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This report outlines the development of a suite of computer codes collectively referred to as MnDrain. These codes, embedded in a standard spreadsheet program, provide a user-friendly environment in which the consequences of an edge drain design decision can be investigated. The purpose of an edge drain is to remove moisture from the granular base of the road system. The rate at which moisture is removed will depend on the geometry and materials used in the base and the soil type in the subgrade. MnDrain allows for evaluation of a given drain design against Federal Highway Administration requirements. In MnDrain, the user can chose from three basic scenarios, select material types and adjust geometries for each scenario, and calculate the moisture removal versus time curve over a two-hour drainage time. The work in this report shows that MnDrain is easy to use, flexible, and produces accurate approximate solutions of the Richard's model of variable saturated flow in a layered media. MnDrain also offers the advantage of offering free access to all source codes, which means that MnDrain can be reconfigured to deal with a large array of pavement drainage issues.

This report focuses on an unsaturated flow model for research on the effects of moisture in pavement, which is a more comprehensive approach for determining roadway drainage. Results establish that SEEP/W software is a valuable tool for modeling unsaturated flow and that time to drain calculations based on unsaturated flow theory will generally be longer than time to drain evaluated under saturated flow assumptions.

This paper summarizes current subsurface pavement drainage used by various state and local agencies. The paper starts with a brief introduction on moisture in a pavement and the damage it can cause. Following the introduction, the relative effectiveness of subsurface drainage is estimated based on environmental conditions, traffic levels, and physical characteristics of the pavement structure. The next three sections of the paper discuss various components used in subsurface drainage, combinations of drainage components to perform specific drainage tasks, and maintenance required to keep drainage components functioning. Next, results from a survey sent to Minnesota city and county agencies are given summarizing current drainage practices used on lower volume roads. Finally, the last part of the paper gives cost and performance data on drainage systems used by various states.

The MnDOT Bridge Office sought out information on best practices regarding the use of drainage systems on bridges. Minnesota regulations strongly discourage the discharge of runoff directly into waterways; however, bridge drainage systems can lead to accelerated deterioration in bridge elements. MnDOT requested a synthesis to gather information to assist them in future development of guidance on design, detailing, specifications, construction, and maintenance procedures for bridge needs, focusing specifically on agencies with similar northern climates to the greatest extent possible.

The report presents the literature relating to design of thermoplastic pipe, describes the development and implementation of field tests conducted for this project, extends the findings of the field tests through calibration of two- and three-dimensional computer models and parametric studies, and makes recommendations for design and installation of thermoplastic pipe under shallow cover and highway live loads.

This study provides design information for temporary stormwater ponds with floating head skimmers. The purpose of the ponds is to remove suspended sediment and nutrient loads from stormwater runoff on active construction sites. The design information is directed at meeting the standards in the National Pollution Discharge Elimination System (NPDES) general permit which includes storing runoff from the 2-year, 24-hour rainfall event or providing the equivalent sediment control. The study results include: Research of currently available floating head skimmers, Estimation of runoff hydrology and hydraulics from active constructions sites using HydroCAD, Estimation of water quality improvements using P8, and Design plans. The study shows several available technologies for pond skimming. The pond and skimmer design manages a 2- year, 24-hour rainfall event while removing an average of 80 percent of total suspended solids (TSS) from runoff. Smaller systems do not operate equivalently without additional treatment such as adding flocculants. Plans, maintenance requirements, and special provisions are included.

Roadside swales are drainage ditches that also treat runoff to improve water quality, including infiltration of water to reduce pollutant load. In the infiltration study, a quick and simple device, the Modified Philip Dunne (MPD) infiltrometer, was utilized to measure an important infiltration parameter (saturated hydraulic conductivity, Ksat) at multiple locations in a number of swales. The study showed that the spatial variability in the swale infiltration rate was substantial, requiring 20 or more measurements along the highway to get a good estimate of the mean swale infiltration rate. This study also developed a ditch check filtration system that can be installed in swales to provide significant treatment of dissolved heavy metals and dissolved phosphorous in stormwater runoff. The results were utilized to develop design guidelines and recommendations, including sizing and treatment criteria for optimal performance of the full-scale design of these filters. Finally, the best available knowledge on swale maintenance was combined with information obtained from new surveys conducted to develop recommendations for swale maintenance schedules and effort. The recommendations aim toward optimizing the cost-effectiveness of roadside swales and thus provide useful information to managers and practitioners of roadways. The research results and information obtained from this study can thus be used to design swale systems for use along linear roadway projects that will receive pollution prevention credits for infiltration. This will enable the utilization of drainage ditches to their full pollution prevention potential, before building other more expensive stormwater treatment practices throughout Minnesota and the United States.

Culvert pipe material selection has traditionally been a relatively simple task involving metal or concrete pipe. In recent years, the addition of coated metal and plastic pipe has led the federal government to implement a rule requiring the consideration of alternative pipe materials. The current MnDOT Drainage Manual provides limited guidance on the selection of pipe material. The manual is lacking detailed information on the influence of environmental conditions on pipe durability in Minnesota. It is necessary to provide updated, accurate information on pipe material and durability for factors directly related to Minnesota. To reach this goal, the availability and suitability of existing data, as well as the practices associated with predicting pipe life spans must be evaluated. This report is the result of the initial feasibility study for a larger project(s) to update the MnDOT Drainage Manual. The goal for this report is to identify knowledge gaps, produce a research plan that will guide future research, and draw any pipe materials conclusions possible using the data available.

Roadside drainage ditches (roadside grassed swales) typically receive runoff directly from the road and water is infiltrated over the side slope of the ditch, similar to a filter strip. Water that runs off the side slopes then has a further opportunity to infiltrate as it flows down the center of the ditch. This research focuses on the volume reduction performance of grassed drainage ditches or swales by infiltration. A total of 32 tests were performed during three seasons in four different highways maintained by MnDOT in the Twin Cities metro area. The field-measured saturated hydraulic conductivities (Ksat) correspond to hydrologic soil group A, even though the soil textures indicated correspondence to hydrologic soils groups A, B and C. This means that the infiltration performance is better than expected for these types of soils. In addition, the trend was to have more infiltration when the saturated hydraulic conductivity was higher and for a greater side slope length, as expected. A coupled overland flow-infiltration model that accounts for shallow concentrated flow has been developed. The predicted infiltration loss has been compared with the actual infiltration loss determined from the monitored field tests. In this manner, the validity of the model as well as the associated soil hydraulic and surface geometry parameters have been evaluated. Using the coupled infiltration-overland flow model, multiple scenarios with sensitivity analyses have been computed, and the results have been used to generate a simplified calculator to estimate the annual infiltration performance of a grassed roadside drainage ditch.

To determine whether the distress observed in MnROAD test sections was unique, researchers examined six other Minnesota concrete pavement projects of similar age and material. Similar types of distress were found but the extent of damage was not as severe and sections with base layers that adequately drained water within the joints performed significantly better.