ENVIRON International Corp. 19020 33rd Avenue West, Suite 310

, Lynnwood, WA 98036

V +1 425.412.1800 F +1 425.412.1840 environcorp.com July 12, 2013

Via Electronic Mail

Stan Krivo EPA Region 4 Krivo.Stanley@epa.gov

Re: Statoil PSD Application

– Response to comments

Dear Mr Krivo :

This letter is in response to your email to me dated Thu July 11, 2013. I i nclude your text in blue, with my responses below each section

.



### Revised Support and Crew Boat Modeling

– The revised modeling for support vessels and crew boats appears to uses two methodologies; one to address the short term standard and one

for the long

- term annual standard. The modeling to assess the long

- term standard appears to be unchanged from the previous version of the application (i.e., volume line source from the drilling vessel extending 25 nautical miles towards the nearest shoreline/ Class I area) while the

short

- term modeling had the support and crew boats modeled as a point sources located 25 nautical miles from the drilling vessel at the closest point to the shore line and PSD Class I

area.

- EPA’s comments on the previous version of the application requested an explanation and/or demonstration of the appropriateness of the input parameters used in volume line source modeling procedure. EPA did not request a more conservative modeling approach for the support vessels and cr ew boats.

- It appears that the volume line source modeling for the long

- term standard was unchanged from the previous version of this application. Therefore, our previous comments on the appropriateness of the volume line source initial input parameters and modeling procedure are still applicable and should be addressed.

A revised Table 6.3.1

- 1 is included below, with annual average taken from the C ALPUFF simulation

that used short

- term emission rates, included on the modeli ng DVD in the directories “ calpuff

discoverer

- st.epa ” and “ calpuff

- maersk

- st.epa ” . Recall that the short

- term CALPUFF modeling used point sources to represent the crew boats and OSVs, locating them at the end of the 25 na utical mile

line. Because the short

- term emission rates exceed the long

- term emission rates, this is a

conservative over

- estimate of the annual ly average concentrations, yet they do not exceed the

relevant SILs. Using the short

- term emission rates a voids the need to submit another modeling DVD.

By using point sources instead of volume sources, we effective ly side

- step the above concerns a b o ut

the initial plume height, sigma

- y

, and sigma

- z values. The only remaining volume source is used to characterize the relatively minor emissions from t he forklift and cement handling. A revised Table

6.2.3

- 4 follows.S tan Krivo

- 2

- J uly 12, 2013

Table 6.3.1

- 1

Maximum CALPUFF

- Predicted Class II Concentrations

Criteria

Pollutant Averaging

Period **Developer** Max.

Concentration (μg/m 3 ) **Discoverer Americas**

Max.

Concentration (μg/m 3 ) Modeling Significance

Level (μg/m 3 ) Monitoring

DeMinimus

Concentration (μg/m 3 )

NO 2 a 1

- hr 5. 7 7.3 7.5 c None c

Annual 0. 2 2 0. 28 1.0 14

PM 2.5 24

- hr b 0.08 0.1 0 1.2 d 4 d

Annual 0.00 61 0.00 69 0.3 d None

Notes:

a Annual NO X was assumed to be 75 percent converted to NO 2 , and use the short

- tem emission rates instead of the long

term emission rates

. One

- hour NO 2 model prediction based on the three year average of the maximum daily model

- predicted

1

- hour NO X concentration at each receptor location and 80 percent conversion to NO 2 (Tier II of EPA’s June 28, 2010 memo “Guidance Concerning the Implementation of the 1

- hour NO 2 NAAQS for the Prevention of Significant Deterioration Program.”

b 100 th percentile (ma ximum) values are presented (not 98 th percentile) using direct PM 2.5 emissions only.

c Interim SIL, established June 28, 2010 in the memo “Guidance Concerning the Implementation of the 1

- hour NO 2 NAAQS for the Prevention of Significant Deterioration Program”. The 1

- hour NO 2 Monitoring DeMinimus level has not yet been proposed.

d The PM 2.5 SILs and SMC were vacated on January 22, 2013,but presented here for comparison.



### - The reason the horizontal stacks in Table 6.2.3

- 3 do not have their exit velocities reduced as

in Table 6.2.3

- 2 should be provided.

A revised Table 6.2.3

- 3 is included below. Note that the CALPUFF modeling used the correct values of 0.001 m/s for all horizontal stacks, which can be verified in Block 13b of the files calpuff. year .inp. Table 6. 2. 3

- 4
Volume Source Stack Parameters for Miscellaneous Sources

Used in Visibility and Long

- Term CALPUFF Modeling Analysis

ID X

- UTM Y

- UTM Height (m) Elev (m) Sigma Y (m) Sigma Z (m)

MISC (a) 941.964

- 1186. 269 1.5 2.74 10 1.4

(a) MISC used to represent cement handling and the forklift, applicable only to the Discoverer AmericasS tan Krivo

- 3

- J uly 12, 2013

Table 6.2.3

- 3 **Support Vessel** Point Source Stack Parameters Used in CALPUFF Modeling Analysis

Stack Modeling

ID X

- Coord (LCC) Y

- Coord (LCC) Height (ft) Elev

. (ft) Diameter (ft) Exit Velocity

(ft/s) Exit Temp

( K ) Orientation

OSV (Main #1) OSV1 895.858

- 1186.624 57.04 0 1.33 157.32 718 Vertical

OSV (Main #2) OSV2 895.858

- 1186.624 57.04 0 1.33 157.32 718 Vertical

OSV (Main #3) OSV3 895.858

- 1186.624 57.04 0 1.33 157.32 718 Vertical

OSV (Main #4) OSV4 895.858

- 1186.624 57.04 0 1.33 157.32 718 Vertical Crewboats (Main #1) C1 895.858

- 1186.624 3.28 0 1.00 0.001 718 Horizontal Crewboats (Main #2) C2 895.858

- 1186.624 3.28 0 1.00 0.001 607 Horizontal Crewboats (Main #3) C3 895.858

- 1186.624 3.28 0 1.00 0.001 607 Horizontal Crewboats (Main #4) C4 895.858

- 1186.624 3.28 0 1.00 0.001 607 Horizontal

Crewboats (Generator #1) CG1 895.858

- 1186.624 3.28 0 0.33 0.001 6 10 Horizontal

Crewboats (Generator #2) CG2 895.858

- 1186.624 3.28 0 0.33 0.001 6 10 Horizontal



### - The application should explain why the stack height s provided in Table 6.2.3.

- 3 are lower than the average height of the support and crew boats provided in Table 6.2.3

- 4.

A s can be seen in the PDF diagrams of the Peyton Candies 1 and Sybil Graham 2 a vailable on the

Internet

, the support vess el’s exhaust is near the top of the pilot house, while the crew boat’s exhaust is about 1 meter above the water line (horizontal exhaust from the side of the vessel).

The modeling IDs VOL01 through VOL10 in Table 6.2.3

- 4 will no longer be relevant, b ecause the

CALPUFF model run used to assess annual average u se d point sources instead of volume sources

to charac terize the crew boats and OSVs.



### - The volume source input parameters provided in Table 6.2.3

- 4 do not appear appropriate because they do not agree with ENVIRON’s respo nse to our comments on the previous version of the application. The proper input parameters should be identified and explained.

- The average height of the offshore support vessels was given as 29.5 meters in a response to our initial review comments. Ba sed on suggested procedures for estimating Sigma z, this height yields a value of 13.7 meters.

- In another response to the previous review comments the actual heights were based on the ship diagrams yielding 18.0 and 7.6 meters or an average of 12.8 meter s. The heights based on ship diagrams appear more appropriate. This would yield a Sigma z

of 5.95 meters.

1 http://www.ottocandies.com/specs/peyton.pdf

2 http://www.grahamgulf.com/sybil_graham.htmS tan Krivo

- 4

- J uly 12, 2013



### - The support ships beam widths were indicated to be 18.3 and 10.4 meters. Following suggested procedures this would yield an average path width of 14.4 meters and a Sigma y of 6.7 meters.

- The volume height was set to the averaged heights of the crew and OSV boats. The application provided these heights as 5.39 and 33.42 meters but a response to our previous comments indicates these heights as plu me heights from SCREEN3 runs.

B ecause the CALPUFF run s used to evaluate annual average impacts compares to the annual SILs use point sources in stead of volume sources to represent the crew boats and OSVs, these

co mments are no longer relevant.



### Welding and Painting

– The revised application has included welding and painting as a new source of project emissions. The anticipated operational characteristics of these activities and

associated emission estimates shoul d be provided to support exclusion from the modeling analyses.

Please refer to the email from ENVIRON ’ s M ichael Carbon , dated April 25, 2013, to EPA. I include

the relevant sections here:



### Maersk Developer

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 campaig n. 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 calculatio ns 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 C FR 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. 3

Will any pa inting (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 partic ulate 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

bel ow. Detailed emission calculations and application forms that required updating are attached to

this email.

3 Included as an attachment to this e

- letter as well.S tan Krivo

- 5

- J uly 12, 2013

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



### Transocean Discoverer Americas

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 1 80

- 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. 4

Will any painting (spray or roller) activities be conducted during the d rilling 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 b rush/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.

MSD S 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 tha t 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 pe r 40 CFR 71.5(c)(11)(ii). There are no applicable regulations that would apply to the maintenance painting activities.

4 Included as an attachment to this e

- letter as well.S tan Krivo

- 6

- J uly 12, 2013

Table 2. Transocean Discoverer

– Painting Emissions

Pollutant Emissions (tpy)

PM10 0.2

PM2.5 0.1

VOC 1.5 Xylene 0.4

Please contac t me as soon as possible if you need further clarification

.

Sincerely,

Bart Brashers Atmospheric Scientist