Equalization Basin Sizing and Design Considerations

Presented by

David J. Delia, P.E.

AECOM Water Engineer

Overview

• Cost Effective Sizing

• Operational Options

• Design Features

Cost Effective?

STORAGE AND/OR TREATMENT

I/I ELIMINATION

Sanitary Sewer Evaluation Study (SSES)

SMOKE TESTING

DYE TESTING

FLOW MONITORING

TV & CLEANING

STRESS TESTING

Two Approaches

Approach 2 Approach 1

Equivalent Annual Cost (EAC)

Cost per Gallon

Gallon of I/I Removed

Finding the Benchmark Flow Rate

=

Finding the Benchmark Flow Rate

=

Finding the Benchmark Flow Rate

x Storm Factor

Effectiveness %

Treatment

“Sum of RDII Source Correction Efforts Multiplied by Unit Reduction Rates” Method

Benchmark Flow Rate

29.61 gpm

0.025 – 0.55 gpm/ft (based on diameter)

4.73 gpm

Calculation of Cost Effective Removal Potential

• Clean outs • Sewers • Manholes • Direct Connections (Downspouts, Catch Basins)

Cost Effective?

STORAGE AND/OR TREATMENT

I/I ELIMINATION

Treat or Store?

Approach 1 Approach 2

$0

$5,000,000

$10,000,000

$15,000,000

$20,000,000

$25,000,000

$30,000,000

$35,000,000

$40,000,000

$45,000,000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Estimated MG of I/I Removed

Present Worth of R/R vs. Estimated I/I Removal

Cummulative Present Worth of I/I Removal

$0

$5,000,000

$10,000,000

$15,000,000

$20,000,000

$25,000,000

$30,000,000

$35,000,000

$40,000,000

$45,000,000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Estimated MG I/I Removed or Stored

Present Worth of R/R vs. Estimated I/I Removal with Detention Basins

Cummulative Present Worth of I/I Removal Present Worth of Retention Tank Poly. (Present Worth of Retention Tank)

Cost Effective Removal 13.7 MG

1

10

100

1000

45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75

Retu

rn P

eri

od

(years

)

Discharge (MGD)

Log Pearson III Flow Analysis for Monroe WWTP

Q (MGD)

* Area under graph does not equal the required storage volume, but represents the change in capacity to achieve a 10-year return period.

59.6 MGD

1

10

100

1000

45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75

Retu

rn P

eri

od

(years

)

Discharge (MGD)

Log Pearson III Flow Analysis for Monroe WWTP

Q (MGD) With I/I Removed

* Area under graph does not equal the required storage volume, but represents the change in capacity to achieve a 10-year return period.

59.6 MGD

51.5 MGD

0

10

20

30

40

50

60

70

80

0 10 20 30 40 50 60 70 80 90 100

Flo

w (

MG

D)

Hours

Hydrograph

Flow (MGD)

Plant Capacity (45.6 MGD)

Flow less I/I (MGD)

Volume between the blue line and the plant capacity = 14 MG

Volume between the green line and the plant capacity = 7.0 MG

VORTEX GRIT SYSTEM

M

M

M

M M

WET WEATHER CLARIFIERS

WET WELL

P.E.W. WET WELL

P.E.W.

SPLIT CASE HIGH PRESSURE

WET

WEA

THER

FLO

W

Design Features

Throttling Valves > VFDs

Flushing Gates

Water Cannons, Smooth Walls, Mixer Aerator, & Fiberglass Stairs

Commissioning Day

Lessons Learned

• Take the lid off

• Gravity flow

• Pump selection

• Inside stairs

Questions?

Riddle

Question: You have been given the task of transporting 3,000 apples 1,000 miles from

Appleland to Bananaville. Your truck can carry 1,000 apples at a time. Every time you travel a mile towards Bananaville you must

pay a tax of 1 apple but you pay nothing when going in the other direction (towards

Appleland).