Council OKs drainage plan

Banner Associates image: This image provided by Banner Associates shows potential fixes to drainage problems in the Windermere/Moriarty Edgrebook Additions. Option 3, which includes a detention pond and retaining walls, was the only one that covers all the project goals.

Plan includes pond to address flooding in Moriarty and Windermere

BROOKINGS – The Brookings City Council heard a drainage study in its June 11 study session and listened to public comments during the regular meeting. The group then approved a Master Drainage Plan Priority List. 

City Engineer Jackie Lanning and Kent Johnson of Banner Associates last week presented the Windermere/Moriarty Edgebrook Additions Drainage Study, which is the third project listed on the Master Plan.

“City staff and Banner Associates held three neighborhood meetings with the Windermere/Moriarty Edgebrook Addition residents to present information, receive feedback and answer questions,” according to the attachment to the agenda, available on the city’s website. 

The presentation is also available as an attachment to the agenda.

Residents spoke about the need to make sure the plan worked. 

“If we get a hit again, it’d be cheaper for me to abandon my house,” Jason Evans said. “We have to fix these issues.”

Study session

The presentation started with an overview that centered on the torrential rain on July 19, 2018, which flooded homes in the study area.

Brookings County averaged from 6.5 to 7.75 inches, with one measurement in Aurora coming in at 8.87 inches. The SDSU rain gauge showed 6.27 inches, Johnson said.

The Drainage Study covered 17th Avenue South, including the Moriarty/Edgebrook Addition to the east and Windermere Pointe Addition to the west. The storm water converges into a small area in the middle of the study area that includes a section of 17th Avenue South and a small piece west of that. The study focused on 1833 and 1903 Windermere Way, which are side by side. Both were hard hit during the July 2018 storm, and both are close to drainage pipes.

Johnson presented six potential fixes for the area to the council:

• Option 1: a detention pond in Moriarty Park; it benefits the most properties; approximate cost $427,100;

• Option 2: a retaining wall to prevent water from entering homes, only protects two homes and does not decrease downstream flows; approximate cost $66,900;

• Option 3: a combination of Options 1 and 2; provides additional benefit for north side of valley gutter; approximate cost $462,500;

• Option 4: add storm pipe from Windermere to St. Justice Street to achieve a 100-year flow; does not meet project goals, approximate cost $445,500;

• Option 5: lower the sidewalk in front of 1833 and 1903 Windermere; minimal benefit, approximate cost $5,700;

• Option 6: remove the homes and construct detention ponds in their place; does not decrease flows from 17th Avenue South and Pebble Beach area, approximate cost around $1.1 million, depending on what the homes are worth.

Option 3 was the only one that covers all the project goals, Johnson said.

Councilor Dan Hansen asked for more details on how some of the options worked, and Johnson explained the flow coming through the pipes and where it was coming from.

Councilor Ope Niemeyer asked if there were any discrepancies with the original drainage design to have contributed to the flooding.

There were some that were a couple tenths of an inch higher or lower, and they do impact slightly, “but it wasn’t enough to cause the flooding in this area,” Johnson said.

Some of the grading in the valley gutter area was not completed according to the plan, Lanning added.

Hansen asked if there was a way to construct the 100-year pipe to pull the water from Windermere and 17th Avenue South and Pebble Beach Drive to 20th Street South.

Yes, there probably is a way, but you’d probably have to buy out additional homes to get the piping through them, Johnson said.

There would probably be additional water pressure, which would impact some homes, added City Manager Paul Briseno.

There could still be problems with an event like last July’s, Johnson said.

Niemeyer said the idea of a detention pond was to keep the water in the area and slowly dissipate, but if we put a pipe in there, it will all be down at 20th and Medary, which already has issues. 

“The whole idea is for it to slowly go somewhere and not inundate our neighbors to the south, either,” he said.

Deputy Mayor Patty Bacon agreed it was best to slow it down because the fast-running water in the pipes causes problems.

Councilor Leah Brink wanted to understand better why the city is in this situation. Is it the grading or the channel between the two homes not being built to specifications?

The homes might have been built too low adjacent to a drainage channel, and as the water approaches Windermere Way, it has to go over the road, Johnson said.

“This area of 17th Avenue South was constructed before our new ordinances on detention,” Lanning said, adding, “so now we’re trying to come in with a retrofitted project to help both areas.”

Regular meeting

Study sessions are for information only, but in the regular meeting, the council heard from audience members.

Lanning explained the Master Drainage Plan Priority List that has 20 projects on it and gave a bit of history on it. It was adopted by the city council in 2008 with 12 projects listed. 

“Since that time, many of those projects have been completed,” Lanning said. “We try to complete one or two a year.”

In 2009, the council adopted a ranking system for the projects on the list. She pointed out the Moriarty detention pond was ranked third on the list. Design is under way now, and Lanning wants to get the project started this fall, if possible, and completed in 2020.

Evans lives on Tanbury Lane.

“In the five years I have lived on Tanbury Lane, we have had three storms over 5 inches of rain,” he said.

Evans pointed out Moriarty Park, where the detention pond would be, is uphill and won’t address the drainage problems in the areas south of it. Rainwater from Moriarty Park and water coming down 17th Avenue South all converge on a small area in an 18-inch pipe. That water combines with the water from the Windermere/Tanbury area to go into a “little pond” west of Tanbury and just north of 20th Street South.

“We need to make sure we have a robust design to be able to address this,” Evans said. “These two developments are connected together; we can’t get away from that. … We’re not the only place that are getting hit.”

Things can look great on paper, but it’s imperative to make sure it works “because many of us can not financially take this hit again. We can’t,” Evans said.

Evans said he was skeptical the plan would fix the problem, calling it “a Band-Aid solution.”

Matt Schmidt of Windermere Way had questions about the flow rate of water into and out of the pond and how the water will get over the road. He said the water problem has been going on for years, since at least 2014. 

Brink asked for clarification on whether the Moriarty Park detention pond listed in the Master Plan included a retaining wall. It does, Lanning said, adding the plan includes storm sewer inlets at the intersection of 17th Avenue South and Pebble Beach Drive and along Pebble Beach Drive, which would be collected in the pond.

“And it would be metered out slowly,” Lanning said.

Niemeyer said he was glad they had been able to come up with a plan and fit a pond in there without taking anything out of Moriarty Park. He asked if it would always have water in it.

“No, this is a dry mode pond,” Lanning said. “It won’t have standing cattails; it’ll all be mowed.”

Mayor Keith Corbett was absent; Bacon presided. Councilor Nick Wendell was absent for the study session, but present by phone for the regular meeting.

Contact Jodelle Greiner at [email protected]

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