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Hanscom Park is Omaha’s oldest park. The hilly, forested property was donated to the City for use as a park in 1872, with park improvements designed in the early 1890s by the noted landscape architect, HWS Cleveland. The 58-acre park includes extensive natural green space, picnic areas, a playground, small informal soccer and baseball fields, an indoor tennis center, a splash pool, a dog park, a lagoon, formal gardens, the City greenhouse, and a pavilion.
The Hanscom Park Green Infrastructure Project will explore the possibility of creating green infrastructure features including cascading bioswales, grassed swales, and other above-ground green infrastructure features to better manage area stormwater runoff within the park. These features would increase the amount of rainwater infiltration within the park’s natural areas. The features also would reduce the runoff from the surrounding neighborhoods that is conveyed to the park and enters the City’s combined sewer system. Two areas within the park will be examined. The large ravine in the park’s northeast quadrant will be studied to determine how water could be detained, to increase the amount of groundwater recharge in this natural area. Any improvements within the ravine will be designed to enhance and blend with natural existing conditions and habitat. Stormwater from the park’s southwestern corner and the adjacent neighborhood to the west will be studied to determine how best to convey this water to locations in the park where it can infiltrate into the ground. In the southwestern corner, water cleansed by the green infrastructure features may be used to supplement the water level in the lagoon. One other stormwater management technique that will be studied is the possibility of storing additional water in the park’s lagoon for short time periods after large rainstorms. This will involve adding an automated water level control device to the lagoon’s outlet structure. It would allow the City to release this excess water into the combined sewer system after peak storm flows. Controlled release of this water would help prevent sewer overflows and avoid taxing the city’s wastewater treatment plant. The device might also be used to lower the lagoon’s water level prior to large storms to increase the volume that can be stored in the lagoon during storm events. If used, this green infrastructure feature along with the increased infiltration throughout the park, would assist the City in meeting the goals outlined in Omaha’s CSO Long Term Control Plan regulated by the Nebraska Department of Environmental Quality.
The Hanscom Park Green Infrastructure project is one of five pilot “green” stormwater projects. The term “green infrastructure” involves the use of man-made features or structures that imitate actions that naturally occur in nature. In this case, natural and improved areas of soil would be used to infiltrate rainwater near where it falls. This would decrease the volume and flow rate of runoff entering the combined sewer system. These five pilot projects would allow the City to gain a better understanding of the effectiveness, costs, and performance of green infrastructure. The City would use this knowledge in designing and managing future green infrastructure projects.
This project would decrease the volume and flow rate of stormwater entering Omaha’s combined sewer system. It would facilitate local groundwater infiltration improving groundwater quality and quantity. Cleansed water from the southwest drainage area may help maintain the water level in the park’s lagoon. Urban wildlife habitat and plant diversity would be enhanced as a result of the green infrastructure features. As a pilot project, it would allow Omaha Public Works staff to learn more about using these stormwater management strategies.
Sustainable and Green Concepts
This project leverages the natural soils in the park’s northeast ravine to reduce the volumes and rates of flow of stormwater runoff from the surrounding areas by increasing infiltration. Local groundwater would be replenished by the stormwater that is infiltrated into soils in the ravine, and other green stormwater infrastructure features. This groundwater would likely help supplement the lagoon’s water level. Recycled materials would be used in the design where appropriate. Concrete walk and street pavement removed during construction could be recycled for use as road base on other projects. Existing park uses would remain. Urban wildlife watching would be enhanced by the improved wildlife habitat and expanded biodiversity within the park. New trees would be planted within the park to replace any trees or shrubs removed due to construction. Native plant species would be used for the mitigation plantings (grasses, sedges, shrubs, trees).
Existing city-owned green space is being “multi-purposed” to help manage stormwater, while still providing a diversity of high-quality recreational uses. Other, non-CSO Program improvements are planned for the park. Planning for these non-CSO improvements is being completed at the same time as the CSO improvements. Local neighborhood leaders are actively involved in both design processes and hope to attract private funding to further enhance the park. Through implementation of this project it is expected that the magnitude, frequency and duration of overflows would be reduced.