The Stone Arch Bridge, a historic 19th-century railroad bridge in downtown Minneapolis, spans the Mississippi River at Saint Anthony Falls. It now serves pedestrians and cyclists. In 2024, the Minnesota Department of Transportation initiated repairs to five of the bridge's piers near Mill Ruins Park, but strong river currents posed a safety risk for divers working on the project. Contractor J.F. Brennan Co., Inc. (Brennan) partnered with Barr to perform hydraulic modeling and structural analysis for a custom temporary flow deflector system designed to slow water around the piers during underwater repairs.
Barr built a two-dimensional computer model of a 1,550-foot stretch of the river around the bridge. The model accounted for water splitting between the Xcel Energy powerhouse and spillway as well as the influence of the downstream dam. Using existing riverbed and surface data, we tested conditions up to 18,000 cubic feet per second, the maximum flow rate considered safe for diving.
Five flow deflector options were tested—one for each pier. The modeling showed that the deflectors could successfully slow water in underwater work zones to less than four feet per second, which would allow divers to operate safely. Barr also calculated the forces acting on each deflector. The deflector designed for Pier 10, facing the most intense flows, was estimated to withstand up to 50,000 pounds of pressure. These results informed the final frame and anchor designs.
By combining hydraulic and structural expertise to inform deflector design, Barr helped Brennan ensure diver safety, minimize construction delays, and support the rehabilitation of one of Minneapolis’s most iconic landmarks.
The Grosse Ile Parkway Bridge crosses the Trenton Channel of the Detroit River in Michigan, connecting Grosse Ile Township to the mainland in Riverview. When high-velocity flows and large depths presented challenges to underwater work needed to repair six of its piers, contractor J.F. Brennan Co., Inc. (Brennan) looked to Barr. We provided hydraulic modeling and a flow evaluation to support the design of temporary flow deflectors around the piers that would help keep underwater workers safe.
Using a two-dimensional Adaptive Hydraulics (AdH) model, we evaluated flow velocities, recirculation patterns, and hydraulic forces around proposed temporary flow deflector structures. Modeling scenarios included various flow rates and deflector configurations to determine optimal placement for minimizing flow impacts during construction. The model was calibrated using site-specific bathymetric surveys and velocity measurements collected during two field campaigns.
Flow deflectors were proposed at all six piers to provide calmer work zones for divers and reduce hydraulic loads on the work area. Barr simulated high-flow conditions (up to 280,000 cfs in the Detroit River, 86,000 cfs in the Trenton Channel) to estimate forces on the deflectors, with results informing anchorage design and construction sequencing. The analysis also quantified potential impacts on adjacent piers and offered strategies to mitigate recirculation zones where velocities exceeded target thresholds.
Barr’s recommendations supported safer and more efficient underwater construction by ensuring the deflector system would perform under anticipated hydraulic conditions while minimizing risk to adjacent infrastructure.
Potash mines in Canada have tailings facilities that are considered high-hazard dams according to the Canadian Dam Association (CDA). These facilities require ongoing inspections, analysis, instrumentation, and modifications to meet current guidelines and continue to receive tailings. Barr began providing these services to a potash mine in 2010 and has since expanded to provide similar dam safety services for five sites in Saskatchewan. Barr is currently the designer of record and engineer of record for most of these facilities.
Our dam safety-related work has included dozens of annual dam safety inspections, where the results are reported to the provincial regulatory authority. Such assessments have been completed at numerous facilities and have led to the design of buttresses, slope modifications, outlet structure modifications, seepage/drainage improvements, and erosion repairs. In many instances, a Failure Mode and Effects Analysis (FMEA) has been completed to identify and categorize dam failure risks and identify risk reduction, surveillance, and monitoring measures associated with potential failure modes.
Instrumentation and monitoring programs have been developed for most of the embankments and salt piles at these mines, including installation of piezometers, slope inclinometers, and other movement instruments. Barr has installed remote monitoring equipment to allow the client to view near-real-time data on a website.
The monitoring programs call for regular visual inspections of the tailings storage facilities, including dikes, seepage collectors, hydraulic structures, coarse tailings piles, and other components. Monitoring reports are prepared at varying intervals to provide the client and regulatory agency with information on potential unsafe conditions.
A Canadian mining operation has produced potash and generated fine and coarse tailings since the 1970s, so when its fine tailings cells were reaching capacity, Barr was called upon to analyze potential options.
Following an alternatives assessment, Barr identified and designed upstream embankment construction and monitoring methods to extend tailings cell life and manage brine, and we developed a plan to resolve issues with both coarse-tailings operations and brine turbidity. Barr designed a 270-hectare expansion of the brine pond to meet future operating and disposal requirements.
Barr investigated soil conditions, performed geotechnical evaluations, and designed an upstream dike raise that includes a center decant structure to manage brine and enhance the stability of future dike raises. In addition, we oversaw project construction and designed another upstream dike raise on the second fine-tailings cell. The client requested assistance with creating a tailings management and expansion plan to provide a long-term vision for the life of the facility.
With our assistance, the facility successfully operates its fine-tailings cells, meeting brine-management-turbidity goals and operating its coarse-tailings pile more effectively. The client has a detailed plan for engineering and operations staff to follow that provides monitoring requirements, responsibilities, action levels, and contingency activities in accordance with Canadian Dam Safety (CDA) guidelines for dam safety.
The City of Boulder has a robust hydroelectric program that can be traced back to 1906 when the Boulder Canyon Hydro Plant was built and operated by the Central Colorado Power Company. The program now includes eight hydroelectric plants that produce enough energy to power thousands of households in the greater Boulder, CO area as well as provide drinking water for the community. Small hydroelectric plants are situated along pipelines running down into the city, converting the water energy to electricity using Francis turbines.
In 2009, the city turned to Barr to assist with their hydroelectric program operation plan by solving some relay protection issues. Satisfied with our work, they came to us again in 2011 when they received a federal grant to replace one of their hydroelectric plants. The plant was old and still depended on the original equipment from decades ago. Barr provided electrical and civil/structural design for a substation upgrade, including electrical equipment updates, protection studies, interconnection studies, updates to the switchyard and 5kV switchgear, and negotiations with Xcel Energy to update the interconnection agreement for the new 5MW generator.
It soon became apparent that spacing would be a significant challenge during the hydro plant replacement project. The substation was a difficult area to work in, and the old transformers (which had to be hauled out and replaced) were set on old railroad carts. Despite these challenges, Barr completed the work on schedule and under budget to get the plant online in 2012.
We have continued to support the city’s hydroelectric program. In 2016, we provided commissioning controls support, conducted arc-flash studies, and assisted with operations. In 2022, the generator step-up transformer at the Boulder Canyon Hydro Plant failed. Barr assessed the problem, determining that a fault had occurred in a lower part of the winding. We assessed two options—repairing the transformer or acquiring a new one—and determined that repairing it would be the more cost-effective and timely solution. Barr provided project management, testing, and commissioning services for the removal, repair, and return of the transformer. Then, in early 2025, we conducted a successful operational test on the new transformer and returned the plant to service in time for spring runoff operation.
Innovative remediation and restoration at one of the largest sediment Superfund sites in Minnesota
The 255-acre St. Louis River/Interlake/Duluth Tar (SLRIDT) Superfund site in Duluth represents one of the first hybrid dredging and capping sediment remediation projects completed in the United States. Seven decades of industrial discharges created two peninsulas and three water bodies containing polycyclic aromatic hydrocarbons and other contaminants in a Lake Superior estuary that is a Great Lakes Area of Concern. Tar seeps and soils were cleaned up in the 1990s, but the 90 acres of contaminated sediment proved most challenging.
In 1999, the Minnesota Pollution Control Agency (MPCA) decided that all contaminated sediment must be dredged and placed off site—a remedy that would have cost $140 million and raised concerns about air and water impacts in the surrounding neighborhood.
Working with the responsible parties, the MPCA, a peer-review team, natural resource managers, and numerous other interested groups, Barr developed and designed an innovative remedy involving an onsite contained aquatic disposal (CAD) facility and 18 different types of caps. One of the innovations included a surcharge cap to avoid dredging the highest PAH concentration sediment in a residential bay while restoring the pre-remediation bathymetry within two years of placement. Another innovation involved the first commercial use of an activated carbon mat to prevent porewater under the surcharge cap and in the CAD from impacting the bioactive zone of the caps.
The SLRIDT remedy involved several examples of beneficial use of materials, including the CAD, which involved converting a contaminated former shipping slip into a shallow bay by placing dredged contaminated sediment behind a lined rock dike at the mouth and then reintegrating it with the river after capping. Also, organic sediment dredged to restore a nearby river channel as part of the project was placed over the site’s caps to accelerate ecosystem recovery with local aquatic flora and fauna.
The project resulted in savings of $90 million compared to an all-dredging approach and restored 106 acres of aquatic and riparian habitat for fish, wildlife, and the community of Duluth. The site is currently in the second decade of a 30-year long-term monitoring and maintenance (LTM&M) program, which has shown the caps are performing as designed and the ecological recovery has been successful.
Minnesota Diversified Industries (MDI) provides job opportunities and services for people with disabilities at its four locations. The company produces standard and custom plastic totes, trays, boxes, sheets, rolls, and tree wrap; provides contract production services; and offers medical device assembly.
When MDI’s Grand Rapids facility wanted to upgrade the older, outdated controls on its Line 1 extruding equipment to improve the line’s efficiency and reliability while reducing downtime, Barr stepped in to shoulder responsibility for the engineering, procurement, construction, and management of the project.
Barr designed the new and improved control systems for the existing extruding machinery on Line 1, procured new controls equipment, hired and managed an electrical contractor for demolition/retrofit installation and an extrusion expert to advise on control settings, provided oversight of startup and commissioning, and managed the entire project.
The new controls were installed on each of the four assemblies that comprise Line 1, including new PLC controls, new HMIs (human-machine interfaces), and updates to the WonderWare system for central oversight of all the new controls. In 2018, Barr upgraded MDI’s WonderWare system replacing a Windows 98 PC to a new Touchscreen PC running off Windows 10 for this line.
Through strategic partnerships, an intimate understanding of the facility, and significant knowledge of the process and industry, Barr provided a total, turnkey package to MDI for automatic control and improved efficiency and reliability of its Line 1 equipment.
Due to the success of the Line 1 project, the same approach was executed by Barr for the Line 2 follow-up expansion project, which was successfully completed in 2024.
Southwestern Power Administration wanted to enhance the electrical capacity of its transmission line and upgrade the shield wires to optical ground wire (OPGW) cables on their Dardanelle transmission line. They hired Barr to develop a comprehensive solution that preserved the integrity of the existing lattice steel tower structures to minimize the need for extensive structural modifications.
Southwestern was concerned that the project might require numerous structure replacements to meet clearance requirements and address potential structural failures associated with larger capacity conductors. Barr's team conducted a thorough analysis, which included an advanced composite core conductor study as well as PLS-CADD and TOWER analyses of the transmission line.
Conductor study
Our research looked into advanced transmission technologies (ATT)—infrastructure, hardware, and software options that increase transmission line capacity—and identified an aluminum conductor composite reinforced (ACCR) conductor, a specific type of transmission wire that met all specifications for the line. Not only did the new ACCR double the electrical capacity of the line, it also had more favorable physical properties and sagged less than the existing aluminum conductor steel-reinforced cable (ACSR) conductor. This innovation allowed us to maintain the existing structures, requiring only a few minor structural reinforcements, which significantly reduced project costs.
Crossing the Arkansas River
A significant challenge was designing the line to span the 2,695-foot-wide Arkansas River. Due to the span length and the required marker balls, the OPGW needed to be much stronger than the rest of the line. Accommodating the different OPGWs while balancing tensions to prevent increasing differential loading was a challenge. The wire selected for this span met the OPGW-to-conductor separation requirements and conductor-to-Arkansas River clearance standards.
Substation fiber optic upgrades
To facilitate the addition of the OPGW on the transmission line, fiber optic cable was required at the Dardanelle substation. We used existing drawings and a site visit to identify the need for additional fiber optic communications infrastructure.
Barr successfully completed the design phase in 2023, and construction is underway. This project was originally intended to be a two-phase project due to structural replacements and upgrades. By effectively using ATT through the chosen ACCR conductor and optimizing designs, we enabled Southwestern to execute this upgrade as a single project, avoiding the complexities and costs associated with multiple-phased projects.
The Unilever facility in Jefferson City, Missouri, is a manufacturer of personal-care products such as soap and shampoo. The facility currently discharges 130,000 to 150,000 gallons per day of wastewater to the city’s wastewater and sewage collection-and-treatment system. The company has indicated that future flow rates of wastewater could be as high as 250,000 gallons per day.
When Unilever installed upgraded pretreatment equipment at the facility, it also considered installing a new 350-gallon-per-minute pump station nearby to reroute the discharge into a separate force main that would be built to connect to Jefferson City’s collection system at a pump station located about 1.5 miles north of the facility. Another option was to route the discharge to an abandoned, city-owned, 20-inch ductile iron force main, retrofitted to serve as a carrier pipe for a new force main dedicated to the Unilever pump station. The second concept would call for installing a smaller-diameter force main inside the abandoned main. Barr developed a concept-level design of this solution, along with opinions of cost for both options.
Nicollet Commons Park serves as the focal point of the city of Burnsville, Minnesota’s mixed-use development known as the Heart of the City. Nestled between retail shops, restaurants, diverse housing, and office space, the park is home to a popular water feature and numerous city events.
Burnsville began experiencing significant water losses while operating the water feature, so in 2019, the city hired Barr to evaluate the problem. After our evaluation, the city decided to renovate the park to address the water loss and add new interactive components. In addition, Burnsville took the opportunity to install new audio and landscape-lighting systems.
Lighting features advanced color-changing LED technology, and an associated control system allows the city to program the light color by zone throughout the park. Lighting schemes can be changed depending on the desired effect, such as red, white, and blue for Independence Day.
Today, Nicollet Commons Park is a renewed centerpiece for the city of Burnsville.