New Regional Detention Area Prepares Olathe for Future Development

The City of Olathe, Kansas was having downstream flooding along Coffee Creek. To solve it, they decided to create a regional detention area near Lindenwood Dr. and Brougham Dr with funding assistance from the Johnson County Stormwater Management Program. In addition to managing the water, this project will also support future development in this rapidly changing area.

Affinis was selected by the city for the Lindenwood Dr. and Brougham Dr. Embankment Improvement project. We started by surveying the area. Property acquisition was an important component of this project. Our survey team researched the property maps, obtained ownership information, and when the improvements were determined, developed tract maps to support the project.

After the initial survey was complete, hydraulic modeling was performed to determine the exact improvements which would help meet the project goal. This led to the decision to construct two dams. One dam is at the future alignment of Lindenwood Dr., and the other is at the future alignment of Brougham Dr.

The Lindenwood Dr. dam is comprised of two box culverts, a 5’ x 4’ reinforced concrete box (RCB) and a 9’ x 5’ RCB. Our team provided stabilization basins at both box culverts and designed the embankment to provide for the future roadway on top of the dam. The Brougham Dr. dam has one box culvert that is 12’ x 11’ in size. As with the Lindenwood Dr. dam, the Brougham Dr. dam was designed so the dam embankment provides for the future roadway on top of the dam. By using the dam embankment for the future roadway, the city provided flood protection for these two future roadways, while also providing regional flooding relief.

This complex project required extensive agency coordination. We worked with the Federal Emergency Management Agency (FEMA) for the floodplain remapping, the United States Army Corps of Engineers (USACE) for the 404 Permit, the Kansas Department of Agriculture Division of Water Resources (KDA) for the two dam permits, and Johnson County Stormwater Management Program for funding assistance. We submitted plans and completed the USACE and KDA permit applications. For the dam permitting, we partnered with Water Resource Solutions to perform the dam breach analysis and inundation mapping.

Affinis also prepared emergency action plans for both dams. After a plan was in place, we submitted a Conditional Letter of Map Revision (CLOMR) to FEMA for their approval. Now that the project is constructed, we are submitting the Letter of Map Revision (LOMR) to FEMA for their final approval to revise the floodplain mapping in this area. These new dams should take several downstream properties out of the floodplain.

Our construction engineering group was also involved in the project. Because of the Kansas Department of Agriculture permitting, full construction observation was performed. At critical times during construction, our survey team provided as-built surveys for the dam permit closeout.

This project has helped move Olathe forward. Not only do these dams protect residents, they also support future development. The new regional detention basins will allow businesses and residents to move to this area with a smaller investment.