Meeting Notes_17W006_ TAC Proj Mtng 5_20190621_finalAGENDA
SOUTH TAHOE PUBLIC UTILITY DISTRICT
TAC Meeting 5
South YFeasibility Study of Remedial Alternatives(D1712508-1)
Friday, June 21, 2019 10:00 AM- 2:00 PM
Go To Meeting Conference Call
Call-In Number: +1 (872) 240-3311; Access Code: 217-469-869
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5_20190621_final.docx 1
Attendees: see Sign-In Sheet (TAC Meeting 5, 6/21/2019). Ivo Bergsohn (IB); Mark
Hausner (MH); Susan Rybarski (SR); Jennifer Lukins (JL_LBWC); Andy Kopania (AK);
Salvador Turrubiartes (ST); Brian Grey (BG); Julie Ryan (JR); Tricia Carter (TC); Jason Burke (JB); Chris Spellman (CS); Sachi Itagaki (SI); Jennifer Lau (JL-KJC); Robert
Reeves (RR); Kathryn Dominic(KD); Gary Kvistad (GK)
1) Welcome/Self Introductions 10:00
Updated TAC Roster/ Dave Peterson new TKWC Water System Manager, is replacing Rick Robillard on the TAC.
2) FS Screening/Interim Remedial Alternatives (KJC) 10:10
JL-KJC provided a Presentation describing the development of the Interim
Remedial Alternatives (IRAs). The presentation included an overview of the
scenarios; a recap of the preliminary alternatives screening; alternatives presented
to water agencies for their respective Board’s input; and an overview of the three
IRAs (Base Treatment- Alt. 1; Targeted Pumping – Alt 2; and Conversion to SW Supply- Alt3) selected for further analysis through the feasibility study process. Base
treatment would not require any new permitting or increases in costs. Disadvantages
– DRI model shows plume may persist for more than 20 years; Alt 1 would not
speed-up mass removal, leaves risk for additional wellhead treatment in future,
accruing additional costs; and spreading of plume to LBWC 1, TKWC 3 and TKWC 1. Alt 2 wells with GAC treatment operated in lead to meet each water systems
demand; no new permitting required; would need to upsize water system pipelines;
added costs for higher O&M due to more frequent GAC change-outs. Benefits
include increase/optimizes PCE mass removal; may be protective of TKWC 1;
treated water used for potable re-use. Disadvantages include: added costs; increased operational complexity; and possible need for secondary option to
discharge treated water. Alt 3- Surface Water Conversion – gradual conversion may
require 15 years for planning, permitting, construction, during interim operate as Alt.
1. Full implementation surface water replaces all groundwater supplies for LBWC
and TKPOA systems; LBWC 1 and TKWC 3 could be used as possible back-up supplies; new permitting for surface water treatment plant; discharge permit for
disposal, if needed; added costs for new infrastructure, water intake, pipelines,
pumping stations, treatment storage and disposal, well destruction costs; added
treatment and O&M costs. Benefit – switch to PCE water supply; opportunity for
shared costs between water purveyors. Disadvantages: limited PCE mass removal; reliance on STPUD for future water supply; probable highest cost alternative. Other
activities were also identified and recommended as potential future work. These
AGENDA
SOUTH TAHOE PUBLIC UTILITY DISTRICT
TAC Meeting 5
South YFeasibility Study of Remedial Alternatives(D1712508-1)
Friday, June 21, 2019 10:00 AM- 2:00 PM
Go To Meeting Conference Call
Call-In Number: +1 (872) 240-3311; Access Code: 217-469-869
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5_20190621_final.docx 2
included LBWC 4 Well Destruction; TKWC 2 Vertical profiling; Construct sentinel wells; Private well survey; expedited investigation and remedial action at PCE
source areas.
Discussion AK clarified that alternatives have not been vetted by TKPOA Board or evaluated by
staff; Staff is currently preparing review comments on the draft DRI F&T Modeling
Report; no decisions have been made by Board.
RR what alternatives were brought to LBWC and STPUD Boards for review? IB - both the four alternatives identified as part of the preliminary screening and the three
IRAs selected for further development were presented and described to the District
Board at the May 2nd meeting. DRI performed additional modeling to evaluate the
three IRAs to be presented later this meeting. RR- were the additional model runs performed for the additional alternatives
requested by the stakeholders?; IB- right; following the February TAC, KJC met
individually with LBWC, TKPOA and STPUD to discuss the preliminary screening of
the Alternatives; receive input from the water agencies; and select a final three alternatives for continued analysis through the feasibility study process (March/April). During phone call, agencies reached consensus on the final three
alternatives (presented to STPUD Board); subsequent to that District requested that
DRI conduct additional modeling on the final three alternatives to be presented later
this meeting. RR- difference in O&M costs between Alt 1 &2? SI- KJC is working on this; clean-up
times for Alt 2? SI- will be presented by DRI in next presentation.
TC – please confirm that Alt 2 uses existing GAC; SI correct, existing treatment at TKWC 2 and planned treatment at LBWC 5 to meet water system demands. No excess treated water is delivered to STPUD water system.
RR- Will LBWC 1 and TKWC 3 still be protected by Alt 2 Targeted Pumping
Scenario, even when pumping less? SR- only one conservative scenario showed trace levels of PCE in the modeling runs, will be shown in the following presentation.
ST- Alt 2- Can LBWC 5 provide the same level of water production as LBWC 1? Can
TKWC 2 provide the same level of water production as TKWC 3? IB- yes, but the
cost of treated water will be higher.
AGENDA
SOUTH TAHOE PUBLIC UTILITY DISTRICT
TAC Meeting 5
South YFeasibility Study of Remedial Alternatives(D1712508-1)
Friday, June 21, 2019 10:00 AM- 2:00 PM
Go To Meeting Conference Call
Call-In Number: +1 (872) 240-3311; Access Code: 217-469-869
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5_20190621_final.docx 3
3) F&T Report – Draft (DRI) 10:40
SR provided a presentation discussing PCE Model Recalibration and Final
Alternatives Modeling Results. At the end of the presentation, DRI fielded questions from the TAC concerning the draft F&T Modeling Report.
PCE Model Recalibration
Recalibration did not substantially affect the model results. Biggest change for recalibration was adjustments made to the screen interval at LBWC 4; screen elevation was corrected; the well screen was in the correct layers; however the
screen interval proportions within each layer needed adjustment. As model was
being recalibrated an expanded clay lens was added to the model, based on
subsurface correlations provided by IB. Additional minor tweaks were also made; longitudinal dispersivity decreased from 50m to 40m;transverse dispersivity ratio increased from 0.5 to 0.6 in layers 1 and 2; decay half-life increased from 15 to 17
years in layer 1. Big change- recharge concentration at source term decreased by
30% during years LTLW was in operation.
TC- Was any of the Pre-Design Investigation (PDI) data incorporated into the model? SR- Yes the hydraulic conductivities from the PDI were used in the model.
SR showed the expanded clay lens as depicted in the model; IB presented a set of
slides showing the subsurface correlations supporting incorporation of the expanded clay lens into the model.
Recalibration Results
SR presented PCE breakthrough curves comparing simulated versus observed concentrations to show results of the model recalibration. Clement Well – not capturing the concentration peak, but are getting the timing of the contaminant
increase right-on. Rockwater Well and LBWC 4 only a few recent observed
concentrations, difficult for comparison. Wells further north; TKWC 1, LBWC 5 and
TKWC 2, correlations between simulated and observed concentrations are better. Recalibrated model is showing higher PCE concentrations in layer 2 than before; allowing more PCE to migrate into layer 2 improved the model. Much less PCE in
layer 3 and almost nothing in layer 4.
Final Alternatives Modeling
AGENDA
SOUTH TAHOE PUBLIC UTILITY DISTRICT
TAC Meeting 5
South YFeasibility Study of Remedial Alternatives(D1712508-1)
Friday, June 21, 2019 10:00 AM- 2:00 PM
Go To Meeting Conference Call
Call-In Number: +1 (872) 240-3311; Access Code: 217-469-869
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5_20190621_final.docx 4
Alternatives 1, 2 and 3; simulations for each alternative were run under baseline
(standard simulation – “A” scenarios) and conservative (constant source release
with a10 mg/L recharge concentration; and no biogenic decay -“B” scenarios) model
conditions. Alternatives 1 and 2 simulations were run for 50 years; Alternative 3 simulations were run for 15 years to represent pumping during transition to a surface water source. Results from the max pumping scenarios from the preliminary
alternatives were also provided as these were already simulated, if interested in
these test results. Model is a planning tool to compare results between each
Alternative. Because of uncertainties in the available data, a book-end analysis approach using standard and conservative model runs was used to constrain the range of predicted PCE concentrations. It is not intended to accurately predict
specific future concentrations.
Alternative 1A Baseline simulated PCE concentrations at TKWC 1, LBWC 5 and TKWC 2 through 2068. TKWC 1 - PCE below MCL over simulation period. LBWC 5 and TKWC 2 – Currently near peak PCE concentrations in these wells, PCE is
predicted to decline from these levels into future. At 2068, most of PCE mass
extracted from Layer 2 (146 kg); PCE mass migrated north of model domain into
Lake Tahoe. Alternative 1B Conservative simulated PCE concentrations at TKWC 1, LBWC 5 and
TKWC 2 through 2068. Much higher PCE compared to baseline simulation, but
follow same general trends. TKWC 1 - PCE above MCL over simulation period; peak
concentrations predicted around 2040. LBWC 5 and TKWC 2 – Currently near peak PCE concentrations in these wells, PCE is predicted to decline but remain above MCLs into future. At 2068, most of PCE mass extracted from Layer 2 (906 kg); High
PCE (>50 µg/L) remains in Tahoe Keys area; PCE Mass is getting pulled into TKWC
3, breakthrough curve shows trace levels approaching method detection limit (0.5
µg/L). PCE above MCLs in Layers 3 and 4; no mass extracted from layer 4 as no wells screened through this model layer.
Alternative 2A Targeted Pumping simulated PCE concentrations at TKWC 1, LBWC
5 and TKWC 2 through 2068, compared to Alternative 1A Baseline. At TKWC 1,
LBWC 5 and TKWC 2 showing lower PCE concentrations compared to Baseline. LBWC 5 and TKWC 2 are retarding plume migration toward TKWC 1. At 2068, most of PCE mass extracted from Layer 2 (238 kg).
Alternative 2B Targeted Pumping – Conservative simulated PCE concentrations at
TKWC 1, LBWC 5 and TKWC 2 through 2068, compared to Alternatives 2A and 1B
AGENDA
SOUTH TAHOE PUBLIC UTILITY DISTRICT
TAC Meeting 5
South YFeasibility Study of Remedial Alternatives(D1712508-1)
Friday, June 21, 2019 10:00 AM- 2:00 PM
Go To Meeting Conference Call
Call-In Number: +1 (872) 240-3311; Access Code: 217-469-869
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5_20190621_final.docx 5
Conservative. At TKWC 1, LBWC 5 and TKWC 2 showing lower PCE concentrations compared to Alternative 1B Conservative. LBWC 5 and TKWC 2 are retarding plume
migration toward TKWC 1. At 2068, most of PCE mass extracted from Layer 2 (1314
kg). PCE is Layers 3 and 4 similar as what were seen in 1B Conservative.
Alternative 3A SW Conversion simulated PCE concentrations at TKWC 1, LBWC 5 and TKWC 2 through 2033. As simulation is only run for 15 years, no direct
comparison to other scenario results. Curves are exactly the same for 1A Baseline
through 2033. At 2033, PCE approaches MCL at TKWC 1; PCE concentrations
declining, but remain above MCLs in LBWC 5 and TKWC 2. At 2033, most of PCE mass extracted from Layer 2 (100 kg); with shorter simulation run; plume has not fully migrated down-gradient. PCE in Layer 3 is below MCLs. SI pointed out that the
model results show that the majority of mass removal is occurring over the first 15
years (about 68%).
Alternative 3B SW Conversion – Conservative simulated PCE concentrations at TKWC 1, LBWC 5 and TKWC 2 through 2033. Curves are exactly the same for 1B
Conservative through 2033. At 2033, PCE approaches 50 µg/L at TKWC 1; PCE
concentrations declining, but remain above 40 µg/L in LBWC 5 and above 60 µg/L in
TKWC 2. At 2033, most of PCE mass extracted from Layer 2 (512 kg); PCE concentrations at TKWC 3 range between 0.5 to 1.0 µg/L.
Other Results – not being considered further in Feasibility Study
Alternative 4: 90% GAC Capacity simulated PCE concentrations at TKWC 1, LBWC 5 and TKWC 2 through 2068, compared to Alternative 1A Baseline. At TKWC 1 observe a marked decrease in PCE concentrations – “Protective Effect”. At LBWC 5
and TKWC 2 showing PCE concentrations declining more rapidly, as more mass is
being removed, compared to 1A Baseline. At 2068, most of PCE mass extracted
from Layer 2 (463 kg); PCE plume is a lot smaller in extent and has not reached as far north toward Lake Tahoe. No PCE mass in Layers 3 and 4.
Alternative 5: 90% Well Capacity – TKWC 2 pumping at 1800 gpm, would require
expanded GAC Treatment System. Under Alternative 5 simulated PCE
concentrations at TKWC 1, LBWC 5 and TKWC 2 through 2068, compared to Alternative 1A Baseline. As in Alternative 4, observe even more marked decrease in PCE concentrations at TKWC 1. At LBWC 5 and TKWC 2 showing PCE
concentrations declining even more rapidly, as more mass is being removed,
compared to 1A Baseline. Under Alternative 5 achieving more PCE mass removal
and more rapid clean-up compared to all other alternatives.
AGENDA
SOUTH TAHOE PUBLIC UTILITY DISTRICT
TAC Meeting 5
South YFeasibility Study of Remedial Alternatives(D1712508-1)
Friday, June 21, 2019 10:00 AM- 2:00 PM
Go To Meeting Conference Call
Call-In Number: +1 (872) 240-3311; Access Code: 217-469-869
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5_20190621_final.docx 6
Mass Extracted by Well Comparison (bar graph), under base scenario – Alternative
2A removes most mass of the three remaining alternatives selected for further
evaluation through the Feasibility Study.
Years to Clean-Up (<4 µg/L) Comparison (bar graph): As only run for 15 years, Alternative 3 not shown.
Discussion
AK pointed out that comparison of Alternative 1 and 2 shows the greatest increase in PCE mass removal occurs at LBWC 5; mass removal at TKWC 2 is relatively
unchanged. This also shows importance of GAC treatment at LBWC 5 as part of the
clean-up effort suggested under Alternative 2.
AK recommended water company operations – how to present this to TKPOA Board – Concerns about model recalibration results; Concentrations in TKWC 2 and LBWC
5 appear to be increasing exponentially which is not reflected in the model;
Operationally have concerns about model to predict future concentrations; simulated
concentrations at LBWC 4 is not supported by observe concentrations – “shows plume where it isn’t” ; concerns about model will not help TKPOA Board’s confidence in the modeling evaluation or how these results will help TKPOA plan
future well operations. What is the best way to help explain these discrepancies to
TKPOA Board? SR- there is a lot of uncertainties in model; large data gaps both
spatially and temporally; which is why book-end approach was used. Standard simulation has a higher chance of occurring; conservative is an extreme worst-case scenario. Main goal was not to predict specific concentrations, but use the model to
compare alternatives and identify what is most effective in terms of groundwater
clean-up.
AK – Water purveyors should not be responsible for groundwater clean-up. As such, TKPOA is concerned about taking on added treatment costs as part of Alternative 2.
If grant funds were available to TKPOA to off-set these added costs, TKPOA may be
more open to participating in implementation of Alternative 2. RR- Because of
possible differing match requirements part of outcome of FS should look at who is best party to apply for Round 3 implementation funding; STPUD or LBWC? If TKPOA could show that operation of the wells was part of the clean-up; TKPOA
could also possibly apply for this funding. Prop 68 funding – allocated for O&M of
existing water treatment systems. This funding may also be available to TKPOA if
moved to implementation as part of recommended alternative. AK- Would like to
AGENDA
SOUTH TAHOE PUBLIC UTILITY DISTRICT
TAC Meeting 5
South YFeasibility Study of Remedial Alternatives(D1712508-1)
Friday, June 21, 2019 10:00 AM- 2:00 PM
Go To Meeting Conference Call
Call-In Number: +1 (872) 240-3311; Access Code: 217-469-869
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5_20190621_final.docx 7
confirm whether TKPOA can qualify for any type of state funding. RR- will need follow-up with SRF; and status of LBWC application; suggest that LBWC and/or IB
attend upcoming Prop 68 workshop.
Draft F&T Report Comments AK- Staff is working on technical review comments. Will need to take toTKPOA
Board for discussion before providing comments.
ST- 90% Capacity for wells and treatment. DDW operational permits are based on treatment plant capacity. Water systems will be restricted to treatment capacity not well capacity.
ST – Surface water treatment, if surface water to be used for drinking water supply;
who will be responsible party maintaining system and what type of agreement will be between LBWC and TKPOA on how will treated water be allotted between water systems? How will conversion to SW affect their regional emergency response
program (response to wildfire)? Contingencies for interruptions to treatment and/or
water supply?
BG – Calibration and Data gaps – expanded discussion about data gaps would be helpful; are there any actions that could be taken to reduce model uncertainty ; in
terms of types of added data collection and/or locations?
TC- Highlight how data from PDI was used in the groundwater model. RR- Identify action items in Feasibility Study to be addressed as part of an
Implementation Project.
4) Feasibility Study (KJC) 12:00 JL-KJC provided a Presentation describing preliminary definition of infrastructure
needs identified for the three screened IRAs; cost elements identified in the
estimates of life-cycle costs and the environmental checklists that will be used as a
basis of a cost of mitigation for each Alternative. Infrastructure needs considerations include water demands to size piping and water treatment systems, water storage. With regards to sizing, system footprints to identify possible sites; tie-ins to existing
water distribution systems (set-points); and other new infrastructure needs including
possible pump stations; utility piping and structure/buildings.
AGENDA
SOUTH TAHOE PUBLIC UTILITY DISTRICT
TAC Meeting 5
South YFeasibility Study of Remedial Alternatives(D1712508-1)
Friday, June 21, 2019 10:00 AM- 2:00 PM
Go To Meeting Conference Call
Call-In Number: +1 (872) 240-3311; Access Code: 217-469-869
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TKPOA water system line work is drawn, not surveyed. Not appropriate for water system modeling. Analytical methods will be used to derive hydraulic flow estimates
used for pipe sizing in conceptual design presented in FS.
Modeled flows (pumping rates) vs. Water Demands used for piping and treatment system sizing. Using the available water production data used in the groundwater model, KJC applied Ca Waterworks Standard methods to estimate Average Daily
Demands (ADD), Max Day Demand (MDD) and Peak Hour Demand (PHD). Fire
flow not included in these calculations (assume fire flow provided through STPUD
inter-ties). Peaking Factors used in MDD and PHD estimates were default values (1.5) as per Ca Waterworks Standard methods.
Alternative 1 – no new infrastructure
Alternative 2 – new piping (upsize existing 8-inch pipe for TKWC 2 to 12-inch?); 12-
inch (?) piping at LBWC 5 appears adequate. (STPUD Piping unit cost ~ $300/lf) – IB to provide bid sheets for recent waterline projects completed by District for KJC use.
Alternative 3- Fresh water intake (Lake Tahoe); surface water treatment facility; new
pipelines; pump stations; utility piping/conduit; storage (?). Membrane treatment
selected for new TCPUD facility- will use costs for TCPUD facility and scale-up for Alt 3 cost-estimate. Storage will be based on evaluation of water demands and emergency use (power outage).
TC- What does permitting involve for a new water intake in Lake Tahoe? AK -Water
depth requirement for intake? SI, KJC – permit requirements are being identified.
AGENDA
SOUTH TAHOE PUBLIC UTILITY DISTRICT
TAC Meeting 5
South YFeasibility Study of Remedial Alternatives(D1712508-1)
Friday, June 21, 2019 10:00 AM- 2:00 PM
Go To Meeting Conference Call
Call-In Number: +1 (872) 240-3311; Access Code: 217-469-869
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5_20190621_final.docx 9
Life-Cycle Cost Elements
Alternative 1 (Existing Costs) –GAC Change-out; Chlorine Consumption; Energy
(pumping); Labor; Other O&M; Unit cost of water from STPUD.
Alternative 2 (Estimated Costs) –GAC Change-out; Chlorine Consumption; Energy (pumping); Labor; Other O&M; Unit cost of water from STPUD. Alternative 3 (Estimated Costs) – Permitting; Energy; Treatment; Labor;
Maintenance; Disposal; Additional O&M (consider adding cost for added water
quality monitoring required for surface water treatment systems)
JL-LBWC- How will KJC consider the design criteria used for GAC system planned for LBWC 5; 300 ppb/PCE at 700 gpm flow as part of the life-cycle cost for
Alternative 2?.JL, KJC response- Limitation would be identified as part of the Pros
vs Cons analysis for this alternative.
JL-LBWC-Should a cost share structure be identified for Alternative 3 within the FS? What would the cost of water be to LBWC under this Alternative. IB- Conceptual
cost of Alternative 3 may not be acceptable to water purveyors; added time/energy
needed to estimate possible cost of water to water system may not be necessary for
evaluation at a planning level. KJC provided a Request for Information to help KJC develop life-cycle costs for the
Feasibility Study. KJC needs to expedite request to TKWC, as D. Peterson (Water
System Manager) is leaving next week.
RR- LBWC should already have cost estimates for GAC system planned for LBWC 5- KJC should consider including these estimates in the Feasibility Study.
Initial Study Checklists- KJC using CEQA Initial Study and TRPA Initial
Environmental Checklists as a basis for estimating cost of mitigation for Alternative 3.
5) Request for Time Extension (IB/KJC) 13:00
IB informed TAC of recent Request for Time Extension (RTE) submitted to SWRCB-DFA. In May (5/10/2019) District submitted a RTE changing the Project Completion Date from June 30, 2019 to January 31, 2020; and walked through changes to
submittal dates for reports to be reviewed by TAC. TC requested that the updated
Pre-Design Investigation report be submitted to Grant Manager; does not need to go
to entire TAC, as draft has already been reviewed. RR requested that updated report
AGENDA
SOUTH TAHOE PUBLIC UTILITY DISTRICT
TAC Meeting 5
South YFeasibility Study of Remedial Alternatives(D1712508-1)
Friday, June 21, 2019 10:00 AM- 2:00 PM
Go To Meeting Conference Call
Call-In Number: +1 (872) 240-3311; Access Code: 217-469-869
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5_20190621_final.docx 10
include section identifying data gaps. TC- RTE is still under review by SWRCB-DOFA staff and at this time, has not been formally approved.
6) LRWQCB Update 13:20 SRWQCB-DFA requested time for LRWQCB to report on progress of SB 445
Investigation (s)
BG – provided a Presentation updating the TAC on the Source Area and Regional Plume Characterization (RPC) being conducted by the LRWQCB. Major focus: Source Area Investigations – identify remaining source areas of PCE contamination
within the South Y Area; RPC – complete SB445 scope of work.
Source Area Investigations: April 2019 – Information request letters sent to 223 parties that LRWQCB suspects may have used PCE at premises; Completed Questionnaires due May 2019. Thirty-three (33) Notice of Violations (NOVs) issued
June 2019 related to incomplete Questionnaires. Staff is continuing to review and
compile information gathered through letter requests.
Investigative Orders (13267 letters) issued to Big O Tire requiring a work plan and completed questionnaire due July 10, 2019. RFI related to Site History (prior to
1985), PCE in soils, preferential pathways, potential release areas. LRWQCB
considers Big O as potential source area. Similar letter with same due date also
issued to Hurzel Properties, LLC (961 Emerald Bay Road). Lake Tahoe Laundry Works (LTLW) –continuing to operate under their Clean-Up and
Abatement Order (CAO R6T-2017-0022). Tucker Pond – waiting for pond area to
dry-out in order to allow for passive soil gas sampling (potential source area?);
access agreement signed with J. Runnels. Passive soil gas sampling also planned for former Big O Tire property. On-going Step Out/Step Down Investigation on-hold until after Tucker Pond soil gas sampling is completed. Technical Meeting –
LRWQCB encouraging interim remedial action be undertaken by PRP on-site;
requested RAP by end of July.
SB445 Regional Plume Characterization (RPC) – Contract scope of work includes 80 CPT locations; 15 Sonic Boring locations; 800 GW Samples; and 100 soil
samples. Push is to get the field work for the RPC completed this field season. Other
work within SB445 Investigation scope include; Vertical Conduit Evaluation; Non-
Municipal (Private?) Water Supply Sampling; Soil Vapor Sampling; and Perimeter
AGENDA
SOUTH TAHOE PUBLIC UTILITY DISTRICT
TAC Meeting 5
South YFeasibility Study of Remedial Alternatives(D1712508-1)
Friday, June 21, 2019 10:00 AM- 2:00 PM
Go To Meeting Conference Call
Call-In Number: +1 (872) 240-3311; Access Code: 217-469-869
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5_20190621_final.docx 11
and Sentry Well Installations. Some of the assumptions used in the initial scope of work have changed; unknown as to work scope flexibility with regards to
incorporating findings from recent work. Source investigation tasks are pending
results of RPC. Sonic drilling started 6/17/2019; CPT rig arrives this coming Monday.
Anticipate weekly email updates showing progress of RPC. RPC is directed at providing a broad look at contaminant plume; LRWQCB believes information from RPC may be helpful in selecting appropriate alternatives for groundwater clean-up.
RPOC LRWQCB is open to receiving comments on proposed investigation approach
for RPC. CPT will be used to investigate subsurface to refusal (about 80 ft bgs).
Sonic to be used to extend investigation below 80-feet to max depth of 300 feet. IB suggested that LRWQCB pay close attention to 30-50 interval, as recent work from PDI suggests that this zone may serve as a preferential pathway for movement of
PCE groundwater contamination near the South Y.
Discussion RR- What are decision criteria to move out laterally beyond edge of proposed
sample grid? PCE concentrations > 5 ppb would provide justification to consider
stepping-out beyond the margins of the sample grid.
SI – Does sample grid represent current scope for SB 445 Investigation or what LRWQCB wishes for the scope of the proposed investigation? Grid reflects current
contract scope. KD, SWRCB- Scope within contract has fixed tasks; how each task
will be carried out is not fixed. Tasks may be changed in response to findings of
preceding tasks; approved scope allows for using as an iterative approach during the investigation.
SI- How will data be released to public; informally or will there be a formal release, if
so, any timeline? LRWQCB intending to use informal email update to keep parties
up-to-date. Final report will be completed after completion of the field activity. AK – TKWC Well No. 1 area- is there any potential for investigation work through
this area to help inform KJ work on feasibility study and/or DRI work on groundwater
model? Additional sonic boring locations are potentially available to help investigate
distal portions of the contaminant plume. KD - drilling of additional borings would be contingent on available remaining funds and competing project objectives.
RR- Are CPTs being done first or will CPT Borings will be performed concurrently
with the sonic borings? CPT Borings will be conducted concurrently with the sonic
borings to help build on preceding results. KD – site access agreements is a
AGENDA
SOUTH TAHOE PUBLIC UTILITY DISTRICT
TAC Meeting 5
South YFeasibility Study of Remedial Alternatives(D1712508-1)
Friday, June 21, 2019 10:00 AM- 2:00 PM
Go To Meeting Conference Call
Call-In Number: +1 (872) 240-3311; Access Code: 217-469-869
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5_20190621_final.docx 12
limitation.
AK- Who developed the terms of the access agreements; LRWQCB or AECOM?
Templates originated from AECOM. IB- District entered into access agreement with
AECOM using District terms and conditions; settled quickly. IB- How will data from investigation be managed; will location coordinates be
collected at each boring location; if so, how will that data be shared? All data will be
stored in a database; should be available for public use.
IB- What will be done with the continuous core samples collected during sonic drilling? No current plans for temporary storage of core materials.
JB- LRWQCB should consider adding a more complete CSLT storm drain layer to
sample grid in order to consider if there is any relation between storm drain system and PCE contamination. IB- is LRWQCB considering additional borings near other stormwater retention basins, given recent findings of LTLW investigation near Tucker
Avenue Basin? Storm drain system is a high priority of the SB445 investigation.
7) Upcoming Events/Action Items 13:40
Meeting 5 Action Items
RR- Project team should develop a project schedule for the recommended interim alternative. Depending on timing, may have a bearing on availability of Prop 68 or other funding sources for possible use during implementation.
AK- Schedule phone call to discuss possible eligibility of TKPOA for public funding
SI – Water agency wish list for future actions/activities as part of a recommended alternative;
ST – Written comments on PDI, and Groundwater Model Reports.
SI – Addressing comments received on draft PDI Report.
IB – Recent cost data for District water line projects.
SI- Contact Tahoe Water Suppliers Association regarding surface water intake
AGENDA
SOUTH TAHOE PUBLIC UTILITY DISTRICT
TAC Meeting 5
South YFeasibility Study of Remedial Alternatives(D1712508-1)
Friday, June 21, 2019 10:00 AM- 2:00 PM
Go To Meeting Conference Call
Call-In Number: +1 (872) 240-3311; Access Code: 217-469-869
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5_20190621_final.docx 13
requirements and possible surface water treatment exemptions.
SI – KJ to provide sizing criteria assumptions used for developing Alternatives to
water purveyors for feedback.
TC – SWRCB will check-in with SRF on status of LBWC application for LBWC 5 treatment system funding.
JL- Review comments on draft Groundwater Fate & Transport Report are due next
Wednesday. BG- LRWQCB to provide revised figures showing SB445 Sample Grid.
Upcoming Events
• Public Outreach - Workshop 5 (6/26/2019) • F&T Modeling Report – Final (June 2019) • Pre-Design Investigation Report - Final (June 2019)
• IS Checklists – in-progress
• Next TAC Meeting – near release of draft FS Report (late August/early
September).
8) Adjourn 14:00