Assessing stormwater reduction using green infrastructure: Gary City Hall (Gary, Ind.)
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The effectiveness of green infrastructure (rain gardens and decreased impervious surfaces) at reducing stormwater runoff is being assessed at a redevelopment project at Gary City Hall (Gary, Indiana). This study will evaluate pre- and post-construction hydrologic conditions using data collected by monitoring storm-sewer flow, groundwater levels, soil moisture, and meteorological conditions.
INCORPORATING GREEN INFRASTRUCTURE INTO URBAN DEVELOPMENT
Gary, Indiana, is located on the southern-most shore of Lake Michigan and is representative of the Great Lakes’ coastal sandy soils and subsurface deposits that encourage infiltration. In many urban watersheds, including Gary, stormwater (excess rainfall or snowmelt that is not absorbed by the ground) can cause problems such as flooding, erosion, and sedimentation; property and habitat damage; harm to fish and aquatic organisms; and decreased water quality.
Like others in the Great Lakes basin, the City of Gary is investing in the redevelopment of abandoned areas in its urban core and is interested in exploring the potential stormwater-reduction benefits of green infrastructure. Green infrastructure is a group of urban stormwater control measures that take advantage of natural processes to reduce or delay peak flows and volumes of stormwater runoff by holding stormwater on-site, encouraging infiltration, and enhancing evapotranspiration (ET). One particular area surrounding Gary’s City Hall is currently undergoing redevelopment. As vacant properties are removed, those lands are being repurposed using types of development that enhance stormwater infiltration, increase opportunities for adding green space, and minimize stormwater loads by redirecting runoff and encouraging groundwater recharge.
The City of Gary recently redeveloped a parking lot south of City Hall using green infrastructure and invited USGS hydrologists to work with the design team to incorporate a monitoring plan and equipment installation into the reconstruction. The redevelopment included the removal of impervious cover, installation of structures to redirect runoff from the storm-sewer system and parking lot to a central rain garden, and the addition of peripheral grassed areas. The USGS worked with the landscape engineers to ensure that the features included in the final design allowed monitoring of surface inflows and groundwater conditions within the rain garden infrastructure. The city is also planning additional redevelopment that would redirect stormwater from downspouts on the City Hall roof to additional rain gardens and include a permeable paver plaza for community events.
In collaboration with the City of Gary and the Great Lakes Restoration Initiative, this study will quantify the effects of planned stormwater reduction strategies and infrastructure on the hydrology of the highly permeable surficial aquifer material and storm-sewer flows. By monitoring conditions before and after the installation of green infrastructure, this study will assess:
- Volume of precipitation and snowmelt at the green infrastructure installation and a control site
- Volume of water lost to evapotranspiration
- Discharge to storm sewers to characterize changes in runoff volume due to increased infiltration
- Changes in the volume of stormwater treated and infiltrated
Additionally, due to the geology and buried infrastructure of the Gary area, the effectiveness of infiltration basins located on lots of filled or disturbed land can be evaluated through the comparison of hydrologic data collected on both types of land subjected to the same rainfall and snowmelt conditions.
Monitoring: The USGS has installed and will monitor and analyze hydrologic data from a network of groundwater observation wells, soil moisture sites, storm sewers, and a weather station to understand the effect of the rain garden and other green infrastructure installations on stormwater reduction. Installation of this network will be conducted by the USGS and monitoring will take place before and after site rehabilitation (including the installation of green infrastructure) to fully understand the water budget. Soil moisture and groundwater levels will also be monitored in nearby parkland areas with no land-use change (the control site) for the length of the project to use for comparison purposes. The data collected will be used to quantify the effect of increased infiltration on the highly permeable surficial aquifer.
Modeling: The installation at Gary City Hall will be modeled with a stormwater routing model to help identify processes that have the greatest influence on the observed water balance and the uncertainty associated with them.
This study addresses both the mitigation of adverse impacts of stormwater runoff and the development of approaches to rehabilitate abandoned land in urban settings, both of which are major issues within urban areas of the Great Lakes. The effectiveness of stormwater infiltration structures has been measured in environments with low permeability surficial sediments, but such systems have not been studied or monitored in highly permeable environments (like that of northwestern Indiana). The data gathered through this study can be used to model the application of similar infrastructure in urban areas with abandoned lands showing the potential effects on groundwater levels and discharge to storm sewers and surface waters.
By monitoring the hydrologic conditions before and after redevelopment and comparing the redeveloped site against a control site, the effectiveness of the green infrastructure to alter the urban water cycle by diverting stormwater and promoting evapotranspiration and infiltration can be measured. Data from this study will be used to evaluate the benefits of future redevelopment proposals to reduce impervious cover and remove vacant housing, for replacement with green space and green infrastructure.
Monitoring at the City Hall in Gary is underway. Click on the links below to view current data and access historical measurements. (Some data may be provisional.)
A webcam was installed to monitor construction activities and site conditions.
Prior to site construction, the following sites were installed onsite and began collecting data in May of 2016:
One weather station measuring local meteorological conditions that will be used to estimate potential evapotranspiration.
Four groundwater monitoring wells with three soil moisture sensors each to measure the groundwater elevations and the response to precipitation events (recharge):
Located adjacent to City Hall:
Located in nearby Gary City Parks:
One storm sewer pipe monitor with webcam to measure stormwater runoff discharging to the storm sewer from the parking lot drains south of city hall and for gage height quality assurance.
Following the completion of construction on the storm water reduction infrastructure in June 2017, the following additional monitoring equipment was installed:
Five flumes to measure the amount of water entering the rain garden from the surrounding parking lot and roadway:
Three pair of soil moisture sensors below the rain garden:
One storm sewer pipe monitor to measure discharge to the storm sewer from the rain garden overflow structure