NRG’s Harrisburg energy center (now owned by Clearway Energy Group) generates electricity for sale to a grid, and generates and distributes steam for space heating, domestic water heating, humidification, and industrial processes. In 2015, when one of the center’s two 200-foot-tall stacks was beginning to deteriorate and needed to be repaired or reduced in height, Barr was asked to conduct air dispersion modeling to demonstrate that even with a reduced stack height, the facility would remain in compliance with national ambient-air-quality standards (NAAQS).

To analyze the new operating scenario, Barr needed to set up the dispersion model to reflect not only emissions from the center’s four boilers and two internal-combustion engines, but also the site’s location in an urban area with several nearby buildings, other sources of air emissions, and a heavily trafficked elevated highway.

Our modeling results allowed for a 20-foot reduction in the stack height. During deconstruction, NRG determined that an additional 7 feet of stack needed to be removed due to deterioration. Barr provided supplemental modeling to show that despite the further reduction in stack height, the facility’s emissions would still meet the NAAQS permit limits.

The city of Blaine has 10 groundwater supply wells in its drinking-water system that are mostly used to supplement peak water demand in the summer. As part of the city’s effort to upgrade its water system, Barr evaluated the wells and wellhouse structures. We then worked with the city to develop a plan for rehabilitating the wells and replacing aging infrastructure.

Before this project, each well was housed in a wellhouse and pumped water either to a treatment plant or directly to distribution. Upgrades included new wellhouses, installation of pitless adaptors, and conversion of wells to emergency-standby status. Rehabilitation of six wells and one booster station was completed in 2023.

An earthen embankment of the Willow River Dam failed in 2016 during a large flow event resulting from rainfall in excess of seven inches in a 24-hour period. The Minnesota DNR, in consultation with the community of Willow River, elected to restore the upstream reservoir level by constructing a rock arch rapids to span the 13-foot elevation change between the reservoir and the downstream river. The rock arch rapids would improve site safety, provide upstream fish passage, and allow for small boat passage when conditions permit.

Barr performed detailed design and modeling for the proposed rock arch rapids, including development of a two-dimensional hydraulic model to evaluate flow velocity and shear stress under a variety of flow conditions. The hydraulic modeling allowed us to size the rapids appropriately to maintain stability during critical flow conditions. Because the rock rapids maintain upstream lake levels that existed previously, the rapids are classified as a dam by the DNR.

From an environmental perspective, the new “dam” represents a major improvement to the river ecosystem, while maintaining the upstream reservoir level. The dam consists of a series of rock rapids with large boulders that break up the flow and create ideal fish habitat. The rapids were designed to allow upstream migration of warm-water fish species while safely accommodating much larger flood flows than the old dam.

ALLETE Clean Energy, the current facility owner at Lake Benton windfarm, retained Barr and the Minnesota Department of Commerce when seeking to retrofit nearly 400 wind turbines at this site. As part of the retrofit, ALLETE Clean Energy applied for an amendment to the original 1998 site permit for windfarm construction and operation. Replacing turbine blades, gearboxes, and generators will boost turbine performance and reliability and extend the life of the facility. Additionally, new fiber-optic connections, servers, and data-acquisition and management systems will improve turbine efficiency and overall facility operations.

Barr’s assistance included reviewing threatened and endangered plant and wildlife species; conducting evaluations of sound levels; managing shadow-flicker studies; and analyzing the need to notify the Federal Aviation Administration of the proposed changes. Because Minnesota guidelines for turbine siting have changed since the original site permit was issued, we also evaluated the differences between the initial and new standards to provide our client with options for the permitting strategy.

The Minnesota Public Utilities Commission approved the partial-repowering permit—one of the first two such permits issued in the state.

When planar-type, wedge-type catchment and bench failures were found in a highwall at its Marinette Quarry, Specialty Granules LLC wanted to assess the highwall’s stability, identify potential hazards, and garner recommendations to achieve a stable slope and bench configuration for future mining operations at its Kremlin facility.

Barr conducted a comprehensive geotechnical assessment comprised of assessing highwall conditions; documenting joint conditions and orientation; using a high-definition laser scanner to collect topographic and rock-mass data; logging below the pit floor with an acoustic and optical televiewer; collecting rock specimens; and performing several analyses, including kinematic, general stability, plane and wedge failure, rockfall, berm offset, and bench configuration. Our in-depth assessment informed recommendations to the client for highwall and bench slope angles and configuration, best mining practices, and highwall monitoring.

Since 2011, Barr has been providing comprehensive environmental assistance at five terminals associated with the Superior refinery. The terminals, located in Minnesota and Wisconsin, are currently operated by Superior Refining Company (which is owned by Cenovus). As part of helping the on-site terminal staff understand regulatory and permit requirements and maintain environmental compliance, Barr developed and continues to maintain compliance action plans for the terminals. The plans cover compliance issues related to air, water, waste, aboveground storage tanks, oil-pollution prevention, site remediation, clean fuels, and EPCRA. Each plan:

As part of our ongoing environmental compliance support for these terminals, we review and update the compliance action plans as needed. We also discuss the plans with terminal staff during annual environmental training sessions.

After years of landslide activity along a portion of Highway 73 in the Missouri River Badlands, a repair was implemented but unsuccessful. The North Dakota Department of Transportation (NDDOT) turned to Barr and another consultant to permanently stabilize the roadway embankment. The soils at the site include high-plasticity clays with limited long-term shear strength and coal seams carrying groundwater that can contribute to slope failures.

We conducted a geotechnical field investigation, installing piezometers and inclinometers that could be read remotely to allow more frequent tracking of groundwater and slope movement and provide a better understanding of the problem. One inclinometer, developed by Measurand, Inc., was the first of its kind and capable of measuring larger displacements like those observed at the site.

The instrumentation data, combined with geologic field mapping and an extensive laboratory testing program, enabled us to better characterize the soils’ shear strength and determine the nature and extent of the landslide, including the significant impact that drainage conditions and water pressures had on movement. Instrumentation and site reconnaissance showed that the landslide was much larger than previously identified.

Testing and investigation results were used in seepage and slope-stability analyses to develop and assess stabilization options, which were presented to NDDOT. The option selected for final design involves installation of large-diameter concrete drilled shafts to pin the sliding mass on one side of the road and a deep interceptor trench to collect groundwater on the other.

The Highway 73 project won a 2020 Engineering Excellence Award from the American Council of Engineering Companies of North Dakota.

Built in the mid-1960s, the levee protecting the city of Hastings, Minnesota, has withstood several floods since its construction. To continue to accredit the levee, the Federal Emergency Management Agency (FEMA) contacted Hastings in 2008, requiring the city to document—with certification from a registered professional engineer—that its levee meets the requirements of the Code of Federal Regulations, Title 44, Section 65.10 (44CFR 65.10). The city partnered with Barr for a full review of the site characteristics, design, and construction.

To certify the levee, Barr’s team of geotechnical experts, structural engineers, and water resources scientists conducted data review and analysis; engineering analysis; operations, maintenance, and emergency action plans; and submission to FEMA.

Barr began by compiling all readily available data about the city of Hastings flood protection project including drawings, design calculations, and studies. Based on this information, Barr prepared a list of additional information required to meet the federal regulations, and then consulted directly with FEMA staff to finalize this list. Next, Barr performed all engineering analyses required for the FEMA accreditation, including freeboard review, review of closures, embankment protection analyses, embankment and foundation investigation and stability and seepage analyses, settlement analyses, and interior drainage review. Then, Barr worked closely with city staff to develop the necessary operations and maintenance manuals and an emergency action plan focused on the unique aspects of the city’s levee system.

Barr compiled the necessary engineering design studies, drawings, required forms, and certifications into a single document for submission and submitted the finished documentation on behalf of the city to FEMA. In consultation with the city, Barr responded to comments from FEMA or other reviewers and made the necessary revisions to the documentation that FEMA requested.

The dam of the Fort Peck hydroelectric project in Montana is the highest of six major dam facilities on the Missouri River. Flooding in 2011 caused a record release through the spillway, resulting in significant damage to the plunge pool and requiring emergency repairs and spillway rehabilitation. The Big Bend hydroelectric project in South Dakota, also on the Missouri River, experienced similar conditions during the flooding. As a subcontractor to J.F. Brennan, Barr provided inspections, structural and mechanical analysis, and design for gate repairs at both sites.

We performed visual structural inspections and nondestructive weld inspections for each gate as well as visual inspections of associated concrete surfaces and counterweights. Barr also conducted a finite-element analysis and designed a rehabilitation plan for each gate. To avoid budget overruns, Barr developed a gate-repair approach involving a tiered ranking system that included work such as crack repairs on fracture-critical members in upper tiers and weld undercut and underrun repairs on non-fracture-critical members in lower tiers. We recommended performing only the highest priority repairs initially and re-evaluating remaining tiers after half of the gates underwent repair. Ultimately, the approach was successful and resulted in a more appropriate use of funds.

In addition, Barr generated final repair plans and specifications for structural weld repairs, concrete surface repairs, ultrafine grout injection, and gate painting as well as replacement of structural steel sections, cathodic protection anodes, and gate seals.

To create an accurate inventory and provide site-specific maintenance recommendations for green-infrastructure stormwater sites, Barr assisted the City of Minneapolis with developing an operations and maintenance manual and associated contracting documents. In one comprehensive manual, Barr documented separate maintenance and operations requirements and calendars for 26 green-infrastructure sites under multiyear contracts. The manual focuses on erosion prevention, sediment management, and plant-community management needed to maintain these stormwater features as attractive neighborhood amenities. It also provides procedures for maintaining seven types of BMPs. In addition, Barr created specifications for sediment removal and plant-community management and assisted the city with obtaining qualified contractors. The easy-to-read manual provides site managers with quick assessment methods and procedures for yearly evaluation and ongoing maintenance of BMPs.