Grantee Research Project Results
Final Report: Next Generation Volume Reduction Green Infrastructure Stormwater Control Measures in Support of Philadelphia's Green City Clean Waters Initiative
EPA Grant Number: R835556Title: Next Generation Volume Reduction Green Infrastructure Stormwater Control Measures in Support of Philadelphia's Green City Clean Waters Initiative
Investigators: Traver, Robert , Welker, Andrea , Wadzuk, Bridget , Clayton, Garrett M , Eisenman, Sasha W , Sen, Siddhartha , Sanders, Tonya , Hunter, James , Smith, Virginia , Shin, Hyeon-Shic
Institution: Villanova University , Morgan State University , Temple University
EPA Project Officer: Packard, Benjamin H
Project Period: September 1, 2013 through August 31, 2017 (Extended to August 31, 2018)
Project Amount: $1,000,000
RFA: Performance and Effectiveness of Green Infrastructure Stormwater Management Approaches in the Urban Context: A Philadelphia Case Study (2012) RFA Text | Recipients Lists
Research Category: Watersheds , Water
Objective:
The overarching objective of this research has been to monitor and demonstrate high-performing next generation green infrastructure (GI) practices that are required for highly urbanized communities to effectively meet their obligations under the Clean Water Act. The research utilized a more holistic approach, considering hydrological, geotechnical, environmental, and economical constraints, to utilizing both the infiltration and evapotranspiration (ET) capabilities of various GI depending on the goals and needs of a specific location. Through this research we were able to improve our understanding of the infiltration and ET processes to increase runoff volume capture performance. The project tasks are:
- Evaluate the current generation of GI stormwater control measures (SCMs) to develop, design, and validate the next generation of GI SCMs
- Evaluate benefits of GI SCMs to neighborhoods
- Develop a collaborative research environment for GI within the Philadelphia Community
- Disseminate results to include STEM educational outreach (K-12)
Summary/Accomplishments (Outputs/Outcomes):
Task 1: The research team worked with the PWD (Philadelphia Water Department) to select three previously constructed SMP (Stormwater Management Practices): The Giraffe Lot Philadelphia Zoo Rain Gardens, the Morris Leeds Tree Trench, and the Roosevelt Playground Sidewalk Planters. These sites were monitored for inflows and outflows, water levels, soil moisture and weather parameters.
The Zoo site (plan view provided above), which comprises two rain gardens connected by a grass swale, was able to mitigate flows from both natural storms and simulated runoff test (SRT) events greatly exceeding the design capture criteria without overflow. It was observed that the inlet performance was crucial to runoff capture, and scheduled maintenance was needed to keep the inlet free from blockage by trash and leaves. As the system capacity greatly exceeded PWD requirements, the results demonstrated that dynamic design (considering soil infiltration and evapotranspiration during the event) is needed to more accurately depict the performance and design for next-generation designs. For systems with multiple components (like the Zoo site), the role of each component needs to be considered individually and related to the regional climate and rain patterns to promote more efficient utilization of each component. At this site, the underground infiltration bed was built to the side of the lower rain garden, which showed good performance by adding storage and increasing the infiltration footprint; therefore, side gravel seepage beds can be a useful alternative to booth infiltration.
The Morris Leeds site (plan view and profile view provided above) comprises an underground rock infiltration bed and five tree pits installed in the infiltration bed. Runoff was collected by inlet structures and entered the infiltration bed via a perforated delivery pipe. The system captured 94% of all runoff but water levels in the infiltration bed never reached full capacity. Runoff was found to overflow during intense storm because of the limited performance of the perforation on the delivery pipe. More perforation (67% more) is needed to transport these intense storms without overflow, and the delivery pipe should be moved closer to the bottom of the infiltration bed to fully utilize the hydraulic pressure in the inlet structure. The research team also found persistent ponding in the inlet structure, indicating clogging of the delivery pipe. The clogging was found to have no impact on performance only during storms as the clog was pushed forward temporarily during storms thus restoring capacity; therefore, the current cleaning frequency is sufficient to maintain functionality. Protective pre-treatment to eliminate trash and floatables is still required to reduce the maintenance and the occurrence of this phenomenon.
During a SRT (use of hydrants to replicate rainfall events) which filled the infiltration trench, the trees did not react to the water in the infiltration bed. Soil water modeling showed that that water did enter the soil of the tree pit, but upward water movement was slow, creating a saturated zone at the bottom of the pit, which was hypothesized to discourage root functioning. It was noted that natural storms never filled the infiltration beds to the root level. This issue can be complex, as it was found (throughout 2015 growing season) that tree responses were the combination of soil moisture, relative humidity, temperature, and solar radiation, not just soil moisture. Among the two Morris Leeds tree species (London plane and Freeman's maple), London plane has higher overall amount of transpiration.
Temple University also studies other tree species near the Morris Leeds site, and found that the responses in transpiration efficiency are diverse. Some trees are risk takers (i.e. increase transpiration when air gets dried) while some are risk-avoiders, indicating the importance of goal identification during plant selection. The research team also found that tree trunk growth is related to transpiration efficiency, and higher leaf investment (i.e. higher mass per unit leaf area) does not mean higher transpiration efficiency.
The Roosevelt site (plan view and profile view provided above) comprises two pairs of planters which receive street runoff from the street. An infiltration bed was installed beneath each pair of planters, and each planter has an overflow pipe transporting water (above a certain depth) to the infiltration bed. No overflow to the combined sewer inlet was observed. Runoff enters the overflow pipe only when the volume of infiltration-excessive runoff exceeds the above-ground storage space; therefore, the research team recommended increasing the above-ground storage space or footprint as an alternative to the overflow pipe and infiltration bed system. The research team also found that soil infiltration rates positively correlate to the depth of soil in planters. Deeper soil was hypothesized to be able to resist a reduction of infiltration rate caused by trampling during construction or maintenance activities.
An investigation on the infiltration beds revealed that these two beds have quite different performance, and the curves of water recession speed vs. water depth of the two are both highly non-linear. This could be caused by the highly non-uniform native soil, which is silty sand with a significant portion of urban fill. Three groundwater observation wells were adjacent to the site, and groundwater mounding was observed. However, the magnitude of mounding was small (less than about 3 cm) and the effect of mounding disappeared 3 meters away from the site.
At the subwatershed scale, infiltration SCMs (such as rain garden, tree pits, or planters) perform similarly, and thus their effect in a subwatershed is considered cumulative. A daily water budget tool was developed using continuous rainfall and temperature records to evaluate SMP infiltration and evapotranspiration performance, which can be useful for design guidance and future climate change adaptation.
As part of the research tasks, low-cost sensors and data loggers were used to replace commercial counterparts. Results showed that low-cost wireless data logging devices coupled with commercial sensors can be an effective alternative, but low-cost soil moisture sensors are not feasible at this point.
Task 2: Morgan State University reported that even though the implementation of "Green City, Clean Waters" initiative can reduce water pollution and runoff volume, the sum of indirect benefit does not outweigh the installation cost. This needs further investigation because "stormwater saving" (part of the indirect benefit) considered only property damage from flooding and reduced loss of soil and habitat due to erosion and sediment flow, without considering the saving on stormwater sewer construction and operation if GI is not adopted. Thru surveys, Morgan State University also reported that public opinions (in terms of housing prices, willingness-to-pay, and visual appreciation) towards different types of GI are mostly consistent, but diverse on certain aspects. Tree trenches promote housing price the most efficiently, and rain gardens were found to be the most efficient in improving the visual landscape. Cost was the most important factor in GI selection, while the mean willingness-to-pay was $37/person.
Task 3: Villanova University, Temple University, Morgan State University, as well as Swarthmore University and University of Maryland at Baltimore County (UMBC) and University of New Hampshire, which have separate STAR projects, worked together over the course of the research. Faculty and students of Villanova and Temple Universities also presented results from this project in various venues.
Task 4: In spring 2015-2018, Villanova University held monthly afterschool programs at the recreational center of Roosevelt Playground, and some of these activities were aligned with and directly supported by the FarmPhilly organization. In summer 2015-2018, Villanova University worked with the recreational center to host summer campers for a day at Villanova University. In spring 2017, the afterschool partnership has expanded to working with volunteers from FarmPhilly, and a semester-long STEM project for local high school students was created with the collaboration with EPA Region 3 scientists. These activities continue.
Conclusions:
The performance of monitored SCMs in this project exceeded the design volumetric removal metric. All three sites had additional capacity that was underutilized, or not available due to hydraulic or drainage area limitations, or simply not needed.Targeted utilization can be achieved by incorporating infiltration in design metrics and defining the role and metrics for each component.
2. Simulated Runoff Test, which is currently utilized by PWD, is an invaluable tool to evaluate the hydraulic pathways and infiltration capabilities of SCMs to ensure correct design and construction. By allowing measured and controlled inflow, the use of SRTs was also of value in understanding the roles of the SCM components, infiltration performance, and enabled research for each of the three sites.
3. The management of trash and floatables requires consideration of ongoing maintenance in the SCM design. All three sites required regular scheduled maintenance.
4. A planning spreadsheet model relating climate (rainfall and temperature), storage, and infiltration / evapotranspiration capacity is a valuable tool to understand and tailor design metrics to regional patterns, and can be applied to climate change adaptations in the future with more research.
5. Monitoring of Urban SCMs can be achieved with the use of solar power, a cross between commercial sensors and low-cost communication and data recorders, despite the challenges of the urban condition. Instrumentation needs to be validated in the lab and tested for field conditions before installation. Accurate as-built plans, and preconstruction soil testing results are needed.
6.GI has positive benefits on runoff colume reduction and quality and mitigation: however, the dollar value of indirect benefits such as stormwater saving, electricity saving, air quality saving, property value, natural gas saving, and CO2 saving do not meet the investment on GI installation. Further investigation is needed on this conclusion because "stormwater saving" considers only property damage from flooding and reduced loss of soil and habitat due to erosion and sediment flow. It did not consider the saving on stormwater sewer construction, and operation if GI is not adopted.
Other SCM site-based conclusions are presented in the report.
Journal Articles on this Report : 3 Displayed | Download in RIS Format
Other project views: | All 18 publications | 4 publications in selected types | All 4 journal articles |
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Type | Citation | ||
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Tu M, Traver R. Performance of a Hydraulically Linked and Physically Decoupled Stormwater Control Measure (SCM) System with Potentially Heterogeneous Native Soil. WATER 2019;11(7). |
R835556 (Final) |
Exit Exit |
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Tu M, Caplan J, Eisenman S, Wadzuk B. When Green Infrastructure Turns Grey:Plant Water Stress as a Consequence of Overdesign in a Tree Trench System. WATER 2020;12(2). |
R835556 (Final) |
Exit Exit |
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Xu X, Dao H, Bair R, Uman A, Yeh D, Zhang Q. Discharge or reuse? Comparative sustainability assessment of anaerobic and aerobic membrane bioreactors. JOURNAL OF ENVIRONMENTAL QUALITY 2020;49(3):545-556. |
R835556 (Final) |
Exit Exit |
Supplemental Keywords:
Stormwater Control Measure, watersheds, cost-benefit, engineering, Pennsylvania (PA), green infrastructure, stormwater management, urban green space.Relevant Websites:
Villanova Urban Stormwater Partnership Exit
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.
Project Research Results
- 2017 Progress Report
- 2016 Progress Report
- 2015 Progress Report
- 2014 Progress Report
- Original Abstract
4 journal articles for this project