by Mike Fernandez

Washington, D.C. - 1/2001 - The 2001 construction market is predicted to remain strong even among concerns of an economic slowdown. Significant increases in the utility and transportation segments are expected as State and Federal legislation such as the TEA-21 (Transportation Equity Act for the 21^st Century), the Safe Drinking Water Act, and Clean Water initiatives provide funding for revitalizing the aging metropolitan infrastructure and expanding it to meet the demands of the growing population and emerging business communities. Many States also have programs for the improvement and expansion of roads, transit systems, drainage systems, and utilities. The Environmental Protection Agency has estimated that more than $330 billion dollars will be needed for the construction and rehabilitation of America’s sewer pipelines over the next 20 years. An increase in land development, fueled by the incentives of the record-breaking economy of 2000, has intensified the need to expand utility and transportation services to outlying areas. The tremendous growth of the communication technology industry and the proliferation of web-based services have also created a demand to upgrade and expand the network of underground digital communication lines.

These legislative initiatives and the increased demand for services are positive indicators of continued economic prosperity in the construction industry. But, the monumental task of rehabilitating and expanding the infrastructure is complicated. The necessary work will take place in increasingly congested areas and confined spaces using smaller excavating equipment. This work will call for the continued development of standardized and interchangeable trench shielding systems that can be combined to handle multiple tasks such as shoring around numerous existing utilities, providing protection for adjacent structures, and securing larger excavated working areas unobstructed by shoring system cross members.

This type of trench shielding system has been developed by Efficiency Production, Inc. It has gained popularity as more contractors are finding it essential for meeting the challenges of their underground projects. Since it is a modular unit the system can be configured to meet a wide range of specific job requirements and yet remain available as a rental unit. The system also provides the added value of higher equipment utilization for a greater variety of job applications.

Efficiency’s system consists of Shore-Trak^TM panels measuring 22 ^1/2 inches wide and up to 24 feet long that slide through guide frames and can be pinned in place above cross trench utilities. The guide frames connect to Slide Rail posts where utilities are located. Then Slide Rail panels are inserted into linear or corner posts and are pushed to grade. An innovative Parallel Beam design eliminates post deflection during installation and removal and facilitates the vertical movement of spreaders or arches. Internal walers can be incorporated for larger unobstructed 4-sided pits. Optional bolt-on collars are also available for using Slide Rail panels with spreaders as standard trench shields for other jobs.

Efficiency’s system has been used on several projects within the last year. Seattle City Light used it to install adjoining utility vaults at a substation across the street from the Space Needle in Downtown Seattle (published in Pacific Builder & Engineer, Mar. 2000). A clear span excavation of 22 x 24 feet wide x 16 feet deep was needed for the vaults. Eight active power ducts crossed the excavation, and a 70-foot power pole supporting a 120, 000-volt line was standing at the edge of the pit. City Light used Shore-Trak panels on two sides to shield around the crossing ducts. Slide Rail panels were then installed to shield the remaining walls. Vibration was kept to a minimum and the ducts, the power pole, nor the Space Needle were compromised during this project!

In another project in Denver, Colorado prime contractors Colorado Jaynes Natkin Co. and subcontractor Mayer, Lemke, and Landsiedel General Contractors installed the water, sewer, electrical, telephone, fiber optic, and steam line systems outside of a new research facility (published in Rocky Mountain Construction, May 2000). The project consisted of transforming the aging underground infrastructure of an Army Hospital into one that would support the University of Colorado’s state-of-the-art Health Science Center and incorporate it into the city’s system.

Their forming crews required minimum clear span excavations of 29 x 29 feet in width x 20 feet deep to install 8 poured-in-place concrete steam vaults in the type "C" soil. Surrounding buildings and roads complicated the installation process. Utility’s ranging from 18 to 24 inches in diameter paralleled 3 sides of the excavation extending from 6 to 18 inches outside of the system and ranging 7 to 16 feet in depth. An 8^1/2 foot square live steam tunnel ran diagonally through one corner of the excavation. A 48-inch manhole structure lying within inches of a corner added to the challenge. The Slide Rail / Shore-Trak combination system was installed and the crews were able to successfully maintain clearance and soil stability around the existing steam tunnel!

Presently, the M.B. Kahn Construction Company’s Moore Division of Greenwood, South Carolina has implemented Efficiency’s Slide Rail / Shore-Trak system to shore pits adjacent to a factory. The $1.2 million Design-Build project to provide water storage for a Carrollton, GA. industrial plant includes the installation of a 4 million gallon above ground water tank, pipe re-routing, 5 pump stations, and the electrical and control boxes.

One of the pump station pits presented a significant challenge. The installation was to take place at the foundation of the factory wall in a low area that catches water runoff. Limited space ruled out sloping as an option. The soil consisted of clay, sand, and "muck". A 48-inch diameter round corrugated metal storm drain ran diagonally across the 24-foot wide by 24-foot long excavation, and an 8-inch steel high pressure oil line ran parallel to the pit within inches of the outside edge of the cut. To further complicate the installation eight inches of rain fell during the excavation process filling the 16-foot deep pit with over five feet of water.

The crew had a dewatering pump running as the excavation and installation of the Slide Rail / Shore-Trak system progressed. Shore-Trak guide frames were set on the two sides where the drainpipe crossed. Due to the size of the pump station one of the guide frames had to be precisely positioned right next to the oil line! Since Efficiency’s Shore-Trak and Slide Rail systems are compatible, the Shore-Trak guide frames were easily connected to the Slide Rail corner posts to complete the square configuration. At this time the 8-foot high by 24-foot long Slide Rail panels were set into the corner posts to shore the two remaining walls of the excavation. Then some of the 22 ^1/2 inch wide by 20-foot long Shore-Trak panels were inserted into the guide frames to begin shoring around the 48-inch diameter storm drain. The crew used a Kobelco 300 to continue digging, positioning panels, and pushing the system to grade simultaneously. A Bobcat mini excavator was dropped inside of the system to dig under the pipe in order to place the final Shore-Trak panels in the corner behind the pipe (refer to photo). At this point the shielding system was successfully installed to grade and the excavation was ready for the forms to be set.

M.B. Kahn’s Project Superintendent, Charles Teague said Efficiency’s shielding system was helping to complete the job quicker, saving time and money. He stated, "The system is very critical to getting the pump station excavated and poured." Project Manager Chris Burch was also "very impressed". He explained his experience with Efficiency’s system, "I can't say enough about the product. We pride ourselves in providing solid solutions for tough conditions. In Carrollton, with eight inches of rain and at times over five feet of water in our excavation, we had tough conditions. The combination Slide-Rail / Shore-Trak system allowed us the opportunity to provide a safe excavation for our employees. Jobsite safety is paramount and having Efficiency engineer this system with the unknowns we encountered, as well as the guidance from Efficiency’s installation team of Doug Austin and Troy Serrels onsite, I felt very comfortable with the excavation. They demonstrated excellent knowledge of the system and worked as a team with our operators and field technicians."

Whether the project is driven by legislation, government funding, or private investment it’s clear that there will be plenty of activity in the 2001 construction market, especially for those who adapt quickly to change. This means gaining versatility in order to be capable of providing solutions to challenging project conditions. Efficiency Production’s interchangeable and combination trench shielding system will certainly go a long way in contributing to those solutions.