by Mike Fernandez

Stayton, Oregon - June 2002 - The James W. Fowler Company (JWF) of Dallas, Oregon has been working on an extremely challenging project that involves trenching across two sections of the North Santiam River. The project is part of the City of Salem’s $6 million 75 MGD Transmission Conduits Phase 1 Project on Geren Island. The purpose of the project is to increase the quantity of potable water that is sent to Salem’s water distribution system. JWF was awarded the job of installing 4,100 linear feet of parallel 69-inch welded steel pipe in 40-foot joints (approx. 8,200 feet total), concrete flowmeters, chemical feed vaults, pressure sensors, valves, and appurtenances. The project was started on June 1, 2002 and is scheduled for completion by May 31, 2003.

Site Conditions

Project specs called for the pipeline to run at depths varying from 16 to over 20 feet in sand and cobbles with a free flowing water table at 6 feet below the existing grade that would require continuous dewatering. Large diameter river rock clogs the North Santiam making sheet piling the river crossing an unacceptable option. The pipeline also runs adjacent to existing fluoridation and disinfection buildings. Vibration during the installation process also poses a risk of structural damage to the surrounding buildings. Good solutions were necessary.

Recognizing the consequences of excavating under the difficult circumstances, JWF evaluated the project specs and then researched their trench shoring options. They joined forces with supplier D.P. Nicoli (DPN) of Tualatin, Oregon and chose to rent DPN’s Efficiency Production Slide Rail System. The Slide Rail offered the added benefit of simultaneously installing the shoring system while excavating the trench. This would save time and money since the river crossings had to be done at constrained durations. Also due to the precise dimensions and the structural stability of the Slide Rail JWF would be able to use the system as a concrete form for pouring the encasement. "We felt that the river crossings were a good match for an active shoring system," stated JWF project manager Mark Weisensee, "It also eliminated the extra step of sheet piling."

River Crossing

Forty-five days were planned to complete the crossings, so JWF has had to use their equipment efficiently and work extended shifts to accommodate the accelerated schedule. JWF is using a Komatsu PC1000, a PC650, and various smaller excavators along with CAT 950 Loaders for the excavation and installation of the shoring system and pipeline.

The Slide Rail system is being used in an eight bay linear configuration. Each bay is 12-feet long and 18-feet wide making for a combined linear shoring structure measuring 105-feet with posts! All 8 bays are installed with sacrificial beams at the bottoms. Then horizontal walers are installed so 3 bays could be opened at a time, resulting in over 38-feet of clear opening with no spreaders! Then the parallel 40-foot pipe sections are positioned at depths of 16 to 20-feet. After securing the pipes the spreaders are reinstalled, and the horizontal walers are removed. As the pipeline installation progresses the panels, posts, walers, and spreaders that comprise each bay are pulled out concurrently while backfilling the trench. Each bay is then "leap-frogged" ahead in the trench and the excavation continues. Efficiency Production’s Slide Rail Field Installer, Troy Serrels, was on hand to assist first time Slide Rail user JWF with the preliminary setup of the system. The crew worked proficiently once they became familiar with the system and expects to finish on time! Weisensee commented on the advantages of the system, "We feel that in the cobbly material on this project the Slide Rail saved us money. " He added, "The river crossing work was difficult to plan and allocate resources for but through research we learned about the Slide Rail and we are able to minimize the potential risks." The Slide Rail also offers other benefits such as increased worker safety, and less excavation and restoration since sloping is unnecessary.

On Site Personnel

The Geren Island project’s on site personnel includes JWF’s Superintendents Tom Pierce and Kevin Orton, Project Manager Mark Weisensee, Crew Foremen Jim Batson and Lloyd Dow, Engineer Jim Schnurr from Black & Veatch, City of Salem’s Construction Manager Sandra Olds, Bruce Ellis of D.P. Nicoli, and Efficiency Production’s Slide Rail Field Installer Troy Serrels.

The James W. Fowler Company has been in business since 1970 as a heavy highway contractor. They began working on treatment plants in 1988 and commercial building projects in 1992. JWF specializes in difficult utility projects and tunneling.