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HomeMy Public PortalAbout09-20-23 Supplemental Material Item 10Conceptual Regional Groundwater Development BOARD OF DIRECTORS MEETING September 20, 2023 2 1.Background 2.Groundwater Model Upgrade 3.Well Master Plan Update 4.Assessment of Current PFAS Condition and the long-term PFAS management strategy 5.Need for Supplemental Groundwater Supply 6.Cost and Schedule Comparisons 7.Next Steps and Recommendations Discussion Outline 2 3 Initiative 2 Evaluate and develop appropriate new water supply and reliability opportunities Initiative 1 Establish a diversified water supply plan Initiative 3 Continue to effectively implement infrastructure projects in the water system Capital Improvement Program (CIP) Background •Zone 7 is updating the groundwater model and the Well Masterplan for supplemental groundwater development •The City of Pleasanton is investigating water supply alternatives to recover their groundwater pumping quota – 3,500 acre-feet per year or 3 million gallons per day •Pleasanton is open to explore a regional groundwater project with Zone 7 •Need to evaluate the regional project concept to see if it could be mutually beneficial for Pleasanton and the region •Need to propose recommendations to Zone 7’s Board 4 Groundwater Model Upgrade: •First developed in the 1980s and last updated in 2016 •Model domain needs to cover all fringe and upland areas •Need to incorporate current hydrogeological data and basin information •The upgraded Model will be useful for various analyses and assessments including: ▪Calculating water budgets and groundwater storage; ▪Analyzing climate change and drought impact ▪Supporting well master planning and well site selection ▪Analyzing PFAS management and purified water studies ▪Evaluating SGMA’s sustainability criteria and ▪Complying with Executive Orders and legislations 55 Well Master Plan (WMP) Update: •The objective is to develop a strategic roadmap to develop supplemental groundwater supply •In 2005, Zone 7 prepared the WMP (2005) •The “preferred alternative” identified installing seven new wells •Installed three municipal water supply wells (COL1, COL2, and COL5) •In October 2012, the Board adopted Resolution No. 13-4230, the water supply reliability policy, •at least 85% of M&I water demands in 99% of the time, and •100% of M&I water demands in 90% of the time •Among multiple objectives, the WMP is to address: •Unpredictable hydrologic conditions stemmed from global climate change •Changing regulatory environment, and •Water quality threats from emerging contaminants such as PFAs compounds and Chromium 6 6 7 Assessment of Current PFAS Condition and Long-term PFAS Management Strategy Overview of Existing Municipal Wells 7 PFAS Concentration in Upper Aquifer 8 PFAS Concentration in Lower Aquifer 9 Pump & Treat at Mocho and Chain of Lakes Wells Upper Aquifer Lower Aquifer ng/L ng/L •This model scenario analyzed pumping and treating PFAS plume at Mocho and Chain-of-Lake locations for 20 years. •It showed that the plume could be reduced and managed but won’t be cleaned up entirely. 10 Components of Long -term Strategy (Post 2023) DIVERSIFING MANAGING BLENDING & TREATING MONITORING MANAGING GROUNDWATER QUALITY to prevent further degradation DIVERSIFING GROUNDWATER SOURCES to become more resilient BLENDING & TREATING to meet water quality standards MONITORING to track and manage groundwater quality 11 13 Need for Supplemental Groundwater Supply Net Capacity Need with Allowance for Losses •To meet Zone 7’s need, a minimum of 2 x 4 mgd wells or 3 x 3 mgd wells will be needed •To meet Zone 7 + Pleasanton’s need, 2 x 6 mgd wells or 3 x 4 mgd wells will be needed 12 Notes: •mgd – million gallons per day •GPQ – Groundwater Production Quota of 3,500 acre-feet per year or approximately 3 mgd Notes: 1.Well sites shown on the following slides are based on conceptual locations 2.Actual well capacities could be greater than or less than listed capacities depending on actual yields 3.Well site screening -- using existing groundwater model, pilot borings, water chemistry analysis, yield analysis, fatal flaw analysis -- will be conducted prior to final site selection 4.Final well locations and capacities will be based on information obtained from field investigation 5.If feasible, submersible pumps will be used to minimize well profile 6.Centralized treatment at Hopyard 6 location is conceptualized for greater cost savings 13 Potential Pipeline Alignment 14 15 18 Cost and Schedule Comparisons Two 4 mgd wells (Meet Zone 7 Demand Only) •8 MGD = 2 new wells × 4 mgd •$29M construction •100% Zone 7 Cost •Capital cost per AF = $327 Upsized Two 6 mgd wells (Meet Zone 7 + Pleasanton GPQ) •12 MGD = 2 new wells × 6 mgd •$32M construction •25% Pleasanton cost share ($8M) •Capital cost for Zone 7 $32M – $8M = $24M •Capital savings for Zone 7 $29M - $24M = $5M •Capital cost per AF = $241 16 Zone 7 gains 8 MGD production capacity. Zone 7 gains 9 MGD (75% of a total 12 MGD production capacity). Pleasanton gets its GPQ of 3 MGD (25%). If two wells can produce sufficient yield: Three 3 mgd wells (Meet Zone 7 Demand Only) •9 MGD = 3 new wells × 3 mgd •$40M construction •100% Zone 7 Cost •Capital cost per AF = $400 Upsized Three 4 mgd wells (Meet Zone 7 + Pleasanton GPQ) •12 MGD = 3 new wells × 4 mgd •$41M construction •25% Pleasanton cost share ($10.2M) •Capital cost for Zone 7 $41M – $10.2M = $30.8M •Capital savings for Zone 7 $40M - $30.8M = $9.2M •Capital cost per AF = $309 If three wells are required: 17 Zone 7 gains 9 MGD production capacity. Zone 7 gains 9 MGD (75% of a total 12 MGD production capacity). Pleasanton will get its GPQ of 3 MGD (25%). Take-Aways •If hydrogeologically feasible, maximizing (upsizing) well size is more cost-effective than adding wells. •Centralized chemical facilities yield cost savings compared to treatment at each well site. •Results reflect capital costs only. •Cost savings from operational efficiencies are not yet included. •Annual O&M and water production costs are not included. 18 Zone 7’s FY27-FY31 CIP Funding and Schedules 19 Semi- Parallel Regional Project Sequential Independent Projects FY 23/24 FY 25/26 FY 26/27 FY 27/28 FY 28/29 Bernal Wells 1&2 and Pipeline WMP Update GW Model Upgrade Pleasanton Well Project Bernal Wells 1&2 and Pipeline WMP Update GW Model Upgrade Comparison of Project Schedules Compression FY 24/25 20 Next Steps and Recommendations Next Steps: •Proceed with accelerated groundwater model upgrade and the well master plan update •Continue with project development activities (planning, budgeting, easements for pilot boring, etc.) for installing new wells Recommendations: •Continue Zone 7’s collaboration with Pleasanton •Construct pilot wells in candidate sites and conduct yield analysis to evaluate groundwater production potential (actual available yields) •Determine feasibility of regional groundwater development and synergetic cost advantage at preliminary design phase 24 21 Questions?