Grantee Research Project Results
Final Report: An Integrated Strategy to Improve Green Infrastructure Approaches in the Urban Context: A Philadelphia Case Study
EPA Grant Number: R835557Title: An Integrated Strategy to Improve Green Infrastructure Approaches in the Urban Context: A Philadelphia Case Study
Investigators: Toran, Laura , Featherstone, Jeffrey , Mandarano, Lynn , Weir, Mark , Nyquist, Jonathan , Meenar, M. , Eisenmann, Sasha , Caplan, Joshua , Van Aken, Benoit , Ryan, Robert
Institution: Temple University , Morgan State University , University of Pennsylvania , Villanova University
EPA Project Officer: Packard, Benjamin H
Project Period: October 1, 2013 through September 30, 2018
Project Amount: $999,995
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 Temple University research addressed four objectives. The Green Campus monitoring program demonstrated low-cost green infrastructure (GI) monitoring techniques, provided testbeds for geophysical characterization of infiltration in urban soils, evaluated green roof media, and modeled effective distribution of GI. In addition, we identified finance mechanisms to promote GI, evaluated triple bottom line (TBL) benefits over time, and assessed implementation practices to determine policy approaches for collaborative and equitable distribution of GI projects. Promotion of STEM education was an important aspect of this project.
Summary/Accomplishments (Outputs/Outcomes):
The Temple University "green campus" monitoring team investigated low-cost monitoring to evaluate stormwater control measures and found simple water level loggers can help identify sites that need improvement or additional monitoring. The water level loggers showed most campus GI is over-designed based on the storm size required to produce overflow. One GI that under-performed was a blue roof on a nearby LEED-certified apartment. Retrofitting roof overflow pipes to extend storage resulted in sediment buildup, showing maintenance is required to achieve the benefits of this GI.
Characterization of infiltration is challenging because of the heterogeneity found in urban environments. The project investigated several geophysical techniques to characterize soils and infiltration patterns. While electromagnetic induction (EMI) worked to map buried foundation materials, the optimal technique for infiltration mapping was electrical resistivity tomography (ERT). Using a new, low-cost ERT system, solar panels, and a custom housing and cable built for this project, we documents evolving non-uniform infiltration patterns during wetting and recovery for different types of urban fill. This method shows promise for rapid characterization of urban vacant lots to assess their role in urban stormwater infiltration and parameterize stormwater models.
Conclusions:
Green roofs are a critical component of green infrastructure, but improved understanding of substrates is needed to provide quick drainage while contributing to plant survival. Experiments were conducted to evaluate how different substrate types affect plant health and to assess performance of green roof design. These experiments quantified the extent that specific grasses delayed storm peaks and reduced outflow volume. Experiments showed introducing biochar to the substrate improved plant survival in drought conditions, although plant growth was reduced. However, given the importance of resilience in reducing maintenance costs, the addition of 10-20% biochar could provide important benefits.
A hypothetical SWMM model of the Temple University campus was constructed to test 54 scenarios using green roofs, rain cisterns, and bioretention basins treating 25% to 75% of roof area (green roofs and cisterns) or 10% to 50% of impervious area (bioretention). These treatment scenarios were distributed in three ways within the sewershed: concentrated near the head; uniformly distributed; and concentrated near the outlet. Each scenario was run using historic rainfall representing above average (wet) years and below average (dry) years. Bioretention was the most effective GI at all levels of implementation with up to 46% reduction in peak runoff and up to 55% reduction in event mean volume. However, it has substantial space requirements. While green roofs are not as effective, there is no additional space required. Cisterns are effective at delaying runoff, but to provide significant volume reduction a reuse plan must be implemented. The placement or geographic distribution of GI does have a measurable impact on its effectiveness. However, this effect appears to be site specific. For example, bioretention concentrated near the outlet of the sewershed is most effective in the northern portion of campus while in the southern portion, the most effective distribution is to concentrate the GI near the head of the sewershed.
Triple bottom line (TBL) analysis was attempted to evaluate multiple benefits of GI. The progress toward the goal of managing 50% of Philadelphia's combined sewer outflow (CSO) area impervious surfaces through GI was assessed using data provided by the Philadelphia Water Department (PWD) and geographic information systems (GIS). The total footprint and contributing impervious area managed by each GI in each CSO area was compared to the total impervious area of the CSO area. The following percentages of impervious cover are managed within each watershed: Cobbs 2%, Delaware 5%, Schuylkill 6%, and Tacony 4%. These values were used to measure the progress-to-goal of 50% impervious cover managed and compared to the earlier 2009 TBL analysis. Improved TBL estimates would have been provided by project construction data, but only limited information was available. The findings suggest possible future actions that the Philadelphia Water Department and various research institutions can take to further the adoption of green infrastructure in the City of Philadelphia and in other communities. For example, the following core metrics should be collected including, at minimum: area vegetated, trees planted, GI footprint, contributing impervious area managed, and date completed. These data need to be collected for both public and private implementations. Additionally, tracking per-project implementation costs would allow for more robust economic analysis. Having a clear, defendable stance on life cycle costs and benefits of various types of green infrastructure can help boost community involvement for public projects and convince private landowners to adopt new practices.
Statistical analysis of community characteristics and GI implementation by census tract revealed that Philadelphia's GI program has resulted in an inequitable distribution with a lower implementation rate in census tracts with higher minority and Hispanic populations. The findings also revealed that privately implemented (regulatory and voluntary) GI projects show inequitable distribution in neighborhoods with more Black and low-income residents. Additionally, public investment in GI, PWD's voluntary and collaborative approaches, are negatively correlated with tracts having higher Asian populations.
The team conducted an assessment to suggest where GI investment is needed to achieve a more equitable distribution. To aid this assessment the team developed a set of variables known as community capitals (human, social, financial, political). In this study, they are used as indicators of a community's capacity to act as a collaborative partner in PWD's public programs to implement GI. After calculating these measures and assessing their positive correlations with GI implementation, the census tracts were ranked as having low, medium, and high capacity. To identify environmental justice communities, the team selected only the census tracts having medium to high rankings of at least one community context variables noted earlier. Using GIS, two categories of environmental justice communities were identified: ones with the capacity to act as effective partners (medium and high capacity) and ones that likely lack this capacity (low capacity) (Figure 1).
The study further evaluated potential for placement of specific types of GI by prioritization and evaluation of suitable GI implementation sites using: (1) prior identification of high priority zones to achieve more equitable distribution based on community context and capacity, developed as part of previous research; (2) restriction of potential implementation sites based on constraints of the built and physical environment; (3) prioritization of potential implementation sites based on proximity to social criteria; and (4) virtual (Google street view) and in situ site evaluation for site feasibility and implementation considerations. Project-specific GIS maps were constructed to help guide future implementation.
Figure 1 Spatial distribution of capacity to install GI based on ranking (1-5) of a set of variables known as community capitals (human, social, financial, political). Increasing GI in identified areas would lead to greater equity in distribution.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
Other project views: | All 23 publications | 4 publications in selected types | All 4 journal articles |
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Type | Citation | ||
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Toran L. Water level loggers as a low-cost tool for monitoring of stormwater control measures. Water 2016;8(8):346. |
R835557 (2017) R835557 (Final) |
Exit Exit |
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Christman Z, Meenar M, Mandarano L, K Hearings. Prioritizing Suitable Locations for Green Stormwater Infrastructure Based on Social Factors in Philadelphia. Land, Special Issue:Landscape Urbanism and Green Infrastructure 2018;7(4):145 |
R835557 (Final) |
Exit Exit |
Supplemental Keywords:
green infrastructure monitoring, urban soils, green roofs, biochar, SWMM, green infrastructure implementation, environmental justice, GISProgress 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