Coppell Set to Spend $1 Million Designing Two Drainage Fixes Expected to Cost $3.5 Million

The Coppell City Council is set to approve just over $1 million in engineering design work Tuesday for two drainage projects. City staff expect those projects to cost about $3.5 million more to build.

Both contracts go to LJA Engineering, Inc. and are on the consent agenda for the council's Oct. 27 meeting, according to the posted agenda. Consent items are normally approved together in one vote unless a council member asks to pull one for discussion. The regular session begins at 7:30 p.m. at Town Center, 255 E. Parkway Blvd. Both contracts would be paid from the city's Drainage Utility District Fund.

$249,800 to design a fix on Winding Hollow Lane

The smaller contract, for $249,800, targets flooding on Winding Hollow Lane. A memo from Public Works Director Mike Garza and Assistant Director Aaron Tainter says the owner of the home at 202 Winding Hollow Lane "has reported flooding originating from the roadway." The house sits along the Cottonwood Branch floodplain next to a 72-inch storm drain outfall at a sharp bend in the channel.

LJA would build a computer model of the storm drains serving the intersection of Winding Hollow Lane and Burning Tree Lane. It would then study two options: realigning the 72-inch storm drain between 200 and 202 Winding Hollow, or building a diversion with an outlet farther downstream. The goal, according to the memo, is to cut street ponding during a 100-year storm and "eliminate flooding from the roadway onto adjacent property."

According to the firm's proposal, the largest line item is $92,000 for the stormwater model. The proposal assumes six months of design. The memo puts the expected construction cost at $1 million.

Bethel Cemetery in Coppell, 2012. The photo is shown for context. Photo: Nicolas Henderson / Wikimedia Commons, CC BY 2.0.

$757,500 for an eroding creek

The larger contract, for $757,500, covers about 1,600 feet of an unnamed tributary to Grapevine Creek. The stretch lies west of South Denton Tap Road beside the Grand Cove Estates subdivision and runs from West Bethel School Road down to where the tributary meets Grapevine Creek. The city's memo says ongoing erosion threatens sewer and storm drain lines near the channel. It says stabilization "is needed to protect this infrastructure from further erosion and potential damage."

The firm's proposal breaks the fee into more than two dozen tasks. The biggest are:

• $127,000 for preliminary design

• $74,500 for conceptual design

• $67,000 to update a stream assessment

• $60,000 for surveying

• $47,500 for geotechnical work

The fee also covers wetland, endangered species and archeological reviews, an Army Corps of Engineers permit application and a $6,000 structural check of an existing gabion wall. The design is expected to take 12 months, with eight more months for bidding and construction support. The memo puts construction at about $2.5 million and says the design will use "nature-based solutions where existing development allows."

Both memos say LJA was chosen through a qualifications-based process and has designed earlier projects for the city.

Coppell police take over a half-mile of toll road

Also on the consent agenda is an agreement with the North Texas Tollway Authority for Coppell police to patrol the roughly half-mile of the Sam Rayburn Tollway, Highway 121, inside the city. Police Chief Danny Barton's memo says the Department of Public Safety used to handle that stretch, but its agreement with the toll authority has ended. Under the new deal, the authority would pay Coppell $110,302 a year.

The bigger picture

Paying an engineer $249,800 to design what is expected to be a $1 million fix may draw questions when the memo names a single home. To be fair, the city also describes the work as improving the neighborhood's storm drain system and cutting street ponding. Drainage problems rarely stay on one lot, and a channel eating toward a sewer line is no small thing either.

Still, these two designs alone would commit Coppell's drainage fund to some $4.5 million in total cost once the projects are built. Residents have a right to see that kind of money discussed in the open, not just approved in a consent vote.

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