There are so many individual activities, iterations and processes that happen during the life cycle of a project; and in this example, a Waste Water Treatment plant. When you look into the life of the project there are numerous opportunities to increase efficiency in design, fabrication, construction and operation that will equate in reduced cost, decreased schedule and increased communication. The result is one that will benefit all involved parties and build a better project.
Prefabrication is one of those processes which I would consider to be low hanging fruit. By definition the process of which something is built does not change, only where it is fabricated. Prefabrication can vary both in size and complexity. At it's simplest form it could be to simplify a minor individual construction task or encompass an entire trade activity. This simple change of mindset can be easily and widely adopted across all construction activities with minimal direct cost or risk to the engineer, owner and contractor.
Baby steps is a great way to describe the adoption of prefabrication on a construction site. Here is an example of a WWTP project where the contractor was to install new 12" diameter stainless steel piping in an existing operating facility. The original engineered plans were not conducive to prefabrication, but due to tight construction schedules, even tighter construction budgets, and serious liquidated damage fees, we had to change the way the project was built.
The engineered plans for the 12" diameter stainless steel piping were made from 2D asbuilts which were not current and the contract was written where the contractor was to "recommend and submit a final designed route". (Notice the shift of liability?) Simply put, to get from A to B, we had a twisted mess of existing conduit, piping, structures and equipment that we needed to snake the new piping around. With no real existing plans to go off, the first step was establishing what was physically between the point of connections. To do this, laser scanning the entire building was the best and most efficient means. Not to mention, we were carrying the piping through the building to the exterior for another 800'. This now meant we needed to not only scan the interior and exterior, but bring in survey as well to verify our tolerances and to put the project in State plane coordinates. In this case the prefabrication tolerances were very tight due to the bends, welds and connection points.
The preplanning coordination reduced the amount of field welds by 85%!
After modeling the proposed piping route in Plant 3D, using the cleaned point cloud data, we ran clash detection in Navisworks to see if any of the newly not yet constructed elements of the project would impact the relocation of the line. Once the rerouted design was completed we were able to engage the owner and engineer with the plan, first though the use of a Navisworks fly though, and then the final approval came from 2D drawings that were created in Plant 3D. This quick turn around and buy in from the owner/engineer was unheard of. Through the use of 3D communication tools the owner/engineer understood the plan, knew the design would work and could tell the contractor had a grasp on exactly how to execute the construction.
Once we had buyin from the stakeholders, we then consulted the pipe fitters and asked them how they want to install this. What a crazy idea! Ask the guys that install it how they want to do it. I can't lie, they first laughed at us and said they could not build what we designed. The spacing of the trapezes, the existing pipe which had to be left in place, and the new pipe to be installed around it, created a major constructability issue. Until we were able to walk through the plan in 3D. Using the 3D model with the pipe fitters we were able to establish what lengths of pipes, how and where the cuts would be, and where the field welds would take place. The preplanning coordination reduced the amount of field welds by 85%! A huge by-product of the 3D model that most contractors do not take advantage of is the creation of piping ISO plans for fabrication.
After it was all said and done, we were able to shop the prefabricated plans all over the country, and saved 30% over the original estimate. This resulted in decrease procurement costs, decrease in field labor cost, little or no rework, zero additional cost in unexpected conflict realignments of existing utilities and no unplanned impacts to schedule or operations!
Contractors need to realize utilizing new technologies and processes is not a direct measurable cost. It has so many benefits which go far beyond a dollar for dollar comparison. The hidden message in my story is not about how much time or money was saved, it is about how the contractor was able to reduce or mitigate risk on this activity through the use of technology and prefabrication. Saving money and increasing efficiency is a by-product. How can you utilize prefabrication on your project?