99ebook com-5 storagetanksmanagement

8/12/2019 99ebook Com-5 StorageTanksManagement

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Storage Tank Management

Water & Wastewater Utility Operation andManagement for Tribes


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Water Storage

Why? What kind? Inspection Maintenance Corrosion control Cold weather considerations

EPA publication 816-K-03-002 Koester Associates, Inc.

www.westsussexda.fsnet.co.uk


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Water Storage Purpose Why?

Supply & demand equalizing Power cost savings Emergency & fire needs Surge relief Chlorine detention time increase Blending water from different sources Convenience!


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Storage Types Elevated Tanks

Dunham Engineering


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Storage Types Reservoirs

Dunham Engineering


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www.aquastore.com

Storage Types Standpipes

www.waterworld.com


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Storage Types Pneumatic Tanks

Dunham Engineering


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Who Should do the Inspection?

You? A professional?

Modern Technology?

tankdiver.files.wordpress.com

potablewatertankcleaning.com

www.ronperrin.com


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Inspection Items

Foundation: settling, cracks, deterioration Overflow pipe and valve Interior and exterior coating systems Water quality Water level indicator Surface tanks:

Roofs

Air vents Ladders Hatches

Pressure tanks


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Foundation/Containment Structure

Check for: Subsidence and uneven settlement Corrosion (cracking & spalling) Cracks

Other deterioration

inspectapedia.com geerassociation.org Dunham Engineering


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Overflow Pipe and Valve

Sufficient size Condition

Supported pipe Corrosion

Obstruction Screening (avoid animals/insects)

Valve: Accessible Operable/functional

Drainage Sufficient size

Erosion control

Dunham Engineering


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Altitude Valve

Controls tank level Refill tank Prevent overflow

Can be 1- or 2-way

Similar issues to theoverflow valve Sizing Condition Access Operation


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Interior & Exterior Coating

Steel reservoirs or tanks: Inside/outside paint prevents corrosion

Concrete tanks: Waterproofing can seal surface cracks

Protective coating systems: Adhesion Peeling or rusting areas Materials (lead?) Ice or other damage (e.g., from

welding or gunshots) Meet NSF Standard 61 if in

contact with potable water Dunham Engineering

inspectapedia.com


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Water Quality

Water sampling (e.g., at drain connection) Suspended solids Turbidity (cloudy?) Odor

Birds, rodents, and insects at access points orwithin the tank

Bottom sediment or sludge

potablewatertankcleaning.com

AWWA


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Water Level Indicator

Pressure gauge Reading in psi or feet of water Adequate reading for tank height

Float-style indicator Cable access opening protected Float moves freely Target reads properly

Supervisory Controland Data Acquisition(SCADA)

Horsley Witten Group

Dunham Engineering

Dunham Engineering


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Roofs

Low spots where water may pond Min. 0.75/12 slope (AWWA D100) Recommend 1/12 slope & thick

Holes along seams

Support columns, rafters, and connections

Dunham Engineering tankdiver.files.wordpress.com


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Air Vents

Proper design Min. 24 Downward-facing cover

Screened to keep animals

and birds out #16 mesh No hardware cloth

Sealed edges & seams Gaps < 1/16 No holes in vent cover

Dunham Engineering

tankdiver.files.wordpress.com


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Access Ladders

Ladder rungs 12 apart Safety:

Cage around ladder Rail-type safety system

Above ground restrict access Ladders supports spaced 10 apart max.

Dunham Engineering


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Hatches

Proper design 30 diameter (or square) opening 4 raised curb

Closes properly (no gaps)

Locks

Dunham Engineering www.swregional.net


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Hydro-pneumatic Tanks

Take inspections seriously!

Annual pressure tank inspections must ensure: Pressure release device is working properly Pressure gauge is working properly Air-water ratio is maintained at the adequate level Rubber gasket is replaced

meridithcorp.com www.frwa.net


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Maintenance: Cleaning & Disinfection

Disinfect tanks after inspection and cleaning

AWWA Standard C652-92 Disinfection of Water-StorageFacilities

Procedure similar to disinfecting water mains

Add chlorine to water filling tank Maintain chlorine residual of at least 50 mg/L for 6

hours minimum Carefully dispose of the disinfection water

For large tanks: Collect samples while filling, or Spray walls with highly chlorinated water


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Maintenance: Steel Tank Issues

Repair and replacement of protective coatings Lead abatement

Containment Competent Person

Corrosion damage Repair/replacement

of rafters Repair/replacement of hatches and appurtenances Repair of pitting to

> Prevent leaks> Maintain structural integrity

Dunham Engineering


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Maintenance: Concrete Tank Issues

Leak repairs Cracking and spalling of concrete over time Concrete doesnt rust, but reinforcement does Typically costs more to build, but less to

maintain

Dunham Engineering Dunham Engineering


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Corrosion Why does it happen?

Corroding water tank is like a battery: Walls = anode provides electrons Water = cathode receives electrons Tank corrodes as electrons leave the steel wall

The electrons (-) in

the steel tank

move into the water

causing corrosion


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Cold Weather Considerations - Ice

Keep water moving! Overflow pipe

Keep clear of ice If clogged, water will flow from

the air vent and freeze, the addedweight could topple the tower

Water tower riser Protect it from freezing If pipe large enough, may partially

freeze on the outside and stillallow flow inside

LA Times

gtluke.com


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Cold Weather Considerations - Ice

Ground-level tanks less likely to freeze Elevated tank

If frozen, costly to thaw Ice can deform walls

If drained, must be disinfected

Koester Associates, Inc.

Keep water moving!


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What Have We Learned?

Various types of tanks

Inspection & Maintenance

Corrosion control

Cold weather issues

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