Photo by Greg Crews, AECOM

Richland-Chambers Pipeline Lowering

The existing 90-in.-dia pipeline had to be lowered to accommodate future construction and operation of a 108-in. raw water pipeline. The work had to be done in no more than 45 days, which was the longest TRWD could shut down the pipeline and maintain contracted service to customers. The contractor proposed a 38-day operation and delivered the project seven days early, roughly $260,000 under the guaranteed maximum price.

One key was the owner's decision to prepurchase all pipe material. With design completed more than one year before the scheduled start of work, there was enough time for manufacturing the pipe before construction to eliminate the risk of manufacturing and delivery delays.

The North Texas winter of 2014 included several snowfalls and extended periods below freezing. With the pipeline encased in low strength concrete, operations had to be stopped on several occasions because material could not be provided within specifications at the batch plant.

Another challenge occurred when the connection point between the existing and proposed pipe was not where the design identified it. To solve the problem, the team decided to use steel pipe, which is more adaptable when field conditions vary, compared with prestressed concrete cylinder pipe. The proposed connection point was found to be roughly 6 ft off from the design location, so the team coordinated adjustments of a 90-in. by 78-in. tee location with the engineer and TRWD, then made a small field adjustment to one stick of pipe.

Key Players

General Contractor Garney Construction, Kansas City, Mo.

Owner Tarrant Regional Water District, Fort Worth, Texas

Lead Design Lockwood, Andrews & Newnam Inc., Fort Worth