Joshua Petersen has worked for Dakota County as the Senior Water Resources Engineer since 2011.
Petersen has helped with multiple projects throughout the years, and now he is helping with the major upgrades to the Lake Byllesby dam. The dam and turbines are more than 100 years old, and the new turbines they are installing are expected to last close to another 100 years.
Q: How are upgrades to the Lake Byllesby Dam going?
A: Very good! We just started what will be a multi-year turbine and powerhouse replacement project. A lot of the work that we have completed this spring has been in preparation for demolition of the existing powerhouse and equipment. The demolition will start this summer and will take three months.
Q: Why does the dam need upgrades?
A: The dam has hydropower equipment that provides revenue to Dakota County that allows us to offset the costs to operations of the dam. The hydropower equipment which is powered from the water on the Cannon River consists of turbines and generators are all original equipment from 1911 and have far exceeded their useful life. The powerhouse structure is also all original and no longer meets building code requirements and has multiple issues that didn’t allow it to be reused. Dakota County has determined that the best solution was to replace the hydropower equipment and powerhouse structure with brand new equipment. This new equipment is much more efficient and will provide over double the power production. The costs associated with building the project will be offset by the increased power production.
Q: I'm assuming the project is being done in phases i.e. turbines are a phase, head gates are another, removing damaged concrete, etc. What was the most recent phase? What's the next one?
A: Yes! There are several phases that make a project like this very complex. The first phase was to make sure the dam was safe during construction, which required massive amounts of concrete to be poured inside the dam to provide stability to replace the mass of the powerhouse itself which was a component of keeping the dam in place. We’ve finished all mass concrete pours, and now were onto the existing structure demolition phase which requires a lot of engineering and oversight. Dissecting a 110 year old building attached to the side of a high hazard dam is complex and requires a lot of coordination, which is why the demolition will take approximately three months. After demolition the new turbine equipment will be installed starting at the bottom of the new powerhouse and working up. Because of the size of the equipment the building will actually be built around the equipment, so the actual new powerhouse structure will be one of the last phases you’ll see on the project.
Q: What part of the upgrades are going to be the most difficult? The easiest?
A: The most difficult phases will be installation of the new turbine equipment. The equipment is manufactured with 0.001” tolerances, so it’s critical that we install that equipment in alignment perfectly in order to not have any issue with its efficiency or long term maintenance. The easiest phase was honestly the one we just completed with the mass concrete for dam stability. This is really just pouring concrete into the back bays to provide mass which supports the existing dam structure.
Q: When will the upgrades be completed and how long until some are needed again?
A: The turbine and powerhouse upgrade project is anticipated to be completed Fall 2022. It is anticipated that this new equipment will last at least another 50 years, but we are hoping to get at least another 100 years out of this equipment as well. Like any structure or building, the Byllesby Dam requires maintenance, some of which is annually, some is every 5-years and others every 15-20 years. Dakota County programs for these future projects as part of our financial planning processes.
Q: Tell me how you became the Senior Water Resources Engineer? Did you always want to be an engineer?
A: I’ve worked for Dakota County approximately 10 years now and applied for the position in 2011 when the previous engineer retired. Previously I worked for two different consulting firms in Minnesota and Iowa working on various water resources projects in the Midwest. I received my degree in Civil Engineering from Iowa State University in spring of 2007. I knew I wanted to be an engineer from a young age. I had a family member that I looked up to that was also an engineer. Being a farm kid from eastern Iowa, I spend a lot of time wrenching on farm equipment, dirt bikes, snowmobiles and ATV’s with my dad on the farm. Engineering is about problem solving, which I have always had a passion for. The advice I give to a lot of young students who want to become an engineer is to not worry about all of the details behind whatever engineering field you decide but worry more about whether you have the drive to want to solve problems, because that is what you will be doing every single day of your career.