HomeMy WebLinkAboutAgenda Report - November 1, 2005 B-01 SMAGENDA ITEM
&J& CITY OF LODI
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AGENDA TITLE: Accept West Yost & Associates Study for Full Implementation of
Woodbridge Irrigation District Surface Water Supply
MEETING DATE: November 1, 2005 (Special Meeting)
PREPARED BY: Public Works Director
RECOMMENDED ACTION: That the City Council accept the West Yost & Associates (WYA) study
for full implementation of the Woodbridge Irrigation District (WID)
surface water supply.
BACKGROUND INFORMATION: At the April 19, 2005, Shirtsleeve Meeting, staff presented alternatives
for implementing the 6,000 acre-feet per year (AFY) surface water
supply acquired from WID.
The alternatives included groundwater recharge and/or constructing a surface water treatment plant to
address the existing groundwater overdraft conditions and meeting future demands associated with Lodi's
projected growth and recommended further study of these options. On April 20, 2005, Council approved a
task order with WYA for further study and recommendation for full implementation of the WID surface water
supply.
The attached study provides an analysis of the alternatives, comparison criteria and preliminary cost
estimates. Based on the qualitative comparison criteria, a southerly -positioned groundwater recharge basin
is the recommended alternative. The surface water treatment plant alternative does provide the most
tangible benefit, but at significantly higher costs (page 21). The study also includes discussion on an interim
plan to utilize raw water for irrigating schools and parks near the WID South Main Canal.
Present worth analysis, including capital, operational and maintenance costs, are presented in the report.
Eventually, a decision must be made as to the proportionate funding responsibility between existing users and
future development.
Considering the significant impact that any of the alternatives will have an the future of Lodi's water supply,
staff recommends that Council accept the attached report and schedule a subsequent Shirtsleeve Meetings)
and eventually a public hearing to provide a forum for more detailed discussion and to address questions, at
which a decision on direction should be made.
FISCAL IMPACT: None at this time.
FUNDWG AVAILABLE: Not applicable. /"fin _i
Richard C. Prima, Jr.
Public Works Director
Attachment
cc: City Attorney
City Engineer
Assistant waterANastewater Superintendent
APPROVED:
Blair King, ity Manager
J, Mater+CWYATask0rder_accept.doe 9/2912005
TECHNICAL MEMORANDUM NO. 1
DATE: May 23, 2005 Project No.: 809-08-05-01
TO: Charles Swimley
City of Lodi
FROM: Dave Peterson
Chris Ewers
West Yost & Associates
SUBJECT: City of Lodi—Full Surface Water implementation Study
Introduction
The City of Lodi contracted with the Woodbridge Irrigation District (WID) to provide
6,000 AF/year of untreated surface water (raw water) for 40 years in May, 2003. The City
is currently examining its options for developing this water supply.
This technical memorandum addresses construction and operation of two alternatives for
developing the water supply:
A groundwater recharge basin at various proposed locations around the city's
perimeter
• A water treatment plant serving the City of Lodi's potable water system
The intent of this study is to provide the City with the tools to take the next logical step in
implementing the WID surface water supply with an eye toward long-term benefit, rather
than short-term consequence. This document provides an analysis of each alternative,
comparison criteria, and a recommended alternative. It also addresses an interim plan to
irrigate schools and parks near the WID South Main Canal with raw water. If
implemented quickly, this interim plan would allow the City to use a portion of the WID
supply beginning at approximately December 2006.
All summary analyses of costs are provided in present worth (PW). This report evaluates
total costs for the facilities studied and does not attempt to distribute implementation
costs between new development and existing rate payers.
Surface Water Implementation Alternatives
WID's contract with the City of Lodi allows the City to bank up to three years of
delivery, or 18,000 AF. Absent a system for developing the WID surface water, the bank
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Technical Memorandum
Page 2 of 27
will fill in October, 2006. The design of surface water implementation alternatives
includes evaluations of how each alternative can accommodate this water in addition to
the 6,000 -AF annual WID delivery.
In preparation for this study, city staff designated sites that may be potential candidates
for groundwater recharge facilities, as shown in Figure 1. A westerly basin site is
feasible, but it is not evaluated as part of this study because the northerly and southerly
candidate sites reflect the least and most expensive recharge basin alternatives. The
Surface Water Treatment Plant (SWTP) is shown on Figure 2.
The City also estimated a groundwater unit cost of approximately $80/AF that can be
deducted from alternatives that replace water already being drawn from the City's potable
water system. This value is based on the cost to provide energy and manpower to the
City's groundwater wells to produce 1 AF of water. It does not include maintenance or
other ongoing costs associated with the wells or distribution system, given that the city
must continue to maintain these elements regardless of water source.
Groundwater Recharge Alternatives
Groundwater extraction rates have exceeded sustainable aquifer yield in the City of Lodi
sphere of influence for decades. The September 2004 "Surface Water Supply Options"
study commissioned by the City indicates an average annual lowering of the water table
by 0.35 feet per year since 1927. Given the local dependence on good -quality
groundwater and the availability of surface water through the WID surface water
agreement, groundwater recharge holds promise for the city.
The benefit of groundwater recharge isn't always apparent to the public. Probably the
most difficult aspect of groundwater recharge for a public agency is the difficulty of
demonstrating a direct local benefit. Local sentiment can run against an option that
underwrites the region's water needs at local expense.
Two means of groundwater recharge are available to the city: aquifer storage and
recovery (ASR) wells and single -purpose recharge basins.
ASR Wells — ASR wells allow users to inject water into an aquifer, then retrieve it
again when it is needed. Central Valley Regional Quality Control Board (RWQCB)
regulations currently prohibit degradation of groundwater, a difficult test for a water to
pass. Injecting even water treated to drinking water standards troubles RWQCB officials
for its potential to contaminate an aquifer with disinfection byproducts, oxidation of the
aquifer structure, and chemical reactions in the aquifer with water that changes the
aquifer's oxygen content. Raw water injection presents a higher risk in its potential for
aquifer contamination. The RWQCB is considering conditions under which treated water
injection would be allowed. However, it is not contemplating allowing injection of raw
water at this time. Because the WID water would have to be treated prior to injection,
ASR would be an additive cost on the water treatment plant alternative, so it was not
considered further in this study.
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Technical Memorandum
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Recharge Basins — Groundwater recharge through single -purpose recharge basins is
less problematic for regulators. Areas are set aside and graded flat to accommodate water
in large, shallow pools that percolate into the aquifer. The percolation rate for a site and
the annual duration of operation determine the area needed for the basin floor at any time.
These facilities obviously require more land than ASR wells. Other types of recharge
areas that would provide dual uses, such as parks and open spaces, are not considered in
this report because of their expense.
The operational skills needed to run a recharge basin are minimal (particularly in contrast
to an SWTP), but some operations and maintenance techniques can make the facility
more successful:
• An aquitard (low -permeability zone) shallower than 15 feet below the
basin floor should be excavated and removed.
• Alternating wet and dry cycles, minimizing cycle time (1-5 days).
Agencies can optimize basin recharge by maximizing wet times within the
cycle, and by minimizing water depth or pumping the basin dry.
• Sectioning basins to allow for rotation, just as farmers rotate fallow fields.
• Basin floors should be level with ridges or furrows to allow increased
surface area, trap fine sediments in troughs, and discourage algae growth.
• Basins should dry between long-term wetting cycles. An annual drying
time of 30-60 days is recommended.
• Basin floors should be periodically scraped to remove fine sediment and to
break up compaction. Unless the water supply has a lot of sediment, this
can be done every 2-5 years.
• Weed growth should be minimized in the basin floor. Herbicides, such as
Rodeo, have been successfully used, but this would require approval from
the Regional Water Quality Board or the Department of Health Services.
Basin banks and bottom can be cleared through manual and mechanical
means during the annual drying period as well.
Basin Area Required
The "Surface Water Supply Options" study includes an estimate of 1 foot/day (ft/day)
percolation rate.I This study uses a more conservative 0.5 feet/day to percolate 6,000
1 City of Lodi staff provided percolation readings of 0.02-0.11 ft/day for a period in March -April, 2005 in
stormwater basins C and G. These values were lower than the actual percolation rate because rainfall and
contributions from the drainage basins were not included in the calculations. Determining these
contributing factors is beyond the scope of this study. The Stockton East Water District (SEWD) has seen a
percolation rate of 0.5-0.6 ft/day near its water treatment plant, and 0.1-0.35 ft/day in a percolation basin
system west of the treatment plant. SEWD staff attribute the difference to preparation of the site near the
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AF/year with an operating time between March 1 and October 15. This study assumes a
shallow, 0.5 -foot pond depth and that the operating time will be split into cyclic periods
of 2 days of dry time for every four days of basin inundation. It is also assumed the basin
will be dried for 45 days beginning Oct. 16, at the end of the annual diversion schedule.
Given these factors and estimated rainfall and evaporation rates, the required basin floor
size is approximately 74 acres. If the acreage of basin was used to percolate for the
remainder of the year at the same rate and if the water were available, it would take more
than eight years of operation between deliveries of the WID contract water to percolate
the 18,000 AF bank of stored water.
This study's estimates of basin requirements are determined by assuming a rectangular
plan broken into four sections. Under this approach, the basin banks would be sloped at a
1V:5H gradient to permit mowing, with a 30 -foot -wide perimeter of aggregate base six
inches thick (Fig. 4). The water surface would be approximately 74 acres when
inundated, and the pond area at ground surface would be 82 acres. Assuming a 30 -foot
fence set back on all sides, the site would occupy approximately 88 acres.
The cost of the facility if built in 2006 is tabulated in Table 1.
Table 1: Recharge Basin Construction Costs
Description
Quantity
Unit
Unit Price
Capital Cost
Excavated material for export
759,600
CY
$ -
$ -
Permanent security fencing
8,060
LF
$ 28
$ 226,000
Perimeter aggregate base
248,000
SF
$ 1.20
$ 298,000
Canal turnout
1
LS
$ 25,100
$ 26,000
Insert flow meter, float/level valve and
vault
1
LS
$ 27,000
$ 27,000
Inlet piping
40
LF
$ 360
$ 15,000
Outlet riprap
4
CY
$ 140
$ 1,000
Sutotal
$ 593,000
Construction Contingency (20%)
1
LS
$ 119,000
$ 119,000
Engineering and Other Fees (15%)
1
LS
$ 89,000
$ 89,000
Subtotal
$ 801,000
Purchase land for basin
88
AC
$ 200,000
$17,574,000
CEQA/NEPA
1
LS
$ 100,000
$ 100,000
Total
$18,475,000
*Excavation costs are offset by the value of the excavated material to the contractor.
$ Assumes only a Negative Declaration required for basin environmental permitting.
Operation and maintenance costs for the basin are estimated at approximately $35,000
per year in 2005 dollars (1/2 of employee at $50,000/year full-time annual salary with a
water treatment plant before it was put into use and note percolation rates seem to improve with proximity
to the Mokelumne River. These factors cannot indicate the percolation rate to be used for the City of Lodi's
percolation basins because they are dependent on local variability in the soil. Nevertheless, they reinforce
the use of a 0.5-ft/day rate.
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1.4 multiplier for benefits). A basin scraping operation should be completed
approximately once every five years, at a cost of approximately $15,000.
Assuming WID provides the water previously banked for eight consecutive years, the
recharge basin would accept approximately 8,250 AF of raw water each of those years.
The water balance in the basin shown in Table 2 shows that precipitation and evaporation
effects lower the estimated groundwater recharge to approximately 7,900 AF per year
during the eight years of water bank depletion. After the water bank is exhausted, the
evaporation rate changes because the basin is only in service during the 7.5 months of
WID delivery.
Table 2: 79 -Acre Recharge Basin Water Balance
This indicates a percolation efficiency of approximately 95 percent for the duration of the
agreement. Note that percolation efficiency is a measure of water entering the
groundwater table, not water available to Lodi.
Potential Recharge Basin Site Considerations
The potential recharge basin site alternatives differ in location and acreage provided for
each (Figure 1). These differences have the following implications.
Northerly recharge basin sites:
Percolation Rate — The Natural Resource Conservation Service (MRCS) soil maps
indicate the area suggested by City of Lodi staff for a local recharge basin site is
underlain by an alluvium composed of sandy loam capable of good drainage with an
effective rooting depth of 60 inches or more. These indicate percolation rates used in this
study might be conservatively low for the northerly alternatives.
Available Acreage — The northern sites total 75 acres, less than the required 88 acres.
However, the higher the percolation rate, the smaller the area required for percolation
basins. Once the percolation rate is known for the available site, city staff can make a
more exact determination about the acreage required for the recharge basins. A 1 ft/day
rate would shrink the required percolation basin facility area (including perimeter
fencing, slopes, etc.) to approximately 51 acres.
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Banked
Typical -
Water
Year
Source
Year
Operation
Operation
Notes
Volume
Volume
AF
(AF)
Intake
8,250
6,000
Water Bank Year Operation: 6,000 AF +
18,000 AF/8 years
Rainfall
113
113
Ave. annual rainfall = 17.1 in./yr.
Evaporation
-462
-397
Ave. annual evaporation = 80.0 in./yr.
Percolation
1 7,901
5,836
This indicates a percolation efficiency of approximately 95 percent for the duration of the
agreement. Note that percolation efficiency is a measure of water entering the
groundwater table, not water available to Lodi.
Potential Recharge Basin Site Considerations
The potential recharge basin site alternatives differ in location and acreage provided for
each (Figure 1). These differences have the following implications.
Northerly recharge basin sites:
Percolation Rate — The Natural Resource Conservation Service (MRCS) soil maps
indicate the area suggested by City of Lodi staff for a local recharge basin site is
underlain by an alluvium composed of sandy loam capable of good drainage with an
effective rooting depth of 60 inches or more. These indicate percolation rates used in this
study might be conservatively low for the northerly alternatives.
Available Acreage — The northern sites total 75 acres, less than the required 88 acres.
However, the higher the percolation rate, the smaller the area required for percolation
basins. Once the percolation rate is known for the available site, city staff can make a
more exact determination about the acreage required for the recharge basins. A 1 ft/day
rate would shrink the required percolation basin facility area (including perimeter
fencing, slopes, etc.) to approximately 51 acres.
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Effect on Aquifer — The potential sites indicated by City of Lodi staff for local recharge
are situated just south of the Mokelumne River and are within 2,500 feet of the river.
(Figure 1). From a qualitative perspective, even the presence of a steepening aquifer
gradient away from the river may not prevent a substantial portion of the water percolated
in the Northerly recharge basin from returning to the river. The basin would effectively
widen the river, and correspondingly raise the groundwater gradient. Wells 7, 26, and 15
would most likely get some benefit from the northwestern site, and well 4R would most
likely see a groundwater surface increase from the northeastern site. If either alternative
is pursued, the City of Lodi must obtain site-specific data on percolation rates and
groundwater movement to clarify these issues.
Water Source Proximity — The WID's South Main Canal runs far from most of the
acreage suggested for the Northerly percolation basins. Even if the 13 -acre parcel on the
west side of Lodi is used, the remaining acreage required for a percolation basin would
have to be developed on the eastern side. This suggests three options: pumping and
piping the WID water to the Northerly percolation basin across Lodi (a pipeline distance
of roughly 4.25 miles), drawing the water from a shallow well on the Mokelumne River's
bank to fill the percolation basin, or creating a river intake for the percolation basin. All
of the options are evaluated here using a basin fill time of 24 hours (meaning the flow out
of the percolation basin would be equivalent to the flow in), or a flow of approximately
8,900 gpm.
Water source options, Northerly Basin Sites:
Pumping and piping from the WID South Main Canal (near Mills and Corbin) —
A 30 -inch (in.) pipeline alone (the size required to keep velocities below 5 feet
per second) would cost approximately $6.62 million without considering the costs
for navigating obstructions, such as Highway 99 and all the utilities along the
way.
Shallow well on the Mokelumne River — No matter where this intake was located,
it would effectively transfer shallow groundwater into the basin to become
shallow groundwater again.
Mokelumne River intake — The intake, with an intake basin, pump station, and
short outlet pipe (approx. 40 ft.), would operate 24 hours/day during the "wet"
cycles of the basin. If the intake was constructed in 2006 with a net discount rate
of 2 percent, the present worth of the facility would be approximately $3,453,000.
Operations and maintenance (O&M) costs are estimated to include power to drive
the pumps, half of one FT employee (salary $60,000, 1.4 benefits factor), and half
the annual power costs in maintenance.
During years when the City could operate the percolation basin and intake to draw
down banked water, the power charges are approximately those in Table 3.
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Table 3: River Intake Operation O&M Cost During Water Bank Depletion
Year
$ For the purpose of this study, maintenance cost is estimated to be half of power cost.
In a typical year of operation, the intake would pump 6,000 AF of water to the
percolation basin, resulting in the slightly lower O&M costs found in Table 4.
Table 4: River Intake Operation O&M Cost During Typical Year
Summer
Winter
Subtotal
Power cost
$ 6,678
$ 4,123
$
10,801
Demand cost
$ 427
$ 153
$
581
Meter cost
$ 547
$ 478
$
1,025
$
12,407
Personnel
0.5 x FT ($60k salary x 1.4)
$
42,000
Maintenance$
$
6,300
Total O&M/yr. for 8,250 AF
$
60,800
$ For the purpose of this study, maintenance cost is estimated to be half of power cost.
In a typical year of operation, the intake would pump 6,000 AF of water to the
percolation basin, resulting in the slightly lower O&M costs found in Table 4.
Table 4: River Intake Operation O&M Cost During Typical Year
Table 5 contains the capital and O&M present -worth costs for each year of the
WID agreement after construction in 2006 at a net discount rate of negative 1
percent (assumed 5 percent interest and assumed 6 percent annual increase in
energy costs). Dividing the present -worth total cost for the intake by the volume
of water delivered through it provides a unit cost for the water delivered through
the intake of approximately $26/AF. This value must be added to the cost of the
percolation basin itself.
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Summer
Winter
Subtotal
Power cost
$ 5,259
$ 3,247
$
8,506
Demand cost
$ 427
$ 153
$
581
Meter cost
$ 431
$ 377
$
807
$
9,894
Personnel
0.5 x FT ($60k salary x 1.4)
$
42,000
Maintenance$
$
5,000
Total O&M/yr. for 6,000 AF
$
56,900
$ For the purpose of this study, maintenance cost is estimated to be
half of power cost.
Table 5 contains the capital and O&M present -worth costs for each year of the
WID agreement after construction in 2006 at a net discount rate of negative 1
percent (assumed 5 percent interest and assumed 6 percent annual increase in
energy costs). Dividing the present -worth total cost for the intake by the volume
of water delivered through it provides a unit cost for the water delivered through
the intake of approximately $26/AF. This value must be added to the cost of the
percolation basin itself.
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Table 5: Present -Worth Costs for Mokelumne River Intake (2005 dollars)
Year
PW
Capitalization
Cost
PW O&M
PW Cost
Volume
Delivered
(AF)
2006
$ 3,452,941
$
-
$3,452,941
0
2007
$
62,034
$
62,034
8,250
2008
$
62,661
$
62,661
8,250
2009
$
63,294
$
63,294
8,250
2010
$
63,933
$
63,933
8,250
2011
$
64,579
$
64,579
8,250
2012
$
65,231
$
65,231
8,250
2013
$
65,890
$
65,890
8,250
2014
$
62,287
$
62,287
8,250
2015
$
62,916
$
62,916
6,000
2016
$
63,551
$
63,551
6,000
2017
$
64,193
$
64,193
6,000
2018
$
64,842
$
64,842
6,000
2019
$
65,497
$
65,497
6,000
2020
$
66,158
$
66,158
6,000
2021
$
66,827
$
66,827
6,000
2022
$
67,502
$
67,502
6,000
2023
$
68,183
$
68,183
6,000
2024
$
68,872
$
68,872
6,000
2025
$
69,568
$
69,568
6,000
2026
$
70,271
$
70,271
6,000
2027
$
70,980
$
70,980
6,000
2028
$
71,697
$
71,697
6,000
2029
$
72,422
$
72,422
6,000
2030
$
73,153
$
73,153
6,000
2031
$
73,892
$
73,892
6,000
2032
$
74,638
$
74,638
6,000
2033
$
75,392
$
75,392
6,000
2034
$
76,154
$
76,154
6,000
2035
$
76,923
$
76,923
6,000
2036
$
77,700
$
77,700
6,000
2037
$
78,485
$
78,485
6,000
2038
$
79,278
$
79,278
6,000
2039
$
80,078
$
80,078
6,000
2040
$
80,887
$
80,887
6,000
2041
$
81,704
$
81,704
6,000
2042
$
82,530
$
82,530
6,000
Totals
$ 3,453,000
$ 2,535,000
$5,988,000
234,000
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Southerly recharge basin sites:
Percolation Rate — NRCS soil maps indicate the presence of a moderately rapid -draining
sandy loam potentially underlain by shallow hardpan. Given the distance between the
river and the regional basin sites and generic soil composition at the sites, this study's
conservative estimate of 0.5 ft/day appears reasonable.
Available Acreage — The combined acreage on the suggested southerly site is
approximately 123 acres, and should easily accommodate the 88 acres calculated for the
recharge basin at a 0.5 ft/day percolation rate. The site also has the benefit of adjoining
the WID's South Main Canal on both sides of the West Lane, which bisects the site.
Effect on Aquifer -- This area isn't as promising as the local sites for percolation rates, but
the capacity to benefit the groundwater table by increasing groundwater elevations
without losing water back to the river is greater. Again, city staff will need groundwater
hydrology data to make an informed decision about which recharge site to select. The site
is a mile south of the city's southern boundary and downgradient from the city's wells.
Percolation could be expected to eventually raise the surface of the aquifer beneath the
City of Lodi due to a backwater effect. The extent of overdraft in the existing aquifer
makes estimations of when the aquifer would begin rising under the City of Lodi
impossible without more data and analyses.
Water Source Proximity — The WID's South Main Canal runs adjacent to the Southerly
percolation basin site, eliminating the need for an intake as required at the Northern sites.
Recharge Basin Cost
Table 6 contains the present -worth costs for the recharge basing over the lifetime of the
WID agreement, beginning from the earliest construction of the basin possible, in late
2005 (estimate begins at 2006 below). The total present -worth cost is divided by the total
water to be developed through this alternative through 2042, for a present -worth unit cost
of approximately $83/AF. Table 7 summarizes the present -worth unit costs for each of
the basin sites.
Two elements could cause this estimate to vary substantially: percolation rate and
excavation spoils use. The higher the percolation rate, the smaller the basin floor area
required (and less water lost to evaporation). If investigation of the final recharge basin
site were to determine the average rate to be 1.0 ft/day, the basin facility, including
perimeter fencing, would require approximately 48 acres, rather than 88 acres. A 1 ft/day
percolation rate would change the present -worth water unit price to $48/AF and increase
the efficiency to 98 percent during years of water bank usage and 97 percent for the
remainder of the agreement.
The City of Lodi could also reclaim the land used for the recharge basin at the end of the
current, 40 -year surface water agreement with Woodbridge Irrigation District if the
2 Asssumes a net discount of 2 percent, given the relative independence of O&M to energy costs.
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contract were not renewed. Given current population pressures, the value of the land will
be considerable in 40 years. The capital construction costs above reflect allowing the
contractor to sell the soil excavated. If the city retained the soil and stockpiled it, the
capital costs for the project would rise considerably, depending on the distance from
excavation to stockpile sites and the costs for excavation.
Figure 6 details the estimated timeline required for construction of the percolation basin
and intake facilities. The timeline on Figure 6 assumes the contractor has an immediate
use for the soil generated in construction of the percolation basins like a large subdivision
or a dike -rebuilding project. This is the optimal scenario for the City. If the contractor
didn't need soil immediately, the City would be faced with two options: pay the
contractor to excavate and dispose of the soil immediately or allow the contractor to
excavate the site in a more leisurely fashion, probably doubling the nine-month
construction time allocated in the timeline on Table 6. If the City were to pay for the
excavation, the City could see an increase in project cost of approximately $2,264,000
(566,000 CY of excavation at $4/CY) for a basin sized for a percolation rate of 0.5 ft/day.
This would equate to a unit cost for the groundwater recharge basin of $94/AF for the
Southerly site, $120/AF for the Northerly site. Doubling the construction time would
make the percolation facility available at the end of the delivery season in 2007 at a cost
of 6,000 AF of water, effectively driving the unit cost for the Southerly basin to $86/AF
and $112/AF for the Northerly Basin.
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Table 6: Present -Worth Costs for Groundwater Recharge Basin (2005 dollars)
Year
PW
Capitalization
Cost
PW O&M
PW Cost
Volume
Delivered
(AF)
2006
$ 18,475,000
$
-
$18,475,000
0
2007
$
37,255
$
37,255
8,250
2008
$
36,524
$
36,524
8,250
2009
$
35,808
$
35,808
8,250
2010
$
35,106
$
35,106
8,250
2011
$
34,418
$
34,418
8,250
2012
$
33,743
$
33,743
8,250
2013
$
33,081
$
33,081
8,250
2014
$
32,433
$
32,433
8,250
2015
$
31,797
$
31,797
6,000
2016
$
31,173
$
31,173
6,000
2017
$
30,562
$
30,562
6,000
2018
$
29,963
$
29,963
6,000
2019
$
29,375
$
29,375
6,000
2020
$
28,799
$
28,799
6,000
2021
$
28,235
$
28,235
6,000
2022
$
27,681
$
27,681
6,000
2023
$
27,138
$
27,138
6,000
2024
$
26,606
$
26,606
6,000
2025
$
26,084
$
26,084
6,000
2026
$
25,573
$
25,573
6,000
2027
$
25,071
$
25,071
6,000
2028
$
24,580
$
24,580
6,000
2029
$
24,098
$
24,098
6,000
2030
$
23,625
$
23,625
6,000
2031
$
23,162
$
23,162
6,000
2032
$
22,708
$
22,708
6,000
2033
$
22,263
$
22,263
6,000
2034
$
21,826
$
21,826
6,000
2035
$
21,398
$
21,398
6,000
2036
$
20,979
$
20,979
6,000
2037
$
20,567
$
20,567
6,000
2038
$
20,164
$
20,164
6,000
2039
$
19,769
$
19,769
6,000
2040
$
19,381
$
19,381
6,000
2041
$
19,001
$
19,001
6,000
2042
$
18,628
$
18,628
6,000
Totals
$ 18,475,000
$
969,000
$19,444,000
234,000
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Table 7: Present -Worth Unit Costs of Percolation Basins per Site Location (2005
dollars)
Percolation Basin Site
PW Basin Unit
PW Intake Unit
Total PW Unit
Costs ($/AF)
Costs ($/AF)
Cost ($/AF)
Northerly
83
26
109
Southerly
83
0
83
Water Treatment Plant Alternative
Treatment and delivery for potable use would constitute a direct beneficial use of the
WID water. Under this alternative, the City would divert Mokelumne River water from
the South Main Canal, process it through a surface water treatment plant (SWTP), and
pump it through a transmission system to interconnections with the existing water
distribution system. The diversion would take place from March 1 to October 15 each
year.3 While using 6,000 AF in this timeframe results in an average diversion rate of 8.5
million gallons per day (mgd), a nominal capacity of 10 mgd was used in the analysis of
the SWTP alternative to provide flexibility of plant operations and production rates. This
flexibility can also absorb the 18,000 AF of banked water within approximately three and
a half years if the plant is operated at full capacity year-round, although this scenario is
not likely.
A surface water treatment plant is not 100 percent efficient, due to the generation of
waste streams. Part of this can be recycled, but actual deliveries to the transmission and
distribution system would average from 8.2 to 8.4 mgd, depending on the extent of waste
stream disposal from the SWTP. (The remaining volume comprises filter backwash and
solids.) Because 8.2 to 8.4 mgd is less than the average -day demand, the City would
continue to operate some of the groundwater supply facilities during SWTP operation.
The resultant intermixing of ground and surface water supplies within the distribution
system then would intensify the need for compatible water quality, particularly as regards
aesthetics, corrosion control, and disinfectant residual. For example, the surface water
supply would contain a disinfectant residual as required by the drinking water
regulations, and therefore, the City would need to maintain a compatible disinfectant
residual in the groundwater supply.
Finished water from the SWTP would need to comply with the drinking water regulations
as promulgated by United States Environmental Protection Agency (EPA) and the
California Department of Health Services (DHS). Forthcoming additional EPA and DHS
drinking water regulations include the Stage 2 Disinfectants/Disinfection Byproducts
Rule and the Long Term 2 Enhanced Surface Water Treatment Rule. A range of SWTP
design alternatives was considered in this analysis, including enhanced conventional
3 This alternative would be improved by changing the contract with WID to allow for year-round delivery.
The City could reduce its O&M costs associated with running groundwater wells and even decommission
some wells for the duration of its contract with WID.
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treatment and membrane filtration to ensure compliance with the current and forthcoming
drinking water regulations.
According to the City's hydraulic modeling, the influx of surface water in the system
would be used on the western side of the city during the 7.5 months of delivery.
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Table 8 summarizes preliminary design criteria for the SWTP.
Table 8. Preliminary SWTP Design Considerations
Component
Requirements/Comments
Canal diversion structure
. 10 mgd screening capacity with one unit out of service
• Flat screens in vertical slots
• Flow control gates for isolation, removal and manual
cleaning of screens from access platform above
Raw water pump station
• 10 mgd pumping capacity with one unit out of service
• Control point for SWTP rate of flow
Raw water pipeline
• Single 24 -inch diameter pipeline
• Accommodations for periodic pigging and inspection
Raw water storage
None
Pretreatment
. 10 mgd combined capacity for conventional
sedimentation basins, or 10 mgd with one unit out of
service for mechanically intensive processes
• Provisions to feed powdered activated carbon in case
of unusual raw water quality conditions
Filtration
. 10 mgd capacity with one conventional filter or
membrane cassette out of service
• Granular media (anthracite/sand) or vacuum -driven
membrane filters with integrity testing system
Post -filter adsorption
None
Disinfection
. Ozonation ahead of the filters
• Ultraviolet (UV) light as primary disinfectant
• Free chlorine as residual disinfectant
Corrosion control
. Chemical addition to ensure compatibility with other
water supplies and various water supply conditions
Fluoridation
Not at this time
Finished water storage
1.0 MG capacity in single -cell structure
Finished water pump station
• 10 mgd capacity with one unit out of service
Instrumentation
Adequate to coordinate SWTP operation with
distribution system storage and other water supplies,
and satisfy EPA and DHS reporting requirements
Electrical power
Dual services or double -ended distribution system
Standby power
• Adequate to operate diversion facilities and SWTP at
10 mgd capacity for 12 hours
Wastewater, solids and storm
. Drying beds with landscaped buffer zone
water handling facilities
. Supernatant recirculation to SWTP
• Storm water collection/storage/diversion as required by
Applicable Law
Operations area
. Adequate to house SWTP staff, chemical storage and
feed facilities, centralized control system, and
laboratory and maintenance functions
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Sanitary waste disposal
.
Connection to City sewer system
Hazardous waste storage and
.
As required by Applicable Law
disposal
Chemical and fuel delivery and
.
Secondary containment inside and outside (i.e., off -
storage areas
loading areas) with safe provisions for spill removal
Access and Security
•
Gate -protected all-weather access road(s) with
separate branches for staff, deliveries and public
visitors
•
Site buffer and physical barriers
•
Building access controls and video surveillance system
Architecture
•
Compatible with current and near -future surrounding
residential neighborhoods
•
ADA compliant in administrative areas and OSHA
compliant throughout SWTP
•
Sustainable design to conserve natural resources
•
Landscaping to enhance aesthetics yet conserve water
Cathodic protection and
.
As needed to prevent corrosion of pipelines and other
coating systems
metallic infrastructure
The operation of a conventional SWTP or membrane filtration plant will generate filter
backwash wastewater and pretreatment sludge as well as lesser volumes of sanitary, solid
and hazardous waste. Because passive solids handling and dewatering systems are
generally more cost-effective than mechanical dewatering systems, this analysis assumes
that the backwash wastewater and pretreatment sludge would flow to nearby decanting
and drying ponds, requiring approximately five acres of land area. (At $200,000/acre, the
land would cost $1 million; a mechanical sludge handling system would cost
approximately $243 million in capital costs alone.) A recirculation system would deliver
decanted supernatant from the ponds to the head of the SWTP. Periodically, the City
would isolate a pond, further dewater its contents, remove the dewatered solids, and
either dispose of the dewatered solids at a landfill or land application site or utilize the
solids in a co -composting facility. A modern SWTP incorporating recycling would be
99.5 percent efficient or better.
Table 9 summarizes the construction cost estimate for the SWTP prior to factoring in
contingencies and other cost line items.
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Table 9. Construction Cost Estimate for SWTP (2005 Dollars)*
Cost Component
Estimated Cost,
dollars
Mobilization/demobilization
800,000
General conditions
400,000
Bonds and insurance
1,250,000
Roads, grading, etc.
750,000
Landscaping and irrigation
750,000
Yard piping
1,500,000
Water treatment systems
Pretreatment
1,500,000
Ozone generators and contactors
2,000,000
Filter equipment, piping and
structures
2,500,000
UV equipment and building space
1,000,000
Chemical storage and feed systems
1,600,000
Solids handling system
1,000,000
Finished water reservoirs
1,000,000
Finished water pump station
1,000,000
Operations building
500,000
Electrical, instrumentation and control
systems, including standby power
2,630,000
Start-up and acceptance testing
750,000
Total (Rounded)
20,930,000
* For the purposes of comparison, a 15 mgd plant in Clovis, CA cost $26.0 million to
construct in 2002. A 30 mgd plant in Fresno, CA cost $31.5 million to construct in the
same year. Both costs are construction only - without engineering, etc. Economies of
scale apply to SWTP construction, so a lower capacity plant tends to have a higher unit
cost ($/mgd).
The City is considering several alternative locations for the canal diversion and SWTP.
This analysis provides a transmission system north to Turner Road, and south along the
west side of the South Main Canal as far as Harney Lane, with six connections to the
existing system (Fig. 2).
The total capital cost of the SWTP alternative, including transmission mains,
contingencies and other cost line items, is provided in Table 10.
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Table 10. Total Capital Cost of SWTP Alternative
Cost Component
Factor,
Length,
Diameter,
Unit Cost,
March 2005,
Mid -Point of
11
percent
feet
inches
dollars
dollars
Construction
Finished water
pipeline
—
6,050
12
157
$ 950,000
$ 1,223,000
w/restoration
Finished water
pipeline
—
3,200
18
185
$ 592,000
$ 762,000
w/restoration
Finished water
pipeline
—
13,500
24
235
$ 3,173,000
$ 4,084,000
w/restoration
10 mgd enhanced
conventional
—
—
—
—
$20,930,000
$26,950,000
SWTP
Subtotal
$ 25,647,000
$ 33,018,000
Construction
contingency -
20
—
—
—
$ 943,000
$ 1,214,000
pipelines
Construction
contingency –
25
—
—
—
$ 5,233,000
$ 6,737,000
other facilities
Subtotal
$ 31,823,000
$ 40,969,000
Engineering and
other fees -
15
—
—
—
$ 849,000
$ 1,092,000
pipelines
Engineering and
—
—
—
other fees – other
20
$ 5,233,000
$ 6,737,000
facilities
Subtotal
$ 37,905,000
$ 48,798,000
Property
l�1
—
—
—
—
$ 1,000,000
$ 1,000,000
acquisition
CEQA/NEPA(3)
—
—
—
—
$ 1,000,000
$ 1,000,000
Total
$ 39,905,000
$ 50,798,000
' Escalated at ten percent per year to March 2008.
2 Five acres for sludge drying beds @ $200,000/acre.
3 Placeholder value.
The operations and maintenance (O&M) cost of the SWTP alternative is estimated as
approximately $1,350,000/year for personnel (a plant operator and six
operator/technicians), chemical purchases, equipment repair and replacement, sludge
disposal, and other miscellaneous O&M cost line items. The total energy cost is
estimated as $770,000 per year assuming a finished water pump station discharge
pressure of 80 psi. Prorating these O&M costs for 7.5 months of SWTP operation results
in an annual O&M cost of $1,315,000/year. If the plant were operated year-round
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(requiring a variance in the City's agreement with WID) to deplete the banked water,
annual O&M costs would become $2,120,000.
Because the O&M cost are tied to supplies and energy costs, their rate of inflation is
calculated at six percent per year for this study. With an estimated interest rate of 5
percent, the net discount rate is -1 percent. Table 11 shows the annual costs associated
with the water treatment plant alternative, with operation beginning in 2009.
The total present -worth costs for the SWTP alternative divided by the amount of water
used from the WID agreement less the cost for pumping groundwater yields a present -
worth unit cost of $410/AF.
The two years spent constructing the treatment facility would mean a loss of 12,000 AF
for the City of Lodi because the 18,000 -AF water bank would be full.
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Table 11: Water Treatment Plant Present -Worth Costs (2005 dollars)
Year
PW Annual
Capitalization
Cost
PW O&M
PW Annual
Cost
Volume
Delivered
(AF)
2008
$51,000,000
$0
$51,000,000
0
2009
$1,471,309
$1,471,309
8,090
2010
$2,229,256
$2,229,256
11,202
2011
$2,251,773
$2,251,773
11,202
2012
$2,274,519
$2,274,519
11,202
2013
$1,425,096
$1,425,096
6,304
2014
$1,439,491
$1,439,491
6,000
2015
$1,454,031
$1,454,031
6,000
2016
$1,468,719
$1,468,719
6,000
2017
$1,483,554
$1,483,554
6,000
2018
$1,498,540
$1,498,540
6,000
2019
$1,513,676
$1,513,676
6,000
2020
$1,528,966
$1,528,966
6,000
2021
$1,544,410
$1,544,410
6,000
2022
$1,560,010
$1,560,010
6,000
2023
$1,575,768
$1,575,768
6,000
2024
$1,591,685
$1,591,685
6,000
2025
$1,607,762
$1,607,762
6,000
2026
$1,624,002
$1,624,002
6,000
2027
$1,640,406
$1,640,406
6,000
2028
$1,656,976
$1,656,976
6,000
2029
$1,673,713
$1,673,713
6,000
2030
$1,690,620
$1,690,620
6,000
2031
$1,707,697
$1,707,697
6,000
2032
$1,724,946
$1,724,946
6,000
2033
$1,742,370
$1,742,370
6,000
2034
$1,759,969
$1,759,969
6,000
2035
$1,777,747
$1,777,747
6,000
2036
$1,795,704
$1,795,704
6,000
2037
$1,813,842
$1,813,842
6,000
2038
$1,832,164
$1,832,164
6,000
2039
$1,850,671
$1,850,671
6,000
2040
$1,869,364
$1,869,364
6,000
2041
$1,888,247
$1,888,247
6,000
2042
$1,907,320
$1,907,320
6,000
Totals
$51,000,000
$57,875,000
$108,875,000
222,000
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Figure 7 details the estimated timeline required for construction of the SWTP and
delivery facilities.
Alternative Comparison
This study uses the following criteria to suggest an alternative for further refinement.
Minimize unit cost —The average treated water unit cost of $410/AF is approximately five
times that of the Southerly percolating basin.
Use of entire volume purchased from WID — Alternatives should develop the full 6,000
AF annual allocation and absorb the 18,000 AF banked with WID by the end of the
contract. All alternatives can do this.
Maximize public acceptance — The primary issue under this criterion can be found in the
City Council's disinclination to accept chlorination of the City's potable water supply.
The treatment alternative would require chlorination.
Implement quickly — If an alternative cannot be implemented by March 1, 2007, water
purchased by the City will be lost until a solution is placed in service.
Minimize environmental repercussions — Groundwater percolation basins can become a
source for disease vectors by becoming mosquito breeding -grounds, though proper
wet/dry cycling can minimize this. Treatment requires production and disposal of solids,
an environmental nuisance. All alternatives have some negative environmental
repercussions; a toss-up.
Maximize use of water by City — The selected alternative should maximize the percentage
of WID water that can be put to use by the City. The Northerly basin sites have the
potential to lose significant amounts of water back into the Mokelumne River. Similarly,
the percentage of WID water that could be recovered from the Southerly basin site could
be low due to loss of recharged water to areas outside of the City's groundwater sphere of
influence.
Recommended Alternative
Table 12 represents a decision matrix built on the criteria above. The "+" indicates
alternatives that pass the criterion, and a "-" indicates those not passing.
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Table 12: Decision Matrix for Surface Water Implementation
* The use of the water in the case of a percolation basin does not equate to direct benefit to the City of
Lodi. Recovery from groundwater percolation is dependent on a host of variables outside the scope of this
study, such as site selection and groundwater hydrology.
The qualitative comparison in Table 12 does not present a compelling technical case for
one alternative over the other. The Southerly recharge alternative appears to provide
balanced overall benefit to the City of Lodi and the region while minimizing further costs
associated with surface water implementation. The water treatment plant alternative
would provide the most tangible benefit to the City, but at a higher cost and a longer
implementation period. Ultimately, the decision must incorporate some form of
weighting of the criteria in discussions with the City policy -makers.
Interim Raw Water Usage Plan
The interim raw water usage plan would provide raw water to public facilities currently
irrigated from the City's potable water system. This parallel, raw -water system would
have no connection to the potable water system, and would eventually be used to provide
recycled water to these same properties. In the interim, the city could use the system to
provide raw water from the WID contract from the South Main Canal.
Layout
The initial layout of the interim water plan follows the proposed routing for the recycled
water plan suggested by City staff (Figure 3).
X:\Clients\809 Lodi\05-01 Full Surface Water Implementation\WMM LodiSurfaceWaterImplementation 2005_05_20.doc
Criteria
�
o
Ei
�
U
Alternates
_
Q
Q)
LOQ
N
U
°'
cu
�+
U
O
LO
o
4
N
c
O
N
N
Q)
E
E
Groundwater Recharge Basin (Southerly)
$ 18,475,000
+
+
+
+
+
_
Surface Water Treatment Plant
$ 51,000,000
-
+
-
-
+
+
* The use of the water in the case of a percolation basin does not equate to direct benefit to the City of
Lodi. Recovery from groundwater percolation is dependent on a host of variables outside the scope of this
study, such as site selection and groundwater hydrology.
The qualitative comparison in Table 12 does not present a compelling technical case for
one alternative over the other. The Southerly recharge alternative appears to provide
balanced overall benefit to the City of Lodi and the region while minimizing further costs
associated with surface water implementation. The water treatment plant alternative
would provide the most tangible benefit to the City, but at a higher cost and a longer
implementation period. Ultimately, the decision must incorporate some form of
weighting of the criteria in discussions with the City policy -makers.
Interim Raw Water Usage Plan
The interim raw water usage plan would provide raw water to public facilities currently
irrigated from the City's potable water system. This parallel, raw -water system would
have no connection to the potable water system, and would eventually be used to provide
recycled water to these same properties. In the interim, the city could use the system to
provide raw water from the WID contract from the South Main Canal.
Layout
The initial layout of the interim water plan follows the proposed routing for the recycled
water plan suggested by City staff (Figure 3).
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The interim plan would require a pumping station at the WID South Main Canal on the
northwest corner of Beckman Park. This pump station would provide approximately 150
feet of head to provide 60 psi to all parks and schools, a typical value for other municipal
sprinkler irrigation systems.
In modeling the irrigation demands, city staff have used the following demands from the
"Surface Water Supply Options Study."
Table 13: Irrigation Demands per Acre
Facility Irrigation
AF/acre*
Parks
2.62
Schools
2.03
* Based on actual 2002 usage and gross parcel acreages.
This study also used these values to generate demand estimates, and assumed that this
water must be delivered during the WID delivery, between March 1 and October 15. City
staff also noted city irrigation facilities are irrigated for five hours every other night. Park
lands would then require 25 gpm per acre during that five-hour irrigation period, and
schools would demand 20 gpm per acre.
City staff asked that facilities in Table 14 be included in the system for irrigation. Table
10 also provides the acreage and corresponding demand for each park based on a five-
hour rotation every other night.
Table 14: Irrigation Demands at Selected Facilities
Facility
Gross
Estimated
Acrea a
Unit
Demand
AF/acre
Annual
Demand
AF
Demand
(gpm)
Peterson Park
20.4
2.62
53.4
509
HenryGlaves Park
13.4
2.62
35.2
335
Reese School
8.8
2.03
17.8
170
Lodi High School
44.2
2.03
89.6
854
Vinewood Park and School
20.1
2.33
46.6
444
Lodi Middle School
19.2
2.03
39.0
372
Kofu Park
8.7
2.62
22.7
216
Tokay High School
49.2
2.03
99.8
951
Beckman Park
15.7
2.62
41.1
392
DeBenedetti Park
1 26.8 1
2.62
1 70.2 1
669
Total
1 226 1
1 515 14,912
A preliminary schedule of the irrigation rotation should be arranged to spread the supply
as evenly as possible between evenings and five-hour irrigation blocks. Table 15 includes
a sample schedule with a maximum flow of approximately 1,350 gpm.
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Table 15: Preliminary Irrigation Schedule for Selected Facilities
First five hours
Estimated Demand
Facility Irrigated (gpm)
Acreage
.........................................................................................................................................................................................
Reese School 8.8 170
Vinewood Park
20.1
444
and School
School
Peterson Park
20.4
509
Total1,123
Total
..........................................................................................................................................................................................
Kofu Park
8.7
216
Henry Glaves
13.4
335
Park
Lodi High
44.2
DeBenedetti
26.8
669
Park
Total1,221
Total1,226
Second five hours
Estimated Demand
Facility Irrigated (gpm)
Acreage
..........................................................................................................................
Beckman 15.7 392
Park
Tokay High
49.2
951
School
Total
1,343
.........................................................................
Lodi Middle
19.2
..................................................
372
School
Lodi High
44.2
854
School
Total1,226
The pipeline used in this project will become part of a larger recycled water use effort.
Because the growth in the system will occur on the west side of the recycled water
delivery system, this eastern portion is sized for this study as a 12 -in. diameter, PVC
irrigation pipeline.
When this system is used as a raw -water delivery system, crews will occasionally have to
use flushing hydrants downstream of the pump to move sediment out of the pipes because
flow rates can be as low as 1.4 feet per second (between the tee near Mills and the future
connection point near Evergreen and Paradise) during operation, and velocities during the
day will be zero. The minimum velocity to re -suspend settled sediments would be 5 feet
per second.
The pumping station specified for this study is mounted in a small skid building, an
electrically -driven station that can be moved to other sites when needed. The South Main
canal bank at Beckman Park would be penetrated with a 36 -in. reinforced concrete pipe
that would terminate in a 60 -in. manhole (Figure 5). This manhole would serve as a wet
well for the temporary pump intake. The canal bank itself would be modified to allow a
slide gate to seal the pipe when not in use. The pump outlet's 8 -in. flexible hose would
connect to a length of 8 -in. PVC pipe daylighting in Beckman Park. This would be
connected through a 8x12 -in. reducer to a 12 -in. tee at Century Boulevard.
The pipe downstream of the pump station would be fitted with periodic one -inch
combination air/vacuum valves to allow the pipe to fill and release the air the pump
station would entrain, and allow air to enter the pipe during shutdown and drain periods.
Isolation valves are anticipated in the raw water line on either side of major crossings,
such as the bore and jack under the South Main Canal near Century Boulevard and
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Technical Memorandum
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upstream of all delivery points. In addition, the system would include two flushing
hydrants along the WID South Main Canal, one at Peterson Park, and one at each of Lodi
and Tokay high schools.
This study assumes a three-phase, 480-V electrical supply is available near the pump
station site at the northwest corner of Beckman Park.
The interim water supply would deliver approximately 4.5 acre-feet of water every two -
night cycle, or about 515 acre-feet during the WID delivery period.
Table 16: Estimated Capital Cost for Interim Raw Water System (2005 Dollars)
Description
Qty
Unit
Unit Price
Rounded
Capital Cost
Temporary Pump Station
1
LS
$ 76,300
$ 77,000
12 -in. SDR -32.5 PVC Pie
16,070
LF
$ 64
$1,029,000
Pipeline a urtenances/fittin s
1
LS
$102,900
$ 103,000
Paving
11,650
SY
$ 50
$ 583,000
Mobilization
1
LS
$ 25,100
$ 26,000
Bore & Jack S. Main Canal
160
LF
$ 450
$ 72,000
Subtotal
$1,818,000
Construction Contingency 20%
1
LS
$142,400
$ 143,000
Engineering and Other Fees 15%
1
LS
$106,800
$ 107,000
Subtotal
$2,068,000
CEQA and Permitting
1
LS
$100,000
$ 100,000
Total
$2,168,000
Current electrical rates indicate annual operation will cost approximately $21,500 per
year. With a quarter -time personnel salaried at $50,000 (with a 1.4 benefit factor)
attending the system for the 7.5 months of operation ($11,000) and $9,500 annually for
parts and startup/shutdown maintenance, annual O&M becomes $42,000.
The unit cost for the City to operate the interim raw water system would be reduced by
the same $80/AF found in the SWTP alternative, and for the same reason: the water
delivered by this system would reduce the groundwater pumping necessary through the
existing potable water system.
The unit cost could vary depending on irrigation methods used. This study anticipates a
screen mounted in a manhole will filter large particles out of the raw water before they
are pumped. Larger -nozzle irrigation devices will be able to use the resulting water, but a
drip system would not. If a raw -water system is implemented, the City of Lodi
maintenance personnel will have to analyze their system to either implement a finer filter
at the pump intake or mechanical strainer at the pump discharge for drip -irrigation lines
or keep the drip -irrigation lines on the potable water system.
Experience with other, parallel raw- and treated -water systems has shown that the
Department of Health Services will scrutinize of this interim system carefully to avoid
the possibility of cross -connections between raw and treated water piping.
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Technical Memorandum
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Though unit costs will decrease with the time the system is in operation, costs are
provided here for the duration of the WID agreement to make it comparable with the
other alternatives. Table 17 shows the present -worth costs for the interim system using a
net discount rate of -1%. These costs include components that could be used in a recycled
water distribution system. The total present -worth costs divided by the total water used
by the system less the $80/AF savings in groundwater pumping determines the present -
worth unit cost of the water, $135/AF.
Figure 8 details the estimated timeline required for construction of the interim system.
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Technical Memorandum
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Table 17: Present -Worth Costs for Interim System 2005 dollars)
Year
PW
Capitalization
Cost
PW O&M
PW Cost
Volume
Delivered
(AF)
2006
$ 2,168,000
$
42,424
$2,210,424
309
2007
$
42,853
$
42,853
515
2008
$
43,286
$
43,286
515
2009
$
43,723
$
43,723
515
2010
$
44,164
$
44,164
515
2011
$
44,611
$
44,611
515
2012
$
45,061
$
45,061
515
2013
$
45,516
$
45,516
515
2014
$
45,976
$
45,976
515
2015
$
46,441
$
46,441
515
2016
$
46,910
$
46,910
515
2017
$
47,383
$
47,383
515
2018
$
47,862
$
47,862
515
2019
$
48,346
$
48,346
515
2020
$
48,834
$
48,834
515
2021
$
49,327
$
49,327
515
2022
$
49,825
$
49,825
515
2023
$
50,329
$
50,329
515
2024
$
50,837
$
50,837
515
2025
$
51,351
$
51,351
515
2026
$
51,869
$
51,869
515
2027
$
52,393
$
52,393
515
2028
$
52,922
$
52,922
515
2029
$
53,457
$
53,457
515
2030
$
53,997
$
53,997
515
2031
$
54,542
$
54,542
515
2032
$
55,093
$
55,093
515
2033
$
55,650
$
55,650
515
2034
$
56,212
$
56,212
515
2035
$
56,780
$
56,780
515
2036
$
57,353
$
57,353
515
2037
$
57,933
$
57,933
515
2038
$
58,518
$
58,518
515
2039
$
59,109
$
59,109
515
2040
$
59,706
$
59,706
515
2041
$
60,309
$
60,309
515
2042
$
60,918
$
60,918
515
Totals
$ 2,168,000
$
1,892,000
$4,060,000
18,849
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Technical Memorandum
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Summary
This technical memorandum addresses the implementation of surface water supply for
the City of Lodi from its WID agreement. Several assumptions must be validated prior to
proceeding with the projects presented in this technical memorandum.
Table 18: Primary Study Assumptions
Assumed variable
Factor
Groundwater recharge percolation rate
0.5 ft/da
Net discount rate for labor -dominated O&M costs
2 ercent
Net discount rate for energy- and materials -dominated O&M costs
-1 percent
Land acquisition cost
$200,000/acre
Irrigation inlet pressure at parks and schools
60 psi
Given these assumptions, the alternatives analyzed have the unit costs shown in Table 19.
Table 19: Cost per Acre -Foot for Alternatives Studied (2005 dollars)
Alternative
Unit Cost $/AF
Northerly Groundwater Recharge Percolation Basin
109
Southerly Groundwater Recharge Percolation Basin
83
Surface Water Treatment Plant and Pipelines*
410
Interim Raw Water Delivery System*
135
`These unit costs include savings from reduced groundwater pumping at existing wells.
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