Houston Public Works’ Northeast Transmission Line Takes Shape
By Christine Kirby and Kevin Tran
Things are indeed bigger in Texas. And Houston’s Northeast Transmission Line is no exception. After a decade of astonishing 21.6 percent population growth, the Houston region is expected to double its current population by 2050. To keep up with projected water demands, and in response to the Harris-Galveston Subsidence District mandate to reduce groundwater pumping along the Texas coastal region, the City of Houston partnered with regional water authorities to build the Northeast Transmission Line (NETL).
The NETL program, Houston’s largest water transmission program yet, is full steam ahead. The project will convey 365 MGD of treated surface water from the newly expanded Northeast Water Purification Plant (NEWPP) through 16.5 miles of primarily 108-inch steel water line from Lake Houston to west of IH-45 with various take-points and interconnections along the way. The water line will also provide redundancy for areas serviced by the existing 66-inch waterline along the Greens Road corridor.
“Houston Public Works is integrating multiple segments into one massive pipeline. Once complete, the City will be able to increase surface water usage to help minimize subsidence and flooding,” said Panduranga P.K. Kuruva, P.E., managing engineer for Houston’s surface water program. “Increasing water capacity is vital to meet Houston’s growing demand.”
By the Numbers
Houston Public Works divided the 16.5 miles into 13 construction contracts. With most of the line being 108-inch diameter, the projects also included 120-inch, 96-inch, 84-inch, 66-inch, 54-inch and 42-inch diameter interconnections. All 16.5 miles of steel water line was manufactured in Texas factories with more than 21,700 metric tons of domestically sourced steel coil. The total construction cost is nearly $450 million, with 26 large diameter isolation valves, more than 17,000 linear feet of tunnels, and over 100 easement parcels. Once the Northeast Water Purification Plant (NEWPP) Expansion is completed, the NETL will serve more than 900,000 homes in Harris County.
“A project of this magnitude required years of planning and extensive collaboration,” said Mackrena Ramos, P.E., vice president at Lockwood, Andrews & Newnam, Inc. (LAN), a national planning, engineering and program management firm that is serving as the technical advisor. “Just the sheer size of the project makes it unique, but the number of individuals it took to make it a reality is quite amazing. From the City team to their partners, engineers, utility coordinators, manufacturers, and contractors’ workforce, we all had a vested interest to meet the water needs of Texans.”
For a project of this scale, challenges of equal magnitude were faced throughout the design and construction process.
The 13 segments were organized in three phases, known as the eastern projects, the western projects, and the “workaround solution”. The workaround solution – three projects which fell in the middle of the alignment – was designed and built first as it could be placed in service with interconnections to the existing system on each end. This created a long bypass for a segment of the existing 66-inch water transmission main along the Greens Road corridor. The first of the projects began construction on summer 2018, and the workaround solution was placed in service by fall 2020. The City was able to isolate part of the existing 66-inch main for condition assessment and rehabilitation, all while the eastern and western segments were still in construction. By the spring of 2021, a much-needed repair was successfully completed on the existing 66-inch water line, which is a major source of water for the City and surrounding areas, including George Bush Intercontinental Airport.
“The internal repair of the existing 66-inch main was crucial to restoring service to an essential line within the NEWPP service area. The interconnection between the 108-inch and 66-inch was on the critical path during design and construction. Now complete, the interconnect and repair provide operational flexibility and longevity to the two systems,” said Ramos.
Part of the workaround solution included a 1,163-foot tunnel under IH-69 at Aldine Bender Road. The freeway consists of 15 elevated main lanes and eight frontage road lanes at this crossing location. The tunnel alignment stretched between bridge columns, and soil conditions included fine sand and silty sand under the groundwater table. Harper Brothers Construction, LLC procured an earth pressure balance machine (EPBM) and successfully completed the tunnel between January to March 2020.
Another challenging aspect of this large-scale waterline project was construction staging and access within an urbanized area. Easements ranged in width from 50 feet to 90 feet, with many of the parcels on developed land. Existing utilities, surface features such as driveways, parking lots, trees, landscaping, and monument signs were within close proximity to the proposed construction work. Contractors needed every inch of space for equipment and material staging, and this was a major consideration during the design phase. Design engineers identified conflicts and worked with private utility owners to relocate overhead and buried utilities to make way for construction. Relocations of easement encroachments, such as monument signs, landscaping and fences, were identified by the design engineer and coordinated through the City in advance of construction.
The City’s public engagement team’s primary goal is to engage, educate, and inform the community. They conducted community meetings to provide information to residents and business owners for the upcoming construction work. The meetings, held after the contractor was selected but before construction work began, allowed attendees to interface directly with the design team and contractor’s representatives.
“Transparency is key for any large project like this. Houston Public Works relies on the community’s support to ensure success throughout construction and implementation,” said Kenya Williams, public engagement team for Capital Projects. “Our engagement team made sure to address any challenges and concerns before construction began.”
Each standard 40-foot-long pipe segment, weighing 35,000 pounds, arrived on site on an 18-wheeler truck. Once the pipe arrived, it was offloaded in a location as close as possible so that the excavator could reach it without having to travel a long distance. To lift and move this pipe, a 70 metric-ton excavator was needed. Harper Brothers Construction used a Hitachi 870, a slightly larger tracked excavator, to perform the double duty of lifting the pipe and excavating a deeper trench. Stabilized construction roads were built within easement areas so that 18-wheelers, dump trucks and other vehicles could enter and exit the job site. Where pipe and materials could not be stored on site, a secondary laydown area was used.
“One of the biggest challenges with construction projects in urban or semi-urban settings is the logistics. To overcome the space constraints on site, we had to have a thorough site plan. We staged our materials in a way that allowed for fluid movement of the crew through the line. The key to a successful project is a solid plan,” said Jon Harper, CEO of Harper Brothers Construction, LLC.
When the COVID-19 pandemic struck the Houston area in March 2020, quick thinking was needed on the part of the City’s team. Two of the western projects had advertised for bids, but the mandatory pre-construction meeting had not yet been held. There was no room for delay, so the team quickly converted the meetings to a virtual format, and attendees were able to call in by phone or log in through a computer. Monthly progress meetings were converted to a virtual format as well and are still being conducted this way today. Safety of the field crews and support staff, all considered as essential workers, were of the utmost priority. Face coverings and hand sanitizer were provided, along with implementing social distancing and contact tracing for crews. Teams quickly adapted to new restrictions and safety protocols, and field activities never missed a beat.
“For the NETL project, all the materials were local and made in Texas. Therefore, we didn’t have major delays. We were fortunate that we did not have any severe cases in our workforce,” said Harper.
On February 15, 2021, temperatures across the state plunged into record-setting, sub-freezing conditions, resulting in widescale electricity outages that lasted for several days. In a matter of hours, chemical plants along the Texas Gulf Coast underwent swift unplanned shutdowns, disrupting global supply chains, and triggering a shortage of raw materials, including polypropylene and polyethylene. As a result, a shortage of materials such as PVC pipe and protective coatings for pipelines is looming over the NETL and the construction industry. So far, manufacturers and suppliers have met commitments, but impacts from the Texas freeze will be felt for months to come.
Where We Are, and Where We’re Going
To date, seven segments have been completed and placed in service. Six segments are currently in construction, and the entire NETL is expected to be completed by late 2022.
“The Northeast Transmission Line is more than ten years in the making and will be the largest water line for the City of Houston,” says Kuruva. “Our purpose is ‘Together we create a strong foundation for Houston to thrive’ and the Northeast Transmission Line embodies our goal for improved water service across the area.”
Houston’s legacy continues with its trail-blazing water infrastructure expansion initiatives. Thanks to these initiatives, the City of Houston’s drinking water system maintains a “Superior” rating, the highest rating for water quality issued by the Texas Commission on Environmental Quality.
Christine Kirby, P.E. is a senior associate and senior project manager at Lockwood, Andrews & Newnam, Inc. (LAN), a national planning, engineering and program management firm. She can be reached at firstname.lastname@example.org.
Kevin Tran, P.E. is a supervising engineer and NETL team lead at City of Houston Public Works, Capital Projects, Facilities Delivery Line, Surface Water Transmission Program. He can be reached at email@example.com.