Westchase District’s largest ever capital improvement project is underway on Walnut Bend Lane. Workers are rebuilding nearly 6,000 feet of the roadway between Westpark Drive and Westheimer Road. The project scope includes some features that everyone will see and enjoy including enhanced sidewalks, pedestrian lighting, dedicated bike lanes, custom bus shelters, bike racks and extensive landscaping. But some of the most impressive improvements are the ones you won’t see.
Walnut Bend Lane was built in the mid-1970s. Some years ago, Westchase District considered resurfacing the street to address failing concrete, shifting panels and uneven sidewalks. “Once we delved into the project, engineers discovered larger issues with underground water and sewer lines in dire need of repairs,” said Irma Sanchez, Westchase District’s vice president of projects.
Any roadway built two and three decades ago doesn’t meet current criteria, which means the engineers designing the project start at ground zero. “You only get one chance to tear up the road and make it right,” said Ricky Gonzalez, of the engineering firm Lockwood, Andrews and Newnam (LAN), which designed the new roadway.
“These retrofit projects tend to be really challenging,” added Matt Manges, LAN’s project leader, stormwater. “First we try to understand the historic issues. Is there a history of flooding? Are there resident complaints. Are there City of Houston issues? We want to resolve historical issues and bring it up to current design standards.”
Through all the recent “rain events,” businesses and apartment communities along Walnut Bend had not reported any structural flooding. But engineers knew they had an opportunity to reduce the flood risk along the roadway.
Unlike a new greenfield development, where a detention pond would be built to accommodate runoff, Walnut Bend is being re-built using existing right-of-way. “When you’re not expanding the roadway, you have to make do with what you have. You can’t take the problem and send it somewhere else,” said Manges.
“You have to get the water into the inlets and get it quickly off the roadway,” said Gonzalez. “You have to store it somewhere while the water in the channel recedes. We can’t store it on the ground, so we store it underground. It’s called underground storage or inline detention.”
The secret is underground
Manges and his fellow engineers at LAN used sophisticated hydraulic modeling software to analyze current conditions and evaluate future rain and drainage conditions. They recommended the installation of reinforced concrete pipes. These giant concrete pipes, ranging in size from 18-inches by 60-inches to 10-feet by 6-feet, are buried underground. They’re designed to hold the water until it can be drained into the appropriate channel.
A lot goes into the analysis and modeling to make sure there is no adverse effect downstream, said Manges. “You take out the old pipe, put in the new bigger pipe and put in a restrictor at the downstream end so you don’t send that problem somewhere else. You can’t send more water downstream than you were before.”
Right now, underground utilities are being moved to make way for the new reinforced concrete pipe. For the team at Westchase District-based LAN, it’s rewarding to see their plans moving into the construction phase. Approximately eight LAN engineers, CAD drafters and constructability review professionals worked 18 months to design the project.
Gonzalez is most excited about the new pavement and the mobility improvements. “When the concrete paving is installed correctly, it should last 50 years. Plus, we’re adding bike lanes and wider sidewalks. We’re replacing driveways, utilities, everything. The quality of life on Walnut Bend will be drastically improved,” said Gonzalez.
The District’s 380 Program with the City of Houston covers about $4.4 million of the $20 million project. Houston Public Works has contributed another $4.6 million and funding from the Federal Highway Administration covers the rest of the project. The Texas Department of Transportation is overseeing the construction process, which is expected to be complete in the summer of 2021.