HNTB on Lynnwood Link
Lynnwood Link Extension under construction in 2020. Image courtesy of Sound Transit.Ahead of the opening of the Lynnwood Link Extension, HNTB offered to participate in an interview with the Seattle Transit Blog discussing their work on the project.
HNTB is an employee-owned infrastructure design firm with offices in downtown Seattle, Bellevue, and many other cities nationwide. They provided engineering design and construction oversight of the Lynnwood Link Extension throughout the life of the project and have worked on almost every major Sound Transit project since they won their first contract from the agency in 1998.
Although HNTB was unable to join the blog for a live interview before the extension opened, they provided written responses to our questions. The following are HNTB's unedited responses to my questions:
- Are there any subtle or easily overlooked aspects of HNTB's design of the Lynnwood Link Extension that you'd like to highlight for us?
Managing a large multi-disciplinary team can often be overlooked or underappreciated. HNTB managed a team of 38 sub-consultants comprising hundreds of design professionals. The General Contractor/Construction Manager delivery method also provided the opportunity to connect the design and construction teams during the design, enabling the HNTB team to identify and incorporate innovative ideas that helped achieve the project objectives.
Sound Transit established a collaborative work environment that offered the design and construction teams, for both Civil and Systems contracts, a seat at the table working together to deliver the best project possible. HNTB supported this culture of collaboration through a partnering strategy that allowed the project teams to understand and work towards achieving the project goals.
- Could you discuss an example of how HNTB has been able to leverage its experience on previous Sound Transit projects to improve its work product on Lynnwood Link and future Link expansions currently in early design stages?
HNTB's extensive experience working on previous Sound Transit projects has significantly enhanced our approach to the Lynnwood Link Extension and other Link expansions in the early design stages. The Lynnwood Link design team members capitalized on their most recent experience completing the final design of the East Link Extension. We adapted many of the proven successful strategies and implemented all applicable lessons learned during our delivery of the Lynnwood Link project. For example, we worked successfully with the East Link Segment A civil consultant, the systems consultant, E335 GC/CM Contractor, and the CMC to coordinate design interfaces, develop and review cost estimates, and evaluate value engineering ideas. We implemented a similar approach on Lynnwood Link, and we ensured that the project benefited from value engineering, constructability reviews and cost-saving measures throughout the life of the project. This depth of knowledge and expertise ensures that we deliver efficient and scalable solutions for future expansions, ultimately enhancing overall system performance and sustainability.
- Earlier Link projects used a form of box girder or tub girder designs for elevated superstructures,but it appears I"-shaped girders were predominantly used for elevated sections of Lynnwood Link. Could you explain when and why the decision was made to use a different girder design, and what lessons HNTB learned from this change?
The decision to use I'-shaped girders for the elevated sections of the Lynnwood Link Extension was made post-60% design as part of our efforts to balance cost-efficiency, constructability, and aesthetic considerations. Compared to the box girder or tub girder designs used in earlier Link projects, I'-shaped girders offered a more cost-effective design while maintaining the necessary structural integrity. To maintain similar aesthetics to other Sound Transit Stations, we utilized tub girders for the exterior girders and I'-shaped girders for the less visible interior. By opting for I'-shaped girders for the rest of the elevated structures, we were able to reduce material costs and simplify construction logistics. This change has provided valuable insights into how we can approach future projects with a focus on adaptability and efficiency without compromising on the quality and durability of the elevated structures.
- What challenges did HNTB face when designing and starting construction on the 130th Street Station after its approval in 2016, and were there any unusual or innovative solutions HNTB employed to overcome these challenges?
When designing the 130th Street Station, we saw several opportunities to enhance the station's integration into the broader light rail network and future-proof its functionality for the growing area. One key opportunity was designing a station that could serve as a vital connection point for surrounding neighborhoods, improving pedestrian and bicycle access while ensuring seamless transit links. Additionally, the station's placement offered us the chance to promote sustainable urban growth by encouraging transit-oriented development.
To capitalize on these opportunities, HNTB employed innovative solutions, including advanced 3D modeling and simulation tools to optimize the station's design. We also incorporated green infrastructure and energy-efficient systems to support the long-term sustainability of the station. By collaborating closely with community stakeholders, we were able to create a design that not only meets the region's transit needs but also enhances the surrounding neighborhoods and promotes smart growth.
Romson Bustillo, a Seattle-based artist, is working on creating an inviting and optimistic atmosphere for the 130th Street Station. His art guides passengers through the station with patterned iconography on the walls and a welcoming painted column at the south entrance. The service building will feature a 100-foot-long mural by Bustillo, inspired by the local neighborhood.
HNTB worked on repackaging the design of the 130th Street Station finishes to be bid separately as a design-bid-build project. The design repackaging effort required seamless coordination among the various disciplines and at the interface points with the construction completed by the GCCM Contractor. The HNTB design team skillfully fulfilled the City of Seattle permitting process to produce the repackaged construction documents and ensure their readiness for bidding. This resulted in a more competitive price and a total saving of $30M on the $100M station.
- Much of the Lynnwood Link Extension runs parallel to Interstate 5 and even crosses over the freeway north of Mountlake Terrace Station. What challenges or opportunities are presented by building along the right-of-way of a state-owned freeway?
HNTB understood that right-of-way parcel identification and acquisition are critical to delivering the Lynnwood Link Extension. Early during the final design, we held technical sessions stressing the need to identify right-of-way needs early since nearly all aspects of the design will be impacted by parcel acquisition. We supported Sound Transit during the required right-of-way negotiations with WSDOT, several cities, parks, schools, private businesses, and private residences. Meeting the project schedule required a well-coordinated and detailed strategy to expedite right-of-way acquisition. Our team utilized proven approaches at 30%, 60% and 90% design to streamline the right-of-way process and allow for early certification of property acquisition.
HNTB utilized the project alignment established during the preliminary design as a good starting point and looked for opportunities to reduce right-of-way acquisition costs and impacts on the public during the final design. For example, we shifted the I-5 guideway crossing over the freeway in Mountlake Terrace slightly to the north to reduce the impacts on the existing Mountlake Terrace freeway station during construction. This alignment shift allowed the freeway station to remain operational during most of the construction and allowed for the use of a more conventional structural guideway type, which resulted in significant cost savings for the project.
- How could construction using concrete and other carbon-intensive materials be made more sustainable (i.e. produce fewer carbon emissions) on future Sound Transit projects? What, if any, do you think are the major barriers to using more sustainable constructionmaterialsin Western Washington?
Light rail projects significantly reduce the carbon footprint by encouraging the public to use public transportation instead of driving their personal cars. This is especially effective when coupled with transit developments that promote walking and cycling access to light rail stations. We're committed to supporting sustainable construction practices through innovative design. We're committed to working closely with Sound Transit to ensure our designs align with their sustainability goals and support them in leading the region toward more eco-friendly infrastructure solutions.
- How has Goran Sparrman'sdeparture from HNTB to work as interim CEO of Sound Transit affected HNTB's relationship with Sound Transit?
We appreciate our ongoing partnership with Sound Transit and remain focused on delivering successful outcomes for its projects. Our team continues to collaborate closely to support Sound Transit's mission and objectives.
Responses are attributed to Moein El-Aarag, Group Director and Associate Vice President at HNTB.