Minnesota Department of Transportation

511 Travel Info

Bridges and Structures

Design, construction and maintenance resources

Do It Right! Lessons from the field not to be repeated


  • If the blistered finish is due to blasting media being trapped in the paint because of incomplete blowdown of the work area — or of gassing bubbles trapped in a much too thick layer of primer — it makes no difference to us:
  • The Contractor has to screen it and repaint it
  • Another good reason to clean up the floor of the containment everyday— you don’t want to let the river clean it off for you!
  • If windy conditions are forecast while you
    have the containment up, make sure to
    “batten the hatches,” and get all the loose
    ends tied up, clamps on the fabric corners,
    the blasting media cleaned completely and the jobsite secured!
  • Even though our Special Provisions call for the enclosure to “minimize the escape of blasting residue during adverse weather conditions,” this is another reason they also call for the contractor to:

“Collect all abrasive blasting waste from inside and outside the containment area at the end of each workday.”

  • This is flash‐rust on freshly blasted surfaces, this will have to be blasted off and blown down before we can allow the painters to paint inside this containment area.
  • They may need to setup a dehumidifier inside the containment to prevent this.

When you're removing paint from a bridge . . .

  • Make sure the holes in the floor of containment have been plugged prior to blasting!
  • I’m thinking probably none of the
    lead paint chips fell into the river?
  • Bottom flange of the end diaphragm unpainted!
  • Looks like they got more paint on the concrete back wall than on the bottom flange!
  • It’s hard to believe, but even the professionals can miss a small spot here and there!
  • The specs call for the paint to be applied in an:

“Even wet coat, free of runs, drips and sags.”

  • When checking the paint job, make sure to do some walking around on your own.
  • The painters may not be looking from the same angle as you.
  • Here are some areas that were missed because they didn’t spray from the lower right side.
  • We’re not looking for a textured surface with the paint system on the steel beams.
  • These aren’t sand dunes or ripples on a
    stream bottom.
  • These are paint ripples on the bottom flange of a beam!