Previous PreviousNext Next

EPA Home > Region 5 > Air > Correspondence


September 9, 1998

Dennis Drake, Chief
Air Quality Division
Department of Environmental Quality
P.O. Box 30260
Lansing, Michigan 48909-7760

Dear Mr. Drake:

Thank you for your timely submittal of the PM 2.5 Monitoring Network Design for Michigan. As you know, the deployment of
a PM 2.5 monitoring network is a critical component in the implementation of the PM 2.5 National Ambient Air Quality Standard (NAAQS). The ambient data from this network will drive an array of regulatory decisions, ranging from designating areas as attainment or nonattainment, to developing cost-effective control programs, and to tracking the progress of such programs.

Thank you also for your commitment to establish 34 PM 2.5 monitoring sites in Michigan by the end of Calendar Year 1999. I am pleased that of these, you intend to deploy 23 sites by the end of Calendar Year 1998. This is in accordance with the timetable for monitor deployment set up by Office of Air Quality Planning and Standards.

I am pleased that more than one half of your proposed PM 2.5 sites will be collocated with ozone monitors, and that several of your proposed PM 2.5 sites will be collocated with meteorologic monitoring. I am confident that ultimately these data will prove to be useful in establishing control strategies for both PM 2.5 and ozone.

I am also very pleased that you have considered international transboundary air issues in siting your PM 2.5 network. This is evidenced in your deployment of monitors at Port Huron and Sault Ste. Marie. Data collected at these sites will not only be useful for evaluation of local and regional air quality, but will also be available to support the United States / Canada Air Quality Agreement which ensures that data collected under both countries' programs are comparable and credible.

This is a middle scale source impact site. You have indicated that data from this site will not be used for comparison
to the PM 2.5 NAAQS. While the Environmental Protection Agency (EPA) has provided States with the flexibility to exempt SPM data from regulatory use for the first two complete calendar years of operation of the SPM, this site may be eligible for comparison to the 24-hour NAAQS.

I will approve this site to operate as an SPM for 1 calendar year. This site should be operated following all the guidelines for State and Local Air Monitoring Stations (SLAMS). By the time the first annual network review is conducted, additional guidance on use of data from SPM may be available. This will permit the Region to evaluate the eligibility of the data from this site for comparison to the 24-hour NAAQS.
# 26-163-0019

These are population-oriented neighborhood scale sites which you have identified as SPM. While the EPA has provided States with the flexibility to exempt SPM data from regulatory use for the first two complete calendar years of operation of the SPM, data from any monitoring site that satisfies all applicable 40 CFR Part 58 requirements and continues to collect data beyond this time frame would then be generally eligible for comparisons to the NAAQS.

I will approve the East 7 Mile, Southwest High School and River Rouge sites to operate as SPM for 1 calendar year. These sites should be operated following all the guidelines for SLAMS.


At the time the first annual network review is conducted, the Region will evaluate whether or not the sites should be upgraded to SLAMS.

After reviewing conceptual drawings for the proposed PM 2.5 site layouts, which were submitted by Tom Monosmith, of your staff, I also have some concerns about the general siting of PM 2.5 monitors in Michigan. I understand that the majority of your monitors will be located at ground level on a concrete slab. While ground level operation of monitors is likely to be safer and more convenient than operation on rooftops, I am concerned that your sites do not meet the access and security siting criteria described in Section 5.1 of the "Guidance for Network Design and Optimum Site Exposure for PM 2.5 and PM 10," 1997. This guidance suggests that sampler inlets should be sufficiently distant (greater than 10 meters) from public access in order to preclude purposeful contamination from reaching them in sufficient quantities, effectively biasing samples higher.

Your sample inlets will be less than 3 meters from public access, and because they are predominantly neighborhood scale population-oriented monitors that will not be located on rooftops, there is a significant possibility for contamination from local sources such as motor vehicle exhaust and cigarette smoke. I urge you to reconsider your decision to site monitors at ground level. While the recommendations of the guidance document are not regulatorily binding, the Region is not likely to exclude these data when making attainment designations.

As there are little historical PM 2.5 monitoring data available, this design represents a very good first attempt at what will be a dynamic process. As data are collected and as newer monitoring technologies become available, it may be useful or necessary to redefine the network so that it continues to provide information essential to describe ambient PM 2.5 concentrations as well as to assist in developing control strategies for PM 2.5. In addition, budget constraints and changes in implementation goals arising from the Agency’s response to the National Academy of Science’s review of the PM 2.5 NAAQS monitoring program may lead to reevaluation of monitoring strategies and ultimately to changes in network design.

I am pleased to conditionally approve your PM 2.5 monitoring network pending Regional site evaluations, and approval of the Fiscal Year 1999 budget. I am looking forward to receiving your annual revised PM 2.5 monitoring network description by July 1, 1999, as required by 40 CFR 58.26.

I appreciate your continued high level of commitment to the coordination of the PM 2.5 monitoring program in Michigan. I consider the implementation of the PM 2.5 network, as I’m sure you do, to be a critical priority.


If you have any questions or comments, please feel free to contact me or have your staff contact Maryann Suero, of my staff, at (312) 886-9077.

Sincerely yours,


Stephen Rothblatt, Acting Director
Air and Radiation Division

For further information, contact:
This Information Last Modified On: 09/18/2008 03:58 PM