Traditionally, bridge ties have presented a challenge for pressure treaters. Closing a bridge for tie replacement can affect several different lines that use the same bridge, which means major cost for the railroads.  So, when a bridge is scheduled for bridge tie replacement, those ties must be ordered and delivered very quickly. As a result, bridge ties are not air-dried and usually have to be treated while still green. Green ties are difficult to treat and are often over-treated, potentially leading to drippage and bleeding.

Because bridge ties cannot be dip-treated with Cellu-Treat and air-dried, Nisus developed the BTX system. This allows the addition of Cellu-Treat borate to the heartwood of green bridge ties so railroads can take advantage of all the benefits of dual treatment in the Bridge Tie Program.

During the Boulton cycle, borate is drawn into the heartwood of the tie, providing long-term residual protection from internal decay.