Based on the environmental evaluation in the Initial Study for the County Road 40 Over Cache Creek Bridge Replacement Project, with the implementation of prescribed mitigation and other measures to reduce environmental impacts, the Project was determined not to have a significant effect on the environment. Adoption of this Mitigated Negative Declaration will allow the Project to move forward through the environmental permitting process for bridge construction.
BACKGROUND
The County Road 40 Bridge (also known as the Low Water Bridge) over Cache Creek was constructed in 1930. The existing bridge (Bridge No. 22C-0091) consists of a 115-foot long, 22-foot wide, six-cell, reinforced concrete box culvert with three open cells. Three of the six cells were plugged with concrete sometime between 1930 and 1979 when Caltrans began biannual inspections of the structure. The north side of the bridge is accessed via CR 40, a single lane gravel road that connects to State Route 16. In its 2008 bridge inspection report, Caltrans rated the bridge’s safe load capacity at zero tons, deeming the bridge as unsafe and inoperable to vehicular traffic. The structurally deficient bridge was closed to vehicular traffic that year.
When it is not inundated, the bridge still provides pedestrian access to public lands, such as recreational trails and park lands. The bridge may be inundated during the winter due to storm events, and in spring and summer due to water releases from the Cache Creek Dam, upstream of the bridge near Clear Lake.
Identifying that this bridge is a key access point to fire fighting in a very remote area of northwest Yolo County, in 2018 the California Department of Forestry and Fire Protection (CAL FIRE) entered into an agreement with Yolo County to provide funding to complete the engineering design for a replacement bridge.
PROJECT DESCRIPTION
Yolo County proposes to replace the existing CR 40 bridge over Cache Creek with a new three-span, cast-in-place, reinforced concrete slab superstructure, supported on two column pile extension bents and seat type abutments founded on 30-inch cast-in-drilled-hole concrete piles. The maximum depth of excavation for the bridge piles is approximately 30 feet. The replacement bridge will be constructed on an improved alignment at essentially the same location as the existing bridge. The bridge will provide a minimum clear width of 20 feet, the same as the existing structure. The structure will be constructed with a horizontal curve radius of 132 feet, to accommodate CAL FIRE’s 72-foot long tractor and trailer vehicle used to transport their fire-fighting equipment across Cache Creek.
Yolo County ceased maintenance on CR 40 in 2009 from State Route (SR) 16 to the Lake County line per Resolution 09-31. CR 40 is no longer maintained by the County and its “county highway” designations have been removed, as most the road extending from Lake County to State Route 16 is not under Yolo County jurisdiction. Since the remainder of the CR 40 roadway is not maintained by the County, as a matter of public safety, the County believes that the gate near its intersection with SR 16 should remain normally closed/locked. Even when the CR 40 gate at SR 16 is closed, the bridge will be accessible to pedestrian, ATV, and equestrian traffic.
Due to the limited traffic use of the bridge, a bridge that satisfies the standard design hydraulic clearances is not proposed. The 50-year and 100-year storm events are expected to overtop the bridge by approximately 8 and 13-feet respectively. The County will request a design exception from Caltrans for hydraulic clearances. Due to bridge inundation during high design flows, the County is proposing to use the new California State Type ST-75 bridge rail with tubular bicycle railing. The Type ST-75 bridge rail will allow inundation flows to pass through the rail members. The heavy-duty steel tube rails are expected to undergo little to no damage when subjected to drift impacts.
Pedestrians and bicyclists, as well as ATV users and equestrians will use the proposed replacement bridge to access recreational trails, parks, and the southeast bank of Cache Creek. The proposed bridge will provide a minimum freeboard clearance of 8-feet for recreational rafters during summer irrigation flows in Cache Creek. During construction, portage signage for recreational rafters will direct them out of Cache Creek upstream of the construction zone and around the bridge construction site to a creek entrance location downstream of the existing bridge.
To build the bridge in essentially the same alignment as the existing low water bridge and provide the needed vertical clearance for irrigation flows and rafters (i.e., will no longer be a low water crossing), the approach roadway construction requires imported fill material. Two retaining walls will be constructed to contain the approach fill at the west end of the new bridge. Rock slope protection is required around the new abutments and these retaining walls to protect the bridge during inundation flows.
ENVIRONMENTAL REVIEW
A Natural Environmental Study was prepared for the Project area which supports the Initial Study/Mitigated Negative Declaration (Attachment A). The Initial Study/ Mitigated Negative Declaration was submitted to the State Clearinghouse, and subsequently circulated for public review and comment on September 9, 2020. Comments were received during the review period through October 9, 2020, and responses to those comments are included in the attached memorandum (Attachment B).
County staff has applied with the Yolo Habitat Conservancy for coverage of this proposed Project under the Yolo Habitat Conservation Plan/Natural Community Conservation Plan (Yolo HCP/NCCP).
The County also initiated an early consultation request with interested Tribes under the provisions of Assembly Bill (AB) 52, and subsequently met with Cultural Resources staff of the Yocha Dehe Wintun Nation (Yocha Dehe/Tribe), who indicated a cultural interest and authority in the project area. A site visit was conducted at the project site with Yocha Dehe’s Cultural Resources Director, Caltrans and County staff, and the County’s consultant team, including an archaeologist. Initially the original design alignment landed the bridge in the middle of a known cultural resource area along the creek bank. Yocha Dehe’s team collaboratively worked with County staff and its consultant team to provide an improved location to avoid the sensitive area. Details of the consultation process are outlined in the Initial Study provided in Attachment A.
The County is working to receive a Categorical Exclusion from Caltrans as part of their National Environmental Policy Act (NEPA) determination. All studies required for NEPA have been approved by Caltrans with the exception of the cultural resources suite of studies: Historic Property Survey Report, Archaeological Survey Report, Environmentally Sensitive Area Monitoring and Discovery Plan, and the Finding of No Adverse Effect. Caltrans required this documentation despite the fact that the project was sited to avoid impacts to the satisfaction of Yocha Dehe, and the Tribe did not desire any additional studies or archaeological testing. The initial reports to meet this requirement were sent to Caltrans on 1/3/2020. After several iterations the final package that has met all the requirements of Caltrans staff was submitted on 10/27/2020. Once District 3 signs these documents, they will be transmitted to Caltrans headquarters for their approval and transmittal to the State Historic Preservation Officer (SHPO). Our understanding is that SHPO has 30 days to review this package. We hope to receive these final environmental approvals in December 2020, so we can proceed with finalizing the bridge design for construction. The County will be responsible for implementing the conservation and mitigation measures outlined in the Mitigation Monitoring and Reporting Program (MMRP) (Attachment B), as referenced in the attached Initial Study/Mitigated Negative Declaration.
CAL FIRE, with the timely assistance of Assemblymember Cecilia M. Aguiar-Curry, has also encumbered $2 million in construction funding to be allocated toward the CR 40 bridge replacement construction. Bridge construction is estimated to cost approximately $4 million. The balance of construction funds is planned to be reimbursed by the federal Highway Bridge Program once funding is programmed by Caltrans.
Staff anticipates finalizing design and receiving the required local, State, and federal construction permits in early 2021, going out to bid in Spring 2021, with construction following through Fall of 2021. |