Hartland Covered Bridge project: Deck rehabilitation steps

The world’s longest covered bridge, the Hartland Covered Bridge, in New Brunswick, Canada, is undergoing the most extensive rehabilitation in its 107-year history. An epoxy polymer overlay from Unitex Chemicals — Unitex Pro-Poxy Type III DOT — is being used to repair the bridge deck.

The New Brunswick Department of Transportation is doing all of the repairs. In all, the deck repairs used 1,650 gallons of Type III DOT epoxy polymer overlay; 119,000 foot- board-measure of decking lumber; and 6,000 pounds of nails.

The deck repairs include the following steps:

1. Five of the seven deck spans were removed, one span at a time (two spans were repaired several years ago).  The spans measure 16-feet-wide by either 150 or 175-feet-long. The deck consisted of asphalt over timbers, which had been treated with coal tar creosote.

2. New timbers – Wolmanized-brand timbers -- treated with a copper-based preservative and fungicide -- were laid. The timbers are 7 inches wide by 1 ¾ inches thick, with lengths of 12, 14 or 16 feet. They were placed on edge, laid side by side, and nailed down.

3. The crews roughened the new timber surface with a very light sandblasting to help the Unitex Pro-Poxy Type III DOT epoxy adhere better.

4. The crews mixed the Unitex epoxy on-site in large plastic tubs using a drill with a “Jiffy mixer.” The epoxy was mixed at about 300 revolutions per minute for exactly three minutes.