Linking Stormwater BMP Designs and Performance to Receiving Water Impact Mitigation

This paper summarizes and synthesizes, from the authors' perspective, the key themes and observations that emerged during the August 19–24, 2001 conference held in Snowmass, Colorado entitled: Linking Stormwater BMP Designs and Performance to Receiving Water Impact Mitigation. The objective of the conference was to discuss and debate what we know and do not know about the linkages between BMP designs and their performance and their ability to mitigate receiving water impacts of urbanization.

Described here are threats and opportunities facing the urban water field. Awareness of and action on these is in the best interests of water professionals, employers, professions and society. The paper urges more diligence in applying the state-of-the-art, guarding against software misuse, adopting a holistic approach to watershed development, and rejecting price-based selection when clients need consulting services.

The U.S. Environmental Protection Agency implements many of the nation's laws for protection of public health and the environment. Recently, EPA has focused on improving the management of urban wet weather flows under the NPDES program. Among the methods for improving urban wet weather flows, watershed management, best management practices, innovative funding mechanisms, and locally developed total maximum daily loads are of particular interest.

Urban watershed needs for many river basins include water conservation, reclaimed water, replacement of pipes, slope stability, land use planning, flood control, coastal protection, desalinization, evaporation suppression on reservoirs, dam safety, aquifer storage and recovery, and atmospheric water management. Predictions of national migration and resettlement, seismic performance or urban regions, scientific developments in water purification, rearrangement of state and provincial boundaries, further research in vegetation management, and a total water resources cost recovery system are just a few items that can be further developed in the 21^st Century. The American Society of Civil Engineers (ASCE) encourages broader participation by its Institutes and the other technical councils in the development of codes and standards, conferences, and appropriate continuing education opportunities. This President of the Environmental & Water Resources Institute (EWRI) of ASCE recommends the continuing development of a private sector-govemment-academia partnership, including financial support by all sectors, in order for professionals to participate fully in the development of standards that will benefit partnerships for the entire world. ASCE continuing education courses for the professional in 2001 may include: (1) Urban Watershed BMP's, (2) Municipal Storm Water Management, (3) Applications in Stormwater Management, (4) Hydrologic & Hydraulic Design of Culverts, (5) Modernization of Irrigation Water Delivery Systems, (6) Wind Loads for Buildings, and (7) Wetlands and 404 Permitting. Past self-study products of the AWWA, WEF, NGWA, AGU, AWRA, University of Wisconsin — Madison, Clemson University, and ASCE have included wetlands & 404 permitting, forecasting urban water demands, planning & management of reliable urban water systems, design & installation of buried pipes, slope stability & landslides, multi-layered aquifer systems, sewer pipeline rehabilitation, trenchless technology, and soil erosion & sediment control. Many of the predictions and educational products are related to the expected development and background education of the recognized technologists associated with the work by many professionals that serve as volunteers of technical societies. The future knowledge needed for urban watersheds include a combination of technologies, additional codes and standards, and continuing education opportunities. This presentation will provide one perspective of a few of the urban watershed technologies that could be covered by future EWRI/ASCE product and marketing opportunities.

Cities, counties, and regulators in the northwest and other regions of North America are looking to maintain stream integrity, and thus, habitat integrity, through the use of on-site control measures. These measures include forest retention, limitations on impermeable surfaces, and controlling the time-duration of runoff rates for what are perceived as critical storm return frequencies. Administratively, uniform criteria should be applied throughout a jurisdiction, or at least throughout a watershed. The question then becomes, is it financially and/or politically feasible to impose the most critical limitations needed to preserve the most vulnerable habitat, and, if not, what habitat conditions can be sacrificed? The effectiveness of on-site control measures for preserving stream integrity will vary with watershed geology, geomorphology, climate, microclimates, vegetation, location in the watershed, and a whole host of other variables. Even within the same region, watershed properties can be very inconsistent. It is understandably difficult to define what critical conditions to protect, even if protection can be provided. The listing of species under the Endangered Species Act (ESA) may severely constrain urban growth in the northwest United States. The purpose of this paper is to examine the potential for on-site-control measures as proposed for the northwest United States to preserve stream channel integrity and habitat. If effective, these proposed measures could overcome some ESA limitations and allow development in undeveloped areas.

Stream ecosystems in three different locations in the United States were found to benefit in a similar fashion from retention of watershed forest and wetland cover and wide, continuous riparian buffers with mature, native vegetation. The findings can help guide comprehensive watershed management and application of these non- structural practices in low-impact urban design. Intensive study of structural best management practices (BMPs) in one location found that, even with a relatively high level of attention, a minority of the developed area is served by these BMPs. Those BMPs installed are capable of mitigating an even smaller share of urban impacts, primarily because of inadequacies in design standards. Even with these shortcomings, though, results showed that structural BMPs help to sustain aquatic biological communities, especially at moderately high urbanization levels, where space limits non-structural options.

Monitoring of both land treatment and water quality is the best way to document the effectiveness of nonpoint source pollution control efforts. There has been a dramatic expansion of nonpoint source control projects with the establishment of the Section 319 Program. However, the lack of information and data hindered State and Local efforts to address nonpoint source pollution. A national framework was needed to address this issue. Working with States and recognized experts, the United States Environmental Protection Agency created the National Nonpoint Source Monitoring Program (NMP). The purposes of the National Nonpoint Source Monitoring Program are to provide credible documentation of the feasibility of controlling nonpoint sources, and to improve the technical understanding of nonpoint source pollution and the effectiveness of nonpoint source control technologies and approaches. These objectives are to be achieved through intensive monitoring and evaluation of a subset of watershed projects funded by a combination of Section 319 funding and other sources. Presently, there are 23 projects within the program — mostly agriculture with two urban projects. Typically, the projects are 6–10 years in nature and consist of three distinct monitoring periods; a pre-implementation baseline (2 years); BMP implementation (2 – 3 years), and post implementation evaluation (3 – 5 years). An overview of the program is presented. Lessons learned and successes from selected NMP projects are highlighted. Also, detailed information regarding how the NMP projects have provided support for the development of urban runoff programs is presented. Recommendations are given for successful watershed projects that can document BMP effectiveness through water quality and land use monitoring.

The U.S. Environmental Protection Agency is developing effluent guidelines applicable to discharges of storm water from new construction and land development activities. This paper presents EPA's assessment methodology for measuring the potential benefits of these guidelines, which include reductions in (1) pollutant loadings to surface waters; (2) habitat/biological impacts (e.g., destruction of streamside habitat, increased stream channel erosion, impacts on cold water fisheries); and (3) impacts on floodplain size.

The Rouge River National Wet Weather Demonstration Project in Wayne County, Michigan, has developed an approach to linking the performance of best management practices (BMPs) to receiving water impacts. The approach considers the various stages of the "life cycle" of BMP design and implementation, and it includes a system of performance measurements at each stage.

Rural to urban land use change is a ubiquitous and formidable challenge in watershed management. Decades of research have revealed that urbanization frequently results in severe stream degradation, but the complexity and variability of stream responses inhibit prediction and informed decision-making. Associations between gross measures of total imperviousness or human population and stream characteristics provide little meaningful feedback for understanding key processes and creating practical mitigation strategies. In contrast, examining the effectiveness of mitigation strategies relative to fundamental biophysical linkages provides a foundation for improved management of aquatic ecosystems in rapidly changing watersheds. The objective of this paper is to provide a process-oriented view of what is known about the physical response of streams to urbanization and stormwater controls, to identify some critical information gaps, and to suggest useful approaches and analysis tools for filling these gaps. In particular, variable responses to altered flow and sediment regimes across different stream types, riparian conditions, and spatio-temporal scales are considered. Decision-based models of channel instability that account for the relative sensitivity of stream types to changes in flow and sediment regimes can improve our ability to set priorities and tailor mitigation strategies to the response potential of receiving waterbodies.

The question "What do we know about impacts of urbanization on receiving water?" can be easily answered. We know a lot, and we know almost nothing. The dual response is due to the fact that we have an abundance of studies that show change, but few studies that confirm cause and effect relationships between water quality and receiving system response. The identification of the relationships between water quality and the response of biological communities can begin with an assessment of potential toxicity associated with runoff events. Since toxicity is produced by a contaminant concentration and associated duration of exposure, assessing the toxicity of runoff should be straightforward. Unfortunately, there has been very little research supporting exposure regimes that are appropriate to storm events where peak concentrations of contaminants may last for only a few seconds. Further, toxicity is also associated with the frequency of exposure to a given concentration/duration of exposure couple. More frequent exposure events, at lower concentration may have more effect than less frequent exposure events at higher concentrations. What emerges from a careful review of this time-scale of exposure research on environmental toxicity research is that storm-related toxicity is not easily characterized. In short, we have lots of toxicity data, but little toxicity information to better understand urbanization effects on receiving systems. In addition to direct toxicity, bioassessments indicate that urbanization affects the integrity of receiving streams. Studies over the past twenty years have found aquatic communities indicative of degraded conditions in urban environments. Unfortunately, these studies fail to provide a specific community response that is specifically responsive to urban runoff. Again, we have lots of data, but information on the specific effects of urbanization is inconsistent. The following discussions will address the question of "What do we know?" by focusing more on what we should know! The following discussions will review a time-scale approach to information gathering that will provide a solid foundation for urban runoff effect analysis

The objective of the Clean Water Act (CWA) is to maintain and restore the chemical, physical and biological integrity (ecological integrity) of the Nation's waters. However, in populated urban watersheds with large amounts of imperviousness, loss of riparian cover, extensive habitat modifications, altered hydrology and numerous pollutant and runoff sources, achieving the highest level of ecological integrity may no longer be feasible — attempting to do so may set unrealistic goals and be economically unachievable. Under the CWA and federal regulations, States, territories and Tribal Nations have the capability to set realistic goals for managing urban water bodies. These goals are the State and Tribal water quality standards and should be the primary yardstick by which water quality management, including storm water management is measured. Through the public water quality standards-setting process, States, territories and Tribes can make improvements in managing aquatic life by adopting more appropriate aquatic life uses for urban water bodies and setting different levels of criteria for protecting each use. Key tools in this effort are biological assessments and criteria. This paper discusses the statutory background and essential elements of water quality standards and how biological assessments and criteria can be used to define appropriate aquatic life goals for urban water bodies and better focus scarce resources on restoration efforts that are attainable.

The evolution of the stormwater regulations has moved substantially faster than has the science and economics needed to effectively direct the stormwater regulatory initiative. The imposition of zero discharge mandates, both as to stormwater-borne pollutants and stormwater itself, is now the reality facing stormwater managers. While the inventory of stormwater quality management practices that can predictably reduce pollutant discharges is growing, to the extent they don't achieve the zero discharge mandate, they do not reduce vulnerability to statutory enforcement action.

This paper explores the degree to which current stormwater treatment practices (STPs) can achieve low impact at the scale of the development site and the small watershed. Low impact is defined here as pollutant loading equivalent to that expected from a rural baseline load. The ability of current STPs to meet this criterion was determined in a four step process. First, uncontrolled pollutant loadings were estimated for a range of urban land uses, using the Simple Method and recently derived land use/impervious cover relationships. Load estimates are provided for sediment, phosphorus, nitrogen and fecal coliform bacteria. Second, ideal pollutant removal rates and effluent concentrations were derived using a national STP database. Third, these, ideal pollutant removal rates were adjusted to reflect stormwater implementation factors, such as stormwater bypass, exempt sites, and practice aging. Lastly, potential load reductions associated with better site design techniques were evaluated over a range of suburban land uses. Based on our analysis, we define the upper limits of pollutant removal for current STPs. Loads from suburban development with STPs alone consistently exceeded baseline rural loads for nitrogen, phosphorus and fecal coliform bacteria. The increased pollutant discharge over such a wide suburban land uses suggests that current STPs cannot consistently meet a zero or low impact threshold for moderately developed sites. At the watershed scale, it appears that background loads would be even more difficult to replicate. In fact, the majority total suspended solids loadings, which appear to most closely replicate natural background loads, are carried in channel erosion, which is not accounted for in this analysis. The implications of this finding for watershed managers, regulators and land use planners are also discussed.

Low Impact Development (LID) stormwater management strategies are an important tool in reducing stormwater impacts. The design and application of these strategies are an attempt to reduce the changes in hydrology that occur with development by reducing the peak rate and volume of stormwater runoff, along with providing water quality treatment through settling, filtration, and adsorption. There has been much discussion and emphasis placed on asserting that these methods can result in developments that mimic to a very close degree the natural runoff or hydrology from a site and hence result in "low impact". This paper reviews the inadequacy of the hydrological design procedures utilized to substantiate the effectiveness of the techniques and recommends that much more robust hydrological techniques be utilized to quantify the potential benefits of this development stormwater management approach. It also suggests that the name of the technique be changed to reflect the actual results of applications of the techniques more closely.

The City of Malmö in Sweden has used BMP more systematically since the late 1980's. Today the implementation of BMP is an integral part of the city's planning of new developments. As a base for this planning, all technical departments in the city have jointly developed a policy for a sustainable drainage of urban stormwater, which has been approved by the politicians. In 1999 a new concept for upgrading overloaded combined sewer systems based on BMP was introduced in Malmö. This concept was applied in the existing development of Augustenborg, which was built up in the late 1940's and early 1950's. The basic idea with the project was to disconnect the stormwater from the combined sewer system and divert it to a new open drainage system for stormwater. The open drainage system is formed by a combination of different BMP techniques. The inhabitants in the Augustenborg area have played a very active role in the planning and the design of the new system. Today all new developments in Malmö are planned with special consideration of the drainage of stormwater. Wherever possible new developments are built up along constructed open drainage corridors, which are laid out at a very early stage in the planning process.

Urbanization in the Denver metropolitan area has brought about changes in the hydrologic regime by increasing frequency of runoff; increasing peak discharges; increasing volume of runoff; decreasing time to peak and increasing duration of flow. This, when combined with the steep slopes prevalent in Eastern Colorado, results in severe erosion, degradation, widening and lateral migration of these channels. This paper will present a variety of solutions successfully implemented in the Denver metropolitan area to stabilize urbanizing streams and to reclaim degraded ones.

Urban stormwater controls for peak flow attenuation are currently being used throughout the world. Standard practice typically dictates bringing postdevelopment peak flows down to the predevelopment levels. In most cases the flow controls target low frequency events, while the smaller, higher frequency events are not affected. This study examines the effects of the state-of-practice in flow control on the peak flow frequency curve, and how well the postdevelopment flows are controlled to predevelopment levels. Continuous simulation, using 50 years of hourly rainfall record, was performed on two climactically diverse locales. Detention ponds with a variety of flow control orifices were examined singularly and in conjunction with extended detention best management practices (BMPs). Conclusions are drawn regarding the efficiency of current practice, and recommendations are made regarding the future of urban stormwater control.

A literature review of urban stormwater runoff and building/construction materials has shown that many materials such as galvanized metal, concrete, asphalt, and wood products, have the potential to release pollutants into urban stormwater runoff, and snowmelt. However, much of this previous research cannot be directly applied to estimating pollutant loadings from runoff. One limitation is that the studies were not performed using actual stormwater runoff. A second limitation is that they did not mimic the cyclic wet-dry weathering to which these materials are exposed. The weathering phenomena, which may result in the weakening of the strength of the materials, may significantly impact the release of these pollutants. This paper will discuss an ongoing research project that is investigating the pollutant releases from typical materials used for infrastructure construction.

Assessment of the effectiveness of any environmental management activity is dependent on stated (or implied) goals. Use of biological indicators to evaluate the success of stressor-control features in enhancing or protecting overall stream or watershed condition requires that some numeric decision threshold be developed. The indicators are, thus, interpreted with some understanding of their expected status in the absence of Stressors. The stated goal(s) of stormwater (SW) management/best management practices (BMPs) such as detention/retention ponds, riparian revegetation, bank stabilization, grade control structures, or others, is the removal or buffering of Stressors that cause receiving streams to be ecologically impaired. This paper presents findings from two case studies where a "BMP-assemblage" was evaluated without the benefit of calibrated biological reference conditions, and another where SW retention ponds, in isolation, were evaluated with calibrated reference conditions.

The Santa Clara Valley Urban Runoff Pollution Prevention Program (SCVURPPP) conducted a Stormwater Environmental Indicators Demon-stration Project (SEIDP) in the Santa Clara Basin, California. The project consisted of implementing and testing the applicability of 20 of the Center for Watershed Protection's 26 Environmental Indicators to Assess Stormwater Programs and Practices. The indicators were applied at two geographic scales: a 310-square-mile watershed and a 28-acre industrial catchment. Two groups of useful indicators were identified. The first group, which included the programmatic indicators targeted at measuring specific program activities, was useful for documenting and understanding pollution-prevention efforts and yielded insight into ways to improve them. The second group of indicators included the application of physical, hydrological, water-quality, and biological measurements at a watershed scale. These indicators were useful for an overall assessment of stream function and an understanding of the multitude of natural and anthropogenic factors that influence stream function. Results from implementing programmatic indicators stimulated improvements to the SCVURPPP's tracking and reporting of illegal discharges and industrial inspections. Results of physical, hydrological, water-quality, and biological indicators are being used to inform and motivate action among stakeholders in the Santa Clara Basin Watershed Management Initiative, a local effort to develop and implement a Watershed Management Plan for the Basin.

During the past decade, it has become apparent during numerous receiving water assessment studies that no one single approach (e.g., chemical-specific criteria, benthic microorganisms, or habitat surveys) can routinely be used to accurately determine or predict ecosystem health and beneficial use impairment. Each assessment approach or component has associated strengths and weaknesses. The selection of specific assessment tools and goals is highly dependent on local conditions and objectives. This paper, based on a recently published book and EPA report, outlines the major components of a receiving water assessment to evaluate urban wet-weather problems.

Following a brief summary of main European regulations dealing with stormwater, the current French and other West European approaches to innovative stormwater management are presented, with respect to BMP analysis, design and performance. This information is based largely on reviews of the European technical literature and the proceedings of the 2001 Novatech conference on innovative technologies in urban storm drainage, which contain a wealth of information on the use of BMPs in France and several other West European countries.

Best Management Practices (BMPs) for control of stormwater runoff include structural elements (structural BMPs) that can be applied on the local scale (e.g. infiltration), the drainage catchment scale (e.g. ponds and treatment, or wetlands) and the receiving water scale (e.g. retrofitting of river reaches), and non-structural BMPs, such as controls of chemicals or building materials, and street sweeping. The available knowledge of stormwater BMPs performance in pollution control is inconsistent and the effect of various BMPs on receiving water quality is either poorly understood, or not known. A review of recent experiences with selected stormwater BMPs in Denmark and Sweden is presented and discussed with respect to the current issues related to legislation and the forces driving future development in stormwater management.

There has been rapid growth in application of BMPs across Australian urban areas. Catchment management plan development frameworks have been established to guide the selection of appropriate management measures. In addition, there have been substantial advances in our understanding of pollutant pathways & intervention & transformation processes underpinning the development of management strategies. This review indicates that while substantial advances have occurred, there remain a number of significant shortcomings in the selection & application of BMPs.

It is essential that good research and programme assessment underpin policy development and programme implementation. The effectiveness of our efforts must be continually evaluated to gauge whether our activities provide a level of protection that the public expects and is consistent with a long term, integrated, and sustainable resource management strategy.

This paper summarizes findings on the impact of urbanization on streams, as it relates to upstream best management practices. First, streams are defined. Next, recent efforts to quantify the impacts of urban runoff are described. Lastly, the results of previous research needs are summarized, and research needs are presented.

Laws and policies dealing with environmental degradation, creation and disposal of waste products, or consumption of natural resources arising from human activities may be considered zero-impact policies when specific effects or waste products are banned outright or limited to detectable minimums. While zero-impact processes are in the strictest sense precluded by the second law of thermodynamics (entropy), the aggregate benefits of the intra- and intergenerational transfer of environmental effects necessitated by zero-impact policies may conceptually be assessed using a progression of sustainability-based social welfare criteria: efficiency, survivability, and sustainability. The core concern prompting implementation of de-minims impact policies relates to the precautionary principle of modern ecological economics, ordaining that precautionary measures be taken when the potential consequences of an activity are catastrophic (i.e. may threaten human health or cause irreversible harm to the environment), even if a direct causal relationship is not scientifically established. An integrated framework for formulating and evaluating zero-impact policies is proposed, incorporating sustainability, precautionary, and adaptive management concepts as a guide to formulating and evaluating these policies.

The understanding of the effects of urban stormwater best management practices (BMPs) in protecting, preserving, and/or improving the health of receiving waters is poor at best. BMP performance in terms of pollution and flow control is not well understood by itself, although through recent efforts this understanding is improving. The purpose of this paper is to provide a framework to begin discussions regarding potential approaches and methods for assessing the performance of urban stormwater BMPs in improving the health of aquatic ecosystems. The paper presents potential methods and study approaches along with potential individual physical, chemical, biological, and biochemical measurements/indicators that employed in particular combinations may be useful in assessing downstream BMPs performance. The paper also presents a brief overview of some of the challenges that will be difficult to overcome.

The U.S. Environmental Protection Agency is developing effluent guidelines applicable to discharges of stormwater from new construction and land development activities. As part of the effluent guidelines development process, EPA conducted two interrelated assessments. First it conducted an evaluation of the environmental impacts attributable to the land development industry. Second it conducted a related assessment of the effectiveness of erosion and sediment controls, post construction stormwater BMPs and low-impact development practices to determine the ability of these practices to mitigate impacts attributable to construction and development activities which were identified in the first assessment. This poster session describes the protocols that were used to conduct the assessment of the effectiveness of the post construction BMP's and summarizes the preliminary findings of the assessment. The effectiveness assessment was conducted for two broad categories.

Low Impact Development (LID) is an innovative technology to control stormwater quantity / quality impacts at the source using micro-scale management practices distributed and integrated throughout the landscape. This technology, developed by Prince George's County, Maryland, to address perceived problems in conventional approaches to stormwater management (SWM) within the County and the State, makes multifunctional use of the urban landscape allowing one to design a hydrologically functional site. This approach results in an ecologically based approach to stormwater management that is usually more aesthetically pleasing, precludes impacts to receiving waters, and is generally less costly to construct and maintain than conventional end of pipe systems This poster session provides a chronological overview of a number of projects which have been instrumental in the development of LID technology. The focus of the paper is on case studies and demonstration projects. While the emphasis of these projects is the state of Maryland, projects and case studies from other regions of the Country are also included.

Stormwater filters are typically operated in a downflow mode. This research had two objectives: (1) to determine the increased life of a filter operated in an upflow mode, and (2) to determine if the operation of a downflow, mixed-media filter could be modeled using the power equation proposed by Urbonas. The results showed that upflow operation could provide longer filter run times. Using laboratory-scale columns, the use of a power equation to model downflow filtration was also demonstrated. Model confirmation using pilot-scale columns is currently underway.

This paper presents the results of experiments conducted to determine if four potential filter media (sand, activated carbon, peat moss, and compost) could retain previously-trapped pollutants even under anaerobic conditions. The results indicated that permanent retention of heavy metals may occur even in an anaerobic environment. However, retention of nutrients may not occur under these conditions.

The poster presents a synopsis of the results of an industry profile data collection effort organized in a manner that facilitates evaluation of existing regulatory approaches based on classifying the requirements for erosion and sediment controls and for post-construction storm water management into one or more control strategies or levels.

Data from this study demonstrates that cattail callus cells can be used to predict the phosphorus concentration in cattail leaves when they are supplied with similar phosphorus levels. If this relationship between callus cells and whole plants is found applicable to other marsh plant species, callus cells could be used as a rapid means to screen plants for their capacity to absorb phosphorus.

This paper overviews causes of combined-sewer deterioration and their heavy pollutant discharges caused by rain events together with a discussion of their control methods. In particular, it covers in-sewer and combined-sewer overflow (CSO) storage-tank-flushing systems for removing sediments and minimizing hydrogen sulfide production, resulting in the reduction of associated pollution and sewerline corrosion, respectively. Performance of two technologies, i.e., the tipping flusher, (TF) and the flushing gate (FG) were evaluated by a detailed examination of 18 facilities in Germany, Canada, and the United States. Results indicate that both the TF and FG technology appear to be a cost-effective means for flushing solids and debris from CSO storage tanks, while the FG is considered to be the most efficient method for controlling combined-sewer sediment.

Burnsville, Minnesota used a group of citizens, business owners and city staff to select low-impact approaches for redeveloping a 40-acre site called Heart of the City (HOC). Site imperviousness will rise from 70.5% to 92.5%. A Low-Impact Development (LID) manual was created based upon XP-SWMM2000 goals, BMPs and existing permeable soils.

A summary of monitoring results is presented which provides hard knowledge on the effectiveness of BMPs in mitigating the effects of urbanisation on receiving watercourses. A porous paved car park and two swales in the East of Scotland were monitored, along with the associated road runoff. The results show these BMPs performed favourably when compared to the traditional drainage option.

Extant data were used to assess the relative effectiveness of ponds vs. wetland-type BMPs. Compared to wet ponds, wetlands tended toward higher constituent concentrations in effluent, were inefficient at nitrogen removal, and appeared to preferentially retain phosphorus. These differences were hypothetically evaluated in terms of emergent macrophyte growth dynamics.

The MCTT was developed to control toxicants in stormwater from critical source areas. During monitoring, the pilot-scale MCTT provided median reductions of >90% for toxicity, lead, zinc, and most organic toxicants. Suspended solids was reduced by 83% and COD was reduced by 60%. The full-scale tests substantiated these excellent reductions.

Previous research has identified significant reductions in infiltration rates in disturbed urban soils. More than 150 prior tests were conducted in predominately sandy and clayey urban soils in the Birmingham and Mobile, Alabama, areas. Infiltration in clayey soils was found to be affected by an interaction of soil moisture and compaction, while infiltration in sandy soils was affected by soil compaction alone. The tests reported here were conducted under more controlled laboratory conditions and represent a wider range of soil textures and specific soil density values.

Cost data and methods are presented to support the development of an Internet-based, interactive tool for estimating capital and operation and maintenance (O&M) costs of commonly used urban runoff best management practices (BMPs).

Stormwater sampling for colloidal and dissolved metals and organic carbon has been initiated at six outfalls draining locally-designated, nonindustrial land uses in Monmouth County, New Jersey. Of the heavy metals, only Cu and Zn were found in all samples, mostly in dissolved form. Larger colloids (>0.45 μm) were composed mostly of Fe, Al, and Si. Organic colloids were found mostly in the 0.01–0.45 μm size range.

The objective of this study was to evaluate the feasibility of using low-cost, natural filter materials for stormwater (SW) treatment. Generic mulch, pine bark mulch, and processed jute were evaluated for metal and organic pollutant removal from actual SW samples collected from a "hot-spot" site (commercial parking lot) in New Jersey. The retention and release behavior of pollutants in different filter materials was evaluated using a specially constructed bench-scale filtration apparatus which allowed for the simultaneous testing of up to 10 different media conditions. SW flowrates (fluxes) through the individual columns and the sorption capacity of each filter medium were studied under a variety of conditions. The benefits of combining mulch or jute with sand (in ratios of 0.25, 0.50, and 0.75) to improve the hydraulic properties (filter flux), removal ability, and cumulative capacity of the filter for a specific pollutant were evaluated. Initial tests were performed to evaluate the basic performance of the mulch and jute materials ("as received"). This performance was compared with the performance of the materials whose particle size was altered. This alteration of the particle size within the filter material was done by separating the mulch materials into "coarse" and "fine" fractions and cutting the jute fiber into significantly smaller pieces. The effectiveness of the filtration process was found to be dependent upon the physical characteristics of the filter media. Both the sand content and particle size of the filter media affected flowrates of SW and their pollutant removal capacities. Copper (Cu) and benzo(a) pyrene [B(a)P] were used a surrogates for heavy metals and organics, respectively. Removals as high as 100% of Cu were observed for all of the combinations of sand with mulch or jute. The removal of B(a)P was found to be dependent upon the media-to-sand ratios, and ranged from 68 to 94%. No significant amount of either pollutant was released from any of the media when the columns were flushed with distilled water. Both mulch and jute appear to be suitable filter materials for Cu and B(a)P removal from urban SW runoff. Additional investigations, however, are necessary to evaluate the practicality of field applications of mulch or jute in the treatment of SW runoff.