Alternative Title

Paper No. 6.10

Location

St. Louis, Missouri

Date

11 Mar 1998, 4:30 pm - 6:30 pm

Abstract

On December 11, 1995, a 100-year old brick sewer ruptured in the exclusive Sea Cliff area of San Francisco, during and intense, but not extraordinary rain storm. Storm flow had been constricted by an Overflow Structure 1400 feet downstream of the failure, causing pressurization of the sewer. At the site of the initial failure water was forced through cracks in the sewer wall. Earlier construction of an adit below the brick sewer and the subsequent development of an adjacent sinkhole relaxed the soil confinement, allowing cracks to widen and water to escape. Ultimately, the sewer completely ruptured. Discharge from the sewer eroded a pit over 250 feet wide and 40 feet deep that caused the nationally-televised destruction of a multi-story residence, as well as severe damage to adjacent public and private property. This paper is a summary of the public report of the forensic investigation.

Department(s)

Civil, Architectural and Environmental Engineering

Meeting Name

4th Conference of the International Conference on Case Histories in Geotechnical Engineering

Publisher

University of Missouri--Rolla

Document Version

Final Version

Rights

© 1998 University of Missouri--Rolla, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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Of Sewers, Sinkholes, and Safes: The Investigation of the Sea Cliff Incident, December 11, 1995, San Francisco, California

St. Louis, Missouri

On December 11, 1995, a 100-year old brick sewer ruptured in the exclusive Sea Cliff area of San Francisco, during and intense, but not extraordinary rain storm. Storm flow had been constricted by an Overflow Structure 1400 feet downstream of the failure, causing pressurization of the sewer. At the site of the initial failure water was forced through cracks in the sewer wall. Earlier construction of an adit below the brick sewer and the subsequent development of an adjacent sinkhole relaxed the soil confinement, allowing cracks to widen and water to escape. Ultimately, the sewer completely ruptured. Discharge from the sewer eroded a pit over 250 feet wide and 40 feet deep that caused the nationally-televised destruction of a multi-story residence, as well as severe damage to adjacent public and private property. This paper is a summary of the public report of the forensic investigation.