Infrastructure

I-405, I-5, and SR 4 Work Continues Through Labor Day

Sunday, August 30, 2026

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I-405, I-5, and State Route 4 will see lane closures and detours through early September for construction projects, according to Washington State Department of Transportation (WSDOT) records.

WSDOT plans to close up to two southbound lanes of I-405 from milepost 12 to Coal Creek Parkway Southeast from 9 p.m. Thursday, Sept. 3, to 5 a.m. Friday, Sept. 4. I-5 will have single-lane reductions nightly from 8 p.m. to 5 a.m. near Alger/Lake Samish Road (exit 240) through Sept. 4. State Route 4 will close a single lane between 50th and 42nd Avenues weekdays from 7:30 a.m. to 5 p.m. until Sept. 11.

WSDOT notes these closures are for fish passage construction on I-5, utility work on I-405, and buried gas main extension on SR 4. The department advises drivers to expect delays and follow flagger instructions through work zones.

📄 Source: WSDOT — Highway Construction & Closures — https://wsdot.wa.gov/travel/road-construction

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I-405, I-5, and State Route 4 will see lane closures and detours through early September for construction projectsNo usable supporting receipt — unverified.
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WSDOT plans to close up to two southbound lanes of I-405 from milepost 12 to Coal Creek Parkway Southeast“405: Up to two lanes of southbound I-405 from milepost 12 to Coal Creek Parkway Southeast (milepost 10) will be closed overnight, 9 p.m. Thursday, Sept. 3 – 5 a.m. Friday, Sept. 4.”
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The closure of I-405 lanes is scheduled from 9 p.m. Thursday, Sept. 3, to 5 a.m. Friday, Sept. 4“405: Up to two lanes of southbound I-405 from milepost 12 to Coal Creek Parkway Southeast (milepost 10) will be closed overnight, 9 p.m. Thursday, Sept. 3 – 5 a.m. Friday, Sept. 4.”
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I-5 will have single-lane reductions nightly from 8 p.m. to 5 a.m. near Alger/Lake Samish Road (exit 240)“005: The northbound and southbound I-5 will be reduced to a single lane from 8 p.m. to 5 a.m. nightly Monday, Aug. 31, through Friday morning, Sept. 4, near Alger/Lake Samish Road (exit 240) for fish passage construction.”
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The single-lane reductions on I-5 are scheduled through Sept. 4“005: The northbound and southbound I-5 will be reduced to a single lane from 8 p.m. to 5 a.m. nightly Monday, Aug. 31, through Friday morning, Sept. 4, near Alger/Lake Samish Road (exit 240) for fish passage construction.”
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State Route 4 will close a single lane between 50th and 42nd Avenues weekdaysNo usable supporting receipt — unverified.
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The single lane closure on State Route 4 is scheduled from 7:30 a.m. to 5 p.m.“004: Monday, Aug. 17 through Friday, Sept. 11: A single lane in both directions of SR 4 between 50th Avenue (milepost 56.4) and 42nd Avenue (milepost 57.2) will be closed weekdays from 7:30 a.m. to 5 p.m., for buried gas main line extension work.”
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The single lane closure on State Route 4 is scheduled until Sept. 11“004: Monday, Aug. 17 through Friday, Sept. 11: A single lane in both directions of SR 4 between 50th Avenue (milepost 56.4) and 42nd Avenue (milepost 57.2) will be closed weekdays from 7:30 a.m. to 5 p.m., for buried gas main line extension work.”
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WSDOT notes these closures are for fish passage construction on I-5No usable supporting receipt — unverified.
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WSDOT notes these closures are for utility work on I-405No usable supporting receipt — unverified.
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WSDOT notes these closures are for buried gas main extension on SR 4No usable supporting receipt — unverified.
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The department advises drivers to expect delaysNo usable supporting receipt — unverified.
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The department advises drivers to follow flagger instructions through work zonesNo usable supporting receipt — unverified.