Water: Nonpoint Source Success Stories
Nebraska: Hanscom Park Lake Rises to New Heights
Hanscom Park, the oldest remaining park in the Omaha, Nebraska, park system, provides numerous recreational activities for city residents. Its lake provides winter ice skating and summer fishing opportunities and serves as the aesthetic focal point of the park. Recently, however, the lake fell victim to age. Its banks collapsed and eroded, filling the lake with sediment. The shallow water became eutrophic; sediment continually resuspended and dissolved oxygen all but disappeared. The lake lost its aesthetic value, and the fishery failed.
In 1992, the City of Omaha's Parks, Recreation, and Public Property Department in cooperation with the Papio-Missouri River Natural Resources District, the Nebraska Department of Environmental Quality, and EPA Region 7, began to restore Hanscom Park Lake. Project objectives were to increase the water depth to restore the fishery and prevent further degradation by redesigning and replacing shoreline structures. The six major components of the restoration project included removing sediment, stabilizing the shoreline, replacing the overflow and inlet structures, installing an aeration system, and improving access to the lake.
Lake reconstruction activities
Restoring Hanscom Park Lake was a multi- task activity, beginning with dredging the lake to a new depth of 8 feet. Among shoreline improvements, a new concrete footing was constructed below water level with a stone wall extending 1 foot above the original grade. This design increased the lake's depth at minimum cost.
Next, drainage pipes were installed to allow the springs to discharge under the stone wall rather than weep through it. The old inlet pipe was removed and a new 2-inch copper line was extended from an existing water line to a new access hole and inlet structure. The drain line now extends under the stone wall and discharges out of sight below the water line. Finally, an electric-powered fountain aeration system was installed to maintain oxygen levels and serve as an aesthetic focal point.
Access to the lake was also improved. A walkway was constructed and shoreline pads were extended from the walkway to the stone wall. The walkways provided a stabilizing structure around the lake and directed foot traffic away from the shoreline. The shoreline pads allowed close access to the lake, however, so that visitors may fish in deep water without disturbing the shoreline. The newly restored lake was quickly restocked with carp, a favorite of park fishing enthusiasts.
Data collection and analysis
Monitoring results indicate that the project has had a positive impact on water quality (Table 1). The concentration of total suspended solids was reduced from an average of 21 milligrams per liter (mg/L) to 5.0 mg/L. Total phosphorus decreased from 0.08 mg/L to 0.05 mg/L. Organic nitrogen declined from an average of 0.85 mg/L to 0.72 mg/L. The concentration of chlorophyll a decreased from 27.17 mg/m3 to 0.24 mg/m3. Water clarity increased from an average of 7.5 inches to 96 inches. It should be noted that while these differences are large, statistical confidence cannot be assessed because the sample size is too small.
|Table 1. Monitoring results.|
|Total suspended solids||76 percent reduction|
|Total phosphorus||38 percent reduction|
|Total nitrogen||15 percent reduction|
|Chlorophyll a||99 percent reduction|
|Water transparency||1100 percent increase|
The aesthetics of Hanscom Park Lake are vastly improved and the lake area is much simpler to maintain as a result of this restoration project. Increased recreational use of the lake and adjacent areas for fishing, family and group picnicking and walking is immediately apparent. Pedestrian traffic around the lake has increased as people come to the park in greater numbers and with more frequency. Use of the walkway and shoreline pads makes the lake accessible but reduces the visitors' encroachment on the shoreline. Because section 319 funding was available for this project, the city of Omaha was able to leverage city funds otherwise dedicated solely to Hanscom Park Lake to initiate a watershed management planning effort for the much larger Zorensky Lake.
|CONTACT: Elbert Traylor
Nebraska Department of Environmental Quality