The Federal Energy Regulatory Commission (FERC) directed this confidential client to increase spill capacity at three of its hydroelectric facilities in order to pass the probable maximum flood (PMF). Barr performed a feasibility study to identify a cost-effective solution for modifying the plants to pass the PMF. We developed several possibilities for each plant, along with preliminary cost estimates.

For the first plant, the client selected Barr’s recommended plan to raise the embankment corewall and modify the tainter-gate spillway hoisting to increase the gate opening. The design was approved by FERC and constructed in 2008. In addition, we designed a downstream-embankment earthen buttress and concrete retaining wall to increase the embankment stability and meet FERC criteria for the PMF load case.

For the other two plants, Barr evaluated several major options, including constructing a new concrete spillway, installing a new headgate in an existing abandoned bay, and making significant modifications to the tainter-gate hoist. The work was initially estimated to cost hundreds of thousands of dollars, but by thoughtfully considering site features and conducting a detailed review of the hydraulics necessary to pass the required flow, we were able to develop a simplified plan that still achieved the primary goals of protecting the powerhouses from flooding and passing the PMF flow without overtopping the embankments. The design consisted of a small floodwall to divert some excess flow around the powerhouse and back to the river at the downstream end of the spillway. This solution cost a fraction of the amount of the original options. FERC approved the proposed plans and modifications, and construction took place in 2020.

Barr assisted the Floyd County Conservation Board with its efforts to remove a dam on the Shell Rock River in the city of Rockford. Constructed in 1872, the 7-foot-high dam no longer served a useful purpose and was deteriorating. Significant leakage was occurring below the dam, and it presented a hazard to swimmers and boaters. In 2010, the Iowa Department of Natural Resources declared the dam to be in a state of failure and recommended that it be either repaired or removed. The county, in consultation with the Iowa DNR and the U.S. Fish and Wildlife Service (USFWS), elected to completely remove the dam. The USFWS provided most of the funding for removal.

Barr assisted the DNR, which provided a grant for a portion of the project, with data collection efforts, and performed a baseline assessment of a historic, restored millhouse located on the river’s east side. The spillway was structurally connected to the millhouse foundation and great care needed to be exercised to separate the two without damaging the millhouse.

Barr developed construction plans and specifications for the dam’s removal, which included a grading plan for the west side of the channel to restore floodplain connectivity and bank vegetation. We also developed a monitoring plan for the historic millhouse, which included installing crack gauges and vibration monitoring equipment to monitor the millhouse foundation during construction, and performing pre- and post-construction surveys of the structure. Barr worked with a subconsultant to assist with the architectural documentation of the dam removal—a required permitting step due to the dam’s historic nature.

In early 2009, the city of Oslo, Minnesota, was notified by FEMA that its existing levee system needed to be recertified within two years to continue to be included in FEMA’s flood insurance program. The city hired Barr to evaluate the levee system, design remedial measures, obtain USACE approvals, provide construction management services, and produce the documentation necessary to achieve FEMA accreditation of the levee system. Barr’s experienced geotechnical team provided recommendations for cost-effective solutions to upgrade more than 2,000 feet of existing unstable riverbank which was identified as an USACE system deficiency.

Barr’s evaluation included review of available data, field investigations and inspections, and engineering analysis. The results indicated additional deficiencies in the levee system. Ultimately, the USACE’s periodic inspection resulted in an unacceptable rating of the levee system; failure to resolve the levee deficiencies within the tight timeline would place the entire city in the 100-year floodplain and virtually eliminate all possibility of future residential or commercial development. The required improvements included property acquisitions, addressing USACE deficiencies, raising significant portions and realigning portions of the levee, raising gatewells, modifying the existing pump station, utility penetration rehabilitation, roadway modifications, potable water tank replacement, and earthen road closures as well as constructing new levees and a railroad closure structure.

To remedy the known riverbank instability deficiency, the geotechnical project team implemented a subsurface investigation which included borings, piezometer and inclinometer installation, and monitoring. We used the data to perform computer modeling, including seepage and stability analyses for the proposed levee improvements with the software programs GeoStudio SEEP/W and SLOPE/W, as well as specialty modeling with FLAC. The project implemented 2,800 feet of new levee construction, raising 13,500 feet of the existing levee, over 300 feet of floodwall, railroad closure structure across Canadian Pacific Railway tracks, existing pumping station improvements, new tractor driven pump station, seepage mitigation, property acquisitions, and public infrastructure improvements.

Barr provided engineering support, technical oversight, and on-site construction oversight during construction. We managed safety plans, progress reporting, progress monitoring, pre-inspections, and schedules. We developed and followed quality management procedures to support evaluation of levee, utility, street enhancements, pump station modifications, structural improvements, and other construction activities.

We ultimately developed a design documentation report, construction report, as-built and record drawings, and the FEMA 44 CFR 65.10 tabbed submittal needed for FEMA accreditation. Barr also developed a new operations and maintenance manual for the entire rehabilitated flood-risk management system in accordance with USACE criteria and as a requirement of the Section 408 approval. The plan was approved by the USACE and submitted to FEMA meeting the project end goal of levee system accreditation.

Barr completed a total maximum daily load (TMDL) study of Nine Mile Creek in the southwest suburban area of Minneapolis. The study was conducted in cooperation with the Minnesota Pollution Control Agency (MPCA) for the Nine Mile Creek Watershed District. The creek was listed on the MPCA’s impaired-waters inventory for turbidity levels exceeding the Class 2B water quality standard of 25 NTUs (nephelometric units—turbidity is measured as the amount of light scattered in a water sample and reported as NTUs). The creek is also listed for chloride and fish index of biotic integrity (IBI). In response to these impairment listings, the watershed district authorized comprehensive stream and watershed assessments that include extensive field data collection followed by computer simulation and mass-balance modeling of streamwater-quality conditions to assess the management practices that must be implemented to restore the creek to compliance with MPCA standards.

The first phase of work involved characterization of stream hydrology and water-quality conditions, including chemical and biological water quality. Barr surveyed the physical characteristics of the stream according to the Rosgen stream classification system and installed three continuous-flow-gaging and automatic-sampling stations on the main stem and branches of the creek. We’re conducting year-round continuous discharge monitoring and episodic water-quality sampling—both baseflow and stage-activated storm event—for a wide variety of water-quality constituents. We’re also concurrently studying stream habitat and the benthic macroinvertebrate and fish communities of the creek to determine any possible biotic impairments related to urban stormwater runoff and road salt applications. Following MPCA protocols for fish-community sampling and physical habitat assessment for wadeable streams, Barr completed fishery surveys for the development of the Index of Biotic Integrity (IBI) scores throughout the watershed. The Nine Mile Creek Watershed District, MPCA and Barr completed a total TMDL analysis of Nine Mile Creek and its watershed to address the fish IBI listing on the MPCA’s Section 303(d) Impaired Waters list. Barr collected continuous turbidity data to show that the creek should be de-listed for turbidity. Working with data collected by our staff and the Metropolitan Council, Barr has prepared the watershed and stream characterization, stressor identification, and causal analysis/diagnosis for the biological impairments.

A detailed computer model (i.e., XP-SWMM) has been developed to simulate stream hydrology and its effect on aquatic habitat. Calibrated to observed conditions, this model can be operated in “what if” mode to evaluate the benefits of implementing various watershed best management practices (BMPs) designed to reduce the rates and volumes of watershed runoff. Stakeholder meetings were organized and conducted to inform interested parties about TMDL study progress and to gather public input about proposed BMPs. In addition, mass-balance modeling and a TMDL report for chloride was developed/approved and implementation planning was completed.

At the West Elk Mine (an underground coal-mining operation on the western slope of the Colorado Rockies), the first indication of unstable slope conditions occurred during construction of the mine portals in 1980, and was thought to be localized and shallow. In early 1997, the landslide moved more than a foot in three months. Calculations showed that it was accelerating, threatening the mine facilities downhill. The Mountain Coal Company initiated an emergency action plan and asked Barr to investigate the landslide and design mitigation measures.

Barr’s team characterized the extent of the slide and the depth of the slide failure plane, as well as the area’s soil and groundwater, and determined that the slide was massive. We confirmed that groundwater was a key factor, so extensive dewatering measures were designed and constructed to provide long-term stability.

To reduce the immediate momentum of the slide, we designed a network of flexible steel pins. Typically, rigid pins anchored in bedrock would be used to stabilize a landslide, but these would be sheared off by the mass of this slide. Barr’s design uses pins made of steel pipe, which flex to prevent them from breaking while still resisting the landslide forces. Rather than being embedded in bedrock, the pins tie the faster-moving upper soil layer to the slower-moving layer below to provide a braking force. We continue to monitor and evaluate the landslide and have contingency plans ready if it reactivates.

Quick response facilitates cleanup at airport

In 2014, jet fuel was identified in an airport’s stormwater-sewer pumphouse, leading to discovery of a release from the airport’s hydrant line. Because of our experience successfully investigating and remediating releases for the airline in other locations, Barr was hired to immediately mobilize a team to determine potential exposure risks and the extent of impacts and to guide development of an investigation and remediation strategy.

Our preliminary investigation included assessing contaminant migration pathways, evaluating jet fuel in an airport-dewatering sump and a nearby elevator shaft, conducting indoor-air screening and risk assessment, and evaluating the integrity of adjacent sewers. We then performed a phased investigation involving sump sampling, installation of soil borings and groundwater monitoring wells, and evaluation of vapor intrusion and indoor air quality. Response actions included installation of horizontal and vertical product-recovery wells, pressure grouting and sealing of exterior walls where infiltration was observed, sump-pump modifications, and a soil-vapor-extraction pilot test.

Throughout the project, our activities were coordinated with the airport to minimize impacts on routine operations. The site received a certificate of completion of remedial activities from state regulators in 2021. Barr continues to assist the client with ongoing operations-and-maintenance activities.

Barr has been measuring per- and polyfluoroalkyl substances (PFAS) in stack emissions at facilities in the U.S. for two decades. Because of this experience, a confidential manufacturing client hired Barr to perform compliance testing to evaluate the performance of thermal oxidation as a best available control technology (BACT) to control PFAS emissions from its processes.

Barr conducted stack testing for EPA OTM-45, Method 25A hydrocarbons, 26A hydrogen fluoride, and EPA 204 capture efficiency. We wrote the test plan, performed testing, and prepared the report. The test results satisfied all permit requirements. The determination of BACT and incorporation of PFAS emission limits in the permit was among the first such instances in the U.S. and was based on the potential to cause or contribute to surface or groundwater contamination.

Our experience in this area dates back more than 20 years, when we participated in an industry-wide mass balance study to measure air, water, and solid waste releases of PFOA (perfluorooctanoic acid, a type of PFAS) to the environment from 2003 to 2005. The study involved the development of sampling methods with full Quality Assurance Project Plans (QAPP). During the study, Barr’s stack test engineers developed an early version of modified Method 5 that was accepted by the EPA in the study docket.

Subsequently, Barr conducted stack tests to evaluate emissions, control-device effectiveness, and emission reduction due to reformulation of input materials to manufacturing processes. Barr has also performed indoor air quality and ambient air measurements for PFAS compounds.

Our work contributed to the development of OTM-45, published in January 2021 through submission of a separate and complete set of stack samples to EPA-ORD to further method development. Barr’s stack test emissions data has been used as input to air, soil, and hydrogeologic modeling to understand PFAS fate and transport as well as the impact of air emissions on surface and groundwater.

Learn more about our PFAS engineering and environmental capabilities.

Outside counsel for a Fortune 500 manufacturing company hired Barr to conduct audits at 35 facilities across the U.S. for compliance with water-discharge requirements at the federal, state, and local levels, including NPDES, stormwater, and industrial-pretreatment permits.

The broad objective was to identify known and potential liabilities associated with operations involving specified media at each plant, including screening for the presence of emerging contaminants and addressing compliance with new and pending regulations.

Within 18 months, our team completed audits at all 35 sites, despite having to reschedule some visits on short notice when competing priorities at certain plants required that.

Working remotely, Barr team members reviewed each facility’s manufacturing processes and chemical usage to deter-mine whether plant operators were accurately characterizing and appropriately disclosing water-related discharges. In addition, we reviewed relevant permits, monitoring data, compliance records, inspections, notifications, and change-management procedures. Subsequently, small teams of engineers and scientists visited each facility to observe conditions and develop recommendations.

For each facility, Barr prepared an assessment report detailing:

When requested, Barr also evaluated facilities’ pretreatment programs and stormwater pollution-prevention plans (SWPPPs), supplying technical memos afterward with findings and recommendations for each facility.

The scope of the detailed audits encompassed reviewing not only permits, facility plans, compliance records, and on-site operations, but also historical regulatory applicability and archived records of sampling results. In addition, Barr interviewed facility staff, and in some cases, to facilitate site walkdowns, we prepared process and layout drawings for facilities with missing or incomplete drawings. Our teams:

To promote quality assurance and quality control, Barr developed measures for audit completeness, uniformity of process, consistent presentation of information, and quality of final deliverables. We established audit and interview templates, report consistency guidelines, and data inventories to be followed for each audit. For each facility, a customized assessment table was generated that itemized all conditions and requirements to be reviewed based on federal, state, and local requirements, as applicable.

In addition, to foster systematic documentation of all issues, Barr compiled a comprehensive database of recommendations by facility, categorizing findings, observations, and program risks (e.g., wastewater, stormwater, product storage). We also created a list of issues common among the facilities to help our client efficiently address improvements.

Finally, two Barr technical team members reviewed each final deliverable for content accuracy, completeness, and document quality.

We presented audit findings and recommendations to our client’s corporate and outside counsel, discussing documented and potential areas of noncompliance that could have significant impacts on business operations. For each site, we provided final reports listing corrective actions.

In 2017, the City of Prior Lake hired Barr to prepare a FEMA letter of map revision (LOMR) application, using the calibrated PCSWMM model Barr completed in 2016 for the Prior Lake-Spring Lake watershed flood mitigation study. The PCSWMM model showed a two-foot reduction in the flood elevation of Upper and Lower Prior lakes. With an approved LOMR, numerous properties and homes would no longer be in the floodplain, and property owners would no longer be required to purchase flood insurance.

Barr obtained the Inter-Agency Hydrologic Review Committee’s approval of the PCSWMM model, prepared and submitted the LOMR paperwork (including the four required versions of the PCSWMM model), responded to FEMA questions, prepared materials for and attended a public open house, and helped the city answer questions from property owners. The LOMR took effect in July 2018. 

Barr also assisted with subsequent work, including analyzing the potential impact on flood elevation of filling the remaining parcels in the floodplain with homes, as well as notifying individual property owners regarding their flood insurance status.

Responding to a sandstone abutment failure improves dam safety

In 2011, erosion and rock slides created a shortened seepage path around an existing sandstone abutment at the Dells Hydroelectric Generating Station. This was identified as a Category I Potential Failure Mode. After working with Barr to inspect the freshly exposed rock faces, Xcel’s project team decided to extend the abutment wall upstream to stabilize the adjacent sandstone wall and extend the seepage path around the abutment.

Barr first conducted an options evaluation summarizing the potential dewatering methods and wall configurations available to create the abutment wall extension. After Xcel selected an option with a downstream seepage-collection system, we collected bathymetry data upstream of the abutment and used it to create a 3D model of the rock surface. Our design included the use of vertical soldier piles with post-tensioned tiebacks drilled 15 to 20 feet into the underlying sandstone. This allowed the reinforced concrete wall to be installed without the need for dewatering or a reservoir drawdown. Barr’s structural and geotechnical engineers finalized the drawings and technical specifications. We also provided construction support that included real-time monitoring of abutment movements in order to maintain dam and personnel safety.