HomeMy WebLinkAbout2020-04-17; Yarrow Drive Sinkhole and Emergency Sewer Main Break on April 12, 2020; Gomez, PazTo the members of the:
CllY COUNCIL
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April 17, 2020
Council Memorandum
To: Honorable Mayor Hall and Members of the City Council
From: Paz Gomez, Deputy City Manager, Public Works
Via: Geoff Patnoe, Assistant City Manager
Re: Yarrow Drive Sinkhole and Emergency ewer Main Break on April 12, 2020
This memorandum provides information on the Yarrow Drive sinkhole and emergency sewer
main break that occurred on Sunday, April 12, 2020.
Background
Shortly after 12:00 pm on April 12, 2020, city staff from Police, Fire and Public Works
Utilities Departments responded to a report of a sinkhole in a private property parking lot at
6300 Yarrow Drive. A van, either on or near the manhole, had fallen into a sinkhole which
resulted in a palm tree falling on top of the van. It was determined that the cause may have
been a collapsed sewer manhole along the Buena Outfall pipeline. This pipeline is owned by
the Buena Sanitation District (Buena), located within its easement and shared with the City
of Carlsbad for use through an agreement. Buena and City of Vista Public Works Department
staff also subsequently responded.
The sewage continued to flow through the hole and into the Buena Outfall pipeline. This
pipeline conveys wastewater flow from Buena and the City of Carlsbad to the Encina Water
Pollution Control Facility for treatment and disposal. Shortly before this occurrence, the
McCl�llan-Palomar Airport weather station reported approximately 6.2 inches of rain over a
6-day period the week of April 6, 2020, including 2.88 inches received within a 24-hour
period from midnight on April 9, 2020 to midnight on April 10, 2020.
Discussion
Sewage flow continued down the pipeline and there was no sanitary sewer overflow (SSO)
observed. Before the San Diego County Public Health Order to shelter in place related to the
COVID-19 public health emergency, the flow in the pipeline averaged 1.8 million gallons per
day of sewage. Due to the rain events and the County Public Health Order to shelter in
place, the flow increased to an average of approximately 3 million gallons per day of
sewage.
The pipeline is approximately 30 feet deep at this location, and pumping was beyond the
capability of both agencies' equipment. Outside services were immediately required to
minimize the possibility of an SSO. An SSO would discharge untreated sewage into
Encinas Creek which outlets to the Pacific Ocean.
Public Works
Utilities Department
5950 El Camino Real I Carlsbad, CA 92008 I 760-438-2722 t
Memo ID# 2020068