1991-03-04 CFRPC to LC Fortner erc
central florida regional planning council
MEMORANDUM
TO: L.C. Fortner, City of Okeechobee
FROM: Jeff Hopper, Regional Planner
DATE: March 4, 1991
RE: Potable Water LOS Calculations
As I promised, I have gone back through my calculations that led to potable water level of
service and persons per connection numbers used in the Comprehensive Plan. As it turned
out, some minor updates and corrections were needed, so this exercise will benefit both of
us. In the discussion below and the attached printouts, I will try to do two things: first,
explain how we arrived at the figures used in current version of the Sanitary
Sewer...Element, which was written over a year ago; and second, note what changes need
i•F to be made before the plan's adoption date so that everything will be up-to-date.
Keep in mind that the number-crunching I do from a planning standpoint is rather basic, and
may not be everything you need to address the engineeihrb aspects of designing a water
system.
There seems to have been some confusion about the level of service, or per-capita
consumption rates, discussed in the plan and what they mean. The plan's current level of
service figure of 142 gallons/capita/day is based on the figures shown in Attachment A for
annual daily flow, number of connections, city and service area population, etc. The
recommended Year 2000 level of service of 119 g/c/d is based on an assumed 15% reduction
in water consumption from present levels. This latter figure is now wrong because City
Council approved a 10% reduction rather than 15%, and because an outdated estimate of
city population was used in calculating it.
Regardless of whether these numbers are correct as currently shown in the plan, it is
important to understand the difference between them. Current level of service
(approximately 140 g/c/d by every methodology we've tried) is nothing more than the existing
consumption rate for average daily flow divided by the total population of the area being
served. This calculation includes city residents with potable water service, connections to the
city system lying outside the city, and the Okeechobee Beach Water Association (OBWA).
for desoto, hardee, highlands, okeechobee, polk counties
p.o.box 2089*490 east davidson*bartow, florida*338304(813) 534-7130*s/c 549-7130*fax (813) 534-7138 sic fax 549-7138
The other number, whether it is 119 g/c/d or something else, is a policy statement that the
city will provide a minimum amount of water for each person using the system. By including
this standard in the plan's Goals, Objectives & Policies document, the city is adopting it into
law. This means the city must provide, or require someone else to provide, whatever system ,)
linpiuveuicnts ale itecessaiy to maintain the standard. In Okccchobee's case, the minimum
standard is intended to be 10% less than current consumption.
Whatever number is adopted as a minimum standard, I would think it makes sense from
your standpoint to base a plant expansion on the current level of consumption rather than
the minimum adopted level of service. By providing somewhat more capacity than the plan
says you need, water conservation (required by adopted policies) becomes something the city
can do gradually and as circumstances permit; also,you are giving yourself"breathing room"
in case the city experiences more demand for water than the planners are now predicting.
As far as your questions about persons per connection and service area population, the
attachments show basically how these calculations were done. Attachment A shows the
numbers currently used in the plan (the small differences in service area population and
current LOS are due to rounding). Attachment B is a recent revision of the same
calculations, using a seasonal rather than year-round population estimate and reflecting the
10% reduction in LOS, rather than a 15% reduction, by 2000. The figures in Attachment
B are the ones you should use in any engineering calculations you do, and they are the ones
I will use in the plan from now on. Attachment A is for information only.
Persons per connection. For purposes of this calculation, OBWA users were separated
from direct customers of the city system. OBWA reported an average of 2.7 persons
per connection, and this standard was used with no further analysis or modification.
For the city water system, a standard was calculated based on the ratio of in-city
connections to number of city residents having water service. Your office reported
that 70-80% of the city has water service; we assumed that to be 75%.
Attachment B shows a peak population estimate of 4,958. Assuming that 75% of
these people are on city water, the city has 3,719 people using 2,048 connections,
either through residences or commercial uses. This translates to 1.82 persons per
connection.
Population of water service area. Since a population estimate is not available for
unincorporated areas on city water, we assume that the standard of 1.82 persons per
connection also holds true outside the city (except in OBWA areas). There are a
total of 3,864 connections to the city system. At 1.82 persons per connection, this
means a service population of 7,016 for the city system. Added to the OBWA service
population of 8,416, this means a total service population of 15,432.
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A
Using the proper population figure and the water conservation standard that City Council
approved, the city's current service level or consumption rate is 139 g/c/d. The
"Recommended 2000 LOS" shown in Attachment B represents a 10% reduction from the
current use rate and will be adopted into the plan as a minimum level of service standard.
In other words, the city may provide more water than this, but not less. According to
SFWMD, they will allow you to design your plant expansion for the current use rate, rather
than force you to limit your design to accomodate only the adopted LOS.
As I said earlier, there were some minor oversights in developing the numbers that were
used in the current version of the "Infrastructure" Element of the plan. These will be
corrected before the plan is adopted, and you should use the updated numbers in any
analysis you are doing. In reviewing these numbers, please take one more look at the input
data that were used in making the calculations, including average daily flow, peak flow, and
number of connections. If any of these need to be changed, now is the time to let me know.
If you have questions or need further information on anything, please feel free to contact
me.
14:51 t 813 534 7138 CENTRAL FLA RPC
ATTACHMENT A
POTABLE WATER
Avg. Annual Daily Flow (MGD) 2.14
Peak Flow (MGD) 3.00
Peak Factor 1.40
Storage Capacity (MG) 2.00
Storage/ADF 93.5%
Current Est.
Population of City 4,770
Current Est.
Population
Served
(includes OBWA) 15,166
Current LOS (g/c/d) 141
Recommended 1990 LOS (g/c/d) 141
Recommended 1995 LOS (g/cld) 134
Recommended 2000 LOS (g/c/d) 119
Design Capacity
of Facility(MGD) 2.8
Future Design
Capacity1MGDI 4.6
No. of Connections
Res. Comm.
In-City 1,536 512 = 2,048
Out of City 1,576 240 = 1,816
3,112 752 3,864
OBWA 3,117
Service Area Population
Estimated peak pop. of city(1990) 4,770
a/o of city pop. with water service 75%
# of in-city connections 2,048
Persons/connection on city system 1.75
Total connections on city system 3,864
Corvioo Population (oxcluding OPWA) 8.750
OBWA Service Population
@ 2.7 persons/connection 8,416
Total Service Population 15,166
. . • • • `•14:52 d 813 534 7138 CENTRAL FLA RPC• ATTACHMENT S
POTABLE WATER (Revised 3-1-91)
Avg. Annual Daily Flow (MGD) 2.14
Peak Flow (MGD) 3.00
Peak Factor 1.40
Storage Capacity(MG) 2.00
Storage/ADF 93.5%
Current Est. Peak
Population of City 4,958
Current Est.
Population
Served
(includes OBWA) 15,432
Current LOS (g/c/d) 139
Recommended 1990 LOS(g/c/d) 139
Recommended 1995 LOS (g/c/d) 132
Recommended 2000 LOS (g/cld) 125
Design Capacity
of Facility(MGD) 2.8
Future Design
Capacity,(MGDj 4.6
No. of Connections
Res. Comm.
In-City 1,536 512 = 2,048
Out of City 1,576 240 = 1,816
3,112 752 3,864
OBWA 3,117
Service Area Population
Estimated peak pop. of city (1990) 4,958
% of city pop. with water service 75%
# of in-city connections 2,048
Persons/connection on city system 1.82
Total connections on city system 3,864
Service Population (excluding OBWA) 7,016
OBWA Service Population
@ 2.7 persons/connection 8,416
Total Service Population 15,432