Browsing by Author "Saftner, David"

Now showing 1 - 6 of 6
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    Comparing Properties of Water Absorbing/Filtering Media for Bioslope/Bioswale Design
    (Minnesota Department of Transportation, 2017-11) Johnson, Kurt; Cai, Meijun; Patelke, Marsha; Saftner, David; Swanson, Josh
    Drainage from highways, particularly the first flush of runoff, contains high levels of contaminants such as suspended solids, metals, and organics. To restrict the discharge of polluted stormwater, the National Pollutant Discharge Elimination System (NPDES) State Disposal System (SDS) General Permit issued by Minnesota Pollution Control Agency (MPCA) in 2013 requires that the first inch of stormwater runoff from new impervious should be held on site through infiltration, harvesting or reuse. Multiple types of infiltration materials have been studied in the laboratory and the field, but few studies have considered the application of local materials for best management practices (BMP). The objective of this project is to determine the characteristics of various naturally occurring water adsorbing and filtering media, such as peat and muck, found along road construction projects in northern Minnesota. Salvage and reuse of these materials during road construction will be evaluated for stormwater treatment, including absorption, infiltration, filtration, and pollutant capture, in constructed vegetated slopes along highway right of ways. The naturally occurring material will be compared to leaf and grass feedstock compost.
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    Cone Penetration Test Design Guide for State Geotechnical Engineers
    (Minnesota Department of Transportation, 2018-11) Dagger, Ryan; Saftner, David; Mayne, Paul
    The objectives of this project are focused on a new cone penetration testing (CPT) geotechnical design manual for highway and transportation applications based on recent research and innovation covering the period from 2000 to 2018. A step-by-step procedure is outlined on how to use CPT data in the analysis and design of common geotechnical tasks. Previous manuals are either very outdated with information from 1970-1996, or not appropriately targeted to transportation works. This design document introduces modern and recent advancements in CPT research not otherwise captured in legacy manuals from the 1990's and earlier. Examples and case studies are provided for each topic interpreted using CPT measures. In the manual, a step-by-step procedure is outlined on how to use CPT data in analysis and design for typical geotechnical practices. These topics, which are applicable both to state highways and local roads, include bridge foundations (including shallow footings and deep foundations) and soil characterization (including determination of standard soil engineering properties).
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    Continued Monitoring of Stormwater Effluents from Filter Media in Two Bioslope Sites
    (Minnesota Department of Transportation, 2021-06) Cai, Meijun; Patelke, Marsha; Saftner, David
    Over the last thirty years, the Minnesota Department of Transportation (MnDOT) has implemented biofilters along roadways as a stormwater control measure. The state and national regulations require that the biofilters must be able to infiltrate and treat the first inch of rainfall onsite. However, the performance of the biofilters after installation has rarely been studied. An early phase of this project monitored two newly constructed biofilter sites for two years and for three months, respectively. This study extended the monitoring of soil moisture changes and infiltration water quality for another two years (2019-2020). Over the four-year monitoring period, both salvage peat and compost materials showed the capacity to retain the first inch of runoff, and this retention capacity did not change over the study period. The drainage water quality showed significantly temporal trends, particularly phosphorus concentrations, which were declining significantly for both compost and salvage peat. The application of tailing with compost can reduce the phosphorus release. The leachate from salvage peat has similar metal concentrations but much lower phosphorus concentrations (below 100 ppb) than the compost. The lowest chemical concentrations were achieved when the soil mixture contained 10% compost and 10% salvage peat, implying the best stormwater control practice is to limit the organic ratio to around 20%. Findings from this work determined the validity of using peat and compost for future biofilters and can aid in future design.
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    Development and Regionalization of In Situ Bioslopes and Bioswales
    (Minnesota Department of Transportation, 2019-07) Johnson, Kurt W.; Cai, Meijun; Patelke, Marsha; Saftner, David; Cruz, Chanelle
    This project is a multi-disciplinary investigation into the use of alternative media for biofiltration systems in Minnesota. Over the last thirty years, the Minnesota Department of Transportation (MnDOT) has implemented biofilters along roadways as a stormwater control measure. These systems must be able to infiltrate and treat the first inch of rainfall onsite to meet state and national regulations. The performance of a biofilter is largely based on its media?s ability to infiltrate water, sustain vegetation, and capture pollutants. To date, MnDOT has relied on sand and compost mixtures for biofilter media components. An early phase of this work identified peat as having similar performance characteristics as compost, making it an ideal alternative. A laboratory testing program was also developed during the early phase of work to determine media properties that could be used to predict biofilter performance. This project focused on characterizing existing biofilters using in situ testing and comparing results to laboratory testing. The comparison of the two methods demonstrated the predictive capabilities of the laboratory regime. This project also included the instrumentation and monitoring of field sites including a newly constructed peat amended biofilter. Findings from this work determined the validity of using peat for future biofilters and can aid in identifying and characterizing other alternative media.
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    Re-use of Regional Waste in Sustainably Designed Soils
    (Minnesota Department of Transportation, 2022-04) Saftner, David; Cai, Meijun; Whitcomb, Adam
    This project explores the potential re-use of waste materials/by-products as a soil amendment in northeastern Minnesota. The project team identified 23 waste/by-products and collected 15 of but only analyzed 11 because of the possible content of persistent chemicals in some of the materials or the unwillingness of the owner to participate. Peat screenings, peat scrapings, tree bark, harbor dredge sediment, coarse and fine taconite tailings, and street sweepings were characterized in physical, chemical, and biological properties through lab tests. The results showed that none of the studied materials were defined as hazardous based on RCRA (Resource Recovery and Conservation Act) metal levels and contained minimal or undetectable Polychlorinated biphenyls (PCBs), Polycyclic Aromatic Hydrocarbons (PAHs) or Volatile Organic Compounds (VOCs). Peat by-products were efficient in removing metals from stormwater runoff. The relatively high phosphorus content of peat by-products provided sufficient nutrients to plant growth but could be released when mixed with low-phosphorus runoff. Dredge sediment and street sweeping had low organic contents but could remove 90% or more of the copper from the runoff. Tailings could remove 50% or less of the metals. Radish or oat can successfully grow in 28 days with individual materials or a blend of materials, except for fine tailings, which are in a clay form and thus don't filter water well.
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    Slope Stabilization and Repair Solutions for Local Government Engineers
    (Minnesota Department of Transportation, 2017-06) Saftner, David; Carranza-Torres, Carlos; Nelson, Mitchell
    The purpose of this project is to create a user-friendly guide focusing on locally maintained slopes requiring reoccurring maintenance in Minnesota. This study addresses the need to provide a consistent, logical approach to slope stabilization that is founded in geotechnical research and experience and applies to common slope failures. Authors used input from Minnesota county engineers, case studies from site investigations throughout the state, and a parametric study of slope stability modeling parameters to develop stabilization recommendations. The project, beginning in September 2015, consisted of four primary research phases. In Task 1, researchers identified slopes for further analysis via a survey sent to each county engineering department in the state. Responses provided site investigation locations. Researchers conducted site investigations and developed case studies to analyze slope stabilization methods. Task 2 involved performing a literature review to identify slope stabilization methods. In Task 3, laboratory testing characterized soil properties from case study sites. Additionally, limit equilibrium method (LEM) models were developed for each slope to investigate different stabilization methods in a parametric study. In Task 4, modeling and analysis results were summarized for distribution to local government engineers. The target audience of the guide is county or local municipal engineers who do not have specialized geotechnical engineering experience. The research does not address slope stability issues of the scale that require local municipalities to hire geotechnical engineering specialists. Authors intend the deliverable to assist with efficient stabilization of common recurring slope failures along roadways.