Westlake Center 2801 Post Oak Blvd. Suite 600 Houston, Texas 77056

Tel: 713/960

- 9111

April 20, 2011

VIA ELECTRONIC AND FIRST CLASS MAIL

Jodi Howard Environmental Engineer

U.S. EPA

- Office of Air Quality Planning and Standards Sector Policies and Program Divisions Coatings and Chemicals Group

Mail Code: E143

- 01 Research Triangle Park, NC 27711

Howard.Jodi@epamail.epa.gov

Re: PVC MACT Rulemaking

— Clarification of PVC Resin Concentration Data Supplementing Submissions in Response to EPA’s Section 114 Request

Dear Ms. Howard:

This letter is intended to cl arify the purpose of resin concentration data provided on behalf of Westlake Chemical Corporation (“Westlake”) in the concentration data spreadsheet submitted to the EPA on September 16, 2010, by The Vinyl Institute (“V I ”). The data in the spreadsheet con stitutes analytical results of polyvinyl chloride (PVC) resin sampling collected in response to the EPA ’s August 21, 2009 information collection request under the authority of Section 114 of the Clean Air Act (CAA) (hereinafter “114 Request”). The PVC res in sampling and analysis plans for the Westlake PVC facilities in Calvert City, KY and Geismar, LA were approved by the EPA on October 30, 2009 and sought to identify and quantify hazardous air pollutants (HAPs) from each of Westlake’s two PVC resin manufa cturing plants.

As described in each of our EPA

- approved Sampling and Analysis Plans, the resin analytical results (or concentrations) were used to calculate estimated quantitative mass emissions for HAPs and reported on

the EPA 30

- Day Resin Sampling Spre adsheets for Stripper and Dryer Outlets.

Upon reviewing the 114 Request data published on the EPA ’s website, it quickly became

apparent to The VI and Westlake that inconsistent methods had been used to convert the resin analytical

results into estimated ma ss emissions among the VI member companies. For example, we understand that some facilities used production volume from the entire plant to calculate the quantitative mass emissions while others used only the volume from the production lines being sampled . As the VI indicated in its September 16, 2010 submission, there were other inconsistencies in the emissions calculations stemming from the varying sampling and testing plans approved by the EPA . Accordingly,

Westlake submits that the concentration data submitted by VI in the spreadsheet is the actual measured data before the application of any mass calculations, and presents the most uniform, comparable, best and accurate data set from which to develop a maximum achievable control technology standard fo r the PVC and Copolymer production category.Jodi Howard

Environmental Engineer

U.S. EPA

- Office of Air Quality Planning and Standards April 20, 2011 Page Two

In closing, Westlake wishes again to emphasize that the spreads heet submission does not amend any data previously submitted to the EPA in response to its 114 Request. Rather

, it is the actual measured concentration data that formed the basis of the emissions estimate provided in the EPA 30

- Day Resin Sampling spreadsh eets. The resin sampling data from Westlake was developed in accordance with the approach set out in its EPA

- approved sampling plan, and it was not until the VI members examined this data collectively that the inconsistencies in reporting methodologies be came apparent.

Please do not hesitate to contact me if you have any questions or concerns via email at

kbloomer@westlake.com , or via telephone at 713

- 585

- 2946.

Sincerely

,

Kevin Bloomer

Sr. Environmental En gineer Westlake Chemical Corporation