Purified Water Feasibility Study
City of Napa Utilities
&
Napa Sanitation District
“You don’t know the value of
water until the well runs dry”
-
Ben Franklin
June 04, 2024
ATTACHMENT
1
❖
Determine volume of water supply available
❖
Regulatory requirements to ensure public safety
•
Water quality evaluation
•
Treatment train
•
Operator certification requirements
•
Residuals management
Purified Water Feasibility Study
ATTACHMENT 1
❖
Capacity options explored
❖
Seasonality and water availability
•
6 months per year
-
winter flows
•
12 months per year
-
urban drool,
natural inflow
and infiltration
•
Stormwater diversion limited to existing
conveyance capacity only
(no added EQ infrastructure)
Purified Water Feasibility Study
Alt 1
Alt 2
Alt 3
Feed Flow (MGD)
1.8 6.0
10.0 6 Month Annual
Water Produced
(AFY)
760
2,200
3,200
12 Month Annual
Water Produced
(AFY)
1,600
5,400
9,000
Determine volume of water available
**
Stormdrain
infiltration
adds up to 0.74 MGD in summer when collection conveyance capacity exists.
ATTACHMENT 1
Purified Water Feasibility Study
❖
Regulatory requirements to ensure public safety
Treatment Train:
1. Ozone
5. UV Advanced Oxidation
2. Biologically Activated Carbon 6. Secondary UV
3. Microfiltration
7. Chlorination
4. Reverse Osmosis
ATTACHMENT 1
Purified Water Feasibility Study
❖
Regulatory requirements to ensure public
safety
▪
Log Reduction Credits
▪
Staffing Requirements
➢
24/7 staffing for 12 months
➢
Operators
-
AWTO 5 or AWTO 3 always on site
➢
Technicians for laboratory, maintenance,
instrumentation
Process
Virus
Giardia cysts
Crypto oocysts
Min Required
20 14
15 AWPF
20.5 21.5
15 ATTACHMENT 1
Purified Water Feasibility Study
❖
Infrastructure requirements for all Alternatives
▪
Purified Water Feed Line
▪
Purified Water Finished Line
▪
RO Concentrate Line
▪
Backwash and Off
-
spec Line
Alt 1
Alt 2
Alt 3
Alt 4
Alt 5
Alt 6
Alt 7
Alt 8
Feed Flow
(MGD)
1.8 6.0
10 1.8
6.0 10
1.8 6.0
AWPF
Location
NapaSan
SWRF
Barwick
Jamieson
WTP
Reuse Type
Treated Water
Raw Water Augmentation
ATTACHMENT 1
Range of
Costs
Purified Water Feasibility Study
Annualized Costs
Alt 1
Alt 2
Alt 3
Feed Flow (MGD)
1.8 6.0
10.0 Water Produced
6 -
mo / 12
-
mo (AF/Y)
760 / 1,600
2,200 / 5,400
3,200 / 9,000
Operations
6 -
mo
–
12 -
mo ($M/Y)
$4M
-
$5.2M
$5.2M
-
$8.6M
$6.3M
-
$12.3M
Capital Costs
Alt 1
Alt 2
Alt 3
Feed Flow (MGD)
1.8 6.0
10.0 Infrastructure Costs
($M)
$11
-
$29
$21
-
$47
$33
-
$63
Treatment Costs ($M)
$110
$197
$237
Total Project Capital
Cost ($M
)
$120M
–
$139M
$218M
-
$245M
$270M
-
$300M
ATTACHMENT 1
The Purified Water Project is:
❖
Technically feasible
❖
Not cost
-
effective
at this time
Future Actions
❖
Monitor cost comparison of alternate
supplies
❖
Monitor regulatory requirements
❖
Monitor costs and public acceptance of
other facilities
Purified Water Feasibility Study Results
ATTACHMENT 1
Questions
or
Comments
ATTACHMENT 1
When will Purified Water make sense for Napa?
Purified Water Feasibility Study
ATTACHMENT 1