Project Description

The California Department of Transportation (Caltrans) proposes to upgrade the bridge railings at Yellow Creek Bridge (approximately 44 linear feet) (PM 6.52) and at Arryo Seco Bridge (approximately 164 linear feet) (PM 8.43) on SR 121 in Sonoma County, California. The Project would also include widening Yellow Creek Bridge approximately 6 inches on each side (for a total of approximately 12 inches) and Arryo Seco Bridge approximately 8 inches on each side (for a total of approximately 16 inches), removing the MBGR and alternative flared terminal systems, installing MGS and alternative in-line terminal systems, constructing concrete anchor blocks, and installing vegetation control. The Project footprint encompasses the maximum extent of construction-related activities, including ground disturbance and staging areas, and is approximately 0.26 acre for Yellow Creek Bridge and 0.60 acre for Arroyo Seco Bridge.

Click on the two maps below to see a larger version.

Figure 1-3 Yellow Creek Bridge Project Components

Figure 1-4 Arroyo Seco Bridge Project Components

Project Features

Widen Bridges
The Project would widen Yellow Creek Bridge approximately 6 inches on each side (for a total of approximately 12 inches) and Arroyo Seco Bridge approximately 8 inches on each side (for a total of approximately 16 inches) to comply with the design and installation standards outlined in the AASHTO MASH. Widening the bridges would avoid narrowing the SR 121 travel lanes and would accommodate upgrading the bridge railings.

Upgrade Bridge Railings
The concrete baluster bridge railing at Yellow Creek Bridge would be upgraded with Type 85 concrete barriers with tubular handrailing. The MBGR at Arroyo Seco Bridge would be upgraded with California ST-75 bridge railing with tubular handrailing.

Remove Metal Beam Guardrail and Install Midwest Guardrail System and Alternative In-Line Terminal System
The Project would remove MBGR along, and alternative flared terminal systems at the end of, the bridge approach and departure sections, and install MGS and alternative in-line terminal systems. The MGS would consist of either wood or steel posts, wood blocks, and steel guardrails. The design would be finalized during the plans, specifications, and estimates (PS&E) phase.

Construct Concrete Anchor Blocks

Concrete anchor blocks would be constructed within previously disturbed areas at both bridges to provide a transition element between the upgraded bridge railings and the MGS to be installed. The concrete anchor blocks may be constructed off the structures; in this case, new footings would be installed approximately 2 feet wide and 3 feet deep. The concrete anchor blocks would be between approximately 7 to 15 feet long, 2 feet wide, and 3 feet tall. The design would be finalized during the PS&E phase.

Install Vegetation Control

Vegetation control would be installed at the bridges in conjunction with the MGS. Fiber/rubber matting may be used as a vegetation control.

Access and Staging

Areas for overnight storage of equipment and materials are anticipated to be limited to occurring in areas within the Caltrans right of way (ROW), such as within the closed lane adjacent to the bridge railing being upgraded. Staging areas are anticipated to be determined prior to the PA&ED phase

Right of Way Requirements

Construction-related activities, including staging areas, would occur within Caltrans ROW. The Project would not require ROW acquisition for the purposes of temporary construction easements or permanent drainage easements.

Construction Methods

Schedule:
Begin construction January 2025 and conclude October 2026.
Daytime work with two weeks of nightwork anticipated for:
• Restriping for temporary one-way alternating traffic control.
• Installing temporary barrier systems and temporary crash cushions along the centerline of SR 121.
• Removing the bridge railings, MBGR, and alternative flared terminal systems.

• Installing MGS and alternative in-line terminal systems.

Stage 1:

-Closing the lane adjacent to the bridge railing being upgraded.
-Restriping for temporary one-way alternating traffic control.
-Installing temporary barrier systems and temporary crash cushions along the centerline of SR 121.
-Installing temporary traffic signals along the approach sections.
-Staging areas would be established within the lane closed to traffic (i.e., within Caltrans ROW) for the overnight storage of equipment and materials.
-To maintain the use of SR 121 for the traveling public, the bridge railings would be upgraded one lane at a time.
-One-way alternating traffic control would keep the other lane open to the traveling public in both directions.
-Temporary traffic signals would stop the traveling public at either end of the bridge approach sections.

Stage 2:

- Clearing and grubbing vegetation prior to removing the bridge railings, MBGR, and alternative flared terminal systems adjacent to the lane closed to traffic in both directions.
- The bridge railings would be upgraded, concrete anchor blocks would be constructed, MGS would be installed, and vegetation control would be installed.
- This construction methodology would then be repeated on the other side of SR 121, with the previously closed lane reopened.

Stage 3:
- Removing temporary work platforms placed below the bridge deck overhangs, removing temporary debris catchment systems, removing BMPs, removing environmentally sensitive area fencing, and removing construction area signs
- Restriping
- Removing temporary barrier systems along the centerline of SR 121, temporary crash cushions, and temporary traffic signals along the approach sections
- Reopening the closed lane to the traveling public

Equipment Would Include:
-Utility truck, Air compressor, Back hoes, Excavators, Cranes, Dump trucks, Jack hammer, Pavement cutter, Concrete truck, Generator, Vacuum, Water truck, Generators, and Street sweeper

Project Location Photos

Photo 1: Yellow Creek Bridge, looking southwest. Concrete baluster bridge railings, metal beam guardrails, 12-foot-wide travel lanes, no shoulders, and no designated pedestrian or bicycle facilities.

Photo 2: A view of Yellow Creek Bridge, from within Yellow Creek, looking east towards the Coast Range. There is a missing portion of the top bridge railing along the northbound lane of State Route 121.

Photo 3: Yellow Creek Bridge, looking southeast. The steel beneath the concrete baluster railing is exposed on the northern segment of the bottom horizontal rail member west of the southbound lane of SR 121.

Photo 4: Yellow Creek Bridge, looking northwest. Concrete baluster bridge railings, metal beam guardrails, 12-foot-wide travel lanes, no shoulders, and no designated pedestrian or bicycle facilities.

Photo 5: Arroyo Seco Bridge, looking west. See-through 75 bridge railings, metal beam guardrails, 12-foot-wide travel lanes, no shoulders, and no designated pedestrian or bicycle facilities.

Photo 6: Arroyo Seco Bridge, looking west. See-through 75 bridge railings.