Methane emissions from above-ground natural gas distribution facilities in the urban environment: A fence line methodology and case study in Calgary, Alberta, Canada

Figures & data

Figure 1. Locations of natural gas gate and control facilities surveyed in this study

Figure 2. Examples of different fencing around facilities. (a) This facility had chain link fencing on the north side, and ~3 m tall solid walls around the east, west, and south sides (note residential area in background). (b) A solid wall ~3 m tall around a gate facility. (c) Chain link fencing with slats. (d) A mix of ~2 m tall chain link fencing with slats and wooden fencing (note residential area in background). The anemometer tower in the foreground of (b)-(d) is 1.65 m tall

Figure 3. Illustration of survey methodology using a portable backpack trace gas analyzer, GPS, and stationary anemometer

Table 1. Summary statistics for each facility. Wind metrics include the mean wind speed ($\bar{u}$), resultant wind direction (θ_R), and wind direction standard deviation (${\sigma }_{\theta }$) based on the Yamartino (1984) method. The sample size of CH₄ measurements from the walking surveys at each site is denoted by n. We supplemented missing wind metrics for select facilities with average hourly wind speed and direction from the Calgary International Airport automated weather station (World Meteorological Organization ID: 71877). Row shading corresponds to CH₄ emissions plausibility: high (white), medium (light gray), low (gray)

ID	Lat. (°)	Long. (°)	Date	n	$\bar{u}$ (m/s)	θR (°)	${\sigma }_{\theta }$ (°)	5^th Percentile CH4 (ppbv)	Peak ΔCH4 (ppbv)	ΔCH4 σ (ppbv)	DW 95^th – UW 95^th (ppbv)	CH3SH odor	Distance to nearest residential (m)
1	50.973	−114.119	2020–05-27	520	1.48	162.67	56.75	1944.53	40.8	4.26	7.6	N	74.7
2	51.023	−114.165	2020–05-25	859	1.77	120.48	62.4	1932.52	5471.74	555.14	2641.36	Y	97.9
3	51.052	−114.165	2020–05-28	1510	2.25	337.01	29.49	1949	490.27	62.08	235.83	Y^c	110.7
4	50.992	−114.095	2020–05-27	504	2.33	177.8	22.04	1942.84	952.59	76.57	36.13	Y	29.3
5	50.974	−114.078	2020–05-27	1388	1.67	128.82	83.95	1942.87	238.9	27.4	98.6	Y	49.3 ^f
6	50.974	−114.052	2020–05-27	775	1.98	146.83	26.75	1942.72	48.83	5.71	−24.19	N	37.9
7	50.950	−114.087	2020–05-28	750	2.24	340.35	44.57	1954.81	468.29	84.72	241.93	Y^c	191.5
8	50.940	−114.110	2020–05-28	614	1.06	270.92	68.66	1954.63	27,865.27	2231.21	8528.9	Y^c	19.5
9	50.950	−114.044	2020–05-28	590	2.54	296.43	27.41	1965.56	604.1	101.41	439.89	Y^c	26.7 ^c
10	50.929	−114.050	2020–05-28	422	4.87	356.08	26.4	1960.46	19.01	4.39	−1.96	N	84.9
11	50.919	−114.048	2020–05-29	660	3.06^a	300.00^b	–	1966.42	198.76	13.79	−26.48	N	36.2
12	50.891	−114.084	2020–06-05	480	3.79	352.8	22.41	1960.4	1414	145.61	433.57	Y	129.9
13	50.892	−114.010	2020–06-05	361	2.78	343.79	25.76	1953.2	705.25	115.43	522.33	Y^c	266.5
14	50.897	−113.980	2020–06-01	475	2.22^a	190.00^b	–	1949.46	42.35	2.69	10.52	N	119.3
15	50.903	−113.977	2020–06-01	918	2.22^a	190.00^b	–	1955.55	884.42	65.67	167.46	Y	33.4
16	50.905	−113.934	2020–06-05	960	2.51	341.58	41.06	1955.86	183.09	23.33	76.57	Y	45.8
17	50.961	−113.918	2020–06-03	744	3.92	122.97	24.91	1942.8	952.66	80.29	107.91	Y	1058.8
18	50.891	−114.047	2020–05-29	240	3.33^a	240.00^b	–	1961.39	3.2	0.77	0.35	N	95
19	50.890	−114.047	2020–05-29	654	3.33^a	240.00^b	–	1961.36	34.49	8.3	−8.98	N	40.5
20	50.891	−114.042	2020–05-29	366	3.06^a	300.00^b	–	1955.83	315.52	54.81	288.64	Y	101.5
21	50.890	−114.042	2020–06-05	390	2.98	314.78	36.21	1977.85	1626.59	147.19	354.53	Y	92.4
22	51.067	−114.152	2020–05-25	1184	2.83	110.95	31.2	1935.53	974.24	131.4	450.23	Y	42.9
23	51.132	−114.210	2020–05-25	1099	3.38	59.03	19.43	1933.87	824.21	106.67	358.68	Y^c	26.5
24	51.183	−114.211	2020–05-25	713	3.85	171.58	13.15	1934.33	5955.33	750.7	3143.34	Y	354.1
25	51.122	−114.093	2020–05-26	1179	4.91	173.54	26.88	1976.82	119.14	18.97	48.61	N	41.2
26	51.148	−114.025	2020–05-26	619	5.49	189.03	19.55	1975.39	586.59	95.89	451.21	Y	1287.5
27	51.095	−113.936	2020–06-03	676	2.72	93.16	32.29	1943.8	275.16	39.27	153.22	Y^c	20.6
28	51.095	−113.935	2020–06-03	181	1.76	94.02	45.09	1944	17.6	3.82	8.94	N	21.9
29	51.068	−113.933	2020–05-26	791	3.66	185.67	21.87	1972.68	135.97	10.45	12.65	N	32.1
30	51.068	−113.962	2020–06-03	683	3.88	89.58	27.56	1943.05	360.94	39.38	90.16	Y	82.3
31	51.067	−113.903	2020–06-03	1568	3.02	107.65	21.41	1942.6	1264.77	227.84	874.42	Y	496.7
32	51.014	−113.956	2020–06-05	684	2.89	312.39	24.01	1963.21	686.25	148.04	582.16	Y	458.7
33	50.979	−114.141	2020–05-27	1521	1.63	110.55	61.82	1943.4	796.54	53.62	166.8	Y^c	193.3

^aHourly wind speed from a weather station at the Calgary International Airport (World Meteorological Organization ID: 71877).

^bHourly wind direction from a weather station at the Calgary International Airport (World Meteorological Organization ID: 71877). The value has been modified to represent the direction the wind is traveling.

^cFacilities where mercaptan odor was detected from nearby sidewalks, alleys, or pathways.

Figure 4. Concentration maps of ΔCH₄. Arrows denote resultant wind direction from on-site measurements or from the Calgary International Airport

Figure 4b. (Continued)

Figure 5. Facility rankings based on peak ΔCH_4.

Table 2. OTM33A EQ summary of emissions rate estimates, mean wind speeds ($\bar{u}$), measurement distances, stability classes, and data quality indicator (DQI) scores. Reported stability classes are averages during survey times based on the standard deviation of the 2D wind direction and turbulent intensity. Stability classes range from 1–7 with higher numbers representing increasingly stable conditions

ID	Emissions rate (mg CH4 s^−1)	$\bar{u}$ (m/s)	Downwind distance (m)	Estimated Wind Stability Class	DQI
9	3.40	1.86	10	3	18
12–1	1.95	2.57	10	4	39
12–2	2.02	3.19	10	4	29
13	1.27	3.17	10	4	39
21	11.32	2.48	10	4	8
24	15.56	2.95	10	6	8
32	30.79	3.15	20	3	12

Yamartino, R. J. 1984. A comparison of several “single-pass” estimators of the standard deviation of wind direction. Journal of Applied Meteorology and Climatology. 23(9):1362–66.

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