 5 factors: Controls already in place at the source Cost of compliance Remaining useful life Energy and nonair environmental impacts Visibility Test the fifth factor degree of visibility improvement as a result of control <CALPUFF> 17

18 3. Determine the Controls, if any (cont.) Fifth Factor (Visibility modeling) Run CALPUFF at pre-control and post-control emission rates for SO2, NOx, and PM2.5 (i.e. degree of improvement) No prescriptive limits for this step such as a comparison threshold Results can be weighted in a variety of ways Consider magnitude, frequency, and duration of impacts. Examples Worst case days, percentage change Season, threshold Compare the 98 th percentile value for pre- and post-control Combinations 18

19 3) Determine the Controls, if any Establishing the BART Limit State weighs the five factors and determines an emission limit (i.e. BART) based on control Repeat process on each affected unit Pollutant by pollutant basis For each control technology option under review BART may equal No Control based on the five factor analysis Example there are existing controls on the unit and it would be cost prohibitive to control further Example no significant visibility improvement is shown 19

20 Modeling Protocol Required in all cases Describes how States, RPOs, or Sources will run the model Approvable by the State We recommend IWAQM as a starting point Flexibility FLMs should be involved 20

21 Guideline is binding for 750 MW power plants For EGU plants >750 megawatt (MW), CAA requires BART determinations to be made pursuant to EPA guidelines. Guidelines procedures mandatory for these sources Guidelines contain presumptive control levels for units 200 MW and above For EGU units >200 MW (not at 750 MW plants): encourage use of presumptive controls Because of evidence that such controls are cost effective All other source categories: guidelines are guidance only 21

22 BART Presumptive Limits for EGUs For coal-fired EGUs greater than 200 MW located at power plants greater than 750 MW SO2: 95% removal or an emission rate of 0.15 lb/mmbtu. NOx: lbs/mmbtu depending on boiler size and coal type, In NOx SIP call area extend controls to year round Outside SIP call area current combustion controls Also based upon whether selective catalytic reduction (SCR) or selective noncatalytic reduction (SNCR) are already employed at the source. State can set BART higher or lower if justified in the five factor analysis (unlikely in all but a few cases) 22

23 Effect of the CAIR on BART Affects only EGUs that participate in CAIR (in the East) Covers an EGU s BART obligation for NOx and SO2. CAIR = BART EGUs must still undergo a BART analysis for PM 23

24 Q & A s Is the 0.5 dv threshold mandatory for the exemption modeling? No, you can use a lower one How do you do the exemption modeling for EGUs (since SO 2 and NOX are covered by CAIR eastern US)? You may model PM only (legal settlement) May consider a lower threshold In the West, you may model SO 2, NOx, and PM collectively since there is no CAIR 24

25 Q & A s cont. How do you model VOCs, Ammonia, VOCs,H 2 SO 4? VOCs case by case (consider species) many States showing VOCs having no impact NH 3 use your best judgment (250 TPY cutoff) H 2 SO 4 model as direct PM Can I use the Ammonia Limiting Method Yes, default values are provided or annual or monthly averages can be developed 25

26 Q & A s cont. What Regulatory Defaults Should I use? IWAQM, Appendix W, FLAG, EPA Guidance for Estimating Natural Conditions Under the RH Program Should use Method 6 with monthly f(rh) What value can I use for Natural Background? Use 20% best days or annual (legal settlement) Which IMPROVE equation should I use? old 26

27 Q & A s cont. What is the best way to determine 24-hr max. actual emission rates? CEM, permit limits, AP-42, PTE Do not consider start-up, shutdown, or malfunction If SO 2, NOx, and PM max. emission rates occur on different days, use the highest rate from each day (conservative) How do I determine if my boiler is integral to the process and therefore BART-eligible? Decision has not been determined; State discretion May want to consider large boilers which were designed to serve the process 27

28 Q & A s cont. What dispersion coefficients should I use, (e.g. PG or turbulence dispersion coefficients)? PG, unless an adequate demonstration is made (per Appendix W) Do I need Obs. To process my met. data? 36 km MM5 too coarse 12 km MM5 data to 12 km CALMET NOOBS ok, but use max. CALPUFF result 12 km MM5 to finer CALMET (e.g. 4 km) Use OBS Decisions reached between Region 4 and VISTAS 28

29 Q & A s cont. How can I use the model plants for exemption from BART? If combined Potential emissions of SO 2, NOx, and PM is < 500 TPY and the source is >50 km from the Class I area If combined Potential emissions of SO 2, NOx, and PM is < 1000 TPY and the source is >100 km from the Class I area Addition of PM is a revision/correction to the Q&A document 29

30 Q & A s cont. Does the use of the model plant numbers mean that I can use Q/D < 10 in all cases of the BART exemption step? Generally no, unless an adequate demonstration is made Fine to use it as a tool What if my source is <50 km from a Class I area? May use CALPUFF or consider other methods (e.g. PLUVUE II) 30

31 Q & A s cont. Can I determine exemptions with the Line of Sight methodology? No, not for uniform haze applications and a range of possible views Can I use a grid model, like CAMx Yes, in cases where you are determining that your BART-eligible sources collectively are exempt. No adjustments or scaling should be applied to the concentrations 31