Date
Tuesday, September 10, 2024
Time
2:30 PM - 3:00 PM
Location Name
M101/102
Name
Lynnbrook Park - Urban Stream Restoration
Track
Green Infrastructure
Description

Lynnbrook Park was born of the need to provide a flood control solution to an urban community greatly impacted during significant rain events. It has become that solution and so much more. A stream restoration project and a multi-faceted park that will provide a place of gathering, education, and recreation for a neighborhood greatly in need of those amenities while improving floodplain connectivity and downstream water quality through stream naturalization. The challenge was set, converting an old City of Chattanooga materials storage yard and WPA concrete-lined ditch into a revitalized natural stream within a public park setting. The existing “stream”, which drains approximately 179 acres in downtown East Chattanooga, had been straight piped/channeled through the linear site since the early 1900’s. To add to the complexity of the urban site, soil tests revealed high levels of lead and extractable petroleum hydrocarbon indicating spent foundry sand from historically local foundries in the area. This foundry sand was found near the surface of the soil and spanned a majority of the site, posing a threat to potential containment migration in the floodplain if not disposed of offsite or buried a specified depth. This requirement paired with the inherent obstacles of the downtown location, set the stage for the need of an innovative design. The restoration design approach begins with incoming flow from an existing 52” culvert being captured and conveyed via a structural storm splitter as a first-flush volume that is discharged into two water quality treatment ponds. These ponds are designed to capture floatables, sediment, and to filter stormwater through the vegetated media before leisurely entering the main stream channel to meander on its way. A previously channelized and armored stream of water, now flows down a natural bed snaking throughout the park with a stable cross-sectional geometry and allowable elevation for access to the floodplain. A stream bed now immersed with pools granting refuge from high velocity flows and riffles ensuring oxygen is infused back into the flowing water. This combination is vital in installing self-sustaining behavior for a functioning stream system. Re-established banks alive with native vegetation provide protection against bank erosion, promote a natural habitat for regional wildlife, and further filter pollutants in the surface water runoff. As the stream reaches the end of its winding path, it exits the site through a low profile, open/natural bottom rectangular culvert as a positive influence for the downstream sections of its tributary. Lynnbrook Park announces its history and its purpose at the very beginning by celebrating the water that serves as its genesis. A public park inhabited with playgrounds for kids of all ages, perimeter walking paths including a pedestrian bridge crossing, and picnic gathering areas all focus on the stream that spans its length. By recognizing the natural treasure that is the stream, the park exhibits abundant educational opportunities to increase water quality education and overall community appreciation of natural stream characteristics in an otherwise urban developed area.