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Beauty is in the eye of the beholder this spring at Robbinsdale Park in southeast Rapid City, where a previously wooded gully in the northwest part of the park has been replaced by a massive stormwater detention cell.

When the park reopens Tuesday after being closed for construction since September, park users might find the sight of the detention cell jarring. The cell currently has little to no vegetation and looks like a crater or the bed of a dry lake.

But to the professionals who conceived and built the cell, it’s a masterful mix of aesthetics and functionality.

The cell will fill up with stormwater only during so-called “100-year flood” events. The rest of the time, much of the cell will be dry, grassy and open to public use. A concrete recreational path that winds around the cell — at 1 foot above the 100-year flood elevation — connects with adjacent neighborhoods and the rest of the 107-acre park.

Mike Stanley, of Stanley Design Group, described the detention cell as an improvement compared to the formerly overgrown gully.

“We took all that acreage that was basically unusable space for the park,” Stanley said during a media event organized by city government, “and we integrated it into the neighborhood so that we could connect it up with sidewalks and activate this whole piece of the park that was unusable before.”

The old wooded gully was actually a detention basin, albeit much smaller and less effective than the new detention cell, said Kale McNaboe, of Sperlich Consulting.

“Before, it basically just had a big pipe sticking into the detention cell, and the water just kind of went hog wild and out through one outlet pipe,” McNaboe said.

The new cell can hold 33 acre-feet of water, which is twice the capacity of the old cell. The new cell's concrete impact basins slow the incoming rush of water, and outlet structures release the water slowly, resulting in less stress on downstream drainage workings that ultimately dump into Rapid Creek. The slow flow of water through the cell also allows sediments and other solids to settle out.

Construction of the new cell necessitated some other changes to the park.

A track for bicycle motocross, aka “BMX,” was moved to the southern part of the park. It was also expanded from 850 linear feet of track to 1,200 feet, and some previously high-maintenance dirt corners were replaced with asphalt. Rapid City BMX is scheduled to host its first races on the new track Wednesday evening.

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One of the Harney Little League's baseball fields was removed to make way for the detention cell, but four new fields were constructed in the southwest corner of the complex where there was previously an unused, overgrown field. The new fields will not be playable until next spring, but the league was allowed into the park earlier this spring and has been playing on its other five fields.

In the southeast part of the park, the 1-mile recreational trail that loops through an off-leash dog area was re-paved with asphalt.

And just off the northwest corner of the park, road reconstruction was undertaken on segments of Ivy, Idaho and Nevada streets.

In all, the project cost city government about $4.6 million. Of that amount, $3.4 million was for the stormwater detention cell and street projects, and the other $1.2 million was for the other work in the park.

Further potential improvements to Robbinsdale Park are detailed in a master plan that was developed for city government before the recent construction began. Those potential projects, which are dependent on future budget decisions, could include moving the park’s southern entrance to the intersection of Fairmont Boulevard and Locust Street, for safer pedestrian and bicycle crossings; constructing a large public pavilion; adding a boardwalk to the wetlands area in the park’s eastern leg; planting formal gardens; constructing a skateboard park and a bicycle pump track; and decorating an area of the park with sculptures.

Contact Seth Tupper at

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Enterprise Reporter

Enterprise reporter for the Rapid City Journal.