Anadarko Petroleum Corporation 2-1 Trinity Consultants 

 

2. REPRESENTATION OF MODELED SOURCES 

2.1. EMISSIONS SOURCES AND POTENTIAL TO EMIT 

The	sources	of	emissions	for	the	proposed	project	primarily	consist	of	internal	combustion	engines,	

painting	operation,	welding	operation,	dust	collectors,	mud‐degassing,	water	blasting	operation,	

miscellaneous	equipment,	and	fuel	storage	tanks.		For	the	support	vessels,	the	only	emission	sources	

are	internal	combustion	engines	and	fuel	storage	tanks.		Anadarko	will	use	the	“worst‐case”	

potential‐to‐emit	scenario	among	all	the	operating	scenario	discussed	in	the	Section	3	for	assessing	

air	quality	impacts	to	demonstrate	compliance	with	the	Class	I	Increments,	AQRVs	and	Class	II	SILs.		

This	will	give	Anadarko	the	flexibility	to	drill	and	operate	at	any	location	within	the	worse‐case	lease	

block	(nearest	to	respective	Class	I	and	Class	II	areas)	or	at	any	other	location	further	away	from	a	

Class	I	area	within	the	“wedge.”		

As	described	in	the	Section	3	of	this	report,	the	project	includes	six	possible	operating	scenario	or	an	

equivalent	combination	thereof.		Refer	to	Section	3	for	the	details	of	each	operating	scenario	and	the	

proposed	air	emission	sources	and	their	operating	conditions	associated	with	it.			

Among	all	the	support	vessels,	the	supply	boats	will	be	very	frequently	used.		All	other	support	

vessels	such	as	well	evaluation	vessels,	stimulation	vessels,	tugs,	and	barges,	will	be	used	in	a	

specific	operating	scenario.		Moreover,	the	supply	boats	generate	higher	emissions	when	they	are	in	

transit	arriving/departing	from	the	drill	ship	than	emissions	generated	when	the	supply	boats	are	

located	adjacent	to	the	drill	ship	during	loading/unloading	operations.		The	other	support	vessels	

generally	generate	more	emissions	during	performing	operations	in	the	vicinity	of	the	drill	ship	

when	compared	against	the	emissions	generated	during	their	transit.		Hence,	placing	a	supply	boat	

source	at	a	distance	of	25	nautical	miles	from	the	worst‐case	drillship	location	in	the	direction	of	

nearest	receptor	should	represent	the	worst	case	support	vessel	emission	scenario	for	air	

dispersion	modeling	analysis.		The	worst‐case	support	vessels	emissions	(i.e.,	supply	boats	with	

highest	PTE)	were	utilized	for	this	modeling	analysis.			

For	performing	air	dispersion	analysis,	maximum	total	emissions	(i.e.,	sum	of	the	drillship	and	

supply	boat	emissions)	for	each	pollutant	were	considered.		Table	2‐1	compares	the	emissions	from	

different	operational	scenarios	and	modeled	emission	rates.		The	modeled	emission	rates	represent	

the	worst	case	combination	among	the	different	operating	scenario.			

Table 2‐1.		Emission Rates Comparison		

Pollutant Source Emission Rates (lb/hr)

Model

ed		

Gas

Flowbac

k

Scenario

Oil

Flowback

Scenario

Stimulat

ion

Vessel

Scenario

General

Well

Completi

on

Scenario		

Well

Evaluatio

n Vessel

Scenario

Drilling		

NOx

Supply	

Boats	 84	 42 42 42 84 42 84

Drill	

ship	 540	 566 582 575 513 573 534

Total 624 608 624 617 597 615 618
Anadarko Petroleum Corporation 2-2 Trinity Consultants 

 

Pollutant Source Emission Rates (lb/hr)

Model

ed		

Gas

Flowbac

k

Scenario

Oil

Flowback

Scenario

Stimulat

ion

Vessel

Scenario

General

Well

Completi

on

Scenario		

Well

Evaluatio

n Vessel

Scenario

Drilling		

PM10

Supply	

Boats	 3	 1 1 1 2 1 2

Drill	

ship	 27	 26 26 10 9 10 10

Total 30 27 25 11 11 11 12

SO2

Supply	

Boats	 0.5	 <0.1	 <0.1	 <0.1	 0.1	 <0.1	 <0.1	

Drill	

ship	 1.5	 <2	 <1	 <0.5	 0.4	 0.4	 0.4	

Total 2 <2 <1 <0.5 2 0.5 0.5

CO

Supply	

Boats	 100	 29	 29	 29	 58	 29	 58	

Drill	

ship	 1,000	 1,062	 779	 191	 177	 181	 182	

Total	 1,100	 1,091	 809	 220	 235	 210	 240	

2.2. Q/D ANALYSIS 

Anadarko	has	completed	a	Q/d	calculation	to	assess	potential	impacts	of	the	proposed	drilling	and	

well	completion	operations	on	the	nearest	Class	I	area.		The	Q/d	analysis	compares	the	ratio	of	the	

sum	of	proposed	annualized	maximum	24‐hour	emission	rates	of	all	visibility	impairing	pollutants	

(in	tons	per	year)	and	the	distance	to	the	nearest	Class	I	area	(in	km)	to	a	threshold	value	of	10,	as	

determined	by	the	FLM.		The	“Q”	is	the	combined	emissions	increase	from	a	source	of	SO2,	NOX,	

PM10,	and	H2SO4	in	tons	per	year	(tpy)	based	on	the	maximum	hourly	emissions	and	“d”	is	the	

nearest	distance	to	a	Class	I	area	in	km	from	the	source.	11		Emissions	from	sources	that	operate	

intermittently	or	seasonally	will	be	adjusted	to	account	for	year	round	operation.			The	emissions	

represented	in	the	Q/d	analysis	are	conservatively	based	on	the	highest	emissions	between	the	

drilling	and	well	completion	operations.		Based	on	the	results,	a	Class	I	area	AQRV	analysis	is	

required	for	the	project	because	the	Q/d	ratio	for	the	proposed	source	is	greater	than	10.		A	copy	of	

the	Q/d	analysis	is	provided	in	Appendix	F.

2.3. MODELED PARAMETERS 

As	mentioned	previously,	Anadarko	is	requesting	the	flexibility	to	drill	and	complete	one	or	more	

wells	in	any	of	the	lease	blocks	within	the	“wedge”	while	complying	with	any	operational	and	

emission	limitations	prescribed	in	the	air	permits	that	will	be	issued.		Therefore,	the	Class	I	area	

modeling	analysis	was	performed	for	each	Class	I	area	with	the	drillship	assumed	to	be	located	at	

the	closest	point	within	the	“wedge”	of	the	project	(worst‐case	location)	to	the	Class	I	areas.			

For	Breton‐NWR,	the	NW	corner	of	the	Desoto	Canyon	lease	block	141	was	determined	to	be	the	

worst‐case	drillship	location.		For	St.	Marks	NWR	and	Bradwell	Bay	Wilderness,	the	NE	corner	of	the	

																																																															

11 U.S. Forest Service – Air Quality Program, National Park Service – Air Resources Division, U.S. Fish and Wildlife 

Service – Air Quality Branch, Phase I Report of the Federal Land Managers’ Air Quality Related Values Workgroup 

(FLAG)--Revised, 2010.