STPUD Item 11.2 Groundwater F Modeling Report Alternative 21
Marla Sharp
From:Ivo Bergsohn
Sent:Friday, July 26, 2019 9:06 AM
To:'Carter, Tricia@Waterboards'
Cc:John Thiel; Jennifer Lukins (jennifer@lukinswater.com); Kirk Wooldridge
(kwooldridge@tahoekeyspoa.org); Sachi Itagaki
Subject:RE: STPUD (Agrmt No. D1712508) - Item 11.2 Groundwater F&Transport Modeling
Report - Alternative 2 Need for Modification
Hi Tricia‐
Thanks for your time yesterday afternoon which we discussed the need to modify Alternative 2 – Targeted Pumping as
part of the South Y Feasibility Study.
A copy of the letter received this week from the Tahoe Keys Property Owners Association (TKPOA) describes their
position with regard to the proposed use of Tahoe Keys Water Company (TKWC) Wells as part of an interim remedial
alternative (attached). In response to this letter, TKWC Well No. 2 will be removed from Alternative 2 and replaced using
extraction well (s) to provide the hydraulic control and removal of PCE from groundwater previously provided by TKWC
No. 2. The project team is currently reviewing data from the Lahontan Regional Water Quality Control Board Regional
Plume Characterization to help site and design these wells in terms of appropriate screen intervals and well depths. We
will also reconsider possible use of the Lukins Brothers Water Company (LBWC) Well No. 4 site as a possible extraction
well location. The project teams short‐term goal is to develop modifications to Alternative 2 to a level that could be
evaluated using the South Y Fate & Transport Model by the end of next week. I’ll follow‐up with an update as this work
progresses.
The modeling evaluation work already completed for this project and documented in the recently submitted Fate &
Transport Modeling Report (DRI, June 28, 2019) underscores the importance of operating LBWC Well No. 5 for hydraulic
control and removal of PCE from groundwater in the South Y Area. With the removal of TKWC wells from Alternative 2,
the importance of well head treatment for LBWC No. 5 is only increased to make Alternative 2 viable.
Feel free to contact me should you have any questions or immediate concerns with the direction that we are taking to
conduct the Feasibility Study.
Thanks,
Ivo Bergsohn, PG, HG
Hydrogeologist
South Tahoe Public Utility District
1275 Meadow Crest Drive
South Lake Tahoe, CA 96150
(530)543‐6204
From: Carter, Tricia@Waterboards [mailto:Tricia.Carter@Waterboards.ca.gov]
Sent: Thursday, July 25, 2019 4:45 PM
To: Ivo Bergsohn
Subject: RE: STPUD (Agrmt No. D1712508) - Item 11.2 Groundwater F&Transport Modeling Report
2
Hi Ivo,
Let me know if you are able to share the comment letter we discussed. It will help facilitate my discussion with Robert
tomorrow and provide emphasis on the need to expedite the funding for the SRF project.
Thanks,
Tricia
From: Carter, Tricia@Waterboards
Sent: Thursday, July 25, 2019 3:52 PM
To: Ivo Bergsohn <Ibergsohn@stpud.dst.ca.us>
Subject: RE: STPUD (Agrmt No. D1712508) ‐ Item 11.2 Groundwater F&Transport Modeling Report
Sounds good.
From: Ivo Bergsohn <Ibergsohn@stpud.dst.ca.us>
Sent: Thursday, July 25, 2019 3:50 PM
To: Carter, Tricia@Waterboards <Tricia.Carter@Waterboards.ca.gov>
Subject: RE: STPUD (Agrmt No. D1712508) ‐ Item 11.2 Groundwater F&Transport Modeling Report
Ok, I’ll try for around 4:15
Talk with ya soon,
‐Ivo
From: Carter, Tricia@Waterboards [mailto:Tricia.Carter@Waterboards.ca.gov]
Sent: Thursday, July 25, 2019 3:49 PM
To: Ivo Bergsohn
Subject: RE: STPUD (Agrmt No. D1712508) - Item 11.2 Groundwater F&Transport Modeling Report
You bet.
From: Ivo Bergsohn <Ibergsohn@stpud.dst.ca.us>
Sent: Thursday, July 25, 2019 3:44 PM
To: Carter, Tricia@Waterboards <Tricia.Carter@Waterboards.ca.gov>
Subject: RE: STPUD (Agrmt No. D1712508) ‐ Item 11.2 Groundwater F&Transport Modeling Report
Hi Tricia‐
Can I give you a call later this afternoon?
‐Ivo
From: Carter, Tricia@Waterboards [mailto:Tricia.Carter@Waterboards.ca.gov]
Sent: Thursday, July 25, 2019 3:05 PM
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To: Ivo Bergsohn
Cc: Susan Rybarski; Sachi Itagaki; Mark B. Hausner
Subject: RE: STPUD (Agrmt No. D1712508) - Item 11.2 Groundwater F&Transport Modeling Report
Hi Ivo,
Any updates?
Tricia
From: Ivo Bergsohn <Ibergsohn@stpud.dst.ca.us>
Sent: Tuesday, July 16, 2019 8:55 AM
To: Carter, Tricia@Waterboards <Tricia.Carter@Waterboards.ca.gov>
Cc: Susan Rybarski <Susan.Rybarski@dri.edu>; Sachi Itagaki <SachiItagaki@kennedyjenks.com>; Mark B. Hausner
<Mark.Hausner@dri.edu>
Subject: RE: STPUD (Agrmt No. D1712508) ‐ Item 11.2 Groundwater F&Transport Modeling Report
Hi Tricia‐
We are currently waiting to hear the direction TKPOA Board has given staff concerning their continued level of
participation as part of the recommended remedial alternative. This is anticipated at their next Board Meeting
scheduled for this Saturday (7/20).
In case TKPOA plans to withdraw from the FS we are considering a Scenario 2b. Scenario 2b would involve adding a cost
item for the drilling and construction of a replacement extraction well, wellhead treatment system and discharge. The
extraction well would be placed near the centerline of the plume, upgradient of TKWC2 and designed to pump
groundwater from Model Layer 2 (TKZ4); approximately 130 – 200 ft bgs. The well would be designed as a production
well (at 550 gpm) with a wellhead treatment system for the removal of PCE from groundwater. Discharge options for
this well would include potable reuse (connection to LBWC water distribution system); and/or surface water discharge
under a NPDES permit.
I believe that the work DRI performed under Alternative 4 may be adequate to estimate the contaminant mass removal
for the replacement extraction well proposed under Scenario 2b. We’ll need to check on this with DRI after we hear back
from TKPOA and depending on the proposed location of the replacement extraction well.
DRI is working on an addendum to address the comment concerning a Table of Data Sources used for the groundwater
modeling.
Let me know if you want to talk further about this or if you have any other questions about the FS.
Thanks,
Ivo Bergsohn, PG, HG
Hydrogeologist
South Tahoe Public Utility District
1275 Meadow Crest Drive
South Lake Tahoe, CA 96150
(530)543‐6204
4
From: Carter, Tricia@Waterboards [mailto:Tricia.Carter@Waterboards.ca.gov]
Sent: Monday, July 15, 2019 3:03 PM
To: Ivo Bergsohn
Cc: Susan Rybarski; Sachi Itagaki; Mark B. Hausner
Subject: RE: STPUD (Agrmt No. D1712508) - Item 11.2 Groundwater F&Transport Modeling Report
Hi Ivo,
In addition to my comment below, can you confirm how you intend to address Tahoe Keys concern of their wells being
included as part of the remedy. Do you intend to run another scenario with the model that does not include the Tahoe
Key’s wells, but accounts for their pumping influence to meet the demand of their customers?
Thanks again,
Tricia
From: Carter, Tricia@Waterboards
Sent: Tuesday, July 09, 2019 12:57 PM
To: Mark B. Hausner <Mark.Hausner@dri.edu>; Ivo Bergsohn <Ibergsohn@stpud.dst.ca.us>
Cc: Susan Rybarski <Susan.Rybarski@dri.edu>; Sachi Itagaki <SachiItagaki@kennedyjenks.com>
Subject: RE: STPUD (Agrmt No. D1712508) ‐ Item 11.2 Groundwater F&Transport Modeling Report
Hi Ivo,
Can you confirm how the first bullet was addressed?
I see the bullets 2‐4 were addressed in the final document.
Thanks for taking the time to put the comments together,
Tricia
From: Mark B. Hausner <Mark.Hausner@dri.edu>
Sent: Tuesday, July 02, 2019 9:58 AM
To: Ivo Bergsohn <Ibergsohn@stpud.dst.ca.us>; Carter, Tricia@Waterboards <Tricia.Carter@Waterboards.ca.gov>
Cc: Susan Rybarski <Susan.Rybarski@dri.edu>; Sachi Itagaki <SachiItagaki@kennedyjenks.com>
Subject: RE: STPUD (Agrmt No. D1712508) ‐ Item 11.2 Groundwater F&Transport Modeling Report
Hi Ivo and Tricia:
Below is a list of verbal comments conveyed to us during the TAC meeting that were incorporated into the final report:
Add a table of data sources used to calibrate the model, being sure to include data generated as part of the pre‐
design investigation
Expand the discussion of spatial and temporal data gaps and how future data could be collected to most
effectively reduce model uncertainty
Add a note to scenarios when and if the simulated concentrations or pumping rates exceed the nominal GAC
capacity (this was requested by LBWC, and we added the note for both LBWC and TKWC)
Add language from STPUD’s attorney to limitations section to address potential liability issues for the District
and DRI.
We also received written comments from Ivo and Gary at the district that we incorporated into the final document.
It was noted during the meeting that effective limitations on pumping were determined by the permit issued and not by
the well capacity, and Salvador Turrubiartes reiterated that in his written comments following the meeting. Ivo provided
us with a copy of Mr. Turrubiartes’ comments, and we kept those comments in mind during the revision. We considered
5
the specific comments outside of the scope of the modeling report, since the simulated scenarios were provided to us by
the stakeholders in the feasibility study.
Please feel free to contact me with any other questions, or if any of the comments or responses remain unclear. Thanks,
Mark
Mark B. Hausner, Ph.D.
Assistant Research Professor, Hydrology
Division of Hydrologic Sciences
Desert Research Institute
775‐673‐7352
mark.hausner@dri.edu
From: Ivo Bergsohn <Ibergsohn@stpud.dst.ca.us>
Sent: Tuesday, July 2, 2019 9:12 AM
To: 'Carter, Tricia@Waterboards' <Tricia.Carter@Waterboards.ca.gov>
Cc: Susan Rybarski <Susan.Rybarski@dri.edu>; Mark B. Hausner <Mark.Hausner@dri.edu>; Sachi Itagaki
<SachiItagaki@kennedyjenks.com>
Subject: RE: South Y Feasibility Study (Agreement No. D1712508) ‐ Item 11.2 Groundwater Fate and Transport Modeling
Report
Hi Tricia‐
Written comments were received from Salvador Turrubiartes (SWRCB‐DDW). I have asked DRI to provide a list of the
verbal comments they noted from the TAC during TAC Meeting 5. The meeting minutes from TAC 5 still need to be
prepared.
No comments were received from B. Grey, LRWQCB.
Comments received from TKPOA (see attached email strings)
Use of semi‐annual vs. annual time‐steps;
Request for Modeling Reports referenced in F& T Report
Outside of the review comments which I provided during development of the F&T Report, I believe that’s it,
Ivo Bergsohn, PG, HG
Hydrogeologist
South Tahoe Public Utility District
1275 Meadow Crest Drive
South Lake Tahoe, CA 96150
(530)543‐6204
6
From: Carter, Tricia@Waterboards [mailto:Tricia.Carter@Waterboards.ca.gov]
Sent: Monday, July 01, 2019 2:55 PM
To: Ivo Bergsohn
Cc: Susan Rybarski; Mark B. Hausner (Mark.Hausner@dri.edu); Sachi Itagaki
Subject: RE: South Y Feasibility Study (Agreement No. D1712508) - Item 11.2 Groundwater Fate and Transport
Modeling Report
Hi Ivo,
Do you have record of all TAC comments and documentation of the responses? (e.g., I recall the data gap discussion
from our TAC meeting that DFA and RB noted. Also, reference to information obtained in the pre‐design investigation
and how it was used to inform the model was also a DFA comment). Did the Regional Board and Tahoe Keys provide any
additional comments?
Thanks,
Tricia
From: Ivo Bergsohn <Ibergsohn@stpud.dst.ca.us>
Sent: Friday, June 28, 2019 10:47 AM
To: Carter, Tricia@Waterboards <Tricia.Carter@Waterboards.ca.gov>
Cc: Susan Rybarski <Susan.Rybarski@dri.edu>; Mark B. Hausner (Mark.Hausner@dri.edu) <Mark.Hausner@dri.edu>;
Sachi Itagaki <SachiItagaki@kennedyjenks.com>
Subject: South Y Feasibility Study (Agreement No. D1712508) ‐ Item 11.2 Groundwater Fate and Transport Modeling
Report
Hi Tricia‐
I am pleased to provide electronic copy of the Fate and Transport Modeling of the South Y PCE Groundwater
Contamination Plume . This report was prepared by the Desert Research Institute (DRI) for the Feasibility Study of
Remedial Alternatives to Mitigate Tetrachloroethylene Contamination, Agreement No. D1712508, and is submitted for
your approval in accordance with Scope of Work Item 11.2 of the Agreement. Any comments received from the TAC
have been addressed in this report.
Upon your approval the attached report will be uploaded to FAAST.
Thanks again for your kind assistance throughout this project,
Ivo Bergsohn, PG, HG
Hydrogeologist
South Tahoe Public Utility District
1275 Meadow Crest Drive
South Lake Tahoe, CA 96150
(530)543‐6204
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