When and how to look at recessed pump stations as an alternative to submersible designs. Issues of safety, maintenance, and workforce capacity all apply.

1. When is it Time for Recess?
Brian Gongol
DJ Gongol & Associates, Inc.
June 9, 2022
Iowa Water Environment Association Annual Conference
Davenport, Iowa

2. Scenario 1:

Raw lift

Aging vertical
lineshaft pumps

Cramped wetwell

Backup power
needed

Water level 26'
below grade

3. Problems like this sound vicious, but they can be solved

4. First, let's review a few numbers

5. OSHA's top ten citations in FY2020
#10: Machinery and machine guarding
#9: Eye and face protection
#8: Fall protection training requirements
#7: Powered industrial trucks
#6: Control of hazardous energy (lockout/tagout)
#5: Ladders
#4: Scaffolding
#3: Respiratory protection
#2: Hazard communication
#1: Fall protection

6. Spot the hazards in these ordinary pump stations
#10: Machinery and
machine guarding
#9: Eye and face
protection
#8: Fall protection
training requirements
#7: Powered
industrial trucks
#6: Control of
hazardous energy
(lockout/tagout)
#5: Ladders
#4: Scaffolding
#3: Respiratory
protection
#2: Hazard
communication
#1: Fall protection

7. Being underground makes the hazards worse

8. Getting closer to the surface is intrinsically safer
Only submarines are safer when they go deeper

9. Wastewater is littered with confined spaces

10. Confined spaces
"Confined space" means a space that:

(1) Is large enough and so configured that an employee
can bodily enter and perform assigned work; and

(2) Has limited or restricted means for entry or exit (for
example, tanks, vessels, silos, storage bins, hoppers,
vaults, and pits are spaces that may have limited means
of entry); and

(3) Is not designed for continuous employee occupancy.

11. OSHA confined-space flow chart

"Can the hazards be
eliminated?"

"Can the space be
maintained in a condition
safe to enter by
continuous forced air
ventilation only?"

12. Getting above ground "eliminates hazards"
(Full stop.)

13. Oh, and one more thing
BABA is here

14. Great news!
Physics will spot us about
25' of elevation!
32.8' of atmospheric pressure
(at 1000' elevation)
- 1' of vapor pressure
- 2' of safety factor
...leaving 29.8' for TDSL
and pump NPSHr

15. Recess is good for bridging marginal cases

Just because it's a suction-lift pump doesn't mean it has
to lift all the way to the surface

Close counts in more than
horseshoes & hand grenades!

16. Back to Scenario 1

26' of lift to the
surface doesn't have
to be a deal-breaker

We can recover a
couple of feet by
recessing the station
without burying it

17. Results:

New pumps installed with old pumps still in service

Recovered all wetwell volume except for the thickness
of the suction pipes

Integrated engine-driven backup installed with the
station package

Pumps handle 25' of the lift, excavation handles the rest

Unrestricted entry via a door and a couple of stairs

18. Suction-lift pumps have two natural limits

Limit #1: Net NPSHa
(atmospheric pressure minus
vapor pressure, safety factor, and
TDSL)

Limit #2: Reprime lift

Recessed stations help overcome
both limits while capturing safety
and operational advantages

19. Discharge heads used to be a practical limit
But no longer:
Can now exceed
300' of TDH with
multistage
suction-lift pumps

20. Scenario 2:
Dry pit/wet pit
configuration
30' to grade level
Chronic I&I issues
Need to increase
storage capacity

21. Scenario 2:
Dry pit becomes
auxiliary wetwell
Capacity expands
Recession moves
effective "grade"
elevation closer
Pump moves to a
safer location

22. Increasing hassles with clogs

23. No end in sight to the problem

24. More solids, less water
High-efficiency
washers
Energy Star
dishwashers
Low-flow
showerheads

25. Scenario 3:
Wet-pit submersibles
Lone operator
Community won't stop
flushing wipes
Flows decreasing, clogs
increasing

26. Scenario 3:
Pump can be unclogged
without any wetwell
exposure
Lone operator can
perform required work
without confined-space
entry

27. Raising the pumps delivers safer work routines

28. Lifting parts, not whole pumps

29. No wetwell exposure to deal with pumps
It's just pipes

30. Separation of motors from pumps

31. Can drain a pump before opening

32. Can see hazards inside the pump

33. Scenario 4:

New-build

Residential area

Flat topography

Near river

Need deep wetwell for gravity feed

Bonus: Can be protected from flooding

34. Climate change may cause more floods
Valve vaults flood
Exposed control panels wash out
Walls can provide
intrinsic flood protection

35. Separation from hazards is still valuable

36. Have to be comfortable with harm reduction
"[T]he choice must always be made,
if not of the lesser evil,
at least of the greater,
not the perfect, good"
- Federalist Paper 41

37. A flooded valve vault doesn't do you any good

38. That's not a submersible control panel

39. Scenario 5:
Existing "canned" lift
station
Main lift station before
WWTP
More capacity needed
Limited space available
Can't afford any
downtime
Need to hot-swap to
brand-new station

40. Scenario 5:
Eliminates climbing
and confined-space
entry
New station installs as
a package with
virtually no downtime

41. Workforce capacity is a chronic issue

42. Also: Nobody's as young as we used to be

43. Being at or near the surface means:

Less lifting

Less climbing

Less slip-and-fall risk

Lower flooding risk

More fresh air

More distance between hazards and the operator

More light

More shelter from inclement weather

More access to tools

More options for adaptive technologies

44. Scenario 6:
Deep pit
High costs to excavate
(due to rocks or high
water table)
Need to make use of
every cubic foot of
storage

45. Scenario 6:
Recession minimizes
excavation costs
Staged pumping
options (parallel and
series) can permit
future growth without
new digging

46. Engineers like numbers
(Economists do, too)
But we can't ignore the human side of pumping

47. Counting the human side of pumping
① Hydraulic efficiency

Efficiency declines if
clearance
adjustments aren't
made

Submerged pumps
are rarely
maintained for
clearances

48. Counting the human side of pumping
②The growth of clogs

Users put worse solids in

Appliances dilute with less water

More clogs result

49. Counting the human side of pumping
③The cost of unclogging
A "non-clog pump"
is unicorn talk
Failing to plan is
planning to fail

50. Counting the human side of pumping
④Work days lost to weather

Human beings do better work when the space is clean,
safe, dry, and warm

51. Counting the human side of pumping
⑤The value of an operator's life

Threat #1: Impatient (or over-eager) operators

Threat #2: Inexperienced workers

Threat #3: Aging

52. Counting the human side of pumping
⑤ The value of an operator's life

People make snap decisions to do the unsafe thing "just this once" or "just for a sec"

Safety must be intrinsic by design

53. Counting the human side of pumping
① Hydraulic efficiency

Clearances have to be adjusted for hydraulic efficiency to pay off
② The growth of clogs

Users put worse solids in and dilute with less water
③ The cost of unclogging

A "non-clog pump" is unicorn talk
④ Work days lost to weather

Human beings do better work when the space is clean, safe, dry, and
warm
⑤ The value of an operator's life

Bad choices by impatient operators have to be designed away

54. So, when is it time for recess?
Any time you can't quite do the job
from the surface, but where being
25' closer to the surface
(the height of a streetlight)
is safer than being 25' deeper
in a hole

55. Questions?

Thank you for your time
and attention!

This presentation will be
available at
gongol.net/presentations

Brian Gongol
DJ Gongol & Associates

brian@gongol.net

515-223-4144

@djgongol on LinkedIn,
Facebook, and Twitter

56. Credits

OSHA definition of confined spaces:

https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.146

OSHA confined-space flow chart:

https://www.osha.gov/laws-regs/regulations/standardnumber/
1910/1910.146AppA

Pump station graphics adapted from originals furnished by The Gorman-Rupp Co.

Submersible pump cutaway courtesy of The Gorman-Rupp Co.

Submerged control panel photo taken from Nebraska Department of
Environmental Quality report on flooding at Loomis, Nebraska

No permanent URL available, but report can be found through
http://dee.ne.gov/NDEQProg.nsf/OnWeb/PRS

Photos are the original work of the author