TO: Andrew P. Powers, City Manager
FROM: Clifford G. Finley, Public Works Director
DATE: February 14, 2024
SUBJECT: Emergency Wastewater Filtrate Line Repair – Hill Canyon Treatment Plant Public Emergency Declaration
Pursuant to Thousand Oaks Municipal Code (TOMC) 3-10.308, please acknowledge below and make a public emergency declaration for the repair of a wastewater filtrate pipeline located at the Hill Canyon Treatment Plant (HCTP). Ratification of this Public Emergency Declaration will be requested at the February 27, 2024, City Council meeting.
On Sunday, February 11, 2024, at approximately 12:30 a.m., when leaving the plant at the end of their shift, staff found untreated wastewater leaking from a failed Gravity Belt Thickener filtrate line located at the bridge near the main entrance inside the plant. Staff was able to determine the source, stop, and isolate the leak within 15 minutes and reported the incident to the Superintendent and Laboratory Supervisor who provided immediate response and began their investigation. It was determined that the leak started at approximately 11:40 p.m., Saturday evening, resulting in an estimated 15,000 gallons of untreated wastewater entering the North Fork of the Arroyo Conejo Creek. Regulatory agencies were notified as required by HCTP’sNational Pollutant Discharge Elimination System (NPDES) permit and according to the HCTP Emergency Response Plan for Wastewater Related Spills and/or Permit Exceedance. Additionally, Camrosa Water District was also notified because their creek diversion structure for non-potable re-use is downstream of the plant, as well as Conejo Re creation and Park District staff. The following morning, staff posted signage along the creek to alert hikers of the hazard.
Samples from the creek were collected for te sting and analysis. In coordination with the Ventura County Environmental Health Division, signage was authorized for removal after three consecutive days of sampling indicating the spill is not impacting the creek.
The failed pipe is near the center of the roadway just inside the main gate of the treatment plant and directly adjacent to the main bridge. This roadway serves as the only vehicular access to the plant, including trucking and deliveries necessary for plant operations. At the same location of the failed filtrate line are a large number of other utilities and additional process lines. Due to the location of the failed line, there is potential that the roadway is undermined or could lead to the development of a sinkhole, potentially compromising safe access to the facility or impairing other infra structure necessary for continued treatment operations. A significant r ain event is in the near forecast adding to the urgency for repair.
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?HY?&RXQFLO???3XEOLF(PHUJHQF\'HFODUDWLRQ::/LQH5HSDLUDW+&73$WWSGI Emergency Wastewater Filtrate Line Repair
Public Emergency Declaration
February 14, 2024
The staff has installed a temporary bypass to send the filtrate flow to another part of the plant while the line is out of service. However, this temporary bypass may be impacted by the upcoming predicted rains and could lead to the interruption of the Gravity Belt Thickeners which operate for approximately 18 hours per day.
After an initial investigation of the issue, it was determined the repair is anticipated to have three phases: temporary shoring of the roadway to ensure safe vehicular access and minimize the potential for further damage, repair of the failed line, and cleaning of the entire line from the Gravity Belt Thickeners to the South Plant Primary Clarifiers to restore proper flow and pressure within the line and minimize the potential for future spills.
Under the emergency provisions of our purchasing guidelines, staff contacted multiple contractors to assess availability for repairs. Discussions revealed that distinct phases of the repair might need different contractors. Staff has authorized Blois Construction (Oxnard, CA) and GSE Construction (Livermore, CA) to begin work to repair the line. Blois Construction and GSE Construction are experienced in this type of work and are available to immediately mobilize.
The total cost for this repair is currently estimated at $75,000. Ratification of this Public Emergency Declaration and authorization of City Manager approval of two separate General Services Agreements with Blois Construction and GSE Construction will be requested at the February 27, 2024, City Council meeting.
PUBLIC EMERGENCY
DECLARATION APPROVED
Clifford G. Finley Andrew P. Powers
Public Works Director City Manager
DPW:290-10\ks\H:\COMMON\Purchasing\Contracts\Emergency GBT Filtrate Line\GBT Filtrate Emergency Repair Memo.docx