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HomeMy WebLinkAbout2023-08-23 Rail Agenda PacketRAIL COMMITTEE Special Meeting Wednesday, August 23, 2023 Community Meeting Room & Hybrid 2:30 PM Rail Committee meetings will be held as “hybrid” meetings with the option to attend by teleconference/video conference or in person. To maximize public safety while still maintaining transparency and public access, members of the public can choose to participate from home or attend in person. Information on how the public may observe and participate in the meeting is located at the end of the agenda. Masks are strongly encouraged if attending in person. The meeting will be broadcast on Cable TV Channel 26, live on YouTube https://www.youtube.com/c/cityofpaloalto, and streamed to Midpen Media Center https://midpenmedia.org. VIRTUAL PARTICIPATION CLICK HERE TO JOIN (https://cityofpaloalto.zoom.us/j/86388142528) Meeting ID: 863 8814 2528    Phone: 1(669)900‐6833 PUBLIC COMMENTS Public comments will be accepted both in person and via Zoom for up to three minutes or an amount of time determined by the Chair. All requests to speak will be taken until 5 minutes after the staff’s presentation. Written public comments can be submitted in advance to city.council@CityofPaloAlto.org and will be provided to the Council and available for inspection on the City’s website. Please clearly indicate which agenda item you are referencing in your subject line. PowerPoints, videos, or other media to be presented during public comment are accepted only by email to city.clerk@CityofPaloAlto.org at least 24 hours prior to the meeting. Once received, the  Clerk will have them shared at public comment for the specified item. To uphold strong cybersecurity management practices, USB’s or other physical electronic storage devices are not accepted. CALL TO ORDER PUBLIC COMMENT  Members of the public may speak to any item NOT on the agenda.  VERBAL UPDATE ON INTERAGENCY ACTIVITIES A.Caltrain B.VTA C.City Staff ACTION ITEMS 1.Review and Discuss New Grant Awards and Requirements from the Federal Railroad Administration and California State Transportation Agency for Grade Separation Projects, and Direct Staff to Develop Funding Agreements 2.Rail Committee to Review the Preliminary Geotechnical Feasibility Study Memorandum prepared by the Consultant for Grade Separation Projects at Churchill Avenue, Meadow Drive, and Charleston Road STUDY SESSION FUTURE MEETINGS AND AGENDAS Members of the public may not speak to the item(s) ADJOURNMENT PUBLIC COMMENT INSTRUCTIONS Members of the Public may provide public comments to teleconference meetings via email, teleconference, or by phone. 1. Written public comments may be submitted by email to city.council@cityofpaloalto.org. 2. For in person public comments please complete a speaker request card located on the table at the entrance to the Council Chambers and deliver it to the Clerk prior to discussion of the item. 3. Spoken public comments using a computer or smart phone will be accepted through the teleconference meeting. To address the Council, click on the link below to access a Zoom‐based meeting. Please read the following instructions carefully. You may download the Zoom client or connect to the meeting in‐ browser. If using your browser, make sure you are using a current, up‐to‐date browser: Chrome 30 , Firefox 27 , Microsoft Edge 12 , Safari 7 . Certain functionality may be disabled in older browsers including Internet Explorer. Or download the Zoom application onto your smart phone from the Apple App Store or Google Play Store and enter in the Meeting ID below. You may be asked to enter an email address and name. We request that you identify yourself by name as this will be visible online and will be used to notify you that it is your turn to speak. When you wish to speak on an Agenda Item, click on “raise hand.” The Clerk will activate and unmute speakers in turn. Speakers will be notified shortly before they are called to speak. When called, please limit your remarks to the time limit allotted. A timer will be shown on the computer to help keep track of your comments. 4. Spoken public comments using a phone use the telephone number listed below. When you wish to speak on an agenda item hit *9 on your phone so we know that you wish to speak. You will be asked to provide your first and last name before addressing the Council. You will be advised how long you have to speak. When called please limit your remarks to the agenda item and time limit allotted. CLICK HERE TO JOIN    Meeting ID: 863‐8814‐2528   Phone: 1‐669‐900‐6833 Americans with Disability Act (ADA) It is the policy of the City of Palo Alto to offer its public programs, services and meetings in a manner that is readily accessible to all. Persons with disabilities who require materials in an appropriate alternative format or who require auxiliary aids to access City meetings, programs, or services may contact the City’s ADA Coordinator at (650) 329‐2550 (voice) or by emailing ada@cityofpaloalto.org. Requests for assistance or accommodations must be submitted at least 24 hours in advance of the meeting, program, or service.  1 Regular Meeting August 23, 2023 Materials submitted after distribution of the agenda packet are available for public inspection at www.cityofpaloalto.org/agendas RAIL COMMITTEESpecial MeetingWednesday, August 23, 2023Community Meeting Room & Hybrid2:30 PMRail Committee meetings will be held as “hybrid” meetings with the option to attend byteleconference/video conference or in person. To maximize public safety while still maintainingtransparency and public access, members of the public can choose to participate from home orattend in person. Information on how the public may observe and participate in the meeting islocated at the end of the agenda. Masks are strongly encouraged if attending in person. Themeeting will be broadcast on Cable TV Channel 26, live onYouTube https://www.youtube.com/c/cityofpaloalto, and streamed to Midpen MediaCenter https://midpenmedia.org.VIRTUAL PARTICIPATION CLICK HERE TO JOIN (https://cityofpaloalto.zoom.us/j/86388142528)Meeting ID: 863 8814 2528    Phone: 1(669)900‐6833PUBLIC COMMENTSPublic comments will be accepted both in person and via Zoom for up to three minutes or anamount of time determined by the Chair. All requests to speak will be taken until 5 minutesafter the staff’s presentation. Written public comments can be submitted in advance tocity.council@CityofPaloAlto.org and will be provided to the Council and available for inspectionon the City’s website. Please clearly indicate which agenda item you are referencing in yoursubject line. PowerPoints, videos, or other media to be presented during public comment are accepted only by email to city.clerk@CityofPaloAlto.org at least 24 hours prior to the meeting. Once received, the  Clerk will have them shared at public comment for the specified item. To uphold strong cybersecurity management practices, USB’s or other physical electronic storage devices are not accepted. CALL TO ORDER PUBLIC COMMENT  Members of the public may speak to any item NOT on the agenda.  VERBAL UPDATE ON INTERAGENCY ACTIVITIES A.Caltrain B.VTA C.City Staff ACTION ITEMS 1.Review and Discuss New Grant Awards and Requirements from the Federal Railroad Administration and California State Transportation Agency for Grade Separation Projects, and Direct Staff to Develop Funding Agreements 2.Rail Committee to Review the Preliminary Geotechnical Feasibility Study Memorandum prepared by the Consultant for Grade Separation Projects at Churchill Avenue, Meadow Drive, and Charleston Road STUDY SESSION FUTURE MEETINGS AND AGENDAS Members of the public may not speak to the item(s) ADJOURNMENT PUBLIC COMMENT INSTRUCTIONS Members of the Public may provide public comments to teleconference meetings via email, teleconference, or by phone. 1. Written public comments may be submitted by email to city.council@cityofpaloalto.org. 2. For in person public comments please complete a speaker request card located on the table at the entrance to the Council Chambers and deliver it to the Clerk prior to discussion of the item. 3. Spoken public comments using a computer or smart phone will be accepted through the teleconference meeting. To address the Council, click on the link below to access a Zoom‐based meeting. Please read the following instructions carefully. You may download the Zoom client or connect to the meeting in‐ browser. If using your browser, make sure you are using a current, up‐to‐date browser: Chrome 30 , Firefox 27 , Microsoft Edge 12 , Safari 7 . Certain functionality may be disabled in older browsers including Internet Explorer. Or download the Zoom application onto your smart phone from the Apple App Store or Google Play Store and enter in the Meeting ID below. You may be asked to enter an email address and name. We request that you identify yourself by name as this will be visible online and will be used to notify you that it is your turn to speak. When you wish to speak on an Agenda Item, click on “raise hand.” The Clerk will activate and unmute speakers in turn. Speakers will be notified shortly before they are called to speak. When called, please limit your remarks to the time limit allotted. A timer will be shown on the computer to help keep track of your comments. 4. Spoken public comments using a phone use the telephone number listed below. When you wish to speak on an agenda item hit *9 on your phone so we know that you wish to speak. You will be asked to provide your first and last name before addressing the Council. You will be advised how long you have to speak. When called please limit your remarks to the agenda item and time limit allotted. CLICK HERE TO JOIN    Meeting ID: 863‐8814‐2528   Phone: 1‐669‐900‐6833 Americans with Disability Act (ADA) It is the policy of the City of Palo Alto to offer its public programs, services and meetings in a manner that is readily accessible to all. Persons with disabilities who require materials in an appropriate alternative format or who require auxiliary aids to access City meetings, programs, or services may contact the City’s ADA Coordinator at (650) 329‐2550 (voice) or by emailing ada@cityofpaloalto.org. Requests for assistance or accommodations must be submitted at least 24 hours in advance of the meeting, program, or service.  2 Regular Meeting August 23, 2023 Materials submitted after distribution of the agenda packet are available for public inspection at www.cityofpaloalto.org/agendas RAIL COMMITTEESpecial MeetingWednesday, August 23, 2023Community Meeting Room & Hybrid2:30 PMRail Committee meetings will be held as “hybrid” meetings with the option to attend byteleconference/video conference or in person. To maximize public safety while still maintainingtransparency and public access, members of the public can choose to participate from home orattend in person. Information on how the public may observe and participate in the meeting islocated at the end of the agenda. Masks are strongly encouraged if attending in person. Themeeting will be broadcast on Cable TV Channel 26, live onYouTube https://www.youtube.com/c/cityofpaloalto, and streamed to Midpen MediaCenter https://midpenmedia.org.VIRTUAL PARTICIPATION CLICK HERE TO JOIN (https://cityofpaloalto.zoom.us/j/86388142528)Meeting ID: 863 8814 2528    Phone: 1(669)900‐6833PUBLIC COMMENTSPublic comments will be accepted both in person and via Zoom for up to three minutes or anamount of time determined by the Chair. All requests to speak will be taken until 5 minutesafter the staff’s presentation. Written public comments can be submitted in advance tocity.council@CityofPaloAlto.org and will be provided to the Council and available for inspectionon the City’s website. Please clearly indicate which agenda item you are referencing in yoursubject line.PowerPoints, videos, or other media to be presented during public comment are accepted onlyby email to city.clerk@CityofPaloAlto.org at least 24 hours prior to the meeting. Once received,the  Clerk will have them shared at public comment for the specified item. To uphold strongcybersecurity management practices, USB’s or other physical electronic storage devices are notaccepted.CALL TO ORDERPUBLIC COMMENT Members of the public may speak to any item NOT on the agenda. VERBAL UPDATE ON INTERAGENCY ACTIVITIESA.CaltrainB.VTAC.City StaffACTION ITEMS1.Review and Discuss New Grant Awards and Requirements from the Federal RailroadAdministration and California State Transportation Agency for Grade Separation Projects,and Direct Staff to Develop Funding Agreements2.Rail Committee to Review the Preliminary Geotechnical Feasibility Study Memorandumprepared by the Consultant for Grade Separation Projects at Churchill Avenue, MeadowDrive, and Charleston RoadSTUDY SESSIONFUTURE MEETINGS AND AGENDASMembers of the public may not speak to the item(s) ADJOURNMENT PUBLIC COMMENT INSTRUCTIONS Members of the Public may provide public comments to teleconference meetings via email, teleconference, or by phone. 1. Written public comments may be submitted by email to city.council@cityofpaloalto.org. 2. For in person public comments please complete a speaker request card located on the table at the entrance to the Council Chambers and deliver it to the Clerk prior to discussion of the item. 3. Spoken public comments using a computer or smart phone will be accepted through the teleconference meeting. To address the Council, click on the link below to access a Zoom‐based meeting. Please read the following instructions carefully. You may download the Zoom client or connect to the meeting in‐ browser. If using your browser, make sure you are using a current, up‐to‐date browser: Chrome 30 , Firefox 27 , Microsoft Edge 12 , Safari 7 . Certain functionality may be disabled in older browsers including Internet Explorer. Or download the Zoom application onto your smart phone from the Apple App Store or Google Play Store and enter in the Meeting ID below. You may be asked to enter an email address and name. We request that you identify yourself by name as this will be visible online and will be used to notify you that it is your turn to speak. When you wish to speak on an Agenda Item, click on “raise hand.” The Clerk will activate and unmute speakers in turn. Speakers will be notified shortly before they are called to speak. When called, please limit your remarks to the time limit allotted. A timer will be shown on the computer to help keep track of your comments. 4. Spoken public comments using a phone use the telephone number listed below. When you wish to speak on an agenda item hit *9 on your phone so we know that you wish to speak. You will be asked to provide your first and last name before addressing the Council. You will be advised how long you have to speak. When called please limit your remarks to the agenda item and time limit allotted. CLICK HERE TO JOIN    Meeting ID: 863‐8814‐2528   Phone: 1‐669‐900‐6833 Americans with Disability Act (ADA) It is the policy of the City of Palo Alto to offer its public programs, services and meetings in a manner that is readily accessible to all. Persons with disabilities who require materials in an appropriate alternative format or who require auxiliary aids to access City meetings, programs, or services may contact the City’s ADA Coordinator at (650) 329‐2550 (voice) or by emailing ada@cityofpaloalto.org. Requests for assistance or accommodations must be submitted at least 24 hours in advance of the meeting, program, or service.  3 Regular Meeting August 23, 2023 Materials submitted after distribution of the agenda packet are available for public inspection at www.cityofpaloalto.org/agendas Rail Committee Staff Report From: Philip Kamhi, Chief Transportation Official Meeting Date: August 23, 2023 TITLE Review and Discuss New Grant Awards and Requirements from the Federal Railroad Administration and California State Transportation Agency for Grade Separation Projects, and Direct Staff to Develop Funding Agreements EXECUTIVE SUMMARY The staff at the Office of Transportation in Palo Alto has been actively pursuing grant funding for Grade Separation Projects. Over the past year, staff have applied for various regional, state, and federal grant funding. Recently, in June, the Federal Railroad Administration (FRA) announced that they have selected the Palo Alto Grade Separation Projects at Churchill Avenue, Meadow Drive, and Charleston Road. The FRA has allocated $6 million for project development, which will provide funding towards the costs of completing the Preliminary Engineering and Environmental Phase for these crossings. Additionally, in early July, the City received notification from the California State Transportation Authority (CalSTA) that the Churchill Avenue Grade Crossing has been chosen for $23.7 million in funding towards the final design phase. In order to receive these grant funds, the City must comply with the requirements outlined by the grants, ensuring the timely completion of the designated phases. The grants impose an obligation on the City to adhere to the specified timelines for these phases. Therefore, staff is seeking Rail Committee review and discussion on grants’ obligations as staff initiates the process of developing agreements for funding the grade separation projects considering various elements of studies in progress for the selection of preferred alternatives. BACKGROUND AND DISCUSSION The project for grade separations at Churchill Avenue, Meadow Drive, and Charleston Road is currently in the pre-planning phase. The City has been working on developing various alternatives and studying them to determine the preferred option for the grade crossings. The next step for the City is to enter the planning phase, where the project will focus on creating Preliminary Engineering and Environmental Documents for the rail grade improvements at these crossings. Item 1 Item 1 Staff Report        Item 1: Staff Report Pg. 1  Packet Pg. 4 of 105  Over the past year, the City staff has actively sought federal and state grant funding opportunities for these grade separation projects. In 2022, the City applied for five different grant opportunities, including the BIL for Multimodal Project Discretionary Grant Opportunity (MPDG) such as INFRA and MEGA, the Rail Crossing Elimination (RCE) program by the Federal Railroad Administration (FRA), and the Major program Advancement Policy (MAP) opportunities through the Metropolitan Transportation Commission (MTC). Additionally, staff also applied for the Transit and Intercity Rail Capital Program (TIRCP), a State of California grant that supports grade separation projects. Recently on June 16, 2023 FRA announced the selected projects for funding through RCE Program. The City of Palo Alto’s grade separation projects at Churchill Avenue, Meadow Drive, and Charleston Drive was on this list to fund $6.0 Million towards the Preliminary Engineering and Environmental phase. The City plans to use matching funds of $14 Million from Santa Clara County Measure B Grade separation funding for this phase. Furthermore, on July 6, 2023, the California State Transportation Agency (CalSTA) announced the selection of the Churchill Avenue grade separation project for funding the final design phase, with an amount of $23.7 Million. These grants come with certain obligations for the City to meet specified timelines for the project phases. To receive the grant funds, the City must comply with the requirements outlined by the grants and ensure the timely completion of the designated phases. The City staff has submitted proposed timelines with grant applications for these phases, which are depicted in Figure 1 below. Figure 1: Proposed Project timelines submitted with grant requests Item 1 Item 1 Staff Report        Item 1: Staff Report Pg. 2  Packet Pg. 5 of 105  On July 27, 2023; Staff met with representatives of Federal Railroad Administration staff to discuss the project development and seek guidance on the next steps of developing agreement(s) for award of the RCE Program funding and allocation of these funds for the PE & Environmental Phase of the project. Based on these initial conversations, the FRA staff had indicated some flexibility, however, it is expected that the Preliminary Engineering and Environmental phase of the project should be completed within three years of the project agreement. With respect to the conceptual phase, the City Council has selected the preferred alternative and backup alternative for the grade separations at Churchill Avenue. However, for Meadow Drive and Charleston Road, the City Council has narrowed down the options to three alternatives: Trench, Hybrid, and Underpass. In order to proceed with the PE & Environmental Phase, the City will need to further narrow down the alternatives and choose a locally preferred option. Currently, several outstanding items need to be reviewed and addressed before the Rail Committee can evaluate these alternatives. These items include the evaluation of technical standards, a Preliminary Geotechnical Feasibility Study, the Caltrain Corridor Study assessing the limits of four tracking needs, Caltrain's review of conceptual plan alternatives and cost estimates, and additional studies to update the evaluation matrix according to the newly adopted Council Adopted Criteria. The estimated timelines for various activities of the grade separation project are depicted in Attachment A Therefore, staff is seeking Rail Committee review of the outstanding items for grant obligations in the acceptance of these grants. Based on the Rail Committee’s review, staff will work with granting agencies in developing agreements for funding these phases for grade separation projects. FISCAL/RESOURCE IMPACT The Rail Crossing Elimination Program, a federal grant, and the Transit Intercity Rail Capital Program Funding, a State of California Transportation Agency grant, are both highly competitive funding opportunities. Securing these grants is crucial for the fiscal funding of the grade separation projects in Palo Alto. ENVIRONMENTAL REVIEW The recommendation in this report does not constitute a project in accordance with the California Environmental Quality Act and is therefore not subject to environmental review. Item 1 Item 1 Staff Report        Item 1: Staff Report Pg. 3  Packet Pg. 6 of 105  STAKEHOLDER ENGAGEMENT The Rail Committee meetings are open to the public and therefore provide the community with opportunities to provide comments to the rail committee and the City. ATTACHMENTS Attachment A: Grade Separation Project Activities and Timeline Report #: 2307-1756 Item 1 Item 1 Staff Report        Item 1: Staff Report Pg. 4  Packet Pg. 7 of 105  Jan-Mar Apr-June July-Sept Oct-Dec Jan-Mar Apr-June July-Sept Oct-Dec Jan-Mar Apr-June July-Sept Oct-Dec Jan-Mar Apr-June July-Sept Oct-Dec Jan-Mar Apr-June July-Sept Oct-Dec Preliminary Geotechnical Feasibility Study Finalize Refinement of Underpass Alternatives Caltrain Review (Service Agreement) Additional Studies (Per Selection Criteria Update) eg. Traffic, Sustainability, Sea level, maintenance, etc. Caltrain Corridor Strategy Study ( 4 Tracking Limits) Caltrain Corridor Strategy Study (Other design elements) Council Preferred Alternative Needed (LPA Selection) Jan-Mar Apr-June July-Sept Oct-Dec Jan-Mar Apr-June July-Sept Oct-Dec Jan-Mar Apr-June July-Sept Oct-Dec Jan-Mar Apr-June July-Sept Oct-Dec Jan-Mar Apr-June July-Sept Oct-Dec Rail Crossing Elimination (FRA) Churchill, Meadow, Charleston ( PE & Env) $6.0 M Transit & Intercity Rail Capital Program (CalSTA) Churchill Avenue (Final Design) $23.7M Jan-Mar Apr-June July-Sept Oct-Dec Jan-Mar Apr-June July-Sept Oct-Dec Jan-Mar Apr-June July-Sept Oct-Dec Jan-Mar Apr-June July-Sept Oct-Dec Jan-Mar Apr-June July-Sept Oct-Dec Mega/Infra (Federal)Submission Timeline ( August 23, 2023)Meadow Charleston Final Design Section 190 (State)Anticipated in Oct 2023 (TBD) Other Federal grants Anticipated in 2024, 2025 2027 Current Project Activities Timeline Anticipated Information from Caltrain (Sept 2023) Anticipated Information from Caltrain (December 2023) Current Grant Activities Timeline Tentative Future Grant Submission Timeline Review and Provide Comments 2026 2027 Final Design Phase -ROW, Utilities, & Final Design (Grant Funded Phase) Upcoming Grants Submission Selected Project (Phase) Funding 2023 2024 2025 2026 Churchill, Meadow, Charleston Project Phase Grants Awarded Selected Project (Phase) Funding 2023 Field Work, Analysis & Draft Report May require amendment/new contract Completed By April 1, 2024 2024 2025 2026 PE & Environmental (Grant Funded Phase) 2027 PE & Environmental (to be completed prior to Final Design Phase) 2023 2024 2025 Conceptual Phase (LPA Selection) Item 1 Attachment A - Grade Separation Project Activities and Timeline        Item 1: Staff Report Pg. 5  Packet Pg. 8 of 105  Rail Committee Staff Report From: Philip Kamhi, Chief Transportation Official Meeting Date: August 23, 2023 TITLE Rail Committee to Review the Preliminary Geotechnical Feasibility Study Memorandum prepared by the Consultant for Grade Separation Projects at Churchill Avenue, Meadow Drive, and Charleston Road EXECUTIVE SUMMARY The City’s engineering consultant (AECOM) has conducted the subsurface exploration and performed data collection from the three sites at Churchill Avenue, Meadow Drive, and Charleston Road crossings in April 2023. The consultant also reviewed available data from nearby projects and data obtained from a limited program of exploration of the sites to assess the soil and groundwater conditions. A Preliminary Geotechnical Feasibility Study Memorandum has since been prepared. Memorandum prepared by the Consultant includes findings to addressing subsurface conditions and the feasibility of alternative construction methods with respect to soil conditions and recommendations for additional studies in future phases. BACKGROUND In 2021 after receiving XCAP recommendations, the City Council selected the preferred alternative and backup alternative for Churchill Avenue and narrowed alternatives in consideration to the three alternatives at Meadow Drive and Charleston Road crossings namely Trench, Hybrid, and Underpass. In addition, the Council directed staff to perform a preliminary geotechnical study to further assist in the review of the alternatives in consideration for the selection of preferred alternative(s). On May 23, 2022, the City Council authorized the amendment with AECOM Consultants that included the scope to perform the preliminary Geotechnical Feasibility Study for review of grade separation alternatives. The City’s Consultant AECOM has conducted the subsurface exploration and performed data collection and sampling from the three sites at Churchill Avenue, Meadow Drive, and Charleston Road crossings in April 2023. The consultant also reviewed data obtained from these Item 2 Item 2 Staff Report        Item 2: Staff Report Pg. 1  Packet Pg. 9 of 105  sites and data available from other nearby projects to assess the soil conditions and ground water levels in the vicinity of each of the three project sites. DISCUSSION The Consultant reviewed regional geology, seismotectonic setting, subsurface conditions, and mapping data available to understand the risk of landslide, flooding, consolidation, and soil corrosivity. In addition, seismic hazards, including the risk of surface fault rupture, strong ground shaking, liquefaction, and lateral spreading were evaluated. Based on the conditions revealed in the geotechnical field explorations completed for this study, as well as those reported for other nearby projects, the soils underlying all three of the proposed grade separation sites consist of relatively strong alluvial fan deposits. The report indicates that except for the moderate liquefaction potential of cohesionless soil interbeds at Meadow Drive and Charleston Road, the main difference among the sites is that groundwater is about 20 feet deeper at Churchill Avenue. Ground Water Conditions: Churchill Avenue Crossing The groundwater level at the Churchill Avenue crossing site is more than 30 feet below the existing ground surface. Unless the grade separation excavation were to extend deeper, the consultant believes temporary dewatering is unlikely to be needed. Therefore, soldier piles and lagging or soil nailing should be feasible for temporary excavation support. Soldier piles and lagging retain the soil using vertical steel piles with horizontal lagging. Typically, H-piles are placed and grouted in holes drilled at regular intervals along the planned excavation perimeter. Lagging consisting of wood or precast concrete panels is inserted behind the front pile flanges as excavation proceeds. The walls can be designed as cantilever walls or receive additional lateral support from external anchors or internal bracing. Soil nailing involves reinforcing in situ soils with grouted, tension-resisting steel elements (nails) to create a gravity retaining wall for temporary or even permanent support. As with soldier pile and lagging walls, the work is done from the top down. Meadow – Charleston Crossings Dewatering will be required during excavation at these crossings due to observed water levels. Groundwater can significantly affect the soil’s stability and it can undermine the effectiveness of soil nailing. Therefore, the consultant believes it would not be a viable option for temporary or permanent excavations support at either of these sites. Item 2 Item 2 Staff Report        Item 2: Staff Report Pg. 2  Packet Pg. 10 of 105  While soldier pile and timber lagging walls have the advantage of being relatively inexpensive and easy to install, they are permeable and would require dewatering to control groundwater. A potential disadvantage of dewatering is that it could cause ground settlement and potentially impact existing railroad facilities, nearby residential dwellings, and underground utilities. Furthermore, large volumes of water would need to be collected and discharged over the course of construction. Pre-treatment of the discharge water also could be required if pollutants are detected. For these reasons, the consultant believes construction methods that cut off groundwater from entering the excavations should be considered. They include cement deep soil mix (DSM), secant pile, and diaphragm (also known as slurry) walls. DSM and secant piles walls are formed by constructing a series of overlapping elements filled either with a soil cement mixture (in the case of DSM) or concrete and incorporating reinforcing steel beams or rebar cages. Diaphragm walls are rigid reinforced concrete walls made up of a series of panels joined together to form a single continuous wall. Clamshell or grab equipment typically is used to excavate soil from the panel areas, using Bentonite or polymer slurry to keep the excavations from caving. After a panel has been excavated and the reinforcement cage inserted, concrete is placed by the tremie method. Because the combined earth and hydrostatic pressure on these walls can be quite high, additional lateral support from external anchors or internal bracing will be needed. If tieback anchors are not permissible, struts (often referred to as cross-lot bracing) could be used. Retaining Walls and Foundation Support: Assuming temporary excavation support using soil nail or soldier pile and lagging walls were to be used at Churchill Avenue, the consultant believes concrete cantilever walls supported on continuous or spread footing foundations would be a feasible option for the anticipated design heights. In the event weak soil deposits are encountered at the foundation level, they would need to be removed or treated (e.g., DSM) to provide the required bearing and sliding resistance. Alternatively, the grade separation walls could be supported on cast-in-drilled-hole (CIDH) piles. CIDH piles also would provide a means of mitigating the risk of post-liquefaction settlement. DSM, secant pile, and diaphragm walls would be better options for the Meadow Avenue and Charleston Road sites, for the reasons discussed above. Plus, all of them can be designed to provide temporary as well as permanent excavation support. Review of Construction Technologies: Box-Jacking Method: Item 2 Item 2 Staff Report        Item 2: Staff Report Pg. 3  Packet Pg. 11 of 105  According to the Consultant, the subsurface conditions underlying the three grade separation sites would likely allow for the feasibility of the open excavation (cut and cover) construction method, including box-jacking. However, it is important to note that a train service outage will be necessary to carry out the 'cut and cover' operations. This would require Caltrain‘s review and approval. In addition, further analysis and review will be needed to assess the structural design of the foundation, potential utility impacts, and relocations, as well as temporary disruptions to local roads. Pipe Canopy and Sequential Excavation Methods: A viable alternative to open excavation is to excavate below the existing tracks, which can be achieved using a Pipe Arch Canopy in combination with the Sequential Excavation Method (SEM). SEM would likely require ground improvement, such as jet grouting to reduce the risk of ground settlement under the tracks. However, it is essential to consider that the design of the project should account for the additional depths that may be necessary to accommodate these construction techniques. These alternatives can be employed while maintaining rail service without the need to construct shoofly tracks. It is important to note that the findings and recommendations presented in the report are based on a feasibility-level subsurface geotechnical study and should be further evaluated and refined during the detailed design phase. Site-specific explorations and assessments are necessary to develop specific recommendations for each grade separation site. This initial geotechnical investigation will assist the City in exploring supplementary design factors and the viability of alternative technologies for assessing various grade separation alternatives as the Rail Committee and the City Council proceed with selecting the preferred alternative at each location. With the completion of the Preliminary Geotechnical investigation, the majority of the work scope that was specified in the Amendment #4 will be fulfilled by AECOM. This included the refinements to underpass alternatives which the Rail Committee assessed at its June 2023 meeting. The peer review of the cost estimate for the trench alternative by the consultant was put on hold as this Caltrain plans to review cost estimates as part of its Service Agreement. FISCAL/RESOURCE IMPACT The Preliminary Geotechnical Feasibility Study task is included in the approved Amendment 4 of the AECOM Contract. Additional geotechnical studies and site studies will be considered during the preliminary and final engineering design phases and will be funded by the approved Capital Improvement Projects. ENVIRONMENTAL REVIEW The recommendation in this report does not constitute a project in accordance with the California Environmental Quality Act and is therefore not subject to environmental review. Item 2 Item 2 Staff Report        Item 2: Staff Report Pg. 4  Packet Pg. 12 of 105  STAKEHOLDER ENGAGEMENT The Rail Committee meetings are open to the public and therefore provide the community with opportunities to provide comments to the rail committee and the City. ATTACHMENTS Attachment A: Preliminary Geotechnical Feasibility Study Memorandum Report #: 2307-1747 Item 2 Item 2 Staff Report        Item 2: Staff Report Pg. 5  Packet Pg. 13 of 105  1 | P a g e Memorandum AECOM 4 N. 2nd Street. Suite 675 San Jose, CA 95113-2254 www.aecom.com 1-408-297-9585 tel 1-408-297-6962 fax Executive Summary In April 2023, AECOM performed a limited geotechnical field exploration program at each of the three proposed railroad grade separation sites: o Churchill Avenue o Meadow Drive o Charleston Road Based on the conditions encountered in the explorations, as well as those reported for other nearby projects, the soils underlying all three of the proposed railroad grade separation sites consist of relatively strong alluvial deposits. Except for the moderate liquefaction potential at Meadow Drive and Charleston Road, the main difference among the sites is that groundwater is about 20 feet deeper at Churchill Avenue. AECOM believes that any open excavation (cut and cover ) construction method, including box- jacking in an open excavation, would be feasible in the subsurface conditions that underlie the three grade separation sites; however, the train service outage required to accomplish cut and cover would require Caltrain approval. As an alternative to open excavation, and to minimize disruption to Caltrain operations, AECOM believes tunneling beneath the existing tracks could be accomplished using a combination of Pipe Canopy and Sequential Excavation Methods (SEM). Additional exploration during final design is recommended, and should consist of sampled boring and cone penetration testing (CPT) explorations at the proposed sites to confirm stratigraphy and conceptually evaluate groundwater cutoff wall requirements. Project Description and Scope of Study The City of Palo Alto (City) is evaluating potential grade separation concepts to eliminate at-grade railroad crossings at the following locations: Churchill Avenue, Meadow Drive, and Charleston Road (Figure 1). A variety of ideas for a citywide solution is under review including a permanent closure of the at-grade rail crossing at Churchill Avenue, partially raising the railroad and partially lowering the roadway (hybrid), viaducts, trenches, and tunnels. To assist in evaluating the feasibility of the various ideas, AECOM has made a preliminary geotechnical study including the following tasks: To Millette Litzinger, PE Associate Vice President - Senior Project Manager Transportation Cc Peter Destefano, PE Deputy Project Manager For Grade Separation Alternatives Churchill Avenue, Meadow Drive, and Charleston Road Palo Alto, California Subject Preliminary Geotechnical Feasibility Study From Paul Boddie, PE, GE Date July 28, 2023 Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 6  Packet Pg. 14 of 105  2 | P a g e Review of the regional geology, seismotectonic setting, and potential geologic and seismic hazards Review of available soil profile and groundwater data from nearby sites Complete a limited geotechnical field exploration program for preliminary site characterization purposes Geotechnical laboratory testing of selected samples recovered from the borings Engineering review of the findings to evaluate the geotechnical feasibility of trenching (overhead), underpass, and - alternatives Preparation of this Technical Memorandum Regional Geology The project area is located about 3¼ miles southwest of San Francisco Bay within the northern portion of Santa Clara Valley, an alluvial basin located between the Santa Cruz Mountains to the southwest and the Diablo Range to the northeast. Santa Clara Valley is located within the central portion of the Coast Ranges geomorphic province of California; northwest-southeast-trending valleys and ridges characterize the region. These topographic features are controlled by folds and faults that resulted from the collision of the Farallon and North American plates and subsequent predominantly strike-slip faulting along the San Andreas fault system between the Pacific and North American plates. Local geologic mapping shows the project area to be underlain by Holocene alluvial fan deposits (Qa.1 & Qa.2) interfacing with intra-fan deposits (Qac) (Dibblee and Minch, 2007). Alluvial fan deposits are described as sand, silt, gravel and clay, with silty, organic, and fossiliferous clay in the intra-fan areas. The nearest bedrock consists of Plio-Pleistocene and Tertiary sedimentary rocks and volcanic basalt mapped at the Stanford University campus about 1½ miles to the southwest of the Churchill Avenue site and about 2½ miles northwest of the E. Meadow Drive and E. Charleston Road sites (Figure 2). Seismotectonic Setting Each of the proposed grade separation sites lies within a region of high seismic activity. In general, earthquakes occur because of movement along active faults. For activity classification, faults are generally grouped into the following categories by the California Division of Mines and Geology (renamed the California Geological Survey, CGS) (Jennings, 1994): Holocene: displacement has occurred within the last 10,000 to 11,000 years. Late Quaternary: displacement has occurred within the last 700,000 years, but evidence of Holocene activity is lacking. Quaternary: evidence of displacement within the last 1.6 million years, but evidence of Holocene activity is lacking. Pre-quaternary: no recognized evidence of displacement in the last 1.6 million years. Generally, faults with Holocene movement are considered to be active while faults with late Quaternary to Quaternary movement are considered to be potentially active . Figure 3 shows active faults within the region relative to the proposed grade separation sites. The closest active faults are the Monte Vista-Shannon, San Andreas, Hayward, and Calaveras. The California Geological Survey (CGS, 2000) has produced maps showing Alquist-Priolo Earthquake Fault Zones along faults with known Holocene activity that pose a potential surface faulting hazard. All of the faults listed above are included as Alquist-Priolo (A-P) zoned faults. The Monte Vista-Shannon fault is located about 4 miles south of the overall project area and the San Andreas fault is located about 5½ miles to the southwest. More distant active faults include the Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 7  Packet Pg. 15 of 105  3 | P a g e Hayward and Calaveras faults located about 13 and 18 miles, respectively, to the northeast. No mapped A- P zoned faults cross the project area. Subsurface Conditions Review of Available Data Available subsurface soil and groundwater data from nearby sites were first reviewed, including information provided by the City for local public and private development projects. Appendix A presents a tabular summary of the data sources, along with information extracted from them and an aerial photo base map showing the approximate site locations in relation to the proposed grade separation sites. Past studies completed by AECOM and our legacy companies also were reviewed. Geotechnical Field Exploration A limited geotechnical field exploration program was then performed; it involved drilling a single boring and advancing a companion seismic cone penetration test (CPT) near each of the three proposed grade separation sites. The approximate locations of the explorations are shown on Figures 4a through 4c. At least one porewater pressure dissipation test was conducted in each CPT to estimate groundwater depth encountered. The explorations initially were advanced to a depth of 5 feet using a hand auger to confirm the absence of underground utilities. Following hand auger clearance, the borings were then advanced with a hollow stem auger (HSA) to a depth of about 15 feet below ground surface (bgs) at Meadow Drive (Boring M-1) and Charleston Road (Boring CH-1) prior to switching to the rotary wash drilling method used to the terminal boring depth of 81½ feet. HSA drilling was used to a depth of 20 feet at Churchill Avenue (Boring C-1) before switching to rotary wash drilling. The logs of borings are presented in Appendix B, along with additional details about the drilling methods. The companion CPT performed at Meadow Drive and Charleston Road each were advanced to depths of 100 feet bgs, whereas the CPT at Churchill Avenue met practical refusal at about 77 feet bgs. Those findings are presented in Appendix C along with the results of the porewater pressure dissipation tests. Laboratory Testing Geotechnical index property tests were performed on both cohesive and cohesionless soil samples recovered from the borings to aid in soil classification and correlation with other engineering parameters. The tests included moisture content, total and dry unit weights, unconfined compressive strength, Plasticity Index (PI), grain size determinations, and corrosion potential, as described in Appendix B. Pocket penetrometer tests also were completed on selected cohesive soil samples in the field and during laboratory sample review to estimate undrained shear strength. The depths at which the tests were made are noted on the logs of borings. The results of PI, grain-size distribution, and corrosion potential tests also are presented graphically in Appendix B. Soil Conditions Churchill Avenue - Boring C-1 encountered approximately 7 feet of hard sandy clay underlain by medium dense sand to a depth of about 15 feet. Hard, grading to stiff, lean clay extended to the terminal depth of 81½ feet, interlayered with medium dense gravelly sand between 38 and 54 feet. The strength and density of these alluvial deposits suggest the compressibility is low. Plasticity Index (PI) testing on a sample of the clay collected from a depth of about 20 feet resulted in a PI of about 15, also suggesting low expansion potential. Companion CPT C-1 revealed generally similar stratigraphy, although the record suggests the presence of sand and silty sand below about 72 feet bgs. Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 8  Packet Pg. 16 of 105  4 | P a g e Meadow Drive - Boring M-1 encountered approximately 25 feet of stiff to very stiff clay with sand underlain by medium dense to dense sand to a depth of about 35 feet, medium stiff to stiff lean clay to 38 feet, and dense sand to 45 feet bgs. Stiff to very stiff lean clay to sandy lean clay extended to the terminal depth of 81½ feet. These alluvial deposits also are considered to have low compressibility and low expansion potential. Companion CPT M-1 revealed generally similar stratigraphy, although the record suggests mostly clay to silty clay, with interbeds of sand between 12 and 15 feet, corresponding to the depth interval where groundwater was first encountered in Boring M-1. Charleston Road - Boring CH-1 encountered approximately 10 feet of very stiff to hard sandy clay underlain by dense silty to gravelly sand to a depth of about 20 feet, medium stiff to stiff sandy lean clay to 24 feet, and medium dense sand and gravel to 43 feet bgs. Very stiff to hard sandy lean clay extended to the terminal depth of 81½ feet. Plasticity Index testing on a sample of the clay collected from a depth of about 20 feet resulted in a PI of about 17. The strength, density, and plasticity characteristic of the soils suggest the compressibility and expansion potential are low. The companion CPT CH-1 revealed generally similar stratigraphy, although the record suggests the presence of sand and silty sand between depths of 58 and 75 feet observed in Boring CH-1. However, Pocket Penetrometer tests on samples recovered from these depth intervals in Boring CH- 1 suggest fine-grained soils. Groundwater Groundwater was encountered at depths of about 12½ and 14 feet bgs in Borings M-1 and CH-1, respectively, before switching to the rotary wash method. These measured groundwater levels are comparable to those recorded in borings drilled at other nearby sites (Appendix A). Porewater pressure dissipation tests performed in CPT C-1 suggest a groundwater depth of about 32 feet near the Churchill Avenue grade separation site. Groundwater was not encountered in companion Boring C-1 before switching to rotary wash. However, explorations made at other nearby sites have encountered groundwater depths in the range of 33 to 36 feet bgs. Potential Geologic Hazards Landslide CGS (2016) mapped the closest earthquake-induced landslide zone about 3 miles to the southwest of the project site. No landslides are mapped on the flat land near or within the proposed grade separation area. Due to the flat lying nature of the area, the site materials are not susceptible to landsliding either seismically induced or otherwise. Flooding As shown in Figure 5, the overall project area is located within the 500-year flood, but outside of the 100-year flood limits. Consolidation Settlement Settlement can occur quickly when soil is loaded by a structure or by the placement of fill on top of it. Time-dependent settlement can also occur gradually when soil porewater pressures, increased by vertical loading, gradually dissipate over time. No new embankment fill is envisioned for the railroad grade separation crossings. Because of the relatively low compressibility of the alluvial soils at all three crossing locations, the risk of potential consolidation settlement due to minor backfill and grading for elevation control and site drainage is expected to be low. However, temporary or permanent dewatering, if needed for construction or maintenance of the grade separations, could induce consolidation settlement and should be evaluated further in the project design. Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 9  Packet Pg. 17 of 105  5 | P a g e Soil Corrosivity Caltrans (2021) considers a site corrosive to foundation elements if the minimum resistivity is less than or equal to 1,100 ohm-cm (as an indicator only), and one or more of the following conditions exist for the representative soil samples taken from the site: Chloride concentration is 500 parts per million (ppm) or greater and/or Sulfate concentration is 1,500 ppm or greater and/or pH is 5.5 or less. Laboratory tests completed on soil samples collected from the three project borings, between depths of about 5 and 22 feet, indicated minimum resistivities exceeding 1,200 ohm-cm, chloride concentrations below 76 ppm, sulfate concentrations below 69 ppm and pH of 7.5 to 8.5. According to the Caltrans guidelines, these samples are non-corrosive to buried steel and concrete. The corrosion test results are included in Appendix B. Preliminary Ground Motions Meadow Drive and Charleston Road are located about 2 miles and 2.3 miles southeast of Churchill Avenue. For the purpose of this feasibility level study, acceleration response spectra using Caltrans ARS Online, v 3.1.0, have been developed separately for Churchill Avenue, with Meadow Drive and Charleston Road considered as one site. Churchill Avenue - The average shear wave velocity in the upper 30 meters, Vs30, is estimated to be about 350 meters/second (m/s) considering data from seismic CPT C-1, standard penetration test driving resistance and undrained shear strength data from Boring C-1. This average Vs30 value corresponds to Site Class D for stiff soil and very dense soil/soft rock sites. The Caltrans ARS Online (Version 3.1.0) tool was used to generate the site characteristics and fault parameters presented below in Table 1a. Table 1a Site Characteristics Parameter Value Site Latitude 37.435599° Site Longitude -122.151562° Site VS30 350 m/s PGA 0.71 g Mean magnitude 7.35 Mean site-source distance 11.9km The ARS Online tool calculates a probabilistic spectrum based on a 5% probability of exceedance in a 50-year hazard level (975-year return period) and for 5% damping. The ARS was adjusted for near fault effects due to the proximity of the site to active faults. The site is not located in a deep sedimentary basin, so a basin amplification factor is not required. Table 1b presents the results. Table 1b Acceleration Response Spectrum Period (s) Design Spectral Acceleration (g) Vs30 = 350 m/s PGA 0.71 0.1 1.25 0.2 1.67 Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 10  Packet Pg. 18 of 105  6 | P a g e Period (s) Design Spectral Acceleration (g) 0.3 1.77 0.5 1.59 0.75 1.36 1 1.2 2 0.61 3 0.4 4 0.3 5 0.23 Meadow Drive/ Charleston Road The shear wave velocity in the upper 30 meters, Vs30, for these two sites ranges between about 305 and about 345 meters/second considering data from seismic CPT M-1 and CPT CH-1, as well as standard penetration test driving resistance and undrained shear strength data from Borings M-1 and CH-1. Results for these sites (combined as one) are presented below in Tables 2a and 2b, assuming an average Vs30 of 325 m/s. Table 2a Site Characteristics Parameter Value Site Latitude 37.416284° Site Longitude -122.120845° Site VS30 325 m/s PGA 0.7 g Mean magnitude 7.28 Mean site-source distance 12.8km Table 2b Acceleration Response Spectrum Period (s) Design Spectral Acceleration (g) Vs30 = 325 m/s PGA 0.7 0.1 1.23 0.2 1.65 0.3 1.77 0.5 1.62 0.75 1.41 1 1.24 2 0.64 3 0.42 4 0.31 5 0.24 Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 11  Packet Pg. 19 of 105  7 | P a g e Potential Seismic Hazards Surface Fault Rupture and Ground Shaking CGS (2006) and MTC/ABAG (2021) do not map any faults crossing the three proposed grade separation sites. The likelihood of surface fault rupture is nil. However, the short distances to nearby active faults including the Monte Vista-Shannon fault and San Andreas fault do create a high risk for ground shaking from fault movement. The intensity of the ground shaking is dependent upon the size of the earthquake, the distance of the epicenter from the site, the direction that the earthquake propagates along the fault, and the site geologic conditions. Liquefaction CGS (2006) mapped both the Meadow Drive and Charleston Road sites as being within a liquefaction hazard zone, whereas Churchill Avenue is mapped outside of this zone. MTC/ABAG (2021) mapped all three of the proposed grade separation sites with a moderate liquefaction hazard (see Figure 5). Since medium dense sand and relatively shallow groundwater underlie the Meadow Avenue and Charleston Road sites, AECOM agrees these two grade separation locations should be considered potentially liquefiable. However, based on the alluvial soil strength and deeper groundwater level of liquefaction potential for the site area is reasonable. Lateral Spreading Lateral spreading occurs when a layer liquefies at depth and causes horizontal movement or displacement of the overburden mass toward a free face such as a stream, canal bank or excavation, or toward an open body of water. Since the potential for liquefaction exists, so does the potential for lateral spreading. Both the potential for earthquake-induced soil liquefaction and lateral spreading should be further evaluated during final design of the proposed grade separations. Tsunami (Figure 6), none of the three proposed grade separation sites is located within the modeled inundation hazard area. Therefore, the potential for tsunami inundation is nil. Preliminary Geotechnical Opinions General Based on the conditions encountered in the explorations completed for this study, as well as those reported for other nearby projects, the soils underlying all three of the proposed grade separation sites consist of relatively strong alluvial fan deposits. Except for the moderate liquefaction potential of cohesionless soil interbeds at Meadow Drive and Charleston Road, the main difference among the sites is that groundwater is deeper at Churchill Avenue. The depth to first groundwater has been measured between 33 and 36 feet below ground surface in borings drilled in the 700 block of Alma Street approximately 2/3-mile to the northwest of Churchill Avenue (see Appendix A). Porewater pressure dissipation tests at the Churchill Avenue site suggest a groundwater depth of about 32 feet. By comparison, groundwater was measured at depths of about 12½ feet at Meadow Drive and 14 feet at Charleston Road. Since the depressed roadway at Churchill Avenue is expected to extend about 20 feet below existing grade at the deepest section, construction likely can be completed in the dry; whereas temporary groundwater control, either by dewatering or groundwater cutoff, will be needed at Meadow Drive and Charleston Road. Measures to permanently control groundwater also will need to be incorporated in the final design, including how to resist buoyant uplift forces on structures extending below the groundwater level. Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 12  Packet Pg. 20 of 105  8 | P a g e Temporary Excavation Support Soldier pile and timber lagging walls have been used for decades throughout the Bay Area to provide temporary support of excavations in a variety of ground conditions. The system retains the soil using vertical steel piles with horizontal lagging. Typically, H-piles are placed and grouted in holes drilled at regular intervals along the planned excavation perimeter. Lagging consisting of wood or precast concrete panels is inserted behind the front pile flanges as excavation proceeds. A major advantage of soldier pile and lagging walls is they are a versatile method that is fast to construct and cheaper when compared to other systems used to support open excavations. However, the system is inherently flexible; therefore, tieback anchors typically are required to limit lateral deformation and associated ground settlement behind the walls. If tieback anchors are not permissible, internal struts (also known as cross-lot bracing) can be used. Soldier pile and lagging walls also are permeable. Therefore, temporary dewatering using wellpoints, deep wells, sumps and pumping would be required if they were to be used at the Meadow Drive and Charleston Road sites where the groundwater level is higher. Additional study would be needed to assess where lowering the groundwater level could induce consolidation settlement, potentially impacting the existing railroad facilities, nearby residential dwellings, and underground utilities. Since temporary dewatering is unlikely to be needed at Churchill Avenue, soil nailing would be another -to consider for that site. The technique uses grouted, tension-resisting steel elements (nails) to reinforce in situ soils and create a gravity retaining wall for temporary excavation or even permanent support. Unfortunately, soil nail walls would be infeasible at the Meadow Drive and Charleston Road sites due to shallow groundwater. AECOM believes cement deep soil mix (DSM) walls with embedded steel beams would be another option to consider for temporary excavation support and to cut off groundwater flow into the required excavations at Meadow Drive and Charleston Road. The DSM method has been used successfully for both temporary and permanent excavations support at other Bay Area sites with similar soil and shallow groundwater conditions. Retaining Walls Types and Foundation Support AECOM expects concrete cantilever walls supported on continuous wall or spread footings should be feasible for the anticipated design heights at all three of the crossing sites. In the event locally weak soils deposits are encountered, they would need to be removed or treated (e.g., DSM) to provide the required bearing and sliding resistance. Another benefit of DSM treatment is the risk of post- liquefaction settlement could be mitigated below retaining walls supported on shallow foundations. Alternatively, the grade separation walls could be supported on cast-in-drilled-hole (CIDH) piles. CIDH piles also would provide a means of mitigating the risk of post-liquefaction settlement. Secant pile and diaphragm (also known as slurry) walls are other wall construction methods that could be considered for both temporary and permanent support. A secant pile wall consists of overlapping (secant) piles used to form permanent structural or cutoff walls to achieve water tightness. The design typically incorporates steel bars or beams for reinforcement within the drilled shafts. A diaphragm wall is a structural concrete wall constructed in a deep trench excavation, using either cast in situ or using precast concrete components. External anchors (e.g., tiebacks) or internal bracing can be used to provide additional lateral support for secant pile, DSM, or diaphragm walls. Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 13  Packet Pg. 21 of 105  9 | P a g e AECOM legacy company URS provided engineering design services as part of the design-build delivery of the 10-mile-long trench segment of the Alameda Corridor freight-rail expressway that connects the ports of Los Angeles and Long Beach in southern California. The photo below is of the Mid-Corridor segment in Compton, California. The mid-corridor trench walls consist of 3-foot diameter cast-in-place reinforced-concrete piles, 4 feet on center, with shotcrete on the inside. They are supported by permanent pre-cast concrete struts at the top and a concrete slab at the bottom of the trench, thereby eliminating the need for temporary ground anchors or tiebacks behind the walls. The following graphic illustrates the construction sequence used. Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 14  Packet Pg. 22 of 105  10 | P a g e The photo below shows the excavation in Stage 2 underway. AECOM believes the strutted secant pile wall construction method also would be feasible in the subsurface conditions that underlie the Meadow Drive and Charleston Road sites along the rail profile where sufficient -vertical clearance could be obtained. The Overhead Contact System (OCS) could be supported from the overhead struts, just as they would from the roof of a tunnel. Grade Separation Structure Construction Options Using Shoo-Flies Regardless of the construction method used (see discussion below), temporary shoo-flies would be required for any alternative that modifies the rail profile (Hybrid, Trench, etc.). The lone exception would be the Viaduct alternative, which allows rail traffic to operate on the existing alignment while a new/offset alignment and structure is under construction. Assuming temporary track realignment (shoo-flies) will be feasible, AECOM believes it would be feasible to support grade separation abutments on large diameter CIDH piles deriving their support capacity through peripheral adhesion between the predominantly clay soils and concrete. Construction by the slurry displacement (wet) method would likely be required for the portion of the shaft extending below groundwater at all three of the sites. Multiple construction stages would be required to complete the abutments, erect the bridge superstructures, install waterproofing and drainage, and relocate the railroad tracks to the finished superstructures. Temporary Rail Service Interruption - AECOM assisted the Santa Clara Valley Transportation Authority (VTA) through 65% design of a pedestrian tunnel at the Santa Clara Caltrain station. Shimmick completed the tunnel construction in 2017. The tunnel is about 80 feet long and runs under three Union Pacific Railroad tracks. The major excavation portion of the project lasted four days, and included stopping rail service on three tracks, cutting about 200 feet of railway, and excavation. The cut-and-cover construction was completed over Thanksgiving weekend in 2016; it utilized precast concrete box units that were set in place to create the floor, walls, and ceiling of the tunnel. A This construction method is feasible; however, b conversations Middle Avenue Pedestrian & Bicycle Undercrossing Project, it would require Caltrain approval due to the risk to the OCS during construction. Temporarily cutting the overhead lines to Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 15  Packet Pg. 23 of 105  11 | P a g e allow for safe cut and cover construction would entail a commuter train service outage, and thus introduce the need for bus bridges for a duration that would also require Caltrain . Italy-based Petrucco Group have developed a similarly innovative box-jacking method that was recently used to replace multiple Long Island Rail Road grade-crossings in New York. The method allowed underpass construction to be completed with only weekend shutdowns; it involves the use of hydraulic jacks and spreaders to move a cast-in-place concrete box carrying the entire underpass and rail bridge into place in an open excavation in a matter of hours, with limited disruption to railway traffic (Photo source: Railway Age, January 5, 2021). AECOM believes the box-jacking construction method would be feasible in the subsurface conditions that underlie the three Palo Alto grade separation sites; however, temporary train service outage would be necessary and it would require Caltrain approval. In addition, other factors would have to be considered if this construction method is pursued further, such as structural design of the foundation, utility impacts/relocations, and temporary disruption to the local roads. Rail Service Maintained - If rail service interruption is unacceptable to Caltrain, AECOM believes tunneling beneath the existing tracks could be accomplished using a trenchless excavation method, such as the Pipe Canopy or the Sequential Excavation Method (SEM). Note that both methods would require lowering of the road and/or ped/bike tunnel 2+ feet more than currently planned (exact depth to be determined depending on the method), which would result in longer pedestrian ramps and more extensive limits to the road profile modification, potentially impacting additional features, such as driveways, utilities, etc. Both methods would involve multiple stages, as described below and illustrated in the cross-sections that follow. Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 16  Packet Pg. 24 of 105  12 | P a g e The following example is an AECOM project that was to include bicycle and pedestrian passages on both sides of the main undercrossing. Stage 1: A series of steel casings that are longitudinally connected to each other would first be installed around the perimeter of the tunnel (under live tracks), then filled with concrete and steel reinforcement, as required. This pipe canopy provides structural support under live tracks to allow for excavation in subsequent stages. Stage 2: The tunnel section would be divided into excavations. In the figure above, three excavations were envisioned. Each of them would be completed in sequence, with steel beams, wire mesh and shotcrete installed as they are advanced in short drives (typically limited to 3 to 5 feet in length), the objective being to minimize potential rail movement and avoid impact to Caltrain operations. Stage 3: After Excavation #1 is finished, cast-in-place concrete tunnel lining would be installed. Stage 4: Excavation #2 would then be completed in the same manner as described above for Excavation #1. Stage 5: Excavation #3 would follow. Stage 6: Temporary columns would then be removed. Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 17  Packet Pg. 25 of 105  13 | P a g e The following photo is an example of a pipe canopy, with low cover conditions, under construction in Toronto, Canada. Recommendations for Additional Studies Additional exploration during final design should consist of sampled boring and CPT explorations spaced at intervals no greater than 300 feet apart along the proposed grade separation alignments to confirm stratigraphy and conceptually evaluate groundwater cutoff wall embedment(s) at Meadow Drive and Charleston Road. Explorations should extend at least 30 feet below the anticipated base of the proposed excavation at any given location. At least four observation wells should be constructed with two of them screened in the upper sand layer and two screened in the lower sand/gravel layer to allow for slug or pump testing to estimate hydraulic conductivities for use in seepage analyses. Field and laboratory testing to evaluate permeability of water bearing granular deposits also should be Deep borings should be advanced at railroad grade separation abutments to characterize the subsurface soils for deeps foundation design; the borings should be at least 100 feet. Explorations should extend at least 20 feet below the anticipated bottoms of CIDH foundations. Relatively undisturbed samples of cohesive soil should be collected for triaxial and consolidation testing. Pressuremeter testing could be used to potentially justify higher soil strengths to allow for a reduction in foundation embedment depths. Additional sampled boring and CPT explorations should be performed to achieve an exploration interval spacing no greater than 200 feet where new concrete cantilever retaining walls are proposed; these explorations should extend to depths equal to twice the wall height taken from bottom of footing elevation or a minimum of 20 feet, whichever is greater. One or more explorations would also be necessary for design of pump station foundations, depending on the proximity to explorations for other project features. Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 18  Packet Pg. 26 of 105  14 | P a g e Samples should be collected from all borings at intervals no greater than 5 feet or at changes in stratigraphy, whichever is more frequent. Selected soil samples from the borings should be tested to evaluate moisture content, total and dry unit weights, gradation, Plasticity Index, unconfined compressive strength, and to confirm the corrosion characteristics are consistent with the results obtained as part of this feasibility level study. Limitations The geotechnical considerations and opinions discussed in this technical memorandum are of a general nature and are intended to be used only for feasibility level planning purposes. They are based a limited subsurface exploration program, review of nearby historic soil and groundwater information, engineering should be developed for the sites. This will require explorations to supplement the available information and further refine our knowledge and understanding of the site-specific subsurface conditions. Our preliminary opinions and conclusions have been developed with the standard of care commonly used in this profession. No other warranties are included, either express or implied, as to the professional advice presented in this report Attachments: Figure 1 Vicinity Map Figure 2 Geologic Map Figure 3 Active Faults in Project Region Figures 4a through4c Site and Exploration Plans Figure 5 Liquefaction Susceptibility Figure 6 Flood Hazard Map Appendix A Summary of Available Subsurface Data - City of Palo Alto Archives Appendix B Field Exploration and Laboratory Testing Appendix C Cone Penetration Testing Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 19  Packet Pg. 27 of 105  15 | P a g e REFERENCES California Geological Survey [Tianqing Cao and others], 2003, The revised 2002 California probabilistic seismic hazard maps, June 2003: CGS online publication at www.consrv.ca.gov/cgs/rghm/psha/fault_parameters/pdf/2002_CA_Hazard_Maps.pdf California Geological Survey, 2006, Earthquake Fault Zones and Seismic Hazards, Palo Alto and Mountain View Quadrangles, scale 1:24,000. https://maps.conservation.ca.gov/cgs/EQZApp/ California Geological Survey, 2016, California Landslide Inventory. https://maps.conservation.ca.gov/cgs/lsi/ California Department of Transportation: Caltrans ARS Online, 2019: Web-based tool calculates both deterministic and probabilistic acceleration response spectra. California Department of Transportation, 2021, Corrosion Guidelines. Campbell-Bozorgnia (2008) and Chiou-Youngs (2008) ground motion prediction equations: -Lifelines program: http://peer.berkeley.edu/products/nga_project.html Dibblee, T.W. and Minch, J.A., 2007, Geologic map of the Palo Alto and Mountain View quadrangles, Alameda, San Mateo, and Santa Clara Counties, California: Dibblee Foundation Map DF-350, scale 1:24,000. https://ngmdb.usgs.gov/Prodesc/proddesc_83441.htm Heeley, E.J., R.W. Graymer, G.A. Phelps, P.K. Showalter and C.M. Wentworth, 1994, Quaternary Geology of Santa Clara Valley, Santa Clara, Alameda and San Mateo Counties, California: USGS Open-File report 94-231. Jennings, C.W. and Bryant, W.A., 2010, Fault activity map of California: California Geological Survey Geologic Data Map No. 6, scale 1: 750,000. Metropolitan Transportation Commission (MTC)/ABAG Hazard Viewer Map, 2021. https://mtc.maps.arcgis.com/apps/webappviewer/index.html?id=4a6f3f1259df42eab2 9b35dfcd086fc8 Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 20  Packet Pg. 28 of 105  Alm a S t Alm a S t Mi d d l e f i e l d R d Wa v e r l y S t Alm a S t Mi d d l e f i e l d R d Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 21  Packet Pg. 29 of 105  Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 22  Packet Pg. 30 of 105  East Valley Trust Faults Stanford fault Northern Midland Zone Thorton Arch Zone Montezuma Hils ZoneBriones Source Zone Mt. Diablo - South Mt. Diablo - North Galt Lodi Tracy Dixon Dublin Oakland Antioch Isleton Manteca Stockton Livermore Brentwood Rio Vista Hayward Concord Lathrop Pittsburg Vacaville Fairfield Pleasanton Walnut Creek 121°40'0"W 121°40'0"W 122°50'0"W 122°50'0"W 38°20'0"N 38°20'0"N 37°10'0"N 37°10'0"N Figure 3ACTIVE FAULTS IN THE SITE REGION 0 10 20 30 405 Kilometers 10 0 105 Miles Fault Source: AECOM Seismic Source Model LEGEND SAF - San Andreas Fault Faults with surface rupture Blind faults and zones Project No. 60577356 Alma Street Grade Separation, Palo Alto, CA Segment Boundaries Alma Street Grade Separation ACTIVE FAULTS IN THE PROJECT REGION Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 23  Packet Pg. 31 of 105  Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 24  Packet Pg. 32 of 105  Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 25  Packet Pg. 33 of 105  Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 26  Packet Pg. 34 of 105  Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 27  Packet Pg. 35 of 105  Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 28  Packet Pg. 36 of 105  Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 29  Packet Pg. 37 of 105  Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 30  Packet Pg. 38 of 105  Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 31  Packet Pg. 39 of 105  Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 32  Packet Pg. 40 of 105  Set casing to 13½ feet Switched to rotary wash at 15 feet Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 33  Packet Pg. 41 of 105  Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 34  Packet Pg. 42 of 105  Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 35  Packet Pg. 43 of 105  Switched to rotary wash at 15 feet Set casing to 13½ feet Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 36  Packet Pg. 44 of 105  Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 37  Packet Pg. 45 of 105  Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 38  Packet Pg. 46 of 105  Set casing to 13½ feet Switched to rotary wash at 20 feet Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 39  Packet Pg. 47 of 105  Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 40  Packet Pg. 48 of 105  Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 41  Packet Pg. 49 of 105  Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 42  Packet Pg. 50 of 105  DESCRIPTION / CLASSIFICATION Project Name: PLASTICITY CHART Project Number: Figure B-6 Boring Number Caltrain GSP Palo Alto 60577356 Water Content (%) Sample Number Depth (ft)LL PI CH-1 4 Light olive brown Lean CLAY (CL)20.0-21.5 21.0 39 22 CL-ML 4 7 CL or OL CH or OH ML or OL MH or OH 0 10 20 30 40 50 60 70 80 0 10 20 30 40 50 60 70 80 90 100 110 PL A S T I C I T Y I N D E X ( % ) LIQUID LIMIT (%) Figure B-6_Atterberg Limits Caltrain GSP Palo Alto CH-1, sample 4 20.0-21.5 ft.xlsx AECOM Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 43  Packet Pg. 51 of 105  Item 2 Attachment A - Preliminary Geotechnical Feasibility Study Memo        Item 2: Staff Report Pg. 44  Packet Pg. 52 of 105  Item 2 Attachment A - 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