Mercer Basin

Giant Mercer Basin on Cypress Creek Aiming for Completion This Fall

July 22 2024 – Harris County Flood Control District (HCFCD) still aims to complete the giant Mercer Stormwater Detention Basin between FM1960 and Cypress Creek just East of the Hardy Toll Road before the end of this year.

Pictures taken 7/22/24 Show Progress

Looking S toward FM1960 from over Mercer Basin. Hardy Toll Road cuts through upper right of frame.
Reverse angle looking N toward Cypress Creek in trees just north of the northern basin.
Looking West toward Hardy Toll Road at Southern Basin. FM1960 in upper left.

Compare these pictures of the Mercer Basin in February this year when clearing and construction was just getting started.

Fighting the Elements

All things considered – January floods, a derecho, May floods and Hurricane Beryl – contractors seem to be making good progress. Especially if you consider that I’ve already recorded 57 inches of rain in my gage in the first six and a half months of this year – more than we usually get in a full year.

How Big is It?

The Mercer Site covers 58 acres. It will contain twin, connected, dry-bottom basins totaling 512 acre feet.

One acre roughly equals the size of a football field without end zones. So, 512 acre feet would cover an area that large to a depth of 512 feet. That’s approximately the height of Two Allen Center downtown.

Of course, the basin won’t be 512 feet deep. It will likely be around 8 to 10 feet deep because it covers 58 acres minus room for maintenance roads.

History of Project

Harris County finalized acquisition of the property in August 2023. A $15.4 million grant obtained from the U.S. Department of Housing and Urban Development (HUD) in 2018 stipulates completion before the end of this year.

Additional funding comes from the 2018 Bond Program, which was approved by Harris County voters on August 25, 2018.

Layout and Location

The two maps below show the layout and location of the project.

Mercer Stormwater Detention Basin
HCFCD map of Mercer project
Mercer location
Mercer is about 8 miles upstream from the US59 bridge over the West Fork.

Cypress Creek joins Spring Creek before reaching US59.

Construction Details

Features include:

  • Concrete box culverts will equalize water levels between the two compartments. And a spillway will connect the northern basin to Cypress Creek.
  • A 54” outfall pipe will move water from the basin into Cypress Creek.
  • A 30’ wide berm will accommodate maintenance and future recreational amenities.

Part of a Bigger Solution

Mercer is one of several stormwater detention basin projects HCFCD is developing in the Cypress Creek watershed.

A regional drainage study for the watershed found that rising floodwaters in Cypress Creek back water up into tributaries and cause flooding there. The tributaries have sufficient stormwater conveyance or drainage capacity. Therefore, stormwater detention basins can help reduce the backwater issue.

The regional drainage study described here recommends nearly 25,000 acre-feet of additional stormwater detention in the watershed.

Mercer by itself won’t help the Lake Houston Area much in a major flood. It’s designed to help primarily homes and businesses in the area which you can see in the photos above.

But every little bit helps.

Posted by Bob Rehak on 7/22/2024

2519 Days since Hurricane Harvey