Completing a cast-in-place project that measures 46 ft. (14 m) wide by 39 ft. (11.9 m) long by 35 ft. (10.7 m) deep near the shores of Lake Michigan is a challenging project in and of itself. Now add in the challenge of being in the middle of an active British Petroleum (BP) refinery, and you have the unique situation that Superior Construction Company Inc., of Gary, Ind., found themselves.
"When the project started, in February of 2012, my original plan was to use a slide rail shoring system," said Paul Armstrong, superintendent of Superior Construction.
With its modular, flexible design the slide rail shoring system can comply with a wide variety of shapes and sizes. Installed from the top down and removed from the bottom up, minimizing excavation size, soil disturbances, restoration time and cost. Installation is done with low vibration, providing soil support for excavations, adjacent structures and existing utilities.
"I went to the internet and started searching for slide rail shoring systems," said Armstrong, "that brought me to GME's Web site. After a couple of conversations, they sent two representatives over to review the project in person." One of those people was Dennis Parker, product manager of GME.
"After meeting with Paul, we had a good idea of what he wanted and how he wanted to proceed with this project," said Parker.
Originally, the project was designed to be three smaller pits, meant to be used for sulfur retention.
As the project progressed, the three small pits morphed into one large pit, located in the middle of the active refinery. With the change of location and the change to one large pit, some site demolition was needed, requiring the vibration alarms to be removed. "With the partial site demolition that needed to occur and the vibration alarms removed, everybody involved in the project turned to sheeting," said Parker. "That opened the door for GME and Sunbelt Rentals Pump & Power Services, to quote our new MD Bracing system."
"We [Superior Construction] already had trench boxes on site from Sunbelt," added Armstrong. "They were already an approved vendor through BP; it just made the whole process a little easier."
The GME MD Brace System is the only large sheeting and bracing system 100 percent designed and built in the United States. The system consists of enclosed hydraulic rams and static extensions, which can be stacked and staged on top of each other during initial installation to help speed up installation time. Engineered to use a variety of sheet piles, the MD Brace is a cost saving system when compared to traditional weld and cut systems. It is designed for use on linear applications, bridge footings, pump stations, soil remediation's, tank installations and a myriad of other large projects.
"Sheeting and bracing seemed like it was a great deal that saved the client time and money by doing one large pit instead of three smaller ones," said Robert Morrow of Jacobs Engineering, the general contractor of the BP project.
"With the MD Bracing System now able to be used, we contacted DH Charles Engineering Inc., to have them perform the site specific engineering for the project," said Parker.
"First look at the job, (a year prior to actually breaking ground), this project appeared to be a very good candidate for the use of hydraulic bracing," said Jasper Calcara, president of DH Charles Engineering, Inc. "With the phasing of bracing installation and removal, along with the other aspects of the design, hydraulic bracing was the leading candidate." Phasing refers to installing the entire system to full depth, then, as the project progresses, removing part of the shoring, while maintaining a safe and secure working area.
With stamped and approved plans in place, using 50 ft. (15 m) long SZ-21 sheeting with four sets of the MD Brace rings, the requirement changed.
"After multiple revisions, over the course of a year, it was finally decided that the design would be based on groundwater level at 17 feet below grade," said Calcara. "This project combined almost every difficult issue that can impact a shoring pit; depth, building surcharges, deflection concerns, very strict clearance requirements retention of groundwater and poor soils."
"Going from full depth dewatering to having water at a depth of 17 feet was a huge change in the project for us," said Parker. "We had to change everything on the project; the sheets changed to 50 feet long SZ-27 sheets with a sealant on them. The number of MD Brace rings stayed the same, but two additional cut and weld rings was required at the bottom of the system, one of which was a sacrificial ring."
"From an engineering standpoint, I cannot say enough about DH Charles," said Armstrong, "when the project conditions changed or a problem arose, we had an answer on how to proceed the next day without any project time lost."
With the final shoring design submitted and approved, the project was able to break ground, under tight time constraints. "All material was on site when it was promised. GME did a great job with its manufacturing time line to make that happen for us," said Morrow.
The success of this project relied on constant communication between all parties.
"Dennis and myself were proactive as a team, which allowed us to stay ahead of the project, which allowed us to have an overall smooth project (from an engineering stand point)", added Calcara.
"From GME's stand point, we wanted to give Superior Construction the closest thing we could to a turnkey operation," said Parker.
"That meant, not only did GME source the sheets needed for the system, we had an installation consultant out on site to instruct them on installation and removal of the system just as we do with our slide rail shoring system."
"Being there for the first full week of installation and consulting with them on the removal of the system, proved to be a great learning experience," added Benjamin Sybesma, assistant slide rail manager of GME and the installation consultant on site.
"There proved to be many obstacles throughout this job, but through hard work and persistent communication, GME and Superior Construction were able to work through it and produce an excellent and safe shoring project."
"Having the GME installation consultant on site was a big thing," said Armstrong. "Having that built in was a key for the overall safety of the site and the people around the site."
Access to the site was another minor obstacle that had to be overcome. Since the project was taking place inside an active refinery, space was limited. The excavating was done by John Deere 350 and an 85 D mini. All other equipment needed for the site had to be lifted over a 70 ft. (21 m) tall by 30 ft. (9 m) wide wall by a crane.
With the project commencing under tight time constraints, one thing stood out about the system: the flexibility of the MD Brace system. This was the first time that Superior Construction had used a system like the MD Brace, so there was a small learning curve. However, by using the MD Brace system, Superior Construction was able to gain some advantages over using a traditional beam and cut process with sheet pile. "With the MD Brace, we didn't have to worry about welding or the exposure involved with trying to place beams," added Armstrong. "That allowed us to save a lot of labor time."
"Being a hydraulic system, [the MD Brace] provided an extra level of protection to the adjacent structures by actively pushing against the sheets, and minimizing potential movement," said Calcara.
The MD Brace has the adjustability to work with rectangular and non-rectangular excavations to be safely shored.
"The flexibility of the system allowed us to work with what the sheets gave us. That same flexibility, and overall ease of the system, enabled us to save time during the installing and even more so during the removal of the system" said Armstrong. "Overall, once the project got underway, I had no issues with the system that weren't quickly solved. I would push to use the MD Brace again on a similar project, especially one with similar time constraints."
Jacobs Engineering provides full-service engineering, design, construction and construction management services. For more information, visit www.jacobs.com
Sunbelt Rentals is one of the largest equipment rental companies in the United States. The company serves a wide variety of customers from commercial contractors to specialized service industries. For more information, visit www.sunbeltrentals.com
DH Charles Engineering Inc. is a civil/structural engineering firm specializing in providing construction-engineering services to contractors throughout the United States and Canada. For more information, visit charlesengineering.com
Superior Construction Co. Inc., located in Gary, Ind., is a general contractor with ties in the highway, industrial, concrete material and wastewater treatment industries. For more information, visit www.superior-constructions.com
GME is a producer of trench shoring and shielding equipment. The products it offers range from a single hydraulic shore system, trench shields, slide rail systems and hydraulic bracing systems. As an industry pioneer since the 1960's, it holds patents on many trench shield features and continues to lead the industry in the areas of product development, innovation and effectiveness. For more information, visit www.gme-shields.com