Board 2 Jan 2020 Staff Report_So Y FS_final_2 Page Handouts1/2/2020
1
SOUTH TAHOE PUBLIC UTILITY DISTRICT
Regular Board Meeting
Board Agenda Item 11.b.
South Y Feasibility Study
January 2, 2020
I. Bergsohn, PG, HG
Remedial Alternatives
2019 Regional Plume Characterization
(LRWQCB)
Questions – Open Forum
South Y Feasibility Study
1/2/2020
2
FEASIBILITY STUDY
Screen Modeled Alternatives for
Engineering Evaluation
(6 Alternatives)
1) Define Infrastructure Needs
2) Develop Life Cycle Cost
Estimates
3) Complete Initial Study
Checklists/Cost of Mitigation
(3 Alternatives)
Select and Develop
Recommended
Alternative
(1 Alternative)
ALTERNATIVE OPERATIONS PCE TREATMENT
EMERGENCY
WATER SUPPLY
1 - Base
TKWC and LBWC PWS Wells
to meet average annual demands
(2009 -2018).
Maintain current levels of VOC Treatment
(TKWC 2).
Operate LBWC 5 as lag well (starting in 2021).
STPUD
2 - Targeted
Pumping
Maximize PCE mass removal.
TKWC and LBWC PWS Wells
to meet average annual demands (2009 -2018).
Increase VOC Treatment.
Operate LBWC 5 as lead well
(starting in 2021).
Install new Replacement Well and Groundwater Treatment System to meet
Drinking Water Standards.
STPUD
3 – Source
Conversion from
Groundwater to
Surface Water
Over next 15 years –
Attain permits, negotiate agreements and
complete design/construction and testing of a new surface water treatment plant to meet 4.4
MGD MDD for TKWC and LBWC water
systems.
TKWC and LBWC PWS Wells to
meet average annual demands (2009 -2018).
Over Next 15 years-
Maintain current levels of VOC Treatment
(TKWC 2).
Operate LBWC 5 as lag well (starting in 2021).
STPUD
REMEDIAL ALTERNATIVES
1/2/2020
3
Alternatives Evaluation –
Summary of Costs (Jan 2020)
Alt 1. Base
Alt 2: Targeted Pumping (revised September 2019)Alt. 3:
Conversion to
Surface Water
Option 1:
Potable
Re-use
Option 2:
To Waste
(STPUD)
Option 3:
To Waste
(STPUD;CSLT)
Capital $0
(no change)$5.1M $3.1 M $3.2 M $57.6 M
O&M
(20 Years)
$0
(no change)$6.0 M $17.0 M $10.4 M
$7.9 M
(15 Years)
Total NPV
(2019$s)$0 $11.1 M 20.1 M $13.6 M $65.5 M
Time to
Implement
(years)
Current
3- 7
(planning, permitting, design/engineering,
construction and testing)
10 – 15
(planning, permitting,
design/engineering,
construction and
testing)
Alt. 1:
Base
Alt 2: Targeted Pumping (revised September 2019)Alt. 3:
Conversion to
Surface Water Option 1:
Potable
Re-use
Option 2:
To Waste
(STPUD)
Option 3:
To Waste
(STPUD;CSLT)
PCE Removed
over 20 years Lbs.278 - 1760 773- 3293 773- 3293
232 – 1418
(15 years)
Clean-Up Time
PCE < 4 µg/L 27 yrs. 18 yrs.
18 yrs.> 15 yrs.
(Total Capital +
O&M)/Water
Produced $/MG 0 $1,695 $5,599 $3,805 $23,176
Alternatives Evaluation-
PCE Removal
1/2/2020
4
Ownership
Long-Term O&M
Excess Water/ Purchase Water Agreement
Alternative 2, Option 1
2019 Regional Plume
Characterization
Objectives
Estimate lateral and
vertical extent of PCE
contamination
Identify contaminant
pathways
Provide detailed 3-d
“snapshot” view of Plume
1/2/2020
5