HomeMy WebLinkAbout2024-02-13 Wastewater spill Rock Creek Lift Station 5day report 5-Day Letter Jacobs
Date: February 19,2024 IPDES Program Manager
IDEA Twin Falls Office
650 Addison Ave W
Twin Falls Idaho 83301
RE:Twin Falls SSO,Permit#ID-002127-0
On Tuesday,February 13th, 2024,a Twin Falls Wastewater Collection employee observed an active Sanitary
Sewer Overflow(550)at the Rock Creek Lift Station.The Jacobs maintenance team was promptly notified at
10:00 am,and they responded swiftly to the site.Equipment was reset,and the 550 ceased by approximately
10:15 am.A sample was collected and processed for pH,temperature,and E.coli analysis.
Our investigation indicated the following:
1 Previous Rounds:On Wednesday, February 7th, rounds were conducted at the Lift Station,during
which no issues were identified.The station appeared to be functioning correctly.
2. Alarm Light Discovery.Subsequently,we learned that a neighbor had noticed the alarm light
activated since Friday, February 9th.Based on this information,we assume that the SSO persisted
from Friday, February 9th,through Tuesday,February 13th.
3. Estimated Volume:The total volume of the SSO is estimated to be approximately 12,000 gallons.
Most of this flow likely entered Rock Creek.
4, Response Actions:On Wednesday the 14th,City crews applied a disinfectant to the affected field
areas.Additionally,grab samples were taken both upstream and downstream from the point of entry
into Rock Creek.The E.coli results were as follows:
Sample from Active Spill(2/13/2024):>2419.6 MPN/100 ml
Upstream(2/14/2024):21.8 MPN/100 ml
Downstream(2/14/2024): 143.9 MPN/100 ml
S. Equipment Failure:The lift station experienced a failure of the in-line comminutor.Simultaneously,
the call-out alarm system failed to activate.This malfunction resulted in flow backing up into the
collection lines and discharging into a horse pasture adjacent to the lift station.Upon inspection,it
was determined that the comminutor requires replacement Our technician investigated the alarm
system failure but found no specific reason.After rebooting the dialer system,alarms resumed
functioning.The Rock Street Lift Station PLC will be connected to the wastewater plant SCADA to
provide a backup ability for a dialer system.A high-level float will be installed on the inlet side of the
comminutor to allow for alarms.Damaged piping feeding the Lift Station will be repaired.The
comminutor is currently bypassed and all flow is running through a manually cleaned bar screen.This
bar screen will be inspected and cleaned 5 times a week until the new comminutor and upgrades are
completed.
Dan Black,Project Manager
Twin Falls WWTP
Dan.blackoiacobs.com
208-734-9933
!Ghent name)