MEMORANDUM. Ken Rairigh. To: Till Stoeckenius. From: Date: 4/7/2005. Subject: WY NO 2 PSD modeling: Final modeling results for Task 1

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1 MEMORANDUM To: From: Ken Rairigh Till Stoeckenius Date: /7/ Subject: WY NO PSD modeling: Final modeling results for Task This memo documents preliminary NO PSD increment modeling results for the Domain (D) near-field region centered on the Bridger-Fitzpatrick Class I Wilderness Area (see Figure ). Annual average NO concentrations were predicted using both ISC and CalPuff. Both the shortterm (ST) and long-term (LT) versions of ISC were used. Emissions Emissions processing for sources in Sublette County was described in a previous memorandum. Aside from two WY power plant sources (as described below), emission sources used in this round of modeling were all located within Sublette County. Development of the modeling inventory was designed to provide a reasonable set of Sublette County emissions within the limited timeframe available for these tasks by keeping the emissions structure as closely aligned as possible with that used for the 99 SWWYTAF project modeling. Sublette County NO x sources were grouped by type as specified by WY DEQ. Source groups and corresponding annual total emissions are shown in Table. Area source emission totals in this table represent totals of gridded emissions as they were input to the models. All NO x emissions data provided for use in this study were assumed to be total NO x reported as NO as is customary. For all modeling scenarios except CalPuff run with the RIVAD chemistry option, NO x emission rates were input directly into the models and predicted concentrations are labeled as NO x in the model outputs and in this report. For the CalPuff runs in which the RIVAD chemical mechanism was used, NO x emissions were speciated into NO and NO assuming a NO/NO molar ratio of 9: for all source categories. Both predicted NO x and NO are reported for these runs. Stoeckenius, T.,. WY NO PSD modeling: Processing of emissions for for Sublette County. Memo to K. Rairigh, WY DEQ, 6 March. Earth Tech,. The Southwest Wyoming Regional CALPUFF Air Quality Modeling Study, Final Report. Earth Tech, Inc., Concord, NH, February. In some cases these total gridded values differ slightly from county totals reported elsewhere due to details of the gridding procedure. Golden Gate Plaza $ Rowland Way $ Novato, California 99- USA Tel: () $ Fax: () H:\WYDEQ PSD\AQ_Modeling\Reports\Taskmemo_a.doc

2 Receptors Page Three sets of receptor networks were superimposed for use in all model runs:. Gridded receptor matrix covering D at km resolution.. Receptors in the interior of the Bridger-Fitzpatrick Class I area at locations specified by the National Park Service ( Receptors at km spacing along the boundary of the Bridger-Fitzpatrick Class I area as used in previous PSD increment modeling studies (Solvay/Simplot) and supplied for this project by WY DEQ. Receptor elevations for the last two networks were as specified by the NPS and WY DEQ, respectively. Elevations for the first network were determined from º DEM data via the interpolation method as implemented by the ISC Breeze software package. ISC Modeling Both the short-term (ISCST) and long-term (ISCLT) models were run in regulatory default mode with the reported NO x emissions as described above. Source parameters were identical to those used in CalPuff: point source stack parameters were supplied by WY DEQ, all area sources were assigned a release height of m and an initial sigma-z of m which is equal to one-half of the typical morning mixing height (Earth Tech, 999). Predicted maximum annual average NO x concentrations by source group are summarized in Table. Note that the maximum is listed for each source group and all source groups combined regardless of location so the indicated maximum value for all source groups combined (column ALL) does not necessarily equal the sum of the individual maximum source contributions as the maxima generally occur in different locations for different source groups. Annual maxima predicted by ISCST are larger than those predicted by ISCLT by about 6 7% in the Class I area and % in the Class II area (all source groups combined). This difference is most likely due to the lack of a complex terrain treatment and the use of horizontal sector averaging in ISCLT. As expected, the Sublette County oil and gas field sources are responsible for the largest maximum value of any source group at Class II area receptors and the maximum from the Jonah- Pindedale fields is nearly as large as that from all fields combined. Point sources also produce some relatively large impacts. Higher point (and area) source impacts may occur at Class II area locations close to some of the point (and area) sources in western Sublette County but the current receptor network does not cover that area (see Figure ). Additional receptors in western Sublette County will be added as part of the Task modeling effort. Within the Class I area, point sources produce larger maxima than the oil & gas sources, but even the maximum combined impact of all sources is estimated to be no more than.6 µg/m ; well below the NO Earth Tech, Air Emissions Within the Southwest Wyoming Regional Modeling Domain Volume : CALPUFF Modeling Inventory. Earth Tech, Inc., Concord, MA and Air Sciences, Denver, CO, November. Golden Gate Plaza $ Rowland Way $ Novato, California 99- USA Tel: () $ Fax: () H:\WYDEQ PSD\AQ_Modeling\Reports\Taskmemo_a.doc

3 Page Class I increment of. µg/m. Similarly, the maximum impacts at Class II receptors are well below the NO increment for Class II areas of µg/m. Spatial distributions of annual average NO x concentrations predicted by ISCST are shown in Figure (for all sources) and Figure (for the Jonah-Pinedale oil & gas sources). The spatial concentration patterns are very similar from year to year although the peak concentration magnitudes vary slightly (by ± 6 % for the all sources combined results). The peak impact area is associated with the concentration of oil & gas sources at the southeastern end of the Jonah- Pinedale anticline. Concentration gradients run southeast to northwest roughly parallel to the Bridger-Fitzpatrick Class I area boundary there is no significant intrusion of >. µg/m concentration isopleths into the Class I area. ISCST and ISCLT results for are compared in Figure. Both models produce very similar spatial patterns. CalPuff Modeling CalPuff was run using meteorological fields generated by applying the latest version of CalMet to the 99 SWWYTAF modeling database (Earth Tech, ). CalPuff was run in four different configurations:. Inert ( no chemistry ) assuming no deposition.. Inert but with dry NO x deposition turned on.. With the MESOPUFF II chemical mechanism to model NO x to nitrate conversion.. With the RIVAD/ARM chemical mechanism to model NO to NO and NO x to nitrate conversion. Scenarios, and were run with dry deposition turned on. Source inputs and receptor configurations for the CalPuff runs were identical to those used in ISC. Maximum annual average NO x concentrations (along with NO from the RIVAD chemistry run) predicted at the Class I and Class II receptors are summarized in Table. Note that the maximum is listed for each source group and all source groups combined regardless of location so the indicated maximum value for all source groups combined (column ALL) does not necessarily equal the sum of the individual maximum source contributions as the maxima generally occur in different locations for different source groups. Maximum annual average NO x concentrations within the Class II area predicted by CalPuff under the no chemistry and no deposition run are to 7 % greater with those predicted by ISCLT and to 8 % greater than those predicted by ISCST. Percentage differences are larger at the Class I receptors where peak concentrations are much lower. The relative impacts of each source group are roughly similar to those seen in the ISC results. Annual average NO x concentration impacts predicted by CalPuff for all sources and the Jonah-Pinedale oil & gas sources under the no chemistry and no chemistry with dry deposition runs are shown in Figure. Concentration patterns in all cases are similar to those obtained from the ISC results. Introducing dry deposition into the model results in a modest % decrease in the peak Class II all sources impact. Golden Gate Plaza $ Rowland Way $ Novato, California 99- USA Tel: () $ Fax: () H:\WYDEQ PSD\AQ_Modeling\Reports\Taskmemo_a.doc

4 Page Use of the MESOPUFF II chemical mechanism in CalPuff lowers the predicted Class II peak NO x concentration by % relative to the dry deposition only run. Use of the RIVAD chemical mechanism results in NO x predictions that fall in between those from the dry deposition only run and the MESOPUFF II run. Class II area peak NO concentrations for all sources combined predicted with the RIVAD mechanism are % lower than the corresponding NO x prediction using MESOPUFF II but Class I area predicted peak NO concentrations are slightly larger than corresponding predicted by NO x using MESOPUFF II. At the location of maximum Class II area impact from the Jonah-Pinedale fields, the RIVAD predicted NO /NO x ratio is.7. At the location of the maximum Class I area impact, the NO /NO x ratio is.9. These ratios are consistent with our expectations regarding near source (i.e., Class II) and more distant (Class I) NO /NO x ratios. Annual average NO x concentrations predicted using the MESOPUFF II chemistry and NO concentrations predicted using the RIVAD mechanism are shown in Figure 6. The overall concentration patterns are the same as in the no-chemistry results. Annual average NO x concentrations presented above do not include impacts from two large power plants (Bridger and Naughton) located in southwestern Wyoming but outside of Sublette County. A no-chemistry run was performed with CalPuff for these two sources; results are presented in Table. The maximum impact of the Bridger plant on the Class I area, while small, is on par with the maximum impact from all Sublette County sources, the maximum impact from Naughton is about half as much. As shown in Figure 7, the Bridger plant peak impact on the Class I area is at the southeast end of the wilderness area. A more detailed view of the concentration gradient in and near the Class I area (Figure 8) shows that, even with the Bridger and Naughton plant impacts included, the peak NO x impact within the Class I area is at the point on the border of the area that is closest to the Jonah-Pinedale field and not near the area of peak impact from the Bridger plant. The northwest southeast orientation of the concentration gradient shown in Figure 8 runs roughly parallel to the contour of the terrain. We hypothesize that this results from high concentration events (which contribute most heavily to the annual average) occurring under stagnant, light wind conditions possibly in conjunction with low-level or ground-based temperature inversions that keep low lying source emissions from reaching into the higher elevations. Source contributions to the Class I area annual average concentrations at locations of peak impacts from all sources, Sublette County sources only, Jonah-Pinedale oil & gas sources, and the Bridger power plant are shown in Figure 9. These results confirm the separation between the Bridger power plant impacts and impacts from Sublette County sources. These results also show that, while none of the concentrations are large relative to the Class I area NO increment of. µg/m, source contributions from the Jonah-Pinedale oil & gas fields (based on the inventory used for the present analysis) are a small fraction of the total impact from all Sublette County sources. Golden Gate Plaza $ Rowland Way $ Novato, California 99- USA Tel: () $ Fax: () H:\WYDEQ PSD\AQ_Modeling\Reports\Taskmemo_a.doc

5 Page Table. Model input NO x emissions by source group. Source Group Emissions (TPY). Point sources: Sublette County sources with potential to emit > TPY,9. Area sources. Agricultural equipment 6. Recreational marine and recreational vehicles 8. Other (urban area sources in cities of Pinedale, Marbleton, and 8 Big Piney). Oil & Gas field sources (heaters and flaring). Jonah field and Pinedale field 69. All other fields in Sublette County 9. On-Road mobile Golden Gate Plaza $ Rowland Way $ Novato, California 99- USA Tel: () $ Fax: () H:\WYDEQ PSD\AQ_Modeling\Reports\Taskmemo_a.doc

6 Table. Maximum NO x impacts predicted by a) ISCLT and b) ISCST. Source groups are: Jonah-Pinedale fields(gasjp), all gas&oil fields (GAS), point sources (PTS), on-road (MOBILE), recreational marine and recreational equipment (RECMAR), urban area sources (CITY), agricultural equipment (AG); Other Area = RECMAR+CITY+AG. a) ISCLT Max NOx ug/m ALL GASJP GAS PTS MOBILE RECMAR CITY AG Other Area 999 Class I Class II Page 6 Class I Class II Class I Class II Class I Class II Class I Class II b) ISCST Max NOx ug/m ALL GASJP GAS PTS MOBILE RECMAR CITY AG Other Area 999 Class I Class II Class I Class II Class I Class II Class I Class II Class I Class II Golden Gate Plaza $ Rowland Way $ Novato, California 99- USA Tel: () $ Fax: () H:\WYDEQ PSD\AQ_Modeling\Reports\Taskmemo_a.doc

7 Page 7 Table. Summary of maximum annual average NO concentrations by source group predicted by the CalPuff model for a) no chemistry run, b) no chemistry but with dry deposition, c) MESOPUFF II chemical mechanism, d) RIVAD chemical mechanism NO x predictions, e) RIVAD chemical mechanism NO predictions. Source groups are as in Table. a) No Chemistry CALPUFF NO x ALL GAS PTS MOBILE Other GASJP Area Class I Class II b) Dry Deposition CALPUFF NO x Dry Deposition ALL GASJP GAS PTS MOBILE Other Area Class I Class II c) MESOPUFF II Chemistry CALPUFF NO x MESOPUFF II, Dry Deposition ALL GASJP GAS PTS MOBILE Other Area Class I Class II d) RIVAD Chemistry (NO x ) CALPUFF NO x RIVAD, Dry Deposition ALL GASJP GAS PTS MOBILE Other Area Class I Class II e) RIVAD Chemistry (NO ) CALPUFF NO RIVAD, Dry Deposition ALL GASJP GAS PTS MOBILE Other Area Class I Class II Golden Gate Plaza $ Rowland Way $ Novato, California 99- USA Tel: () $ Fax: () H:\WYDEQ PSD\AQ_Modeling\Reports\Taskmemo_a.doc

8 Page 8 Table. Maximum annual average NO impacts at the Domain Class I and Class II receptors predicted under the no-chemistry scenario by CalPuff from all Sublette County sources and two power plants (PP) in southwestern Wyoming. CALPUFF NO x Sublette Co. Sources Bridger PP Naughton PP ALL Class I..7.. Class II Golden Gate Plaza $ Rowland Way $ Novato, California 99- USA Tel: () $ Fax: () H:\WYDEQ PSD\AQ_Modeling\Reports\Taskmemo_a.doc

9 Page 9 D SW Corner: -., -6. NX,NY: x Dx SW Corner: - 67., -. NX,NY: x Figure. Near-field domain (D) modeling receptor domain (indicated by grid of + symbols) in southwestern WY with receptors at km grid resolution (+), receptors along the border of and inside the Bridger-Fitzpatrick Wilderness (O), and Sublette County point sources ( ). Box enclosing Dx domain indicates extent of km model computational grid used for tracking puffs. Golden Gate Plaza $ Rowland Way $ Novato, California 99- USA Tel: () $ Fax: () H:\WYDEQ PSD\AQ_Modeling\Reports\Taskmemo_a.doc

10 Page ISCST 999 Annual Average NOx [ug/m^] Max =. ug/m^ ISCST Annual Average NOx [ug/m^] Max =.7 ug/m^ ISCST Annual Average NOx [ug/m^] Max =.9 ug/m^ ISCST Annual Average NOx [ug/m^] Max =.6 ug/m^ ISCST Annual Average NOx [ug/m^] Max =. ug/m^ Figure. Annual average NO x predictions from ISCST for all sources. Golden Gate Plaza $ Rowland Way $ Novato, California 99- USA Tel: () $ Fax: () H:\WYDEQ PSD\AQ_Modeling\Reports\Taskmemo_a.doc

11 Page ISCST 999 Annual Average NOx [ug/m^] from Jonah and Pinedale Gas Max =. ug/m^ ISCST Annual Average NOx [ug/m^] from Jonah and Pinedale Gas Max =.8 ug/m^ ISCST Annual Average NOx [ug/m^] from Jonah and Pinedale Gas Max =.97 ug/m^ ISCST Annual Average NOx [ug/m^] from Jonah and Pinedale Gas Max =.8 ug/m^ ISCST Annual Average NOx [ug/m^] from Jonah and Pinedale Gas Max =.8 ug/m^ Figure. Annual Average NOx predicted by ISCST for Jonah and Pinedale Gas Sources. Golden Gate Plaza $ Rowland Way $ Novato, California 99- USA Tel: () $ Fax: () H:\WYDEQ PSD\AQ_Modeling\Reports\Taskmemo_a.doc

12 Page ISCLT Annual Average NOx [ug/m^] Max =.8 ug/m^ ISCLT Annual Average NOx [ug/m^] from Jonah and Pinedale Gas Max =.6 ug/m^ ISCST Annual Average NOx [ug/m^] Max =.9 ug/m^ ISCST Annual Average NOx [ug/m^] from Jonah and Pinedale Gas Max =.97 ug/m^ Figure. ISCLT (top row) and ISCST (bottom row) annual average NO x for all sources (left column) and Jonah-Pinedale (right column) for. Golden Gate Plaza $ Rowland Way $ Novato, California 99- USA Tel: () $ Fax: () H:\WYDEQ PSD\AQ_Modeling\Reports\Taskmemo_a.doc

13 Page Calpuff 99 Annual Average NOx No Chemistry Run (All Sources) Max = 6.9 ug/m^ Calpuff 99 Annual Average NOx No Chemistry Run (Only Jonah Pinedale Sources) Max =.7 ug/m^ Calpuff 99 Annual Average NOx No Chemistry Run with Deposition (All Sources) Max =.87 ug/m^ Calpuff 99 Annual Average NOx No Chemistry Run with Deposition (Only Jonah Pinedale Sources) Max =. ug/m^ Figure. Annual average NO x concentrations predicted by CalPuff for all Sublette County sources (left column) and Jonah-Pinedale oil & gas field sources only (right column). Top row: no chemistry. Bottom row: no chemistry but with dry deposition turned on. Golden Gate Plaza $ Rowland Way $ Novato, California 99- USA Tel: () $ Fax: () H:\WYDEQ PSD\AQ_Modeling\Reports\Taskmemo_a.doc

14 Page Calpuff 99 Annual Average NOx MESOPUFF II Chemistry (All Sources) Max =. ug/m^ Calpuff 99 Annual Average NOx MESOPUFF II Chemistry (Only Jonah Pinedale Sources) Max =.69 ug/m^ Calpuff 99 Annual Average NO RIVAD/ARM Chemistry (All Sources) Max =. ug/m^ Calpuff 99 Annual Average NO RIVAD/ARM Chemistry (Jonah Pinedale Sources) Max =.7 ug/m^ Figure 6. Annual average NO x predicted using MESOPUFF II chemistry (top row) and NO concentrations predicted using RIVAD chemistry (bottom row): impact of all Sublette county sources combined (left column), impact of Jonah-Pinedale oil & gas field sources only (right column). Golden Gate Plaza $ Rowland Way $ Novato, California 99- USA Tel: () $ Fax: () H:\WYDEQ PSD\AQ_Modeling\Reports\Taskmemo_a.doc

15 Page Calpuff 99 Annual Average NOx No Chemistry Run (All Sources. with SWWY Power Plant) Max = 6. ug/m^ Calpuff 99 Annual Average NOx No Chemistry Run Bridger Plant Only Max =. ug/m^ Calpuff 99 Annual Average NOx No Chemistry Run Naughton Plant Only Max =.69 ug/m^ Figure 7. Annual average NO x concentrations predicted by CalPuff for all sources (top left), Bridger power plant only (top right) and Naughton power plant only (bottom left). Note different color scale used to represent power plant impacts. Golden Gate Plaza $ Rowland Way $ Novato, California 99- USA Tel: () $ Fax: () H:\WYDEQ PSD\AQ_Modeling\Reports\Taskmemo_a.doc

16 Page Calpuff 99 Annual Average NOx No Chemistry Run (All Sources. with SWWY Power Plant) Max = 6. ug/m^ Figure 8. Annual average NO x concentrations from all sources in Sublette County and the Bridger and Naughton power plants with contour scale altered to show concentration gradient within and near the Bridger-Fitzpatrick Class I area. Golden Gate Plaza $ Rowland Way $ Novato, California 99- USA Tel: () $ Fax: () H:\WYDEQ PSD\AQ_Modeling\Reports\Taskmemo_a.doc

17 Page 7 Source Contributions at Locations of Maximum Class I Area Impacts.. Annual Avg. NOx (ug/m).... All Source Max All Sublett Max Jonah-Pinedale Max Bridger Max.. Points All O&G Jonah- Pinedale On-Road Mobile Other Area All Sublette Co. Bridger Naughton Location All Sources Sublette Co. Jonah- Pinedale Bridger All Src Max..7.. All Sublett Max....8 Jonah-Pinedale Max..7.. Bridger Max....7 Figure 9. Source contributions (µg/m ) to annual average NO x at locations of maximum impacts in the Bridger-Fitzpatrick Class I area from all sources combined, all sources in Sublette Co., Jonah Pinedale oil & gas sources, and the Bridger power plant. Golden Gate Plaza $ Rowland Way $ Novato, California 99- USA Tel: () $ Fax: () H:\WYDEQ PSD\AQ_Modeling\Reports\Taskmemo_a.doc