Monday, August 18, 2008

Measured Improvement? Times analysis of carbon monoxide may exceed AY FEIS estimates

Would you want to run a marathon around the Atlantic Yards footprint?

An informational graphic (click to enlarge) in the New York Times Sports section Saturday suggested some curious details about the Atlantic Yards footprint and nearby parts of central Brooklyn: the area is experiencing high levels of carbon monoxide (CO) emissions, close to the levels that prompted Beijing officials to take drastic pre-marathon measures.

The main point of the graphic is to compare the air quality along the Olympic marathon route in Beijing before alternate-day driving restrictions were imposed with the air quality after such limitations were imposed.

The newspaper also included a graphic of the New York City Marathon route, which showed a "spike" in the area near Lafayette and Bedford avenues, where the route turns north,
but also some significant increases around the intersection of Fourth, Flatbush, and Atlantic avenues, the western segment of the AY footprint.

The newspaper blames "construction machinery" for the increase, at least in the area closer to Bedford Avenue. There's also a significant amount of construction equipment operating in and around the footprint, as with the excavator pictured on Dean Street near Sixth Avenue.

So, as I describe below, there's an argument for measuring carbon monoxide even though it's not part of the Community Air Monitoring Plan for the construction phase of the project.

Looking at the numbers

The Times graphic suggests that the area around Fourth, Flatbush, and Atlantic avenues experiences well over 5 ppm (parts per million), and possibly as large as 10 ppm, or even larger. Still, without backing data, it's not easy to eyeball the graphic and determine a total.

By contrast, Chapter 17 (Construction Impacts) of the Final Environmental Impact Statement (FEIS) estimates that the combination of construction equipment and traffic would not raise CO above the 9 ppm threshold set by the Environmental Protection Agency in its National Ambient Air Quality Standards (NAAQS).

Note that the EPA states that the 9 ppm level should not be exceeded more than once per year. (The maximum permitted one-hour concentration is 35 ppm.) Also note that that level is an 8-hour average, and the Times didn't state whether its totals represent such an average or simply the average of one-time readings along the route.

(What's wrong with CO? Chapter 14 (Air Quality) of the FEIS explains: CO, a colorless and odorless gas, is produced in the urban environment primarily by the incomplete combustion of gasoline and other fossil fuels. In urban areas, approximately 80 to 90 percent of CO emissions are from motor vehicles. Since CO is a reactive gas that does not persist in the atmosphere, CO concentrations can vary greatly over relatively short distances. Elevated concentrations are usually limited to locations near crowded intersections, heavily traveled and congested roadways, parking lots, and garages. Consequently, CO concentrations must be predicted on a local, or microscale, basis.)

More CO coming, likely

The Construction Impacts chapter in the FEIS notes:
CO emissions... generally would also be highest during periods when the most activity would occur.

It's fair to say "most activity" has yet to occur. That's an argument for further monitoring, especially since the Community Air Monitoring Plan for the construction phase of the project focuses solely on particulates and volatile organic compounds, not carbon monoxide.

From Chapter 17:
Maximum predicted combined concentration increments from on-site construction and mobile sources during Phase I, and overall combined concentrations including background concentrations, are presented in Table 17b-6 and Table 17b-7, respectively... The cumulative increments presented in Table 17b-6 are a sum of the Phase I construction on-site increments from Table 17b-4 and the maximum construction related mobile-source increments from the mobile source site closest to the location of the maximum on-site increments.

Conclusion: no problem

Chapter 17 states:
In terms of the magnitude of air quality impacts, any action predicted to increase the concentration of a criteria air pollutant to a level that would exceed the NAAQS... would be deemed to have a potential significant adverse impact. See Chapter 14, “Air Quality,” for a full discussion of the standards and impact criteria.

Most of the section on air quality concerns particulate matter rather than carbon monoxide. A few very selective excerpts from the chapter's conclusions:
Concentrations of CO, NO2, and PM10 were not predicted to be significantly impacted by the construction of the proposed project in any phase of construction...

Under SEQRA, determination of the significance of impacts is based on the assessment of the predicted impacts based on their intensity, duration, geographic extent, reversibility, and the number of people that would be affected by the predicted impacts...

For these reasons, no significant adverse impacts on air quality are predicted during the construction of the proposed project.

From Chapter 14

Chapter 14, Air Quality, deals with effects from the project as built, rather than from construction impacts. The conclusion:
CO, PM10, and PM2.5 concentrations due to project-generated traffic would not result in any violations of National Ambient Air Quality Standards (NAAQS) or any significant adverse air quality impacts. It was also determined that CO impacts would not exceed CEQR [City Environmental Quality Review] de minimis criteria...

And what are those criteria? Chapter 14 explains:
Significant increases of CO concentrations in New York City are defined as: (1) an increase of 0.5 parts per million (ppm) or more in the maximum 8-hour average CO concentration at a location where the predicted No Build 8-hour concentration is equal to or between 8 and 9 ppm; or (2) an increase of more than one half the difference between baseline (i.e., No Build) concentrations and the 8-hour standard (9 ppm), when No Build concentrations are below 8.0 ppm.

You can see that neither of those criteria are met. You can also see that, for some reason, the FEIS, issued in November 2006, contained "maximum predicted existing 8-hour average CO concentrations for 2005," which seems odd, given that 2005 statistics could have been monitored rather than predicted.
(Emphases added)

Note that, while graphics shown on this blog concern conditions in 2010, the predicted end of the first phase of the project, the FEIS also contains charts estimating conditions in 2016, the predicted (though highly unlikely) conclusion of the project.

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