Auburn University Samuel Ginn College of Engineering

National Center for Additive Manufacturing Excellence

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Methodology Development for Evaluating Inlet Protection Practices (IPPs) Using Large-Scale Testing Techniques

Perez, M.A., Zech, W.C., Donald, W.N. and Fang, X. | 2014 | Most roadway construction projects disturb existing vegetation exposing bare soil to environmental variables (i.e., precipitation, wind, and freeze and thaw) that cause erosion. Soil eroded during storm events is conveyed by storm water runoff and may become deposited in receiving waterways. Inlet protection practices (IPPs) are temporary erosion and sediment controls commonly used around inlet drainage structures to prevent erosion while also retaining sediment on-site. Effective IPPs impound storm water, prevent upstream channel erosion, and promote settling along the perimeter of a device. Stringent effluent regulations coupled with greater public awareness with regards to surface water pollution have created the need for understanding the performance of commonly used erosion and sediment control practices. This study developed a methodology and testing apparatus for large-scale reproducible performance-based testing of standard IPPs at the Auburn University Erosion and Sediment Control Testing Facility. A two-phased testing protocol comprised of installation improvements and performance evaluations was developed. A test channel, 13.42 m (19 ft) in length, 5.80 m (19 ft) in width, sloped at 5% towards a 1.22-m (4 ft) inlet was constructed to test IPPs. Using the Alabama rainfall and erosion characteristics, water and sediment delivery mechanisms were designed and developed for implementing experimental flows and sediment introduction rates of 0.035 m3/s (1.25 ft3/s) and 21.2 kg/min (46.7 lb/min), respectively. Data collection includes pretest and posttest channel surveys, flow-through rates, total suspended solids, and turbidity. Finally, a case study using a typical wattle barrier IPP demonstrates the developed testing methodologies, installation improvements, and performance measures.

Compute Critical and Normal Depths of Arch and Elliptical Pipes

Perez, M.A., Butler, C.G., and Fang, X. | 2015 | Arch and elliptical pipes are commonly used as roadway culverts. The pipe section is composed of three radii, which result in complex equations to compute cross-sectional geometry and hydraulic parameters, such as normal and critical depths. Basic sizing charts do not allow direct calculation of hydraulic properties of these pipe sections. Therefore, general formulas were developed to compute hydraulic properties for any given arch pipe cross section. An Excel workbook capable of calculating normal and critical depths for given flow rates was created using the developed formulas and the solver function. Worksheets to compute geometric properties and water surface profiles using the direct-step method were also developed. These user-friendly worksheets are useful for hydraulic design and analysis of arch and elliptical culverts. A case study was conducted on several standard pipe geometries to demonstrate the comparative results from the developed workbook and existing sizing charts.

Using Unmanned Aerial Vehicles (UAVs) to Conduct Site Inspections of Erosion and Sediment Control Practices and Track Project Progression

Perez, M.A., Zech, W.C., and Donald, W.N. | 2019 | Construction activities increase the erosion potential of a site through earth-disturbing processes of vegetative grubbing, topsoil stripping, and grading. Receiving waters become susceptible and vulnerable to the process of sedimentation, which degrades the overall water quality. Federal, state, and local regulations require the use of erosion and sediment controls to help manage stormwater discharge from construction sites. Regulations further require regular inspections, monitoring, and maintenance of employed erosion and sediment control practices. Unmanned aerial vehicles (UAVs) are an emerging remote sensing tool capable of acquiring high resolution spatial and sensing data. Remote sensing with UAVs has the potential to provide high-quality aerial imagery and data that can assist in site inspections of erosion and sediment control practices and monitoring project progression. UAVs are economical and flexible in acquiring aerial data and can be preprogrammed with flight paths to capture data over construction sites objectively. UAV-based remote sensing enables user-controlled image acquisition and bridges the gap in scale and resolution between ground observations and imagery acquired from conventional manned aircraft and satellites. This research describes the application of UAV technologies for construction site inspections of erosion and sediment control practices and tracking project progression. A case study was performed on an active residential construction site with a commercially available UAV to showcase its application and capabilities of enhancing the site inspection process and construction monitoring.

Evaluation and Modification of Wire Backed, Nonwoven Filter Fabric Silt Fence for use as a Ditch Check

Donald, W.N., Zech, W.C., Perez, M.A., and Fang, X. | 2015 | Construction activities require contractors to install, continuously monitor, and maintain controls to minimize erosion and sediment transport. Construction sites discharge up to 100 times more sediment per acre than agriculture land activities because of mechanized compaction of bare soils that decreases infiltration capacity, increases runoff volumes, and increases erosion potential. Silt fence perimeter controls are widely used by the construction industry to intercept and impound stormwater runoff sheet flow, forming large impoundment areas ideal for sedimentation. Ditch checks are often used to minimize channel erosion and promote sedimentation in conveyance channels through runoff impoundment. Structural failures of silt fence have caused many state agencies to exclude their use in concentrated flows. Researchers at the Auburn University-Erosion and Sediment Control Testing Facility (AU-ESCTF) have evaluated the use of wire backed, nonwoven geotextile silt fence as ditch checks using large-scale testing techniques. This research has shown that silt fence, properly installed, can be used as a ditch check successfully. A longevity test of an enhanced silt fence ditch check installation resulted in sediment retention of 91.2% by volume.

Design Methodology for the Selection of Temporary Erosion and Sediment Control Practices based on Regional Hydrological Conditions

Perez, M.A., Zech, W.C., Donald, W.N., and Fang, X. | 2016 | Construction-related activities typically disturb established vegetation, resulting in the potential for accelerated erosion. Because of the associated water quality impacts of construction activities, the USEPA has established regulatory programs to manage stormwater runoff emanating from construction sites. Currently, designers typically rely on “rules of thumb” for the design and selection of temporary erosion and sediment control practices. To provide a hydrologically sound approach, this research developed a quick and direct sizing method based on Technical Release–55 methodology. The analysis focused on Type-II and Type-III rainfall distributions, with 171 hydrological simulations performed. The results yielded applicable equations for the determination of flow rates representative of regional conditions for a typical 0.405-ha (1.0-acre) roadway median drainage basin. Geographical information system (GIS) analyses were used to develop and analyze regional hydrological characteristics. The GIS modeling results showed the average 2-year, 24-h rainfall depth and soil curve number for newly graded developing urban areas in the state of Alabama to be 11.3 cm (4.43 in.) and 88.5, respectively. Multiple linear regressions were performed on simulated data to develop equations to calculate expected total storm volume, peak flow rate, and average flows for 30-, 60-, and 90-min peak volumes based on regional input rainfall parameters and a weighted curve number. The developed relationships reported low standard errors when compared with a complete hydrologic analysis. Designers can implement these regression relationships as design aids in selecting and sizing appropriate runoff control practices for projects under consideration when developing

Installation Enhancements to Common Inlet Protection Practices (IPPs) using Large-Scale Testing Techniques

Perez, M.A., Zech, W.C., Donald, W.N. and Fang, X. | 2019 | Inlet protection practices (IPPs) are temporary erosion and sediment controls commonly used in active construction sites to help reduce off-site transport of sediment. The overall in-field performance of these practices is commonly misunderstood. This study researched common failure modes of IPPs with the use of large-scale, channelized flow experiments. Testing evaluated the performance of standard IPP design details and provided installation enhancements to four typical practices commonly used in the erosion and sediment control industry (aggregate, sandbag, silt fence, and wattle barriers). Installation enhancements focused on providing effective structural improvements with typical installation materials while also considering reduced installation efforts and material costs. Enhancements increased IPP's impoundments while maintaining efficient dewatering times. Variations of practices from state agency design guides and comparisons of developed installation enhancements were presented. A performance and cost comparison was developed for practitioners to use when comparing improved IPPs.

A Hydraulic Method to Evaluate the Performance of Ditch Check Practices and Products

Donald, W.N., Zech, W.C., Fang, X., and Perez M.A. | 2016 | Erosion and sediment control products have become an integral part of the construction industry as manufacturers now provide innovative alternatives to traditional practices. Ditch checks are used on construction sites to intercept channelized stormwater runoff to reduce flow velocity, minimize channel erosion, and promote sedimentation. A standardized metric is needed to evaluate the performance of various ditch check practices. Comparative analyses are difficult in the field and in large-scale testing environments because conditions can vary greatly. A hydraulic-based metric to evaluate performance was developed by researchers at the Auburn University-Erosion and Sediment Control Testing Facility (AU-ESCTF). This metric is based on hydraulic conditions created by a ditch check to slow flow velocity and transform kinetic energy to potential energy. Using the ratio of water depth (y) to specific energy (E), the average performance can be quantified and compared with counterparts and traditional practices, even if data were developed under different flow conditions or channel geometries. While using the y/E ratio to determine kinetic energy reduction, a nonsubjective performance threshold of y/E=0.75 emerged.

Methodology and Development of a Large-Scale Sediment Basin for Performance Testing

Perez, M.A., Zech, W.C., Fang, X, and Vasconcelos, J. | 2016 | Stormwater regulations require construction-generated pollution to be controlled on-site prior to discharge to avoid impairment of receiving waterbodies. Sediment basins are stormwater detention practices commonly used to capture and treat sediment-laden runoff prior to discharging from a construction site. Federal and state highway and environmental protection agencies have developed standardized guidance on the design of sediment basins, however further research is necessary to understand basin performance under various design conditions using large-scale testing techniques. This study details the design and construction of a 79.0 m3 (2,790 ft3), large-scale sediment basin at the Auburn University Erosion and Sediment Control Testing Facility (AU-ESCTF). A testing methodology and phased experimental regime were developed to allow for future testing of various sediment basin design configurations and high-rate lamella plate settler technology within the basin. Data collection efforts including water quality, flow rates, basin stage levels, sediment deposition volumes, and sediment sampling for particle characterization will be used to evaluate the performance of various basin design configurations. Preliminary results from basin testing for the effectiveness of an excavated sump are presented to demonstrate the developed test method. Water-quality parameters revealed improvements ranging between 150 and 200 Nephelometric Turbidity Units (14.0–18.6%) when an excavated sump was included in the forebay of the system. Sediment collection showed that the improved system allowed for an additional 4.3% of sediment deposition by mass. This research effort and future testing results will allow practitioners to better understand the performance of current sediment basin designs and for providing operational improvements.

SEDspread: A Sediment Basin Design Tool for Construction Sites

Perez, M.A., Zech, W.C., Donald, W.N., and Fang, X. | 2016 | Sediment runoff rates from construction sites can be substantially higher than those of other land uses. Construction stormwater regulations require detailed stormwater pollution prevention plans to minimize environmental impacts associated with construction activities. Sediment basins are temporary sediment control measures used to detain and treat stormwater runoff on-site prior to discharge. This study developed SEDspread, a user-friendly spreadsheet-based design tool for designers to appropriately size temporary sediment basin parameters. The workbook allows users to input site-specific parameters and constraints to determine basin capacity and configuration, surface skimmer size and dewatering rate, auxiliary spillway design, and baffle configuration. The workbook includes a summary sheet that provides users with schematics of the designed basin, available as a supplement to facilitate effective communication between designers and contractors for constructing and installing the basin. SEDspread includes geospatially derived and referenced data that allow for automated selection of design hydrologic and soil conditions through the input of a project location’s U.S. ZIP code. A hydrologic analysis was performed to relate input hydrologic and soil parameters to 2-year, 24-h design volume sizing factors to contain all design storm runoff. To showcase the capabilities of the developed workbook, a case study was performed to compare the actual designs of two construction site sediment basins to the designs generated through SEDspread. The case study resulted in a volumetric difference factors of 3.0, indicating the basins were severely underdesigned for the local 2-year, 24-h design rainfall.

Improvements in Standardized Testing for Evaluating Sediment Barrier Performance: Design of a Full-Scale Testing Apparatus

Bugg, R.A., Donald, W.N., Zech, W.C., and Perez, M.A. | 2017 | Perimeter controls [i.e., sediment barriers (SBs) or sediment retention devices] are typically used on construction sites to retain sediment and prevent polluted stormwater runoff from adversely affecting aquatic habitats and clogging storm sewers. Often, parameters based on rule-of-thumb are applied to the design of SBs without knowing their expected performance capabilities. This issue is further complicated by the difficulty in devising a scientifically sound, repeatable testing methodology, replicating field conditions to assess performance. To resolve this issue, a test apparatus was designed and constructed at the Auburn University—Erosion and Sediment Control Test Facility to replicate in-field rainfall runoff rates for purposes of conducting full-scale experiments on various SBs. This apparatus allows for performance testing and direct comparisons between various SB products, practices, and installations. The overall intent of conducting full-scale testing is to improve design criteria and enhance the in-field performance of SB practices. Initial test results for a woven polypropylene silt fence reinforced with a polypropylene grid and supported by wooden posts performed well structurally with an average sediment retention rate of 90.5% by volume.

Performance Evaluations of Three Silt Fence Practices Using a Full-Scale Testing Apparatus

Bugg, R.A., Donald, W.N., Zech, W.C., and Perez, M.A. | 2017 | Erosion and sediment controls on construction sites minimize environmental impacts from sediment-laden stormwater runoff. Silt fence, a widely specified perimeter control practice on construction projects used to retain sediment on-site, has limited performance-based testing data. Silt fence failures and resultant sediment losses are often the result of structural failure. To better understand silt fence performance, researchers at the Auburn University-Erosion and Sediment Control Testing Facility (AU-ESCTF) have evaluated three silt fence options to determine possible shortcomings using standardized full-scale testing methods. These methods subject silt fence practices to simulated, in-field conditions typically experienced on-site without the variability of field testing or the limited application of small-scale testing. Three different silt fence practices were tested to evaluate performance, which included: (1) Alabama Department of Transportation (ALDOT) Trenched Silt Fence, (2) ALDOT Sliced Silt Fence, and (3) Alabama Soil and Water Conservation Committee (AL-SWCC) Trenched Silt Fence. This study indicates that the structural performance of a silt fence perimeter control is the most important performance factor in retaining sediment. The sediment retention performance of these silt fence practices was 82.7%, 66.9% and 90.5%, respectively. When exposed to large impoundment conditions, both ALDOT Trench and Sliced Silt Fence practices failed structurally, while the AL-SWCC Trenched Silt Fence did not experience structural failure.

Design and Construction of a Full-Scale Testing Apparatus for Evaluating the Performance of Catch Basin Inserts

Basham, D.L., Zech, W.C., Donald, W.N., and Perez, M.A. | 2018 | As stormwater runoff flows over impervious surfaces, it suspends and transports various pollutants from their original locations and often conveys them into municipal separate storm sewer systems (MS4s). Most municipalities and state highway agencies in the United States have developed stormwater management guidelines to ensure compliance with the EPA’s MS4 standards, including allowable methods and practices to remove pollutants from stormwater influent flowing into MS4s. Catch basin inserts (CBIs) have become an increasingly popular option for pollutant removal from stormwater. However, limited data are available to ensure that these practices meet required treatment standards. This study details the design, construction, calibration, and validation of an apparatus for full-scale testing of CBIs. CBI testing is designed to evaluate total suspended solids (TSS) removal efficiency reduction at three flow rates, 1.7, 3.4, and 5.1 L/s (0.06, 0.12, and 0.18 ft3/s), at an influent concentration of 450 mg/L (0.028 lb/ft3). Testing of a nonproprietary CBI revealed that the device removed 62.1%, 65.1%, and 51.7% of sediment introduced and reduced average TSS by 57%, 53%, and 49% over flow rates tested, respectively.

Large-Scale Performance Testing of Temporary Sediment Basin Treatments and High-Rate Lamella Settlers

Perez, M.A., Zech, W.C., Vasconcelos, J.G., and Fang X. | 2019 | Sediment basins are temporary practices commonly used to detain stormwater runoff and capture suspended sediment on construction sites. A 79.0 m3 (2790 ft3) sediment basin testing apparatus at the Auburn University—Erosion and Sediment Control Testing Facility was used to provide a series of controlled and repeatable, large-scale tests to understand the performance of sediment basins and provide improvements. This research evaluated five sediment basin configurations over the course of 27 individual tests, including: (1) a standard configuration, (2) the addition of an excavated sump upstream of a ditch check, (3) the modification of the first baffle, (4) a high-rate lamella settler in upward flow, and (5) a high-rate lamella settler in parallel flow. The primary metric for evaluating performance and the treatment effectiveness of a configuration’s ability in capturing sediment was assessed from turbidity measured across the basin surface. Multiple linear regression analysis indicated that an excavated sump provided insignificant improvement in sediment capture effectiveness. Furthermore, the modification to the first baffle was deemed ineffective in improving treatment efficiency. Lamella settler results indicated a 18.2% and 29.0% reduction in turbidity across the basin for upward and parallel flow configurations, respectively.

Design of a Pressurized Rainfall Simulator for Evaluating Performance of Erosion Control Practices

Ricks, M.D., Horne, M.A., Faulkner, B., Zech, W.C., Fang, X., Donald, W.N., and Perez, M.A. | 2019 | Construction site erosion and resulting sedimentation constitutes one of the greatest non-point source pollution threats to our nation’s waterways. Erosion control practices are important aspects of any construction project due to their ability to limit the process of erosion. Testing erosion control practices under simulated rainfall representative of conditions experienced on construction sites is important to better understand their erosion reduction capabilities. Full-scale testing using simulated rainfall has been shown to provide controllable and repeatable results, in comparison to field-testing under natural conditions. Therefore, the focus of this study was to design, construct, and calibrate a pressurized rainfall simulator testing apparatus capable of accurately and repeatedly simulating rainfall intensities of 50.8, 101.6, and 152.4 mm/hr (2.0, 4.0, and 6.0 in/hr) for 20-min intervals. The developed testing apparatus consisted of a 12 m (40 ft) long by 2.4 m (8.0 ft) earthen slope at a 3H:1V slope. Ten sprinkler risers at a height of 4.27 m (14 ft) were installed around the perimeter of the slope to create a uniform distribution of rainfall. Data collection procedures consisted of collecting and analyzing rainfall depth, drop size distributions, and sediment concentrations. The optimum location for each sprinkler riser, as well as the most accurate nozzle configuration, were determined through test procedures developed for this study. Through calibration testing, the simulator was found to produce accurate rainfall intensities with relative errors of 1.17–4.00% of the target intensities. Uniformity of rainfall distribution ranged from 85.7 to 87.5%. Average drop sizes were determined to be between 2.35 and 2.58 mm (0.093 to 0.102 in.).

Transferring Innovative Erosion and Sediment Control Research Results into Industry Practice

Perez, M.A., Zech, W.C., Donald, W.N., Turochy, R.E., and Fagan, B.G. | 2019 | Erosion and sediment controls (ESCs) are essential components of construction projects in minimizing downstream environmental impact. Since 2014, the Auburn University—Erosion and Sediment Control Testing Facility has hosted training events focused on disseminating results of innovative construction stormwater research to practitioners to help close the gap between research results and implementation. The purpose of training is to provide participants with the opportunity to learn about various practices used in construction settings to manage stormwater runoff. The result is increased knowledge of stormwater management which will translate into better protection of water resources. The facility has the unique capability of producing flows to simulate runoff typical of construction activities using research apparatuses, allowing attendees to understand how devices react when subject to field-like runoff conditions. The facility has provided training through a total of nine offerings with 764 participants. The purpose of this manuscript is to evaluate the effectiveness of the delivery style of these courses in providing technology transfer to industry professionals. In distributed surveys, attendees were asked to rank their level of knowledge prior to and after attending the training programs in ten specific focus areas covered during training. Overall, knowledge measurements indicated that technical knowledge level was improved across all measured areas with an average increase in perceived knowledge of 82% for a 1.5-day hands-on installer training event and 36% for a 1-day field day.

Evaluation of Lamella Settlers for Treating Suspended Sediment

Liu, L., Perez, M.A., and Whitman, J.B. | 2020 | Stormwater quality management has become an increasingly important topic. Pollutants from construction, urban, and agricultural runoff sources create adverse water quality impacts to receiving water bodies. Among these sources, suspended sediment has a significant influence on water quality and further acts as a media for transporting pollutants. Current stormwater treatment practices remove large, rapidly settable, soil particles; however, fine soil particles tend to remain suspended and contribute to elevated turbidity conditions. A need exists for an economical and passive treatment mechanism for the removal of suspended solids. Lamella settlers have been shown to enhance soil particle capture by increasing surface area and reducing settling distance. The objective of this research was to identify and optimize design configurations for a lamella settler system in treating a variety of synthetic soils. Five types of synthetic soils suspended in simulated stormwater at 500, 1000, and 5000 mg/L concentration were treated using system configurations of three lamella settler reactors at 0.5, 1.0, and 1.5-h residence times. Statistical analyses through a full factorial method followed with a regression analysis and analysis of variance (ANOVA) test suggested that there was a significant difference exists between these experimental variables and turbidity levels. An optimized lamella settler reactor providing 1.8 cm (0.7 in.) settling space with 1.5-h residence time reduced turbidity by up to 90% when compared to a control reactor without lamella plates and a 0.5-h residence time. In addition, particle size distribution analysis indicated a decrease in the D90 by up to 84%, which showed that the optimized reactor was effective in capturing larger diameter soil particles.

Improving the Effectiveness of Saturated Riparian Buffers for Removing Nitrate from Subsurface Drainage

McEachran, A., Dickey, L., Rehmann, C., Perez, M.A., Rutherford, C., Goth, T., and Isenhart, T. | 2020 | A saturated riparian buffer (SRB) is an edge-of-field conservation practice that reduces nitrate export from agricultural lands by redistributing tile drainage as shallow groundwater and allowing for denitrification and plant uptake. We propose an approach to improve the design of SRBs by analyzing a tradeoff in choosing the SRB width, and we apply the approach to six sites with SRBs in central Iowa. A larger width allows for more residence time, which increases the opportunity for removing nitrate that enters the buffer. However, because the SRBs considered here treat only a portion of the tile flow when it is large, for the same difference in hydraulic head, a smaller width allows more of the total tile flow to enter the buffer and therefore treats more of the drainage. By maximizing the effectiveness of nitrate removal, defined as the ratio of total nitrate removed by the SRB to total nitrate leaving the field in tile drainage, an equation for the optimal width was derived in terms of soil properties, denitrification rates, and head difference. All six sites with existing SRBs considered here have optimal widths smaller than the current width, and two are below the minimum width listed in current design standards. In terms of uncertainty, the main challenges in computing the optimal width for a site are estimating the removal coefficient for nitrate and determining the saturated hydraulic conductivity. Nevertheless, including a width that accounts for site conditions in the design standards would improve water quality locally and regionally.

Practical Silt Fence Design Enhancements for Effective Dewatering and Stability

Whitman, J.W., Perez, M.A., Zech, W.C., and Donald, W.N. | 2020 | Many of today’s construction sites rely on perimeter control practices to capture and treat sediment-laden stormwater emanating from disturbed lands. Silt fence systems are a common sediment control practice often specified by stormwater designers to be installed as perimeter control applications. Although design considerations are often given to the location and placement of these systems within the boundaries of a site, design characteristics of the silt fence itself (e.g., post size, post spacing, and fence height, among others) are rarely taken into consideration. As a result, silt fence systems often become overloaded and fail due to insufficient support or lack of effluent flow capability. Thus, this research effort sought to identify and evaluate practical methods for managing the discharge of impounded stormwater and improving the structural stability of silt fence systems. Results from full-scale testing suggest the inclusion of a plywood dewatering mechanism resulted in 96% sediment retention and effluent water quality data similar to results associated with standard silt fence installations. Silt fence dewatering time was reduced from over 24 to 4 h with minimal downstream disturbance of soil and vegetation. Finally, structural analysis data from five common silt fence support posts were used to determine post spacing based on structural load limits. Using these data and in-field observations, recommended distances for post spacing were developed for each support post type.

A Spatial Approach to Determining Suitable Water Harvesting Sites in Cambodia

Ward, M., Poleacovschi, C., and Perez, M.A. | 2021 | Cambodia suffers from devastating droughts in the dry season and floods in the wet season. These impacts can partly be attributed to ineffective irrigation systems and water resources infrastructure that are unable to retain water throughout the dry season. Water harvesting—i.e., the collection and management of floodwater or rainwater runoff to increase water availability for domestic and agricultural use as well as ecosystem sustenance—is one approach that could help improve Cambodia’s climate resiliency. This research uses a combination of geospatial analysis and analytical hierarchy processes to determine suitable sites for water harvesting reservoirs. To determine ideal sites for water harvesting reservoirs, pairwise comparisons were performed between: soil drainage, geologic porosity, precipitation, and slope. Model weights were assigned to decision parameters based on prior water harvesting studies. A preliminary model showing suitable sites for water harvesting reservoirs was developed. This preliminary model can help guide future water infrastructure projects aimed at improving climate resiliency by identifying what sites are suitable for water harvesting reservoirs.

Field Evaluation of Wattle and Silt Fence Ditch Checks

Schussler, J.C., Kazaz, B., Perez, M.A., Cetin, B., and Whitman, J.B. | 2021 | Erosion and sediment control practices are implemented during construction activities to mitigate downstream effects, but limited field-performance data exists. Field assessments were conducted to evaluate ditch check installations during highway construction in Tama County, Iowa. Data collection included daily rainfall, topographical surveys of sediment deposition, pre- and post-rain event images, and visual observations. Variations to the standard Iowa Department of Transportation silt fence ditch check installation evaluated as part of this study include: (a) upgrading non-reinforced geotextile to a multi-belted, reinforced geotextile (i.e., SF-M1); (b) installing V-shape, as opposed to linear, while incorporating wire reinforcement to support hydrostatic loads placed on the geotextile, inclusion of a weir to facilitate controlled flow discharge, and offsetting the geotextile entrenchment location to improve ground securement (i.e., SF-M2); and (c) installing the dich check as described for SF-M2 substituting slicing for trenching (i.e., SF-M3). The modified wattle installation (i.e., W-M) incorporated a teepee staking configuration to facilitate ground contact, and an excelsior underlay, secured by sod staples, to minimize wattle undercutting. Results from field experiments indicated that sediment retention rates significantly improved for installations of SF-M2 and SF-M3 when compared with the standard installation and SF-M1 at the 85% confidence level, and served as viable control measures in concentrated flow applications. The W-M installation exhibited a statistically significant improvement in sediment retention over the W-S installation at the 95% confidence level. These findings suggest that ditch check performance is a function of specified practice and of installation methods described within regulatory agency specifications and design guidelines.

A State-of-the-Practice Review on the use of Flocculants for Construction Stormwate Management in the United States

Kazaz, B., ,Perez, M.A., and Donald, W.N. | 2021 | Construction stormwater practices have a vital role in protecting downstream water bodies from runoff that is typically characterized with large amounts of sediment and suspended solids. Most sediment control practices lack the capability to capture fine-sized soil particles that are responsible for causing elevated turbidity. Flocculation is a form of chemical treatment that uses flocculant particles as a binding bridge to form larger particles to enhance the gravitational settling process. The use of flocculants provides promising results for removing fine particles and treating construction stormwater. This study provides a comprehensive review of flocculants and their applications in construction stormwater treatment in the U.S. The study presents a literature review and results of a state-of-the-practice survey distributed to state departments of transportation. Results from 37 participating state agencies and data from specifications and design manuals for non-participating agencies were compiled to develop a comprehensive understanding of current uses and perceptions. Results indicated that 39% of state agencies currently use flocculants on construction sites. Within that, 54% of the state agencies rely on manufacturer guidance for dosage and application rates and only 23% require monitoring residual flocculant in downstream receiving waters. The potential risk of polluting downstream water bodies because of overdosage of flocculants related to inadequate application rates and techniques is the main concern of the state departments of transportation on flocculant usage. Understanding the perspective of the state agencies on flocculants will provide an insight into future research agendas for extending the use of flocculants in construction stormwater management.

Hydraulic Performance Evaluation of Wattles used for Erosion and Sediment Control

Whitman, J.W., Schussler, J.C., Perez, M.A., and Liu, L. | 2021 | Land disturbing construction activities can become nonpoint sources of pollution, particularly due to suspended sediment, if erosion and sediment control measures are ineffective. Wattles have become popular practices among many governing agencies and contractors because of the variety of wattle materials available and their vast array of applications, such as ditch checks, inlet protection practices, and perimeter controls. As technologies continue to emerge, quantifying wattle performance can be a difficult and daunting task. To better understand hydraulic performance, flume experiments were conducted on eight manufactured wattles using a testing regime that used four inflow rates of 0.007, 0.021, 0.035, and 0.057 m3/s (0.25, 0.75, 1.25, and 2.00 ft3/s) and three longitudinal channel slopes of 3.50%, 4.25%, and 5.00%. Hydraulic measurements to assess wattle performance were taken for each trial after flow stabilization. Six different fill materials (excelsior wood fiber, wheat straw, coconut coir, recycled synthetic fiber, chipped wood, and miscanthus fiber) and four containment systems (natural netting, synthetic netting, synthetic socking, and polyester socking) were evaluated. Test results indicated that wattles fall into one of four developed classes based on correlations between hydraulic depth ratios and subcritical length ratios identified in the study. Class 1 wattles are considered the least hydraulically favorable, and Class 4 wattles are considered the most favorable at reducing supercritical flows when compared to the performance of an impervious weir control test. Two-way (flow rate and channel slope) ANOVA analyses were conducted to evaluate the degree of wattle performance variations for each wattle type, and a multiple linear regression model was developed to quantify performance characteristics based on fill material, slope, and flow rate from a base case (i.e., impervious weir) scenario. The ANOVA analyses indicated that synthetic fiber and miscanthus filled wattles had superior hydraulic performance capabilities when subjected to various flow rates and longitudinal slopes based on no statistical difference across flow rates and slopes. The multiple linear regression model suggested that excelsior fiber was the least effective fill material for establishing flow velocities favorable for soil particle settlement, while miscanthus fiber created the most favorable conditions. Lastly, water absorption evaluations suggest that saturated wattle density, as opposed to dry density, can be used to link the wattle fill type to hydraulic performance.

Construction Site Utilization Planning: A Process based upon Industry Best Practices

Whitman, J.B., Deshpande, A., Zech, W.C., and Perez, M.A. | 2021 | Construction site utilization planning (CSUP), also known as jobsite layout planning, has implications on the safety, productivity, scheduling, and budgetary performance of a project. Past research efforts on CSUP have mainly focused on the development of optimization systems that delineate and allocate site space to predetermined temporary facilities based on time and/or cost constraints. Despite the significant body of knowledge on site optimization systems, the applicability of optimization algorithms remains limited due to the unique requirements and site constraints faced on each construction project. An important aspect not identified in past research efforts are the current practices for site utilization plan (SUP) development currently used by the construction industry. Therefore, the objectives of this research were to: (1) determine the state-of-the-practice regarding CSUP within the construction industry, (2) identify current SUP best practices, and (3) develop a procedure that outlines the CSUP process. An electronic survey was sent to 4021 industry professionals inquiring on current CSUP practices. A total of 240 responses were received, for a response rate of 6%. Thirteen best practices were identified from the survey, each focusing on an important aspect of the site planning process. These best practices were validated through a follow-up survey, as well as in-person interviews with experienced construction professionals. From the best practices, a procedure describing the development of a SUP was created. Key components identified were: (1) begin CSUP during budget development, (2) involve all stake holders associated with the project, and (3) remain flexible on space allocation throughout the construction life cycle.

Deep Learning-Based Object Detection for Unmanned Aerial Systems- Based Inspections of Construction Stormwater Practices

Kazaz, B., Poddar, S., Arabi, S., Perez, M.A., Sharma, A., and Whitman, J.B. | 2021 | Construction activities typically create large amounts of ground disturbance, which can lead to increased rates of soil erosion. Construction stormwater practices are used on active jobsites to protect downstream waterbodies from offsite sediment transport. Federal and state regulations require routine pollution prevention inspections to ensure that temporary stormwater practices are in place and performing as intended. This study addresses the existing challenges and limitations in the construction stormwater inspections and presents a unique approach for performing unmanned aerial system (UAS)-based inspections. Deep learning-based object detection principles were applied to identify and locate practices installed on active construction sites. The system integrates a post-processing stage by clustering results. The developed framework consists of data preparation with aerial inspections, model training, validation of the model, and testing for accuracy. The developed model was created from 800 aerial images and was used to detect four different types of construction stormwater practices at 100% accuracy on the Mean Average Precision (MAP) with minimal false positive detections. Results indicate that object detection could be implemented on UAS-acquired imagery as a novel approach to construction stormwater inspections and provide accurate results for site plan comparisons by rapidly detecting the quantity and location of field-installed stormwater practices.

SILTspread: A Performance-Based Approach for the Design and Installation of Silt Fence Sediment Barriers

Liu, L., Perez, M.A., Whitman, J.B., Donald, W.N., and Zech, W.C. | 2021 | Construction operations are susceptible to high rates of rainfall-induced soil erosion due to the earth-disturbing nature of land-grading activities. Silt fence sediment barriers are a temporary sediment control practice comprising geotextile material supported by posts. Silt fence sediment barriers create containment systems to remove suspended soil particles by intercepting stormwater runoff and forming temporary impoundments. Most existing silt fence sediment barrier design guidance primarily relies on state design standards based on rules of thumb that lack scientific justification. Proper design and implementation of silt fence sediment barriers is critical and must consider site-specific factors such as topography, precipitation, soil type, and other site parameters. This technical paper describes a silt fence sediment barrier design and installation standard developed through a literature review of current state agency guidance and performance-based research. This study proposes a hydrologic design approach using local site conditions while accounting for detention volumes provided by silt fence sediment barrier installations. A streamlined hydrologic design approach and volumetric storage relationships were developed for three standard silt fence sediment barrier installation configurations (linear, J-hook, and C-shape). In addition, a user-friendly spreadsheet-based tool was developed to assist designers in calculating hydrologic and volumetric parameters, properly sizing silt fence sediment barrier segments, and estimating maintenance needs. A case study and recommendations for state agency implementation are included to demonstrate the application of the developed design approach.

Slope Stability of Streambanks at Saturated Riparian Buffer Sites

Dickey, L.C., McEachran, A.R., Rutherford, C.J., Rehman, C.R., Perez, M.A., Groh, T.A., and Isenhart, T.M. | 2021 | Saturated riparian buffers (SRBs) reduce nitrate export from agricultural tile drainage by infusing drainage water into carbon-rich riparian soils where denitrification and plant uptake occur. The water quality benefits from SRBs are well documented, but uncertainties about their effect on streambank stability have led to design standards that limit the maximum bank height and minimum buffer width, thus reducing the number of suitable candidate sites. In this study, the relationship between SRB design and streambank stability was examined through numerical slope stability modeling and validated using field sites. At the study sites, the addition of SRB flow increased the probability of failure by less than 3% for both simulated dry and rainfall scenarios. Furthermore, the simulations provide no evidence to support excluding potential sites based on bank height alone. Multivariate analysis of dimensionless parameters developed for SRB flow conditions was used to predict the factor of safety as a function of the SRB site and design conditions. The equation presented allows designers to assess the stability of a potential site where bank failure poses a heightened risk. The results of this study alleviate the need for extensive geotechnical evaluations at future SRB sites and could increase SRB implementation by expanding the range of eligible sites.

Soil Loss Risk Analysis for Construction Activities

Kazaz, B., Schussler, J.C., Dickey, L.C., and Perez, M.A. | 2022 | Construction-related ground-disturbing activities leave exposed land susceptible to soil loss and increase the risk of polluting adjacent waterbodies with sediment-laden discharge. State and federal regulations require stormwater pollution prevention plans to be implemented during construction to mitigate the impact of stormwater runoff. Areas prone to soil loss can be identified early in site planning using soil loss modeling. Identification of these critical areas could influence the design and placement of erosion and sediment control practices. The Revised Universal Soil Loss Equation (RUSLE) can be applied to estimate the soil loss on construction sites in tonnes per Ha per year (tons/acre/year) by considering factors of rainfall erosivity, soil erodibility, length of slope, erosion control, and sediment control. This study integrates geographic information system (GIS) with RUSLE to create soil loss models for residential, commercial, and highway construction scenarios in the contiguous U.S.A. These three construction types were modeled in various locations throughout the country to assess erosive risk. Soil loss outputs were categorized into five risk tiers ranging from very low to very high. Southeastern states had the highest estimated soil loss during residential, commercial, and highway construction, reaching rates of 1,464, 706, and 1,302 tonnes per Ha per year (653, 315, and 581 tons/acre/year), respectively. This study provides a customizable model for any site-specific slope-length factor outside of the three construction scenarios modeled. Integration of GIS provides a unique opportunity to apply RUSLE across a larger landscape. The presented macro-scale data can be used for the design of erosion and sediment control practices.

Detection of Residual Flocculant Concentrations in Construction Stormwater Runoff

Kazaz, B., Perez, M.A., Donald, W.N., Fang, X., and Shaw, J.N. | 2022 | Flocculants provide an innovative solution for managing construction stormwater runoff with their efficiency in reducing turbidity in the effluent. With proper application and dosage, these chemicals improve the performance of sediment control practices in capturing fine-sized soil particles. Flocculants function by providing electromagnetic charges to attract soil particles into large molecular bridges of flocs. Following this process, suspended particle removal can be achieved through gravitational forces. Despite the benefits of using flocculants, their implementation may create a potential risk of polluting downstream waterbodies and harming aquatic life in case of a high residual concentration in discharge. Determining residual concentrations is challenging for practitioners because of a lack of field applicable testing methods that work across a variety of flocculant types. This study developed a field applicable methodology for detecting residual flocculant concentrations by using settling velocity as an identifier of flocculant concentration. In total, 14 products comprised of polyacrylamide, sodium montmorillonite, chitosan, agricultural gypsum, and alum-based products were evaluated. Known flocculant concentrations ranging from 0% to 30% of the manufacturer’s recommended dosage, were mixed with a fine soil passing through No. 200 sieve and allowed to settle in a graduated cylinder to record the settling velocity. Regression analysis was conducted on the experimental data to develop concentration versus settling velocity relationships which indicated that more than 90% of known concentration values are dependent on the settling velocity. The study provides a framework for practitioners to identify residual flocculant concentrations in field conditions by relating settling velocity with chemical concentrations.

Development and Evaluation of Lamella Settlers combined with Electrocoagulation for Treating Suspended Sediment

Liu, L., and Perez, M.A. | 2022 | Stormwater quality has become an increasingly important issue in agricultural, urban, and construction sectors. Soil, nutrient, and pollutant discharge caused during rainfall events is one of the greatest sources of stormwater quality degradation. Enhanced stormwater treatment mechanisms are needed to economically and efficiently remove suspended pollutants in runoff. In this research, the performance of electrocoagulation (EC) combined with lamella settlers (LS) was investigated. EC is a highly effective and proven water-treatment technology that uses an electrochemical anode corrosion process to destabilize and remove contaminants and that has been shown to have widespread applications for treating a variety of wastes. LSs have been shown to enhance soil-particle capture by increasing the surface area and reducing the settling distance. This research demonstrated that the combination of EC and LS can enhance the sedimentation process while simultaneously decreasing the required detention time and size of traditional sediment control practices (i.e., detention basins, sediment basins). Combining EC with a LS is a novel approach for treating suspended particles in stormwater. In this project, bench-scale experiments were conducted using EC as pretreatment upstream of a LS reactor. Synthetic silica filler at concentrations of 500 mg/L, 1,000 mg/L, and 5,000 mg/L were used to evaluate treatment efficiency at 0.5-h, 1.0-h, and 1.5-h residence times. Collected data, including turbidity, total suspended solids, and particle size distribution, were used to statistically characterize the system’s sediment removal performance. Through a series of experiments and statistical analyses of the results, an optimized EC+LS reactor with 1.27-cm (0.5-in.) LS plate spacing and 1.5-h residence time reduced turbidity by up to 98% and total suspended solids by 99% in effluent when compared with a base case reactor with a 31.8 cm (12.5 in.) settling distance (no LS plates installed) and 0.5-h residence time without EC pretreatment. In addition, particle size distribution analyses resulted in a decrease in the D90 value by 84%, indicating that the optimized reactor was effective in capturing larger-diameter soil particles. To validate the laboratory results with synthetic sediment-laden influent, stormwater samples were collected from a construction site and treated through the optimized system, resulting in a turbidity reduction of 50% and TSS reduction of 69%.

A Decade of Research in Review: The Auburn University - Erosion and Sediment Control Testing Facility

Schussler, J.C., Perez, M.A., Donald, W.N., Whitman, J.B., Zech, W.C., Fang, X., and Fagan, B.G. | 2022 | Sediment remains one of the most commonly occurring pollutants affecting the U.S.’s water bodies, as identified by the United States Environmental Protection Agency (USEPA) (1). Construction activities largely accelerate soil erosion and subsequent sediment deposition. The National Pollutant Discharge Elimination System Construction General Permit requires construction operators to implement erosion and sediment control (E&SC) plans to minimize downstream implications from sediment-laden discharge. However, E&SC practices are often designed from “rules of thumb” and lack scientific, performance-based evidence in their design and implementation. The Auburn University Stormwater Research Facility (AU-SRF), previously the Auburn University Erosion and Sediment Control Testing Facility (AU-ESCTF), is an outdoor research center dedicated to evaluating E&SC practices and products commonly used on highway construction projects. Large-scale test apparatuses and methods at AU-SRF are designed to mimic construction site conditions, including rainfall, flow rates, topography, and soil characteristics, to evaluate existing and novel E&SC practices. Since its inception in 2008, AU-SRF has provided small-, medium-, and large-scale testing evaluations for numerous Departments of Transportation and product manufacturers. Findings from controlled testing have continued to inform the selection, design, implementation, and maintenance of E&SC practices used on construction sites and protect downstream waters and infrastructure. In the first decade, AU-SRF has directed 13 research projects and produced more than 30 peer-reviewed publications and 100 professional presentations. As AU-SRF grows into its second decade and efforts reach outside of the southeastern region, the mission to advance knowledge through E&SC research and development, product evaluation, and training remains constant. This review synthesizes the research produced from large-scale testing at AU-SRF to date and presents ongoing projects.

Assessment of Polyacrylamide Concentration in Construction Stormwater Runoff using an ASTM D6459 Rainfall Simulator

Manning, C., Perez, M.A., and Donald, W.N. | 2022 | Polyacrylamide (PAM) is a polymer used in construction stormwater management as both an erosion and sediment control measure. PAM is considered one of the environmentally safest polymers on the market, however overapplication concerns dictate that large quantities in runoff be avoided. For slope erosion applications, ensuring proper concentration requires methods for testing residual concentrations. This research investigated residual concentrations of PAM when dry-applied at a rate of 25 lb/acre (28 kg/ha) for slope stabilization and subjected to 1-h of simulated rainfall following ASTM D6459-19 protocols at three 20-min successive 2-, 4-, and 6-in./h (5-, 10-, and 15-cm/h) intensities. Residual concentrations were determined by centrifuging runoff samples to remove soil and reading absorbance from an ultraviolet-visible spectrometer, comparing values to those at known concentrations. Concentrations in collected runoff samples were found to surpass values found in previous research and in other PAM applications, especially during first flush, and were high enough to affect water viscosity. An alternative application method is presented that may mitigate PAM runoff concentration. The spectrometry method was also used to highlight the possibility that polymers used in hydromulches may also deposit excess concentrations in stormwater runoff, and that formal residual testing of such products is warranted. The processes used for this study demonstrated how discharge may be monitored and regulated to minimize undesirable runoff conditions from construction sites and underscore the importance of appropriate design and implementation when using additives for erosion control.

Evaluating Climate Change Adaptation Barriers of Critical Infrastructure in Rural Alaska

Taylor, J., Poleacovschi, C., and Perez, M.A. | 2022 | As climate change impacts intensify, communities in rural Alaska are undergoing and adapting to changes to infrastructure from increased permafrost thawing, flooding, and erosion. Climate change adaptation is needed to address structural failures and safety concerns. Despite recognizing the need for support from stakeholders and adaptation of infrastructure, the level of adaptation activity remains limited and inconsistent across regions and communities in rural Alaska. We address this need by identifying barriers to community-wide adaptation of infrastructure based on stakeholder perspectives who make adaptation decisions for government agencies, nonprofits, engineering firms, or academic institutions in rural Alaska. Barriers were identified qualitatively through interviews (N = 25) and validated quantitatively through surveys (N = 30). Qualitative and quantitative results identified and validated 17 barriers to adaptation of infrastructure – spanning sociocultural, institutional, economic, physical, and environmental dimensions based on the Sustainable Livelihoods Framework (SLF). Results demonstrate the need for national adaptation funding and policy that is specific to the diverse cultural landscapes, extreme weather, rural locations, limited transportation, and high costs in rural Alaska. Adaptation funding and policy is needed that supports the collaboration of Alaska-based institutions, such as nonprofit organizations and engineering firms, Tribal entities, and rural Alaska community representatives in adaptation.

Field-Monitoring Sediment Basin Performance during Highway Construction

Schussler, J.C., Perez, M.A., Cetin, B., and Whitman, J.B. | 2022 | Stormwater regulations require erosion and sediment control practices to be implemented during construction to prevent discharging polluted water offsite and mitigate downstream effects. Sediment basins are a common practice used to detain suspended sediment from stormwater runoff by providing residence time and storage to promote gravitational settling. Sediment basin design, and thus pollutant removal efficiency, vary regionally due to local design standards and preferences. This manuscript presents the results of a case study from Highway U.S. 30 construction in Tama County, Iowa, USA where two sediment basin systems were created within a conveyance channel by constructing an earthen berm across the channel to detain sediment-laden stormwater. A dewatering riser pipe was routed through the earthen berm to provide primary dewatering. The in-channel sediment basin was constructed with a 3% slope and a 10 ft. bottom width. The first system consisted of one basin created by a single earthen berm damming sediment-laden runoff, whereas the second system included two earthen berms, creating two in-channel sediment basins in series. Field monitoring was conducted on in-situ basins by deploying a rain gauge and automated water samplers positioned at the inflow and discharge points of a (a) single basin and (b) two basins in series within a roadside channel. During the monitoring period, no maintenance or dredging was recorded. Water samples were taken from the monitored basins at regular time intervals and analyzed for turbidity. Inflow turbidities often reached magnitudes up to the 103 NTU and discharge samples indicated negligible turbidity reduction after residence. On several occasions, the in-channel sediment basins acted as a sediment source, with discharge turbidities measuring higher than inflow. Despite their initial performance, there was interest in improving the in-channel basin design due to the potential to maximize length-to-width flow ratios, and use of existing infrastructure, which reduced the amount of right of way needed for basin construction, installation time and cost. As a result, several potential design improvements and techniques were recommended to enhance in-channel sediment basin performance.

Groundwater Flow in Saturated Riparian Buffers and Implications for Nitrate Removal

McEachran, A.R., Dickey, L.C., Rehmann, C.R., Isenhart, T.M., Groh, T.A., Perez, M.A., and Rutherford | 2022 | A saturated riparian buffer (SRB) is an edge-of-field conservation practice that intercepts tile drainage and reduces nitrate flux to nearby streams by redistributing the flow as shallow groundwater. In this study, a three-dimensional, finite-difference groundwater model representative of SRBs in central Iowa was developed to assess the flow of groundwater and implications for nitrate removal during spring conditions, when flow to the SRB is highest. The model reproduces field observations of water level with Nash–Sutcliffe efficiency of 0.68, which is deemed acceptable for hydrologic models. The modeling shows that groundwater flow is three-dimensional near the distribution pipe and the stream and primarily one-dimensional in the rest of the buffer. The path the water takes in flowing toward the stream depends on where it exits the distribution pipe. When nitrate is not limiting, the potential for nitrate removal depends on the length of the path—and thus travel time—and depth because denitrification potential varies with depth. Travel time Tt can be estimated well with slight modifications to a one-dimensional approximation: Tt = 1.11Lx/vx, where Lx is the buffer width and vx is a one-dimensional approximation of the average linear velocity of groundwater. Refining knowledge of SRB function is an important step toward enhancing design for improving water quality.

Hydraulic Evaluation of Wattle Encasement Materials

Clampitt, J.E., Perez, M.A., Whitman, J.B., Donald, W.N., LaMondia, J.J., and Craig, A.J. | 2023 | Suspended sediment in stormwater runoff can have negative environmental impacts. Construction activities are a major contributor to sediment-laden runoff caused by the constant disturbance and destabilization of soil. Wattles are one of the most commonly used materials across a wide range of erosion and sediment control applications. Past research has found that the hydraulic performance of wattles is based primarily on fill material. This research focused on further evaluating wattles by assessing the impact that encasement material (e.g., netting, socking, etc.) has on hydraulic performance. Two separate hydraulic flumes were used in a two-phased approach. Phase I evaluated wattle encasement fabric configurations. Selected encasements were then evaluated in Phase II using 4.0 ft (1.2 m) excelsior fill materials: plastic netting (control), polypropylene, polyester and polypropylene mix, and cotton woven encasements. The results from each wattle test were normalized with impoundment length and depth ratios. Results indicated that the percent open area (POA) had a direct relationship with the impoundment length and depth when the encasements were evaluated independently of the fill material, but encasement type had a larger effect on performance when fill material was included. Using a cotton fabric increased impoundment length and depth ratios by 30% and 24%, respectively, which increased to 52% and 42%, when two additional cotton fabric layers encompassed the wattle.

Evaluation of Surface Skimmer Flow Rates and Size Selection

Sharpe, C.D., Perez, M.A., and Donald, W.N. | 2023 | A floating surface skimmer is a device used to dewater a sediment basin as it fills. The skimmer floats on the surface, draining the least turbid water as sediment falls out of suspension. An adjustable orifice on the skimmer regulates the filling and draining rate of the basin. After significant runoff events, skimmers slowly drain the basin over several days to maximize settling, while draining less turbid water from the top of the water column. Manufacturers have published data for products that customers can use to decide on the skimmer type, size, and orifice opening, but these design parameters tend to be very rough estimates with numerous assumptions. This study details a methodology for testing skimmers, including the materials, data collection process, and data analysis approach required to obtain the most accurate skimmer flow rate data. Testing was performed on a 15.2 cm (6.0 in.) post-construction stormwater skimmer prototype provided by J.W. Faircloth & Son, Inc., in an approximately 30 m3 (1000 ft3) evaluation tank. This skimmer used an adjustable sluice gate to control flow rate and had two barrel lengths. Six sluice gate opening sizes were tested three times for both barrel lengths, resulting in 36 tests performed. Experiments revealed that the skimmer had a capacity ranging from 0.03 m3/s (0.5 ft3/s) with a 2.54 cm (1.0 in.) opening and a capacity of 0.071 to 0.085 m3/s (2.5–3.0 ft3/s) with an opening of 15.2 cm (6.0 in.). Experimental results were then used to create a user-interactive skimmer sizing tool to provide more accurate information on sediment basin storage and drawdown times based on skimmer selection.

Optimum Dosage and Product Selection Guidance for Flocculant Usage in Construction Stormwater Treatment

Kazaz, B.K., Perez, M.A., Donald, W.N., Fang, X., and Shaw, J.N. | 2023 | Implementing proper methods and techniques for construction stormwater management brings numerous benefits in protecting the environment, maintaining social justice, and enhancing sustainability within the construction industry. Flocculants improve construction stormwater management on active job sites by enhancing the function of temporary sediment control practices by facilitating the capture of fine-sized soil particles that are otherwise difficult to settle. The performance of flocculants is dependent on specific soil properties, dosage, and application techniques. Proper product selection and identification of adequate dosage rates is an arduous task for practitioners given the soil variability across job sites and a lack of implementation guidance. This study investigated the performance of various commercially available flocculant products on 15 soil samples collected from construction sites across Alabama through bench-scale testing methods. Experiments focused on providing guidance on product selection and identifying optimum dosage rates through soil assessment, match tests, and dosage experiment phases. The performance of polyacrylamide, sodium montmorillonite, chitosan, agricultural gypsum, and alum-based products was investigated across all soil samples for product selection. Dosage of selected products was evaluated by ranging manufacturers’ dosage recommendations from 0% to 200% to evaluate settling performance across a range of dosing conditions. Results indicated that increasing recommended dosage rates negatively affected the turbidity reduction performance of tested products. In general, dosages lower than 40% manufacturer recommended rates showed a statistically significant improvement in turbidity reduction at a 95% confidence level. The study provides insight for practitioners and future research agendas on the proper usage of flocculants in the construction industry.

Efficacy of Undisturbed Vegetated Buffers in Capturing Suspended Sediment

Roche, B.G., Perez, M.A., Donald, W.N., and Whitman, J.B. | 2023 | The U.S. Environmental Protection Agency’s Construction General Permit requires a 50 ft (15 m) undisturbed vegetated buffer to be maintained when construction activities are adjacent to a water body. However, maintaining a buffer is not always feasible, especially in highway construction activities; therefore, a contractor may use alternatives that capture sediment at an efficiency equivalent to an undisturbed buffer. However, little research has been conducted on the sediment removal efficacy of an undisturbed vegetated buffer. Several factors influence the sediment capture efficiency of a natural vegetated buffer, including climate, soils, topography, and vegetation characteristics. This research aimed to explore the sediment removal capabilities of various vegetated buffers with factors common to Nebraska roadway construction projects using the Revised Universal Soil Loss Equation 2 Model. A multiple linear regression model was developed to analyze relationships between 7,776 model iterations. Statistical analysis indicated that decreasing the slope of the buffer and the clay and silt content in the soil increased the sediment removal efficiency of the buffer; this finding matched the conclusions of past research on vegetated filter strips and vegetated buffers. Sediment removal ranged between 77% and 99%, with an average efficiency of 94%—comparable to the efficacy of manufactured sediment barrier practices commonly used on construction sites.

Comparison of Erosion Control Products using an ASTM D6459 Rainfall Simulator: Insights and Suggestions

Manning, C., Faulkner, B., Donald, W.N., and Perez, M.A., | 2023 | This study used a large-scale ASTM International D6459 rainfall simulator to evaluate performance of various types of erosion control products used in construction. Rolled erosion control products (RECPs), hydraulic erosion control products (HECPs), and soil amendments were tested and compared based on Cover factor (C factor), a parameter between 0 and 1 where 0 represents perfect erosion protection and 1 represents bare soil. All products behaved statistically similarly at the lowest rainfall intensity [5.1 cm/h (2 in./h)] with an average C factor of 0.03. At the next intensity of 10.2 cm/h (4 in./h), RECPs had significantly lower C factors than HECPs (0.11 and 0.41, respectively). Among the HECPs, Type 2 had worse C factors than other products, but all deteriorated at the highest 15.2 cm/h (6 in./h) intensity, reaching an average C factor of 0.48. Most (88%) products met their industry minimum specifications at the lowest rainfall intensity, but only 25% met them by the highest intensity. The soil amendments did not have published C factors, so their performance was compared to traditional products. Gypsum statistically matched the RECPs while Polyacrylamide (PAM) statistically matched the HECPs. Preliminary testing was performed on thee straw applications, but due to sampling differences only a soil loss ratio, or simple ratio of soil lost on the bare plot to soil lost on the treated plots, was calculated. A cost estimate obtained though local professionals revealed that the straw treatments appeared to be the most economical in terms of total dollars spent per reduction in sediment loss, and that the cost of premium hydraulic mulches did not appear to translate into improved performance. This study is useful because large-scale simulations more accurately reflect field erosion performance, but they are seldom performed due to time and cost considerations. In addition, varying intensities revealed performance differentiations, many product types were compared, and using an industry standard allows for confident comparison to other results.

Climate Change Adaptation Among Indigenous Peoples: A Systematic Review of the Emperical Research Focus over the last two Decades

Taylor, J., Poleacovschi, C., and Perez, M.A. | 2023 | Over the past 20 years, an increasing number of empirical research conducted aims to understand climate change adaptation among Indigenous groups. Despite the increased scholarly interest, a comprehensive understanding of empirical adaptation research trends across various continents and disciplines is noticeably absent from the literature. Thus, this article systematically assesses the state of empirical adaptation literature involving Indigenous peoples globally. Using Scopus and the Web of Science, we analyzed 140 peer-reviewed journal articles, identifying two main trends—research attributes and themes of adaptation. Research attributes identified include publication year, research location, and methods. Our results show that studies are increasing in number each year, primarily in Africa, Asia, and North America, and primarily use qualitative methods. Synthesizing research attributes informs how scholars engage with adaptation research involving Indigenous peoples. Thematic analysis results show that articles mainly focused on four themes of adaptation, including adaptation strategies, drivers, barriers, and adaptation process approaches. The most prominent sub-theme of adaptation strategies was agricultural practices, adaptation drivers were Indigenous knowledge and traditions, and adaptation barriers were governance barriers. Adaptation process approaches sub-themes included holistic approaches to adaptation, local collaboration, and knowledge integration in adaptation. Identifying themes of adaptation contributes to the body of knowledge and practical application by informing adaptation plans, investment, and policy. This analysis points to the need for: (1) researchers to conduct additional studies in the Pacific Islands and Central and South America, where increased vulnerability emphasizes the importance of adaptation; (2) researchers to expand sectors included in studies, such as health and cultural adaptation; (3) researchers and practitioners to employ participatory methods; and (4) researchers and practitioners to situate adaptation in the context of colonization.

Stereotypes and Stereotype Threats Experienced by Latinx Undergraduate Engineering Students

Turochy, E., Ballesteros, L.M., Perez, M.A., Yuen, T., Estes, K., Poleacovschi, C., and Doran, E. | 2023 | Latinx engineering students often experience stereotype threats in their programs. Stereotype threats not only affect student self-esteem but can influence academic performance and persistence in engineering programs. Our research aims to increase understanding of the specific types of stereotyping and stereotype threats experienced by Latinx engineering students. We also analyze how these stereotypes and stereotype threats are experienced across different demographic groups, class standing, engineering major, and institutional context. Our research analyzes various stereotypes and stereotype threats that Latinx undergraduate engineering students face using data collected from interviews and surveys across three universities, two Predominately White Institutions (hereafter, PWI) and one Hispanic Serving Institution (hereafter, HSI). A content analysis of the 28 interviews and Ordinary Least Squares (OLS) regression analysis were conducted on our 156 survey responses. Nine major stereotype and stereotype threat themes related to engineering identity were identified. Findings showed that Latinx undergraduate engineering students commonly experienced both ethnicity and gender stereotype threats, particularly in the form of ''assumed behaviors'' and ''assumed academic abilities''. Regression analyses also suggest that female gender identity is a statistically reliable predictor of students experiencing both gender and ethnicity stereotype threats. Latinx undergraduate engineering students commonly experience stereotyping and stereotype threat along ethnic and gender lines, with female identifiers systematically more susceptible to both. The implications of this research are significant, as both identity categories of this intersectional group-female and Latinx-are already underrepresented in engineering educational programs and professions. This research expands the literature on the impact of stereotypes and stereotype threat on Latinx undergraduate engineering students' persistence and success in this major and emphasizes the need to foster inclusion and diversity within engineering programs.

Exploring the Integration of Unmanned Aerial System Technologies into Stormwater Control Inspection Programs

Whitman, J.B., Perez, M.A., and Sturgill, R. | 2023 | Construction stormwater best management practices and post-construction stormwater control measures are controls and techniques designed to manage and treat stormwater runoff. Departments of Transportation (DOTs) within the United States rely on these practices to treat and improve water quality emanating from DOT rights of way. To ensure operational performance, these practices undergo periodical inspections to identify if operational deficiencies exist and if corrective measures need to be deployed. The inspection process is often conducted on foot by a qualified inspector and can require a substantial labor effort to complete. Recently, unmanned aerial system (UAS) technologies have been utilized in the construction sector to survey, monitor, and improve safety. This study sought to identify and document practices regarding UAS technologies when conducting inspections of stormwater practices. Through a distributed DOT survey questionnaire (80% response rate) and four case example interviews, this study investigates how UAS stormwater inspections have been deployed by DOTs and the strategies and programs that have been adopted or created. Key findings outline (1) use of UAS technologies for stormwater inspections, (2) applying UAS technologies within a DOT, (3) staffing and equipping needs, and (4) managing UAS inspection datasets. The study also identifies challenges and implementational strategies to facilitate the development of a UAS stormwater inspection program within a DOT.

Large-Scale Performance Evaluation of Various Woven Silt Fence Installations under Nebraska Highway Conditions

Roche, B.G., Perez, M.A., Donald, W.N., and Whitman, J.B. | 2024 | Sediment barriers are used on construction sites to protect downstream waterbodies from the impacts of sediment-laden stormwater runoff. Although ubiquitous on construction sites, many sediment barrier practices lack performance-based testing to determine effectiveness and treatment mechanisms, with previous evaluations being limited to conditions local to the Southeastern U.S., with conditions in other regions remaining untested. Testing was conducted to determine the effectiveness of woven silt fence barriers and provide structural improvements to common installation methods. Testing was conducted using a large-scale sediment barrier testing apparatus at the Auburn University—Stormwater Research Facility. The results from testing indicate that Nebraska DOT standard silt fence installations can be improved to reduce the risk of structural failures such as undermining, complete installation failure, slow dewatering, and overtopping. To improve structural performance, four modifications (a 15.2 cm [6 in.] offset trench, wooden posts, a dewatering board with an overflow weir, and a dewatering board with an overflow weir with adjusted post spacing) were tested. On average, 83% of introduced sediment was retained behind the tested barriers. The water quality results across the testing of standard and modified installations indicated that stormwater treatment was due to sedimentation within the impoundment formed by silt fence installations and not filtration through geotextile fabric.

Evaluation of Crimped Straw as an Erosion Control Practice on Varying Soil Types on a 4:1 Slope

Cater, J., Perez, M.A., and Donald, W.N. | 2024 | Construction sites rely on erosion control practices to protect bare slopes and prevent soil loss. The effectiveness of certain erosion controls is often under-evaluated if they are not a part of a product evaluation program. Furthermore, erosion controls in general are not fully understood regarding how their performance can be affected by site specific variables, such as soil variations. This study used large-scale rainfall simulators to evaluate how a commonly used erosion control on construction sites, broadcasted straw mulch, performs on three common soil types in Alabama. The study at the Auburn University, Stormwater Research Facility (AU-SRF) used the industry standard testing method and three different soil types: sand, loam, and clay in accordance with ASTM D6459-19, the standard test method for testing rolled erosion control products’ (RECPs) performance in protecting hillslopes from rainfall-induced erosion. As required by ASTM D6459-19, the rainfall simulators simulated a storm of varying 20 min increments of 2 in./h (5.08 cm/h), 4 in./h (10.16 cm/h), and 6 in./h (15.24 cm/h). A total of nine bare soil tests on the 4:1 test plots was performed with an average total soil loss of 1977 lb (897 kg), 236.2 lb (107 kg), and 114.2 lb (51.8 kg) for sand, loam, and clay, respectively. The average erodibility K-factor for each soil type is calculated to be 0.37 (sand), 0.043 (loam), and 0.013 (clay). Nine straw tests were performed on the 4:1 plots, with an average total soil loss of 44.31 lb (20.1 kg), 6.74 lb (3.1 kg), and 17.13 lb (7.8 kg) for sand, loam, and clay, respectively. Straw testing indicated substantial soil loss reduction with average cover management C-factor values under the revised universal soil loss equation (RUSLE) method of 0.021, 0.047, and 0.193 for sand, loam, and clay applications, respectively. This variation in C-factor across the three soil types indicates that the single C-factor, often reported by product manufacturers, is not adequate to imply performance.

Evaluation of a Pre-treatment Intake System for Reducing Particulate Loading to a Bioretention Cell

Dickey, L.C., Rehmann, C.R., Perez, M.A., and Ikuma, K. | 2024 | Urbanization and climate change pose substantial challenges to mitigating the risk of flooding and degradation of water quality caused by stormwater runoff from developed areas. Bioretention is a stormwater management practice that addresses these challenges by reducing runoff volume and contaminant transport. However, bioretention systems are prone to physical clogging from suspended particles that reduce infiltration capacity and prevent treatment benefits. Pretreatment of stormwater before entering the bioretention system can alleviate this common issue, yet few studies have focused on the design of pretreatment approaches for bioretention systems. This lack of study is particularly important because most pretreatment systems allow untreated bypass flow directly to the storm sewer. In this case study, we combine field monitoring and hydrologic modeling to evaluate the design of a pretreatment intake structure in Johnston, Iowa. We assess the structure’s effectiveness by comparing inflow concentrations (representing conditions without pretreatment) to outflow concentrations and consider the associated trade-offs for mitigating urban runoff quantity and quality. This multichambered pretreatment intake structure routes runoff through a series of internal weirs and outlets that flow to the bioretention treatment area and allow bypass directly to the storm sewer. Our field-validated results show the pretreatment intake structure removed 37% of suspended particles before they could enter the bioretention basin, thereby reducing clogging and preserving well-established vegetation that enhances performance. Additionally, modeling showed water quality and quantity benefits from a 62% reduction in the mass load of suspended particles and an 80% reduction in peak flow rate directed to the storm sewer. In contrast, trade-offs include a decrease in the amount of water entering the bioretention basin and the potential for subsequent treatment because 60% of flow bypasses directly to the storm sewer. Opportunities to improve the design of pretreatment methods for bioretention systems lie in tailoring the system to site-specific pollutants, reducing bypass flow, and preventing resuspension of settled particles. This case study contributes insights into the benefits, trade-offs, and design considerations of pretreatment for bioretention systems critical to advancing sustainable stormwater management.

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