The Draft IS/ND's analysis of project impacts identified potentially less than significant impacts which will be avoided by adhering to the following Project Features (PFs) and Avoidance and Minimization Measures (AMMs):

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• PF-AES-1, Minimize Vegetation Impacts. Impacts on vegetation would be minimized to the greatest extent possible during construction. Vegetation to remain would be protected from construction activities through the installation of temporary fencing when it is close to construction work.

• PF-AES-2, Temporary Fencing. Temporary fencing would be used to protect the roots and canopies of nearby trees.

• PF-AES-3, Staging Areas Positioning. Construction materials and equipment would be stored in a staging area beyond direct view of the motoring public and residential properties to the extent feasible.

• PF-AES-4, Architectural Treatment. The need for the architectural treatment of proposed Project elements such as a retaining wall should be investigated by the Caltrans Office of Landscape Architecture during the plans, specifications, and estimates phase of design and incorporated as appropriate. This may include coloring or other treatments to new concrete paving or retaining walls, anti-graffiti coatings, and other elements.

• PF-AES-5, Tree Trimming. Where the pruning of trees is required to accommodate construction operations, pruning would be performed under the supervision of a certified arborist.

• PF-AQ-1, Control Measures for Construction Emissions of Fugitive Dust. Dust control measures would be implemented to minimize airborne dust and soil particles generated from graded areas. For disturbed soil areas, the use of an organic tackifier to control dust emissions would be included in the construction contract. Watering guidelines would be established by the contractor and approved by the Caltrans Resident Engineer. Any material stockpiled during construction would be watered, sprayed with tackifier, or covered to minimize dust production and wind erosion.

• PF-AQ-2, Construction Vehicles and Equipment. Construction vehicles and equipment would be maintained and tuned in accordance with manufacturer’s specifications. In addition, solar-powered traffic control lights would be used if feasible.

• PF-AQ-3, Minimize Idling. Idling times would be minimized either by shutting equipment off when not in use or reducing the maximum idling time to 5 minutes.

• PF-AQ-4, Recycle Waste and Materials. If practicable, non-hazardous waste and excess material would be recycled. If recycling is not practicable, dispose of material according to applicable regulations.

• PF-BIO-1, Environmentally Sensitive Areas. Before starting construction, ESAs (defined as areas containing sensitive habitats adjacent to or within construction work areas for which physical disturbance is not allowed) would be clearly delineated as needed using high-visibility orange fencing. The ESA fencing would remain in place at each location until work at that location is complete and would prevent construction equipment or personnel from entering sensitive habitat areas. The ESA fencing would also serve to delineate the Project footprint in which all construction activity would occur. The final Project plans would depict the locations where ESA fencing would be installed and how it would be assembled and constructed. The ESA fencing would be removed following completion of construction activities.

• PF-BIO-2, Construction Site Management Practices. The following site restrictions would be implemented to avoid or minimize potential effects on listed species and their habitats:

1. Project-related vehicle traffic would be restricted to established roads and construction areas. The speed limit of 15 miles per hour within the Project footprint and on unpaved and paved areas would be enforced to reduce dust and excessive soil disturbance.

2. Project personnel would be required to comply with current guidance governing vehicle use, speed limits, fire prevention, and other hazards.

3. Construction access, staging, storage, and parking areas would use existing maintenance vehicle pullouts, existing paved areas, gravel shoulder backing, and disturbed areas within the Project limits. Staging and storage areas would be located at least 50 feet from wetlands, the ordinary high-water mark of jurisdictional waters, a concentrated flow of stormwater, a drainage course, or an inlet, unless additional containment efforts are used. Access routes and boundaries of the footprint would be clearly marked prior to initiating construction activities and would be limited to the extent necessary to construct the proposed Project. Only approved areas clearly delineated in the plans may be used for staging and storage.

4. Any borrow material must be certified non-toxic and free of weeds to the maximum extent possible.

5. All food-related trash items such as wrappers, cans, bottles, and food scraps would be disposed of in closed containers and removed at least once daily from the Project footprint.

6. All pets would be prohibited from entering the Project area during construction to prevent harassment of, injury to, or mortality of sensitive species.

7. Firearms would be prohibited within the Project site, except for those carried by authorized security personnel or local, state, or federal law enforcement officials.

• PF-BIO-3, Vegetation Removal. Vegetation would be cleared only where necessary and would be cut above soil level, except in areas that would be permanently affected or excavated. This would allow plants that reproduce vegetatively to resprout after construction. Vegetation removed by construction operations within the Project limits would be replaced according to Caltrans policy. Appropriate native species would be used to the maximum extent possible. Shrubs and groundcover would be selected for drought tolerance and disease resistance. Mulch would be applied to planted areas to reduce weed growth, conserve moisture, and minimize maintenance operations.

• PF-BIO-4, Replant, Reseed, and Restore Disturbed Areas. Temporarily disturbed areas would be restored to the maximum extent practicable. Exposed slopes and bare ground would be reseeded with native vegetation or other methods to stabilize and prevent erosion. Where disturbance includes the removal of trees and woody shrubs, native species would be replanted, based on the local species composition.

• PF-BIO-5, Night Lighting. Nighttime work would be avoided to the maximum extent practicable. For unavoidable nighttime work, all lighting would be shielded and directed downward toward the active construction area to avoid exposing nocturnal wildlife to excessive glare.

• PF-BIO-6, Invasive Weed Control. To reduce the spread of invasive, non-native plant species and minimize the potential decrease of palatable vegetation for wildlife species, Caltrans would comply with Executive Order 13112. This order is provided to prevent the introduction of invasive species and provide for their control to minimize the economic, ecological, and human health effects. If noxious weeds are disturbed or removed during construction-related activities, the contractor would be required to contain the plant material associated with these noxious weeds and dispose of them in a manner that would not promote the spread of the species. The contractor would be responsible for obtaining all permits, licenses, and environmental clearances for the proper disposal of materials. Areas subject to noxious weed removal or disturbance would be replanted with fast-growing native grasses or a native erosion control seed mixture. Where seeding is not practical, the target areas within the Project footprint would be covered to the extent practicable with heavy black plastic solarization material until the end of the Project.

• PF-CUL-1, Unanticipated Archaeological Discovery. If cultural materials are discovered during construction, all earthmoving activity within and around the immediate discovery area would be diverted until a qualified archaeologist can assess the nature and significance of the find in consultation with the State Historic Preservation Officer.

• PF-CUL-2, Unanticipated Human Remains Discovery. If human remains are discovered, State Health and Safety Code Section 7050.5 states that further disturbances and activities would cease in any area or nearby area suspected to overlie the remains and the county coroner would be contacted. Pursuant to Public Resources Code Section 5097.98, if the remains are thought to be Native American, the coroner would notify the Native American Heritage Commission, which would then notify the Most Likely Descendant. At that time, the person who discovered the remains would contact the Environmental Senior and Professionally Qualified Staff, who would work with the Most Likely Descendant to ensure respectful treatment and disposition of the remains. Further provisions of Public Resources Code Section 5097.98 would be followed, as applicable.

• PF-HAZ-1, Preliminary Site Investigations. A preliminary site investigation for aerially deposited lead, agricultural chemicals, and potential hazardous materials concerns related to soil and groundwater would be conducted during the Project design phase to investigate soil within Project limits proposed to be excavated, encountered, or disturbed and managed. The findings of the preliminary site investigation would be used to evaluate soil and groundwater handling practices, construction worker health and safety concerns, and soil and groundwater reuse and disposal options. If hazardous materials are identified during the preliminary site investigation, additional investigation could be required. The results of the site investigation would determine the special provisions to be used in the final design package. The site investigation report would be included as part of the information handout made available as a part of the final design package.

• PF-NOI-1, Public Outreach. Public outreach would be required before Project construction and throughout Project construction to update residents, businesses, and others with upcoming Project activities and timeframe. Public outreach could entail sending notices to nearby residents, notifying the City, and posting a notice on the Project website.

• PF-NOI-2, Construction Noise Levels. The following measures would be implemented to reduce noise levels during construction where feasible:

  • Any operation exceeding 86 decibels (A-weighted) would not be allowed at nighttime from 9:00 p.m. to 6:00 a.m.

  • Schedule noisy operations within the same timeframe where feasible. The total noise level would not be significantly greater than the level produced if operations are performed separately.

  • If feasible, use solar or electricity as a power source instead of diesel generators.

  • Avoid unnecessary idling of internal combustion engines.

  • Locate all stationary noise-generating construction equipment as far as practicable from noise-sensitive receptors or provide baffled housing or sound aprons for equipment when sensitive receptors adjoin or are near a Project construction area.

  • Equip all internal combustion engine-driven equipment with manufacturer-recommended intake and exhaust mufflers that are in good condition and appropriate for the equipment.

  • Use “quiet” air compressors and other “quiet” equipment where such technology exists.

  • No construction equipment would be delivered and dropped off before 6:00 a.m.

  • Maintain all internal combustion engines properly to minimize noise generation.

• PF-WQ-1, Construction and Implementation of Best Management Practices. Erosion control best management practices (BMPs) would be included in the final Project plans, and Standard Special Provisions would be included in the final construction package to comply with the conditions of the Caltrans National Pollutant Discharge Elimination System permit. The Caltrans BMP Guidance Handbook (Caltrans 2017)  would provide guidance for provisions to be included in the construction contract for measures to protect environmentally sensitive areas and avoid or minimize stormwater and non-stormwater discharges. Construction BMPs for stormwater may include, but are not limited to, the following:

  • Construction tracking control practices

  • Job site management

  • Sediment control (fiber rolls and silt fencing)

  • Waste management and materials pollution control

  • Materials stockpile management

  • Dust and wind erosion controls

  • Non-stormwater management

  • Water quality monitoring

  • Maintaining and tuning construction vehicles and equipment approximately 50 feet away from known water features

  • Locating designated fueling areas approximately 50 feet from downslope drainage facilities

• PF-WQ-2, Water Pollution Control Program. A Water Pollution Control Program would be prepared by the contractor and approved by Caltrans, pursuant to the 2018 Caltrans Standard Specifications Section 13, Water Pollution Control, and the Caltrans Water Pollution Control Program Preparation Manual (Caltrans 2021b).  The Water Pollution Control Program would be implemented prior to the beginning of construction.

• PF-WQ-3, Temporary Stream Diversions. Temporary stream diversions would be used when necessary for culvert replacements. If needed, stream diversions would be determined during the design phase of the Project.

• PF-WQ-4, Permanent BMPs. To minimize and avoid potential post-construction impacts on water quality, the Project would consider design pollution prevention BMPs. Design pollution prevention BMPs would be used to minimize runoff, maximize infiltration, maximize vegetation (depending on the location), and reduce erosion.

• PF-TRF-1, Traffic Management Plan. A Traffic Management Plan would be prepared prior to the beginning of construction to minimize impacts on the public while traveling on SR 131 and ensure their safety. Lane closures and traffic control would maintain traffic operations throughout the Project footprint. Temporary traffic barriers or traffic cones would be used to separate the open lanes from the closed lanes.

• AMM-AES-1, Staging Areas Impact Reduction. Staging areas would not be located where they require the removal of vegetation or result in ground compaction affecting tree roots.

• AMM-AES-2, Project Coordination. Design and construction related to an ongoing or planned project, such as the local Hawthorne Undergrounding Utility Project and Caltrans Bike Plan project, should be coordinated with the Town of Tiburon, and the designers and contractors involved. Additional avoidance and minimization measures, as appropriate, should be identified and implemented.

• AMM-AES-3, Erosion Control. Application of erosion control seeding and similar measures would be made to areas of disturbance that are beyond paved areas.

• AMM-AES-4, Night Lighting and Glare. Directional lighting and shielding would be maintained for all traffic, roadway, or construction lights installed or used for the Project.

• AMM-BIO-1, Worker Environmental Awareness Training. Prior to the start of construction, a biologist would provide a training session for all work personnel to identify any sensitive species that may be in the area, their basic habits, how they may be encountered in their work area, and procedures to follow when they are encountered. Any personnel joining the work crew later would receive the same training before beginning work. Upon completion of the education program, employees would sign a form stating they attended the program and understand all protection measures. A pamphlet that contains images of sensitive species that may occur within the Project, notes key avoidance measures, and provides employee guidance would be given to each person who completes the training program.

• AMM-BIO-2, Pre-construction Nesting Bird Surveys. If Project activities occur between February 1 and September 30, then a pre-construction survey would be conducted for nesting birds no more than 3 days before construction. If active nests are found, then an appropriate buffer would be established, and the nest would be monitored for compliance with the Migratory Bird Treaty Act and CFGC Section 3503.

• AMM-BIO-3, Active Nest Buffer. If an active bird nest is found during construction activities, then the following ESA buffers would be established:

  • If an active raptor nest is observed, a 300-foot ESA buffer would be implemented to avoid affecting the young until they have fledged.

  • If an active nest of non-raptor migratory birds is observed, a 50-foot ESA buffer would be implemented to protect the young until they have fledged, or as otherwise determined by consultation with CDFW regarding appropriate action to comply with the Migratory Bird Treaty Act and CFGC Section 3503.

• AMM-BIO-4, Work Period in Dry Weather Only. Work would only be conducted during periods of dry weather. Forecast precipitation would be monitored. When 0.25 inch or more of precipitation is forecast to occur, work would stop before precipitation commences. No Project activities would be started if their associated erosion control measures cannot be completed prior to the onset of precipitation. After any storm event, all sites currently under construction and all sites scheduled to begin construction within the next 72 hours would be inspected for erosion and sediment problems, and corrective action would be taken as needed. In addition, 72-hour weather forecasts from National Weather Service would be consulted, and work would not start back up until runoff ceases and there is a less than 50% forecast for precipitation for the following 24-hour period.

• AMM-BIO-5, Prevent Inadvertent Entrapment. To prevent inadvertent entrapment of animals during construction, all excavated, steep-walled holes or trenches more than 1 foot deep would be covered at the close of each working day with plywood or similar materials or provided with one or more escape ramps constructed of earthen fill or wooden planks at an angle no greater than 30 degrees. Before such holes or trenches are filled, they would be thoroughly inspected for trapped animals. Pipes, culverts, or similar structures stored in the Project footprint overnight would be inspected before they are subsequently moved, capped, or buried.

• AMM-CUL-1, Cultural Environmentally Sensitive Areas: Before starting construction, ESAs (defined as areas containing previously recorded archaeological sites located adjacent to or within construction work areas for which physical disturbance is not allowed) would be clearly delineated as needed using high-visibility orange fencing. The ESA fencing would remain in place at each location until work at that location is complete and would prevent construction equipment or personnel from entering these sensitive areas. The ESA fencing would also serve to delineate the Project footprint in which all construction activity would occur. The final Project plans would depict the locations where ESA fencing would be installed and how it would be assembled and constructed. The ESA fencing would be removed following completion of construction activities.

• AMM-CUL-2, Archaeological Monitoring. Caltrans is preparing an Archaeological Monitoring Plan to be implemented during construction. This will include establishing an archaeological monitoring area and having an archaeologist and tribal representative monitor job site activities within the archaeological monitoring area to reduce the Project’s impacts to the resource within the Project limits. No work can be conducted within the archaeological monitoring area unless the archeological monitor is present. Reference Caltrans Standard Specification 14-2.03.

• AMM-CUL-3, Post-review Discovery Plan: If archaeological resources cannot be avoided, a Post-review Recovery Plan will be implemented by a qualified archaeologist for the significant archaeological site that is directly affected. Data recovery will only occur in the portion of the site being directly affected.

• AMM-GEO-1, Unanticipated Paleontological Resources. As outlined in Standard Specifications 14-7.03, Discovery of Unanticipated Paleontological Resources, if unanticipated paleontological resources are discovered at the job site in the native Pleistocene terrace deposits, the following measures would be implemented:

1. Stop all work within a 60-foot radius of the discovery.

2. Secure the area.

3. Notify the Project engineer.

The Caltrans Department of Geology Services would investigate the discovery and modify the dimensions of the secured area if needed. Paleontological resources would not be moved or taken from the job site until appropriate coordination and consultation has been completed. Work within the radius of discovery would not resume until authorized by a qualified paleontologist.

• AMM-NO1-1, Noise Control and Monitoring. The Contract Specifications would include a Special Provision requiring Noise Monitoring and Control, which would include providing public outreach or a communication plan for residents, businesses, and others regarding upcoming construction-related activities and Project schedule.

• AMM-UT-1, Utility Notifications. Caltrans would notify all affected utility companies of the construction schedule for the Project so that relocations can be conducted by each utility company as necessary prior to the start of construction.