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  1. Road Services
  2. Ames Lake Trestle Bridge No. 1320A Replacement Project

Ames Lake Trestle Bridge No. 1320A Replacement Project

Photo of the bridge.
Ames Lake Trestle Bridge No. 1320A.


Map showing location of Ames Lake Trestle Bridge.
The bridge crosses Ames Creek on Ames Lake-Carnation Road NE, in rural unincorporated King County between Redmond and Carnation.

Latest update

February 28, 2020 - Road Services hosted a public open house on February 27 from 5 to 7 p.m. at Redmond Fire Station 14. The community was invited to drop in to learn about the project and give feedback on proposed design options for the new bridge.

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Broch Bender, Communications Program Manager
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Project overview

This project replaces the 96-year-old Ames Lake Bridge with a wider structure and straighter bridge approaches. The improvements are designed to increase sight distance for drivers and provide a safe, unrestricted crossing for trucks and vehicles of all sizes. In addition, the new bridge will be designed to have less environmental impact on Ames Creek and the surrounding wetlands.

The Ames Lake Trestle Bridge was originally designed to carry smaller, lighter trucks and vehicles. In order to prevent damage and keep the bridge safe for passenger cars and trucks, very heavy trucks and specialized hauling vehicles are currently prohibited from crossing this bridge. These heavy vehicles will continue to be restricted until the new bridge is complete.

Project schedule

King County is in the process of selecting a preferred alternative for a replacement bridge, with construction projected to begin in 2023. The preliminary estimated total project cost is $15 million. This project is funded through the King County Capital Improvement Program and the Road Services Division Operating Budget.

Ames Lake Trestle Bridge project schedule

Bridge access for residents and emergency vehicles will be maintained throughout construction. Construction activities will include demolition, concrete pouring, and crane lifts. After the new bridge is opened to traffic, crews will continue low impact restoration work including plantings and site clean-up.

Help us select the preferred alternative for your new bridge

King County is evaluating three design alternatives for a replacement bridge. Project team members will use a variety of evaluation criteria, including comments from the public, to select the final design from among the three design alternatives for the new bridge.

Find images of the bridge alternative options below:

You can submit your bridge alternative preference and comments to Broch.Bender@kingcounty.gov . We welcome public comments on the design alternatives until the close of the preliminary design period in late March 2020.

Roadway alignment Alternative 1

Alternative 1.

Alternative 1 overview

  • Builds new bridge and road approach slightly west of the existing bridge and maintains two-way traffic across the existing bridge during construction.

  • After construction of the new bridge is complete, traffic shifts to the new bridge, the existing bridge is removed, and the site is restored.


Advantages

LOWER CONSTRUCTION COST, SHORTER CONSTRUCTION DURATION: Follows existing topography where possible to reduce bridge length and retaining wall height, which reduces construction cost and duration.

MORE ACCESSIBILITY: Two-way traffic maintained throughout construction.

EASIER TO BUILD: Less complicated access and constructability.

NO DIRECT WETLAND IMPACT: Bridge foundations are anticipated to be built outside of wetlands.

Disadvantages

IMPACTS TO NEIGHBORS: Some property acquisition required along western edge. Temporary impacts to existing driveways during construction.

Roadway alignment Alternative 2

Alternative 2.

Alternative 2 overview

  • Builds the new bridge and road approach slightly east of existing bridge and maintains two-way traffic across the existing bridge during construction.

  • After construction of the new bridge is complete, traffic shifts to new bridge, the existing bridge is removed, and the site is restored.


Advantages

MORE ACCESSIBILITY: Two-way traffic maintained throughout construction.

Disadvantages

HIGHER CONSTRUCTION COST, LONGER CONSTRUCTION DURATION: Long, steep slopes on east side of existing bridge require a longer bridge with higher retaining walls, which increases construction cost and duration.

MORE DIFFICULT TO BUILD: More complicated construction access along steep slopes.

POTENTIAL DIRECT WETLAND IMPACT: Some work within wetlands required at both north and south ends of the bridge.

IMPACTS TO NEIGHBORS: Some property acquisition required along eastern edge.

Roadway alignment Alternative 3A

Alternative 3A.

Alternative 3A overview

  • Builds the new bridge and road approach in the footprint of the existing bridge and maintains alternating one-way traffic on the temporary bridge during construction.

  • Prior to construction of the new bridge, traffic shifts to a single-lane temporary bridge, and the existing bridge road approaches and the existing bridge are removed.

  • Maintains alternating oneway traffic on the temporary bridge.

  • After construction of the new bridge and road approaches are complete, traffic shifts to the new bridge, the temporary bridge is removed, and the site is restored.

Advantages

  • EASIER TO BUILD: Locating new bridge in the same place as the existing bridge requires less ground shoring and leveling (grading). It also minimizes the size of retaining walls that will be required.

  • NO DIRECT WETLAND IMPACT: Temporary and permanent bridge foundations are built outside of wetlands.

Disadvantages

  • IMPACT TO NEIGHBORS: Some property acquisition required along eastern and western edges. Minor temporary impacts to existing driveways during construction.

  • HIGHER CONSTRUCTION COST: Temporary bridge makes logistics more complex and increases construction costs.

  • LONGER CONSTRUCTION DURATION: Construction of temporary bridge adds time to overall construction duration.

  • LIMITED ACCESSIBILITY: Possible traffic backups due to signalized alternating lanes throughout construction.

  • TEMPORARY ACQUISITION: Some temporary construction easement along western edge for the temporary bridge.

Roadway alignment Alternative 3B

Alternative 3B.

Alternative 3B overview

  • The roadway will be closed to traffic during demolition of the existing bridge and construction of the new bridge.

  • Traffic will use a detour route for the duration of the new bridge construction.

Advantages

  • EASIER TO BUILD: Locating new bridge in the same place as the existing bridge requires less ground shoring and leveling (grading). It also minimizes the size of retaining walls that will be required.

  • NO DIRECT WETLAND IMPACT: Permanent bridge foundations are built outside of wetlands.

  • LOWEST CONSTRUCTION COST: Will offer significant cost savings due to the small project footprint and absence of a temporary bridge.

  • LOWEST CONSTRUCTION DURATION: Much faster construction times with no temporary bridge, minimal ground shoring and leveling, and no adjacent traffic.

  • BETTER WORKER SAFETY: Removing traffic near work zones creates a safer work environment.

  • ENVIRONMENTALLY FRIENDLY: The smaller project footprint requires less tree removal and environmental disturbances.

Disadvantages

  • IMPACT TO NEIGHBORS: Some property acquisition required along eastern and western edges. Minor temporary impacts to existing driveways during construction.

  • NO ACCESSIBILITY: The road will be closed for the duration of the new bridge construction and traffic must use a detour route.

Photos

Ames Lake Trestle Bridge signs.
Vehicle weight restriction signs for the Ames Lake Trestle Bridge.
Under the Ames Lake Bridge.
View of the timber support piles under the bridge.

Frequently-asked questions

The Ames Lake Trestle Bridge was built more than 90 years ago and was originally designed with narrow lanes for much smaller vehicles compared with what we see on the road today. The bridge has a posted weight restriction for specific large trucks and specialized hauling vehicles. Replacing the bridge will provide a safer, unrestricted crossing for the community.

The original timber piles that support the deck are decaying. Over time, the poor condition of the piles could prohibit large trucks and emergency vehicles from crossing, which eventually would require the bridge to be shut down completely.
The new design removes vehicle weight restrictions and improves sight distance by widening and straightening the road. A wider and straighter road helps users on the bridge, and those coming out of adjacent driveways, to see farther down the road. In addition, the new bridge will be designed to have less environmental impact on Ames Creek and the surrounding wetlands.
The bridge crosses Ames Creek on Ames Lake-Carnation Road NE, in rural unincorporated King County between Redmond and Carnation.
Approximately 1,900 vehicles and 70 trucks cross the bridge every day. It is a County-designated snow route. Ames Lake-Carnation Road NE serves a growing population of single-family homes, farm and forest lands.
Yes. The bridge remains safe for passenger cars and trucks. The County restricts specific heavy trucks and specialized hauling vehicles, and the limits are posted near the bridge. These heavy vehicles will continue to be restricted until the new bridge is complete.

King County will continue to inspect and maintain the existing bridge regularly to ensure it is safe to use.
Bridge weight restrictions. Yes, there are.

Current weight limits include:
Type 3: 21 tons
Type 3-S2: 34 tons

Single-unit vehicles:
3 axles or fewer: 21 tons
4 axles: 19 tons
5 axles: 22 tons
6 axles: 25 tons
7 axles: 28 tons

King County regularly inspects the bridges it is responsible for maintaining. If new restrictions are required based on these inspections and bridge load rating analysis, a notice will be posted on the bridge. The County will also note any new restrictions on the Bridge Weight Restrictions website.
King County is evaluating three design alternatives for a replacement bridge. We will present the three design alternatives to the public at a Community open house on Feb. 27, 2020, from 5 to 7 p.m. at Redmond Fire Department, Station 14. The final bridge design will be determined in spring 2020. Project construction is expected to begin in 2023.
The length of construction depends on which design alternative the county selects. We are currently in the design selection process. The project team will update the construction schedule timeline in late 2020.

All project construction work will comply with terms and conditions set by our partner permitting agencies. Crews will follow best practices to avoid negative environmental effects to the stream and other natural surroundings and keep the road open to traffic during construction.

Bridge construction schedule.
The project will replace the bridge in the same general location on Ames Lake-Carnation Road NE. The new bridge could be located slightly upstream or downstream from the current location, depending on the final design.
No. The new bridge will be built to current standards and will not have vehicle weight or size restrictions.
Bridge access for residents and emergency vehicles will be maintained throughout construction. Of the three bridge design alternatives under consideration, one of them would involve building a one-lane temporary bridge to keep traffic moving along the road while construction is underway. Other alternatives would maintain traffic on the existing bridge while the new bridge is constructed next to it. There will be short-term full closures for certain construction activities, such as delivery and placement of bridge beams. Local access for residences will be maintained.
The preliminary estimated total project cost is $15 million.
The King County Council adopted $12.7 million in funding within the Road Services Division 6-year Capital Improvement Program during the 2019 – 2020 biennial budget process. Additional funds for this project come from the Road Services Division Operating Budget.
The project will remove, transport, and dispose of the existing creosote-treated timber piles at an approved disposal facility.

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201 S Jackson Street
Seattle, WA 98104
Hours: 8 a.m. - 5 p.m.

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