Browsing by Author "Nieber, John L."
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Item Assessing and Improving Pollution Prevention by Swales(St. Anthony Falls Laboratory, 2014-08) Gulliver, John S.; Ahmed, Farzana; Natarajan, Poornima; Weiss, Peter T.; Nieber, John L.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.Item Assessing and Improving Pollution Prevention by Swales(Center for Transportation Studies, University of Minnesota, 2014-08) Ahmed, Farzana; Natarajan, Poornima; Gulliver, John S.; Weiss, Peter T.; Nieber, John L.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.Item Assessment of Stormwater Best Management Practices(University of Minnesota, 2008-04) Anderson, James L.; Asleson, Brooke C.; Baker, Lawrence A.; Erickson, Andrew J.; Gulliver, John S.; Hozalski, Raymond M.; Mohseni, Omid; Nieber, John L.; Riter, Trent; Weiss, Peter; Wilson, Bruce N.; Wilson, Matt A.; Gulliver, John S.; Anderson, James L.Item Cost Analysis of Alternative Culvert Installation Practices in Minnesota(Minnesota Department of Transportation, 2009-06) Hansen, Brad; Nieber, John L.; Lenhart, ChristianVarious factors associated with conventional culvert design, including shallow water, perched inlets and high flow velocities, can cause difficulties for migrating fish and affect their genetic diversity and long-term survival. Conventional culvert design has traditionally been based on hydraulic conveyance, safety and cost. Recently, some alternative culvert designs have been developed to facilitate salmon migration on the west coat of the United States. These alternative designs focus on matching the natural dimensions and characteristics of the stream channel through the culvert. The intended purpose of these newer designs is to provide unimpeded passage of aquatic life, reduce maintenance costs and improve erosion control. Currently, some of these new designs are being implemented in Minnesota mostly when fish passage is a consideration. There are concerns about the additional costs associated with these alternative designs as well as whether they are really needed at some road crossings. The objectives of this research were to summarize state-wide fish passage concerns related to culvert road crossings on public waters and to perform a cost comparison between the conventional and the alternative culvert designs.Item Design and Construction of Infiltration Facilities(Minnesota Department of Transportation, 2021-06) Tecca, Nicholas P.; Gulliver, John S.; Nieber, John L.; Weiss, Peter T.Infiltration stormwater control measures are an important structural practice to mitigate the impacts of urbanization on stormwater quality and quantity. Infiltration stormwater control measures help to mimic the natural processes of infiltration and evapotranspiration. Unfortunately, the failure rate of infiltration stormwater control measures has been observed to be between 10% and 50%. Two common causes of failure are addressed in this work, namely improper siting and improper characterization of saturated hydraulic conductivity. A procedure to calculate a preliminary infiltration rating (PIR) was developed in a geographic information system to identify areas where infiltration stormwater control measures are likely to be successful. The Modified Philip-Dunne infiltrometer, double ring infiltrometer, Turf-Tec IN2-W infiltrometer, and soil texture analysis were used to estimate infiltration capacity in three swales in the Twin Cities Metropolitan area. A correction factor was proposed for the Turf-Tec IN2-W infiltrometer. A protocol for assessing infiltration capacity was also proposed.Item The development and application of a four-level rain garden assessment methodology(St. Anthony Falls Laboratory, 2007-11) Asleson, Brooke C.; Nestingen, Rebecca S.; Gulliver, John S.; Hozalski, Raymond M.; Nieber, John L.The Minnesota Pollution Control Agency (MPCA) and the Metropolitan Council Environmental Services (MCES) provided funding for this project. The involvement of the project manager from the MPCA, Bruce Wilson, and the project officer from MCES, Jack Frost, was greatly appreciated. The Technical Advisory Panel (TAP) for the project whom provided insightful and experienced advice throughout the project added to the usability of the final product. The assistance of several undergraduate studentsā Geoff Kramer, Nicolas Olson, and Thomas Natwick was undoubtedly a critical component leading to the final outcome of this project. Their hard work is very much appreciated. The staff at St. Anthony Falls Laboratory (SAFL) provided assistance in the construction of equipment necessary for this project. University of Minnesota facilities management and the City of Little Canada provided assistance with the use of fire hydrants for this research. Several partnerships were developed through this project and provided additional insight to this work. I would like to thank the Ramsey Washington Metro Watershed District (RWMWD) for their enthusiastic involvement with this project, especially Cliff Aichinger who also served on the TAP. The Dakota County Soil and Water Conservation District and Washington County Conservation District were conducting similar work and the cooperation of our efforts aided in the successfulness of this work.Item Enhancement and Application of the Minnesota Dry Swale Calculator(Center for Transportation Studies, University of Minnesota, 2016-04) Garcia-Serrana, Maria; Gulliver, John S.; Nieber, John L.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.Item Evaluating Roadway Subsurface Drainage Practices(Minnesota Department of Transportation, 2009-01) Canelon, Dario J.; Nieber, John L.This project involved the evaluation of some configurations of pavement subsurface drainage systems, including the conventional edgedrain system, and two centerline configurations, at 2-foot and 4-foot depths. Testing of these configurations took place on a newly constructed eight-mile section of Nobles County CSAH 35 near Worthington. Drained roadway sections were 500 feet long for each drainage treatment. Each of the treatments was replicated six times, with the outflow for each replication outlet through a tipping-bucket flow monitoring system. The experimental design tested both the drain configuration and the effect of relative elevation of the roadway. Measurement of relative wetness of the pavement base and subgrade materials for each of the drainage treatments was conducted with a Geonics electromagnetic induction instrument (EM38). Data were collected from March 2006 until November 2008, with breaks during the winter periods. Statistical analyses were conducted to look for treatment effects, using both drained volumes as well as the EM38 measurements as measures of drain efficacy. Additional project work included a finite element analysis of the drainage configurations, EM38 evaluation of drainage effectiveness of an open-graded base construction for streets in the city of Worthington, and evaluation of the potential drain plugging effect of crushed concrete fill.Item Evaluation of Buffer Width on Hydrologic Function, Water Quality, and Ecological Integrity of Wetlands(Minnesota Department of Transportation, 2011-02) Nieber, John L.; Arika, Caleb; Lenhart, Christian; Titov, Mikhail; Brooks, Kenneth N.Human activities including agricultural cultivation, forest harvesting, land development for residential housing, and development for manufacturing and industrial activities can impair the quality of water entering the wetland, thereby detrimentally affecting the natural ecological functions of the wetlands. This can lead to degradation of biota health and biodiversity within the wetland, reduced water quality in the wetland, and increased release of water quality degrading chemicals to receiving waters. Under natural conditions wetlands develop buffer areas that provide some protection from the natural processes occurring on adjacent areas of the landscape. Buffers serve the function of enhancing infiltration of surface runoff generated on adjacent areas, thereby promoting the retention of nutrients in the soil, and retention of sediment suspended in the runoff water, while still allowing runoff water to reach the wetland through subsurface flow routes. To protect wetlands and receiving waters downstream from the wetlands it is important that wetlands in areas disturbed by human activities be provided with sufficient buffer to prevent degradation of wetland biotic integrity as well as degradation of wetland water quality. The question arises, āHow much buffer is sufficient?ā The objective of this study was to investigate the sufficiency of buffers to protect wetland biotic integrity and water quality, and to evaluate the benefits extended to wildlife by the habit available in wetland buffers. The study was conducted by using a wetland data base available for 64 wetlands in the Twin Cities metro area.Item Evaluation of Computed Tomography to Determine the Distribution of Macropores in Soil(Water Resources Research Center, University of Minnesota, 1991-08) Nieber, John L.; Warner, Glenn S.Preferential flow paths in some soils result in the rapid movement of water and associated chemicals to groundwater. Macropores are one type of preferential path. Examples of macropores include earthworm tunnels, decayed root channels, shrink/swell cracks, tillage cracks, etc. Water movement through a soil can potentially be modeled if the number, size and extent of the macropores are known. At present no easy and accurate method of characterizing macropores has been developed. X-ray computed tomography (Cf), developed for medical purposes, uses scan techniques to secure multiple views of an object and provides ameans of obtaining nondestructive internal cross sections of objects. The spatial resolution of modern scanners is on the order of I mm, providing a potential means of detecting small air-filled pores within the soil. Undisturbed soil cores, 200 mm in diameter, were taken in cultivated and uncultivated areas. A medical Cf scanner was used to scan these cores at depth intervals varying from 10 mm to 50 mm. Data for each scan were analyzed using microcomputers to display images and to determine the size and number of macropores for each scan image. Cores were physically sectioned at scan locations to visually compare the size, location and continuity of macropores in the sections with those shown in the scan images. Laboratory cores packed with soil were scanned as standards to determine the response and contrast resolution of the Cf scanner for dense material containing sharp density discontinuities. Cores were packed with different types and densities of soil. Artificial "macropores" were formed in some packed cores using glass tubes and holes formed with wire probes to assess the resolution of the scanner. Macropores of various sizes and types were found in all of the field cores scanned with the majority of macropores being associated with earthworm tunnels. The number and size of macropores were approximately the same for all cores below a depth of approximately 50 mm. The number of macropores found above this depth was affected by a large number of roots in the grass-surfaced core and by tillage in the bare-surfaced core. Many macropores were continuous to depths of 600 mm or more. Some passed completely through the core. Dye tests and physical sampling revealed that some of the macropores functioned as preferential flow paths and had very high flow rates. Analysis of the packed cores revealed that the detection of small holes in a dense medium by Cf depends not only on the size of hole but also on the density of the medium. Various attenuation values were examined to determine the optimal threshold value to use for the detection and measurement of macropores in the field cores. The average attenuation value for air in the holes in the cores was not zero as was initially assumed, but varied with the size of hole. The results showed that a CT scanner can accurately determine pore locations and sizes for pores I mm or larger. Accurate determinations of macropore characteristics require that proper values of parameters for the medium and conditions being analyzed be assessed. Use of microcomputers greatly enhanced the ability to display images, analyze features of interest, detect and characterize individual macropores. The main conclusion of the study was that the Cf scanner when coupled with use of computers is a potentially valuable tool for characterizing macropores.Item Impact of Alternative Storm Water Management Approaches on Highway Infrastructure: Guide for Selection of Best Management Practices - Volume 1(2006-02-01) Arika, Caleb; Canelon, Dario J.; Nieber, John L.; Sykes, Robert D.Highway infrastructure represents a substantial portion of the total impervious areas that generate runoff water. Because of long winters in congested areas that require frequent applications of de-icing materials, much of the runoff has the potential for affecting downstream water quality. However, storm water management techniques themselves have the potential for compromising the integrity of adjacent highways when they result in significant increases of water content in the soil beneath the roadway.Because of impacts and the costs associated with construction and maintenance, any storm water management system needs to be assessed before any decisions are made regarding new highway development or redevelopment. The authors consider Best Management Practices (BMPs) as they relate to the most commonly used storm water management approaches including dry ponds, wet ponds, infiltration trenches, infiltration basins, constructed wetlands, grassed swales, bioretention cells, sand filters and porous pavements. They provide a framework for considering cost of practices, negative impact on infrastructure, results from a BMP-related survey of highway design and maintenance professionals and cost-estimation formulas for each of the most commonly used storm water management approaches in urban Minnesota.
Item Impact of Alternative Storm Water Management Approaches on Highway Infrastructure: Project Task Reports - Volume 2(2006-02-01) Arika, Caleb; Canelon, Dario J.; Nieber, John L.; Sykes, Robert D.Highway infrastructure represents a substantial portion of the total impervious areas that generate runoff water. Because of long winters in congested areas that require frequent applications of de-icing materials, much of the runoff has the potential for affecting downstream water quality. However, storm water management techniques themselves have the potential for compromising the integrity of adjacent highways when they result in significant increases of water content in the soil beneath the roadway.Because of impacts and the costs associated with construction and maintenance, any storm water management system needs to be assessed before any decisions are made regarding new highway development or redevelopment. The authors consider Best Management Practices (BMPs) as they relate to the most commonly used storm water management approaches including dry ponds, wet ponds, infiltration trenches, infiltration basins, constructed wetlands, grassed swales, bioretention cells, sand filters and porous pavements. They provide a framework for considering cost of practices, negative impact on infrastructure, results from a BMP-related survey of highway design and maintenance professionals and cost-estimation formulas for each of the most commonly used storm water management approaches in urban Minnesota.
Item The Impact of Stormwater Infiltration Practices on Groundwater Quality(St. Anthony Falls Laboratory, 2014-07) Nieber, John L.; Arika, Caleb; Lahti, L.; Gulliver, John S.; Weiss, Peter T.Establishing enhanced infiltration sites for the control of stormwater runoff in developed areas is becoming a common practice among municipalities, departments of transportation, other government entities, and private entities. One of the purposes of enhanced filtration is to control the volume and rate of runoff from developed areas in order to keep the level of runoff close to that of undeveloped conditions. Another purpose is to capture the stormwater so that contaminants contained in the stormwater will be treated through the process of water infiltrating and flowing through the soil profile. With the increasing adoption of enhanced infiltration practices there is a growing concern that these practices might be putting the quality of the groundwater resources underlying some of these practices in jeopardy. In recent years there have been some efforts to quantify the potential for degradation of groundwater resources by infiltrated stormwater. The study described in this report is an effort to quantify the potential for contaminants to reach the groundwater resources in the Twin Cities Metropolitan Area, Minnesota. A literature review was first conducted to identify concerns with regard to groundwater contamination and the extent of the research that has been completed with regard to these issues. The field study was then conducted over a period of 18 months in which three sites containing enhanced infiltration practices were monitored to quantify the amount of contaminants reaching depths large enough to infer that the contaminants would eventually reach the underlying surficial aquifer. The sites investigated included an infiltration basin near the St. Paul campus of the University of Minnesota (referred to as the Sheep Pasture, SP), a large infiltrating rain garden located within Como Park (referred to as the Hamline-Midway Ave. site, HM), and an infiltration gallery constructed in a formerly industrial area located at Beacon Bluff (referred to as BB) in the eastern side of St. Paul. These sites were selected from a number of potential sites based on the criteria: 1) should have been functioning long enough to contain contaminants; (2) be local for convenience of access; and (3) represent one of the infiltration practices that are of primary concern with regard to groundwater pollution.Item Implementation of Methodology for Weed Management Practices(Minnesota Department of Transportation, 2009-02) Arika, Caleb N.; Nieber, John L.; Wyse, Donald L.; Moon, Roger D.A study initiated in 2004/2005 in District 4 of Mn/DOT compared the use of 100 1/4-mi long segments against seven 3-mi segments on sampling precision for the estimation of weed infestations in highway rights-of-way for Canada thistle (Cirsium arvense (L.)(Scop.), leafy spurge (Euphorbia esula L.), and poison ivy (Toxicodendron radicans). The comparison showed that the 3-mi and 1/4-mi plans yielded equivalent estimates of mean weed population density, although the results indicated that at the district level precision was greater with the 1/4-mi plan. Further investigations suggested that additional improvements in precision and efficiency would likely occur if segment lengths were shortened to 125ā or less. The project implementation phase reported here aimed to investigate efficiencies of two sampling plans, one with weed density measured over 100, 225-ft segments, and one with presence/absence of weeds measured over 150, 14-ft segments. Results showed that the presence-absence surveys almost consistently underestimated the area infestation derived from the 225-ft surveys. The 14-ft survey required substantially less time to conduct, but at this time they appear to be less precise than the 225-ft surveys with regard to quantifying infestation density. It is recommended that an additional season of survey data be analyzed to better quantify the precision of the 14-ft survey results.Item Implementation of Methodology for Weed Management Practices ā Phase II(Minnesota Department of Transportation, 2009-09) Arika, Caleb N.; Wyse, Donald L.; Nieber, John L.; Moon, Roger D.In 2008 a Phase II implementation project was conducted to test whether presence/absence surveys could provide accurate and cost effective estimates of invasive weed species infestation in roadway rights-of-way within Mn/DOT District 4. A 225-ft survey, in which infested areas were mapped, was used as the standard for comparison to the presence/absence surveys which were conducted using 14-ft āstick walksā. A 2007 Phase I project had shown the presence/absence surveys to be more cost effective, but the infestation estimates were consistently lower than the standard. The 2008 study provided additional data to test the efficacy of the presence/absence surveys. The results of the 2008 study showed that the presence/absence surveys were significantly less costly than the standard, but the estimates of infestation themselves were not satisfactory relative to the standard scheme. From this study it is concluded that surveys should be conducted using the 225-ft sampling scheme for invasive species that form contiguous patches. The lower cost of the presence/absence surveying scheme might make it a good option for sampling of invasive weed species infestations for the case of rare species such as poison ivy which do not typically form contiguous patches.Item Management Practices for Weed Control in Roadway Rights-of-Way(Minnesota Department of Transportation, 2007-10) Arika, Caleb; Wyse, Donald; Nieber, John L.; Moon, Roger D.By law, Departments of Transportation are required to control noxious weeds along highway rights-of-way (ROWs). Since 2000, District 4 (D4) of Minnesota Department of Transportation (Mn/DOT) adopted a survey design consisting of n= 7, 3-mi segments to quantify infestations of Canada thistle (Cirsium arvense (L.)(Scop.), leafy spurge (Euphorbia esula L.), and poison ivy (Toxicodendron radicans) in chosen regions of the district. In 2004 and 2005, a second survey design was added to see if stratification by ecozone in D4, and greater numbers of 1/4-mi segments could improve precision. Comparison of matching sample statistics from the 3-mi and 1/4-mi plans in each year indicated the two plans yielded equivalent estimates of mean acres per roadway mile of each weed (a = 0.05). However, precision at the district level was much greater in all cases with the 1/4-mi plan. In addition, weed abundances varied substantially among ecozones (a < 0.05); this knowledge will allow managers to direct control efforts to problem areas. Finally, a combination of computer based mapping and resampling of the 1/4-mi segments observed in the two years suggests that additional improvements in precision and efficiency are likely to occur if segment lengths are shortened to 125' or less. Shorter segments would reduce inspection costs, increase sample sizes, improve precision, and possibly allow conversion from an area-measurement approach to one based on presence or absence of chosen weeds in selected segments. Plans are underway to compare the latter two approaches in 2007.Item Measurement of Flow through the Unsaturated Zone Using a Prototype Funnel Lysimeter(Water Resources Research Center, University of Minnesota, 1994-05) Alexander, E. Calvin, Jr.; Foster, Michael B.; Misra, D.; Nieber, John L.Prototype funnel lysimeters were constructed using 2-m dia. tree transplanting equipment. This equipment offers a possible means for quantitative, practical, and cost-effective measurement of flow in the unsaturated zone at the meter scale. The objective of this investigation was to develop and test the funnel lysimeter as a practical field methodology to conduct controlled quantitative tracer tests on large undisturbed soil samples. The steps to achieve this objective were to develop a working prototype, conduct tracer tests at sites with different field soils and a repacked soil in the laboratory, determine the characteristics of tracer breakthrough curves for the test soils, and assess the degree to sample disturbance caused by the lysimeter installation process. Lysimeters were installed by temporarily excavating a 2-m(3) soil sample using the tree transplanter and then replacing the sample after the installation of a sump and funnel-shaped impermeable liner. Tracer experiments were then carried out by applying solutes at the surface and sampling from the sump using an automatic sampler. Seven funnel field lysimeters were installed in Minnesota over two field seasons in three different soil types. Experiments identified two distinct flow types: preferential and matrix flow. In a typical field experiment with the preferential-flow soil, discharge at the lysimeter sump occurred within 15 minutes of the start of a six minute tracer application; discharge of the tracer stated after 23 minutes. For the matrix-flow soil, discharge to the sump typically took several hours to respond to tracer application. Drainage to the sump in the same cycle was composed of 100% antecedent water. The installation method does not lead to major disturbance of the soil but is more effective in sandy soils. The experimental results indicate that the funnel lysimeter methodology is suited for wide application in subsurface hydrology because of its large sample size, a time scale resolution of minutes, and mass balance control. Essential technological improvements to the lysimeter and further tracer experiments are required to fully define the lysimeter flow characteristics.Item Modeling soil water variability(University of Minnesota, Water Resources Research Center, 1987-06) Bakovic, Ivo L. Lopez; Nieber, John L.This report demonstrates the process of simulating the temporal and spatial variability of soil water.Item Performance Assessment of Oversized Culverts to Accommodate Fish Passage(Minnesota Department of Transportation Research Services Section, 2011-08) Hansen, Brad; Johnson, Sara; Nieber, John L.; Marr, JeffIn Minnesota there is not a standard culvert design used at road crossings to improve aquatic organism or fish passage. The design process for fish passage in Minnesota is currently based on the knowledge and experience of local county, state and DNR personnel. The design methodology attempts to maintain the natural stream dimensions, pattern and profile through the culvert crossing. If designed properly aquatic organisms and fish that can make it upstream to the culvert should be able to pass through the culvert. This research was conducted to better understand the hydraulic conditions related to the practice of recessing culverts and other fish passage design elements over a range of landscapes in Minnesota. The design elements analyzed included bankfull width, slope, channel materials, side barrels and recessed culverts. Nineteen culvert sites were survey around the state. The main criterion used to evaluate performance of the culverts was the presence or absence of adequate sediment in the recessed culvert barrel. Six of the fourteen sites with recessed barrels had no sediment accumulation. A likely reason that these culverts lack sediment was increased velocities due to improper sizing relative to bankfull channel width and the accumulation of sediment in the side barrels. Wider Rosgen āCā type channels also correlated with performance issues related to culvert design.Item Performance of Low Impact Development Practices on Stormwater Pollutant Load Abatement(St. Anthony Falls Laboratory, 2011-08) Ahmed, Farzana; Gulliver, John S.; Nieber, John L.Stormwater runoff is a major contributor to the impairment of surface waters in the United States. With high connected impervious surfaces and concentrated human activities, urban land uses are involved in discharging most of the stormwater volume and pollutant loadings during a storm. Stormwater pollution prevention involves the installation and maintenance of stormwater low impact development (LID) practices in urban areas. These include infiltration basins and trenches, porous pavements, rain gardens, vegetative swales, and filter strips. LID practices infiltrate and detain stormwater to reduce stormwater runoff volume and improve water quality via filtration and other processes. The reasons for assessing the performance of the LID practices include fulfilling stormwater permit regulatory requirements, engineering and design due diligence, scheduling maintenance and TMDL studies. The results of the assessment allow for an improved understanding of the role of the various system components (i.e. soil, plants, etc.) in pollutant removal and volume reduction. This project is designed to assist MS4s in the assessment of their stormwater BMPs and the utilization of these BMPs in watershed TMDL analyses. Objective B of this project focuses on the infiltration performance of low impact development (LID) practices. The infiltration capacity testing developed for rain gardens (Asleson, et al. 2009) was to be refined, altered and expanded for other types of LID practices including infiltration basins and trenches, vegetative swales and filter strips. The Modified Philip Dunne (MPD) infiltrometer is implemented as a low-effort, low-cost method to determine saturated hydraulic conductivity, a predictor of infiltration capacity. This infiltration tests have been performed on rain gardens, infiltration basin, swales and turf areas.