RE_ South Y Feasibility Study TAC Meeting 4 Follow-UP Action Items (Item 3 RAO)From:Ivo Bergsohn
To:"Sachi Itagaki"
Cc:Jennifer Lau
Subject:RE: South Y Feasibility Study TAC Meeting 4 Follow-UP Action Items (Item 3 RAO)
Date:Friday, March 01, 2019 8:38:47 AM
Hi Sachi-
Thought on the use of the RAO Objectives as Alternative Scenario Evaluation Criteria.
Can the RAO Objectives be weighted in terms of importance? This might help in providing more
meaning to the scoring of Alternatives.
If this is how KJC intends to proceed with this evaluation, I’m on the same page.
Thanks,
-Ivo
From: Ivo Bergsohn Sent: Friday, March 01, 2019 8:22 AMTo: 'Sachi Itagaki'Cc: 'Greg Pohll'; 'Susan Rybarski'Subject: RE: South Y Feasibility Study TAC Meeting 4 Follow-UP Action Items (West Side ReplacementWell)
Hi Sachi/Greg-
Please consider adding another Scenario for modeling/FS evaluation that would entail building on
Scenario 5 and proposed Scenario 6. This would involve adding a Replacement Well situated on the
west side of the South Y Plume. The purpose of this scenario would be to compare and contrast the
hydraulic effect of a Replacement Well sited on either side of South Y Plume. I would suggest this
analysis be performed in conjunction with TKWC 2 and LBWC 5 pumping at 90% Treatment Capacity
(Scenario 5A/5B); and with TKWC 2 and LBWC 5 pumping at 90% Source Capacity (Scenario 6A/6B).
Results of this evaluation could then lead to a recommendation for the preferred siting of a future
Replacement Well with respect to the South Y Plume.
Let me know your thoughts on this suggestion and whether it could be completed without a
significant change to the Project Budget/Schedule.
Thanks,
Ivo Bergsohn, PG, HG
Hydrogeologist
South Tahoe Public Utility District
1275 Meadow Crest Drive
South Lake Tahoe, CA 96150
(530)543-6204
From: Ivo Bergsohn Sent: Wednesday, February 27, 2019 10:44 AMTo: Sachi ItagakiCc: Greg Pohll; Susan RybarskiSubject: South Y Feasibility Study TAC Meeting 4 Follow-UP Action Items
Hi All-
Thanks for your efforts in developing and presenting the Modeling Evaluation and Feasibility Study
materials during yesterday’s TAC Meeting 4; Overall, I thought it went very well and led to some very
interesting and productive discussions, generally all positive. In follow-up to the meeting, here are
my takeaways, with regard to follow-up items;
1. LBWC #4 Well Site (KJC): Is a Replacement Well (RW) a worthwhile Alternative to
evaluate for the LBWC #4 well site?
i. To prevent the RW from serving as a potential vertical conduit for PCE
contamination and to mitigate potential contamination into the well; a
Surface Casing would likely need to be included for well construction tied
into the “Clay Lens” occurring at a depth of about 100 feet below ground
surface (ft bgs); or an inferred lower aquitard at a depth of about 160 ft bgs.
In this case targets for water production would include PCE contaminant free
water-bearing zones below about 175 feet bgs.
ii. In order for the TAC to help better consider this Alternative, KJC will
develop a PROS/CONs table generally considering potential Permitting Issues
(97-005 Process); possible benefit for remediation/containment on the
South “Y” PCE Plume; possible need for Well-Head Treatment; and costs
(Capital and O&M).
2. Scenario 6A/6B (KJC/DRI): Pumping TKWC-2 and LBWC-5 at 90% Source Capacity;
“Excess Treated Water” delivered to District main water distribution system.
i. Source Capacities: TKWC2 = 1800 gpm; LBWC 5 = 720 gpm
ii. KJC to determine “Excess Treated Water” delivered to District water
distribution system. Corresponding reductions in water production from
District wells in the Stateline Zone, to be performed using same method as
was used for determining Scenario 5 Pumping Rates. Pumping Rates for
Scenario 6 will be provided by KJC to DRI for evaluation using the South Y
PCE Model.
3. RAO Objectives (KJC)
i. KJC will develop a matrix showing the RAOs satisfied by each Alternative
evaluated for the Feasibility Study.
4. Feasibility Study Outline (KJC)
i. KJC will add a heading to Section 3 for a discussion of data gaps identified
during the project
ii. KJC will add a heading to Section 10 for a discussion of local permitting
needs for the evaluated alternatives
5. Public Workshop 4 (KJC/DRI/STPUD) – see attached draft Agenda
i. KJC will look into availability of Alice Robinson to address potential
questions of risk from delivering “Excess Treated Water” to the District’s
main water distribution system.
ii. STPUD will provide slides with exception of Item 5 – GW Model
Alternatives Evaluation to DRI by this Friday
iii. DRI to provide slides for Item 5 presentation.
6. Presentation Slides (KJC/DRI)
i. Review slides for any corrections identified during TAC Meeting 4
ii. KJC provide a full set of corrected slides for attachment to the Meeting
Minutes
iii. DRI provide a full set of corrected slides for attachment to the Meeting
Minutes
Let me know if you see any items that I may have missed; or wish to further discuss any of these
items.
Regards,
Ivo Bergsohn, PG, HG
Hydrogeologist
South Tahoe Public Utility District
1275 Meadow Crest Drive
South Lake Tahoe, CA 96150
(530)543-6204