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Beyond an “Average Day” How Much Water Should Be Stored Dan Barr, PE Burgess & Niple, Inc.
Beyond an “Average Day”How Much Water Should Be Stored
Dan Barr, PEBurgess & Niple, Inc.
Dan Barr, PEBurgess & Niple, Inc.
Introduction
A comprehensive, innovative, and straightforward storage and pumping analysis that will help determine:
Distribution system capabilities during critical conditions
Current and future storage/pumping requirements Determine and test proposed solutions District by district requirements Combines many storage concepts into one analysis. Incorporates minimum turnover requirements No mysterious factors or multipliers
A comprehensive, innovative, and straightforward storage and pumping analysis that will help determine:
Distribution system capabilities during critical conditions
Current and future storage/pumping requirements Determine and test proposed solutions District by district requirements Combines many storage concepts into one analysis. Incorporates minimum turnover requirements No mysterious factors or multipliers
Analysis Components
This analysis determines the minimum required storage volume for each of the following components:
Operational (balancing and turnover)
Fire Protection Outages
This analysis determines the minimum required storage volume for each of the following components:
Operational (balancing and turnover)
Fire Protection Outages
The Three Components of Storage
The Three Components of Storage
Analysis Data Requirements
Water demands by district is ideal Existing system storage volumes Existing pumping capacity
Water demands by district is ideal Existing system storage volumes Existing pumping capacity
Emergency Outages
This component deals with situations when the source(s) for each district is out of service. Assumptions for determining minimum outage
volume:– The minimum number of hours the system must operate on
storage alone– The demands during the outage
The system’s emergency management plan must coordinate with these assumptions
This component deals with situations when the source(s) for each district is out of service. Assumptions for determining minimum outage
volume:– The minimum number of hours the system must operate on
storage alone– The demands during the outage
The system’s emergency management plan must coordinate with these assumptions
Emergency Outage Equations
Minimum Storage Volume Demand (gpm) x Outage Requirement (hours) x
60 (minutes/hour) = Required Volume (gal)
In Millions of Gallons Per Day Demand (mgd) x 1,000,000 gal/mil gal x Outage
Requirement (hours) / 24 (days/hours) = Required Volume (gal)
Minimum Storage Volume Demand (gpm) x Outage Requirement (hours) x
60 (minutes/hour) = Required Volume (gal)
In Millions of Gallons Per Day Demand (mgd) x 1,000,000 gal/mil gal x Outage
Requirement (hours) / 24 (days/hours) = Required Volume (gal)
Fire Protection
This component is sized by determining the design fire in each district.
The design fire is an assumption based on a number of factors– Local fire department requirements– Organizations like ISO, Inc. that publish public fire protection data– Ohio Fire Code
Begin analysis after choosing design fire – How much of required fire flow rate can be delivered by system
pumping– What portion of the design fire will need to be delivered by system
storage
This component is sized by determining the design fire in each district.
The design fire is an assumption based on a number of factors– Local fire department requirements– Organizations like ISO, Inc. that publish public fire protection data– Ohio Fire Code
Begin analysis after choosing design fire – How much of required fire flow rate can be delivered by system
pumping– What portion of the design fire will need to be delivered by system
storage
Fire Protection Equations
Capacity Available for Fire Protection Firm Pumping Capacity (gpm) – Maximum Day
Demands (gpm) = Pumping Capacity available for fire protection (gpm)
Required System Storage [Design Fire Flow Rate (gpm) – Available Pumping
Capacity (gpm)] x [Design Fire Duration (hours)] x (60 minutes/hour) = Required System Storage (gal)
Capacity Available for Fire Protection Firm Pumping Capacity (gpm) – Maximum Day
Demands (gpm) = Pumping Capacity available for fire protection (gpm)
Required System Storage [Design Fire Flow Rate (gpm) – Available Pumping
Capacity (gpm)] x [Design Fire Duration (hours)] x (60 minutes/hour) = Required System Storage (gal)
Operational Storage
This component includes storage volume utilized for: Daily turnover of the tank
– Tank turnover is used to keep stored water fresh Current industry practice and the Ohio EPA’s recommendation:
- Turnover 20% to 40% of the tank every day
Maximum hour balancing– Storage required to supply demands over the system’s
pumping capacity
This component includes storage volume utilized for: Daily turnover of the tank
– Tank turnover is used to keep stored water fresh Current industry practice and the Ohio EPA’s recommendation:
- Turnover 20% to 40% of the tank every day
Maximum hour balancing– Storage required to supply demands over the system’s
pumping capacity
Operational Equations
TurnoverStorage Volume (gal) x Turnover Target
Percentage (%) = Required System Storage (gal)
BalancingMaximum Hour Demand (gpm) – System Pumping
Capacity (gpm)] x 8 hours x 60 (minutes/hour) = Required System Storage (gal)
TurnoverStorage Volume (gal) x Turnover Target
Percentage (%) = Required System Storage (gal)
BalancingMaximum Hour Demand (gpm) – System Pumping
Capacity (gpm)] x 8 hours x 60 (minutes/hour) = Required System Storage (gal)
Total Required Storage Volume Per District
After calculating the three component volumes (emergency outage, fire protection and operational storage) determine the total required volume by: Adding all three components Adding operational component to the larger of the two volumes
for outage and fire protection Sizing the required tankage on the largest of the three
components
Final parameter: Determine if the district has enough average daily demand to
turn over the required storage
After calculating the three component volumes (emergency outage, fire protection and operational storage) determine the total required volume by: Adding all three components Adding operational component to the larger of the two volumes
for outage and fire protection Sizing the required tankage on the largest of the three
components
Final parameter: Determine if the district has enough average daily demand to
turn over the required storage
Maximum Sustainable Storage
• (5)x(average daily demand) = Maximum Sustainable Storage for 20% turnover.
• (4)x(average daily demand) = Maximum Sustainable Storage for 25% turnover.
• (5)x(average daily demand) = Maximum Sustainable Storage for 20% turnover.
• (4)x(average daily demand) = Maximum Sustainable Storage for 25% turnover.
Final Steps
Determine remedies for deficiencies discovered during the process. Problems can be solved by a combination of:
– Increased pumping capacity May solve fire flow problem economically Power or mechanical failures could occur
Increased storage volume– Increases emergency outage capacity without fear of
mechanical or power-related failures– Expensive, might have siting issues
Reduced demands– Usually not possible unless customers can be shifted to
another neighboring pressure district
Determine remedies for deficiencies discovered during the process. Problems can be solved by a combination of:
– Increased pumping capacity May solve fire flow problem economically Power or mechanical failures could occur
Increased storage volume– Increases emergency outage capacity without fear of
mechanical or power-related failures– Expensive, might have siting issues
Reduced demands– Usually not possible unless customers can be shifted to
another neighboring pressure district
Common Situations
Too much storage
Too little storage
Storage in the wrong place
Too much storage
Too little storage
Storage in the wrong place
Questions?
Preformatted spreadsheet with calculations available
Contact:
Dan Barr, PE
Preformatted spreadsheet with calculations available
Contact:
Dan Barr, PE
