Vibrating Wire Piezometer Installation and Geotechnical Boring for the Palo Alto Flood Basin Tide Gate Structure Phase 1 Project
Summary
SCH Number
2024020725
Public Agency
Santa Clara Valley Water District
Document Title
Vibrating Wire Piezometer Installation and Geotechnical Boring for the Palo Alto Flood Basin Tide Gate Structure Phase 1 Project
Document Type
NOE - Notice of Exemption
Received
Posted
2/20/2024
Document Description
Valley Water is designing the Palo Alto Flood Basin Tide Gate Structure Phase 1 Project which aims to reduce seismic vulnerabilities and extend the existing tide gate structure’s service life by retrofit and rehabilitation. The said project is anticipated for construction in Fall 2025. To support the design and construction phases of the tide gate structure project, two data collection activities are necessary. These include the installation of a vibrating wire piezometer to collect groundwater level information, and a geotechnical investigation to evaluate soil conditions within the proximity of pile location to be constructed in 2025. Only one boring hole up to 70 feet deep below the levee crest is required to satisfy both data collection needs. A truck-mounted drill rig with a 5-inch auger would be utilized to create the said hole. A practical boring location would be selected on the levee area within 60 feet of the west end of the existing structure. While the 70-foot depth would be utilized for the geotechnical investigation purpose, the proposed piezometer depth is only up to 30 feet below the levee crest. Therefore, the bottom 40 feet of the hole would be backfilled in accordance with Valley Water Well Standards once the geotechnical data collection is complete and the top 30 feet of the hole would be utilized to house the piezometer assembly.
Once the bottom 40 feet of the hole has been backfilled properly, the vibrating wire piezometer attached to a small PVC pipe not exceeding 1 inch diameter would be inserted into the hole. Grout would fill the excess space inside the hole. The top end of the piezometer will be connected to a terminal box placed inside a Christy box. Excess soil and drilling materials would be temporarily stored in a steel drum before being transported off-site for proper disposal, and the surrounding area would be restored to pre-disturbance conditions. No vegetation removal would occur because of the work implementation.
Access for the work activities would be from the existing levee trail accessed from Byxbee Park in Palo Alto. The piezometer installation and geotechnical investigation activities are expected to take no longer than 2 days to complete. Work would occur between Monday and Friday between 8 am and 6 pm in accordance with the allowed construction hours set by the City of Palo Alto Noise Ordinance.
Contact Information
Name
Christopher Hall
Agency Name
Santa Clara Valley Water District
Job Title
Assistant Environmental Planner
Contact Types
Lead/Public Agency
Phone
Location
Coordinates
Cities
Palo Alto
Counties
Santa Clara
Regions
San Francisco Bay Area
Zip
94303
Notice of Exemption
Exempt Status
Categorical Exemption
Type, Section or Code
Class 6
Reasons for Exemption
The project qualifies for a Categorical Exemption under California Environmental Quality Act (CEQA) Guidelines §15306: “Class 6 consists of basic data collection, research, experimental management, and resource evaluation activities which do not result in a serious or major disturbance to an environmental resource. These may be strictly for information gathering purposes, or as part of a study leading to an action which a public agency has not yet approved, adopted, or funded.”
The project would consist of geotechnical investigation on an existing developed parcel within Valley Water easement. No vegetation removal or tree trimming would be required. These activities are for data collection and resource evaluation, and they would not result in serious or major disturbances to an environmental resource. Furthermore, none of the exceptions to the use of a Categorical Exemption noted under the CEQA Guidelines §15300.2 would apply.
County Clerk
Santa Clara
Attachments
Notice of Exemption
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