Construction Beginning Soon on Mercer Stormwater Detention Basin

Harris County Flood Control District (HCFCD) will soon start building the new Mercer Stormwater Detention Basin, a large flood-risk reduction project along Cypress Creek adjacent to Mercer Botanical Gardens. HCFCD issued a notice to proceed to the contractor in December 2023 and the contractor is now mobilizing.

*The basin is north of FM-1960, east of the Hardy Toll Road, south of Cypress Creek and west of the Memorial Hills.*

Combined 512 Acre Feet in Two Basins

The Mercer Stormwater Detention Basin project will include the excavation of 512 acre-feet of soil and other materials from the site. Once complete, the $14.8 million dry-bottom stormwater detention basin will provide approximately 166.8 million gallons of stormwater storage during heavy rainfall events.

The U.S. Department of Housing and Urban Development’s Community Development Block Grant Disaster Recovery program provided a $15.4 million grant for the project. Another $9.7 million comes from the 2018 Bond Program.

Arrowstone Contracting, LLC received a $14,846,391 contract for construction. Land acquisition, engineering and administration will consume the rest of the budget.

The stormwater detention basin will include two separate compartments, north and south, with an equalizer pipe connecting them. An 54″ outfall pipe will also be constructed along the north compartment so stormwater can slowly flow back into Cypress Creek after storms pass.

Construction Caution

Contractors will access the work area via FM-1960 or Lazy Ravine Lane in the Memorial Hills Subdivision. The contractor may use heavy construction equipment such as dump trucks, excavators and bulldozers. Motorists should be aware of truck traffic when passing near construction access points and along truck routes.

The HUD Grant stipulates that construction needs to finish by Fall 2024. And construction is scheduled to take 348 days.

Reducing Backwater in Tributaries

This is among multiple stormwater detention basin projects the Flood Control District is developing in the Cypress Creek watershed.

A regional drainage study for the watershed found that flooding along tributaries of Cypress Creek is predominately caused by rising stormwater in Cypress Creek backing up into tributaries. Flooding is not caused by a lack of sufficient stormwater conveyance or drainage capacity on the tributaries themselves. Therefore, stormwater detention basins could be a beneficial project to reduce that backwater issue.

Project Benefits

The Mercer Basins will remove the 100-year area of inundation from 30 structures and the 500-year area of inundation from an additional 17 structures.

The project also includes a 30’ wide berm to accommodate maintenance and future recreational amenities.

The project avoids wetlands and will lower the water surface elevation by .35 feet during a 100-year storm event, according to HCFCD.

Upstream detention was one of three major prongs of the strategy to reduce flooding in the Lake Houston Area. This and every other little bit will help downstream.

The regional drainage study found here recommends nearly 25,000 acre-feet of additional stormwater detention in the Cypress Creek watershed. That would be enough to hold back the peak flow during Harvey for almost 5 hours. In lesser storms, the benefit would last even longer.

Posted by Bob Rehak on 1/2/24 based on information from HCFCD

2317 Days since Hurricane Harvey