An industrial client faced challenges posed by selenium leaching into groundwater and surface water. The company had selected a biological system that relies on microbes to remove dissolved selenium from wastewater; the process generates biosolids containing residual selenium.

Our client’s goal was to assess correlations between microbial-ecology and system-operations data to learn whether modifying the microbes’ environment had the potential to boost treatment system effectiveness. Before committing significant amounts of money to make operational changes, though, the company asked Barr to perform a preliminary statistical analysis.

There was little information in wastewater or academic literature about facilities using microbial-ecology data to directly inform treatment operations, especially for selenium-removal processes. Data the client had collected for the project included 16S ribosomal RNA (rRNA) community profiles, adenosine triphosphate (ATP) measurements, and microscopy data.

Barr’s analysis of that data correlated several dominant microbial groups with plant performance. When we evaluated those groups further to determine which system conditions would promote or inhibit microbial activity, the operational parameters predicted to limit concentrations of reduced selenium in the effluent were typically the same as those we identified through direct pairwise correlation of the parameters and reduced-selenium concentrations. In other words, the direct application of microbial-ecology data to inform plant operation did not yield much promise for improving treatment effectiveness—a finding that gave our client the insight needed to avoid spending money on further analyses.

Still, evaluating the microbiology data provided the company with several benefits, including measuring  microbial activity and performance in real time via ATP and microscopy techniques, and gaining a microbial-community operational baseline to support future root-cause analyses of reactor upsets.

Improvements to Highway 93 in British Columbia have been part of ongoing infrastructure rehabilitation in Canada’s national parks and historic sites. Along the highway adjacent to the Vermilion River, Barr has performed environmental impact assessments for Parks Canada Agency, including habitat assessments for potentially impacted species.

When the agency determined that constructing a rock revetment to stabilize a failing slope would affect fish habitat in the river, Barr was asked to develop compensation measures to improve habitat for bull trout, a species of special concern in British Columbia. At the time, there was no place for trout to rest and spawn, and the river was susceptible to falling debris from the eroding highway slope above.

Barr designed boulder vanes and clusters to create small pools in the river. Within an hour of completing the restoration, trout-spawning activity was observed near the first boulder vane (see video below). The natural channel design provided habitat features that were essential for bull trout, consistent with the geomorphology of the Vermilion River, and complementary to the slope-stabilization measures for the adjacent highway.

Southern Minnesota Beet Sugar Cooperative (SMBSC) operates the largest sugar-beet processing facility in the United States. In 1999, SMBSC implemented a five-year plan to modernize and expand its Renville facility to increase processing capacity. Barr supported the cooperative in these efforts and completed an environmental assessment that evaluated the impacts of the anticipated 40,000-acre increase in sugar-beet acreage.

SMBSC also needed to revise its NPDES permit to increase the average treated-process-water discharge. Barr prepared the permit application, submitted it to the Minnesota Pollution Control Agency, and assisted with negotiations. The application included a nondegradation (the Minnesota equivalent of antidegradation at the federal level) analysis, including an evaluation of alternatives to the proposed discharge and additional control measures. The permit issued in 1999 had had unique provisions, including a phosphorus-trading program, discharge restrictions during summer low-flow conditions, and an annual phosphorus-mass-loading cap.

After the factory came online, our client found that dissolved minerals in the sugar beets and additives were present at higher concentrations in the treated effluent than the permit allowed. SMBSC and Barr evaluated the process, treatment technologies, and discharge alternatives, finding that a variance was needed. Barr assisted SMBSC in preparing a variance request, which was approved by the MPCA.

Since its 2009 permit expiration, Barr has continued to work with SMBSC on its NPDES permitting and compliance, including helping to develop and implement a long-term permitting and wastewater-management strategy. We provide value through our integrated environmental and engineering teams, which work through complex multidiscipline issues relating to wastewater management and permitting.

Ecosystem project showcases nature and engineering

Barr's team worked with artist Christine Baeulmer to design and build a self-contained bog atop an entrance canopy of the Minneapolis College of Art and Design.

Creating and sustaining a moisture-loving plant community in the desert-like conditions on a roof posed challenges related to water sources, circulation, evaporation rates, and pH balance. To keep the plants in two inches of water, we designed a cistern to collect the building’s stormwater runoff and recirculate it to the bog using a solar pump, with city water as a backup. Funded by a grant from the McKnight Foundation, the bog showcases the team’s ability to establish a natural ecosystem in an unnatural urban environment, and the results exceeded everyone’s expectations. The project began as a temporary art exhibit, but became a permanent installation. 

The Hettinger County Water Resource Board hired Barr in 2016 to improve safety at Karey Dam in western North Dakota. Over time, this historic community asset and recreational destination had become a dangerous liability that posed drowning risks. 

Barr’s solution involved removing the existing low-head dam and replacing it with a series of engineered rock riffles. A detailed assessment of flow conditions helped confirm that the project would not worsen the downstream scour hole post-construction and consequently undermine the dam’s structural integrity. Our approach significantly reduced the safety risks posed by the deteriorating structure and eliminated the development of deadly recirculating currents, thanks to the distributed energy loss between each rock arch.

Constructed in fall 2020, Karey Dam is now the first rock riffle structure in the western part of the state. Barr’s innovative solution improved dam safety while also providing benefits such as river connectivity and aquatic organism passage. In addition, the design enabled continued water storage in the upstream pool and has minimal impact on water-surface elevations and structures upstream of the site.

Without Barr’s assistance with identifying funding sources, this project would not have been possible for Hettinger County, a sparsely populated area with fewer than 2,600 residents. Through a comprehensive stakeholder engagement process, Barr helped secure 95 percent of the project’s funding from local, state, and federal agencies, resulting in a local cost share of less than 6 percent. Prior to the project, the community risked losing an important recreational area. With safety no longer a concern, future generations can enjoy the improved dam for years to come.

Barr provided assessment and remediation services to the site owner of a 100-acre, former wood-treating facility where creosote and pentachlorophenol had contaminated soil and groundwater. Working with state and federal regulatory agencies and agency partners to identify and select the most cost-effective soil and groundwater remedies, we conducted soil, groundwater, and site remedial investigations; evaluated human-health and ecological risks; studied the feasibility of remedial alternatives; supported the site owner in complex regulatory negotiations; and prepared plans and specifications for the proposed cleanup. Barr also helped the client prepare a submittal to the National Remedy Review Board and developed a supplemental feasibility study to evaluate alternatives further based on modified soil volumes.

For this project, more than 470 acres of aquatic and terrestrial habitat were investigated and 390 samples (water, sediment, soils, wild rice, plants, fish mussels, crayfish, and earthworms) were analyzed for contaminants such as dioxins, metals, semi-volatile compounds, and polychlorinated biphenyl (PCB) congeners. In all, Barr has analyzed more than 6,000 samples from this site since 1980.

The U.S. EPA is developing a Record of Decision based on the remedial investigations and feasibility studies that Barr developed for the site.

In 2013, the Minnesota Department of Natural Resources prioritized 12 sites in and around the St. Louis River for habitat restoration. The agency combined the Grassy Point and Kingsbury Bay sites into a single project to restore 240 acres of fish and wildlife habitat. As the DNR’s engineering consultant for the project, Barr began working with stakeholders in 2017 to design a project that included dredging, island building, and thin-layer sediment covers to restore habitats. Material reuse within and between project areas was critical in making best use of restoration funds. 

More than 100,000 cubic yards of sawmill waste lying at the bottom of Grassy Point was used to expand an island and create a shallow, sheltered bay. Another 100,000 cubic yards of organic-rich sediment from Kingsbury Bay was dredged to create deeper-water habitat and placed at Grassy Point to provide a fertile benthic environment.

Barr’s team performed an environmental investigation and used dredge-elutriate testing to confirm that removing and reusing the wood waste wouldn’t contaminate the site. We then performed hydrodynamic modeling to evaluate the restoration’s effect on the river’s behavior and hydraulic and hydrologic modeling to address potential erosion issues. We also conducted a geotechnical investigation and modeling to design a stable wood-waste island. During the final phase of work, completed in fall 2021, Barr provided construction administration, engineering, and quality control.

One of Barr’s borate mining clients was experiencing problems with the crystallizer system in its processing plant. The slurry piping had severely degraded and the evaporation circuit wasn’t functioning properly, and those issues were contributing to inconsistent operations and production.

Barr redesigned aspects of each circuit. Upgrading the slurry section included replacing the pump and redesigning the piping system for erosion resilience. For the evaporation section, we redesigned the overhead piping to automate the rate of cooling-water flow to the condensers and ejectors, and added a steam dryer to provide higher-quality steam to those components. We also redesigned the seal tank and adjacent piping to facilitate control of water flow and level.

Key to repairing and improving our client’s legacy systems were our decades of experience with slurry systems and our familiarity with state-of-the-art equipment, as well as our knowledge of how to size pipes to address settling velocity. In addition, Barr reduced the potential for erosion in the piping by incorporating sweep elbows; improved control of processes by adding automation; and contained construction costs by choosing specific couplings.

A section of Highway 1/169 between Ely and Tower, Minnesota, was realigned to improve safety and traffic flow. Construction required extensive earthwork and exposed rock from the 2.5-billion-year-old Soudan iron formation. The folded and faulted stone contained sulfide minerals that, when exposed to air and water, can generate acid rock drainage (ARD) that may adversely affect runoff water quality.

The Minnesota Department of Transportation (MNDOT) developed an acid-generating rock mitigation plan and hired Barr’s qualified professional geologists to oversee plan execution.

Barr sourced neutralizing amendment materials, including limestone and slaked lime byproduct, from the local paper industry. The project called for specific dosing of ARD-generating materials with amendments, and construction of a large-scale, long-term covered repository.

The geologists were on site daily to assess the materials’ acid-generating potential, collect samples for geochemistry analysis, refine volume estimates, and implement mitigation measures as needed. Our work helped ensure that excavated material remained within the mitigation plan’s safety factors. Close collaboration also helped keep construction on schedule while enabling MNDOT to better manage risk and understand the onsite implications of implementing an ARD mitigation plan.

The project was completed in 2018, and long-term monitoring indicates chemical and geotechnical stability of the ARD rock repository. The original mitigation plan and design project won awards from the Association of General Contractors as well as from MnDOT’s Office of Environmental Stewardship.

Barr has been assisting the RWMWD with repair and rehabilitation of the Beltline and Battle Creek stormwater tunnel systems for more than three decades. Constructed in 1925, the Beltline interceptor captures stormwater from two watersheds through a system of tunnels around 34,000 feet in total length. The Battle Creek system, built in 1982, conveys stormwater flow under the creek via 4,500 feet of tunnels.

Our inspectors, certified by the National Association of Sewer Service Companies (NASSCO), provide regular inspections of the tunnels. In 2015, we conducted a five-year inspection and condition assessment of the entire Beltline and Battle Creek storm tunnel systems. Using a NASSCO PACP inspection approach, we documented structural and operational/maintenance defects. We then used a coding system to assign numerical scores to condition defects based on their seriousness. Observations and defects were catalogued by location IDs linked to station numbers and clock position. Tunnel segments were then evaluated by condition ratings to identify and prioritize those most needing repair.

Barr then developed a rehabilitation design for approximately 16,000 feet of tunnel, including repair details and quantities. We also provided bidding and construction administration and full-time, on-site construction observation. Conducted in two phases over two years, the $4 million project was completed in 2018. Barr performs detailed inspections of the entire seven-mile storm tunnel system every five years.