Oh the Places You’ll Go… with a Hydraulic Model

Jason Nikaido, P.E.City and County of Honolulu

2015 HWEA Collection Systems ConferenceDecember 4, 2015

Outline

• How we got here• Wastewater Capacity Management and Monitoring• Planning Phase for CIP Projects• Sewer Connection Applications• Construction

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How We Got Here

• 1999 Sewer I/I Assessment and Rehabilitation Program• Flow and rainfall monitoring program• INFIX• XP-SWMM - Trunk model

• 2010 Sewer I/I Assessment and Rehabilitation Program Update• Flow and rainfall monitoring program• InfoWorks CS - All pipes, all parcel model• Migration to InfoWorks ICM• Completed model accepted in 2012• Network update in 2014

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Wastewater Capacity Management and Monitoring• Flow and rainfall monitoring• Model update• Modeling services

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Flow and Rainfall Monitoring

Previous Effort• 100 long-term flow meters• 120 short-term flow meters• 30 rain gauges• Project analysis• Temporary

Current Effort• 51 flow meters• 40 rain gauges• Long term trends• Permanent

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LegendÕ Rain Gauge# Flow Meter$1 Treatment Plant

Model Update

• Recalibrate model using flow and rainfall data• Update water consumption data for dry weather flow estimates• Update network from GIS• Target completion in 2017

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Modeling Services

• Long range planning• Can the collection system handle future flows?• Evaluating multiple flow conditions

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Ohana and Accessory Dwelling Unit (ADU) Potential• Sand Island: 37,301 parcels• Honouliuli: 38,960 parcels• Island-wide: 120,899 parcels

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Transit Oriented Development (TOD) Potential1/2 mile of rail stations

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Zoning

Planning Phase for CIP Projects

Initial model recommendations

Consultant revises recommendations

City verifies design in model

Consultant revises design / City reruns model

Project continues with verified

design

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Sewer Connection Applications

• DPP Wastewater Branch transitioning to use InfoWorks model• Application of flow chart using model results

• 5-year level of service• Predicted SSOs• Dry weather flow• Wet weather flow• Surcharge levels

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Have there been anyhistorical wet weatherSSOs downstream?

Deny SCA

Does the model predict 5-year LOS peak wet

weather SSOsdownstream?

Is the number ofEDUs > 3?

Is the pipe diameter< 12-inches?

Is the peak dry weatherflow (PDWF) d/D > 0.75?

ApproveSCA

Is the 5-year LOS peak wet weather flow (PWWF) surcharge > 3 ft

or freeboard < 8 ft?

- Are deficiencies not backwater related (i.e. surcharge = 1, PS wetwell backup,pipe diameter changes)?

- Is number of consecutive, deficient pipe(surcharge =2) segments > 3?

- Is headloss > 1 foot/1,000 ft?

ApproveSCA

Are there capacity deficienciesat downstream pump stations

and/or treatment facilities?

Deny SCA

Yes

No

No

Yes

No

Yes

Yes

Yes

No

No

No

No

Yes

No

Is the number ofEDUs >=500?

Yes

No Yes

Evaluate deficientpipe segments.

Is the maximum freeboard(distance from crown to ground) <= 4 feet?

No surchargeallowed.

Input population/flowsand re-run model.

Is there surcharge during the5-year LOS peak wet weather flow?

YesYes No

Are there any potential operations and/or maintenance issues?- PM frequency- PM activity- Dry weather spills

Yes

Yes

No

Consult with CSM

Are there any operations and/or maintenance issuesthat significantly increase

spill risk?

Deny SCA

No

No

Yes

Construction

• Sewer bypass flows• Example: CIPP Guideline

• Pipe diameters <= 10-inches• Peak 2-year flow (greater of 6 or 24-hour storm)

• Pipe diameters > 10-inches• Lesser of:

• Peak 2-year flow • 2.5 times the peak daily flow

• Balance bypass cost and risk• Only a guide, specific situations may warrant higher bypass flows

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Summary

• Model is a tool that can be used across the wastewater program• Model has limitations• Work in progress• Technological advancements will increase functionality

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Questions?