executive summary - colorado state universityvibe.cira.colostate.edu/ogec/docs/north...

PUBLIC COMMENT DRAFT

NC Division of Air Quality

Photochemical Modeling of

Shale Gas Development and Production

in North Carolina

An estimate of the potential ground-level ozone impacts fromthe development, production, processing and

transmission of natural gas from shale gas wellsin North Carolina

5/1/2015

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Table of Contents1. Executive Summary.............................................................................................................................4

2. Introduction.........................................................................................................................................6

3. Methodology.......................................................................................................................................8

3.1 Photochemical Modeling...................................................................................................................8

3.2 Emissions........................................................................................................................................10

4. Results...............................................................................................................................................12

5. Discussion and Conclusions...............................................................................................................16

6. References.........................................................................................................................................17

List of Tables

Table E-1. Modeling Results for Ozone Monitors in and Near the Shale Gas Study Area...........................5Table 3-1. CMAQ Configuration Options....................................................................................................9Table 3-2. Model Runs................................................................................................................................9Table 4-1. Modeling Results for Ozone Monitors in and Near the Shale Gas Study Area.........................14Table 5-1. Comparison of Modeled Ozone Impacts of the Sanford Shale Development to “Best Estimate” Emission Scenarios for the Marcellus and Fayetteville Shale Development..............................................17

List of Figures

Figure 2-1. Triassic Basins (green) within North Carolina...........................................................................6Figure 2-2. Map of the Monitor Locations and 2012-2014 Ozone Design Values, in parts per billion........7Figure 3-1. 36-km (left) and 12-km (right) SEMAP air quality modeling grids.............................................8Figure 3-2. Estimated 2018 NOx and VOC Emissions for Lee County and for the Drilling Activity in the Sanford Sub-basin......................................................................................................................................10Figure 3-3. Percentage of NOx and VOC Emissions for Lee County in 2018 and for the Drilling Activity in the Sanford Sub-basin...............................................................................................................................11Figure 3-4. The 12-km SEMAP Air Quality Modeling Grid, Centered on Lee County (the Sanford Sub-basin is shaded in blue).............................................................................................................................11Figure 3-5. Percent Allocation of the Shale Gas Development Emissions to the Modeling Grid...............12Figure 4-1. Average Change in Ozone for Days with 2018 Modeled Ozone Concentrations Greater than 60 ppb in the Triangle and Lee County Areas............................................................................................13Figure 4-2. Change in Predicted 2018 Design Values in the Triangle and Lee county areas.....................15Figure 4-3. Change in the Number of Days with Ozone Concentrations above 60, 65, and 70 ppb for the Fuquay-Varina, Pittsboro, Blackstone Monitors, and the model grid cell with peak shale drilling emissions (d)..............................................................................................................................................................16

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List of Acronyms

Acronym DefinitionCAA Clean Air ActCAMx Comprehensive Air quality Model with extensionsCMAQ Community Multiscale Air Quality modelDENR North Carolina Department of Natural ResourcesNAAQS National Ambient Air Quality StandardNOx Nitrogen OxidesPM2.5 Particulate Material with a diameter less than 2.5 micronsppb parts per billionSEMAP Southeastern Modeling, Analysis and PlanningEPA U.S. Environmental Protection AgencyVOC Volatile Organic CompoundsWRF Weather Research and Forecasting model

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1. Executive Summary

In 2011, the North Carolina General Assembly adopted Session Law 2012-143 establishing a regulatory program for the management of oil and gas exploration and development activities, parts of which were amended in Session Law 2015-1. Part III, Section 2.(c)(a3)(2)(ii) of Session Law 2012-143 directs the Department of Environment and Natural Resources (DENR) to assess emissions from oil and gas exploration and development activities that use horizontal drilling and hydraulic fracturing technologies, including emissions from associated truck traffic, to determine the impact on ozone levels in the area in order to determine measures needed to maintain compliance with federal ozone standards.

This report summarizes the results of the DENR’s assessment of potential air emissions impacts on ground-level ozone formation associated with possible oil and gas exploration and development activities in the Sanford Sub-basin shale formation located in Lee, Chatham and Moore counties. Photochemical grid modeling was performed using summer day nitrogen oxides (NOx) and volatile organic compound (VOC) emissions estimates during year 6 of shale gas exploration and development activities representing the highest level of emissions estimated to occur relative to current emissions levels.1 Three model runs were performed to assess the potential impacts associated with emissions from shale gas exploration and development activity: A base year 2007 run (Base07), a future year 2018 run (Future18), and a future year 2018 run containing year 6 shale development emissions (Sanford18). An additional sensitivity run was completed to assess potential ozone impacts associated with only the NOx emissions estimated for year 6 of the shale exploration and development activities (Sanford18_NOx).

Table E-1 shows the modeling results for monitors in and around the shale gas study area. The photochemical modeling results indicate that emissions associated with shale gas exploration and development may increase ozone concentrations in the study area by almost 2 parts per billion (ppb) at the Blackstone monitor located in Lee county, and less than 1 ppb at the other monitors in the region. Future ozone design values in 2018 are predicted to be 63.7 ppb or below. These modeling results suggest that the emissions increases associated with shale-gas development activities will not likely contribute to a violation of the current 2008 8-hour ozone standard of 75 ppb, as well as the US Environmental Protection Agency’s (EPA) proposed revision to the standard ranging from 65-70 ppb.2

1 See “Estimate of Air Emissions from Shale Gas Development and Production in North Carolina”, April 2015, for further details. Current emissions levels represent emissions from all source sectors prior to the start of shale gas exploration and development activities. 2 The CAA requires the EPA to review, and revise if necessary, the National Ambient Air Quality Standards (NAAQS) every five years. On December 17, 2014, the EPA proposed to revise both the primary ozone standard, to protect public health, and the secondary standard, to protect the public welfare (79 FR 75234-75411). Both standards would be 8-hour standards set within a range of 65 to 70 ppb. The EPA also requested public comment on levels for the health standard as low as 60 ppb as well as keeping the existing standard of 75 ppb. The EPA is under a court order to finalize its decision on the revised ozone NAAQS by October 1, 2015.

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Table E-1. Modeling Results for Ozone Monitors in and Near the Shale Gas Study Area

County Monitor

Base07 Ozone Design Value (ppb)1

Future18 Ozone Design Value (ppb)2

Sanford18 Ozone Design Value (ppb)3

Change from Future18 to Sanford18 (ppb)

Lee Blackstone 74 59.5 61.4 1.9

Chatham Pittsboro 71.7 55.4 56.3 0.9

Wake Fuquay-Varina 77 62.3 62.6 0.3

Montgomery Candor 73 58.8 59 0.2

Wake Millbrook 79 63.6 63.7 0.1

Durham Durham 74 59 59.1 0.1

Cumberland Wade 75.3 60.5 60.6 0.1

Granville Butner 79.3 63.5 63.6 0.1

Johnston West Johnston 75 59.7 59.8 0.1

Franklin Franklinton 76.3 61.2 61.3 0.1

Cumberland Golfview 77.7 63.1 63.1 0.0

1 Base 2007 ozone design values2 Future 2018 model predicted ozone design values3 Future 2018 model predicted ozone design values with emissions from shale gas development in the Sanford Sub-basin

Section 2 of this report provides brief background on shale gas and the general modeling approach. Section 3 discusses the methodology for photochemical modeling and incorporating the shale gas emissions into the modeling. The modeling results are presented in Section 4. The results are discussed and compared to other studies in Section 5.

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2. Introduction

North Carolina has several Triassic rift basins containing potentially economically recoverable shale gas reserves (USGS June 2012). The initial development is projected to occur in the Sanford Sub-basin, which lies within the larger Deep River formation (Figure 2-1). The extraction of the shale gas will involve many phases: drilling, hydraulic fracturing, processing, and transmission of the gas. The heavy duty diesel and natural gas fired engines that are the primary power source for these activities may be significant sources of nitrogen oxides (NOx) and volatile organic compounds (VOCs). These precursors then go on to react under sunshine to produce additional ozone across the region.

Figure 2-1. Triassic Basins (green) within North Carolina

Ozone concentrations recorded by monitors currently meet the 2008 8-hour ozone standard of 75 ppb across the eastern Piedmont, including the Triangle and Fayetteville regions (Figure 2.2). These monitors also meet or are projected to meet the EPA’s proposed revision to the current standard that ranges from 65-70 ppb by 2018. However, some monitors are predicted to be just below 65 ppb, and any significant increase in NOx emissions may cause ozone to increase above the proposed standard.

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DENR estimated the amount of emissions during year 6 of shale gas production, and this modeling study investigates the potential ground-level ozone impacts associated with year 6 of shale gas development in the Sanford basin.3 The shale gas emissions inventory was merged into readily available emissions files and used as inputs within the Community Multiscale Air Quality (CMAQ) model. The closest future year of modeling that was available is 2018, which provides a close estimate of potential ozone impacts compared to the projected year 6 which will occur between 2020 and 2025.

Figure 2-2. Map of the Monitor Locations and 2012-2014 Ozone Design Values, in parts per billion

3. Methodology

3.1 Photochemical Modeling

DENR utilized the Southeastern Modeling, Analysis and Planning (SEMAP) photochemical grid modeling platform to estimate the potential impacts on ozone formation associated with increases in NOx and

3 See “Estimate of Air Emissions from Shale Gas Development and Production in North Carolina”, April 2015, for further details.

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VOC from shale gas extraction activities. The SEMAP modeling platform was previously developed to estimate ozone and regional haze air quality impacts across the southeastern US. This modeling platform was selected for this study because it has been peer reviewed and represents the most recent modeling platform available for this study. The CMAQ model version 5.0.1 was used to simulate air pollutants over a national 36 kilometer (km) domain and a regional 12-km domain covering the southeast US (Figure 3-1). Major model configuration options are shown in Table 3-1. The Weather Research and Forecasting (WRF) model was used to generate meteorological inputs. For the modeling platform, the base year is 2007 and the future/projection year is 2018. The base year model performance meets or exceeds the EPA’s guidelines4. Both the base and future year modeling was replicated by DENR and closely matches with SEMAP. Therefore, the model performance of the modeling for this study should closely match the SEMAP modeling, with an ozone bias of less than 10% in central North Carolina. Additional details can be found at Odman, Adelman et al., 2014.

Figure 3-3. 36-km (left) and 12-km (right) SEMAP air quality modeling grids

4 US EPA - Guidance on the Use of Models and Other Analyses for Demonstrating Attainment of Air Quality Goals for Ozone, PM2.5, and Regional Haze.

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Table 3-2. CMAQ Configuration Options

Model Parameter CMAQ_v5.0Horizontal Advection Yamartino (hyamo)Vertical Advection WRF (vwrf5)Horizontal Diffusion MultiscaleVertical Diffusion Advanced Convective Method (ACM2)Gas Chemistry Mechanism CB05 with Chlorine (cb05tucl_ae6_aq6)Gas Chemistry Solver Euler Backward Iterative (ebi_cb05tucl)Aerosol Mechanism CMAQ 6th Generation (aero67)Clouds/Aqueous Chemistry ACM clouds with aero6 (cloud_acm_ae6)Plume in Grid none

For the shale gas modeling study, DENR modeled a period stretching from April 30 to Sept 29 which includes the days with higher ozone throughout the spring and summer of 2007. Although ozone concentrations are lower by 2018 according to the modeling, there are still 10-15 days predicted to be above 60 ppb around the shale gas exploration and development region. This is a sufficient number of days at that level to obtain a meaningful model ozone response. The simulation was split between 2 computer nodes, with each simulation having a 2 day spin-up period. Three model runs were performed to assess the potential impacts associated with emissions from shale gas exploration and development activity: A base year 2007 run (Base07), a future year 2018 run (Future18), and a future year 2018 run containing year 6 shale development emissions (Sanford18). An additional sensitivity run was completed to assess potential ozone impacts associated with only the NOx emissions estimated for year 6 of the shale exploration and development activities (Sanford18_NOx).

Table 3-3. Model Runs

Model Run Emissions Year

Summary

Base07 2007 Default 2005 SEMAP emissionsFuture18 2018 Default 2018 SEMAP emissions

Sanford18 2018 2018 emissions with emissions from shale gas exploration and development activity within the Sanford Sub-basin

Sanford18_NOx

2018 2018 emissions with NOx emissions from shale gas exploration and development activity within the Sanford Sub-basin

5 First the change in column mass is computed and then the vertical velocity is computed layer-by-layer using the horizontal mass divergence.6 Updated toluene chemistry and reactions of toluene and xylene with chlorine7 PM-other speciation includes non-carbon organic matter and metals. Primary organic carbon is aged. ISORROPIA v1.7 is replaced with ISORROPIA v.2.1 which treats the thermodynamics of crustal material.

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3.2 Emissions

The Base07 and Future18 emissions originate from the SEMAP modeling project. Details can be found in Odman, Adelman et al., 2014. Anthropogenic NOx emissions in North Carolina were estimated at 465,000 tons in 2007 and 227,000 tons in 2018, a decrease of nearly 51%. Anthropogenic VOC emissions in North Carolina were estimated at 419,000 tons in 2007 and 294,000 tons in 2018, a decrease of 30%. The 2018 SEMAP emissions estimates reflect most federal and state rules that are or will be scheduled to become effective by January 1, 2018. However, the 2018 SEMAP emissions do not include more recent rules and regulations such as Tier 3 Vehicle Emission and Fuel Standards.

Emissions from shale gas development in the Sanford Sub-basin are described in the DENR Shale gas report8. Total emissions were derived for year 6 of shale gas development, when there would be 121 new wells drilled and 247 wells in production. The projected NOx emissions from the Sanford shale gas activity are 3.7 tons/day, of which 2.6 tons/day or 71% will occur within Lee County based on geographic breakdown of the Sanford Sub-basin shown in Figure 2-2. The projected VOC emissions from the Sanford shale gas activity are 2.9 tons/day, of which 2.1 tons/day or 71% will occur within Lee County. For comparison, the projected emissions for Lee County absent of shale gas development are 926 tons/year, or 2.5 tons/day. Figure 3-2 and 3-3 compare the 2018 NOx and VOC emissions for Lee County and emissions from year 6 of shale gas activities within the Lee County portion of the Sanford Sub-basin. Shale gas development emissions are projected to nearly double the amount of NOx emissions in the Lee County area in 2018.

Figure 3-4. Estimated 2018 NOx and VOC Emissions for Lee County and for the Drilling Activity in the Sanford Sub-basin

8 See “Estimate of Air Emissions from Shale Gas Development and Production in North Carolina”, May 2015, for further details.

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Figure 3-5. Percentage of NOx and VOC Emissions for Lee County in 2018 and for the Drilling Activity in the Sanford Sub-basin

Emissions were converted to moles per second (units used by the CMAQ model) and allocated on an hourly basis to the 12-km modeling grid according to the percentage of the shale drilling region contained in each grid cell. Figure 3-4 shows the Sanford Sub-basin overlaid with the county lines and the 12-km modeling grid. The area of the Sanford Sub-basin is approximately 76,000 acres or 307 square kilometers (km2). Figure 3-5 shows the percentage of shale development emissions allocated to each grid cell. Note that over half of the shale development emissions are allocated to a single grid cell.

Figure 3-6. The 12-km SEMAP Air Quality Modeling Grid, Centered on Lee County (the Sanford Sub-basin is shaded in blue)

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Figure 3-7. Percent Allocation of the Shale Gas Development Emissions to the Modeling Grid

4. ResultsThe maximum average increase in ozone concentrations on days with predicted ozone levels above 60 ppb in 2018 in the Triangle and Lee County regions was 3.4 ppb (Figure 4-1). The maximum increase occurred in the grid cell containing the majority of the shale gas emissions. Outside of the shale gas area, the average ozone impacts decline rapidly, and beyond approximately 10 miles the average increase in ozone is less than 1 ppb. The modeling output data were run through the EPA’s Model Attainment Test Software to compute future design values at the ozone monitors for each of the runs. The results are shown in Table 4-1 and Figure 4-2.

The Blackstone monitor had the highest increase, at 1.9 ppb. Note that ozone measurements at the Blackstone monitor started only since January 1, 2014. Consequently, the design value for the Blackstone monitor was interpolated from 2012 and 2013 ozone concentrations observed at the Pittsboro and Fuquay-Varina monitors. The beginning design value, whether interpolated or real, will have no impact on the modeled ozone increase. Pittsboro had the next highest ozone increase of 0.9 ppb, followed by Fuquay-Varina at 0.3 ppb. The ozone increases for all other monitors in the state was 0.2 ppb or less.

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Figure 4-8. Average Change in Ozone for Days with 2018 Modeled Ozone Concentrations Greater than 60 ppb in the Triangle and Lee County Areas

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Table 4-4. Modeling Results for Ozone Monitors in and Near the Shale Gas Study Area

County MonitorBase07 Ozone Design Value (ppb)1

Future18 Ozone Design Value (ppb)2

Sanford18 Ozone Design Value (ppb)3

Change from Future18 to Sanford18 (ppb)

Lee Blackstone 74 59.5 61.4 1.9

Chatham Pittsboro 71.7 55.4 56.3 0.9

Wake Fuquay-Varina 77 62.3 62.6 0.3

Montgomery Candor 73 58.8 59 0.2

Wake Millbrook 79 63.6 63.7 0.1

Durham Durham 74 59 59.1 0.1

Cumberland Wade 75.3 60.5 60.6 0.1

Granville Butner 79.3 63.5 63.6 0.1

Johnston West Johnston 75 59.7 59.8 0.1

Franklin Franklinton 76.3 61.2 61.3 0.1

Cumberland Golfview 77.7 63.1 63.1 0.0

1 Base 2007 ozone design values2 Future 2018 model predicted ozone design values3 Future 2018 model predicted ozone design values with emissions from shale gas development in the Sanford Sub-basin

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Figure 4-9. Change in Predicted 2018 Design Values in the Triangle and Lee county areas.

The DENR also looked at the change in the number of days for which ozone exceeded 60, 65, and 70 ppb in the 2018 modeling (Figure 4-3). The number of days above 60 ppb increases from 1 to 6 days at the Blackstone monitor, with no days above 65 ppb. Similarly, the Fuquay-Varina and Pittsboro monitors have slight increases in the number of days exceeding 60 ppb, with no increases in the frequency of days above 65 ppb due to shale gas emissions. The grid cell with the majority of the shale emissions (Peak Shale Emissions Grid Cell) was also examined. Like Blackstone, there is an increase in the frequency of days with ozone above 60 ppb. There was one day that is predicted to exceed 65 ppb due to the shale gas development emissions.

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Figure 4-10. Change in the Number of Days with Ozone Concentrations above 60, 65, and 70 ppb for the Fuquay-Varina, Pittsboro, Blackstone Monitors, and the model grid cell with peak shale drilling

emissions (d).

A sensitivity run was made that included only the NOx emissions from the shale gas development (Sanford18_NOx). The average ozone impacts and predicted design values are virtually identical to the run with all shale gas development emissions (Sanford18). This suggests that ozone in the region is NOx limited and that VOC emissions from the shale gas development have little to no impact on ozone formation.

5. Discussion and Conclusions

There have been a few modeling projects that investigated the impacts of shale gas production on ozone, though for much larger shale gas plays (Table 5-1). Roy et al. (2014) used the CMAQ photochemical model on a 36-km grid to estimate the impacts of ozone on the Marcellus Shale in Pennsylvania, West Virginia, and New York. The maximum impact on 8 hour ozone was 5 ppb in the Marcellus shale region. Kembal-Cook et al. (2010) used the Comprehensive Air quality Model with extensions (CAMx) to simulate ozone impacts of up to 4-6 ppb from shale gas production in the Haynesville shale region in Louisiana and Texas. The modeled ozone impacts for the Sanford Sub-basin shale gas study area are consistent with these other studies.

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Table 5-5. Comparison of Modeled Ozone Impacts of the Sanford Shale Development to “Best Estimate” Emission Scenarios for the Marcellus and Fayetteville Shale Development

Shale Basin New Wells Cumulative Wells

NOx tons/day

NOx tons per new well

Maximum Average increase in Daily Max 8 hour ozone

Sanford 120 368 5.9 0.049 3.4Marcellus1 3500 40,000 129 0.0369 5Haynesville2 565 1875 82 0.145 5

1 Baseline or Best Estimate Scenario from Roy et al. (2014)2 Moderate scenario from Kembal-Cook et al. (2010)

Overall, the per well emission estimates are similar to those used for the above studies. However, the shale gas development emissions modeled in these studies were distributed over a wide region that encompassed the entire shale basins due to uncertainties in well drilling locations. By comparison, the drilling activity within the Sanford Sub-basin is targeted over a much smaller geographic area, leading to a greater number of wells (and hence emissions) per unit area compared to the Marcellus and Haynesville basins. The net effect of the more intense drilling and emissions on the modeling is predicted ozone impacts on par with these larger shale basins despite the lower total emissions.

In summary, DENR used an existing modeling framework to predict the potential impacts of year 6 shale gas development using emissions estimates from the DENR Shale Gas Inventory. Year 6 is estimated to have the peak emissions for the shale gas development. The maximum average increase in 8 hour ozone concentrations on days with higher ozone (> 60 ppb) in 2018 is 3.4 ppb. The average increase in ozone declines rapidly outside the perimeter of the Sanford Sub-basin. Of the ozone monitors across the region, Blackstone had the highest ozone design value increase of 1.9 ppb, followed by Pittsboro at 0.9 ppb. The increase in design values for all other monitors in the region is less than 0.3 ppb. The predicted 2018 design values without shale gas development emissions are below 65 ppb, and the additional emissions from shale gas development is not expected to push any design values above 65 ppb. Likewise, the modeling indicates there will be little to no increase in the number of days with ozone above 65 ppb.

6. References

North Carolina Oil and Gas Study under Session Law 2011-276, Prepared by the North Carolina Department of Environment and Natural Resources and the North Carolina Department of Commerce, April 30, 2012. Estimate of Air Emissions from Shale Gas Development and Production in North Carolina, Prepared by the North Carolina Department of Environment and Natural Resources, Division of Air Quality, May 2015. Kemball-Cook, S, Bar-Ilan, A., Grant, J., Parker, L., Jung, J. Santamaria, W., Mathews, J., Yarwood, G., 2010. Ozone impacts of natural gas development in the Haynesville Shale. Environmental Science and Technology, 44:9357-9363.

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Roy, A.A., P.J. Adams and A.L. Robinson, 2014. Air pollutant emissions from the development, production, and processing of Marcellus Shale natural gas. Journal of the Air & Waste Management Association, 64(1), 19-37.

Roy, A.A., P.J. Adams and A.L. Robinson, 2015. Impact of natural gas development in the Marcellus 1 Shale on regional ozone levels. In press.

Odman, Talat, Zac Adelman, et al. SEMAP – SEMAP Emissions and Air Quality Modeling Final Report. http://semap.ce.gatech.edu/sites/default/files/files/SEMAP-Revised-Final-Report_Final.pdf

US EPA - Guidance on the Use of Models and Other Analyses for Demonstrating Attainment of Air Quality Goals for Ozone, PM2.5, and Regional Haze. http://www.epa.gov/scram001/guidance/guide/final-03-pm-rh-guidance.pdf

USGS June 2012. Assessment of Undiscovered Oil and Gas Resources of the East Coast Mesozoic Basins of the Piedmont, Blue Ridge Thrust Belt, Atlantic Coastal Plain, and New England Provinces, 2011. Fact Sheet 2012-3075: http://pubs.usgs.gov/fs/2012/3075/fs2012-3075.pdf.

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http://pubs.usgs.gov/fs/2012/3075/fs2012-3075.pdf

http://semap.ce.gatech.edu/sites/default/files/files/SEMAP-Revised-Final-Report_Final.pdf

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