HomeMy WebLinkAboutItem III (C) Acceptance and Authorization for Mayor and City Clerk to Execute Addendum to Perform Groundwater Modeling of Land Application of Treated Wastewater at the City's Effluent Disposal Site/Golf Course with LJ Nodarse & Associates, Inc. }
/ AGENDA 1-4-94
Item III C
"CENTE j F GOOD LIVING-PRIDE OF WEST ORANGE"
OCOo@ S.SCOTT VANDERGRIFT
6i. 1 COMMISSIONERS
.0-1.44 f ° CITY OF OCOEE RUSTY JOHNSON
' M O. 150 N.LAI�SHORE DRIVE PAUL W.FOSTER
v D OCOEE FLORIDA 34761-2258 VERN COMBS
�+�. ?V
(407)656 2322 JIM GLEASON
yfE� Op G0OD N> CITY
r-' ELL S MANAGER
SFiAPIRO
TO: The Honorable Mayor and Board of City Commissioners
FROM: Montye Beamer, Director (1 j
Administrative Services U � �
Date: December 29, 1993
RE: ADDENDUM TO PERFORM GROUNDWATER MODELING OF LAND
APPLICATION OF TREATED WASTEWATER AT THE CITY' S EFFLUENT
DISPOSAL SITE/GOLF COURSE
As indicated at the December 7 , 1993 Commission meeting, the first
task for the geotechnical consultants would be to perform the
groundwater modeling required by the Florida Department of
Environment Protection (FDEP) for the treated wastewater at the
City' s effluent disposal site/golf course . The three geotechnical
consultants responded; their proposals are attached. On December
22 , 1993 these proposals were reviewed by the City Engineer and the
City' s consulting engineer . The selection criteria included: ( 1 )
scope of services , ( 2 ) schedule , and ( 3 ) proposed fee . Ken Hooper
summarized the findings . His letter is also attached.
It is staff ' s recommendation to award Addendum 1 to L . J . Nodarse
& Associates , Inc . in the amount of $14 ,760 . 00 with 196 hours for
completion. This recommendation is due to the understanding
exhibited in their proposal as to what will be necessary to satisfy
FDEP in the required time frame; its detail demonstrates that it
will also be the most cost-effective .
ACTION REQUESTED
The Mayor and City Commissioners ( 1 ) award Addendum 1 to L .J .
Nodarse & Associates , Inc . in the amount of $14, 760 . 00 with 196
hours for completion and ( 2 ) authorize the Mayor and City Clerk to
execute .
PEC
PROFESSIONAL ENGINEERING CONSULTANTS, INC.
December 28, 1993 P-3178
Mr. James W. Shira, P.E.
City Engineer/Utilities Director
City of Ocoee
150 North Lakeshore Drive
Ocoee, Florida 34761
Re: Proposal to Perform Groundwater Modeling of
Land Application of Treated Wastewater at the
City's Effluent Disposal Site/Golf Course
Dear Mr. Shira:
As requested, I have reviewed the proposals from the City's three (3) geotechnical
consultants, Universal Engineering Sciences (UES),Professional Service Industries, Inc.
(PSI), and L.J. Nodarse and Associates, Inc. (UN). Listed below are comments
concerning the scope of services, schedule and proposed fee.
SCOPE OF SERVICES
All three geotechnical firms identified an acceptable scope of services to perform the
groundwater modeling as requested in the City's Request for Proposals (RFP). All
firms proposed to use the MODFLOW simulation model, including calibration and
coordination with FDEP staff. The UN scope demonstrated an exceptional awareness
of existing groundwater conditions, including a detailed description of the interaction
of the depressional lakes (sinks) and the breaches in the semiconfining layers above the
aquifer. UN also described their extensive experience with the MODFLOW model and
its uses.
Summary
The scope of services as described by UN is exceptional in detail and demonstrates a
very good knowledge of the existing conditions.
SCHEDULE
The City has committed to FDEP to complete the groundwater modeling and provide
the results by March 31, 1994. Assuming a notice to proceed can be issued on January
5, 1994, the schedule requires for completion of this assignment no later than 12 weeks.
engineers
planners
surveyors 200 East Robinson Street • Suite 1560 • Orlando, Florida 32801 • 407/422-8062 • FAX 407/849-9401
Mr. James Shim
December 28, 1993
Page 2
The schedules as identified in each proposal are as follows:
UES - 12 weeks
PSI - 12 weeks
UN - 7-9 weeks
Summary
Based on the proposals, all firms indicated the groundwater modeling could be
completed within the mandated timeframe.
PROPOSAL FEE
Each firm identified a proposed fee to complete the assignment.
UES - $18,860.00 - 284 hours
PSI - $13,800.00 - 201 hours (indicated a range of $12,000 to $15,000
depending on FDEP's response)
UN - $14,760.00 - 196 hours
RECOMMENDATION
Based on the scope of services as provided by the consultant, schedule and proposed
fee, I recommend the City of Ocoee use the consulting firm of L.J. Nodarse and
Associates, Inc. to complete the assignment concerning the modeling of the groundwater
at the City Effluent Disposal Site/Golf Course. The defined scope of services should
provide the most cost-effective groundwater analysis and meet the City's schedule for
compliance with FDEP permit conditions.
Very truly yours,
PROFESSIONAL ENGINEERING CONSULTANTS, INC.
9'' '?Vcite.-----._
K nneth R. Hooper
KRH/kh
cc: Montye Beamer
ADDENDUM TO CONTRACT
FOR PROFESSIONAL GEOTECHNICAL ENGINEERING
AND TESTING SERVICES
ADDENDUM NO. 1
PROJECT: GROUNDWATER MODELING OF LAND
APPLICATION OF TREATED WASTEWATER AT THE
CITY'S EFFLUENT DISPOSAL SITE/GOLF COURSE
CITY: OCOEE, FL
GEOTECHNICAL ENGINEER: L. J . NODARSE & ASSOCIATES , INC .
Execution of the Addendum by City shall serve as
authorization of GEOTECHNICAL ENGINEER to provide for the above
project , professional services as set out in the documents which
are attached hereto and made a part hereof .
ATTACHMENTS:
[X] Technical & Fee Proposal , Groundwater Modeling
of Land Application of Treated Wastewater dated
December 15 , 1993
GEOTECHNICAL ENGINEER shall provide said services pursuant to
this Addendum, its attachment and that certain Agreement of January
1994 , between CITY and GEOTECHNICAL ENGINEER which is
incorporated herein by reference as if it had been set out in its
entirety. Whenever the Addendum conflicts with said Agreement , the
Agreement shall prevail .
TIME FOR COMPLETION: The work authorized by this Addendum
shall be completed within one hundred and ninety-six ( 196 ) hours
from the date this Addendum is executed by the CITY.
COMPENSATION: The CITY shall compensate Geotechnical Engineer
a negotiated fixed fee in the amount of FOURTEEN THOUSAND SEVEN
HUNDRED AND SIXTY DOLLARS ( $14 , 760 . 00 ) for the service required
under this Addendum. GEOTECHNICAL ENGINEER shall perform all work
required by this Addendum; but , in no event , shall GEOTECHNICAL
ENGINEER be paid more than the fixed fee set forth above .
IN WITNESS WHEREOF, the parties hereto have made and executed
this Addendum on this _th day of January, 1994 , for the purposes
stated herein.
By:
Its :
(CORPORATE SEAL )
APPROVED:
ATTEST: CITY OF OCOEE, FLORIDA
Jean Grafton, City Clerk S . Scott Vandergrift , Mayor
( SEAL )
FOR USE AND RELIANCE ONLY BY APPROVED BY THE OCOEE CITY
THE CITY OF OCOEE, FLORIDA COMMISSION AT A MEETING
APPROVED AS TO FORM AND LEGALITY HELD ON , 1994
this _ day of January, 1994 . UNDER AGENDA ITEM NO.
FOLEY & LARDNER
By:
City Attorney
Geotechnical,
Environmental
& Materials
Engineers
December 15, 1993
Project No. 93-0597
LI Nodarse
TO: CITY OF OCOEE &Associates,Inc.
150 N. Lakeshore Drive
Ocoee, Florida 34761
ATTN: Mr. James W. Shira, P.E.
City Engineer/Utilities Director
RE: Technical & Fee Proposal, Groundwater Modeling of
Land Application of Treated Wastewater
Ocoee Public Golf Links Facility
City of Ocoee, Florida
Dear Mr. Shira:
At your request, we are pleased to present this technical and fee proposal to perform the
above-referenced services. This proposal describes our technical approach, the estimated
professional time requirements, associated costs and schedule for completion of the work.
In summary, we propose using the transient MODFLOW simulation to predict the
percolative capacity of the site. The analysis will be performed in accordance with
modeling protocol that is consistent with FDEP requirements. The estimated time to
complete the modeling study and deliver the final report is 7 to 9 weeks from your
authorization to proceed. We understand that a March 31, 1994 deadline has been
established by FDEP and we will meet this deadline. Our estimated fee to complete this
work is $14,760.00. An itemization of this fee is presented in the proposal.
We trust that this proposal is in order and we look forward to assisting the city on this
project. Please do not hesitate to contact us if there are any questions.
Sincerely,
L.J. Nodarse & Associates, Inc.
DR 3 ( L.J.---3"e
Devo Seereeram, Ph.D. David B. Twedell
Hydrogeotechnology Consultant Senior Environmental Consultant
'Le' ; I. in al Nodarse, P.E.
• ;e. len
11
807 South Orlando Avenue♦Suite A♦Winter Park, Florida 32789♦Telephone 407.740.6110♦Facsimile 407.740.6112
TABLE OF CONTENTS
1.0 INTRODUCTION 1
2.0 TECHNICAL APPROACH 1
2.1 General 1
2.2 Methodology 2
2.3 Conceptual Model 3
2.4 Model Design 7
2.5 Calibration . . . .. . . . . . . . . . . . . . . . . . . . 10
2.6 Sensitivity Analysis 10
2.7 Model Verification 10
2.8 Prediction . . . . . . . . . . . . . _ _ 11
2.9 Field Audit Recommendations . . . 11
2.10 Water Balance & Nutrient Balance 11
2.11 Final Report 11
3.0 SCHEDULE 11
4.0 ESTIMATED COST 12
1.0 INTRODUCTION
The 240-acre Ocoee Golf Course site is a combination rapid rate/slow rate reclaimed
wastewater land application scheme. Slow-rate irrigation of the 18-hole golf course is
combined with rapid rate disposal via two on-site percolation ponds. This proposal
focuses on the technical approach for modeling and predicting the ultimate disposal
capacity of the site. The City of Ocoee has been requested by the Florida Department
of Environmental Protection (FDEP) to perform such an analysis to satisfy the
requirements for a mounding analysis as per Chapter 17-610("Reuse of Reclaimed Water
and Land Application")of the Florida Administrative Code(F.A.C.). The City of Ocoee
has committed to deliver a report on this study to the FDEP by March 31, 1994.
In addition to a discussion of technical aspects of the assignment, this proposal is divided
into 3 sections:
• Technical Approach.
• Schedule For Execution of Work
• Professional Fees
2.0 TECHNICAL APPROACH
2.1 General
There are many appropriate numerical models and approaches to applying these models
to predict the disposal capacity of a wastewater land application facility. In general, the
choice of a methodology and its approach is influenced by several factors, including:
• the hydrogeologic setting of the site,
• the complexity of the areal distribution of artificial recharge within the
site,
• the magnitude of the artificial recharge rate (i.e., slow-rate or rapid-rate),
• the various mechanisms of disposal (i.e., evapotranspiration, lateral
seepage, vertical leakage, etc.)
• the field data available, and
• the guidance of the regulatory agencies.
The methodology and approach described hereunder applies specifically to the Ocoee
Golf Course site and is tailored to address the needs of the Florida Department of
Environmental Protection.
•
Project No. 93-0597
Page 2
2.2. Methodology
The ground water flow model chosen for our evaluation is the USGS MODFLOW model
created by McDonald and Harbaugh. Given its widespread use over the past 7 to 8
years, this computer-based methodology is now regarded as the de facto standard for
three-dimensional finite difference modeling of effluent disposal facilities in Florida.
The steps in a typical MODFLOW modeling protocol include:
1. Develop a conceptual model of the system: Hydrogeologic units and
system boundaries are identified. Field data are assembled
including data needed to assign values to aquifer parameters and
hydrologic stresses.
2. Model design: The conceptual model is put into a form suitable for
modeling. This step includes design of the grid, selecting time
steps, setting boundary and initial conditions, and preliminary
selection of values for aquifer parameters and hydrologic stresses.
3. Calibration: The purpose of the calibration is to establish that the model
can reproduce field-measured heads. During calibration a set of
values for aquifer parameters and stresses is found that
approximates field-measured heads. Calibration is commonly done
by trial and error adjustment of parameters, although automated
methods are now being introduced into the practice.
4. Calibration sensitivity analysis: The calibrated model is influenced by
uncertainty owing to the inability to define the exact spatial
distribution of parameter values in the problem domain. There is
also uncertainty over defmition of boundary conditions and
stresses. A sensitivity analysis is performed in order to establish
the effect of uncertainty on the calibrated model.
5. Model verification: The purpose of model verification is to establish
greater confidence in the model by using the set of calibrated
parameter values and stresses to reproduce a second set of field
data. If a second set of field data does not exist, model
verification is necessarily skipped.
6. Prediction: quantifies the response of the system to future events. The
model is run with calibrated values for parameters and stresses,
except for those stresses which are expected to change in the
future. Estimates of the future stresses are needed to perform the
simulation.
Project No. 93-0597
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7. Reporting of modeling design and results: clear presentation of model
design and results is essential for effective communication of the
modeling effort.
8. Field Audit: A field audit is conducted as the future stresses modeled in
the prediction simulation are actually approached. New field data
are collected to determinewhether the prediction was correct.
Typically the field audit will lead to new insights into system
behavior which may lead to changes in model parameters and a
more refined prediction.
Each of the above steps, as they relate to the Ocoee Golf Course,are discussed in more
detail below.
2.3 Conceptual Model
A conceptual model is a pictorial representation of the ground water flow system,
frequently developed in the form of a block diagram. The two steps in building a
conceptual model are defining the hydrogeologic units and defining the flow system.
Both of these steps are described below for the Ocoee Golf Course site, followed by a
discussion of the relationship between the conceptual model and the digital model.
2.3.1 Hydrogeology
The hydrogeology at the Ocoee Golf Course may be generalized as follows:
Lithologic Unit Thickness Hydrogeologic Unit
Clean Fine Sand 12 to 50 feet Permeable portion of
surficial aquifer
Cemented fine sand/ 20-30 feet Semi-confining unit
"hardpan" type
1
Hawthorn Clays 75 to 120+ ft thick Semi-confining Hawthorn
Group
Ocala Group Limestone occurs at a depth of 160 to Floridan aquifer
220 ft below land surface
The sixty (60) borings drilled throughout the site disclosed a stratigraphy that is very
consistent within the site. There is an upper mantle of clean fine sand underlain by
dense, much less permeable "hardpan" type soils. The permeability of the clean fine
sands is in the range 40 to 90 ft/day, while the permeability of the hardpan is on the
order of 0.02 ft/day. Since the hardpan is over 1000 times less permeable than the upper
Project No. 93-0597
Page 4
sands, it acts as a semi-confining layer retarding the downward movement of ground
water from the uppermost aquifer.
The top of the hardpan layer is of the same general shape as the land surface
topography. It is generally 12 to 18 feet below land surface in Site #5 and the
interconnecting 30 acre tract, 20 feet below land surface west of the proposed beltway
on Site#8, 30 to 50 feet deep on the eastern boundary of the site, and about 50 feet deep
around the rim of the lakes.
Underlying the hardpan soils are the Hawthorn. Group soils which are comprised of
greenish gray clays with some beds ofsands and thin layers of shell, limestone and
interspersed phosphate grains. The top of the Hawthorn is about 50 feet below land
'surface and extends to a depth of 160 feet to 200 feet below land surface where it
contacts with the Ocala Group limestones of the Floridan aquifer. The top of the
limestone is eroded in this area. The Hawthorn is at least 75 feet thick and is maybe
over 120 feet thick.
According to previous reports, the groundwater table contours generally mimic the
ground surface contours. The pre-development groundwater table is generally 10 to 20
feet below land surface and is generally deepest in the eastern portion of the site. Lakes
#1 and #2 act aspronounced internally drained sinks in the ground water flow regime.
The potentiometric surface of the Floridan aquifer varies seasonally from +58 ft to +63
ft MSL as compared to water levels in Lakes #1 and #2 of +90 and +115 ft MSL
respectively. These elevation differences are evidence that the on-site depressional lakes
are not well connected to the Floridan aquifer. Water movement in the Floridan is to
the north and northeast.
Recharge maps published by St Johns River Water Management District indicate that the
recharge from the surficial aquifer to the Floridan aquifer is 8 to 10 inches per year
within the site.
There are no adjacent surface water bodies with positive outfalls. Lake Sims and Trout
Lake, approximately 1600 feet to the east of the site, are both internally drained but are
better connected to the Floridan aquifer than the on-site depressional lakes. Lake
Apopka, which is poorly connected to the Floridan aquifer, is over a mile to the west
of the site and therefore outside the radius of influence of the hydraulic loading on the
site.
2.3.2 Fate of Recharge Water At The Ocoee Golf Course Site
Before describing the conceptual model, it is important to provide an explanation of the
fate of the recharge water after it infiltrates into the ground. First, it is important to
reiterate that the project site is located within a closed drainage basin. That means that
there are no rivers, creeks, or other surface water bodies which can intercept ground
water and discharge it outside the limits of the basin. Therefore, discharge of ground
water from the surficial aquifer system within the basin is by evapotranspiration and by
Project No. 93-0597
Page 5
vertical leakage to the Floridan aquifer. The latter component is much higher within the
depressional Iakes where the semi-confining Iayers are partially breached.
The portion of the recharge water not consumed by either evaporation or
evapotranspiration will percolate downward below the soil-root zone. Infiltration will
be rapid through the well-drained sand lithology present on-site. The water table will
rise as a result of the increase in recharge. A ground water mound will form in the
uppermost aquifer, inducing lateral flow away from the wetted area. As the ground
water mound spreads beyond the limits of the wetted area, it starts filling the available
soil void space above the preloading water table. The mound continues to spread until_
the lateral hydraulic gradients that develop can dissipate the artificial recharge. At the
radius of influence or lateral extent of the mound, the water table level is close to the
preloading Ievel (i.e., there is little or no mounding effect). Note that a considerable
quantity of water can be stored in the soil voids above the water table especially on the
"high and dry" sand hills which typify the site vicinity.
The increase in head in the uppermost aquifer as a result of the mounding creates
additional downward vertical leakage through the semi-confining unit (i.e.,the hardpan
and Hawthorn clays) to the Floridan aquifer. This vertical leakage rate is, however, not
uniform across the site. It is much greater where the semi-confining layers are breached
such as in the on-site and off-site depressional lakes.
In summary, the ultimate height and lateral extent of the groundwater mound due to the
long-term application of effluent at the land surface depends upon several factors,
including
• the rate at which recharge water arrives at the water table
• the thickness, fillable porosity, and hydraulic conductivity of the
uppermost aquifer,
• ambient groundwater levels in the surficial aquifer,
• the leakage coefficient of the semi-confining unit, inter-aquifer head
difference, and transmissivity of the underlying Floridan aquifer,
• the areal distribution of the effluent application rate, and
• the geometry of the hydraulically loaded area.
2.3.3 Relationship Between Conceptual Model and Numerical Model
Based on the above discussions of the hydrogeologic units and the flow systems, the
numerical model is formulated as follows:
Simulation Type: Transient
Model Type: Full Three-Dimensional
.
•
Project No. 93-0597
Page 6
Model Layers: The model will be set up as a two-layered system:
Layer #1 (unconfined): uppermost zone of clean fine
sand
semi-confining unit (not a model layer)
Layer #2 (leaky confined): the Floridan limestone
aquifer
2.4 Model Design
2.4.1 Model Grid
The rectangular model grid will extend out at least 1000 feet from the edge of the wetted
area. The project site will be centered in the grid. Nodal spacing will be selected during
final design.
2.4.2 Boundary Conditions
Specified head boundaries will be set in the grid cells and located about 1000 feet from
the edge of the wetted area. This setback is considered large enough to prevent the
boundary conditions from influencing the solution. Grid cells beyond this locus will be
inactive while grid cells within the boundary cells will all be active variable head cells.
The locations of the boundary and active cells will be the same in Layers #1 and #2.
The head values in the boundary cells will be set as follows:
Layer #1: annual average water table elevation
Layer #2: annual average potentiometric surface elevation
Since site-specific water table measurements will not be available at the off-site boundary
cells, the water table elevations will be estimated by reviewing the SCS soil map units
and the SJRWMD 1-foot topo of the area. For Layer #2, the specified heads in the
boundary cells will be based on the USGS/SJRWMD Floridan aquifer potentiometric
surface map for a selected normal rainfall year.
In order to prevent artificial recharge stresses from migrating out to the boundary and
causing a simulated effect that is unrealistic, the simulation will be terminated after a
predetermined simulation time. This simulation time, however, will not be less than 2
years or such other simulation time mutually agreed upon with the FDEP.
If a pump station is to be installed in Lake #1, "drain" cells (within Lake #1 in Layer#1)
may be used to model the discharge/recirculation rates and to control the stage elevation.
• •
Project No. 93-0597
Page 7
2.4.3 Initial Conditions
•
Initial conditions refer to the head distribution throughout the system at the beginning of
the simulation. It is standard practice to select as the initial condition, a steady-state head
solution generated by the calibrated model. This initial head distribution represents
dynamic average steady-state conditions where head varies spatially and flow into the
system equals flow out of the system.
2.4.4 Preliminary Selection of Aquifer Parameter Values
The list of aquifer parameters in Table 1 will be required for the conceptual model. _
TABLE 1: AQUIFER PARAMETERS REQUIRED FOR CONCEPTUAL MODEL
LAYER # TYPE . I AQUIFER PARAMETERS
1 Unconfined or a. Hydraulic conductivity
upper clean sand Water table b. Fillable porosity
c. Base elevation of aquifer
not a model layer Semi-confining unit . a. Vertical leakage coefficient
2 a. Transinissivity
Floridan aquifer Leaky confined b. Storage coefficient
There is considerable site-specific data on the hydraulic conductivity and base elevation
of Layer #1. Kriging will be used to interpolate the base elevation of Layer#1 between
the boring locations and areas of the model domain outside the site limits. There is much
less uncertainty associated with estimating the fillable porosity of Layer #1. Values of
fillable porosity of these fine sands are generally in the range 25% to 30%.
Estimates of the Floridan aquifer parameters will be obtained from published data and
any information available from the Water Management District and the FDEP.
The vertical leakage coefficient will vary within the model domain. For example, it will
be much higher in the depressional lakes. This parameter will be refined during the
calibration, but the leakage coefficient will be initially selected to ensure that recharge
from Layer #1 to Layer #2 is consistent with the published recharge rates of 8 to 10
inches per year.
2.4.5 Preliminary Selection of Natural Hydrologic Stresses
Natural recharge to Layer #1 is equal to Rainfall Runoff and Evapotranspiration. On
these excessively drained sand pine hills, the recharge to Layer #1 is generally about 15
inches per year with the following components:
Project No. 93-0597
Page 8
Rainfall = 50 inches/year •
Rainfall Runoff = 0.2 inches/year (Curve Number = 45)
Evapotranspiration = 35 inches/year
The evapotranspiration rate in the lakes and poorly drained soils around the lakes is about
50 inches/year.
Recharge to Layer #1 will therefore be simulated as 15 inches/year on the excessively
drained sandy soils and 0 inches/year in the lakes. It is important to note that this is
annual rechargefromthe atmosphere to the water table aquifer (Layer #1) and not
recharge to the Floridan aquifer.
The evapotranspiration rates will increase in the postdevelopment condition due to the
change in vegetative cover, the rise in water table, and the controlled rate and
distribution of the reclaimed water spray. Postdevelopment evapotranspiration rates on
an optimally irrigated golf course is close to 50 inches per year. Therefore, the increase
in evapotranspiration of the irrigated turf grass (50 in/yr) over the predevelopment pine
communities (35 in/yr) is on the order of 15 inches per year. This translates to a
potential additional disposal capacity of 270,000 gpd over this 240 acre site.
In order to take advantage of the increase in postdevelopment evapotranspiration, the
MODFLOW Evapotranspiration Module will be used to automatically model the increase
in evapotranspiration as the water table rises.
2.5 Calibration
Calibration of a flow model refers to a demonstration that the model is capable of
producing field-measured heads which are the calibration values.. Calibration is
accomplished by finding a set of parameters, boundary conditions, and stresses that
produce simulated heads that match actual field-measured values within a preestablished
range of error.
There are basically two ways of finding model parameters to achieve calibration; (1)
manual trial and error adjustment of parameters and; (2)automated parameter estimation.
The manual method is the one most preferred by the FDEP practitioners and will be the
method used in this modeling effort.
As requested by the FDEP, the field data used in the calibration will be the site-specific
predevelopment ground water table contour map.
2.6 Sensitivity Analysis
The purpose of a sensitivity analysis is to quantify the uncertainty in the calibrated model
caused by uncertainty in the estimates of aquifer parameters, stresses, and boundary
conditions. During a sensitivity analysis, calibrated values for hydraulic conductivity,
storage parameters, recharge, and boundary conditions are systematically changed within
previously established ranges. The magnitude of change in heads from the calibrated
Project No. 93-0597
Page 9
solution is a measure of the sensitivity of the solution to that particular parameter. The
results of the sensitivity analysis are measured by the effects of the parameter change on
the average measure of error selected as the calibration criterion.
2.7 Model Verification
Owing to uncertainties in the calibration, the set of parameter values used in the
calibrated model may not accurately represent field values. Consequently, the calibrated
parameters may not accurately represent the system under a different set of hydrologic
stresses.
During verification, values of parameters and hydrologic stresses determined during
calibration will be used to simulate a transient response for which a set of field data
exists. The hydraulic loading and observed ground water level responses of the golf
course system and existing percolation ponds will be used for verification of the
calibrated model parameters.
2.8 Prediction
In the predictive simulation, the parameters determined during calibration and verification
will be used to predict the response of the system to future events. It is at this point that
the increase in evapotranspiration will be taken into account in the postdevelopment
condition.
In addition to the natural stresses, artificial recharge stresses will be applied to the
calibrated/verified model to simulate the ultimate disposal capacity of the site. This
exercise is a trial and error process where the recharge distribution is varied from zone
to zone within the golf course until the ground water mound is within the level acceptable
to the FDEP. Acceptable, in this sense, means that the mound does not rise to within
2 feet of the ground surface at any point.
The results of the prediction will be the percolative capacity of the site and the
approximate distribution of disposal capacity within the site.
2.9 Field Audit Recommendations
The model domain will extend approximately 1000 feet beyond the limits of the property
where detailed geotechnical data is not available. Therefore, by necessity, there will be
extrapolation of aquifer parameters within this area. The model predictions will therefore
reflect some judgement in estimating these parameters. Because it is desirable to
maximize the disposal capacity of the site, it is recommended that the City of Ocoee
implement a monitoring plan which will facilitate a field audit of the model predictions.
Such a plan will allow the city to maximize the actual permitted disposal capacity of the
site in the future.
This operating plan will include ground water level observation wells to measure the
mound and compare it to the model prediction. After approximately a year of loading
•
Project No. 93-0597
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at 75% of the permitted capacity, a field audit can be conducted to re-rate the site
capacity based on actual performance. Our experience shows that this is the most
effective and assured approach for maximizing the disposal capacity of a large facility,
and is also preferred by the FDEP.
2.10 Water Balance and Nutrient Balance
The following factors limit the effluent disposal capacity of a reclaimed water irrigation
scheme:
■ Percolative (or hydraulic) capacity which is the ability of the sprayfield to be
hydraulically loaded with effluent and excess rainfall, (i.e. precipitation-runoff-
evapotranspiration) without creating adverse groundwater mounding impacts
(i.e., seepage outcrops and ponding conditions). From a treatment and
operational standpoint, it is desirable to maintain the ground water mound at a
minimum depth of 2 feet below land surface.
• Uptake of effluent chemical constituents (primarily nitrogen and phosphorus) by
the vegetative cover and the soil plant-root zone to limit potential adverse
groundwater quality impacts.
• Holding pond capacity which is required for storage during periods of excess
precipitation, down time for maintenance of the irrigation equipment, or other
standby time. The FDEP, by rule, requires a minimum wet weather storage
equivalent to 3 days of average daily flow.
• "Hardware" and operational (management) limitations related to the capacity of
the installed pumps and transmission lines and the available hours for irrigation,
rotation schedule, etc.
One result of the MODFLOW analysis will be the percolative capacity of the site. This
percolative capacity will be used in a spreadsheet model for the water balance and
nutrient balance computations for the golf course site.
2.11 Final Report
A modeling report will be prepared in a format acceptable to the FDEP, and will include
the following sections:
• INTRODUCTORY MATERIAL
• HYDROGEOLOGIC SETTING AND CONCEPTUAL MODEL
• MODEL DESIGN AND RESULTS
The Code
Relationship Between Conceptual Model and Numerical Model
Project No. 93-0597
Page 11
Model Calibration and Verification
Sensitivity Analysis
Predictions
Water Balance and Nutrient Balance
• MODEL LIMITATIONS
• SUMMARY AND CONCLUSIONS
• REFERENCES
• APPENDICES •
Note that field audit recommendations may be presented separately from the modeling
report.
3.0 SCHEDULE
The estimated time for completion of this study is 7 to 9 weeks from your authorization
to proceed. In order to expedite completion of the project, we will need your assistance
to obtain the following information:
• Hydrologic monitoring data and flow records maintained by Robert
Holland at the city's wastewater treatment plant
• AUTOCAD data file in DXF format containing the as-built plans of the
golf course
• Stormwater management reports which describe control levels and control
mechanisms for the on-site lakes
Upon receiving authorization to proceed from the city, an initial meeting will be arranged
with FDEP staff to present the Plan of Study (similar to that outlined in this proposal).
Follow up meetings will be scheduled with FDEP staff as necessary to present details and
obtain concurrence on key aspects of the model such as the grid layout, the calibration,
etc., as the modeling progresses. We believe that by working closely with the FDEP
during all phases of model set-up and calibration, we can ultimately reduce their
response time to our request for permit modification.
Project No. 93-0597
Page 12
4.0 ESTIMATED COST
U
Item// Task Description Unit Rate Quantity Amount
A FIELD VISIT& DATA REVIEW
A.1 Senior Engineer/Scientist hr $85.00 6 $510.00
B GROUND WATER MODELING
B.1 Principal Engineer/Scientist hr $100.00 6 $600.00
B.2 Senior Engineer/Scientist hr $85.00 100 $8,500.00
C DOCUMENTING & REPORTING OF MODELING STUDY
C.1 Principal Engineer/Scientist hr $100.00 6 $600.00
C.2 Senior Engineer hr $85.00 20 $1,700.00
C.3 Drafting Services hr $30.00 24 $720.00
C.4 Secretary hr $30.00 16 $480.00
D MEETING TIME & COORDINATION
D.1 Principal Engineer/Scientist hr $100.00 8 $800.00
D.3 Senior Engineer/Scientist hr $85.00 10 $850.00
TOTAL $14,760.00
4
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~vim Professional Service Industries, Inc.
Jammal & Associates Division
December 21, 1993
Proposal No. 757-3-652
TO: The City of Ocoee
150 North Lakeshore Drive
Ocoee, Florida 34761
Attention: Mr. James W. Shira, P.E.
City Engineer/Utilities Director
SUBJECT: Proposed Scope of Work and Cost Estimate,
Evaluation of Effluent Disposal Via Spray Irrigation for City of Ocoee
Golf Course Site,
Ocoee, Florida
Dear Mr. Shira:
As requested, we have prepared our proposed scope of services to complete the mounding
analysis for the above referenced site and provide input to modifications of the existing
Florida Department of Environmental Protection (FDEP) permit for the site. Our
proposed scope of work, related fees, and time schedule are presented herein.
PROPOSED SCOPE OF WORK
Based on our understanding of the project requirements and the project history,we envision
that our work will consist of five tasks which will be performed sequentially. To summarize,
Tasks 1 and 2 will consist of compiling and/or generating site- specific soil, surface water,
groundwater level, and loading rate information as input to the preparation of groundwater
level maps and formulating our approach to the project. Task 3 will consist of the
formulation of our analysis methodology and subsequent presentation to and interaction with
representatives of the FDEP. The implementation of our analysis/modeling, summary
report preparation, and response to FDEP comments will comprise Tasks 4 and 5,
respectively. A brief summary and schedule relative to each of the tasks follows.
1675 Lee Road • Winter Park, FL 32789 • Phone:407/645-5560 • Fax:407/645-1320
City of Ocoee Golf Course
'Proposal No. 757-3-652 -2
Task 1
Based on our understanding of the project history, Task 1 will consist of compiling previous
site-specific subsoil and groundwater level reports and evaluations prepared by previous
consultants (including our firm). As you are aware, the bulk of this work was completed
during our earlier involvement with the project. Therefore,we do not envision that this task
will require a significant amount of time and can be completed within one week of
authorization to proceed.
Task 2
We understand that the golf course will be open to the public on January 28, 1993. Recent
visits to the site and discussions with the golf course architect and the City of Ocoee's
general engineering consultant indicate that the site is being heavily irrigated as part of the
"greening in" of the course. We are currently installing a total of ten monitoring wells that
were required by the FDEP for the groundwater monitoring plan approved with the original
permit application. Groundwater level data for these wells should be available by mid-
January, 1994.
The referenced monitoring wells will provide valuable insight into the groundwater level
conditions on the site as they relate to the heavy irrigation required during the greening in
period for the golf course. In addition to the data provided by these monitoring wells, we
propose to install a number of temporary piezometers in areas of the site where
groundwater level data is not available. Based on recent discussions with representatives
of the FDEP, it was their impression that the temporary piezometers would be installed
prior to commencement of the full evaluation of the site. These piezometers would be
installed by hand, in areas that would not be considered a hinderance to course
maintenance.
The groundwater level data from the monitoring wells and temporary piezometers,
combined with irrigation/loading data from the golf course architect will be compiled and
utilized to prepare current groundwater level maps for the site. This task will require
approximately four weeks to complete following authorization of the project. We
understand that ground surface and well datum elevations at monitoring wells currently
being installed by our firm will be determined by others. We would request that elevations
at the proposed temporary piezometers by determined at the time the monitoring wells are
surveyed.
Tasks 3 and 4
Once groundwater level maps have been prepared for the current site conditions, we will
formulate a modeling/analysis approach that will later be presented to the FDEP for their
review and comment. It is possible that the evaluation of the site may not require a fully
three-dimensional analysis. It is conceivable that groundwater level data from the
monitoring wells and temporary piezometers, in concert with loading rate data, would allow
us to determine a safe loading capacity for the site without performing a mounding analysis.
City of Ocoee Golf Course
Proposal No. 757-3-652 -3
Once we have formulated our analysis strategy, we will meet with representatives of the
FDEP to discuss and present our proposed methodology and reach agreement as to specifics
of the model/analysis. Once this agreement has been reached,we will begin our evaluations
in earnest. While we are completing our evaluations,we will update the FDEP periodically
to discuss the project status and to address any conditions which were not anticipated during
our initial discussions/agreement. We anticipate Tasks 3 and 4 can begin within three to
four weeks of authorization to proceed and can be completed within eight to ten weeks
following project commencement.
Task 5
Upon completion of our analysis, we will prepare a summary report for the City and FDEP
summarizing our approach, the analysis and results, and our recommendations relative to
the future utilization of the site. We will work very closely with the FDEP during this
process to assure that by the time our final report is submitted for review, all concerns will
have been addressed. Therefore, it is our opinion that final review and approval by the
FDEP should take less than thirty days. Relative to project time frames, and in
consideration of the other tasks involved in this project, we anticipate that we can submit
the final report to the FDEP not more than 12 weeks following authorization for proceed.
Level of Effort and Estimated Fees
For this project, mainly three professionals will perform the work. For your review and
consideration, we have broken down the anticipated involvement for each individual (in
man-hours) for each task area. The following table summarizes the anticipated involvement,
by task.
Level of Effort
S. E. Jammal, P.E. Doug Hearn, P.G. Scott Cavin, E.I.
Task # (Principal Engineer) (Sr. Hydrogeologist) (Project Engineer)
1 1 4 --
2 6 16 --
3 12 28 --
4 10 24 40
5 8 12 24
An outline of the proposed scope of services and related costs to complete all Tasks are
provided on Attachment A. The anticipated fee for our involvement in the project is
$13,800. Please note that due to unforeseen circumstances and/or revelations during the
project, our fees may decrease if work items may be deleted. Therefore we anticipate that
oI% IlaigaLfrs may vary between $12,000 and $15,000 for the work.
rte•
City of Ocoee Golf Course
Proposal No. 757-3-652 -4
As described above, it is possible that a full-fledged mounding analysis with three-
dimensional modeling may not be required for this project. In the event that the FDEP is
willing and will approve a site rating based on recent historical data, the line item and
related fees presented as Item 4.1.3 would be eliminated from our contract, a net savings
of $2,000 from the estimated project total of $13,800.
CLOSURE
PSI/Jammal & Associates Division appreciates the opportunity to submit our proposal for
Ocoee Golf Links project and trust that this proposal will address your needs and concerns
for the project. Should you have any questions or require additional information, please
contact the undersigned at (407) 645-5560.
Sincerely,
PSI/JAMMAL & ASSOCIATES DIVISION
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Enclosure:
Attachment A
7573652.001
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•Orlando
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,ENGINEERING SCIENCES •GainesviIle
•Fort Myers
Consultants In:Geotechnical Engineering • •Merritt Island
Environmental Sciences•Construction Materials Testing •Daytona Beach
•West Palm Beach
December 22, 1993
City of Ocoee
150 North Lakeshore Drive
Ocoee, Florida 34761
Attention: Mr. James W. Shira, P.E.,
City Engineer/Utilities Director
Reference: Proposal to Perform Groundwater Modeling
City of Ocoee Public Golf Course and
Reclaimed Water Disposal Site
Ocoee, Florida
Dear Mr. Shira:
Universal Engineering Science (UES) is pleased to submit the scope of services, cost estimate,
and schedule to complete the mounding analysis for the City of Ocoee's Public Golf Course
Reclaimed Water Disposal Site. As described in our Statement of Qualifications and as
presented in our presentation, UES has extensive experience in successfully completing
mounding analyses for effluent disposal sites of similar nature to the golf course site.
Mr. Thomas Zankert, P.G., who will be performing the computer modeling for the project, has
been working on effluent disposal projects in Florida for the last eight years. He has a thorough
working knowledge of the reuse rule (FAC 17-610) and of MODFLOW which is the model of
choice for the mounding analysis. He has also established a good working relationship with
FDEP personnel directly responsible for review and approval of the groundwater modeling. All
of these aspects are essential to establish a defensible effluent disposal model for the golf
course site and to resolve the pending permitting issues.
PROJECT UNDERSTANDING
Based upon our file review and our discussions with Mr. Ken Hooper, P.E. and Ms. Sarah
Whitaker of the Florida Department of Environmental Protection Groundwater Section a
groundwater mounding analysis is required to establish the permittable disposal capacity for the
golf course site.
The proposed effluent disposal capacity for the site is 2.25 mgd which will be applied by a
combination of spray irrigation of the golf course and rapid infiltration via two existing and two
proposed rapid rate percolation ponds at the site. The groundwater modeling efforts for the site
were rejected by FDEP for reasons related to model set-up and calibration. In a Letter of
Understanding, the City of Ocoee agreed to limit the disposal capacity of the golf course site to
1.0 mgd pending results of additional groundwater modeling efforts. The City also agreed to
submit the results of the mounding analysis, and the necessary permit modifications, if required,
to FDEP no later than March 31, 1994.
3532 Maggie Blvd. • Orlando, FL 32811 • (407) 423-0504
City of Ocoee
Attention: Mr. James W. Shire, P.E.,
City Engineer/Utilities Director
Reference: Proposal to Perform Groundwater Modeling
City of Ocoee Public Golf Course and
Reclaimed Water Disposal Site
Ocoee, Florida
December 22, 1993
Page 2
PROJECT APPROACH
In order to establish the permittable effluent disposal capacity for the golf course site, UES
proposes to perform a mounding analysis using the groundwater flow model MODFLOW. Based
upon our experience and our discussions with Sarah Whitaker, MODFLOW is the model of
choice. In the MODFLOW model structure one can account for site specific hydrogeologic
features such as the shallow hardpan layer and the sink hole lakes, both which are important
in the development of the groundwater mound in response to the application of the treated
effluent. UES proposes to prepare a permittable mounding analyses to establish the effluent
disposal capacity for the site by conducting the four following tasks.
TASK 1 - Construct Conceptual Hydrogeologic Model
For this task, UES will review and summarize existing site specific and regional hydrogeologic
data from existing site specific reports and published data by the Florida Geologic Survey, the
St. Johns River Water Management District and other governmental agencies. We also plan to
review and analyze the water level data which the City has been collecting at the site. This data
will be used for the set up and calibration of the model. Data to be compiled include information
regarding site stratigraphy, depth and thickness of confining beds, hydraulic conductivities of the
soils, water level data and variations, climatic data, and other data needed for input into the
groundwater flow model. Based on this review, we will construct a conceptual model of the site
which will be used to set up (and later defend) the model structure within MODFLOW. This task
is extremely important since understanding the site specific hydrogeology is essential prior to
attempting to construct a mathematical analog of the site.
TASK 2 - Groundwater Modeling
The initial task will be to set up the model and model grid. We plan to extend the model grid
beyond the site boundaries to incorporate regional hydrogeologic boundaries such as lakes and
groundwater divides. Using this approach will eliminate FDEP's concerns regarding influence
of the boundary conditions on the predictive analyses.
Upon completion of the model set up, we will present this data and the proposed modeling
approach (including the treatment of the sink hole lakes in the model) to FDEP for discussion
to minimize the inquiries on the modeling methodology after the results are presented to the
agency.
We will then proceed to calibrate the model using both predevelopment and postdevelopment pp
(load test) water table data to assure that the model response reasonably simulates the "
City of Ocoee
Attention: Mr. James W. Shira, P.E.,
City Engineer/Utilities Director
Reference: Proposal to Perform Groundwater Modeling
City of Ocoee Public Golf Course and
Reclaimed Water Disposal Site
Ocoee, Florida
December 22, 1993
Page 3
conditions observed in the field. In addition, we will perform a sensitivity analysis of the input
parameters to assure that model set up and input will provide a defensible mounding analyses.
Once the model is calibrated, we will run the predictive analyses to establish the site disposal
capacity for both the golf course spray irrigation and the existing and proposed percolation
ponds. The predictive analyses are only meaningful if the model is calibrated properly. We have
allocated a total of 50 hours for calibration which should be adequate to calibrate the model to
the degree acceptable to FDEP.
TASK 3 - Report Preparation
In order to speed up the permitting process and to minimize questions from FDEP, UES will
prepare a report which will present the model set-up, assumptions, calibration procedures, and
modeling results in an organized and concise manner. We also plan to present the results to
FDEP personnel in a meeting prior to submitting the final report to address any questions that
they may have.
TASK 4 - Permitting Assistance
UES is prepared to assist the City of Ocoee with the permit modification or negotiations with
FDEP, if required.
SCHEDULE
In order to meet the City's March 31, 1994 deadline, we propose to conduct the above work
according to the following schedule:
Task Completion Date
Review& Compile Existing Site Specific & Regional Hydrogeologic Data 1/22/94
Set-Up Model & Meet with FDEP to Present Approach 2/11/94
Groundwater Modeling 3/11/94
Draft Report to City of Ocoee 3/18/94
Final Report to FDEP 3/29/94
City of Ocoee
Attention: Mr. James W. Shira, P.E.,
City Engineer/Utilities Director
Reference: Proposal to Perform Groundwater Modeling
City of Ocoee Public Golf Course and
Reclaimed Water Disposal Site
Ocoee, Florida
December 22, 1993
Page 4
CLOSING
The cost estimate to complete the above mentioned tasks is attached. If acceptable, we will
perform the proposed work in accordance with our contract with the City of Ocoee and the
attached Cost Estimate. Please be assured that UES understands the urgency of the pending
permitting issues for the golf course, and we feel confident that using the proposed modeling
approach and Mr. Zankert's modeling experience with MODFLOW at similar sites in Central
Florida we will help resolve the pending permitting issues.
UES appreciates the opportunity to provide the City of Ocoee with assistance on this project.
If you have any questions during the review of this proposal please call us at 423-0504.
Respectfully submitted:
Universal Engineering Sciences
__A-tNJ).241_,4-
Thomas M. Zankert, P.G.
Senior Hydrogeologist
Martha D. Gia4:/.a-Q
Project Coordinator
TMZ:MDG:mec
Enclosure: Exhibit I - Cost Estimate
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