From: Michael Carbon [mcarbon@environcorp.com]

Sent: Thursday, April 25, 2013 12:15 PM

To: Shepherd, Lorinda

Cc: Donald Evans (DOEV@statoil.com); Kjersti Seim (kjes@statoil.com); Kyle 

Heitkamp; Michael Carbon

Subject: Statoil - Response to EPA Email Questions

Attachments: Maersk_Developer-Emissions_and_Forms.pdf; 

Transocean_Discoverer_Americas-Emissions_BACT_and_Forms.pdf

Importance: High

Lori,

This email correspondence contains responses to a series of questions you provided to Statoil over the 

last month and a half. Responses are separated for each of the two drill rigs, and a series of 

attachments include more detailed emission calculations.

Maersk Developer

Will the project include flaring?

No, the Developer does not have flare booms installed and Statoil is not proposing to conduct any 

flaring during the exploratory drilling operations.

Will any welding activities be conducted during the drilling campaign?

Yes, welding occurs as part of regular maintenance activities. Rig operators estimate that up to 

240 pounds of welding electrodes could be used per 180-day drilling campaign. Electricity for welding is 

provided by the main engines on the drilling vessel. ENVIRON has estimated emissions from the welding 

activities to be less than 0.01 tpy of PM/PM10/PM2.5 and approximately 7 lb/yr of total HAP. Detailed 

emission calculations for welding activities are attached to this email.

Since potential emissions of regulated air pollutants are less than 2 tpy, and HAP emissions are less than 

1,000 lb/yr, the emission levels from welding activities are considered insignificant per 40 CFR 

71.5(c)(11)(ii). There are no applicable regulations that would apply to the maintenance welding 

activities.

Detailed emission calculations for welding activities and application forms that required an update are 

attached to this email.

Will any painting (spray or roller) activities be conducted during the drilling campaign?

Yes, painting occurs as part of regular maintenance activities. Rig operators estimate that up to 

380 gallons of paint coating and 310 gallons of paint thinner could be used per 180-day drilling 

campaign. Paint is applied using both brush/roller and sprayer depending on the size and location that 

needs to be painted; however, ENVIRON has assumed 100 percent of the paint is applied by spray to 

conservatively account for particulate matter emissions generated from paint overspray.

MSDS information (Percent Solids, VOC content, HAP content, etc.) was obtained for each paint coating 

and thinner used on the drill rig. ENVIRON has estimated emissions from painting in Table 1 below.

Detailed emission calculations and application forms that required updating are attached to this email.
Since potential HAP emissions (Xylene) are above the 1,000 lb/yr insignificance level, painting activities 

are not considered an insignificant activity. There are no applicable regulations that would apply to the 

maintenance painting activities.

Table 1. Maersk Developer – Painting Emissions

Pollutant Emissions

(tpy)

PM10 0.3

PM2.5 0.1

VOC 1.5

Xylene 0.8

Will any seismic operations require additional emission units not included in the application?

No, vertical seismic profile (VSP) activities during the Statoil exploratory drilling campaign will be drill rig 

based. Electric compressors powered by the drill rig main engines will be utilized for all VSP activities 

and Statoil will not be including any additional boats or compression/spark ignition engines as part of 

the seismic measurement activities.

Description of cement/mud mixing activities?

Dry cement and mud additives are mixed onboard the drill rig for use in casing and drilling operations.

On the Developer drill rig, the mixer is completely enclosed and air that is displaced by the addition of 

dry materials and/or wet mud is directed back to the enclosed material conveyors. The enclosed 

conveyor and mixing system prevents the dry cement and mud mixing activities from being emitted as 

particulate matter to the atmosphere. We do not anticipate particulate emissions from this fully 

enclosed process.

Transocean Discoverer Americas

Will the project include flaring?

No, the Discoverer Americas does not have flare booms installed and Statoil is not proposing to conduct 

any flaring during the exploratory drilling operations.

Will any welding activities be conducted during the drilling campaign?

Yes, welding occurs as part of regular maintenance activities. Rig operators estimate that up to 

50 pounds of welding electrodes could be used per 180-day drilling campaign. Electricity for welding is 

provided by the main engines on the drilling vessel. ENVIRON has estimated emissions from the welding 

activities to be less than 0.002 tpy of PM/PM10/PM2.5 and less than 2 lb/yr of total HAP.

Since potential emissions of regulated air pollutants are less than 2 tpy, and HAP emissions are less than 

1,000 lb/yr, the emission levels from welding activities are considered insignificant per 40 CFR 

71.5(c)(11)(ii). There are no applicable regulations that would apply to the maintenance welding 

activities. Detailed emission calculations for welding activities and application forms that required an 

update are attached to this email.

Will any painting (spray or roller) activities be conducted during the drilling campaign?
Yes, painting occurs as part of regular maintenance activities. Rig operators estimate that up to 

250 gallons of paint coating and 250 gallons of paint thinner could be used per 180-day drilling 

campaign. Paint is applied using both brush/roller and sprayer depending on the size and location that 

needs to be painted; however, ENVIRON has assumed 100 percent of the paint is applied by spray to 

conservatively account for particulate matter emissions generated from paint overspray.

MSDS information (Percent Solids, VOC content, HAP content, etc.) was obtained for each paint coating 

and thinner used on the drill rig. ENVIRON has estimated emissions from painting in Table 2 below.

Detailed emission calculations and application forms that required updating are attached to this email.

Since potential emissions of regulated air pollutants are less than 2 tpy, and individual HAP emissions 

are less than 1,000 lb/yr, the emission levels from painting activities are considered insignificant per 40 

CFR 71.5(c)(11)(ii). There are no applicable regulations that would apply to the maintenance painting 

activities.

Table 2. Transocean Discoverer – Painting Emissions

Pollutant Emissions

(tpy)

PM10 0.2

PM2.5 0.1

VOC 1.5

Xylene 0.4

Will any seismic operations require additional emission units not included in the application?

No, vertical seismic profile (VSP) activities during the Statoil exploratory drilling campaign will be drill rig 

based. Electric compressors powered by the drill rig main engines will be utilized for all VSP activities 

and Statoil will not be including any additional boats or compression/spark ignition engines as part of 

the seismic measurement activities.

Description of cement/mud mixing activities?

Dry cement and mud additives are mixed onboard the drill rig for use in casing and drilling operations.

On the Discoverer Americas drill vessel, the mixing area is not fully enclosed like the Maersk Developer, 

but the Discoverer Americas contains dust pickup points routed to a dust collector for control. There are 

no applicable regulations that would apply to the handling of cement/mud additives.

Particulate matter emissions are based on the dust collector design flow rate (4,415 cfm) and an exhaust 

grain loading of 0.01 grains per dry standard cubic foot, established from discussions with the dust 

collector manufacturer. Assuming continuous dust collector operation (180 days/yr), potential 

PM/PM10/PM2.5 emissions are 0.4 lb/hr and 0.8 tpy. The cement handling activities are not considered 

insignificant. Detailed emission calculations and updated forms are attached to this email.

Update BACT EGEN BACT Analysis for Engine Replacement?

The BACT analysis included in the original permit application did not include technical feasibility or cost 

effectiveness for replacement of the Transocean Discoverer Americas emergency generator engine 

because, at that time, Statoil believed the engine was Tier 2 compliant. Subsequent information 

provided to Statoil showed the engine was certified as IMO compliant engine, but the engine was not 

certified Tier 2 compliant.
Compliance with EPA’s emission standards (Tier 2, Interim Tier 4, and Final Tier 4) is an inherent part of 

engine design and no modifications or retrofits can be made to an existing engine to obtain a newer 

emission certification level. The NSPS Subpart IIII requires the owner or operator to purchase a certified 

engine in order to comply with the NSPS regulations (40 CFR 60.4211(c)) and does not allow the engine 

manufacture to provide certification for any Tiered emission levels if additional emission controls were 

to be added to the engines. Therefore, to meet an emission certification level, the engine would need 

to be replaced with a new engine. Replacement of the emergency engine would require the new engine 

to have a similar output rating, meet vessel space and footprint restrictions, and weight distribution 

requirements that were determined during the vessel design phase. Replacement of the engine could 

also require a re-design of the engine frame, modification of drill vessel structure, and potentially 

require the rig owner to recertify the vessel.

Even though the technical limitations provided above would likely prove replacement of the existing 

emergency engine is technically infeasible, Statoil has included conservative cost effectiveness 

calculations assuming that a Tier 4 engine (meeting most stringent future emission standard) is 

available. A Tier 4 engine would be limited to NOx emissions of 0.67 g/kW-hr (40 CFR 1039.101, Table 

1).

Conservatively assuming a new 3,000 hp engine would cost $20,000 and require one day in dry dock to 

install ($500,000), the cost effectiveness of the engine replacement is over $90,000 per ton of NOx 

removed. The replacement of an emergency engine would require a yard stay based on safety concerns 

that the loss of main engines at sea without an emergency backup would clearly be an unsafe situation.

Based on the very conservative cost effectiveness calculations, replacement of the emergency generator 

engine with a future Tier 4 engine would not be cost effective. The cost effectiveness calculations for 

the EGEN replacement are attached.

Update BACT ACOMP BACT Analysis for Engine Replacement?

The BACT analysis included in the original permit application did not include technical feasibility or cost 

effectiveness for replacement of the Transocean Discoverer Americas emergency air compressor 

engines engine because, at that time, Statoil believed the engines were Tier 2 compliant. No emission 

certification documents were available from the engine manufacture, so Statoil has conservatively 

assumed the engines do not meet any emission standards.

Compliance with EPA’s emission standards (Tier 2, Interim Tier 4, and Final Tier 4) is an inherent part of 

engine design and no modifications or retrofits can be made to an existing engine to obtain an emission 

certification level. The NSPS Subpart IIII requires the owner or operator to purchase a certified engine in 

order to comply with the NSPS regulations (40 CFR 60.4211(c)) and does not allow the engine 

manufacture to provide certification for any Tiered emission levels if additional emission controls were 

to be added to the engines. Therefore, to meet an emission certification level, the two emergency 

engines would need to be replaced with new engines. Replacement of the emergency engines would 

require the new engines to have a similar output rating, meet vessel space restrictions, and weight 

distribution requirements that were determined during the vessel design phase. Replacement of the 

engines could also require a re-design of the engine frame, modification of drill vessel structure, and 

potentially require the rig owner to recertify the vessel.

Even though the technical limitations provided above would likely prove replacement of the existing two 

emergency air compressor engines is technically infeasible, Statoil has included conservative cost 
effectiveness calculations assuming that Tier 4 engines (meeting most stringent future emission 

standard) are available. A similar sized Tier 4 engine would be limited to NOx emissions of 4.7 g/kW-hr 

(40 CFR 1039.101, Table 1 (19 ≤ kW < 56)).

Conservatively assuming a new 50/68 hp engine would cost $1,000 and no other costs would apply to 

the engine replacement, the cost effectiveness of the engine replacement is over $88,000 per ton of 

NOx removed. Based on the very conservative cost effectiveness calculation, replacement of the 

emergency air compressor engines with future Tier 4 engines would not be cost effective. The cost 

effectiveness calculations for the ACOMP replacement are attached.

Updated PSD Significance Analysis

Based on welding, painting, and dust collector (Transocean rig only) emissions, ENVIRON has updated 

the PSD Significance Analysis summary for particulate matter and VOC emissions from the two operating 

scenarios (Maersk Developer and Transocean Discoverer Americas). Table 3 presents the update PSD 

Significance Analysis for PM, PM10, PM2.5 and VOC. The updated emission calculations for both drilling 

scenarios do not change the pollutants currently subject to PSD review. Both scenarios are still subject 

to PSD for only NOx emissions.

Table 3. Updated PSD Significance Analysis

Pollutant

Maersk 

Developer 

Scenario a

(tpy)

Transocean 

Discoverer 

Americas 

Scenario b

(tpy)

PSD 

Significant 

Threshold

(tpy)

Subject to 

PSD 

Review?

PM 10.6 10.2 25 No

PM10 9.8 9.4 15 No

PM2.5 9.5 9.2 10 No

VOC 27.6 24.8 40 No

Notes:

a – Maersk Developer scenario PTE were updated to include 

welding and painting emissions.

b – Transocean Discoverer Americas scenario PTE were updated 

to include welding, painting, and dust collector emissions.

Air Quality Impact Analysis

The inclusion of maintenance activities (welding and painting) and cement handling (Transocean only) 

result in slight increases on short-term and annual particulate matter and VOC emissions from the two 

drilling vessel scenarios. As presented in Table 3 of this email, the updated operating scenario emissions 

still show that only NOx triggers PSD review, and PM2.5 PSD review is also triggered due to NOx 

emissions. The addition of welding, painting, and cement handling does not increase NOx emissions, so 

no changes to previous modeling completed for Class I or Class II NO2 concentrations or Class I nitrogen 

deposition are required.

The slight increase in primary PM2.5 emissions would have an insignificant impact on the conclusions 

drawn from previous CALPUFF modeling. Tables 6.3.1-1 and 6.4.11-1 of the January 28, 2013 revised air 
quality impact analysis show that CALPUFF-predicted Class I and Class II PM2.5 concentrations are well 

below relevant modeling criteria (Class I and Class II Significant Impact Levels). Previous visibility 

modeling results show the change to visibility in Breton Wilderness is dominated by nitrates formed 

from NOx emissions from the two drilling vessel scenarios and direct PM2.5 emissions play a much 

smaller role in CALPUFF-predicted visibility impacts. Based on these reasons ENVIRON believes no 

additional modeling is required for the small increase in potential PM2.5 emissions as it would have an

insignificant impact to the Class I and Class II PM2.5 modeling concentrations and to the visibility impact 

analysis already provided to EPA.

Additionally, please note that we have prepared responses to Stan Krivo’s email questions related to the 

Statoil air quality analysis and we will copy you on those responses.

Please do not hesitate to contact us with any additional questions or if you would like to discuss 

anything about Statoil’s permit application.

Thanks

Michael

Michael Carbon | Principal

ENVIRON | www.environcorp.com

8235 YMCA Plaza Drive | Suite 300 | Baton Rouge, LA 70810

T: 225.408.2691| M: 225.907.3822 | mcarbon@environcorp.com

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