THE FINANCIAL BENEFITS OF WATER CONSERVATION: THE TUCSON STORY

CANDICE RUPPRECHT

WATER CONSERVATION

MANAGER

TUCSON WATER

PETER MAYER, P.E.

PRINCIPAL

WaterDM

MARY ALLEN, P.E.

BUSINESS PROCESS IMPROVEMENT

PIMA COUNTY REGIONAL WASTEWATER

RECLAMATION

AWE AVOIDED COST STUDY

• Alliance for Water Efficiency grant funds from Walton

Family Foundation focused on Colorado River Basin

Initiative

• WaterDM and City of Westminster Study

• Tucson, AZ and Gilbert, AZ selected to participate

• Goal of the study is to examine the impact of increased

water use efficiency on customer rates

WATER USE IN THE US, 1900 - 2010

Includes fresh and saline

water. Source USGS and

Pacific Institute 2015

M&I WATER USE IN THE US, 1900 - 2010

Source USGS and

Pacific Institute 2015

TUCSON WATER ANNUAL PRODUCTION (1940-2016)

CAP ProductionPotable Production TARP Production Reclaimed Production

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

Wate

r P

rod

ucti

on

fo

r T

W S

erv

ice A

rea (

Acre

-Feet)

1940 1950 1960 1970 1980 1990 2000 2010Year

2016 2016

CAP

Reclaimed

Water

TARP

Total Potable Water Use at 1985 Level

RESIDENTIAL INDOOR GPCD

69.3

58.6

36.7

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

REU1999 REU2015 High-Efficiency (Aquacraft2011d)

Ind

oo

r A

vera

ge G

allo

ns

Per

Cap

ita

Per

Day

(gp

cd)

Source: Water Research Foundation (2016) Residential End Uses of Water Update – #4309.

Denver, CO.

1999 vs. 2016 =

15.4% reduction

2016 vs. HE =

37.4% reduction

INDOOR GPCD COMPARISON

ToiletClotheswasher

Shower Faucet Leak Other Bath Dishwasher

REU1999 18.5 15.0 11.6 10.9 9.5 1.6 1.2 1.0

REU2015 14.2 9.6 11.1 11.1 7.9 2.5 1.5 0.7

0

2

4

6

8

10

12

14

16

18

20

Gal

lons

per

cap

ita

per

day

(gpc

d)

Source: Water Research Foundation (2015) Residential End Uses of Water Update – #4309. Denver,

CO.

Statistically significant

reductions in:

• Clothes washer

• Toilet

• Dishwasher

WATER EFFICIENCY IS NOT ONE, BUT MANY APPROACHES

• Utility-sponsored conservation & education programs

• Rebates, Youth & Professional Education

• Community outreach campaigns: Pete the Beak; Water Reliability

• Increasing block rate structures

• 4-Tier structure: $1.55,1-7 ccf; $3.00, 8-15 ccf; $7.48, 16-30 ccf; $11.75 > 30 ccf

• Local ordinances: Xeriscape Landscaping (1991), Water Waste (1984) & Comm.

Rainwater Harvesting (2008)

• International Plumbing Code Tucson Plumbing Code

• National Policy that drives Innovation & technology improvements

• Energy Star (2002) & WaterSense (2006)

0

20

40

60

80

100

120

140

160

180

19

85

19

86

19

87

19

88

19

89

19

90

19

91

19

92

19

93

19

94

19

95

19

96

19

97

19

98

19

99

20

00

20

01

20

02

20

03

20

04

20

05

20

06

20

07

20

08

20

09

20

10

20

11

20

12

20

13

20

14

20

15

SF H

ou

seh

old

Avg

. An

nu

al U

se (

CC

F)

1960s & 1970s

Typical landscape

Preferences shift…

A typical landscape today

SINGLE FAMILY AVG. ANNUAL USE 1985 - 2015

Present-day

Typical landscape

0

20

40

60

80

100

120

140

160

180

200

Syst

em G

PC

DTOTAL SYSTEM GPCD

1980 - 2015

188

130

105

78

512,000

717,875

-

20

40

60

80

100

120

140

160

180

200

1989 2015

-

100,000

200,000

300,000

400,000

500,000

600,000

700,000

800,000

Gallo

ns

per

Capita P

er

Day

Popul

ation

System Per Capita Water Use (gallons/day)

System Per Capita Wastewater Use (gallons/day)

Service Area Population

POPULATION AND PER CAPITA WATER AND WASTEWATER USE

1989: 188 / 107 gpcd

Pop. 512,000

2015: 130 / 79 gpcd

Pop. 717,875

96.493.3

134.4

54.0 56.2

80.0

0.0

20.0

40.0

60.0

80.0

100.0

120.0

140.0

160.0

1989 2015 2015 Hypothetical

Avg

. D

aily

Pro

duc

tion/

Flo

w (M

GD

)

Water Wastewater

HYPOTHETICAL, NON-CONSERVING WATER DEMAND

Daily Water

Production &

Wastewater Flows:

-1989 actual

- 2015 actual

- 2015 hypothetical

“WHY ARE MY RATES GOING UP AGAIN WHEN

I KEEP CONSERVING WATER?!”

• Due to conservation, per capita water use in Tucson has

dropped 45% and wastewater by 35% since 1989.

• Yet…. costs to customers continue to increase.

• Some customers are confused and frustrated.

• What is the impact on water and wastewater rates

due to conservation?

WATER SYSTEM AVOIDED COSTS

• Water Treatment Infrastructure

• Pumping & transmission expansion

• Water Resources

• Operating Costs

How Much Additional Cost

to Tucson Water meet non-

conserving, hypothetical

demand of 134 mgd?

WASTEWATER SYSTEM AVOIDED COSTS

• 2015 Avg. Daily Flow ~ 56.2 MGD

• Hypothetical Non-Conserving Avg. Daily Flow ~ 80 MGD

• Current System Max. Treatment Ability ~ 95 MGD

• In this analysis, wastewater treatment capacity water increased

to 107 MGD to meet Hypothetical Non-Conserving Daily Flow

range

What additional wastewater

system infrastructure and costs to

meet 80 mgd avg. daily flow?

ADDITIONAL COSTS OF MEETING A NON-CONSERVING DEMAND…

THAT HAVE BEEN AVOIDED

• Additional $22 million per year for water system O&M

• $140,000,000 for new Avra Valley Transmission Main CIP

• $15 million for new 7 MGD recycled water facility

• Additional $6.4 million per year for wastewater treatment O&M

• $195,000,000 for additional 12 MGD of wastewater capacity,

financed over time

CUSTOMER RATE IMPACT

• Current avg. single-family, water customer uses 98.9 ccf/year, and pays

for 84 ccf/year of wastewater treatment.

• At current water rates, the avg. single-family customer pays $847 per year

for water and sewer.

• Under the non-conserving scenario (assuming 188 gpcd) the average

single-family customer would pay $976 per year for water and sewer.

Due to water efficiency, rates today are nearly

15.3% LOWER than otherwise necessary.

74.0

97.2

63.0

82.8$847

$976

$-

$200

$400

$600

$800

$1,000

$1,200

0

20

40

60

80

100

120

2015 Actual Non-Conserving Hypothetical

Ann

ual W

ate

r &

Wast

ew

ate

r Bill

-$

Ann

ual W

ate

r and

Wast

ew

ate

r U

se (kg

al)

Impact to an Average Single-Family Customer - Tucson, AZ

Water Use (kgal) Wastewater Discharge (kgal) Annual Water & Wastewater Bill - $

BREAKDOWN OF AVOIDED COSTS

Water Transmission, 11.8%

Reclaimed Water, 0.0%

Interest and Debt Service, 17.0%

Water Treatment Operation, 38.6%

Wastewater Treatment, 21.8% Wastewater Treatment

Operation, 10.8%

Tucson Water rates are

22.3% lower today and

Pima County WR rates are

7.8% lower today

than otherwise necessary if

per capita water demand

had not been reduced.

STRENGTH OF SEWER FLOWS

216

429

205

338

22781

20424

18000

18500

19000

19500

20000

20500

21000

21500

22000

22500

23000

23500

0

50

100

150

200

250

300

350

400

450

500

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016

Flo

w in

Mill

ion

Gal

lon

s/ye

ar

Ave

rage

Str

engt

h (

mg/

L)/y

ear

TSS BOD Combined Influent Flows for Agua Nueva and Tres Rios

IMPACT TO THE SEWER PIPES

• Scour velocities may take longer to attain in

newer developments with lower flows

• Flushing of pipes may be required

• Potential for more odors in pipes

• Potential for corrosion in pipes

• Terminal ends may require steeper slopes

• Cost goes up for deeper sewers

FLUSHING THE PIPES

PIPE MAY REQUIRE STEEPER SLOPES

Table 5.1 Minimum Slopes for Gravity Sewer Lines

Pipe Diameter (inches)

Minimum Slope (ft/ft)

*Full-Flow Velocity (ft/sec)

6 (terminal reach) 0.0110 3.0

8 (terminal reach) 0.0100 3.5

8 (non-terminal reach) 0.0044 2.3

10 0.0025 2.0

12 0.0019 2.0

15 0.0014 2.0

18 0.0011 2.0

24 0.0008 2.0

*Manning’s (n) value of 0.013 used

ODORS AND CORROSION

Bottom Line: When Everyone Conserves, Everyone Saves

• Water and wastewater rates have increased because of the increasing

costs of providing 24/365 service, while maintaining and improving

infrastructure to meet regulatory treatment requirements.

• Decreasing demands are a balancing act: Revenue v. Resources

• The typical Tucson single-family customer pays 15% less today,

than they would need to be if water efficiency had not been

achieved.

QUESTIONS & DISCUSSIONTHANK YOU!

MARY.ALLEN@PIMA.GOV

CANDICE.RUPPRECHT@TUCSONAZ.GOV