HomeMy WebLinkAbout03/17/1992, 7 - STUDY ITEM - CONSIDERATION OF REPORT EVALUATING THE WATER OFFSET PROGRAM. lll��ltlllll�lllllll�l Ilulll MEETING DATE:
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COUNCIL AGENDA REPORT ITEM NUMBER:
FROM: Arnold B. Jonas, Community Development Director
PREPARED BY: Glen Matteson, Associate Planner
SUBJECT: Study item - consideration of report evaluating the
water offset program.
CAO RECOMMENDATION
Retain the toilet retrofit/development off-set program as an
appropriate part of an overall sustained water conservation
program and provide direction if changes are desired in the
program.
BACKGROUND
The Council has asked for an evaluation of the offset program,
under which builders may proceed without water allocations if
they save twice the required allocation by retrofitting existing
buildings in the city. Staff is presenting a report.
The report concludes that water use by all customers has declined
dramatically during the last four years; water usage by
retrofitted customers has declined slightly more than usage by
all customers. There are too many variables and insufficient.
consistent data to conclude how close predicted long-term savings
are to actual long-term savings, mainly because retrofitting was
done at the same time the City implemented mandatory water
conservation. More time is needed to see if water use in
retrofitted buildings stays down while use in buildings that have
not been retrofitted trends upward as mandatory conservation is
relaxed.
ATTACHMENT
"Evaluation of the Water Offset Program"
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EVALUATION OF THE WATER OFFSET PROGRAM
February 1992
City of San Luis Obispo
Purpose
This study evaluates the effectiveness of the water offset program, commonly referred to
as "the retrofit program." Water usage has been tracked in a sample of multifamily,
motel, and commercial properties which were retrofitted under that program. This study
does not evaluate the effectiveness of the toilet-retrofit rebate program, which is being
evaluated separately. Water usage in houses was not closely examined in this study,
because single-family houses have been a small part of retrofit activity under the offset
program, and nearly all of the activity under the rebate program.
Conclusion and observations
Water use by all customers has declined dramatically during the last four years; water
usage by retrofitted customers has declined slightly more than usage by all customers.
There are too many variables and insufficient consistent data to conclude how
close predicted long-term savings are to actual long-term savings, mainly because
retrofitting was done at the same time the City implemented mandatory water
conservation. More time is needed to see if water use in retrofitted buildings
stays down while use in buildings that have not been retrofitted trends upward as
mandatory conservation is relaxed.
Retrofitting, and the projects enabled by it, have not substantially influenced
total, citywide water usage during the short term. (Several of the projects for
which developers retrofitted have not been built.)
Savings of individual retrofitted customers range from significantly more to
significantly less than predicted.
Through July 1991, when the evaluation was conducted, about eleven percent of
all potential properties had been retrofitted under the offset program, and about
six percent under the rebate program.
If the projected water savings from the offset program are correct, long-term
citywide water usage would be about one percent lower, considering the savings
in properties retrofitted through December 1991 and the expected usage in the
projects to be built. If there are no long-term savings due to retrofitting, long-
term usage would be about one percent higher. As more properties are
retrofitted to enable construction, the range of long-term effects increases to plus
or minus six percent, which would be reached when all eligible properties are
retrofitted (assuming no substantial additional retrofitting under rebate or other
programs).
Offset evaluation 2
Background
The City's Water Allocation Regulations (Municipal Code Chapter 17.89) allow certain
amounts of development according to relationships between water supplies and water
use. According to the regulations, a project needing a water allocation to be built may
be made exempt from waiting for an allocation if the developer changes existing
facilities (does "retrofitting") that will save twice the needed water allocation.
The offset program is intended to deal with long-term conditions: water use in the
project to be built and in the retrofitted properties over the next 30 to 50 years. The
offset option was included in the regulations before mandatory conservation (rationing)
was seriously considered. The rationing program is intended to avoid running out of
water for the duration of the drought, over a span of perhaps six years. At the start of
the offset program, staff developed what were intended to be conservative, yet realistic,
estimates of water savings from specific retrofit features. However, the offset program is
an experiment with an outcome that will be influenced by people's behavior, not simply
an application of mechanical rules.
By the end of December 1992, 85 projects had completed retrofitting in 2,500 dwellings
and motel units and 44 buildings of other kinds. The expected total water usage
reduction in retrofitted properties due to these projects is 172 acre-feet annual water
usage. If the water savings factors are correct, the net citywide savings is about 86 acre-
feet, considering the expected usage of the new developments enabled by retrofitting.
There are about 20,000 dwellings and motel units in the City. Total water use before
mandatory conservation was about 8,000 acre-feet. Currently, annual water use is about
5,000 acre-feet.
The City's water savings factors, used to determine offset credits for most proposals
involving toilet and showerhead replacement, are based on City water use histories,
federal surveys of water use in projects with low-flow fixtures, Morro Bay's experience
with the first several years of that city's program, and an extensive study prepared for
the City of Santa Barbara. For some proposals, offset credits are calculated using
expected reductions due to specific modifications to equipment. The water use factors,
which determine the amount of allocation needed for a development project, are
generally based on five years of pre-rationing water use by various kinds of buildings.
In addition to properties retrofitted under the offset program, by July 1991, 1,091
accounts (nearly all single-family dwellings, representing 1,748 toilets) had done
retrofitting under the rebate program. There is no overlap between the two programs.
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Offset evaluation 3
Data Summary
Staff completed a first phase evaluation in October 1990, by examining about 400
apartments and 60 motel rooms, and some other types of buildings, that had water
billing records for at least one full billing period (two months) during rationing and
before retrofitting as well as one full billing period during rationing and after retrofitting.
About one-half the addresses had only two months of usage history after retrofitting,
about one-half had four months, and only a few had more than four months. Usage
history before retrofitting typically spanned ten to 14 months. The results showed that
actual savings were about two-thirds of predicted savings. However, the data are not
considered reliable since they came from such a short period, during which seasonal
changes and other factors probably obscure changes due solely to retrofitting
In November 1990, staff began a second-phase effort to track water use in selected
retrofit projects. The intent was to take a close look at a manageable number of
projects, rather than to track usage in many accounts. The projects were selected as
follows, without prior knowledge of the effectiveness of retrofitting:
The two highest-volume users in each category:
Apartments with primarily students
Apartments with senior citizens
Apartments with mixed ages/occupations
The three highest-volume users in each category:
Motels
Other types of development, as a group
Water use tracking began in January 1986 and extended through early June 1991.
Among the selected projects, the first retrofit occurred in July 1989 and the last in
September 1990. The results are summarized in Table 1.
Actual savings for residential projects were about eight percent more than predicted
savings. Savings in nonresidential projects were about three times the predicted savings.
Overall, actual savings were about 2.4 times predicted savings. The reduction due to
retrofitting, separately from other contributing factors, can only be inferred.
Table 1 shows the wide variations in apparent retrofit effectiveness among different
types of projects, and how the overall results can be dominated by one or two sample
properties.
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Offset evaluation 4
Table 1
Actual and Predicted Use and Savings
for Major Retrofitted Water Users:
Before and During Mandatory Conservation
Average use before Average use after Actual Predicted
Project retrofittingretrofitting Savins Savings
(all in 100 cubic feet per billing period)
#1, #2 combined
Student apts; 128 of
166 units retrofitted 2,682 17793 889 546
#3 Senior apartments
18 of 20 units retrofitted 138 78 60 86
#4 Senior apartments
94 of 108 units retrofitted 877 469 408 394
#5 Mixed age, suburban apts.
47 of 49 units retrofitted 680 650 30 205
#6 Mixed aged, downtown apts.
24 of 24 units retrofitted 146 92 54 104
Residential Subtotal 4,523 3,082 1,441 1,335
#7 Motel
35 of 40 units retrofitted 384 309 75 102
#8, #9 combined; motels
55 of 55 units retrofitted 329 141 188 222
#10 Student group
housing 3,825 1,461 29364 507
#11 Hospital 8,698 5,383 3,315 703
#12 Carwash 479 270 209 287
Nonresidential Subtotal 13,715 7,564 6,151 1,821
TOTAL. all projects 18,238 10,646 7,592 3,156
Source: City of S.L.O. Community Development Dept. & Utilities Dept., July 1991
7-S
Offset evaluation 5
Also, the sample retrofitted properties were compared with all properties. Since about
17 percent of potential locations had been retrofitted when the data were gathered, the
comparison between retrofitted locations and all locations is expected to be about the
same as a comparison of retrofitted locations and non-retrofitted locations. Table 2
summarizes the results.
The first line in Table 2 simply converts the last line of Table 1 into acre-feet per year.
The second line shows, also in acre-feet, what the water usage and reduction for the
retrofitted properties would have been, if their usage (based on 1986 and 1987 meter
readings) had been distributed throughout billing periods the way citywide usage was
distributed. In other words, water usage in the retrofitted properties would have shown
this reduction if those properties had followed the citywide trend of water usage.
The second line shows how the sample retrofitted properties' water usage would have
changed if they had followed citywide trends, reflecting voluntary and mandatory
conservation and rate increases, but with little influence from retrofitting.
The 41 percent reduction in actual usage is about equal to the 40 percent reduction that
was calculated based on the citywide trend, indicating that retrofitting probably has
saved little water, in the short term, in comparison with mandatory conservation and
other factors.
Table 2
Actual and Predicted Use and Savings
By Major Retrofitted Water Users
vs. Citywide Usage Trends:
Before and During Mandatory Conservation
Average use Average use Actual Predicted
Description before retrofit after retrofit Savings Savings
(acre-feet annual usage)
Retrofitted sites,
measured 251 147 104 (41%) 43
Retrofitted sites,
if citywide trend 297 177 120 (40%) (not
was followed applicable)
Source: City of S.L.O. Community Development Dept. & Utilities Dept., August 1991
FJ—
Offset evaluation 6
Study methods
To get a clear answer on the effectiveness of retrofitting alone, we would have to look at
water-use records for a large sample of retrofitted units, when each of the following
determinants of water use would be about the same before and after retrofitting:
Vacancy rates;
Average household size;
Target water use levels (the level of mandatory conservation, if any);
Water costs in relation to incomes or a broad price index;
Rainfall, temperature, humidity and wind;
Economic conditions (occupancy of motels, patronage of businesses).
This approach was not possible, mainly due to the imposition of mandatory conservation
about the time retrofitting was done.
It is also possible to evaluate one of several features contributing to water use changes
through a statistical technique called "multiple regression," but one must have reliable
indicators of the other features. Such indicators, particularly the last two listed, would
be difficult to obtain for San Luis Obispo.
The City's "water usefactors" were determined using a more simple method: averaging
usage over five years before rationing (1981 through 1985), and assuming that future
conditions would not be too different from those past conditions, in the long term. Any
error was likely to be on the side of requiring larger allocations, and therefore avoiding
not having enough water for the whole community.
Looking at water use before rationing and during rationing is bound to show a decline,
whether or not retrofitting is effective. Total water use will decline due to brown lawns
and short showers, regardless of toilet and shower-head gallonage. Likewise, a
comparison of usage during rationing with usage after rationing is bound to show an
increase, even if retrofitting has been effective. Further, any comparison of short
intervals can easily be skewed up or down by seasonal differences in a few large projects
(such as motels or student housing complexes) in the retrofit sample. This limitation is
a serious flaw in the first phase evaluation described above, and a consideration in the
second phase.
Notes on second phase evaluation:
Predicted savings from the sample properties represented about 27 percent of the
total predicted savings from retrofits completed through June 1991.
Some of the dramatic savings among the retrofitted properties may have been
due to large water users totally eliminating landscape irrigation about the same
time toilets, showerheads, and faucets were retrofitted. This was the case in
Project #10 (student housing) of Table 1. For Project #11 (hospital), predicted
1- 7
Offset evaluation 7
savings were estimated by the plant engineer and verified by staff. They included
substituting basement drainage outflow for all City water in landscape irrigation,
but the plant engineer could not account for the actual savings. The hospital's
water use did increase dramatically from 1981 - 1985 to 1986 - 1989, with the
retrofit apparently reducing consumption to the earlier period's level. The
retrofit activities may have corrected a leak or other problem which was not
consciously accounted for.
The comparison in Table 2 uses January/February 1986 through the first retrofit
completion date, July/August 1989, as "before" retrofitting, and the following
billing periods through May/June 1991 as "after" retrofitting. Choosing a cut-off
on other dates between the first and last retrofits in the sample does not
substantially change the results.
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