TO: The Honorable Lake County Board of Supervisors
FROM: Lars Ewing, Interim Public Works Director
Mireya G. Turner, Community Development Director
Michelle Irace, Senior Planner
DATE: November 18, 2025
SUBJECT: 2:00 P.M. - Consideration of Adoption of Addendum to the Initial Study/Mitigated Negative Declaration (IS/MND) for the South Main Street and Soda Bay Road Widening and Bike Lanes Project
Exhibits
A. CEQA Addendum, October 2025
Attachment A: References
Attachment B: Nighttime Construction Noise Memorandum (May 2016)
Attachment C: Supplemental Biological Resources Review (January 2016)
Attachment D: Caltrans Section 7 Biological Revalidation (May 2025)
B. Caltrans NEPA Revalidation, June 2025
C. January 24, 2013, Planning Commission Staff Report
D. 2012 Initial Study with Mitigated Negative Declaration/Environmental Assessment
EXECUTIVE SUMMARY
As your Board is aware, the County is rapidly progressing with the South Main Street and Soda Bay Road corridor improvement project. The project proposes to reconstruct and widen the existing two-lane road corridor to three lanes, add 8-foot shoulders, underground existing overhead utilities, and incorporate an extension of the City of Lakeport’s water main in the unincorporated area south of Lakeport. Following extensive environmental studies, securing various regulatory permits, acquiring numerous rights-of-way, and securing sufficient funding through the California Transportation Commission, the County is now ready to advance the project to the construction phase.
The project is funded, in part, by grant funding received from the Federal Highway Administration (FHWA). As such, the project required evaluation under both the California Environmental Quality Act (CEQA) and the National Environmental Policy Act (NEPA). The County was the lead agency under CEQA and the California Department of Transportation (Caltrans), as assigned by the Federal Highway Administration (FHWA), was the lead agency under NEPA. The Original Project was formally evaluated in 2012 as a joint CEQA-NEPA document (State Clearinghouse Number: 2011052028). The County and Caltrans determined that the proposed project would not have a significant impact on the environment and a Mitigated Negative Declaration (MND)/Finding of No Significant Impact (FONSI) was approved. Specific to the County’s actions, the Original Project, associated General Plan Conformity Determination (GPC 11-09) and IS/MND were approved by the Planning Commission on January 24, 2013. The 2012 IS/MND/EA is included in Exhibit B; and the January 24, 2013 Planning Commission Staff Report is included in Exhibit C.
The Original Project evaluated in 2012 did not consider nighttime construction. However, the County now proposes a modification to the Original Project to accommodate nighttime construction until 8:00 p.m. (herein referred to as the Modified Project). This proposed change constitutes a modification of the Original Project that was not previously fully evaluated and necessitates subsequent environmental review/documentation under CEQA and NEPA.
In accordance with CEQA Guidelines Sections 15162-15164, the County (with the assistance of consultants LSA and Associates), prepared an Addendum to the 2012 IS/MND/EA to analyze impacts of the Modified Project. As described further below, the Addendum concludes that the Modified Project would not result in any new or substantially more adverse significant effects or require any new mitigation measures not identified in the original IS/MND. Caltrans completed an analogous NEPA review for the EA through a revalidation study (June 2025) and Finding of No Significant Impact (FONSI) for the nighttime construction, included here in Exhibit D.
Zoning Ordinance Section 64.1, states that the Board of Supervisors may certify, recertify or otherwise modify any decision concerning the California Environmental Quality Act for a publicly initiated project. “Publicly initiated project” being undertaken by any public agency under the jurisdiction of the Board of Supervisors, including but not limited to public works construction and related activities.
Staff recommends that the Board adopt the Addendum (Exhibit A) to Initial Study with Mitigated Negative Declaration/Environmental Assessment (IS/MND/EA) originally approved in 2012 for the South Main Street and Soda Bay Road Widening and Bike Lanes Project.
PROJECT SUMMARY
A summary of the project is below. Please refer to the Addendum in Exhibit A, which includes a “redlined” project description, for more information.
The South Main Street and Soda Bay Road Widening and Bike Lanes Project consists of a 0.5-mile segment of South Main Street, from the Lakeport city limits to the State Route (SR) 175 extension, and a 0.75-mile segment of Soda Bay Road extending south from SR-175 to approximately 0.1 mile west of Manning Creek. The project would rehabilitate deficient pavement along the roadway corridor and improve roadway surface drainage. The roadway’s two existing through-traffic lanes would be widened to 12 feet to accommodate a new continuous 12-foot-wide center turning lane, and 8-foot-wide paved shoulders would be constructed to also serve as a Class II bicycle facility. A slight horizontal curve correction would be constructed at the existing curve of Soda Bay Road, approximately 0.45 mile south of the SR-175 intersection. The curve radius would be increased from 230 feet to 550 feet to improve safety.
The existing average width of the paved roadway is approximately 24 feet. The proposed near-term three-lane roadway expansion project will provide a pavement width of approximately 52 feet. Earthwork for the road widening would consist mostly of fill work, with a small amount of grading to contour driveway intersections and portions of the interior curve of Soda Bay Road Other road work would consist of painting lines and installing signage and lighting.
Utilities. Above-ground utility lines would be relocated underground, and utility poles along both sides of the roadway would be removed. A new utility trench for telephone, television, and electric power providers would be constructed parallel to the west side of South Main Street and Soda Bay Road along with drainage culvert undercrossings and utility vaults. In cooperation with the City of Lakeport (City), the project may include extension of the existing South Main Street water main. Assuming that appropriate funding is secured, it is anticipated that the planned water main extension would be included as part of the road improvements project. No water service connections would be established as part of the proposed project; however, fire hydrants may be installed in conjunction with the water main extension.
Three concrete box culverts would be extended and/or expanded, and one round concrete pipe and one concrete box culvert would be removed and rebuilt at a new location within the project right-of-way (ROW). In some locations, ditches would be constructed or reconstructed as water quality treatment swales. Impervious surface flows would be treated in bioswales in accordance with the post-construction requirements of the State Water Resources Control Board Construction General Permit.
ROW Acquisitions. ROW acquisitions are required to accommodate the roadway widening, cut/fill embankments, drainage facilities, and utility improvements. The existing County and City ROW corridor is approximately 60 feet wide and varies slightly in width from parcel to parcel along the route because of existing prescriptive ROW easements. The proposed project would require up to 80 feet of ROW to accommodate the near-term three-lane expansion and a possible future five-lane expansion.
Construction. Temporary construction easements would be needed to complete roadway construction, to match the new driveway entrances into the existing driveways, and to connect some of the utility and drainage improvements to existing facilities. Staging areas may be located in the paved Lakeport Auto Movies Theatre parking lot at 52 Soda Bay Road and/or in a paved and fenced lot immediately south of the Jack in the-Box restaurant at SR-175, assuming that permission is received from the property owners.
Noise and Traffic Avoidance Minimization Measures. Project construction would typically occur during daytime hours between 7:00 a.m. and 7:00 p.m. on weekdays, and between 8:00 a.m. and 7:00 p.m. on weekends. Additional construction may occur during evening hours (up to 8:00 p.m.) to maintain vehicle access throughout the project corridor and to businesses along the alignment, consistent with the following avoidance and minimization measures:
• Construction activities would be limited only to those activities, such as utility trench/vault or box culvert installation, that would otherwise prohibit through traffic and access for residences or businesses if conducted during the day. The only currently anticipated nighttime construction activity located near an existing residence would be a culvert replacement just west of 110 Soda Bay Road.
• A single lane of traffic, with flaggers to help control two-way traffic, would be maintained at all times unless a practical detour is available. Traffic control would be limited to 500 feet from any active construction area.
• No pile driving, rock drilling, or utility pole installation or removal activities would occur between the hours of 7:00 p.m. and 7:00 a.m. on weekdays and between 7:00 p.m. and 8:00 a.m. on weekends.
• No nighttime construction would occur within the specified construction avoidance areas located in the immediate vicinity of noise-sensitive receptors, such as residences, as specified on Figure 1 within the Addendum (and from the Nighttime Construction Noise Memorandum (LSA 2016)).
• For any nighttime construction activities within 200 feet of a construction avoidance area, as specified on Figure 1 of the Addendum (from the Nighttime Construction Noise Memorandum), construction equipment and noise sources would be shielded with a temporary noise barrier consisting of heavy vinyl noise curtain material (e.g., Sound Seal BBC 13-2 or equivalent).
• Nighttime construction would be limited to no more than four (4) consecutive nights, which is the maximum work duration anticipated for expected discrete overnight construction activities.
• The Lake County Public Works Department would establish a procedure for coordination with the adjacent noise-sensitive uses so that construction activities can be scheduled to minimize noise disturbance. A phone number for complaints would be posted at the construction site, and all complaints would be investigated (including noise monitoring of construction activities, as necessary) and addressed.
Traffic Management Plan. The proposed project would require temporary lane closures during construction that could cause slight delays and additional queuing of vehicle traffic, emergency services, public transit, and bicyclists, as well as temporary parking reductions. Temporary lane closures would be necessary in order to underground the utilities along the project alignment. The existing utility poles prevent the widening of the road. Flaggers would manage traffic during temporary lane closures via a two-way traffic control. As described in Section 2.1.4 of the IS/MND/EA, a detailed Traffic Management Plan (TMP) would be included as part of the contractor’s specification package to manage temporary construction delays due to one-lane traffic controls. The TMP would address all traffic-related aspects of construction, including, but not limited to: traffic handling during each stage of construction, emergency service provider access, pedestrian safety/access, and bicycle safety/access. A component of the TMP would involve public dissemination of construction-related information through notices to the neighborhoods, press releases, and/or the use of changeable message signs. No roadway or driveway access to residences or businesses is expected to be blocked during construction of the project.
Project Schedule. The utility undergrounding will occur in late spring 2026 at the earliest, with road work to follow, for a proposed completion of winter 2027. The project is anticipated to be implemented in two phases, based on available funding, which is likely to result in construction completion for the second phase being delayed.
Figure 1, Vicinity Map
Source: Lake Couty GIS
ANALYSIS OF POTENTIAL ENVIRONMENTAL EFFECTS
CEQA Guidelines (Sections 15162 and 15164) state that an Addendum to a previously adopted IS/MND may be prepared if some changes or additions to the environmental evaluation of a project are necessary but none of the following occurs:
(1) There are no substantial changes in the project which require major revisions to the IS/MND or a substantial increase in the severity of previously identified significant effects;
(2) There are no substantial changes with respect to the circumstances under which the project is undertaken which require major revisions to the IS/MND; or
(3) No new information of substantial importance, which could not have been known with the exercise of reasonable diligence at the time of IS/MND adoption, shows any of the following:
(a) The project will have one or more significant effects not discussed in the previous IS/MND;
(b) Significant effects previously examined will be substantially more severe than shown in the previous IS/MND;
(c) Mitigation measures or alternatives previously found not to be feasible would in fact be feasible and would substantially reduce one or more significant effects of the project, but the project proponents decline to adopt the mitigation measure or alternative; or
(d) Mitigation measures or alternatives which are considerably different from those analyzed in the previous IS/MND would substantially reduce one or more significant effects on the environment, but the project proponents decline to adopt the mitigation measure or alternative.
According to CEQA Guidelines Section 15164(c) and (d), an addendum need not be circulated for public review but can be included in or attached to the final EIR or adopted negative declaration, but the decision-making body shall consider the addendum with the final EIR or adopted negative declaration prior to making a decision on the project.
In accordance with the aforementioned regulations, the Addendum evaluates whether implementation of the Modified Project would result in any new significant impacts or substantially more severe impacts than identified in the IS/MND prepared for the Original Project. Some CEQA topics have been updated or modified, in compliance with current CEQA regulations, since the IS/MND was prepared for the Original Project. Additionally, technical analyses prepared for the Original Project have been updated for the Modified Project (see attachments to the Addendum in Exhibit A). The discussion below includes a summary of noise impacts that are analyzed within the Addendum. Refer to the Addendum for more information and for the analyses of the remaining CEQA topics.
Noise. Section 2.2.6 of the IS/MND/EA analyzed noise impacts associated with the Original Project. The IS/MND/EA identified two potential temporary, short-term, construction-related noise impacts that would occur during construction: (1) noise generated by construction crew commutes and transportation of construction equipment and materials to the project site; and (2) noise generated by construction equipment on the project site. Construction-period noise would be short term and intermittent, and subject to measures that restrict the hours of construction and impose maintenance and operation restrictions on construction equipment. Avoidance and minimization measures identified in the IS/MND/EA, consisting of BMPs related to operation and placement of construction equipment to minimize construction-related noise, would be implemented to meet the City and County noise standards.
A Nighttime Construction Noise Memorandum (LSA 2016) (Attachment B to the Addendum) was prepared for the Modified Project to analyze the impacts of nighttime construction on noise-sensitive receptors (i.e., residential uses located within 100 feet of the project roadway segments). Nighttime construction associated with the Modified Project would only occur outside of the “Nighttime Construction Avoidance Areas” as shown on Figure 1 of the Addendum (Exhibit A) and Noise Memo. The minimum distance from any sensitive noise receptor to a nighttime construction area would be between 115-340 feet.
As described in the IS/MND/EA, the worst-case combined construction noise level would be 91 dBA Lmax at 50 feet from the active construction area. Based on FHWA documentation of best practices for calculating the estimated reduction from noise reduction measures, a 5 dBA reduction can be achieved for a properly installed manufacturer-recommended muffler (FHWA 2006). With the implementation of this minimization measure from the IS/MND/EA, nighttime construction noise levels would be reduced to 86 dBA Lmax (the maximum sound level recorded during a specific measurement period, measured in decibels) at 50 feet from the construction area, which is consistent with the Caltrans Standard Specifications, Section 14-8, Noise and Vibration.
As explained in the 2016 Noise Memo, for any nighttime construction conducted within 200 feet of a construction avoidance area, as shown on Figure 1 of the Addendum and Noise Memo, a portable temporary noise barrier consisting of heavy vinyl noise curtain material (e.g., Sound Seal BBC 13-2 or equivalent) would be used to shield nighttime construction equipment from the nearest sensitive noise receptor. Based on FHWA documentation, a 5 dBA noise reduction can be achieved with this type of barrier. With implementation of this new noise reduction measure and the previously specified avoidance and minimization measure related to properly installed manufacturer-recommended mufflers, nighttime construction noise levels would be further reduced to 81 dBA Lmax at 50 feet from the construction area, which is below the 86 dBA Lmax at 50 feet Caltrans specification.
With the use of properly installed mufflers and temporary noise barriers within 200 feet of a nighttime construction avoidance area, the estimated maximum nighttime construction noise level at an existing residence would be 75 dBA Lmax, which is based on the closest possible distance that a residence may be located relative to an adjacent construction area (i.e., 100 feet).
As Lead Agency, the County has determined that the updated noise avoidance and minimization measures incorporated into the project will not result in substantial changes to the circumstances under which the project will be undertaken, new significant environmental effects, or a substantial increase in the severity of previously identified significant effects, as identified under Section 15162 of the State CEQA Guidelines.
CEQA Conclusion. The Modified Project, which involves nighttime construction, would have the same project footprint, use the same construction techniques, and implement the avoidance and minimization measures and mitigation identified in the IS/MND/EA. The Modified Project would not trigger any of the conditions listed under the CEQA Framework for Addendum section of this Addendum, requiring additional environmental documentation. Thus, this Addendum satisfies the requirements of State CEQA Guidelines Sections 15162 and 15164. The changes to the project to accommodate nighttime construction would not introduce new significant environmental effects, substantially increase the severity of previously identified significant environmental effects, or demonstrate that mitigation measures or alternatives previously found not to be feasible would in fact be feasible. The proposed changes that would be implemented as part of the Modified Project would not alter the findings in the IS/MND. In addition, no change has occurred with respect to the circumstances surrounding the proposed project that would cause new or substantially more severe significant environmental effects than identified in the IS/MND, and no new information has become available that shows that the project would cause significant environmental effects not already analyzed in the IS/MND.
Furthermore, as Lead Agency, the County has determined that the minor avoidance and minimization measure clarifications for aesthetics and biological resources, updated information related to regulatory framework changes, and the updated noise avoidance and minimization measures for nighttime construction will not result in substantial changes to the circumstances under which the project will be undertaken, new significant environmental effects, or a substantial increase in the severity of previously identified significant effects, as identified under Section 15162 of the State CEQA Guidelines. The County, as Lead Agency, has agreed to implement the updated avoidance and minimization measures contained herein when carrying out the Modified Project. Therefore, no further environmental review is required beyond this Addendum to the IS/MND.
FINDINGS FOR APPROVAL
Zoning Ordinance Section 64.1, the Board of Supervisors may certify, recertify or otherwise modify any decision concerning the California Environmental Quality Act for a publicly initiated project. “Publicly initiated project” undertaken by any public agency under the jurisdiction of the Board of Supervisors, including but not limited to public works construction and related activities.
According to CEQA Guidelines Section 15164(c) and (d), an addendum need not be circulated for public review but can be included in or attached to the final EIR or adopted negative declaration, but the decision-making body shall consider the addendum with the final EIR or adopted negative declaration prior to making a decision on the project.
1. The Addendum to the Initial Study with Mitigated Negative Declaration for the South Main Street and Soda Bay Road Widening and Bike Lanes Project (SCH No. 2011052028) has been prepared in compliance with CEQA Sections 15162 and 15164.
2. There are no substantial changes in the project which require major revisions to the IS/MND or a substantial increase in the severity of previously identified significant effects.
3. There are no substantial changes with respect to the circumstances under which the project is undertaken which require major revisions to the IS/MND.
4. No new information of substantial importance, which could not have been known with the exercise of reasonable diligence at the time of IS/MND adoption, shows any of the criteria noted in CEQA Section 15166, subsections a through d.
5. As Lead Agency, the County has determined that the minor avoidance and minimization measure clarifications for aesthetics and biological resources, updated information related to regulatory framework changes, and the updated noise avoidance and minimization measures for nighttime construction will not result in substantial changes to the circumstances under which the project will be undertaken, new significant environmental effects, or a substantial increase in the severity of previously identified significant effects, as identified under Section 15162 of the State CEQA Guidelines.
6. With implementation of avoidance and minimization measures, as well as mitigation measures identified in the IS/MND/EA and Addendum, all impacts can be reduced to less than significant levels.
7. The Addendum concludes that the proposed project modifications do not result in new or more severe significant environmental effects and therefore do not require preparation of a subsequent MND or EIR.
8. As the Lead NEPA Agency, Caltrans has completed a separate NEPA revalidation (June 18, 2025) for the Modified Project and determined that the project would result in a Finding of No Significant Impact (FONSI), and that subsequent review is not required.
Staff recommends the Board of Supervisors:
Adopt the Addendum (Exhibit A) to Initial Study with Mitigated Negative Declaration for the South Main Street and Soda Bay Road Widening and Bike Lanes Project, as modified, based on the findings in the Board memo dated November 18, 2025.