Drinking Water State Revolving Fund
Green Project Reserve Business Case Examples
Water
Efficiency
Summary
Replacement of 24,000 feet of pre-1930s lead-jointed cast iron (CI) distribution pipe with new 8-inch to 16-inch ductile
•
iron (
DI
) pipe to eliminate the loss of 115 million gallons of water per year (
MGY
), equal to 10% of total production and 52% of total system water loss.
SRF loan amount = $2,500,000
•
Water saving (green) portion of loan = 100%
•
Annual water savings = 115 million gallons (
MG
)
•
Background
The water distribution system has approximately 80 miles of CI and
DI
distribution pipe ranging from 6 to 16 inches
•
in diameter. The water system is 100% metered and includes a master meter (or production meter) at the source water supply (after treatment).
As par t of a water loss management plan,
•
1 the water utility calibrates all water meters every 5 years and conducts a leak detection survey every 2 years. Over the past 5 years the utility performed a physical condition assessment of 1% of the distribution pipes. The pipes were selected for assessment based on historic leak detection survey data.
Based on the assessment of 1% of the pipe, the utility concluded that the pre-1930s distribution pipe is in the o poorest condition, has incurred the most leaks, and is most critical to replace.
Pre-1930s
pipe accounts for 17% (13.6 miles) of the 80 miles of distribution pipe. This project will replace 24,000 feet of
•
pipe (4.5 miles or approximately 33% of the pre-1930s pipe) with 8-inch to 16-inch
DI
pipe.
The remaining 83% of the distribution system includes
DI
pipe installed between 1950 and 2000. Because this o pipe has been found to be in better condition, there is no alternative pipe replacement project that would yield the same (or better) water efficiency gains.
In 2010, the water treatment plant processed an average of 3 million gallons per day (
MGD
) or 1,095
MGY
. Based on
•
the water balance, the system had an authorized water consumption of 875
MGY.
The total system water loss of 220
MGY
is the difference between the water produced and the authorized consumption .
The system water loss is comprised of the following:
•
Apparent losses of 0.05% based on water meter accuracy = 5.48
MGY
(assume no losses due to unauthorized o consumption or theft)
Real losses = 214.52
MGY
o
Transmission and distribution main leaks = 210
MGY
ú
Storage tanks/overflows = 2.52
MGY
ú
Service connection leaks = 2
MGY
ú
2
The real losses correlate to 74.78 gallons/connection/day.
•
3
Results
175 pipeline repairs were made during the last year. The highest frequency of r epairs was in the pre-1930s pipes and
•
equally distributed among all sizes.
4
In addition to the leak repair records, the leak detection survey, and condition assessment assisted with determining which sections of distribution mains are most prone to leaks and are the highest priority for replacement.
5
The utility concluded there is minimal water loss in pipes installed after the 1930s and estimates the 210
MGY
of water
•
loss through the distribution pipe is primarily from the pre-1930s pipe.
1
Water Loss Management Plan for the Hypothetical Drinking Water System. February 2011.
2
Leak Detection and Condition Assessment for the Hypothetical Drinking Water System. Updated August 2010.
3
The system has 7,859 connections.
4
Water Loss Management Plan for the Hypothetical Drinking Water System. February 2011.
5
Leak Detection and Condition Assessment for the Hypothetical Drinking Water System. Updated August 2010
•
approximately 115
MGY
of lost water.
6
The estimated 115
MGY
of water loss from the pre-1930s pipe is 52% of the overall water loss of the system: 115
/
220 =
•
52%.
Conclusions
By replacing the 24,000 feet of pipe, the utility anticipates conserving 115
MGY
(52% of overall water loss); therefore,
•
reducing the volume of water withdrawn, treated, and pumped from the reser voir. The cost to pump and treat water is $1.53 per 1,000 gallons. Cost savings from reduced leaks are estimated at $175,950
•
(115,000
*
$1.53). The simple payback period of the loan is 14.2 years.
Additional benefits include reductions in unnecessary pumping and operation and maintenance expenditures, and
•
eliminating potential health hazar ds associated with waterborne pathogens entering the water distribution system.
The energy savings of avoiding pumping the 115
MGY
in water lost from the reservoir to the service connection, an
•
elevation difference of 200 feet, is 103,600 kilowatt-hours (kWh) per year. The carbon emissions av oided from reducing this electricity consumption are equivalent to 74.4 metric tons of carbon dioxide.
7
(Note that the energy savings and carbon reduction calculations are not required for water efficiency business cases.)