Facility improvements result in bettering citizens’ lives and a smaller environmental impact.
Water equals life, and now with droughts and the coronavirus pandemic we need access to clean water more than ever. Wastewater treatment facilities are essential infrastructure that support life on Earth. They help brining clean water to our homes, and help us stay clean. People could live without electricity, but would not survive long without clean water, which is why expansion of the Dallas Salmon Wastewater Treatment Plan was an important investment.
The Dallas Salmon Wastewater Treatment Plant is an award-winning American Public Works Association Texas Chapter Environmental Project of the Year 2019. It is one of the two wastewater treatment plants in a friendly city of League City of Houston metropolitan area.
In 2014, in response to new discharge permit constraints issued by the Texas Commission on Environmental Quality (TCEQ), the City of League City was informed that the outfall for the effluent line of the Dallas Salmon Wastewater Treatment Plant (DSWWTP) would need to be moved from its existing location. Due to updated copper and zinc discharge limits, the outfall needed to be moved further downstream in order to discharge into a wider water stream, requiring the City to build an entirely new effluent line and outfall location.
The existing outfall was located on a small and narrow tributary of Clear Creek river, which had become too narrow with the new effluent limits, and had to be moved into a wider spot. The project team of Jones|Carter was tasked with finding the most economical alignment for relocating the affluent line to the outfall at Clear Creek to satisfy the TCEQ requirements. The design commenced in February 2016, new outfall was required by the TCEQ to be operational by September 2018 per the discharge permit mandate, so the design had to be expedited. Ultimately, it was finished a month ahead, in August 2018. The expansion of this facility broadened its capacity from 7.5 million gallons per day to 12 million gallons per day.
Jones|Carter design team, which included Water, Hydrology & Hydraulics, Transportation and Surveying practices,
was supported by a strong group of dedicated consultants, among others of Ardurra Group (Structural, WWTP Hydraulics, Permitting), Terracon (Geotechnical), Ecologic (Environmental) and C.N. Koehl (Urban Forestry). The League City team and the contractor, SER Construction, were also instrumental in the success and delivery of this project.
Preserving the historic feel
One of the goals of the construction was to preserve the historic district feel of the neighborhood of League City.
“It was evident early on the project would require a great
deal of coordination with the nearby neighborhood, which consisted of a residential historic district,” said David Warner, Senior Project Manager at Jones|Carter. In order to do that the Jones|Carter team worked extensively with the city staff to develop options, which were then presented at a public meeting attended by residents within the historic district and consulted with them. The comments received from the public
were incorporated into the project. This was achieved through the design of a roadway section that accommodated the historic oaks and the open ditch drainage in the neighborhood.
“During the preliminary design and selection of the recommended outfall alignment, we discovered many conflicts with existing utilities, drainage features, roadway, and wetlands,” Warner said. In order to mitigate those conflicts, the team diverted the existing drainage features to a parallel storm sewer outfall adjacent to the proposed effluent outfall.
With parallel outfalls required, a large portion of North Kansas Avenue required pavement replacement. The team recommended the addition of the roadway reconstruction to the project, which was already slated in a future Capital Improvement Plan. Combining the effluent, storm sewer, and roadway work ultimately saved the city significant construction dollars. The team also minimized the impacts to the existing wetlands by reducing the construction footprint through those areas and securing a permit from the U.S. Army Corps of Engineers.
Doing what is best for citizens and the environment
When it comes to doing what is best for citizens and environment, the team combined the outfalls for the effluent line and storm sewer outfall into one structure, in lieu of separate outfalls, resulting in a single environmental impact to Clear Creek. The decision was made to revise the design from a circular pipe to reinforced concrete box culverts (RCBCs) to minimize depth of cover requirements and to aid in lowering the hydraulic grade line from Clear Creek to DSWWTP. Finally, the team opted for an asphalt roadway with natural roadside ditches along North Kansas Avenue to help preserve the historic feel and many of the historic oak trees along the alignment.
The team installed 1,500 linear feet of 9’x6’ and 8’X5’ reinforced concrete boxes from the existing discharge structure at the DSWWTP to a new outfall location at the north end of N. Kansas Avenue at Clear Creek. Due to its size and location, the combined outfall structure has since been turned into a fishing dock for the community to enjoy.
“Everyone on our team did their piece of the job,” said Kyle Kaspar, Manager of the Conveyance & Transmission team at Jones|Carter. “But it’s the fact everyone came together to do a great job for the City of League City that made it an award- winning project for both the client and Jones|Carter.”
Dominika Kowalska is the Assistant Editor for American Infrastructure Magazine. She can be reached at firstname.lastname@example.org.