The proposed bridge replacement structure will have its supports built behind the existing bridge abutments and as such would be slightly longer (60+/- feet) than the existing bridge length of 53 feet. This approach would keep the new abutments outside the natural creek channel (minimize environmental impacts). Two (2) bridge design alternatives were considered:
#1. 60+/- foot Single Span Steel Girder Bridge
#2. 60+/- foot Single Span Precast Prestressed Girder/Voided Slab Bridge.
Construction of the new bridge abutments will require two excavation areas approximately 35 feet wide by 15 feet long by and up to 15 feet deep. Cast-in-Drilled-Hole (CIDH) piles will be used per geotechnical study recommendations. These deep foundations are anticipated to be fairly short in length due to the shallow bedrock. Noise and vibration from pile construction would likely not generate significant concerns as there are no nearby residents or other sensitive receptors within the project study area. Attachment B includes diagrams of the bridge.
Proposed Bridge Profile
The design of the proposed bridge will conform to the “AASHTO Policy on Geometric Design of Highways and Streets 2011, 6th Edition Green Book” and "AASHTO Very Low Volume Local Road Guidelines" along with County standards where appropriate. In addition, per County and Caltrans coordination the proposed bridge will be designed to pass the 100-year flood (base flood) and the overtopping flood (design flood) with no freeboard. This design criteria will require a design exception as it does not meet the Federal Highway Administration (FHWA), Caltrans and the County’s freeboard requirements.
Bartlett Springs Road is a rural, one lane, unpaved road that varies in width from 12' to 24' in width. With a low Average Daily Trips (ADT) of 127 (projected by 2034), the recommended minimum width of traveled way is 20 feet plus 2 foot shoulders on each side, for a total of 24 feet, for the proposed roadway approaches. The new roadway approaches will be unpaved and will conform to the existing roadway condition and width, with standardized transition railings and end treatments planned for all four quadrants of the bridge crossing.
In-Channel Work and Detour Route
Some temporary in-channel work may be required to remove the existing bridge structure. Constructing the existing bridge on the same alignment will require on site detour around the construction zone to maintain through traffic on Bartlett Springs Road. Fortunately, an existing well established low water crossing is directly adjacent to the existing bridge and appears to be a regularly used route by vehicular traffic. This existing and well defined low water crossing is considered the most viable option for redirecting traffic and construction equipment as it will not require additional vegetation removal and minimal earthwork grading within the waterway. To minimize these potential water quality impacts, it is anticipated that construction will be completed in one construction season, at a time when the creek is dry. However, depending on the creek flows at the time of construction, a temporary stream diversion may be required, which may include screened pumps, a temporary pipe network, and clean gravel fill to route flow through and around the immediate work area, maintain dewatered conditions, and return flow to the downstream channel network without causing harm to biological resources or affecting water quality. Attachment C includes the Natural Environmental Study that was completed by Caltrans for the project on April 2018.
Staging Areas, Rights of Way, and Utilities
Staging areas will be established on private property along the north side of Bartlett Springs Road. There will not be any need for permanent right-of-way acquisition. This minor temporary construction easement area are all that will be required, and the project will be built within the footprint of the existing bridge. There is an existing buried fiber optic line running parallel to the existing road alignment on the southern side of Bartlett Springs Road. The fiber optic line appears to be outside of the project limits. As a result, work on this bridge will not impact this utility. No other utilities are located near the proposed project limits.
Construction Equipment and Schedule
Typical construction equipment will include the following: backhoes, dozers, excavators, dump trucks, and concrete breakers for the removal of the existing bridge, excavation of the abutments and construction of the new bridge structure. Bridge foundations will require equipment to drill the cast-in-place drilled piles including cranes to lower the steel reinforcing steel in the drilled hole, with concrete trucks to fill the drilled holes with concrete. Erection of steel and precast bridge components will involve hauling trucks, small cranes, and temporary scaffolding. Components of the bridge that are cast-in-place, will require additional formwork and falsework. Roadway work will require use of graders and dump trucks and earth moving equipment such as bulldozers or graders. It is anticipated that construction will begin in summer of 2023.
Construction activities will occur in the approximate sequence
• Relocate Utilities- if necessary, currently not anticipated.
• Construct temporary detour and stream diversion downstream of bridge (if required based on stream flow).
• Remove the existing bridge and bridge foundations.• Construct new bridge foundations and abutments. Abutments will rest on cast-in-drilled-hole pile foundations.
• Construct bridge superstructure, by erecting steel girders and precast deck components hauled in from off-site.
• New rock slope protection (RSP) will be installed along the re-constructed embankments in the areas disturbed by foundation excavation. A large excavator with bucket/thumb attachment would place/fit RSP on the slopes.
• Install bridge safety railing system.
• Construct roadway approaches including final grading and approach guard railing
• Complete remove temporary creek crossing detour, if installed.
• Final site clean-up of all staging and construction work area.
The following permits will be required pursuant to the Lake County Municipal Code:
• Community Development Department – Complex Grading Permit
• Community Development Department – Building Permit
The following permits are required, and a copy of these permits will need to be sent to Caltrans
Senior Environmental Planner of District 1 Local Assistance before construction begins:
• Regional Water Quality Control Board - 401 Permit
• U.S. Army Corps of Engineers - 404 Permit
• CA Department of Fish and Wildlife - 1602 Permit Stream Alteration Agreement
Funding for the project comes from the Federal Highway Administration through the Federal Highway Bridge Program. As the agency responsible for oversight, Caltrans is responsible for implementing funding and project approvals.