responding to and planning for lift station failures

Responding to and Planning for Lift Station FailuresFEBRUARY 18, 2020

2020 WEAT SEMINAR 1

Denton Wastewater Utility Background

• 100+ square mile service area

• 540+ miles of collection and force mains

• 2 WWTPs

• 31+ lift stations (and more on the way)

• 2 full time 6-man construction crews

2020 WEAT SEMINAR 2

2020 WEAT SEMINAR 3

Hickory Creek Lift Station

• 40 Square mile basin

• Constructed in 1984

• Wet well – Dry pit construction

• Firm Capacity = 3,500 gpm (5 MGD)

• 3 pumps (2 functional)

• 12,200 LF 24-inch Forcemain

• Average Daily Flow 3 MGD

2020 WEAT SEMINAR 4

Hickory Creek System Failures

A pump casing failed after ingesting concrete. Pump replaced. Pump 3 valves damaged and not repaired for cost savings. SSO – 720,750 gallons

Feb. 2018

Electrical anomaly believed to have caused transient surge. SSO – 300,000 gallons

Dec. 2018

Electrical anomaly believed to have caused transient surge. SSO – 490,000 gallons

Nov. 2019

2020 WEAT SEMINAR 5

December 2018 Event

• 1:56 PM – Plant receives VFD Failure Alarm on Pump 1

• 2:20 PM – Staff determines VFD 1 fuses have blown

• 2:30 PM – Staff start Pump 2

• 2:43 PM – Dispatch receives call of sewer coming out of the ground

• 3:00 PM – Staff identify forcemain leak

• 4:28 PM – Lift station is shut down

• 11:00PM the following day – FM Repairs completed

2020 WEAT SEMINAR 6

Constrained Site

2020 WEAT SEMINAR 7

Fun Photos

2020 WEAT SEMINAR 8

Fun Photos

2020 WEAT SEMINAR 9

Important Considerations

2020 WEAT SEMINAR 10

Thanksgiving 2019 Event

• Sunday, November 24th

• Received a call of an issue at the HCLS

• 10:00 am City staff rapidly mobilized to the site

• Immediate notification was sent to UTRWD, TCEQ and CMO/PA

• Contacted Sunbelt to provide bypass equipment

• Staff set up pumps and piping we had on hand to begin bypass

• 3:59 pm begin bypass to UTRWD with small pipe and pumps COD had

• 10:30 pm Sunbelt piping, drive over, and pumps set up and sent flow to UTRWD



• Monday, November 25th and Tuesday, November 26th

• Contractor onsite to deploy sand bag and plug piping

• Declaration of Emergency issued

• Press Releases sent

• Pumping continued to evaluate the situation

• Water Quality Sampling began

• Walked project with TCEQ

• Damage discovered

• Sand plug failed



• Wednesday, November 27th and Thursday, November 28th

• Pumping and Water Quality Sampling continued• Pump 2 part received from Chicago • Pump 2 repairs were made and regular lift station operation restored• Bypass pumping to UTRWD still deployed• Overflow stopped

• Tuesday, December 3rd – Monday, December 9th

• Press release sent• Rangeline installed stopple on force main• Boil water notice lifted for citizens with water well within one half-mile of lift station• Pump 1 repairs were made using parts from Pump 3 • Pump 1 was operational and redundancy was restored


172020 WEAT SEMINAR

Total Spend on Two Events

December 2018 Event – $115,500 + Equipment time

Bypass Pumping Equipment – $205,000 to date (not all costs accounted for)

November 2019 Event – $165,000 + Equipment time to date (not all costs accounted for)


Recurring Questions

• What did we do last time?

• Why reinvent the response?

• Why not own everything we need?

• What do we need to purchase?

• Why can’t we use what we purchased?

• Where is that old public notice document?

• Who do we call at TCEQ?

• Leadership Transitions led to knowledge loss.


Lift Station Emergency Response Plan

• What does it need to say?

• What data is necessary?

• Maps

• System curves

• Pump curves

• Equipment lists

• Bypass capability

• Site photos

• Incident Commander


Lessons Learned

Establish an ERP

Establish a Scribe and central POC

Public Notices and Press Releases

Departmental Coordination

Establish working parameters

Establish Documentation process

Bypass equipment and materials need to be ready


Materials List for Emergency Response•10” Lay-Flat Hose

•10”, 8”, 6” and 4” Centrifugal Pumps

•Trailer(s)

•Road Ramp

•Road Ramp Adapters

•10” Adapters

•10” O-Ring

•2” Air Vent

•10” Check Valve

•10” 45 degree and 90 degree Bends


Special Thanks


Questions / Comments

Denton Water and Wastewater Utilities


responding to and planning for lift station failures

Documents