International Low Impact Development Conference 2016: Mainstreaming Green Infrastructure

The Camden County Municipal Utilities Authority installed cisterns at locations around the city of Camden, NJ. Cisterns provide a cost effective approach to reduce stormwater runoff volume and peak discharge. The collected water can be substituted for potable water in some applications reducing the demand. This presentation focuses on five cisterns that were monitored as part of a capture-and-use system at community gardens. The cisterns capture water from existing rooftops or shade structures installed by CCMUA as part of the project. Cistern volumes varied from 305 gallons to 1,100 gallons. The design volume was based on the available roof drainage area. Water level was monitored at 10-minute intervals using pressure transducers and rainfall was recorded using tipping bucket rain gauges. Cisterns were sampled at 6 to 8 week intervals through the growing season for determination of concentration of microorganisms, nutrients, and metals. The analyses detected antimony, arsenic, barium, copper, lead, manganese, nickel, vanadium, and zinc. Concentration of all these metals were below recommended water quality criteria for irrigation by EPA guidelines for water reuse. The total nitrogen, phosphate, and total organic carbon concentrations varied from 0.23 to 2.26 mg/L, 0.025 to 1.11 mg/L, and 0.55 to 4.06 mg/L, respectively. Large total coliform concentrations were observed in some samples. The presentation will summarize the data for first growing season giving the results from monitoring the water use and water quality of cisterns.

Highways are major source of stormwater runoff due to their large foot print of paved areas. The runoff can lead to many environmental problems such as non-point source pollution, soil erosion, and flooding. The low impact development (LID) practice, through incorporating best management practice (BMP) elements in linear infrastructure projects such as highways, can provide a cost-effective and environmentally sound solution for on-site control and management of stormwater runoff. Because of the diversity and variety of site conditions across the country, an extensive number of factors have to be considered. For a given project, factors can include soil characteristics such as soil type and infiltration rate; site conditions such as surface vegetation cover, drainage area and pathway, slopes, imperviousness; meteorological conditions such as rainfall; available land space for BMPs, and costs associated with the installation and maintenance of BMPs. To develop a most cost-effective engineering solution for a given site, a large number of scenarios need to be analyzed to evaluate the impact of essential factors aforementioned on the performance of BMPs, which is to be linked to the cost analysis of a given scenario. For practical application, an approach that can be readily deployed for efficient evaluation of many scenarios in relatively short time is needed. Such an approach should be integrated with considerations for cost analysis. Information and reporting in the currently available LID design manuals and related technical documents about such an integrated approach linking extensive performance evaluation with cost analysis is limited. This paper discussed results from our study that takes a modeling approach to evaluate the impact of many aforementioned factors on performance of several BMPs for control of stormwater from highways, as well as the linkage with cost analysis. This study used an idealized catchment and Personal Computer Stormwater Management Model (PCSWMM) for analysis. The modeled BMPs included bioswale, infiltration trench and vegetated filter strip. The analysis results on newly constructed BMPs indicated an average runoff reduction of up to 100% from the infiltration trench, of 70-83% and 68-78% for bioswale and vegetated filter strip, respectively. The linkage between the performance and the costs of BMP installation and maintenance for linear projects were discussed. Findings from this study provides valuable information to support decision-making for selecting and placing cost-effective stormwater BMP for controlling stormwater runoff from highways and beyond.

“Green City, Clean Waters” is Philadelphia Water’s Wet Weather Long Term Control Plan that intends to reduce the stormwater entering the city’s combined sewer system through the use of green stormwater infrastructure. Since the adoption of “Green City, Clean Waters” in June 2011, the modeling efforts to represent, evaluate and guide the program have advanced. The growth of the program has led to an increase in data collection and general information about the collection system, which helps make the hydrologic and hydraulic (H&H) models better.

By 2030 the Republic of South Africa (RSA), a developing country, is predicted to be severely impacted by physical water scarcity. 2015 was one of the driest years on record, leaving many towns with extremely compromised water supply systems whilst also limiting food production across the country. This is placing pressure on the already fragile economy. In order to avert a future water crisis, the country needs to reduce its reliance on conventional surface water schemes based on impoundments on rivers. This paper presents an initial assessment of the potential role of low impact development (LID) for the purposes of stormwater harvesting (SWH) and describes the principal outcomes from two RSA case studies. The findings suggest that SWH could substantially increase the supply of water to urban areas, but that there are a number of barriers to its wider use that need to be addressed. The paper concludes with three “position statements” describing how SWH, with the assistance of LID, can contribute to: improving water security and increasing resilience to climate change in urban areas; preventing frequent flooding; and providing various other additional benefits such as amenity and the preservation of biodiversity.

The Toronto and Region Conservation Authority (TRCA), Lake Simcoe Region Conservation Authority (LSRCA), and Credit Valley Conservation Authority (CVC), “the GTA CAs,” have worked collaboratively to identify preferred low impact development (LID) stormwater management (SWM) models suitable for meeting typical design criteria. The GTA CAs research and experimentation efforts with various LID SWM case studies will inform the audience of model criteria and rationale that supports the selection of preferred open-source and/or commercial license LID modeling tool(s) which effectively demonstrate design targets have been met. The GTA CAs commissioned Golder Associates Ltd. to provide programming support and water resources expertise to support the development of the LID Treatment Train Tool (LID TTT) for Ontario, presently in a working beta version for review and experimentation before a planned hard launch in late March, 2017. The primary intention of the LID TTT is to support more consideration and realization of LID opportunities for a proposed site plan, throughout the design process undertaken by planners, SWM designers, and other decision makers for all types of site development or retrofit projects. The LID TTT will process computational results from EPA-SWMM to provide an assessment of stormwater runoff volume and associated target depths, along with total suspended solids (TSS) and total phosphorus (TP) reductions for both annual and event based scenarios, throughout the design process. A preliminary water budget assessment for pre and post conditions is also provided in the beta version of the LID TTT.

The performance variability of green infrastructure is connected to the changing dynamics in rainfall-runoff processes. Because of these dynamics, a green infrastructure facility experiences a range of rainfall-runoff events that are difficult to fully capture during a monitoring program. In this study, we evaluated the cumulative hydrologic performance of green infrastructure in a residential area of the city of Parma, Ohio, draining to a tributary of the Cuyahoga River. Green infrastructure involved the following spatially distributed devices: 16 street side bioretentions cells, 7 rain gardens, and 37 rain barrels. Data consisted of rainfall and outfall flow records for a wide range of storm events, including pre-treatment and treatment periods. The stormwater management model (SWMM) was calibrated and validated to predict the hydrologic response of green infrastructure. Optimized parameters were used to estimate flow attenuation over 11 years of precipitation data in order to capture the complex rainfall-runoff dynamics. For the long-term simulation of green infrastructure, we observed a 0.8% increase in evaporation, an 8.8% increase in infiltration, a 14.2% reduction in surface runoff, and 4.6% outflow from green infrastructure. The hydrologic performance of green infrastructure was evaluated by comparing the flow duration curve for pre-treatment and treatment outfall flow scenarios. The flow duration curve shifted downwards for the green infrastructure scenario, with a 21-26% decrease in the Q₉₉ and Q₉₈ percentiles. Parameter and predictive uncertainties were inspected by implementing a Bayesian statistical approach.

Civil engineering senior undergraduate students at Stevens Institute of Technology are required to evaluate engineering solutions to real world design problems while completing their capstone design. During the 2015-16 academic year, two design teams assessed incorporating green infrastructure (GI) technologies to capture stormwater within two very different regions. One team worked with the Task Force on Water Resources Management for the Rockland County Planning Department. The other team worked with the Stevens Division of Facilities and Campus Operations to assess GI’s benefits on a dense urban campus as part of the USEPA Campus RainWorks Challenge. Each team established design objectives based on community concerns and developed conceptual level designs through stakeholder engagement. The students learned how to use engineering tools to evaluate hydrologic response and convey their findings to the stakeholders. Educational value was added for the students, who were required to attend meetings with community stakeholders and educate the public and peers about the benefits of the proposed GI designs in “plain” language. This served as a unique learning experience as the students became the teachers. The stakeholders benefited by obtaining a detailed study on the impact of GI technologies at little to no cost.

The use of green infrastructure (GI) to mitigate the effects of increasing rate of urbanization has not been without challenges. Determining the clogging patterns and finding the issues with clogging will enable the researchers to address some of these challenges. Two GI stormwater control measures (SCMs) were constructed in Louisville, KY, utilizing permeable pavers in December 2011. Using empirical methods for maintenance, one paver strip has been maintained quarterly and the other only when requested. Using sweeper truck as the first method and air pressure tools as the second method, the clogging material was recovered and analyzed for particle size distribution and organic content. Characteristics of clogging material are used to provide refinement to the maintenance method, frequency for remedial methods. By dividing each SCM into equal small segments, the material collected using the air pressure maintenance provides a better description of the behavior of the SCM. With the more frequent maintenance, fines are mostly trapped up gradient and larger particles with majority of organics are trapped down gradient. The shorter SCM with more service time has shown that the penetration of fines is almost equal all segments. Finally, the quarterly maintenance plan is found more suitable than the other.

The City of San Diego, in developing water quality improvement plans for watersheds within the city, sought to assess the benefits to the citizens of San Diego of the anticipated investments in green storm water infrastructure and other activities they would undertake to reduce pollutant loads in urban runoff and storm water. The city and its stakeholders implemented initial stages of HDR’s sustainable return on investment (SROI) approach to identify and communicate the value of additional benefits that could be realized from several dozen strategies and project types. The initial stage of this analysis involved identifying benefit categories in terms of the triple bottom line: financial, environmental, and social outcomes. Then, each benefit category, respectively, was further defined by key drivers of value. Next, the degree to which each strategy and project type could actually generate each type of benefit was assessed. This process ultimately led to an initial ranking of project options in terms of potential relative value. Some of the categories of benefits associated with green storm water infrastructure investments and other actions included habitat improvements, increased local water supply, greenhouse gas emission reductions, improved public health, and improved recreational opportunities. The connection between a stormwater management strategy and benefit category was characterized, depending largely on available information, in one of four ways. Monetizable: stormwater management strategies that are likely to generate the highest value would have monetizable benefits. The value of specific strategies would be derived from available peer reviewed studies. Measurable: strategies that generate measurable, but not monetizable, benefits are likely to generate comparatively lesser degree of value than monetizable ones. In this case, engineering design and studies may be able to quantify tangible impacts, but economic literature has not been sufficiently developed to assess value for that scale or type of project outcome. Potential: this scale of benefits characterizes project outcomes that are less clear and more speculative. These benefits have no peer reviewed studies showing that they were observed from implementation of the strategy in a quantifiable manner, but judgment and accepted theory suggested the benefits would be likely to occur. Not-applicable: benefits that no peer reviewed studies showed occurring from implementation of the strategy, and judgment and accepted theory suggested would be unlikely to occur. At this initial stage of analysis, the value of each stormwater management strategy was characterized in terms of the number of benefits that could be generated by the strategy and the degree to which they could generate monetizable value.

As BMP sizing standards have evolved towards a focus on volume-based approaches (e.g., capture of the first 1 inch of runoff), sizing methods are typically absent or lacking for flow-based BMPs. Yet, flow-based BMPs that are certified with high pollutant removal performance can serve an important role in stormwater management in space constrained areas or as part of treatment trains in combination with volume-based systems. In response to these factors, Modular Wetland Systems, Inc. commissioned the development of a new sizing methodology for forty-five regions within fifteen states on the eastern seaboard of the United States for the flow-based MWS Linear treatment system. This methodology is based on providing equivalent long term capture efficiency of stormwater runoff volumes as compared to volume-based regulatory standards. The sizing methodology developed first involves establishing a target capture efficiency for each region, obtained directly from state guidance, or developed via continuous simulation modeling using long-term, high-resolution precipitation data. Facility flow rates needed to achieve the target long term capture efficiency for different drainage area conditions were then calculated via continuous simulation modeling. Findings were normalized and used to develop sizing tables to allow for application to flow-based facility sizing for user-specific drainage area types.

A multi-disciplinary team evaluated the potential real estate development and financial impacts of new post-construction stormwater standards, and an option for a fee-in-lieu for off-site compliance, on planned development in an area planned for transit-oriented development in Riverside County, California. Site plans, stormwater volumes, and development costs were projected for expected development in study area to determine the impact of stormwater compliance on total development cost. The study found the new standards could affect the financial feasibility of medium-density infill and redevelopment projects. However, a fee-in-lieu option for up to 30% of required volume, if priced at the equivalent cost per gallon treated of a standard stormwater management practice, would successfully address the financial feasibility impacts. The study provided much better understanding of the types and extent of developments that will likely need alternative compliance and the cost tolerances for a fee-in-lieu program.

Tetra Tech prepared a study for EPA (to be published by summer 2016) to explore methods for estimating the consumptive direct use value of groundwater recharge achieved through stormwater retention practices designed to simulate predevelopment hydrology. The study estimated the value that could be realized from expanding practices for maintaining recharge rates for new development and restoring recharge in redevelopment in those states where existing regulatory standards do not already meet or exceed the retention scenario evaluated. Across a number of scenarios studied, the estimated cumulative volumes of stormwater retention range from 6.8 million to 10.8 million acre-feet. The monetary values of this retained stormwater range from about $16 to $225 million, annualized, and $0.2 to $4.5 billion in cumulative, present value benefits. The full study, Estimating Monetized Benefits of Groundwater Recharge from Stormwater Retention Practices (2016), is available on EPA’s website.

Quality soil is critical to the performance of LID projects. Poor soil quality and project failures can result when soil specifications are not properly provided or are poorly written. Case studies of various New England projects completed in the past few years will be used to illustrate the successful use of non-proprietary manufactured soils to satisfy design criteria. Soil specifications and soil design will be presented for storm water treatment facilities, such as infiltration basins and rain gardens, where soils must provide for rapid and controlled infiltration rates while at the same time provide adequate water holding capacity and organic content to support vegetative growth. Design standards and construction of soils for wetland restoration projects will also be presented. Soil manufacturing principles and soil testing methods used to assess soil quality will be discussed in relation to satisfying design goals.

A green infrastructure treatment train at Villanova University consisting of a vegetated swale, two rain gardens in series, and an infiltration trench was analyzed as part of the study. The GI treatment train has shown adaptive capacity during seasonal variations and large storms resulting in greater volume capture than designed, however, performs inefficiently due to static design. As part of ongoing construction at Villanova University, a 5,100 gallon cistern was added as part of the GI treatment train system. The cistern has a pump that will allow stored runoff in the cistern to be recirculated through the GI treatment train to maximize infiltration during and after a rainfall event and increase the drainage area capture volume over the previous design. The GI treatment train is instrumented with flow meters, pressure transducers, and soil moisture meters throughout in attempt to optimize system performance. Real-time data from NOAA and sensors installed at the site are utilized by OptiRTC to have real-time control and operation to decide when runoff should be recirculated in the system and optimize system capacity. The addition of the cistern increases the static capacity of the system as well as the adaptive capacity due to the potential to detain or release stormwater runoff based on projected weather forecasts. The goal of this research is to optimize the infiltration performance at the treatment train through the use of a real-time control system. Volume capture will be studied and compared with previous research at the treatment train through the use of 22 sensors installed to monitor the system performance. Further, initial algorithms developed to assimilate data will be further developed to create self-learning algorithms based on the successes and failure of the system. An overview of the site setup is presented.

The benefits of green infrastructure to manage stormwater have been well documented and many communities have amended their ordinances to promote these practices. However in Indiana, we can do better. In 2014, the Indiana Office of Community and Rural Affairs (OCRA) sponsored the development of a curriculum and delivery of a training program to provide local governments and their project partners with information to implement stormwater projects which incorporate green infrastructure practices. Six one-day trainings were conducted throughout the state in 2015 and 2016 to educate and empower elected officials, decision-makers, and municipal staff to include green infrastructure into their municipal operations. The one-day trainings were strategically divided into three sessions to attract and meet the needs of the diverse interests in a municipality that influence the implementation of green infrastructure projects. These sessions include 1) an overview of green infrastructure, 2) policies, incentives, and funding, and 3) design and integration into municipal project. The target audience was elected officials, decision-makers, and municipal staff from engineering, planning, finance, economic development, parks, and street departments. Attendees were invited to attend the entire day or just the session that was most applicable to their municipal role. The information covered in the sessions ranged from a general overview of what green infrastructure is and the associated social, environmental, and economic benefits to examples of design, construction, and maintenance requirements and worksheets for green infrastructure practices. Case studies from across the state were used to illustrate how to successfully integrate green infrastructure into municipal programs, policies, and projects. While this presentation will focus on case studies in Indiana, the overview and approach for the trainings, the call to action worksheets, the feedback from attendees, the progress municipalities have made implementing green infrastructure policies and practices as a result of the training, and the lessons learned will benefit similar training programs nationwide.

The EPA’s Urban Watershed Management Branch (UWMB) has been monitoring the permeable pavement demonstration site at the Edison Environmental Center, NJ, since 2010. This site has three different types of permeable pavements including interlocking concrete permeable pavers, pervious concrete, and porous asphalt. The permeable pavements are limited to parking spaces, while adjacent driving lanes are impermeable and drain to the permeable surfaces. The parking lot is instrumented for continuous monitoring with thermistors and water content reflectometers that measure moisture as infiltrate passes through the storage gallery beneath the permeable pavements into the underlying native soil. Each permeable surface of the parking lot has four lined sections that capture infiltrate in tanks for water quality analyses; these tanks are capable of holding volumes up to 4.1 m³, which represents up to 38 mm (1.5 in.) for direct rainfall on the porous pavement and runoff from adjacent driving lanes that drain into the permeable surface. Previous technical releases concerning the demonstration site focused on monitoring techniques, observed chloride and nutrient concentrations, surface hydrology, and infiltration and evaporation rates. This presentation summarizes these past findings and addresses current water quality efforts including pH, solids analysis, total organic carbon, and chemical oxygen demand. Current findings support earlier findings for pH, total organic carbon, and chemical oxygen demand where porous asphalt infiltrate values exceeded the infiltrate values of the other two permeable pavements; interestingly, porous asphalt suspended solids concentration is increasing with time.

This paper summarizes research conducted to revise existing pavement thickness design tables for permeable interlocking concrete pavement (PICP) published by the Interlocking Concrete Pavement Institute (ICPI) in 2011. The study included a literature review, field deflection testing of existing projects and test sections, estimation of the effective stiffness of each layer in PICP structures, mechanistic analysis, and structural design of a test track incorporating three different subbase thicknesses (low, medium, and higher risk), tests on the track with a heavy vehicle simulator (HVS) to collect performance data to validate the design approach using accelerated loading, refinement, and calibration of the design procedure using the test track data, development of a spreadsheet based design tool, and development of revised design tables using the design tool. Rut development rate as a function of the shear stress to shear strength ratios at the top of the subbase and the top of the subgrade was used as the basis for the design approach. The revised design tables are based on subgrade soil properties, subbase aggregate properties, the number of 80 kN standard axle loads, and the number of days with standing water in the subbase. The minimum design thicknesses required to prevent subgrade rutting in the revised tables do not differ significantly from those in the 2011 ICPI publication and are mostly less conservative.

This study aimed at developing LID-based district planning techniques, and simulating effects of LID-based district planning. Analyses were progressed with the following order. First, establishing process and principles of LID-based district planning were set up through analyses on related literature, and LID-based district planning technique (proposal) was deduced. Second, FGI was executed to develop the technique. To secure its objectivity, FGI (focus group interview) was progressed three times. Third, LID-based district planning was established by selecting the object place, and LID effects were simulated. Simulation was made by using multilateral impact assessment tool. Research results are as follows. First, LID-based district planning technique was developed. Principles were derived from “Preventing flood damage,” “Securing good environment,” and “Minimizing developmental impact area.” Establishing procedures were composed of steps like basic survey, comprehensive analyses, basic design, plans by section, and each step had detailed phases. Second, a fact was verified that LID-based district planning technique reduced non-point pollution source and rainfall runoff and had sufficient ability in achieving environmental performances which enhanced ecosystem through a simulation on LID-based district planning effects. This means that planning is possible systematically according to targets of considering ecologic aspects. Third, LID-based district planning can be evaluated as a comprehensive plan which achieves environmental performances and ensures development of areas as well.

Philadelphia Water’s Green City, Clean Waters program outlines a vision for large-scale implementation of green stormwater infrastructure (GSI) to reduce stormwater-based demand on the combined sewer system. Stormwater tree trenches are an essential stormwater control measure (SCM) of the Green City, Clean Waters program. In order to effectively assess the performance of stormwater tree trenches, collaborators at Drexel University and Philadelphia Water developed a green infrastructure performance (GIP) model that predicts infiltration rates and estimates water levels within the SCM. Quantitative experimental data are evaluated in order to demonstrate GIP’s applicability to a variety of SCMs. 13 SCMs currently monitored by Philadelphia Water are assessed as case studies. Quantitative performance evaluation via simulated runoff tests (SRTs) is discussed. SRT application allows for testing of SCMs in a controlled manner. SRT procedures developed by Philadelphia Water staff are discussed in detail. These procedures introduce metered flow to the SCM via a fire hydrant connection. Quantitative data regarding inflow and water level in the SCM and qualitative observations are collected. These inputs, and precipitation data from natural events, are used to calibrate the GIP model. Analysis protocols and real world applicability are discussed through these case studies. The GIP model uses R and related technologies to execute model routines. R is used to perform quality assurance and quality control of large amounts of data collected in SRT activities. When data analysis and model runs are complete SRT data is used to validate and calibrate additional analysis routines.

To investigate the possibility of reducing winter road salting using permeable pavement, the University of Toronto, partnering with the Ontario Ministry of Transportation and the City of St. Catharines, is currently conducting a winter performance assessment study of a heavily used permeable pavement parking lot located in St. Catharines, Ontario. The purpose of this two-year study is to evaluate the winter pavement performance and verify the safety and environmental benefits of permeable pavements by comparing them to a conventional asphalt pavement. Throughout the 2015/2016 winter, skid resistance measurements were collected following winter maintenance to identify the risk of slips and falls on permeable pavements. Conductivity levels in winter outflows have been continuously monitored in order to examine the environmental impacts of the permeable pavement on winter stormwater quality.