Ames Lake Trestle Bridge No. 1320A Replacement Project
August 17, 2020
King County selected a preferred design alternative to replace the 96-year-old Ames Lake Bridge with a wider structure and a straighter approach. The preferred alternative is the best choice because it has the shortest construction period, the lowest cost, and has no wetland impact. The bridge will be built in the same location as the existing bridge and have no weight restrictions. The road will be closed for the duration of the new bridge construction and traffic must use a detour route.
King County will return for a second open house in early 2023 and construction is set to begin in mid-2023. The new bridge should be complete in mid-2024.
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.
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.
King County selected 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.
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.
Preferred design alternative
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.
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.
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.
King County will continue to inspect and maintain the existing bridge regularly to ensure it is safe to use.
Current weight limits include:
Type 3: 21 tons
Type 3-S2: 34 tons
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.
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.
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.
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.