The Town Council learned last week that it could cost up to $1.5 million to modify and upgrade the storm water drainage system that flows behind Golden Eagle Park Dam.

The council heard a report from Ted Lehman, P.C. of J.E. Fuller, Hydrology & Geomorphology, Inc. Lehman stressed the cost estimate is based only on a concept plan, but does include a 30-percent contingency.

Lehman described two parts to the project. The first addresses channels and water flow within the boundaries of the park and the second goes upstream on Ashbrook Wash to the west side of Golden Eagle Blvd. That part of the project proposes using several hundred feet of gabion basket construction to reinforce a 20-foot high arroyo to control erosion of silt into the wash and downstream.

Lehman said continued erosion along that arroyo could be a threat to private home lots in the future.

Within the park the project would focus on improving the wash channels to better manage the flow. Lehman, as well as Town Manager Grady Miller and Public Works Director Justin Weldy, all stressed that Golden Eagle Park is largely designed as a detention basin for floodwater. The design is to capture runoff behind the Golden Eagle Park Dam to protect downstream residential properties from flooding.

That is one reason that insurance would not cover damage to the park following the October 2018 storm event that flooded ball fields with up to six feet of water. The depth captured behind the dam was as much as 15 feet. The town spent close to $1 million with clean-up and repairs following that flood. Most of the work was flood related but it also included some previously planned improvements.

It was said at the time that the dam and park did what it was designed to do in collecting water. The town had simply not anticipated that much damage with silt and debris. The control building, which had up to 30-inches of water in the lower level, was built to be above a 100-year flood event, Lehman said.

The proposed work within the park boundary includes grading of wash channels, excavation of sediment basins, concrete aprons, bollards designed to slow and trap larger debris and reconstruction of a large debris trash rack at the dam.

There would also be work to reinforce the bridge foundation at Cloudburst Wash at the south end of the park. That bridge was overtopped by flood water in the October 2018 event.

Lehman also explained that a similar rain event in September 2019 was an indication of the effectiveness of some of the improvements made since the storm the previous year. Portions of the ball fields were flooded again but the amount of sediment was significantly reduced, causing only minor damage.

Councilman Mike Scharnow asked about the clean-up efforts that might be required after a storm with the improvements being proposed.

Weldy explained that the bollard design proposed is used elsewhere and is effective. He said the posts stop larger debris and can allow for more time to clean up, reducing costs and manpower.

Councilman David Spelich asked whether there were less expensive options.

“Is this the Cadillac you are proposing,” Spelich asked.

“This concept will help prevent future damage,” Weldy said. “This is what is needed to reduce and minimize the effects of severe storm events.”

Miller noted that this would be a multi-year project to ease the impact on any particular annual budget.

“Were we able to buy some time with the fixes we have already done?” Scharnow asked.

“What we have done is very much makeshift,” Miller said. “We are looking for a more permanent fix.”

Lehman pointed out that the improvements are not maintenance free, and the proposal suggests that annual maintenance costs are about $20,000.

“The severity of the October 2018 damage was partially due to a lack of maintenance,” Lehman said.

“This is a great illustration of what can happen when you need to defer maintenance and cut corners,” Mayor Ginny Dickey said.

The council took no action on the proposal at the Jan. 21 meeting. Miller indicated that initial steps would include complete engineering, which would better define costs. The initial design will be discussed as part of the 2020/2021 budget capital improvement plan, which will come to the council in March.