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San Francisco

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Sunnydale Auxiliary Sewer Tunnel


SFPUC completed the construction of approximate 6,400 feet of auxiliary sewer line along Sunnydale Avenue, San Francisco, California in 2012.  A portion of the alignment was located within volatile organic compounds (VOCs) soil and groundwater contamination areas.  The VOCs contamination is currently being addressed and remediated by a third party (the Site Owner) with oversight by DTSC.

AEW was retained by SFPUC to provide consulting and planning services to address environmental issues from conceptual to detailed design phases of the project.  Primary objectives of our environmental services included (1) a comprehensive understanding of chemical conditions in subsurface media along the proposed alignments; (2) evaluation of potential soil classifications for excess soil requiring off-site disposal; (3) evaluation of groundwater quality for potential wastewater discharge, (4) baseline air quality monitoring for developing project-specific air quality action and stop work levels for the construction, (5) identification of environmental mitigation requirements and development of the corresponding mitigation measures, (6) environmental sections of the construction bids and specifications development, (7) environmental coordination with DTSC and the Site Owner for the construction and operation of the sewer line within the VOCs contamination area, and (8) support to the SFPUC's team to resolve unexpected environmental conditions encountered during construction.

Project Challenges

A portion of the planned alignment passed through an existing VOCs plume that is undergoing remediation with oversight by DTSC.  It is crucial for SFPUC and its design team to identify impact and concerns by DTSC and the Site Owner on the design and construction of the alignment sections within the VOCs contamination area in relationship to the on-going investigation and the planned VOCs remediation.  In addition, the planned construction schedule of the sewer line is anticipated to be coincided with the planned schedule for the VOCs remediation.  It is critical to establish a strong coordination and relationship between SFPUC, DTSC, and the Site Owner in order to maintain a clear understanding of the requirements between both projects with the goal to minimize technical and schedule impacts for both projects.  To address this challenge, since the early stage of the sewer line design, AEW conducted stakeholder meetings and assisted SFPUC to maintain strong coordination, and periodic updates to DTSC, the Site Owner, and its consultant to relate the information on the design, construction methods, planned environmental mitigation measures, and construction schedule.  The stakeholder meetings and communications successfully allowed SFPUC to address all DTSC and Site Owner concerns, and to facilitate the DTSC approval of the environmental documents related to the sewer line construction within the VOCs contamination area.  As a result, no redesign of the tunnel was required to address DTSC and Site Owner’s concerns on the design, and the construction schedule.


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