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Related Links

Minnesota Department of Transportation (MNDOT)

Minnesota Helps

Twin Cities Red Cross

Maps

Map of Affected Roads (PDF)

Detail Map Around 35W Bridge (PDF)

Air Monitoring

Phase I - Air Quality Sampling Results

US Environmental Protection Agency contractors conducted Phase 1 of air quality sampling Aug. 10, 11, and 12. Samples were taken from seven locations surrounding the bridge site, with all samples taken before heavy demolition began to establish baseline air quality.  Samples were analyzed for asbestos, a set of metals including lead, particulates, and silicates. 

Analyses of these samples showed no unusual or health-threatening conditions during this baseline period with most of the results below the method detection limits, or in the case of volatile organic compounds (VOC) and total suspended particulates, within the expected range routinely see in the metro area. Minnesota Pollution Control Agency and Minnesota Department of Health are consulting with Minneapolis Environmental Management in review of data.

Phase 1 baseline air quality monitoring test results (done Aug. 10 – 12) (PDF)

Phase 2 – Air Quality Sampling

The review for the air sampling conducted August 27-31, 2007 during the initial phase of demolition on the I-35W Bridge has been completed. Samples indicated that the health impacts during this sampling period were minimal.

Monitoring site 1A - TSP mass was at or below normal concentrations for Minneapolis with the exception of the 178.45 µg/m3 recorded on the 8/27/07. This concentration was above the State ambient standard of 150 µg/m3. Activities at this site should be evaluated and corrective actions taken to minimize fugitive dust. Metals concentrations were generally below detection limits or levels of concern.

Monitoring site 2A and 3A - TSP mass was below the State ambient standard but above the normal range indicating demolition activities may have had some impact at this location. Activities at this site should be evaluated and corrective actions taken to minimize fugitive dust. Metals concentrations were generally below detection limits or levels of concern.

Monitoring site 4A, 6A and 7A - TSP mass was at or below the normal range for the 5-day sampling period. Metals concentrations were generally below detection limits or levels of concern.

Monitoring site 5A - TSP mass on 8/28/07 was 283.3 µg/m3 indicating significant impact from demolition activities on this day. This compared with a 24-hour value of 24 µg/m3 sampled on 8/28/07 at the MPCA site located in downtown Minneapolis. Mass for the other four days were at or slightly above the normal range indicating some impacts from demo activities. Metals concentrations were generally below detection limits or levels of concern. A detectable lead (Pb) concentration of 0.49 µg/m3 was reported on 8/28/07. Activities at this site should be evaluated and corrective actions taken to minimize fugitive dust.

In summary, demolition activities resulted in elevated TSP mass concentrations at monitoring sites 1A, 2A, 3A and 5A. Two of the 35 samples taken exceeded the State ambient air quality standard for TSP, but do not pose an immediate health risk. However, activities at this site should be evaluated and corrective actions taken to minimize fugitive dust. Results reported for sites 4A, 6A and 7A were at or below the normal TSP concentration range for ambient air in the Minneapolis area. Metals concentrations were generally below detection limits or levels of concern.