Snohomish Road Widening Job Adds Lanes, Bridges
📅 Fri January 11, 2013 - West Edition
With 35 named wetlands and eight tributaries plus the Snohomish River, the expansion project presented a “substantial environmental challenge.”
When the project is completed in 2014, the 4 mi. (6.4 km) of SR 522 from the Snohomish River Bridge to Monroe, Wash., will feature four lanes with a median barrier to separate oncoming traffic, a roundabout, a noise wall and upgraded lighting and signage.
Four new bridges will be added, including a new 1,700 ft. (158 m) bridge over the Snohomish River that will be 9 ft. (2.7 m) higher than the existing bridge. Constructed of structural steel, concrete girders, the new bridge on the north side of the existing Snohomish River Bridge will carry westbound SR 522 traffic. A wildlife crossing also will be added.
Nearly 28,000 vehicles travel this stretch of SR 522 each day. Heavy congestion and delays are common in the Puget Sound region, and this small inland city experiences them routinely.
As the terminus for SR 522 since the 1970s, Monroe connects with larger cities to the south via Interstate 405, which has established it as a bedroom community.
The intersection in town where it joins with U.S. Route 2 is often congested with intrastate traffic. Retail development along the highway and residential growth in the city have contributed to gridlock, particularly during summers and holidays.
Widening the road into a four-lane divided highway will reduce congestion and the likelihood of collisions. Between 2006 and 2010, the Washington Department of Transportation reported 100 collisions on this stretch of mainline SR 522, three of them fatal and four with serious injuries. There were an additional 54 collisions at the SR 522/164th Street/Main Street interchange. During the same time period, there were 39 rear-end collisions on this stretch of SR 522.
The additional lane in each direction will increase capacity on this stretch of SR 522 to improve traffic flow and cut down on drive times. The DOT expects that by improving traffic flow, the risk of congestion-related collisions, such as rear-end and sideswipe collisions, will be reduced. The median barrier to separate oncoming traffic will reduce the risk of head-on collisions.
The roundabout will help improve traffic flow and safety at the interchange at 164th Street SE on the northwest side of SR 522. After evaluating current and projected traffic volumes, as well as a variety of options, including turn lanes, signals and roundabouts, the DOT determined that the existing intersection would not be able to handle future traffic volumes. Their analysis showed that a roundabout is the best long-term solution for the intersection and would produce the shortest delays and backups for traffic.
Roundabouts can handle more cars per hour and with less congestion on approaching roads, compared with traditional signalized intersections. They promote a continuous flow of traffic and are safer than traditional stop sign or signal-controlled intersections. Studies have shown that roundabouts reduced injury crashes by 75 percent at intersections where stop signs or signals were previously used for traffic control.
A new direct ramp from eastbound SR 522 to eastbound U.S. 2 also will help alleviate congestion at the interchange.
The risk of collisions with wildlife should also be reduced, due to a new wildlife crossing to provide safe passage for fish and animals. The DOT reported 13 collisions involving wildlife on this stretch of SR 522 from 2006 to 2010.
Two fish barriers are being replaced with a new fish-friendly culvert that also will allow deer and small mammals to pass under the highway. The project also will include fencing to help guide wildlife to the safe crossing under the highway.
Other environmental improvements resulting from the project include new detention ponds to improve water quality. The ponds will collect and filter rain water runoff from the highway before slowly releasing into area creeks, benefitting salmon and other wildlife. The ponds also will reduce the potential for flooding.
A noise study for neighborhoods near SR 522 during the project design phase measured current noise levels and modeled future noise levels based on future traffic volumes.
The noise study showed that future noise levels for the neighborhood on the northwest side of SR 522 between 171st Avenue SE and Mountain View Road SE would exceed 66 decibels, which is the threshold for considering a noise wall.
In addition to the 9 to 10 ft. (2.7 to 3 m) noise wall, a 42-in. (106.7 cm) concrete barrier will be installed along the outside lanes of SR 522 between 164th Street SE and 154th Street SE — 10 in. (25 cm) taller than the barrier typically used on this type of project. Besides preventing vehicles from leaving the roadway, the barrier is expected to reduce tire pavement noise by 1 to 2 decibels, due to the additional height.
Getting to Work
A total of $128.8 million has been raised through a variety of resources, predominantly the 2003 Gas Tax (Nickel Funding).
Scarsella Brothers, Inc. was awarded the $73 million contract in May 2011. Construction began that July. The Kent, Washington-based company specializes in clearing and grading, excavation and drainage, and underground pipe and utilities, performing mass excavation and utility work for commercial and residential customers in the 10 western states.
According to Kris Strutner, general superintendent, 80 percent of the earthwork is done. In addition to the 496,000 cu. yds. (379,219 cu m) of dirt they’ve cut, they have imported an additional 325,000 cu. yds. (248,480 cu m) for construction of the 130,000 sq. ft. (39,624 sq m) structural earth wall for the bridge approach. The lengthy approach accommodates the bridge’s proximity to wetlands, he explained.
“It’s been challenging to accommodate the environment and the weather,” Strutner said. Summer saw a 90-day stretch with no precipitation, but winter is showing its teeth with abundant rainfall.
Fortunately, he said, they planned the project with rain in mind.
Nevertheless, with 35 named wetlands and 8 tributaries plus the Snohomish River, the expansion project presented a “substantial environmental challenge.” A revised plan was developed to mitigate environmental impact during installation of an intermediate bridge.
“Our original permit plan called for two seasons [of work] back to back to coordinate with ’fish windows’ from January 1 to September 30,” Strutner said. Instead, they regrouped by compressing their schedule and applying for a one-month extension to reduce the disruption. “The trade-off is that we have to do it in one season.” Happily, he said they completed the work with two weeks to spare.
The substructure for the Snohomish bridge is done, but work on the superstructure is still going on. Strutner said that 50 percent of superstructure is completed. The second half — erection — will begin in March.
The superstructure sits on a pier — a 30 ft. (9 m) column with 10 ft. (3 m) diameter drilled shaft. A temporary access work trestle was built to enable crews to construct the structure. “We’re using a girder launching system because there’s no way to go across the river using a crane,” Strutner said.
This system is typically reserved for areas with environmental impact, he added. Subcontractors SB Structures and Apex Steel are responsible for the launching system. “It takes precision and a willingness for risk.”
Having a Blast
Rock blasting between the Snohomish bridge and Monroe to make room for the new lanes began in July. In order to create space for the new roadway northwest of the existing road, crews are blasting and removing 350,000 cu. yd. (267,594 cu m) of rock along the westbound lanes. Strutner said the material will be incorporated on the project.
The DOT anticipates 150 closures to complete the rock-blasting work. Each blasting operation will take about an hour from start to finish and must be done during daylight hours. To keep drivers safe, one-hour closures in both directions are scheduled for rock blasting twice a week, rain or shine. “There’s no weather sensitivity in blasting,” Strutner said.
Working a 5-day schedule, the 60-man crew operates a fleet of 14 35-ton (31.8 t) off-road haul trucks, three PC 400 and 400 excavators; D8 and D10 excavators; 22 over-highway trucks and three rock drills (at peak).
The project is “straight-forward work,” Strutner said, but it’s “intriguing because of the magnitude.” One of the complications is manipulating staging to keep traffic moving.