Identification of Research Needs Related to Highway Runoff Management (2004) / Chapter Skim
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From page 57... ...
3.1. BRIEF REVIEW OF RECENT MAJOR SYNTHESES OF HIGHWAY RUNOFF/URBAN STORMWATER QUALITY RESEARCH Several researchers have attempted to compile and summarize highway runoff/urban stormwater quality research and data, including BMP evaluation studies and performance data.
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For example, BMPs that rely on settling as a primary removal mechanism cannot have high percent removals where suspended solids concentrations are low in the influent. The influent data in the dryextended detention ponds in the database are relatively Category Records in Database General Test Site Information 158 Sites Sponsoring and Testing Agencies 60 Agencies Watershed Information 167 Watersheds Nonstructural BMPs Information 28 BMPs Structural BMPs Information 170 BMPs Monitoring Stations 557 Monitoring Stations Precipitation Data 3,396 Precipitation Events Flow Events Monitored 6,563 Flow Events Monitored Water Quality Sampling Event Data 8,588 Water Quality Events Monitored Water Quality Laboratory Analyses 122,265 Analyses Conducted TABLE 3-1 Summary of records found in ASCE/EPA BMP Database (as of August 2002)
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BMPs Type Number of BMPs in Category, Including Design Information Precipitation Records for BMPs Type1 Flow Records for BMPs Type1 Water Quality Records for BMPs Type1 Detention Basin 24 129 229 4,209 Grass Filter Strip 32 227 385 6,251 Media Filter 30 187 327 6,144 Porous Pavement 5 5 5 55 Retention Pond 33 378 817 14,293 Percolation Trench and Dry Well 1 3 3 21 Wetland Channel and Swale 14 53 113 1,241 Wetland Basin 15 221 681 7,320 Hydrodynamic Devices 16 169 309 6,186 Total 170 1,372 2,869 45,720 1 Only events that included the collection of event mean concentrations have been included in the summary statistics presented in this table. TABLE 3-2 Summary of data by structural BMP type (as of August 2002)
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To facilitate this compatibility, the site recommends use of Urban Stormwater BMP Performance Monitoring: A Guidance Manual for Meeting the National Stormwater BMP Database Requirements, of which there have been more than 25,000 downloads to date. In addition to the detailed BMP monitoring and data analysis guidance provided in the manual, the guidance manual includes lists of required and recommended data elements, or metadata, that should be reported with BMP performance data, including specific information for individual BMP types.
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. Water quality monitoring studies have demonstrated the wide variability in water quality concentrations in storm61 water runoff; with more consistent effluent quality from BMPs, percent removal becomes a function of how polluted the inflow is.
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3.1.5. Center for Research in Water Resources: Highway Runoff Literature Review Barrett et al.
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More advanced evaluations have included attempting to associate performance with specific site conditions or design variables, evaluating methods to improve pollutant removal in existing drainage systems, and characterizing the water quality achieved rather than the removals. Furthermore, some BMP evaluations may have looked beyond the pollutant removal effectiveness through the use of surrogate performance measures, such as the hydraulic regimes (hydraulic residence, bypass volume, etc.)
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The literature shows significant variation among the methods used to collect and analyze such water-quality data and make inferences about BMP performance. ASCE, in cooperation with the EPA, attempted to develop a standard BMP performance monitoring protocol through the publication of Urban Stormwater BMP Performance Monitoring: A Guidance Manual for Meeting the National Stormwater BMP Database Requirements (GeoSyntec Consultants, 2002)
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. By definition, the SOL is equal ER = −1 average outlet EMC average inlet EMC Innovative Technique or Technology Number of States Using Practice Number of States Not Using Practice Water quality inlets 16 32 Constructed wetlands 32 16 Grassed/vegetated swales and buffer strips 43 5 Wet ponds 31 17 Dry ponds 39 9 Wet vaults/tanks 9 38 Dry vaults/tanks 6 41 Porous/permeable pavement designs 5 42 Oil and water separators 27 21 Silt fences 31 16 Infiltration basin/trench 32 15 Sand filter 15 32 Low impact design 11 36 Hydrodynamic ultra-urban BMPs 9 38 Filtration ultra-urban BMPs 14 33 Natural stream channel design and stabilization 24 22 Herbicide alternatives for roadside vegetation maintenance 23 23 Gross solid separators (trash)
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This method weights all storms equally and does not account for pollutant storage and release during successive storm events. The most serious shortcoming of this method is the assumption of effluent quality dependence on influent quality, particularly when applied to detention storage BMPs that have residence times greater than the storm event duration.
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Urban Stormwater BMP Performance Monitoring: A Guidance Manual for Meeting the National Stormwater BMP Database Requirements. American Society of Civil Engineers and U.S.
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Erosion controls, which are designed to hold soils in place either temporarily during construction or permanently on cut–fill slopes, will be addressed in a separate subsection. Some common research questions with regard to gross pollutant removal include • How effective are source controls -- such as street sweeping, catch basin cleaning, and public education -- at reducing trash and debris in transportation facility runoff?
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Study for Caltrans to evaluate whether catch-basin cleaning improves the water quality of highway stormwater runoff. The runoff water quality was monitored and analyzed to determine any difference in water quality between stormwater discharge from a drainage system with clean drain inlets versus discharge from unclean systems.
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. Despite these recommended design parameters, the relationship between BMP performance and hydraulic residence times, as well as other hydraulic characteristics of BMPs, is not understood clearly.
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Infiltration practices are one of the most valuable urban stormwater BMPs, because they help to reduce not only stormwater pollutants but also stormwater volume, which increases groundwater recharges and reduces the potential for scour and bank erosion in receiving waters. Livingston (2000)
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. The influence of hydraulic residence time on BMP performance has been studied well, and it has been confirmed that detention time is correlated positively with pollutant removal (at least for particulatebound pollutants)
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3.2.4.1. Identification of Research Needs When evaluating the performance of stormwater control facilities, it is important to consider not only the pollutant removal capacity under a variety of hydrological and influent quality conditions but also the pollutant retention capacity over long time periods and under both storm and low-flow conditions.
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Water quality monitoring results have indicated that average pollutant removal efficiencies are consistent with published values. The information collected on completion of the study will enable more accurate prediction of BMPs cost and performance for treating highway runoff.
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3.2.5.2. Coagulants Methods to improve pollutant removal in existing stormwater systems can be borrowed from technologies used at municipal treatment facilities.
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3.2.5.3. Identification of Research Needs The literature review addressing methods for improving pollutant removal in existing stormwater control facilities indicates a few potential research gaps.
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Nwankwo (2001) evaluated the effectiveness of PAMs at controlling erosion from three highway construction projects around Wisconsin.
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was affected by the erosion control treatment. The greatest water quality improvements were seen with the use of bound fiber matrix, jute, and straw.
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3.2.7. Design Variables Affecting BMP Performance The performance of stormwater control facilities is believed to be affected in large part by design variables such as geometry, surface area, outlet control structure, and vegetation density and type.
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3.2.7.1. Identification of Research Gaps and Needs Based on the review of literature, it is apparent that some of the primary design variables affecting BMP performance -- such as outlet structures, baffles, berms, and vegetation density, in addition to the volume a system is able to capture -- are those that control flow.
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Proc., 8th International Conference on Urban Storm Drainage, Vol. 2, Sydney, Australia (August 30–September 3, 1999)
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LID technologies are based on using the cumulative effects of multiple, redundant, decentralized stormwater management techniques to meet quantified stormwater management thresholds. LID is designed to create a multifunctional–multibeneficial use in every aspect of the urban landscape to manage runoff and, where possible, to restore or maintain effectively the natural hydrologic and water quality regimes.
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Numerous spreadsheet models have been created for water quality and hydraulic models and, more recently, for BMP modeling. Hayes et al.
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Using the model, the authors discovered that the cost for the maximum level of BMP treatment was four times as high as the cost for a 90% improvement in water quality using the four most economical BMPs. 84 Detention systems and infiltration systems appear to be the most extensively studied BMPs in terms of BMP modeling.
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However, other BMP water quality treatment unit processes -- such as sorption processes (absorption and adsorption) , biodegradation, photolysis, and volatilization -- still need to be studied further before reliable BMP performance models can be developed.
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A Conceptual Model for the Design and Simulation of Porous Pavements. Proc., 7th International Conference on Urban Storm Drainage (September 1996)
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With the exception of one infiltration trench in Nagoya, all of the infiltration facilities showed a marked improvement in infiltration capacity. A study of four porous pavement systems, including pavers with infiltration joints, porous concrete pavers with filter layers, greened porous pavers, and pavers with greened infiltration joints was performed to determine the pollutant retention abilities of the various systems (Dierkes et al., 2002)
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The results of the study suggested that infiltration basins, porous pavement, grass filters, swales, and "pocket" wetlands generally required modifications or improvements in order to provide reliable pollutant removal. A King County study evaluated the effects of mowing on the performance of vegetated swales (Colwell et al., 2000)
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The use of biological indicators for evaluating BMP performance is a relatively new method that is gaining popularity among stormwater regulators. Biological indicators such as those used in toxicity bioassays have been used extensively for evaluating potential impacts to and the contamination of receiving water systems (see EPA's Biological Indicators of Watershed Health: www.epa.gov/bioindicators)
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3.2.12.1. Identification of Research Needs Based on the scarcity of studies that use biological indicators for BMP performance assessment (as well as for general highway runoff characterization)
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(2002) , include • Quantification of the benefits of urban storm systems; • Consideration of receiving water impacts in cost–benefit analysis; • Development of cost–benefit evaluation methodologies for nonstructural BMPs; • The availability and application of flow and water quality data to BMP cost–benefit analyses; • Inclusion of land use data into cost optimization analyses; and • Cost–benefit analysis of BMP treatment trains.
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From page 92... ...
An evaluation of maintenance costs of BMPs -- such as wet ponds, dry ponds, exfiltration and infiltration trenches, porous pavement, baffle boxes, inlet baskets, and sediment sumps -- is presented by the authors, who recommended that maintenance needs be considered in the design and construction of retrofit projects in order to ensure that retrofits provide longterm pollutant removal. After evaluating baffle boxes and inlet devices, England (1998b)
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Costs of Best Management Practices and Associated Land for Urban Stormwater Control. Journal of Water Resources Planning and Management, Vol.
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Partnerships and negotiations among various jurisdictions and levels of government often are required to fulfill multifaceted social, economic, and environmental goals within the watershed. Only eight states have conducted studies or prepared reports on the retrofitting of existing stormwater management measures at DOT facilities where a watershed-based approach is employed to address fish passage or other issues pertaining to receiving waters.
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From page 95... ...
EEP is intended to protect the state's natural resources through the assessment, restoration, enhancement, and preservation of ecosystem functions and through identifying and implementing compensatory mitigation programmatically, at the watershed level. In particular, the program will – Enable multiple project impacts (wetlands, stream corridor, water quality, species, and habitat)
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The compensatory mitigation strategy will include a sufficient amount of restoration and enhancement to ensure no net loss of wetland and riparian acres and functions, including water quality effects. The project's preservation component is preserving the highest quality and most biologically diverse wetland and riparian sites throughout North Carolina.
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Little asset management information exists for BMPs. Pollutant trading is a fairly new watershed-based, marketdriven approach to improving receiving water quality while minimizing the costs associated with mitigation and restoration.
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3.4. HIGHWAY RUNOFF CHARACTERIZATION AND ASSESSMENT This category refers to the hydrologic and water quality characterization of highway runoff before entering water quality control facilities or receiving streams.
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3. Effect of Highway Runoff on Receiving Waters -- Completed in 1985, this five-volume report analyzes the effects of highway stormwater runoff on receiving waters.
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in crankcase oil and vehicle emissions are the major SVOCs detected in highway runoff and urban stormwater. The few loading factors and regression equations that were developed in the 1970s and 1980s have limited use in estimating current loads of SVOCs on a national scale.
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Polyaromatic Hydrocarbons. PAHs are a group of toxic and carcinogenic compounds rarely included in characterization studies, but often present in highway runoff due to trafficrelated sources.
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of petroleum hydrocarbons, including PAHs, as well as other trace elements not normally included in characterization studies, such as BTEX, MTBE, and PGMs. More advanced highway runoff characterization studies, such as those that investigate firstflush phenomena, the correlation of water quality parameters to independent variables, or the fate and transport of highway runoff pollutants, will be discussed in following subsections.
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The numbers of antecedent dry days was found not to be a satisfactory independent variable for constituent correlation. One of the most profound highway runoff correlation studies found in the literature review was conducted by Irish et al.
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In order to improve understanding of how much each impervious surface is contributing to the total imperviousness for each watershed, this research specifically examines the percentage of transportation infrastructure as well as the percentage of conTABLE 3-7 Identification of independent variables affecting constituent concentrations in highway runoff during multiple regression analysis (adapted from Thomson et al., 1997)
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The hydrological factors such as runoff volume, rainfall volume, intensity, and duration are independent variables that have been shown by a few researchers to affect runoff constituent levels. Total storm volume affects loads of some water quality parameters such as TSS and oil and grease but does not appear to significantly affect concentrations.
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Forecasting Pollutant Loads from Highway Runoff. In Transportation Research Record 1017, TRB, National Research Council, Washington, DC (1985)
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The study observed dry deposition fluxes of copper, nickel, cadmium, and chromium at concentrations of 1100, 600, 22, and 1300 µg/m2/year respectively and at concentrations of 1200, 420, 110, and 230 ng/L respectively in precipitation. Researchers concluded that atmospheric deposition contributed less than 30% of the loadings for copper and nickel in stormwater runoff.
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Filling this gap would provide a better basis to understand how highway-specific atmospheric deposition and dispersion of highway-related pollutants affect receiving water quality, receiving water biota, and roadside ecosystems. There is also a need to quantify the contribution of atmospheric deposition to pollutant concentrations found in highway runoff.
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materials on surface water runoff and groundwater quality. The study's main objective was to develop and evaluate methodologies for identification of possible surface and groundwater impacts from construction materials.
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This subsection touches on the surface of this vast topic with regard to highway runoff. The topic areas identified as the most important to highway characterization and assessment are sediment transport, speciation, and sorption processes.
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(1985) investigated heavy metal speciation in rainfall and highway runoff at two sites in central Florida: at the intersections of Maitland Interchange and I-4 and at US17-92 and Shingle Creek.
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It is well documented that the dissolved phase of the metals are more bioavailable and 112 therefore more toxic to aquatic biota than the particulate phase. In fact, in 1993 the EPA's Office of Water revised its policy to use dissolved metals concentrations rather than total recoverable metals concentrations to set and measure compliance with water quality standards.
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Influence of Chemistry, Hydrology and Suspended Solids on Partitioning of Heavy Metals to Particles -- Considerations for In-Situ Control of Urban Stormwater Quality. Global Solutions for Urban Drainage, Proc., 9th International Conference on Urban Drainage (September 8–13, 2002)
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From page 114... ...
However, the gross pollutant and litter mass loading rates were not highest during the first flush but generally appeared to correlate with the peak flow rate, which is similar to the water quality data. The total litter volume generated appeared to be related to the relative intensity of the storm event.
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A study to identify the variables that affect highway runoff in Austin, Texas, applied regression analysis techniques for predicting pollutant loads. The results of the study suggested that highway stormwater loading variations during a storm event depend on variables measured during previous events, the antecedent dry period, and the current storm event.
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The study also developed methods for estimating potential impacts on receiving waters, including guidance for evaluating the performance of mitigation measures. A total of 993 individual storm events at 31 highway sites in 11 states were monitored.
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Copper and zinc were shown to increase by 11% and 85%, respectively. Fifteen highway construction sites were monitored by Caltrans to assess the water quality of stormwater runoff from 117 the sites (Kayhanian et al., 2001)
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3.4.8.1. Identification of Research Gaps and Needs The disturbance of land during highway construction activities significantly increases the potential for sediment transport even with the implementation of erosion control prac
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3.4.9. Drain Inlet and Gross Pollutant Studies The control of gross pollutants in highway runoff was addressed in section 3.2.2., Gross Pollutant Removal.
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3.4.9.1. Identification of Research Gaps and Needs Because of the variety of materials that make up gross pollutants in highway runoff, characterization and assessment is difficult.
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3.4.10. Cold-Weather Studies Cold-weather highway runoff quality studies primarily characterize snowmelt runoff and evaluate winter maintenance activities such as highway sanding and deicing agent application.
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Review of Water Quality Impacts of Winter Operation of Urban Drainage. Water Quality Research Journal of Canada, Vol.
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. These projects integrated known technology applicable to the quality of runoff water, the background quality of the receiving water, and the water quality criteria applicable to the receiving water and addressed reasonable treatments and proper disposal systems if and when warranted.
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Although further research in these areas may be needed, the focus herein is on highway runoff, and the discussion has been limited to impacts caused directly by stormwater runoff or by runoff generated during maintenance activities such as bridge deck cleaning. Other bridge maintenance activities such as painting, surface treatments, substructure repair, joint repair, drainage structures repair, and pavement repair or repaving also may cause impacts to receiving waters depending on storm event timing, duration, and intensity.
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Heavy Metals and PAHs in Stormwater Runoff from the Skyway Bridge, Burlington, Ontario. Water Quality Research Journal of Canada, Vol.
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In addition to water toxicity testing, some researchers have evaluated the toxicity of sediments near urban stormwater outfalls to assess the effects of these discharges. Rochfort et al.
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This recent literature review effort supports the claim that there do not appear to be adequate bioassessment methods for assessing impacts of highway runoff on receiving water systems, particularly at the time-scales typical of stormwater-runoff events. Also, there are a wide variety of assessment methods currently used by the few highway water quality researchers conducting toxicity and bioassessment studies, so it is difficult to quantitatively compare existing data or to make any general assessment of the impacts of highway runoff on receiving water biota.
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3.5.5.1. Identification of Research Needs The area of water quality modeling shares a few of the research gaps identified under the BMP Modeling section (section 3.2.10)
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The water quality impacts of CSOs need to be better understood in order to facilitate development of appropriate regulations for the protection of receiving waters. According to Kaunelis and Johnson (2000)
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This sec130 tion evaluates the impacts of deicing agents on stormwater runoff. Potential research questions include • How do deicing agents impact receiving waters, and what are the least toxic alternatives?
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Five reaches along Peshastin Creek and its tributaries were selected for the collection of weekly grab samples and three of these reaches were outfitted with continuous monitoring equipment. Water quality tests, Microtox® toxicity tests, benthic macro invertebrate enumeration, and streambed substrate sieve analyses were used to evaluate the influence of deicing activities (application of traction sand and IceBAN, a liquid deicer)
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The results of this Florida DOT study showed an attenuation of inorganic contaminants; yet, the researchers concluded that organic compounds in the retention pond sediments may eventually impact groundwater quality.
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Pollution of Soil and Groundwater from Infiltration of Highly Contaminated Stormwater, A Case Study. Proc., 7th International Conference on Urban Storm Drainage (September 1996)
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Approximately 220 acres of wetlands are included in the project. An intricate train of treatment was included as part of the design to provide multiple benefits such as highway runoff water quality improvement, flood flow retention, and the creation of wildlife habitat.
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The tendency for many highway runoff pollutants to accumulate in wetland sediments and vegetation raises some concern with regard to long-term impacts on wetland biota. Current regulatory requirements for monitoring and assessing impacts to existing wetlands ensure that water quality and sediment quality, as well as toxicity data, are and will continue to become available for analysis.
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