Catherine Barr, December 2nd, 11:30 AM, CEER 312
Water quality performance of a green roof in comparison to other land uses
Recent studies on green roof water quality have indicated that extensive green roofs are a source of phosphates, and occasionally nitrates, as compared to conventional roofing systems. However, due to the presence of soil media and vegetation, green roofs should be compared to other vegetated sites, as opposed to conventional roofs, for a fairer comparison. In this study, the impact of green roofs on surface water quality is placed in the context of other vegetated land uses, including two types of stormwater control measures (SCMs) as well as non-SCM sites. Site runoff and SCM effluent were evaluated for nitrogen and phosphorus species, chlorides, total suspended solids, and total dissolved solids. Comparisons of concentrations against EPA recommended criteria suggested that the green roof generally retained nitrogen and released phosphorus. Its performance was similar to that of a wooded area, a grassy area, and a mixed-use area, while it was outperformed by a rain garden and a constructed stormwater wetland.
To better gage the effect of the green roof’s volume retention performance on its water quality impact, a nutrient mass balance was conducted for the green roof, and mass loads for the comparison sites were calculated. Mass balance estimation suggests that the green roof’s water quality impacts could be mitigated by its volume retention capabilities. The green roof exports less nutrients than are input to the system from fertilization and atmospheric wet deposition, although overall it exports more than wooded areas, based on drainage area-scaled values. Findings may be used to guide land use planning including implementation of green infrastructure and management of urban green spaces. It is suggested that if nutrient export is a concern and space is available, green roof overflow could be diverted to other SCMs which are designed to remove excess nutrients from stormwater runoff.
Maggie Chase, November 11, 11:30am
The Design and Implementation of a Green Roof Shelter Research Site (People Hub)
Abstract: Green roofs are becoming increasingly popular as urban stormwater control measures (SCMs). Further understanding of the relation between design characteristics, like media depth and vegetation type, and stormwater performance is crucial to effective green roof design. The VUSP’s newest on-campus research site is a green roof shelter, designed to optimize stormwater volume reduction with a small footprint. The semi-intensive modular green roof is a living laboratory for stormwater research and community education. The research focuses on green roof performance for different configurations of growing media, plants, drainage designs and more. The monitoring system includes a custom orifice restricted device (ORD) designed to measure the relatively small magnitude of overflow. The presentation will give an overview of the shelter design and construction process, monitoring system implementation, data logging system, target research questions and STEM outreach.
Gerald Zaremba, October 1, 1:00 PM
“What’s with that huge tank on the third floor of CEER?” A Look into Smarter Stormwater Control Measures (SSCMs) on Villanova’s Campus
As stormwater infrastructure becomes an ever increasing priority in site development, property owners and designers are becoming increasingly tasked with mitigating stormwater in creative ways. While many other sectors of infrastructure and development have embraced new technologies and worked with other branches of engineering, stormwater management has been stuck with the age old practice of infiltration. Unfortunately designers have been held back by outdated design regulations that have been slow to adopt the latest research in their guidelines.
A recent grant through the NSF will allow Villanova University to retrofit 3 of its on campus SCMs with some of the latest technology for stormwater management. In partnership with OptiRTC and The University of Pennsylvania, Villanova will be retrofitting The Green Roof Research Site, The Constructed Stormwater Wetland, and The Treatment Train in order to increase their performance as well as to study maintenance programs for stormwater infrastructure. The benefits of this technology can help downsize traditional SCMs, help ensure an SCMs longevity and continued performance, as well as drive down costs of installation and long term maintenance. This presentation will explore the three sites above and discuss present and future modifications underway as well as goals and expected outcomes of the project.
Andrea Welker, Ph.D., PE
My observations of the status of stormwater management practices in Ireland
Low Impact Development (LID) or Green Infrastructure (GI) stormwater practices are gradually gaining acceptance in the United States. These practices are also being used to control stormwater in Ireland, where they are dubbed Sustainable Drainage Systems (SuDS). This talk will describe the observations made by the author about the status of SuDS in Ireland.
Erica Forgione, August 19th, 12:00 pm
"Fate and Transport of Road De-Icing Salt in a Constructed Stormwater Wetland"
Road de-icing salt is one contaminant of concern in stormwater runoff with an estimated 15 million tons of salt being applied to U.S. roads every year. Road salt (usually NaCl) is soluble, and chloride (Cl) is a conservative tracer, meaning that it will not degrade over time. While many assumed that road de-icing salt would wash through watersheds with spring rains, as much as 77% of chloride has been shown to be retained within a watershed (Liptak and Mitsch 1996-98) and chloride levels may remain elevated late into summer months (Gardner and Royer 2010). Chloride has been shown to affect the survival and health of many amphibians at heightened levels (Karraker and Gibbs 2011) and increased chloride concentrations has resulted in increased metals concentrations (Endreny et al 2012). Because chloride poses a possible threat to downstream waters, a study was performed to study the fate and transport of chloride on Villanova’s campus.
The study aims to do a mass balance of chloride over two years in Villanova University’s constructed stormwater wetland (CSW) from the campus’ impervious surfaces, through the wetland, and into Mill Creek (the natural downstream waters) to see if there is any net retention or export of chloride. In addition, concentrations of chloride taken at intervals over a four year period for both storms and base flow events are compared to EPA chloride freshwater recommended standards to determine if Villanova’s CSW outflow meets that criteria. Correlations for TDS, conductivity, and chloride concentration are created in the course of this study and equations were formed to compare values of TDS, conductivity, and chloride. A unique k value for the CSW was determined for the equation Conductivity = k * TDS. The study aims to educate about the fate of road de-icing salts to inform sustainable action moving forward.
Ryan Lee, July 7th, 10:00 am
Evaluation of Soil Proxies for Rain Garden Design
The three main components that determine the performance of a rain garden are the inflow volume, the size of the rain garden, and the soil hydraulic properties. Because soil hydraulic properties are often difficult to determine, proxies such as soil textural class or hydrologic soil group are often used instead of actual properties. The use of class-average soil properties for these proxies is a persistent practice in water resources engineering, but the effect of this practice has not been assessed or validated for use in rain garden design. This research uses a large dataset of soil hydraulic properties along with computer simulations of a rain garden to determine the effectiveness of these soil proxies for rain garden designs, specifically showing whether such proxies can determine the need for an underdrain, the effectiveness of fill media, and the overall expected performance of rain gardens during a design storm.
Jhoanna Montaño Valdez, July 6th, 12:00 pm
Fate and Transport of Algae in a Constructed Stormwater Wetland
Abstract: Constructed Stormwater Wetlands (CSWs) are one type of Stormwater Control Measure (SCM) to treat stormwater runoff. The main objective of this research is to analyze the fate and transport of phytoplankton (i.e. free floating algae) in the Villanova University Constructed Stormwater Wetland (VU CSW). The VU CSW receives runoff from the Main and West campus and this runoff contains nutrients such as nitrogen and phosphorus which contribute to the algae growth, and hence, leads to eutrophication of the VU CSW. It also produces a measurable amount of algae during baseflow conditions that are washed away during storm events.
The concentrations of chlorophyll a (an indicator of algal content), dissolved oxygen, organic matter, temperature and nutrients in the VU CSW will be presented in an attempt to correlate algae growth with nutrient depletion. In addition, the mass of algae washed from the wetland during storm events will be quantified to determine if this export of algae may have a negative effect on downstream water quality.
Kyle Johnson, June 4th, 12:00 pm
SCMs are Forever: Towards Sustainable Design and Maintenance Practices for Multiple Generations of SCMs
Abstract: Over the past several decades research for green stormwater infrastructure (GSI) has been successful in demonstrating proof-of-concept and has resulted in large cities investing in large-scale GSI implementation projects that will span decades. While proper design, installation, and regular maintenance practices have evolved, there are still a lot of questions and assumptions made regarding the longevity and end-of-life of GSI systems. Using a multiple life cycle perspective, the potential cost and environmental impact savings of GSI “renewal” – as opposed to full decommissioning/replacement – are outlined for several stormwater control measures by incorporating elements of eco-efficiency, the Circular Economy, and industrial ecology. A “multi-generational approach” that aims to support the development of best practices for SCM design, maintenance, disassembly, and material reuse is broadly discussed. Recommendations are made for future studies that focus on extending the useful life of SCM materials.
Amanda Hess, May 6th, 12 pm
Evapotranspiration and Infiltration in Rain Garden Systems
Abstract: Quantification of evapotranspiration (ET) and infiltration from vegetated stormwater control measures (SCMs), such as rain gardens, is necessary to properly assess their volume reduction potential. Weighing lysimeters at Villanova University mimic three bioretention rain garden designs and measure water budget parameters to determine how design elements impact ET and infiltration (percolation). The designs compare two soil medias: a loamy sand (72% sand, 12% silt, 1% clay) and sand (96% sand, 4% silt, 0% clay), and different drainage systems: a controlled valve and internal water storage (IWS) outflow. The controlled valve outflow allows a user defined flow rate. The IWS outflow maintains a storage volume within the media.
A custom distribution system was built to simulate excess rain delivered to a rain garden during natural storm events. In Pennsylvania, SCMs are often sized to control a multiple (typically 5:1 for rain gardens) of a selected rain event. Trials were performed in April and August 2014 for half open controlled valve configurations. Both loamy sand and sand soils with a controlled valve configuration showed an average ET of 3.1 mm per day for 7 days after simulated 5:1 events. Sand soil with an IWS showed an average of 6.0 mm per day for 7 days after simulated 5:1 events. Simulated storm events produced larger ET rates, on average, than that of a 1:1 ratio. Comparisons of predictive equations show the ASCE Penman-Monteith under-predicting and Hargreaves over-predicting observed ET, but follows the trend of each lysimeter.
Raquel Burlotos, April 29th, 11:30am
A study on porous asphalt at the Morris Arboretum
Abstract: The Morris Arboretum has one of the oldest porous asphalt sites in the country dating back to 1982. Today the asphalt is being replaced because it no longer infiltrates, and is wearing down. Because of this, the Villanova Urban Stormwater Partnership decided that it would be advantageous to perform a forensic study on the asphalt examining its current condition before replacement. The study focused on observing why the asphalt no longer infiltrates, quantifying the amount contaminants trapped in the asphalt, determining the asphalt's porosity and determining the asphalt's current infiltration rates. Results revealed high metal concentrations from the asphalt, low infiltration rates, and failure due to age and clogging.
Ashley Neptune, April 29th, 11am
Water Quality Evaluation of Storm Sampling Techniques for a Constructed Stormwater Wetland
Abstract:Stormwater control measures are built in order to address the issues of stormwater runoff. These issues are primarily focused around volume control and water quality treatment. Villanova University's Constructed Stormwater Wetland (CSW) was recently reconstructed in 2010 to improve treatment efficiency by adding meanders to hold runoff in the treatment system longer. From 2011 to present the CSW is sampled once to twice a month for storm and baseflow events. Until April 2014, sample collection for storms involved gathering samples 12 to 24 hours after rainfall ended. Though the flow rates during this time are still above average baseflows, the concentrations are not representative of first flush conditions. The use of automated samplers at the inlet and outlet permit for real time stormwater quality monitoring at the CSW. A comparison study between the grab sampling storms and autosampler events was performed, in addition to mass analysis for the automated samples.
Catherine Barr, March 25th, 12pm
Nutrient Export for a Green Roof in Comparison to Other Land Uses
Recent studies on green roof water quality have indicated that extensive green roof systems are a source for phosphorus, and occasionally a source for nitrogen as compared to conventional roofing systems. Due to the presence of soil media and vegetation on green roofs, a comparison to traditional roofs reveals little about relative nutrient quantities released. The Villanova green roof was compared to other suburban vegetated areas for nutrient export. The water quality parameters evaluated included nitrogen and phosphorus species, chlorides, total suspended solids, and total dissolved solids. Where applicable, US EPA recommended nutrient criteria for rivers and streams, and for lakes and reservoirs, were used as a reference point to nutrient parameters. Results indicated that the green roof generally retained nitrogen and released phosphorus; its performance was similar to or better than that of a grassy area and a wooded area in terms of nutrient retention, and performed similarly to an area that was at least 50% impervious. In addition, a comparison of quality data from overflow samples revealed that a nearby wetland and rain garden outperformed the green roof in terms of nutrient retention. It is suggested that if nutrient export is a concern and space is available, green roof overflow could be diverted to other stormwater control measures which are designed to remove excess nutrients from stormwater runoff.
Zachary Zukowski,March 25th, 12:30 pm
Selection of Sites, Instrumentation, and Equipment for a Rain Garden Comparison Study
Rain gardens are vegetated stormwater control measures (SCMs) that reduce runoff volume and high peak flows. Rain gardens promote infiltration and evapotranspiration (ET), thus mitigating the effects of high stormwater runoff that have become common in developed areas. In addition to runoff quantity, rain gardens also help improve water quality by allowing water to infiltrate into an engineered or native soil media. Engineered soils typically contain a high sand content with lower amounts of silts, clays, and organics. Native soils can be used if the hydraulic properties indicate that an adequate infiltration rate is attainable. Additionally, to save construction costs, engineered soils can be mixed with native soils. Rain gardens may also contain a liner and an underdrain. Systems without a liner allow for evapotranspiration and infiltration into the native soil layer, which promotes recharge to the underlying aquifer. Systems with a liner and underdrain typically favor evapotranspiration.
A study was proposed to determine the best rain garden design and configuration for optimum hydrologic performance. This included the use of a liner, the use of an underdrain, soil media, and age of the rain garden. Many rain gardens on Villanova University’s campus were considered, and three rain gardens were selected: the Bioinfiltration Traffic Island, Fedigan Rain Gardens, and Pavilion Traffic Island. The three sites have notably different configurations, soil mixtures, and other defining characteristics. After site investigations, instrumentation was selected for each site, which included pressure transducers, soil moisture sensors, and rain gages. This talk will describe the challenges and soil properties encountered during the site investigations, as well as the process of instrumentation and equipment selection for each site.
Margaret Chase, February 25th, 12pm
The Measurement of Runoff from Vegetated Roof Shelter
Funded by the EPA Urban Waters Small Grant program, the project's purpose is to design, construct and monitor two shelters (e.g. bus shelter or picnic table covering) with vegetated roofs in the Darby Creek watershed in southeastern Pennsylvania. The shelters will be living laboratories used for community education and stormwater research. The research component will focus on green roof performance for different configurations of growing media, plants, drainage designs and more. The education component includes collaboration with the Eastern Delaware County Stormwater Collaborative and Upper Darby High School to introduce community members to green roof technologies and introduce students via the science curriculum to the hydrologic processes of green roofs.
A key component of these living laboratories is to precisely and accurately measure the inputs and outputs of the green roof to quantify performance. The magnitude of outflow (drainage) measurements is relatively small for these small-scale green roofs, thus requiring a custom solution to measure outflow. The presentation will give an overview of the project goals and also focus on the method developed for runoff measurement from the green roofs.
Conor Lewellyn, January 14th 2015, 12pm
An Extremely Undersized Infiltration Trench 10 Years Later
Infiltration trenches are a stormwater control measure (SCM) used in urban and ultra-urban areas to provide stormwater runoff volume reduction. Legacy infiltration trenches are difficult if not impossible to maintain and were often built without pretreatment. As runoff with high suspended solid loads enters an infiltration trench there is continual buildup of solids that clog the infiltrating surface, decreasing the hydraulic conductivity at the soil interface and the performance and longevity of these systems.
The present study builds on previous work at Villanova University on an extremely undersized infiltration trench (directly connected impervious drainage area to SCM area of 160:1) to artificially accelerate annual loading to evaluate long-term performance. Ten years and 1270 cm of rain later, infiltration through the bottom of the trench has ceased and the sides have slowed as well. Recession rates have reached an equilibrium point where they no longer improve or decrease. Although recession rates have slowed considerably since 2004, reduced infiltration still occurs in the bottom layer of the IT.
Gerald Zaremba, January 14th 2015, 12:30 pm
Optimizing Green Roof Design for Evapotranspiration
Green roofs are an effective, yet costly stormwater control measure that reduces runoff volume through ET, and can provide other services, such as improved building insulation and reduced urban heat island effect. For green roof systems to be competitive as a low impact development strategy, they must be designed to maximize ET. Understanding each component’s process in a green roof design is the key to designing a green roof to perform optimally.
Evapotranspiration (ET) is a primary mechanism for removal of water in a green roof. When adequate water is available, the ET rate is limited by the energy-available. However, when the system is water-limited then less ET will occur than is climatologically possible, thus causing the green roof to perform sub-optimally. One way to retain more water within the green roof is to minimize drainage (outflow) by altering or restricting the drainage layer within a green roof. In the present work, a green roof with a drainage layer is compared to a lysimeter without a drainage layer to determine if hydrologic performance is enhanced or compromised in either system.
Preliminary results from the Villanova University green roof systems show that the under drained system has approximately 65% of rainfall go to ET, while the undrained system showed 77% ET from April through November 2013. However, the system without drainage has seen as high as 88% annually go to ET in drought years. Additionally, the plants appeared healthier during the drought in the undrained system than in the drained system.