Lake Hills / NW Lake Sammamish Sewer Upgrade
This is an upgrade of 4.5 miles of sewer pipes in
Redmond to provide service for 50+ years. The sewer
line eventually leads to the Brightwater Treatment
Plant. But this project only covers the southernmost
4.5 miles of the regional line, which ends at the
Bellevue city line.
As such, it passes along the west edge of Marymoor
Park. The new alignment mostly follows the existing
alignment, though there is a small section where the
existing line runs along the river, and it will be
shifted west to the trail along the east edge of West
Lake Sammamish like the rest.
Construction to start mid-2021 (bid early 2021). 3
year construction duration.
For the most part, the new line will be installed next
to the existing pipe. Later the existing pipe will be
decommissioned, but usually not removed.
For the most part, the new pipe will be installed by
trenching. However, where the line passes under the
Sammamish River, and where it passes under Marymoor Way
at the west entrance to the park, they will use
trenchless tunneling to install the line.
Work will be during normal daylight hours; Redmond will
dictate available construction times. Construction will
be year-round, but certain stretches will probably have
to be done during the dry season. This is especially
likely along the Sammamish River. Some temporary road
closures will be required. Lane closures, reduced speed
limits, and congestion are expected. Neighbors have
A 35’ x 40’ wide strip will need to be cleared in order
to install the piping. (Small) trees will be planted to
replace those cut, at ratios determined by the various
Michael asked whether tunneling just south of Marymoor
Way will allow some of the trees just SE of the
intersection to be saved. Kelly said she’d ask about
Natasha asked whether cottonwoods that are removed would
be replaced by new cottonwoods, or different species.
Changes in species change the habitat for birds and
animals. Natasha and Norah expressed interest in seeing
the planting plan, at least for Segment 3 (which runs
past the park).
Sammamish River Trail – for a lot of this project, the
pipe will be installed under the trail. This means
there will be significant trail closures, due to limited
space and access points. So off-site detour routes are
being defined; some of them are very lengthy. Laura
asked to make sure there are trail signs informing them
of future closures.
Trail detours: The worst is that pedestrians will not
have a route between Marymoor Way and Leary Way for as
much as a year. The “detour” for pedestrians would be
about 6 times larger, running all the way through
Marymoor to the East Lake Sammamish Trail, then
northwest to connect to the trail along Bear Creek
Parkway. However, there will be sidewalk work done
along the north edge of Marymoor Way from WLSP to the
Marymoor Connector Trail. Natasha requested a safe
crosswalk from the north side of the road to the mansion
area. Kelley and Norah both mentioned that a lot of the
necessary improvements would be the responsibility of
Norah asked about the possibility of a pedestrian
shuttle. Or a Metro bus route?
Michael suggested using the trail that runs north of
Marymoor Way on the east side of the Sammamish River,
with a Bailey Bridge over Bear Creek – BUT that route
will be used by Sound Transit for construction of the ST
line to Redmond during the same time period.
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