California State University - Sacramento (Sacramento State) is “going green.” The university has several new building projects underway which are incorporating aspects of “green building,” a process to create buildings and supporting infrastructure that minimize the use of resources, reduce harmful effects on the environment, and create healthier environments for people.
One of the green building projects at Sacramento State includes upgrading the sewer system on campus. A new 33,000 gal. (120,000 L) holding tank and pump station were recently installed to augment the current system. Tidelands Construction Company from Brentwood, Calif., was the general contractor installing the tank and pump station.
On a busy campus such as Sacramento State, a project such as this was not going to be easy or routine. The excavation site had very limited access and many surrounding obstacles to contend with, including:
• A main road for the university and an adjacent parking structure
• A drainage ditch and railroad line in close proximity on the opposite side of the excavation from the road
• An existing pump station and generator near the excavation site
• High volume of both vehicle and pedestrian traffic on the adjacent road.
There was little to no room for equipment access except from the ends of the long, deep and narrow excavation, unless the road was closed. Shoring the pit was a major challenge as traditional sheet piling or sloping was not an option.
D.P. Nicoli, Efficiency Production Provide Shoring Solution
D.P. Nicoli Inc. was contacted to help solve the shoring problem. Ryan Jaffe, vice president of Slide Rail Shoring, worked with Phil Toelkes, owner of Tidelands Constructions, and J. M. Turner Engineering to come up with a shoring plan that would work for the unique and challenging situation, yet still be affordable and relatively easy for the contractor to install.
D.P. Nicoli consulted with Mike West, vice president of engineering at Efficiency Production Inc. —a manufacturer of trench shielding and shoring equipment. D.P. Nicoli proposed using Efficiency’s Slide Rail System in a six-bay, 4-Sided Multi-Bay Configuration. Nicoli’s experience with large pits using Efficiency’s slide rail and the patented waler system seemed like a good fit.
“Efficiency’s Slide Rail really was the perfect solution,” said Hans Vermeulen, project engineer of Turner Engineering. “Everything went according to how it was drawn up.”
“I’d worked with Nicoli for other shoring needs, but never for the Efficiency Slide Rail,” said Tony Zottola, project superintendent of Tidelands Construction. “Installation went really sweet all the way to the bottom without any binding or twisting. With other slide rail systems I’ve used, I’ve needed to get into the hole and weld the system just to hold it together so it wouldn’t fall apart.”
’Dig and Push’ System Reduces Over-Excavation
Efficiency’s Universal Slide Rail is a component shoring system comprised of steel panels (similar to trench shield sidewalls) and vertical steel posts. The versatile system can be used in a variety of configurations, such as small four-sided pits; large unobstructed working pits as big as 50 by 50 ft. (15.2 by 15.2 m) with Efficiency’s ClearSpan System; or in a linear Multi-Bay configuration to install length of pipe over 40 ft. (12 m).
Slide Rail is installed simultaneously as the trench or pit is excavated by sliding the panels into integrated rails on the posts — either double or triple rails depending on needed depth — then pushing the panels and posts incrementally down to grade as the pit is dug; a process commonly referred to as a “dig and push” system.
Big Clearance for Tank Made Easy
The entire excavation needed to be 16 ft. (4.8 m) wide and 89 ft. (27 m) long. The tank was 64 ft. (19.5 m) long and needed to be placed in a single pick set at 28 ft. (8.5) deep.
The biggest challenge was engineering a shoring system that would provide an unobstructed open clearance to the pit of at least 60 ft. (18.2 m). Efficiency’s multi-bay configuration uses parallel beams that incorporate into the vertical posts and pin-in-place standard trench box spreaders as cross-members. The parallel beams have rollers, and when horizontal walers and sacrificial members are used, the entire cross-member apparatus can be removed resulting in an unobstructed clearance to the shored excavation.
“Compared to other systems the Efficiency slide rail has a little more room to play with because of the integrated rails on the posts and the moveable parallel beams sliding along the face of the posts,” Zottola added. “This was very beneficial due to the limited access that we had. We could only install from a couple of spots around the pit, but we had no problem handling the system’s components.”
Slide Rail is unique in that it is installed and removed incrementally, which allows the trench to be properly shored throughout the entire installation or removal process, maximizing the stability of the surrounding ground.
“Clearly, we had no safety issues with the system, it was very safe,” said Zottola.
The system was engineered to incorporate a 60 ft. long W24x162 I-beam welded onto a larger W36x300 I-beam waler, which was then welded to the outside of the vertical posts at the top. Sacrificial beams were placed at the shoes of the linear posts below grade, to eliminate the potential of deflection when the cross-member assembly was removed. D.P. Nicoli Inc. supplied all the slide rail components and had their Senior Slide Rail Specialist, Bruce Ellis, on hand to work with the Tidelands crew.
Smooth, Easy Tank Installation
Tidelands began the excavation by first benching and sloping down approximately 8 ft. (2.4 m). The slide rail system components included four 32 ft. (9.7 m) vertical corner posts and five sets of 32 ft. linear posts; and 5 in. (12.7 cm) thick, 14 ft. (4.2 m) long, 8 ft. and 4 ft. tall slide rail panels. Tidelands used a Kobelco 400 excavator to install the system.
Water was encountered at 30 ft. (9.1 m). A 6-in. (15.2 cm) pump was inserted and the water piped thru a small sediment tank. A small Bobcat excavator was lowered into the pit to help finish the final grade.
The base and first section for the pump were set and backfilled at 28 ft. (15.2 m) deep. After the walers were secured to the posts and the sacrificial beams put in place, three of the five Efficiency parallel beam-spreader assemblies were removed for the tank set. The result was an unobstructed pit that was 60 ft. long and was able to accommodate the 64 ft. long tank.
A crane was brought in to set the tank. The tank was also hooked up with a separate strap attached at one end to the excavator, which helped guide the nose of the tank under the last sets of spreaders. The tank was then sand-bagged in place and backfilled. Tidelands also used a Caterpillar 375 excavator when removing the slide rail components.
The entire tank and lift station installation — from first cut to backfill — took approximately four weeks in October 2006.
D.P. Nicoli is a resource for the shoring and piling needs of the heavy construction industry, offering a wide variety of materials and equipment for sale or rent. They currently serve the Western United States from three facilities in Oregon and Northern California. Celebrating its 25th anniversary, DPN has developed relationships with both large and small customers.
Efficiency Production Inc. provides a wide selection of standard and custom trench shielding and shoring systems.
For more information on D.P. Nicoli, visit www.dpnicoli.com.
For more information on Efficiency Production Inc., visit www.epi-shields.com.