In 2013, 3 Rivers Wet Weather conducted a regional green stormwater infrastructure suitability analysis using the EPA's System Urban Stormwater Treatment and Analysis Integration (SUSTAIN) model. The results of this analysis, which are available on 3RWW's Open Data portal, are intended to help municipalities comply with certain wet weather regulations, particularly the Pennsylvania Department of Environmental Protection's geographic information systems (GIS) map submission requirements of the Phase I Municipal Consent Orders. The SUSTAIN modeling work was conducted by 3RWW and finalized May 15 2013.
SUSTAIN is a planning-level analysis that could be used by municipalities to evaluate the potential for incorporating site specific green stormwater infrastructure (GSI) methods and projects into their source reduction studies. The results are informational only. Locations for GSI must be further screened based on local information, hydraulic performance (runoff capture), and cost to determine the true feasibility of GSI for sites and projects.
The SUSTAIN analysis is conducted within geographic information systems (GIS) software. At its core is an overlay analysis methodology, which is conducted by bringing layers of geo-based information--such as the slope of the land, distance to streams, and soil composition--together in a GIS, where they are analyzed for spatial coincidence. Specific criteria related to those layers determines the sutiability of any given location for different types of green stormwater infrastructure.
The mapping criteria used in the analysis are described in the following table:
| GReen Stormwater Infrastructure Suitability criteria | Drainage Area (Acres) | Drainge Slope (%) | Impervious (%) | Hydrological Soil Group | Water Table Depth (ft) | Road Buffer (ft) | Stream Buffer (ft) | Building Buffer (ft) |
|---|---|---|---|---|---|---|---|---|
| Bioretention | < 2 | < 5 | > 0 | A-D | > 2 | > 5 | > 25 | > 15 |
| Constructed Wetland / Wet Pond | < 25 | < 15 | > 0 | B-D | > 2 | > 25 | > 100 | > 100 |
| Grassed Swale / Bioswale | <5 | <4 | n/a | A-D | > 2 | < 100 | n/a | > 15 |
| Infiltration Basin / Trench | < 10 | < 15 | n/a | A-B | > 4 | > 25 | > 100 | > 25 |
| Porous Pavement (Concrete/Asphalt) / Permeable Interlocking Paver | < 3 | < 5 | > 0 | A-D | > 2 | n/a | > 100 | n/a |
| Vegetated Filter Strip / Grass Buffer | n/a | < 15 | > 0 | A-D | > 4 | n/a | > 100 | n/a |
The EPA provides source code and an off-the-shelf Esri ArcGIS toolbox for conducting this analysis [note: as of 2016, the tool is no longer being maintained by the EPA]. More info on SUSTAIN methodology can be found on the US EPA website. Contact mwolinsky@3rww.org for more information about the model. Contact mwolinsky@3rww.org for more information about 3RWW's model run.