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King County’s road and bridge network spans three
centuries
Just like keeping a vintage automobile in running condition or
preserving a classic historic building, King County knows “an ounce of
prevention is worth a pound of cure” when it comes to keeping the roads
and bridges in the unincorporated areas in good working order.
The inventory of roads and bridges maintained by the
King County Road Services
Division spans three centuries, and it takes constant
 maintenance
to keep the transportation network in the unincorporated areas
functional and efficient.
King County Road No. 1 – today’s Military Road – was established in
1854, and the last built-from-scratch county road was completed in 2003
when King County and Issaquah opened Highlands Drive north of Interstate
90. The county’s first bridge was built in 1867 and the newest one – the
Tolt Bridge replacement – will begin construction this week.
Some of these roads and bridges may be decades old, but they are
important links in the region’s transportation network. That is why
preventative maintenance is a top priority for the Roads Division.
“We have to preserve the existing the system because we can’t afford to
lose any of its usefulness,” says Road Services Division Director Linda
Dougherty. “We rely too much on our bridges and roads – both old and new
– to neglect any of them.”
In recent years, the King County Road Services Division has talked a lot
about preserving its aging infrastructure. But, just how old is this
infrastructure?
Some bridges near Redmond and Kent date back to 1913 and 1914. The old
culverts the county is currently replacing on
 Northeast
Cherry Valley Road are from the 1920s, made of clay, and are only 18
inches in diameter. Three years ago, Roads crews dug up Southeast 248th
Street in Maple Valley when the road began to crack and sink near Rock
Creek. They found a deteriorating wooden culvert under the surface that
was more than 100 years old.
One of the best examples of historic infrastructure is east of Redmond,
where the oldest bridges in King County are located on one of the oldest
roads. Two 93-year-old bridges spanning Evans Creek are on the
105-year-old Red Brick Road (196th Avenue Northeast), which still has a
surface of original and historic replacement bricks.
When both the old and new infrastructure is inventoried, the average age
of a bridge in unincorporated King County is 48 years; and the average
age of the surface pavement is 17.3 years. While the Roads Division
would like to lower those averages, staff are confident that the
county’s transportation network is safe and reliable for the traveling
public.
“Some of these roads and bridges are quite old, but still function very
efficiently,” said Dougherty. “It is a testament to how well-maintained
our county roads and bridges are.
 But,
it also creates a never-ending backlog of maintenance and preservation
work.”
A recent survey of pavement conditions of unincorporated roads shows
that 79 percent of the arterial and local-access roads are in
good-to-excellent condition. Only 10 percent fall into the
poor-to-substandard range.
The most recent annual bridge report shows that the “sufficiency rating”
– a numeric calculation that rates the bridge’s safety and
serviceability – has stayed consistent for the past several years.
Different repair programs, including seismic strengthening and
rehabilitation, ensure that the useful life of the current bridge
inventory is maximized. However, in some cases – such as the 84-year old
Tolt Bridge and the heavily traveled 75-year-old South Park Bridge – the
spans are reaching a point where they will soon be beyond repair and
must be replaced.
Because transportation funding has dwindled over the past decade, the
Roads Division places primary importance on preserving infrastructure
and supporting traffic and pedestrian safety. Dougherty says
preservation has to come ahead of adding capacity to the road system.
“In many of the unincorporated areas, where there is no existing street
grid, there are not a lot of alternative routes,” she said. “So the ones
that do exist are extremely critical, and are lifeline routes for local
residents. By investing in preservation projects, we keep our road
system safe and useable.”
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