So 2 modeling issues
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SO 2 Modeling Issues. Leigh Barb Bacon Meteorological Section ADEM Air Division June 2012. June 22, 2010- EPA finalizes new 1 hour SO 2 NAAQS at 75 ppb (195 µg/m 3 ) October 3, 2011- EPA issues Guidance for 1 hour SO 2 NAAQS SIP

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SO 2 Modeling Issues

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So 2 modeling issues

SO2 Modeling Issues

Leigh Barb Bacon

Meteorological Section

ADEM Air Division

June 2012


So 2 modeling issues

  • June 22, 2010- EPA finalizes new 1 hour SO2 NAAQS at 75 ppb (195 µg/m3)

  • October 3, 2011- EPA issues Guidance for 1 hour SO2 NAAQS SIP

  • Submissions for 30 day comment period. EPA-HQ-OAR-2010-1059

  • October 28, 2011- EPA extends comment period to December 2nd.

  • December, January, February, March, April……

  • April 12, 2012- EPA holds call with NAACA to announce plans for 1 hour

  • SO2 Implementation- no modeling for unclassifiable areas.

  • May 29 – June 1, 2012- EPA holds a series of stakeholder meetings to

  • discuss implementation issues.


The good the bad and the so so news

The Good, the Bad and the So- So News

Good News

EPA is advocating, through a white paper and stakeholder discussions,

a more pronounced role for monitoring, with modeling still a viable

option.

  • Comments will be taken on the White Paper through June 22nd

    Bad News

    Complex modeling is not off the table.

    So-So News

    There are still many specifics that need to be ironed out.

    Rulemaking would need to be completed, detailing how the network

    will be developed- TIME!

    Cost to Agencies, Sources?


So 2 modeling

SO2 Modeling

  • In an effort to evaluate the impact of the new 1 hr NAAQS, ADEM developed a case study involving a set of modeling analyses.

  • This analysis was completed following current guidance used in the PSD program.

    • EPA has indicated that the implementation process will not necessarily follow PSD methodology

  • The goal of the study was to ascertain the extent of potential problems with the NAAQS, if attainment status is determined through modeling.


  • The specifics

    The Specifics

    • ADEM chose a small SO2 emitter (~120 tpy- allowed) as the focus of the case study. Facility “A” is located in a fairly rural part of the state, with the closest facility located approx. 1.5 km away.

      • However, within 15 km of the source, there is a complex of sources of varying types (chemical, pulp and paper, utility, etc.).

      • There are three units at the facility, all of which operate primarily on natural gas, with fuel oil backup.

      • It is the fuel oil capability that “triggers” the tpy threshold that would require modeling.


    Model inputs

    Model Inputs

    • ADEM initiated a QA/QC of SO2 sources in late 2011, including updating UTM locations and stack parameters, so confidence in the data was high.

    • This was a pseudo-PSD analysis, so the first step was to model the facility alone and determine how significant the facility was and then how far out the significance extended.

      • EPA’s interim SO2 significance level of 7.8 µg/m3 was used.

    • A fairly tight grid was used, with 250 meter spacing out 15 km in each direction.

    • Modeling was performed with EPA’s approved dispersion model, AERMOD, using 2006-2010 meteorological data for the area, and building downwash for the facility.

    • ADEM did not evaluate plant property boundaries in this analysis, which obviously will play a crucial role in compliance.


    So 2 modeling issues

    Step 1: Model Facility A Only


    So 2 modeling issues

    Facility “A’s” Impact Area- 2010

    BLUE AREAS ARE

    INSIGNIFICANT CONCENTRATIONS

    RED AREAS ARE PREDICTED VIOLATIONS


    Facility a conclusions

    Facility A Conclusions

    • As expected, there are localized predicted violations around the facility.

    • Some of these predicted violations are likely on plant property, and further analysis will exclude these concentrations.

    • However, there are widespread “predicted” significant contributions to potential violations of the 1 hour standard within the 15 kilometer grid (yellow on map)

    • In order for this facility to receive a permit, if it was a new source, it would have to demonstrate that it does not contribute to a predicted violation at each of those receptors. This is typically handled through a cumulative modeling analysis.


    Step 1a model facility a and its closest neighbor facility b

    Step 1a: Model Facility A and its Closest Neighbor (Facility B)


    Modeling results facilities a b 2010

    Modeling Results Facilities A&B - 2010

    RED AREAS ARE PREDICTED VIOLATIONS


    Facilities a b conclusions

    Facilities A&B Conclusions

    • There are widespread “predicted” violations of the 1 hour standard within the 15 kilometer grid centered on Facility A.

    • From the previous map, it can be seen that at a good number of those violations, Facility A is either causing or contributing to the predicted violations. In addition, the same can be said for Facility B.

    • However, more modeling will need to be completed to determine plant property issues, and modeling Facility B correctly, i.e. downwash, etc.

    • In addition, it is apparent from the maps that Facility A will have a significant impact beyond the edges of the grid.

      • Additional modeling will need to be accomplished to see how far downwind these causations/contributions will extend

      • Who will be responsible for that modeling?

      • Where does this stop?


    Step 2 model all sources within sia

    Step 2: Model all sources within “SIA”

    • This step included adding 23 additional stacks, representing 6

    • facilities, to the modeling.


    So 2 modeling issues

    Cumulative Modeling Results A&B - 2010

    ~30 KM

    SOURCE UNDER REVIEW


    Cumulative analysis conclusions

    Cumulative Analysis Conclusions

    • Similar to previous slides, there are widespread “predicted” violations of the 1 hour standard within the 15 kilometer grid centered on Facility A.

    • The extent of these violations has increased significantly, mainly to the south and west of Facility A. Again, using the previous maps, it can be seen that in a good number of those violations, Facility A is contributing to the predicted violations.

    • However, more modeling will need to be completed to determine plant property issues, and re- modeling MANY facilities to incorporate downwash, etc.

      • This will be an extensive time and resource burden on both sources and the State.


    Cumulative analysis conclusions cont

    Cumulative Analysis Conclusions, cont.

    • In addition, it is apparent from the maps that many of these sources will have impacts beyond the edges of the grid.

      • Additional modeling will need to be accomplished to see how far downwind these causations/contributions will extend.

      • Who will be responsible for that modeling? Who will pay for it?

      • What is the timing for resolution?

      • Will sources need to work together in situations where there is no obvious fix? What is ADEM’s role in this?

      • Where do these analyses end?


    Cumulative analysis conclusions cont1

    Cumulative Analysis Conclusions, cont.

    • In the areas of highest concentrations, there are many receptors where 6-7 facilities significantly contribute to modeled violations.

    • Who has to reduce emissions to correct the issue?


    Never ending story

    Never-Ending Story?

    A

    B

    C

    E

    D

    SIGNIFICANT IMPACT AREAS


    What can be done

    What Can Be Done?

    • Know your facility- have up to date property boundaries, a reliable, scaled plot plan, and good stack information.

    • Comment! EPA is accepting comments on the White Paper they have developed through June 22nd.

      http://www.epa.gov/air/sulfurdioxide/implement.html

    • ADEM intends to comment on several parts of the White Paper, including:

      • Putting an emphasis on developing monitoring networks, using an actual tpy emissions threshold, as outlined in the paper. (ex. ~2000 tpy)

      • Providing a phased in approach that looks to the larger SO2 sources first, then focuses resources on smaller sources at a later date.


    What can be done1

    What Can Be Done?

    • ADEM intends to comment on several part of the White Paper, including:

      • Allowing sources to choose to operate a network of monitors or to model, depending on each source’s particular situation.

      • For a modeling analysis, allowing the use of actual emissions to determine if there are likely real world issues.

      • Allowing a sole source analysis as opposed to a cumulative assessment, so that sources can focus on their contributions.

      • Allowing time for national programs to have a chance to work, before expecting “fixes”.


    And above all give states

    And Above All Give States…

    • TIME-Give ADEM the time to implement the program. It is understood that there are those that want the fix tomorrow, but it simply isn’t possible. Allow us to make the important decisions within a reasonable time frame.

    • FLEXIBILITY- Give ADEM the flexibility to implement the standard in the best way for Alabama. We know our sources and state programs are not the same. We need to know that EPA will provide the tools and allow us to use those tools to support ADEM’s decision making.

    • RULES-Codify the decisions made through rulemaking. The use of guidance and policy memos simply will not work with an implementation program of this scale.


    Questions

    Questions?


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