LTC 052-2010 Normandy Shores Water Mainsm MIAMIBEACH
OFFICE OF THE CITY MANAGER
LTC # 052-2010 LETTER TO C~~~i'~'I~SI~I~' 36
TO: Mayor Matti Herrera Bower and Members of the City Comm~ssion~' ~"' ~ `~ ~' . ~ Q ~ F f C E
FROM: Jorge M. Gonzalez, City Manager `--'
_= ~
DATE: February 25, 2010 c-:, ~ =`°~~
r ~ ~ '~'~
{~'- ~
SUBJECT: Normandy Shores Water Mains ='= - ,i, F.1
~.
~ri _~
The City was recently asked to take pipe coupons and analyze the need to replace the water q~ins~7~,
in the Normandy Shores neighborhood. This process has been completed, and it-~as"Seen.";
determined that the structural integrity of the existing water mains has not been corri ~ ofi~ed.
Therefore, these water mains do not warrant replacement now or in the near future.
During the first week of February 2010, the City took coupons of the water mains. These coupons
showed that the mains are in relatively intact condition with only minor tuberculation being present in
one of the eight (8) randomly extracted coupons. System pressure recorders also documented that
the water mains in Normandy Shores have more than adequate operational pressures.
These findings correspond directly and are consistent with the previously created Water Main
Priority Maps, which classified these water mains as P3.3, water mains with the lowest Water and
Sewer Bond replacement priority.
Background
The Water Main Priority Maps were developed in 2003 using water system models, non-destructive
field tests, service request logs, and resident complaints. Due to financial constraints which limit the
ability to replace all the water mains, these mains were classified as either Priority 1, Priority 2, or
Priority 3. The replacement of the Priority 1 and Priority 2 mains were funded, and they were re-
classified as CIP mains. The Priority 3 mains were subdivided into P3.1, P3.2, and P3.3 mains.
Water system computer models calculate pressures at nodes and flowrates and pressure losses
through pipe segments under various operating conditions. These scenarios include conditions with
high projected water demands like hypothetical fire fighting operations. These models identify
inadequately sized lines. Subsequent iterations of the model are developed replacing undersized
pipes in order to calculate proper sizes for them. Per the Florida Administrative Code, adequate
minimum system pressure is 20 psi with a recommended working pressure of 35 psi. The current
system operates well above the minimum standard, thus suggesting that the existing pipe is free
from flow constrictions driven by internal corrosion.
The pressures and flowrates developed by the modelling are then calibrated to match observed field
conditions. Tuberculated mains are usually identified at this time when observed pressures are
lower than modelled pressures. Segments in which pressure losses are too great, whether from
tuberculation or inadequate sizing, are then prioritized for replacement.
Soil resistivity tests are also performed. Soils with high resistivity do not conduct currents as well as
soils with low resistivity. Thus, resistivity indirectly measures the corrosiveness of a soil and the
likelihood of corrosion on the exterior of a pipe buried in it. Soil resistivity data are compared with
service requests and complaints to predict if a main is failing due to corrosion.
Normandy Shores Water Main
February 25, 2010
Page 2 of 2
Typically, pipe coupons are taken when modelled data do not match field data and when there is a
large number of resident complaints. Resident complaints of odors, taste, and coloration, are an
indication of internal corrossion, and there is no record of this type of complaint. However, coupons
are not routinely taken as part of a water system analysis because it is a destructive test. The more
frequently coupons are taken, the more system structural integrity is lost.
Analysis
As previously noted, the condition of the Normandy Shores water mains is consistent with the Water
Main Priority Maps. System pressure recorders were installed at four locations on Normandy Shores
on December 12, 2009. These locations were 1175 North Shore Drive, 565 Fairway Drive, 163
North Shore Drive, and 600 South Shore Drive. These recorders show pressures well above
industry accepted standards. Over the course of the day, system pressures varied from a high of just
around 70 psi to a low of over 40 psi. (Please see Attachment A: Map of the Pressure Recorder
Locations and Attachment B: Chart of the Pressure Recordings.) These low pressures occur
between 1:00 am and 6:00 am when the golf course was using a high volume of water for irrigation
and the City water storage tanks are being refilled. During the typical period of high resident demand
in the early morning and evening, system pressures are high. Based upon these data, the water
system at Normandy Shores is continuously operating above the minimum recommended pressure
of 35 psi even during periods of golf course irrigation.
During the first week of February 2010, the City exposed eight (8) sections of the Normandy Shores
water mains and took coupons. These locations were 300, 620, and 940 South Shore Drive; 535
and 875 Fairway Drive; 227, 645, and 1015 North Shore Drive (please see Attachment C: Map of
Coupon Locations and Attachment D: Photos of the Coupons). Seven (7) of the eight (8) randomly
extracted coupons are perfectly clean with no tuberculation. One (1) coupon has minor
tuberculation. The cross section of the coupon shows that the wall thickness is perfect with no
external or internal corrosion that would compromise the water main structural integrity. As a result,
there is no indication that the functionality of the pipes has significantly deteriorated as a result of
age and exposure.
Conclusion
At this point in time, pursuant to all technical analysis and field investigations, the City Administration
cannot recommend replacement of the Normandy Shores water mains. System pressure data,
system modelling, and coupons all indicate that the water mains are functioning and will continue to
function well above minimum standards.
The cost to replace all the unfunded P3.3 water mains throughout the City would be substantial.
There are approximately 17,300 feet of water mains within Normandy Shores and an additional
25,000 feet of unfunded P3.3 mains in neighborhoods not currently in construction. These
neighborhoods include Biscayne Point, North Shore, La Gorce, Flamingo,West Avenue, and Palm
and Hibiscus Islands. Therefore, approximately 42,300 linear feet of P3.3 would have to be added to
the Neighborhood Improvement Program. Based upon recent City projects, the estimated cost for
construction, permits, design, and management to add all these P3.3 mains, would be over
$10,000,000. Funding would have to come from the future water and sewer bonds since this work is
not otherwise funded. It should be noted that an increase in the bond issuance correlates with an
increase in the water and sewer rates.
Attachments:
A. Map of the Pressure Recorder Locations
B. Chart of the Pressure Recordings
C. Map of Coupon Locations
D. Photos of the Coupons
JGG/FH~V
F:\work\$ALL\(1) EMPLOYEE FOLDERS\Rick Saltrick\LTC for Normandy Shores WM.doc
,~O
~~~. pp
~ ~O
Q O
O.
7~ p• pp
O.
7~~ pp
~ ~O
O
~ ~~p
s p
~ p°o
ss o
o.
Q'°o
°op
'~ ~°o
'moo.
7p, • pp
~o ~°o
'°o.
cos °o
~,. °op
'moo.
~~~•pp
O.
c~~~• pp
O.
D~~pO
O.
~~~p0
O.
~~, p0
O.
?Q~pO
O.
c~?~' pp
O.
~~~p0
OD
O
O.
6'~' pp
O~
6'. O
~O
.Q O
O.
~~' pp
O.
~~~p0
O.
7p,. pp
~~~ p0
j~iS p0
OD
O
0
3
d
c.
O
cD
N
d
cD
'G
N
cD
N
N
C
N
D
v
n
m
W
N w ~ cn rn ~ o
0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
D
~«
3
7
D
~t
,-.
v
m
.5
-;~E
~~ ~i
~~~~~
.,
~~
~.
0
0
c
S
O
1
s1+g;F
tip,
~~~
~.'
r
~_
~_.
-. s..~ ~ ~
.,. ~, w
~, rv Y
~ ~ ~ ' ,'s
,. ~~
r ~ ~~
n ~ T
~' ~~ ~ !~~. ~'a ~ ..;~ ~x 'Cix. ~ ~~ v~
.~. _, ~~ ~ ~
Y
"
~~'' h f
~~ T ~~~',
r .
2
t
ltd
s
by ~ ~ ~ ~ .~ i
} ,
f
I
x
L
M
~1\
~
~
vs 4
.~
V
.='~g~
_....
.~ ~ N
~
1 cA
~.,
~~t
a I
~~"~~
`~ If I I
~ ,4
~.~
~
~~~.
a ~.
,,
e
~~~~ ~ ' ~
~ ~
~
~ ~.
~ `"~
J~fkY
~ ~'. v
r,
~
~ ;. ~
,_
_z ^"
~
a
~ ~~~~yy
"C~ i
~tl~4 y
k ~
~~
=
,~,
` ~
~~ ~ ~ ~
u ~w „
~
~ ~, ,,
~: ~~ ~ ~.?
~,
~,
~.;;~
~~ ~g~ ~
~`
Y
gym.. ~ ~~ ~
P f ce
~ a #
~ _ *
'
~
;.
~ , ~ u
*~
~ , ~`
~
~ _ ~ ~,
a"~
N
N
v
Z
0
0
c~
~~~ ~.,
°"
~~,
,~ ~' ' ~ ,
` $r
~.m:;:,:
~ w~
~a.s
~^-~a_^.,_ .
~~~
a
~. a~-
`
~ ,
° .
~ ~~ ~
~ '
~~ ~ ~
Y
t
~ P t
4
y~
~ W
y
N
w-
+w- ~
~rv ~
o
gib ~ `~ ~ ~
~~~~ ~ ~ +~ t
s €
i' ~ V ~' R ~
1Ma ~
'
~ ~~ ~
i. ~ ~ ~
~
:.
~
~ r ~
~
`~ ~
_~
3 ~. -
s. 7' µ
~
4 ~'
'~ ^_}
Z
Q
/~
VJ
Q
~,,,;'
k
~~ ..
$` ~ ffi
i
t
~
t ?
~~~ v ~.,
~LL
~; 4
;_ ~nT:
;~
~~'
~:
~~
,,~~~ _
~,
~y~
. ,T a ~.,
._ ~ - ., ~,
-. e,
,~ _ ~,
a~
~ ~ Y
~ i X`
ruj ?
k u. ~ r : ,.
~ ~ ~
* a~.
3= : `"_ ..
t ~ .'b
e`
3 ~ q•i
~~
_'_~ , ~ ~,
~~
~~
s ~ ~~ ~
1 ~ ~~ ~ ~~;~~~s
~ _ ~~ .
_:~, ~ ,
,,
a.,
> ^'rv~