From: Krivo, Stan

Sent: Wednesday, July 31, 2013 3:34 PM

To: Shepherd, Lorinda

Subject: FW: Statoil EGOM PSD Application: Revised Air Quality Impact Assessment

Follow Up Flag: Follow up

Flag Status: Flagged

Statoil records

From: Bart Brashers [mailto:bbrashers@environcorp.com] 

Sent: Thursday, July 11, 2013 3:31 PM

To: Krivo, Stan

Cc: Shepherd, Lorinda; Kyle Heitkamp; Michael Carbon

Subject: RE: Statoil EGOM PSD Application: Revised Air Quality Impact Assessment

Stan,

See in-line below for my responses. Please take a moment to parse this, and let me know as soon as 

possible if any of my responses are insufficient. I will respond more formally tomorrow, but I 

understand you’ll be out of the office tomorrow, and I would very much like to see this process move 

along quickly.

Would it be faster to use the annual average values from the short-term modeling, which you already 

have on the modeling DVD? Even though the annual emissions are much smaller than the short-term 

emissions, both the NOx and PM2.5 annual average are below their respective SILs.

Please let me know if we can get this finished today.

Bart

From: Krivo, Stan [mailto:Krivo.Stanley@epa.gov] 

Sent: Thursday, July 11, 2013 11:14 AM

To: Bart Brashers

Cc: Shepherd, Lorinda

Subject: RE: Statoil EGOM PSD Application: Revised Air Quality Impact Assessment

Bart, 

This is a follow up to today’s telephone discussion concerning the revised air quality modeling 

section of the application. The revised application is in response to our review comments on 

the previous version of the application that addressed issues with the method and procedures 

used to model the support vessels as a volume line source. The following provides the 

remaining concerns with the revised modeling section.

Revised Section 6 - Air Quality Impact Assessment (June 2013) 
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 shortterm 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 crew 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.

In the interest of time, we will side-step the whole volume source issue by assuming the crew and other 

support vessels are located at the end of the 25 nautical mile line, the same location as in the revised 

short-term modeling. We will model them as points sources. Modeling is underway, I will have results 

for you later today.

- 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.

The table should be corrected. The CALPUFF modeling was done correctly, however, as can be seen for 

example for the source C1:

! SRCNAM = C1 !

! X = 895.858,-1186.624,1.00,0,0.30,0.001,607.04,0,2.46E-03,0,2.68E+00,0,0,0,0,0,5.95E-02 !

The 6th element of the line is the stack velocity, with a value of 0.001 m/s.

- The application should explain why the stack heights 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. 

If you inspect the PDF diagrams of the Peyton Candies and Sybil Graham I sent previously, also available 

at http://www.ottocandies.com/specs/peyton.pdf and http://www.grahamgulf.com/sybil_graham.htm, 

you can see that the support vessel’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, now that we’ve 

converted the annual modeling to point sources.

- The volume source input parameters provided in Table 6.2.3-4 do not appear appropriate 

because they do not agree with ENVIRON’s response 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. Based 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 meters. The heights 

based on ship diagrams appear more appropriate. This would yield a Sigma z of 5.95 

meters.

- 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 plume heights from SCREEN3 runs.

This comment will no longer be relevant, now that we’ve switched to point sources for the annual 

modeling.

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 should be provided to support exclusion from the modeling 

analyses.

See my previous response. Were you able to find the information in the docket?

Please let me know of any questions. 

Thanks...sjk

From: Bart Brashers [mailto:bbrashers@environcorp.com] 

Sent: Thursday, June 27, 2013 4:40 PM

To: Krivo, Stan; Shepherd, Lorinda; Jill Webster (Jill_Webster@fws.gov)

Cc: Donald Evans; Michael Carbon; Brian Glover; Kyle Heitkamp

Subject: Statoil EGOM PSD Application: Revised Air Quality Impact Assessment

Stan,

Enclosed please find an revised Air Quality Impact Assessment that reflects the changes to the Statoil 

PSD Application, as per our recent discussions. It refers to the PM2.5 Assessment that you’ve seen 

before, which is also enclosed. I trust that this version of the assessment will allow the application 

process to proceed. A revised modeling DVD will be sent under separate cover to you today.

Jill,

The portions of the enclosed Air Quality Impact Assessment that pertain to Class I Area visibility 

degradation and deposition have not changed since last you saw it, but I wanted to make sure you had a 

chance to comments on the final version.
Bart

Bart Brashers | Atmospheric Scientist

Senior Manager, ENVIRON International Corporation

19020 33rd Ave W Ste 310 | Lynnwood WA 98036

T: +1 425-412-1812 | F: +1 425-412-1840 | M: +1 206-550-2606

bbrashers@environcorp.com

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