Trends Spring 2016 | Page 6


The first step involved in the complex task of renovating the Byllesby Dam powerhouse is determining how the building was originally constructed .

But doing that isn ' t easy when it ’ s clear those who built the powerhouse more than 100 years ago did not strictly follow the original architectural drawings and failed to record their many deviations from those plans .
That ’ s the challenge facing the Ayres Associates team hired by Dakota County , Minnesota , to rehabilitate the structure into a modern-day producer of electricity , while recognizing its early 20th century aesthetic glory .
Last December Jason Ingram , Ayres ’ manager of land survey , sent a two-person survey crew to the Byllesby Dam site armed with the latest in high-density , or HD , laser technology . The surveyors spent two days at the site taking a set of 62 high-density laser scans of the entire complex – the dam , its adjoining floodgates , and the powerhouse .
Each of those scans creates a 3-D dataset of that part of the dam site , Ingram explained . “ The scanner measures features at a rate of up to 1 million points per second , mapping in such detail that it can look like a photograph when viewing the point cloud dataset ,” he said .
Each of these 62 sets of data , called a “ point cloud ,” provides precise measurements detailing key information , such as materials used , the thickness of walls , where pipes enter and exit walls , flatness of floors , and much more .
Through a process called “ registering ,” surveyors will analyze each point cloud and convert the data
into one “ point cloud dataset .” This registration process “ is like putting a puzzle together , piecing each of the 62 scans together with survey-grade accuracies ,” Ingram said .
Another advantage to scanning that was recognized on this project was the equipment ’ s ability to pick up data on everything it can see and measure . For example , the scanning picked up the existing spillway , which is being rehabilitated , along with areas that had concrete removed along its surface . From the point cloud , cross-sections were cut and an existing surface model was generated to aid engineering staff in determining a proposed finished profile of the surface for construction . Although this was not the targeted use of the point cloud , the technology enabled all data to be collected and saved for future benefits to design staff without the need for more costly site visits .
Once that puzzle is completed , the point cloud dataset will be sent to Ayres ’ BIM Specialist Bryant Christenson . BIM stands for Building Information Modeling , a process by which Christenson will use Revit computer software to convert the “ point cloud dataset ” into a 3-D computer model of the entire Byllesby Dam site , including every room within the powerhouse .
“ This will give a very good representation of what ’ s there ,” he said . “ It will indicate all the materials that are there and their condition .”
Ingram explained that these 3-D computer models will enable Ayres architects to , in a 3-D virtual environment , remove existing equipment and add proposed new equipment to the powerhouse while identifying any potential conflicts with the building ’ s existing infrastructure .
Further down the road , Christenson said , Ayres also will be able to use the 3-D computer models to create pictures of their redesign proposals that can be shown at public meetings related to the powerhouse project . When a final design decision is made , those models will be used in creating the project ’ s construction documents .
– Bob Brown