HomeMy WebLinkAboutIV(B)2a Status Report on Forest Oaks Water Well Maim 07/05/88
ITEM Imo. IVB.2(a)
THOMAS R. ISON TELEPHONE(407) 656-2322 Ocoee
AMAYOR•COMMISSIONER # G
CITY OF OCOEE
v •• O
COMMISSIONERS 150 N.LAKESHORE DRIVE
RUSTY JOHNSON OCOEE,FLORIDA 32761 ' 0000
LESTER DABBS,JR.
JOHN BATEMAN
VARD J. HAGERmbe
2001
aQ ) s�
CITY MANAGER OCOEE
TEDDY C. RYAN,JR. ABICENTENNIALCOMMUNITY
STAFF REPORT
TO: THE HONORABLE MAYOR AND BOARD OF CITY COMMISSIONERS
FROM: JOHN COCKRELL, WATER DEPARTMENT SUPERVISOR
DATE: JUNE 30, 1988
SUBJECT: FOREST OAKS WELL # 1/M-003
ISSUE
What action should the Ocoee City Commission take regarding the defective condition
of Well #1 at the Forest Oaks Water Treatment Plant?
BACKGROUND
On June 17, 1986 the Ocoee City Commission accepted the Forest Oaks Water Treatment
Plant. The capacity of this plant was to be 2450 gallons per minute (GPM) provided
by two wells. This capacity was to have provided service for 1749 single-family
residences. Performance of the plant was secured by a two-year bond posted by the
Developer which expires August 5, 1988.
DISCUSSION
Although Well #2 (the west well) has met its design criteria, Well #1 (the east
well) has not. In reviewing the file on this particular well, I found various
letters, reports, and memoranda which indicate that the design pumping rate of the
well should be between 1100 and 1200 GPM. I have also seen documentation in the
file attesting to the well's ability to produce that flow. However, subsequent
to a discovery by City Staff that the well was not producing its designed rate,
the City Commission authorized Ardaman & Associates to conduct an investigation
to determine the true capacity of the well.
Subsequently, Ardaman conducted the necessary test and has determined that the
sustained pumping rate of the well should not exceed 700 GPM. A copy of Ardaman's
report dated May 16, 1988 in which this conclusion was discussed was then
transmitted to the Developer, Mr. A. Wayne Rich, by our letter dated May 23, 1988.
In response to that letter, Mr. Rich apparently authorized Michael D. Sims &
Associates to review Ardaman's report and to make appropriate recommendations.
"CENTER OF GOOD LIVING—THE PRIDE OF WEST ORANGE"
In his report dated June 14, 1988, Mr. Sims concludes that the well is capable of
producing at least 1000 GPM even with the restriction posed by the 7" casing (the
well was originally designed to be a 10" well) although it cannot achieve this rate
without restoration of the well bore to its originally-drilled depth including an
additional 50 feet to allow for future caving or sloughing.
RECOrMRENDATION
It is respectfully recommended that the Honorable Mayor and Board of City
Commissioners approve the following action:
1. That the City of Ocoee provide formal notice to the Developer, the surety
for the bond, the well's design engineer, the City's consulting engineer that
provided services to the City for this particular project, and the contractor that
this well is defective and that a demand be made on all of these parties for actions
necessary to correct these defects. This demand must be made prior to the
expiration of the bond on August 5.
2. That the Developer be allowed to undertake the restorative effort
recommended by Mr. Sims entirely at the Developer's cost. We should note that the
Staff is not convinced that this restorative effort will effect a permanent solution
to the problems but feel that the Developer should be given this opportunity. Such
permission should be given with the expressed stipulation that by granting the
Developer this opportunity, the City is not releasing any of its rights to obtain
a permanent solution to the capacity problem which would be consistent with sound
engineering practice. Furthermore, the City's approval must be given with the
additional stipulations that the Developer must accomplish this work within a time
period agreed upon by the City and that such approval will not prejudice our
recovery rights under the terms of the bond and the Developer's Agreement.
DLF/jgr
cc: Teddy C. Ryan, Jr. , City Manager
Dennis L. Finch, Assistant City Manager
William F. Lichtler, Ardaman & Associates
Todd L. Johnson, Hartford Insurance Co. (Surety)
A. Wayne Rich, Amick Construction Co. (Developer)
William Goodman, Residential Communities of America (Developer)
Michael D. Sims & Associates
Walter Kuhrt, Jr. , P.E. , Kuhrt & Associates, Inc. (Design Engineer)
Stephen R. Miller, P.E. , Miller, Miller, Sellen, and Einhouse, Inc. (Consulting
Engineer)
Meredith Corporation (Contractor)
R. Duke Woodson, City Attorney
Ardaman &Associates, Inc.
111.0%4.
June 29, 1988
File Number 87-082
Consultants in Soils, :-vcrocecicay,
Foundations and Mater als Testing
City of Ocoee
150 Lakeshore Drive
Ocoee, Florida 32761
Attention: Mr. John Cockrell, Ocoee Water Superintendent
Subject: Report - Forest Oaks Water Well No. 1, Evaluation and
Recommendation by Michael D. Sims & Associates, Inc.
Gentlemen:
As requested by Mr. John Cockrell, Mr. William F. Lichtler has reviewed the
subject report. We have several specific comments and an overall comment on
the conclusions and recommendations.
1. The caliper log performed on May 11, 1988 shows the top of the 7-inch
casing at 121 feet which is the maximum depth at which the intake of
the existing pump could be set. Measurement of the pump column by
Layne-Atlantic during the pump test on May 9, 1988 (120.3 feet)
indicate that the foot valve was within about a foot of the top of the
7-inch liner casing.
2. The geophysical logs indicate that the open hole part of the well
extends from 609 feet to 1142 feet for a total open hole length of 533
feet. The driller's log shows the original open hole depth after the well
was completed on 6/12/85 to be from 609 to 1168 feet for a total open
hole length of 559 feet.' As the driller's log generally is the original
source of data on well construction unless geophysical logs are run at
the time the well is completed, this indicates that there is 26 feet of
fill in the bottom of the well. Dividing 26 by the original open hole
length of 559 feet indicates that only 4.65 percent of the producing part
of the well has been filled in.
3. Examination of the geophysical logs does not reveal any data that would
accurately determine the distribution of major producing zones where
water enters the well bore during pumping. The most likely looking
zones on the caliper log are between 840 and 846 feet where a cavity at
least 34.5 inches in diameter was encountered and between 609 and 700
feet where numerous small cavities are present. A horizontally
extensive 34-inch cavity is capable of yielding a large quantity of
water. The log does not show significant cavities between 1000 feet
and 1142 feet except a 10-inch diameter cavity at 1135 feet. The other
geophysical logs do not indicate zones of potential major inflow to the
well nor does the driller's log. In our opinion, the most practical way to
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City of Ocoee
File Number 87-082 -2-
determine the pattern of inflow of water to the well bore during
pumping is to conduct a current meter survey during pumping.
4. We believe that a roughness coefficient (lower numbers indicate greater
roughness) of c=130 (new pipe) is too high a number when calculating
the friction loss in the 7-inch diameter pipe. The 7-inch casing is at
least 3 years old and judging by the condition of the pump column that
was in the well and presumably was new when installed in 1984 a
coefficient of c=120 (5 years old) to c=110 (10 years old) is more
likely. These coefficients indicate 14 to 16 feet of drawdown,
respectively. Using a mid value of 15 feet leaves only about 3±1 feet of
drawdown attributable to drawdown in the aquifer and friction loss in
the open hole part of the well which is only 6 inches in diameter at
some depths. As stated in Ardaman & Associates, Inc. report to the
City of Ocoee dated May 25, 1988, the roughness coefficient of the
7-inch diameter casing and consequently the drawdown in the well can
be expected to increase with time. We believe that most of the
drawdown measured during the pumping test on May 9, 1988 was due to
friction loss in the well. Some drawdown in the aquifer must take place
to move water to the well, however, we believe that this factor is
minior in Well No. 1.
5. We can make no definitive statements as to the accuracy of the
measurements of either discharge or drawdown during the June 11, 1985
pumping test. However, an increase of more than 50 percent (9 feet to
14 feet) in drawdown when the pumping rate was increased 10 percent
(1000 to 1100 gpm) is not the usual aquifer response during a pumping
test.
Our general comments are: i) that using a roughness coefficient of c=130 to
calculate friction loss in the 7-inch diameter casing liner is unrealistic; (ii) there
is no definitive data in the geophysical logs to indicate that the major producing
zone of the well is near the bottom-of the well (1000 to 1142 feet); (iii) estimating
the error in measurement during the June 11, 1985 pumping test at 15 to 20
percent is speculative; and (iv) we are not optimistic that removing the 26 feet of
fill in the bottom of the well and deepening it another 50 feet will significantly •
increase the specific capacity of the well.
If we can be of further assistance or if you have any questions, please contact us.
Very truly yours,
ARDAMAN & ASSOCIATES, INC.
4,z)e,/:/eel:>p)/o . `7et -rLitlx
William F. Lichtler
Senior Hydrogeologist
WFL:ed
Ardaman&Associates,arc.
Ardaman & Associates, Inc.
/MA
May 16, 1988
Consultants in Soils, Hydrogeology, File Number 87-082
Foundations and Materials Testing
City of Ocoee
150 Lakeshore Drive
Ocoee, Florida 32761
Attention: Mr. John Cockrell
•
Subject: Pumping Test Conducted by Layne Atlantic Company on Well
No. 1 (East Well) at Forest Oaks Wellfield
Gentlemen:
As requested by Mr. John Cockrell, Mr. William Lichtler oversaw the pumping test
conducted by Layne Atlantic Company on Well No. 1 (east well) at the Forest
Oaks Wellfield.
The original schedule was for Layne to set the pump on May 4, 1988 and conduct a
preliminary test with a longer test if needed on May 5, 1988. Problems arose with
inserting the pump bowls in the well on May 4, 1988. The bowls were modified and
the pump was emplaced in the well on May 5, 1988. Further problems arose in
connecting the 6-inch discharge line to the 8-inch orifice pipe, but on May 6, 1988,
a preliminary run was performed to test the equipment. Present were: Mr. John
Cockrell, Ocoee Water Superintendent; Messrs. Walter Wood and Douglas Hern,
MIchael D. Sims & Associates; Mr. Ned De Marce, Berry Goodman, Inc.;
Mr. William Lichtler, Ardaman & Associates, Inc.; and a three-man crew from
Layne Atlantic Company.
The static water level in the well was measured by steel tape using the wetted
tape technique at 71.79 feet below the top -of the 10-inch diameter casing at
11:25. The water level, as measured using the airline installed in the well, was
within 0.2 feet of that measured with the steel tape.
The orifice used to measure discharge of the well was a 6-inch knife edge plate in
an 8-inch pipe. The Layne orifice tables used to calculate discharge in relation to
the manometer readings are calculated using a knife edge orifice plate. The
manometer opening is located 33 inches from the orifice plate rather than the 24 •
inches as indicated in the book; however, Layne personnel on the job said that they
have used this setup for many years and it has been calibrated within 2 percent
against calibrated flow meters.
The static water level in the well at 12:50 was 71.85 feet below the top of the
casing. Well No. 2 had not been pumping for more than 20 hours. The pump test
• was started at 13:25; however, at 13:27 the coupling above the pump bowls broke
and the test was postponed until May 9, 1988.
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City of Ocoee
File Number 87-082 -2-
On May 9, 1988 the water level in the well, as measured by steel tape, was 73.19
feet below the new measuring point at the airline access hole (one foot above the
top of the casing) at 14:37 hours.
The water level in the well, as indicated by the airline gage reading, corresponded
to the steel tape reading within 0.2 feet and had remained steady for more than
one hour. The reading showed that the bottom end of the airline was 28.5 to 29
feet below the static water level. The length of the airline was reported by Layne
as 103.6 feet below the access hole placing the end at 30.4 feet below the water
surface.
Present at the test were: Mr. John Cockrell, Ocoee Water Superintendent;
Mr. Walter Wood, Michael D. Sims ac Associates; Mr. WIlliam Lichtler, Ardaman &
Associates, Inc.; and a three-man crew from Layne Atlantic Company.
The test was started at 14:38 and the pumping rate was steadily increased toward
the goal of 1100 gallons per minute (gpm).
As the pumping rate reached approximately 950 to 975 gpm, as indicated by the
manometer-discharge rating curve, the airline readings on the gage reached the
bottom peg on the gage indicating that the water level was below the bottom end
of the airline and drawdown in the well was greater than 28.5 to 29 feet. At this
time (14:45) the Layne crew chief (Gary) shut down the engine to avoid the
possibility of drawing the water level below the pump bowls as the airline gage
could no longer show the water level. The end of the airline was reported to be
approximately 7 feet above the pump bowls. A conference was held and it was
agreed upon by all present that the well could not be pumped at 1100 gpm,
therefore, It was decided to pump the well at approximately 800 gpm which
corresponds to a manometer reading of about 26 inches.
The airline reading at a pumping rate of 800 gpm produced an airline reading of 10
feet which corresponds to a drawdown of 18 to 19 feet (specific capacity of 43
gpm per foot of drawdown). The reading stabilized within approximately 5
minutes and remained at that level for 15 minutes. The switch on the engine
malfunctioned several times and shut down the engine; however, each time the
water level returned to the static level within 5 minutes and stabilized at 18 to 19
feet of drawdown at 800 gpm 15 minutes after the test was restarted.
Detailed readings of pumping rates and drawdowns were taken by the Layne crew
and will be forwarded when available.
The two major causes of drawdown in a well are: (1) lowered water levels in the
aquifer which are necessary to create a gradient and cause the water to move to
the well and (2) friction loss within the well casing and open hole part of the well
as the water moves up to the pump intake. The aquifer drawdown Is a function of
the transmissibility and storage coefficient of the aquifer and leakance. The
drawdown due to friction loss is a function of the type, diameter and length of the
casing, the diameter and roughness of the open hole and the location of the zones
contributing water to the well.
• City of Ocoee
File Number 87-082 -3-
The aquifer transmissibility varies greatly from well to well depending on the
number and size of water bearing cavities penetrated by the well. The drillers log
for the open hole part of the well from 609 feet to 1168 feet does not mention
cavities penetrated; however, the log lists hard light brown limerock and dolomite
between 970 and 1168 feet and this type of formation often contains cavities that
yield large quantities of water.
The well is constructed, according to the drillers log, with a 7-inch liner from 125
feet to 609 feet (confirmed by geophysical logging from 121 to 609 feet) in the
10-inch well. Calculations based on 500 feet of casing with the generally
accepted roughness value of C=100 for old pipe, 800 gpm and a casing size of
7-Inch diameter, indicate a head loss of approximately 19 feet (see graph).
The calculations indicate that most of the drawdown in the well is due to friction
loss in the 7-inch diameter casing liner in the well with little loss due to open bore
friction or aquifer drawdown. The rapid stabilization of drawdown levels and the
rapid recovery support this conclusion.
We believe that the maximum withdrawal rate from this well with Its present
construction should not exceed 800 gpm as the pump cannot be set lower due to
the 7-inch casing at 121 feet.
Water levels with long-term production pumping at 800 gpm would probably be
lower than 19 feet below current static levels due to likely increased drawdown
with long-term pumping, interference from Well No. 2, natural decline in regional
water levels and interference from nearby wells, therefore, it is recommended
that the permanent pump be designed to produce water at a rate of approximately
700 gpm.
If you have any questions, please do not hesitate to contact us.
Very truly yours,
ARDAMAN ec ASSOCIATES, INC.
iirf/,,ez.ze. 40e:01
William F. Lichtler
Senior H dro ologist
Herbert G. Stangland, Jr., .E.
Senior Water Resources E ineer
Florida Registration No. 16713
WFL:cc
EXPLANATION
250—
FLOW=800 GPM
ROUGHNESS VALUE-C = 100
LENGTH OF PIPE = 500 FEET
DIAMETER OF PIPE a 7 INCHES
_ HEAD LOSS - 19 FT. t
• DATA POINT FROM WILLIAMS & HAZEN TABLE
A CALCULATED USING FORMULA
W
U.
FORMULA
0150—
H=4.727L r O 1 1.85
WD4.87 L C J
=
H.19 FT.
H=HEAD LOSS (FEET)
100—
OFLOW (CFS)
C=ROUGHNESS
D=DIAMETER OF PIPE (FEET)
L=LENGTH OF PIPE (FEET)
50—
r
0—
I
4 6 6 7 8 9 10 12 14 18
DIAMETER OF PIPE IN INCHES
HEAD LOSS THRU 500 FT. OF PIPE
Nor Ardaman& Associates,Inc. ,
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F.nnbtinni,n id N4twiE TStinI
CITY OF OCOEE
SOURCE: WILLIAMS & HAZEN 1933 HYDRAULIC TABLES
JOHN WILEY& SONS "AAMNEY. SEF ICNECREOEr IDATE: 5/9/88
F87-ae2gENO. APPROVED/2.
S 4464
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