|REASON FOR RECOMMENDED ACTIONS/BACKGROUND
On February 9, 2021 the Board of Supervisors (Board) received an update on the County Road (CR) 41 (Att. A – Location Map) right-of-way (ROW) at the location where Cache Creek eroded its bank and washed out several hundred feet of road not on the County’s maintained mileage. Two alternatives were presented for reconnecting the road and direction was given to staff to investigate both alignments simultaneously.
During staff’s ongoing discussion with affected landowners and representatives from the Yocha Dehe Wintun Nation following the February Board meeting, an additional alternative was put forward for consideration. Therefore, staff is bringing these three alternatives to the Board for consideration, along with additional research and reports obtained regarding the conditions of the site. The alternatives (Att. B – Alternatives Map) include:
Alternative 1 - Reconstruct CR 41 within the existing right-of-way (ROW)
Alternative 2 - Obtain new ROW and set the road back (east) from the washout and in front (west) of Mr. Hutchens' house
Alternative 3 - Obtain new ROW and set the road east of Mr. Hutchens' property, including a dry arroyo crossing east of the house
Upon request County staff sought outside engineering expertise from WSP, a global leader in providing engineering consulting services, to obtain an estimate to place CR 41 within the existing ROW. This alternative is attractive for a few reasons, the future stability of the bank would be established, and no additional ROW would be needed.
After a site visit and discussion with WSP and several case matter experts it was determined that a soldier pile wall with an Embankment Confinement System (bank armoring) would be the best solution to protect from further creek erosion in this area and accomplish this alternative. The disturbance required within Cache Creek would involve an extensive environmental review process, and state and federal oversight of each phase of the project. The estimated schedule for design, environmental clearance and permitting is estimated to be 3 to 4 years with a cost estimate for this effort expected to be about $10 million.
When County staff previously presented this alternative to the Board, concern was raised regarding the long-term viability given the potential for continued erosion of the creek bank. To understand the future movements of the creek, the County contracted with a geomorphologist, Norman Braithwaite of Pacific Hydrologic, Inc., to provide a qualitative assessment (Att. C – Geomorphology Assessment).
The assessment showed that some additional erosion to the bank will likely occur, however given the current situation there is a good chance that the creek will reroute away from the existing bank using the nascent cutoff pictured in Figure 8 of the report. Staff has taken this data and revised the road alignment to allow for likely continued erosion in the creek and increasing the length from the previously reported 920 feet to 1200 feet. With this change the cost estimate for this alternative is $250,000 and the anticipated schedule for design, environmental clearance and permitting is estimated to be 1 year.
This alternative was discussed with the affected landowners following the February Board meeting but was not supported for several reasons; the alternative requires more ROW acquisition, the realigned road is significantly longer and is therefore more expensive, and the proposed route has greater disturbance to the natural resources in the area. The dry arroyo crossing is a significant part of the cost and disruption to the natural environment. The estimated schedule for design, environmental clearance and permitting is estimated to be 2 to 3 years with the cost estimate for this alternative at $350,000.
Of the three alternatives, Alternative 2 is the lowest cost and has the least impact to the landowners and the natural resources in the area. The reduced impact on the natural resources include both cultural and environmental. It should be additionally noted that the reduced need for new materials equates to reduced greenhouse gas emissions and the shorter length requires less ROW acquisition. Alternative 2 also has the shortest design, right-of-way and environmental permitting schedule of all three alternatives.
Alternative 1 provides the least permanent impact to local land owners and will provide a reliable long-term design, however it requires extensive agency oversight, has a long timeline for environmental clearance, requires a large amount of raw materials and is very costly to construct. Alternative 3 has the least amount of risk long term, however since the geomorphology assessment demonstrated minimal risk for Alternative 2, this benefit is outweighed by the additional burden on the natural resources and increased costs. Given these facts County staff doesn’t recommend pursuing either Alternatives 1 or 3.
Given the likely long-term reliability of the Cache Creek bank, staff recommends Alternative 2 as the best approach to reestablishing this unmaintained portion of CR 41 that is a vital route necessary for fire evacuation and disaster response. Currently the estimate of $250,000 is unfunded, therefore further budgetary action will be needed to move forward with design and construction. If funds can be identified for this project construction could commence as early as the fall of 2022.