Pressure Study

8/8/2019 Pressure Study

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Analysis and Design to CorrectLow Pressure in a Water

Distribution System

SENIOR DESIGN PROJECTby Dan Bauer, Dan Kranenburg, andRebecca MacIsaac - Seniors in Civiland Environmental Engineering


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The Challenge

Portlands Bureau of Water Supply provideswater to Burlington, just northwest of thecity.

A few residences in the higher elevations of Burlington have experienced very low water

pressures, prompting the Bureau to ask thestudents to investigate possible solutions.


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Burlington

U.P.


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Problem Definition

Low water pressures: Are an inconvenience Violate Oregon State standards Are a potential health risk

Investigate: Reasons for low pressures Potential Solutions

Recommend a solution


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The Setting

The Burlington water supply systemconsists of a pipeline which parallels Route30

Several areas are supplied from the mainpipeline, many of which are at a much

higher elevation The Harborton area is one of these areas - it

has experienced low-pressure problems


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Water Supply SchematicBurlington Water District (Plan View)

ReservoirHarborton

Pump

To Portland

Highway 30

Other Users

Other Users

3 miles


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Reservoir

Elevation at 264 ft Capacity: 200,000 gallons

Height: 15 ft Diameter: 50 ft

10 ftWater Level7 ft


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Pump

Johnston 4-inch submersible pump Designed to engage when reservoir level

drops 3 ft Field data show a 1-inch drop

Elevation at 64 ft Delivers 260 gpm to system


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Purpose and Scope PURPOSE

Analyze Burlington Water System Evaluate possible design solutions

METHODS Computer modeling

Cost comparison GOAL

Recommend final solution to correct low pressure


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Design Guidelines Service at minimal pressure of 20 psi

State requirement

Provide 40 psi if possible

City of Portland Bureau of Water Worksstandard

Zoning restrictions Forest Park

Financial feasibility


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Field Investigation

The water surface elevation in the reservoirwas monitored Fluctuations in the tank were observed to

be only inches, when they should have beenfeet


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Computer Analysis

Data on the physical characteristics of thesystem were determined The data were used with a model of the

water distribution system The model was used to analyze flow and

pressures under four different alternativesolutions


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Alternative Solutions

Neighborhood Standpipe

Hydropneumatic Tank

Continuously Operating Pump with Valve

Additional Pump with Valve


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Alternative I - Standpipe

When pump is on, water fills standpipe When pump is off, a check valve stops the

flow of water back to the lower elevations


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Standpipe

Pump

Check Valve

Standpipe

Harborton

Reservoir

Pump On

Other Users

Direction of Flow


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Standpipe

Pump

Check Valve

Standpipe

Harborton

Reservoir

Pump Off

Other Users

Direction of Flow


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Alternative II - Hydro-pneumatic Tank

When pump is on, water fillshydropheumatic tank

When pump is off, a check valve stops theflow of water back to the lower elevations


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Hydropneumatic Tank Pump On

Hydro. Tank

Pump

Check Valve

Reservoir

Harborton Other Users

Direction of Flow


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Hydropneumatic Tank Pump Off

Hydro. Tank

Pump

Reservoir

Check Valve

Other UsersHarborton

Direction of Flow


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Alternative III - ContinuouslyOperating Pump

When pump is on, the valve is open andboth the Harborton area and reservoir are

filling When the reservoir is full, the valve closes

and pump continues to supply water andprovide pressure to Harborton area


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Continuously Operating PumpValve Open

Harborton

Reservoir

Valve

Other Users

Pump

Direction of Flow


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Continuously Operating PumpValve Closed

Harborton

Valve

Reservoir

Other Users

Pump

Direction of Flow


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Alternative IV - Additional Pump

Two pumps provide water to the Harbortonarea and the reservoir

When the reservoir fills, the valve closesand only one pump operates to supply theHarborton area


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Comparison of AlternativesAlternative Pressure Cost Other

Standpipe 43-54 psi low Forest Park

Hydro Tank 28-55 psi high Large forneighborhood

ContinuousPump

55-73 psi low Wearing of pump

AdditionalPump

55-73 psi moderate Addsredundancy


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Final Recommendation

Additional Pump Provides adequate pressure Low maintenance Moderate cost Adds redundancy


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Pressure Study

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