Air Quality Discussion

This discussion was led by Keith Latham of Sempra.  Other Sempra folks and the audience participated as well.  Notable items I picked out of this discussion included: [You know - the talking portion sure seemed longer last night, but I believe this is the gist of what was said.  The rest came through the repeated asking of similar questions and answers.  Please let me know if I missed anything major in this section]

• One of the major concerns expressed by the community at the meeting in May and in subsequent discussions has been the lack of air quality data here in Adamstown.  We recognize that and are committed to working with you to determine the best way to gather the information you need, and work together to see if we can make it happen. [Here's a link (takes you further down the page) to what I believe is required to allay our fears]

• The regulatory process includes the requirement for the use of data modeling to simulate various processes at the plant.  One of these models is emissions modeling.  Sempra's consultant modeled / simulated plant output and dispersion using 5 years of meteorological data from the area.  A significant amount of data was developed at 36 equi-radial paths away from the site.  Data points started every 50 meters and expanded outward in some cases to distances of 150 miles.  This modeling showed that most of the impact was on the site itself, and the rest was below the levels that are deemed to be significant by regulation.

• Since the dispersion modeling showed that there was an insignificant impact on ambient air quality, additional modeling taking into account additional sources (like EastAlco, Essroc, etc) was not required. [This statement was consistent with page 7 of the testimony of Robert C. McCann, Jr.]

• No local air quality monitoring was required because the modeling and performed showed an impact below the threshold required for local air monitoring.  [Again consistent with page 9 of the testimony of Robert C. McCann, Jr.]

• Since Frederick County has been designated as Non-attainment for ozone, the plant is subject to Non-Attainment New Source Review.  This means there are stricter limits on the emissions of NOx and VOC that must be met by the plant, and that they must purchase emission offsets at a rate of 1.3 to 1 for these emissions. 

• The plant's emissions will be less than or equal to all permitted amounts. 

• Thanks to the plume abatement planned for the facility, the plume from the stacks will not be visible most of the time.  In fact, they expect that we should only see a small plume for a few hours on some winter days.

[The following question and answer from Mr. McCann's testimony seems to sum up the Sempra stance on the air quality impact that the Catoctin plant will have on the area:

Q. What is your conclusion regarding the Project’s potential impacts to air quality in nearby communities?

A:  The Project’s potential impacts to air quality in nearby communities are expected to be minimal and even lower than the maximum (but still insignificant) impacts reported in the Application.  The maximum Project impacts were predicted to occur near the Project site.  In nearby communities, the Project’s impacts are expected to be at least an order of magnitude lower than the reported maximum values and far below the Ambient Air Quality Standards that are designed to protect health and welfare.]

Questions and Answers [These are not anywhere near verbatim, they are what I remember as being the essence of the questions..]

Question: [This first question was asked a number of different ways, and a number of different times, but the essence was the same each time.]  What is the air quality here in Adamstown?  If we do not know what our current air quality is, how can we - the local residents with children in this school - assess what the impact will be.  You say it will be negligible, worst case ~ 1%, but what if that 1% takes us from 100% of the EPA guideline to 101%?  We need to know so we can all have some basis for our levels of comfort or discomfort.
Answer: That is a good question to which we do not have an answer.  To this point we have been focused on fulfilling all of the regulatory requirements for the permitting process.  Under those procedures, local area quality testing is not required.  We used data from Dulles and local meteorological data in our models of emissions that the plant is expected to produce and the associated dispersal patterns, but did not do local testing.  That being said, as was stated previously, we believe it is in our best interest to pursue a way to get you the information you want to see.  The details of how that might be accomplished still need to be worked out.

Question: How does the process of purchasing offsets work?
Answer: Let's use an example.  Say I am producing 1000 pounds of NOx.  The regulations require me to find someone who is no longer producing - or is willing not to produce 1,300 pounds of NOx and purchase that capability from them.  That then lowers their permitted amount by 1,300 and they are then never allowed move it back up.  This has the net effect of lowering the maximum permitted emissions between the 2 facilities by 300 pounds. 

Question: Where will you purchase these offset credits?
Answer: While there is a large geographical area from which we can purchase the credits, we are working toward purchasing credits in the local area and have identified a couple of potential sources.

Question: What are the geographical restrictions on the purchase of the credits?
Answer: We will get back to you with that information.

Question: What kind of plume will we see on a normal day?
Answer: You should not see any plume on a normal day.  Due to the plume abatement (and the exact details are subject to the final equipment choice) you should only see a 30-40 foot plume a few hours on some days in the winter.  Basically the types of days when you see fog over the water.

Question: What was the worst case data you used for the model?
Answer: We did not use a single set of data.  The model is more like a simulation. We fed in 5 years worth of local meteorological data to simulate real conditions and this is what generated the data points.

Question: Did you develop a graphic overlay of the emission dispersion data on the local area?  This would be helpful in visualizing the impact (once we have local air quality data as a starting point).
Answer: We can develop that graphic and we will get back to you with more information.

Local Air Quality Monitoring

02/18/2006 08:24 AM