This report examines construction risk management as applied to Sound Transit's Capitol Hill Light Rail station, part of Seattle's University Link extension. It defines risk management within the construction industry and identifies the unique hazards that tunneling in Seattle's hilly, rain-prone environment presents. The paper focuses on the risk of soil settlement damaging the nearby Capitol Building, an unreinforced masonry structure situated unusually close to the tunnel route. It analyzes the probability and potential financial consequences of such damage, evaluates Sound Transit's risk reduction measures — including a concrete-grout wall and underground sensing devices — and concludes with recommendations for insurance coverage and contractor oversight procedures.
The paper demonstrates applied risk quantification: it pairs the probability of a hazard (soil settlement exceeding one inch) with its financial consequences (up to $4.8 million in property liability) to prioritize the risk and justify the cost of mitigation measures. This consequence-times-probability framework is a standard technique in construction risk management literature.
The paper opens with a conceptual definition of risk management, transitions into project background, and then follows the canonical risk management cycle — identification, analysis, response, and recommendation. Each stage builds on the previous one, ensuring that the final recommendations are traceable back to the specific hazards and data established earlier in the paper. The conclusion is prescriptive rather than merely summarizing, adding practical value.
Risk management is one of the most important and yet frequently overlooked areas of business management. Risk management is the identification, measurement, and control — at the most economical cost — of the hazards that can threaten the life, property, assets, and earnings of an organization. Risk analysis is the identification and assessment of the likelihood of hazards occurring and the consequences if they do occur.
In the construction industry, risk management takes on even greater significance. Construction, which consists of the manipulation of matter on the surface of the earth, presents unique hazards in the modern business world because of its clear impact on life and property. Construction activities, because of their substantial physical impact, often affect people and property in adverse and unexpected ways.
The City of Seattle is currently extending its Link Light Rail transit system from Downtown Seattle to the University District. This extension will run east of downtown Seattle to Capitol Hill before travelling north through the Montlake neighborhood to the University District. Because it will run through four different residential neighborhoods, the extension requires the construction of three new light rail stations: Capitol Hill, Montlake, and Wallingford.
University Link is a 3.15-mile light rail extension that will run in twin-bored tunnels from Downtown Seattle north to the University of Washington, with stations at Capitol Hill and on the University of Washington campus near Husky Stadium. University Link construction is being funded by a combination of federal grants, motor vehicle excise tax (MVET), and a local sales tax of 0.4%. The total cost for University Link is $1.9 billion. Construction began on the two stations and tunnel track in 2009 and is expected to continue for seven years, with University Link scheduled to open for service in 2016.
During the excavation phase, the contractor grades the site to make it level and begins digging out the area for the station. The excavation for the station is approximately 400 feet long, 100 feet wide, and 60 feet deep. Once the excavation reaches the bottom of the station — approximately 60 feet down — a concrete slab 10 feet thick is poured at the base of the excavation.
After the concrete slab is poured, excavation of the two tunnels to Pine Street begins. A single tunnel boring machine (TBM) is launched from the bottom of the station excavation. The TBM is scheduled to excavate an average of 40 feet of tunnel per day. As it bores through the ground, the TBM simultaneously places the concrete rings that form the exterior surface of the tunnel. Excavated dirt travels through the machine onto a conveyance system that carries it back to the surface to be hauled away.
When the TBM reaches Pine Street, it is disassembled and transported back to the station site, where it is reassembled to dig the second tunnel between Capitol Hill and Pine Street. Tunneling proceeds in this direction because there is insufficient room at Pine Street for all the equipment needed to extract the excavated material.
Sound Transit has already completed demolition and environmental remediation for the project. It held public presentations and comment meetings both before and after demolition. Following demolition, Sound Transit conducted an environmental survey to record any unexpected changes to the environment not accounted for in the original University Link construction plan, particularly with respect to soil conditions. Property owners were also given the opportunity to raise concerns or problems related to the University Link construction project at the public comment meetings.
Risks in construction can be physical, consequential, social, legal, political, financial, and technical. They can arise from outside the company — as with natural hazards or the activities of suppliers — from within the company, as with accidents or physical damage, or they can be transmitted from the company outward, as with environmental damage or injury resulting from the company's products or negligence.
Sound Transit's previous tunneling work on the Beacon Hill Light Rail station revealed the hazards of tunneling in Seattle. Seattle's geography and climate — extremely hilly terrain with frequent rainfall — make tunneling far more problematic than in other American cities such as New York City or Boston. The soil is soft and its composition often changes dramatically over short distances. During previous tunneling projects, soil or the water table has shifted, causing buildings above to sink. In one instance, it cost $4 million to investigate and fill several voids, one of which nearly swallowed a house. In the Beacon Hill Station dispute, Sound Transit recouped that cost by withholding it from final payment to the contractor.
Seattle's boring and tunneling activities can disrupt the foundations of existing buildings throughout the city, obligating Sound Transit to compensate residents for property damage. This risk is heightened by the relatively shallow tunnel depth in certain sections of the project — the tunnels run only 45 feet below the Capitol Building, which houses apartments. Because the Capitol Building is constructed of unreinforced masonry, even a settlement of less than one inch could crack it down the middle where the tunnel passes under the building's east side. If the Capitol Building is damaged, Sound Transit's insurance or funds held within the construction budget would be used to pay for repairs.
Always verify citation format against your institution’s current style guide requirements.