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17W006_ TAC Proj Mtng 3_20181023_notes_FINALAGENDA SOUTH TAHOE PUBLIC UTILITY DISTRICT TAC Meeting 3 - NOTES South Y Feasibility Study of Remedial Alternatives (D1712508) Tuesday, October 23, 2018 9:30 AM - 12:00 PM Go To Meeting Conference Call Call-In Number: +1 (872) 240-3412; Access Code: 794-898-717 X:\Projects\General\17W006_So Y FS\4.0 TAC\Mtng 3_Oct 2018\Meeing Notes\17W006_ TAC Proj Mtng 3_20181023_notes_FINAL.docx 1 Attendees: T. Carter, SWRCB-DFA (TC); I. Bergsohn, STPUD (IB); S. Turrubiartes, SWRCB-DDW (ST); B. Grey, LRWQCB (BG); J. Burke, CSLT (JB); J. Lukins, LBWC (JL); S. Rybarski, DRI (SR); S. Itagaki, KJC (SI); M. Durant, KJC (MD) 1) Welcome/Self Introductions 9:30 • Non-Agenda Item: Shannon Cotulla, STPUD informed TAC that Water Purveyors are requesting meeting with SWRCB-DFA, SWRCB-DDW and LRWQCB staff to clarify water system(s) O&M Plan requirements in response to PCE contamination described in “Distribution System Operations and Maintenance Plan and Emergency Response Plan” letter dated 9/14/2018 by A. Revzani (SWRCB-DDW). Water purveyors are seeking to schedule a meeting with agency staff by end of October to confirm expectations. 2) Items in Progress 9:40 • MOU Update (T. Carter) • SWRCB-DFA may consider removing MOU from Agreement (D1712508); Agreement amendments submitted by IB to TC in September are presently on-hold until a determination on the MOU is made. If MOU is removed, the change will be reflected in the existing amendment that is currently on hold. MOU in current form is under discussion between LRWQCB and State Water Board attorneys. TAC is working collaboratively as intended and could continue to operate without an MOU for this project. • Baseline Human Health Risk Assessment (KJC) • Expect draft for TAC review within next 2 weeks. • FS Work Plan (KJC) • Looking for TAC feedback to address SWRCB-DFA comments on Remedial Action Objective (RAO) Table – see Agenda Item 3. • PDI Draft Report (KJC) • Expect draft of PDI Technical Report for TAC Review within next 3 weeks. 3) Remedial Action Objectives (KJC) 10:00 • Remedial Action Objectives (page 3 of 12) • SWRCB-DFA comments on FS Workplan RAO Table Items 5, 6 and 7 were discussed with TAC. As the objectives for Clean-Up Level (item 5); Area of Attainment (Item 6); and Restoration Time Frame (Item 7) may vary depending on Remedial Alternative approach, RAOs also need to be flexible (TC). RAOs may need to be revisited as KJC progresses with the FS process and these RAOs become better defined. At this point KJC is seeking suggested language changes that would reflect this needed flexibility and allow KJC to complete the final workplan for submittal to TC. • TC and BG agreed to seek further input from SWRCB-DFA and LRWQCB management concerning suggested language changes to the RAO table. If AGENDA SOUTH TAHOE PUBLIC UTILITY DISTRICT TAC Meeting 3 - NOTES South Y Feasibility Study of Remedial Alternatives (D1712508) Tuesday, October 23, 2018 9:30 AM - 12:00 PM Go To Meeting Conference Call Call-In Number: +1 (872) 240-3412; Access Code: 794-898-717 X:\Projects\General\17W006_So Y FS\4.0 TAC\Mtng 3_Oct 2018\Meeing Notes\17W006_ TAC Proj Mtng 3_20181023_notes_FINAL.docx 2 input from management is not forthcoming, the current language may be acceptable for the FS workplan (TC). • Clean-Up Levels in Source Areas: BG noted LRWQCB primary concern is back-diffusion of PCE from low permeability to high permeability zones as continuing sources of aqueous-phase PCE contamination relative to remedial action objectives and selection. SI noted that the Safe Drinking Water Act and the Clean Water Act/Porter Cologne may have different requirements. 4) Remedial Scenario Definition (KJC) 10:45 • Well Head Treatment (Alts_Modeling.xlsx) • This approach addresses PCE removal at the existing drinking water supply wells • Future Pumping Rates: Baseline model is currently using average annual water production (pumping rates) from previous 10-year period (2006-2016). • Scenario with Municipal Supply Wells pumping at nominal source capacity should be performed to identify the maximum amount of capture and PCE mass removal that could be achieved by Municipal Well pumping alone. – Pumping rates to be verified prior to DRI running scenario • Alternate scenario could involve pumping Municipal Supply Wells in a manner that solely satisfies average annual and max day demands. • Water purveyors need to closely look at the predicted future pumping rates and determine whether they are still reasonable or need to be changed; • IB will work with JL and R. Robillard, TKWC (RR) to review estimated average annual system and maximum day demand requirements developed during the Analysis of Basin Conditions for the LBWC and TKWC water systems; • From these estimates the proportions of this pumping needs to be distributed for Lead, Lag and Lag-lag wells to help better define Municipal Supply Well pumping rates for the future model scenarios. • Replacement Wells (Page 11 of 12) • This approach does not remove PCE but rather moves the drinking water supply wells to areas/zones outside of projected PCE contamination. • JL will take a closer look at proposed replacement well sites for LBWC system; • In terms of replacement wells, consideration also needs to be given to any existing impaired wells that could be used for extraction (e.g. TKWC #2) (TC) for remediation purposes (not supply); • Replacement wells will be modeled with all groundwater extraction removed from Layer 3 and pumping rates as developed in Well Head Treatment. • Mid-Plume Remediation • This approach removes PCE upgradient of the drinking water supply wells • PCE Distribution • 2016 – 2018 Field Data • B. Grey noted that that soil remediation has been AGENDA SOUTH TAHOE PUBLIC UTILITY DISTRICT TAC Meeting 3 - NOTES South Y Feasibility Study of Remedial Alternatives (D1712508) Tuesday, October 23, 2018 9:30 AM - 12:00 PM Go To Meeting Conference Call Call-In Number: +1 (872) 240-3412; Access Code: 794-898-717 X:\Projects\General\17W006_So Y FS\4.0 TAC\Mtng 3_Oct 2018\Meeing Notes\17W006_ TAC Proj Mtng 3_20181023_notes_FINAL.docx 3 performed at the 2 dry cleaners that are the likely primary source of PCE (LTLW and Norma’s); LTLW has ongoing soil vapor extraction. There remain secondary PCE sources including PCE bound to low transmissivity soils and in GW. Acknowledged the technological and economical limitations of remediating the secondary sources (ie what order of magnitude contaminant reduction would be likely for each proposed remedial technology) and that a hybrid remediation approach is likely required. • Model Simulated Contours • TAC Discussion/Remedial Scenarios for Model Evaluation • Comparison of field data versus modeled simulated PCE contours shows limitations on use of the model for directly evaluating mid-plume remediation scenarios. • KJC is continuing to work on possible mid-plume scenarios directed at “hot spots” identified in field data contours; KJC has not moved forward with FS evaluation of any mid-plume remediation alternatives, as preliminary model results were not encouraging. • IB requested that KJC keep the TAC informed through the Alternatives Modeling worksheet (Alts_Modeling.xlsx) and accompanying figure showing the modeled scenario(s) submitted to DRI for evaluation as this work progresses through the 4th quarter. • KJC to work with DRI to develop list of common outputs from each model run • DRI to confirm PCE mass removal estimates from the prior in situ (40 kg) and pump and treat (70 kg) remediation runs. 5) Upcoming Activities 11:30 • So. Y Groundwater Level Data Collection • Coordinated water level monitoring event scheduled for this Thursday (10/25/2018) • Public Meeting 3 (11/07/2018-tent.) • Meeting to update Public on progress of FS; scheduled for SLT City Council Chambers. Sachi will to participate to describe project status. • Public Meeting 4 to consider and receive public input on proposed remedial alternatives to be scheduled during 1st Quarter 2019. • PDI Draft Report Submittal • Anticipate draft for TAC review week of 11/7 • Modeling Evaluation/Remedial Scenarios • Modeling evaluations to be completed by January 2019 • FS - Screen Modeled Alternatives • FS to be completed by March 2019 • FS – Select and Develop Recommended Alternative AGENDA SOUTH TAHOE PUBLIC UTILITY DISTRICT TAC Meeting 3 - NOTES South Y Feasibility Study of Remedial Alternatives (D1712508) Tuesday, October 23, 2018 9:30 AM - 12:00 PM Go To Meeting Conference Call Call-In Number: +1 (872) 240-3412; Access Code: 794-898-717 X:\Projects\General\17W006_So Y FS\4.0 TAC\Mtng 3_Oct 2018\Meeing Notes\17W006_ TAC Proj Mtng 3_20181023_notes_FINAL.docx 4 • RAP to be completed by May 2019 6) Adjourn 12:00 • Next TAC Meeting – Week of December 9th (tbd) • Review progress of remedial scenario/model evaluations.