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Construction of roads exposes large areas of soil which can lead to high erosion rates. Current best management practices are good at keeping larger sized particles on-site, but smaller particles still remain a problem for construction site stormwater discharges. Turbid water leaving construction sites can have detrimental impacts for the surrounding environment, especially for aquatic organisms such as mussels. Polyacrylamide (PAM) has been shown to help reduce turbidity of construction site stormwater.

The objectives of this project are to: (1) Establish a procedure to identify the optimum antistrip additive content for a given asphalt mixture and antistrip additive combination; (2) Evaluate the moisture damage resistance of plant-produced asphalt mixtures to establish a preliminary protocol for quality assurance and control; and (3) Develop an objective means to quantify emulsion- aggregate compatibility in lieu of the visual assessment procedure currently specified in NCDOT A-24 procedure. Laboratory- mixed, laboratory compacted mixtures were used to establish an antistrip dosage selection procedure for Boil test results coupled with Asphalt Compatibility Tester (ACT) color measurements.

The objectives of this project are to: 1) develop recommendations for extender and recycling agent product approval and dosage selection; and 2) identify appropriate aging procedure(s) to simulate long-term oxidative aging coupled with test methods and parameters to characterize the cracking resistance of asphalt binders. Three NCDOT approved surface asphalt mixtures were evaluated in this study, including a reclaimed asphalt pavement (RAP) mixture, recycled asphalt shingle (RAS) mixture, and RAP/RAS mixture. Three extenders and two recycling agents (RAs) were evaluated. The extenders were blended with PG 58-28 virgin binder whereas the RAs were blended with PG 64-22 virgin binder. Blends of recycled binder, virgin binder, and a RA or extender were prepared that achieved similar high-temperature AASHTO M 320 performance-graded properties to virgin PG 64- 22 binders in North Carolina.

FHWA/NC/2017-45, A 2014 change in vehicle appearance guidelines forwent custom bright yellow paint job in favor of the factory standard white color for NCDOT light duty trucks. This change raised some concerns about vehicle conspicuity, or the vehicle’s ability to draw attention to itself. The addition of high visibility markings was offered as a possible solution. This work used an eye-tracking system to test a variety of color options for the markings in a simulated driving environment. Results showed that, in general, there were not statistically significant differences in the time to first fixation, fixation count, and average fixation duration between the different color combinations. The results suggest that none of the tested color combinations would perform significantly better than one another at improving conspicuity.

This project performed preliminary work to support use of Unmanned Aerial Vehicles (UAV)-based for bridge inspections, providing an economical and safer alternative to conventional inspection practices. The main challenge is that most existing technologies rely on general-purpose UAV platforms and there is no verified methodology for UAV-enabled bridge inspection principles and relevant considerations to reliably obtain inspection data. There have been some efforts to use general-purpose commercially available UAVs for bridge inspection. However, the turbulent environment that often exists around bridges requires customized and enhanced UAV platforms with a higher level of robustness, taking into account the bridge type and structure as well as the weather conditions around the bridge. Additionally, the data-acquisition capabilities of commercially available UAVs need to be compared to those required for bridge inspection. Previously, there has not been a study to quantify the gap between the performance of the commercially available UAVs and ideal desired performances. In this multidisciplinary project, a comprehensive set of experiments were developed for selection, testing, and evaluation techniques of candidate UAVs, the complex nature of flying UAVs in close proximity to bridges was explored, and the limitations of UAV flight due to turbulent flows around bridge components and nearby terrain was assessed. Commercially available platforms for bridge inspection were selected, tested, and evaluated. Deliverables from this project include: (1) measurable metrics to evaluate the performance of UAVs for bridge inspection, (2) experiments to test the suitability of UAVs for bridge inspection, and (3) a comprehensive analysis near-bridge environment flow field. Computational analysis of air flow patterns near bridge elements shows that the bridge geometry creates areas of turbulence and flow variation which impact the control requirements of the UAV. Local weather cond

A new field monitoring approach in the form of metallic capsules is developed to evaluate Benzene and PCE diffusion through concrete pipe gaskets. The capsules are developed and tested with three gasket materials: Neoprene, Buna-N, and Viton. To validate the monitoring approach and develop field retrieval protocol, capsules were deployed in three contaminated sites: (i) Nash county maintenance depot in Nashville, NC (gasoline contaminated site), (ii) A maintenance facility yard in Newton, NC (gasoline contaminated site), and (iii) Triangle Laundromat in Durham, NC (chlorinated solvent contaminated site, PCE). The tensile strength of gasket materials, integrated with the deployed field capsules, is evaluated with time. In addition to testing under field conditions, tensile strength testing is also performed under controlled conditions in the laboratory to establish material degradation model. Computational modeling is used to simulate the site conditions of the installed capsules considering test sites’ hydraulic gradient, soil properties and plume concentration and the influence of such parameters on the rate of breakthrough within the installed capsules. The hydraulic parameters of gaskets were calibrated using field measurements and data from a series of experimental studies under controlled condition. Results indicated nonlinear power relationship for the mass breakthrough of benzene and PCE with time. Compared to chlorinated solvent, benzene has higher diffusivity among gasket materials (Neoprene, Buna-N, Viton). Viton showed the highest resistance to the diffusion of benzene and PCE. Viton and Neoprene showed the lowest and highest tensile strength degradation, respectively, once exposed to gasoline or chlorinated solvent contamination. Based on modeling results, benzene concentration breaking through the Neoprene and Buna-N will reach more than 70% and 60% of the monitoring well concentration, respectively, after 4 months. Benzene breakthrough reaches 85% to 9

Two swales (Mango Creek and I-40) treating highway runoff were retrofitted with simple check dams typically used for construction site sediment and erosion control to determine if these devices might improve post-construction stormwater management. The Mange Creek swale was retrofitted with a pair of standard rock check dams. The I-40 swale was retrofitted with a system of excelsior fiber wattle check dams and bags with proprietary phosphorus-adsorptive media (ViroPhosTM) to investigate if additional treatment for dissolved phosphorus was provided. Each swale was instrumented for approximately six months to collect data prior to the installation of check dams (pre-retrofit period) in March and April of 2014. Monitoring continued for an additional twelve months post-retrofit. Hydrologic data were collected at Mango Creek to examine peak flow mitigation and volume reduction imparted by the check dams due to additional storage and infiltration. Flow-proportional water quality samples were obtained to investigate removal of nitrogen and phosphorus species and total suspended solids (TSS) during the pre- and post-retrofit phases of the research. The inclusion of rock check dams in the Mango Creek swale did not significantly improve the volume reduction or peak flow mitigation of the SCM; however, these statistics were impacted substantially by the small pre-retrofit data set. Improvements were observed for volume reduction, peak flow mitigation, and hydraulic retention time, especially for small (<0.75 inch) and moderate (0.75-1.5 inch) rainfall events. Rock check dams did not significantly improve the removal rates of nutrients or TSS. However, these statistics were again impacted by the small pre-retrofit data set. Total nitrogen (TN) and total phosphorus (TP) concentrations from the highway were low compared to the literature, limiting the potential for significant reduction. Even so, TN and TP concentrations exiting the swale (0.81 mg/L and 0.13 mg/L, respectively) r

This report constitutes the second phase to document the water quality benefits of a stream restoration in the coastal plain of North Carolina. This phase compares the pre-restoration and post-restoration states of the water quality and hydrochemical signature of ‘the canal’ at the Claridge nursery in Goldsboro, NC. We made the hypothesis that a robust way to quantify the water quality benefits of this stream restoration was the use of cumulative nutrient load indicators. However, these indicators required the use of state-of-the-art instruments capable of capturing flow and water quality on a near continuous basis over the long term. After meticulous correction and all the necessary verifications, we were able to show that the restoration of the Claridge nursery canal, effectively creating a flowing wetland, was able to lower the nitrate loads by about 30% over three post-restoration consecutive years. This was accompanied by an overall carbon sequestration. The seasonality of the nitrate retention suggests that much of the nitrate unaccounted for was associated with the growth of vegetation, either through plant uptake and/or through denitrification associated with the release of organic matter from dead vegetation and the exchange conditions that they provided in the channel and with the floodplain. Increased residence time associated with the aquatic vegetation working as a filter time likely increased the capacity of the stream to retain nitrate. The seasonality of the nitrate retention may suggest that shorter monitoring periods could be chosen to represent a ‘summer’ vs. a ‘winter’ effect. However, averaging these effects would not necessarily represent the effective benefits over the long term. Instead, we suggest that monitoring should focus on cumulative indicators used over the long term for projects for which there is a high potential for nutrient retention. Fewer projects may have to be monitored, but using the necessary investment.

In response to growing traffic congestion, the North Carolina Department of Transportation will install North Carolina’s first ramp meters at four locations in the westbound direction of I-540 in Raleigh. The study outlined in this report addressed this need by developing a state-specific method that can be incorporated into NCDOT planning processes to evaluate any potential ramp metering projects in the future. The related frameworks of analysis were applied to the four westbound I-540 ramp meters to estimate the expected outcomes of the project. The I-540 analysis and frameworks resulting from this study focus on four major steps in the ramp metering process: 1) planning-level data collection, 2) planning-level analysis, 3) life cycle cost analysis, and 4) before-and-after installation evaluation. Ultimately, the research team found that westbound I-540 ramp meters will provide estimated benefits of between $28,234,500 and $73,410,500 over the next ten years. Although such future research is suggested, this study produces a sound foundation for evaluating ramp metering outcomes on which the state can build a ramp metering program that is both sustainable and efficient.

NCDOT RP 2021-06, The NCDOT mixture design procedure assumes 100 percent of the binder contained within reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) is available for blending with virgin asphalt. However, the literature shows that this assumption is flawed due to the presence of recycled asphalt material (RAM) agglomerations that prevent complete recycled binder availability (RBA). As a result, RAM mixtures designed using current practices may suffer from an inadequate amount of virgin asphalt, rendering them susceptible to cracking. Furthermore, past research highlights significant variability in the rheological properties of RAP and RAS stockpiles across North Carolina. Correspondingly, the objectives of this study were to: (1) modify the NCDOT’s procedures for the design of surface mixtures containing RAP and RAS to improve performance, and (2) modify the NCDOT’s current specifications to improve the consistency of RAP and RAS mixtures. To meet these objectives, a literature review was conducted that identified two approaches for addressing partial RBA in mixture design: the corrected optimum asphalt content (COAC) method specified by Georgia DOT and the availability adjusted mixture design method (AAMD) developed in NCDOT RP 2019-21. A review of plant operations was conducted to identify the range of RAP and RAS management and characterization processes in the state and select six plants to include in the experimental plan. ‘Control’ mixture designs were then identified from each of the selected plants for evaluation. The control mixtures correspond to approved Job Mix Formulas (JMFs) and thus, reflect mixture designs prepared according to current NCDOT practices. The control mixture designs were redesigned according to the COAC and AAMD approaches. The performance of the control and redesigned mixtures were evaluated through laboratory testing and pavement performance simulations. The COAC and AAMD methods produced mixtures with enhanced cracking performa

FHWA/NC/20YY-NN, Appendices included as Supplemental File, Stormwater conveyance networks contribute to stream degradation and instability either through direct discharges of sediment or by eroding gullies downslope of pipe outlets. To limit erosion downslope of pipe outlets, current regulations require the 10-yr, 24-hr peak velocity discharged to a vegetated area to be less than the downslope soils’ permissible velocity. Otherwise, the conveyance system must be redesigned. The effectiveness of this design standard has not been evaluated. North Carolina State University assessed 60 pipe outlets in the Piedmont and Mountain physiographic regions of North Carolina to identify which watershed and downslope characteristics influence the severity of erosion caused by pipe outlets. The effectiveness of the current standard was also assessed. Six assessed sites in Raleigh were additionally monitored for hydrologic, hydraulic, and water quality impacts. These data were also used to evaluate the effectiveness of a swale with (1) rip-rap, (2) well-established vegetation, (3), check dams with mowed turf grass, and (4) check dams with well-established vegetation to limit downslope erosion. The results indicate the current standard does not limit downslope erosion, and designers should consider limiting the 1-yr, 24-hr peak velocity to the permissible velocity. Designers should also consider the downslope soil and vegetative conditions to reduce the potential for gully erosion. Designers can use the predictive tools developed from the data to help determine the optimal discharge point for pipe outlets. Preliminary results suggest turf grass swales with check dams may mitigate the potential for erosion downslope of pipe outlets. However, this design should be validated with field-scale studies before standards for pipe outlets are revised.

This project aimed to implement the advances in new technologies to develop a robotic-based autonomous inspection system for underground pipelines. The new technology is based on the combination of intelligent powerful portable software and the newly advancement in mapping techniques. The system can scan and reconstruct the 3D profile of a pipeline in real-time using a networked system of ground robots. LiDAR (Light Detection and Ranging), Infrared (IR) cameras and 3D cameras with other NDT (Non-Destructive Testing) sensors used to generate the 3D profiles of the pipes as the robots with the advanced sensors autonomously move inside the pipes. During the pipe condition assessment, video files, pictures, and other scans like LiDAR and 3D are used to acquire a lot of data. This becomes cumbersome to interpret and make meaning out of. In the context of human decision-making, we aim at reducing and reordering the data to show to the human inspectors to enhance their decision performance. The proposed method is based on computer vision and pattern recognition algorithms that have proven to improve the proficiency of the inspection process in identifying and locating important features and defects. A complete technology transfer system is developed and proposed to NCDOT for implementation.