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Dr. Thomas Cahill Responds to Bob Dunning

Nish-from-tracks
In a recent Enterprise column, "Pollution Doesn't Magically End at Olive Drive," Bob Dunning  asks:

…if this is truly all about ultra-fine metals from brakes on trains, why aren’t these same folks sounding the alarm about all the other areas in town that are similarly at risk?

In response, Dr. Thomas Cahill, UC Davis Professor of Physics and Atmospheric Sciences and founder of the DELTA Group (Detection and Evaluation of Long-range Transport of Aerosols), sent us the following information and asked us to publish it.

Freeways have limited impacts downwind, and in most cases, freeway influence has dropped to 10% in 500 feet. The key factors are:

  1. Traffic volume and truck fraction
  2. Freeway configuration and distance to 10% impact
    1. Flat  (all of I-80 in Davis) – the normal 500 ft margin for freeway impact
    2. Depressed (113 through Davis)  – the best for impacts: 200 ft.
    3. Elevated on berm (UPRR overcrossing adjacent to Nishi) – bad, with impacts beyond 1,000 ft
  3. Upwind versus downwind
    1. Upwind usually under 150 ft to 10%
  4. Traffic pattern
    1. Freely flowing freeways -> surprisingly little pollution.
    2. Accelerating from slow to high speed -> heavy diesel exhaust from trucks (Nishi south)
    3. Braking from high speed to slow -> ultra fine metals (Nishi I-80 over crossing)

The Nishi property exhibits the worst case for all four key factors.

 The following shows the Nishi risk in comparison to a UC Davis student living in Davis:

Davis-air quality comparison

I-80 Nishi elevated

Scaling

Neo- natal

Loss of lung capacity

Number

%

Cars ng/m3

Trucks ng/m3

Cars %

Trucks %

Cars, trucks

137,000 12,000

146%

17%

990

0.4%

        

Braking hrs

2

        

30

42

14%

20%

Distance to dorms

900 ft

130%

15%

880

0.4%

27

37

12%

18%

Sum

 

130%

15%

880

0.4%

27

37

12%

18%

Note: Neo-natal is so high because the impact can occur in just a few months of residence.

Note: Without local traffic data, these are at best semi-quantitative estimates based on personal experience.

  1. West campus:                     > 20 x better than Nishi, best air in Davis
  2. Orchard Park:                    10 x  better than Nishi
  3. Solano Park:                        ??    better than Nishi, and there is mitigation from mature trees, but given families & long residence times, measurements are needed plus better filters
  4. Near University Mall:         9 x  better than Nishi
  5. L street complexes:            18 x  better than Nishi
  6. Lincoln 40 proposal:          8  x  better than Nishi
  7. Westwood Village:              18 x  better than Nishi
  8. Near Marketplace:              9 x  better than Nishi
  9. South Davis:                         18 x  better than Nishi

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Comments

3 responses to “Dr. Thomas Cahill Responds to Bob Dunning”

  1. John Troidl

    The best, cleanest air is on West Campus?? Well, let me ask a stupid question: Why doesn’t the University build (more) student housing at that location? Make residential sites that are interesting, accessible, educational, and safe. BTW, “accessible” means NO NEED FOR STUDENT TO HAVE THE EXPENSE AND INCONVENIENCE OF OWNING AND OPERATING A CAR. REGARDING “safe”… why would the University want to stick students out by the highway?

    Reply
  2. Bill Wagman

    I find it interesting that no results are listed here for the east side of Olive Drive.

    Reply
  3. Tom Cahill

    Bill, there are several reasons for the absence. I did this report for Matt Dulcinich at UCD and focused on UCD sites. Only at the end did I add others. For example, I had good data from a prior study south of I-80 near El Macero, as well as in Davis west of 113. I have nothing on Olive Drive east. Olive Drive west was a disaster in the EIR because trucks are accelerating 400 ft south of the site, but by east Olive, traffic is running more smoothly. Then there are trees, ect. I did downgrade the Lincoln 40 site because of heavy braking on Richards Blvd, but I am not sure how far that travels east with all the trees and buildings. Sorry I can’t help more.
    Tom

    Reply

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