Groundwater Replenishment with Purified Water Injection Provides Drought Protection & Environmental Benefits Santa Margarita Groundwater Replenishment Project PNW AWWA Conference 3 May 2017
Presentation Overview Introduction & Project Benefits Groundwater Recharge (GWR) Regulations Advanced Purification Treatment Review of Hydro-geologic modeling for injection Environmental Benefits from GWR Estimated Project and Life-cycle Costs Questions
The Santa Margarita GW Basin supplies water to ~40,000 people in northern Santa Cruz County, California
The objective is to recharge the Lompico Aquifer which is the primary water supply source for the area.
The SMGB Lompico Aquifer groundwater levels have dropped significantly over the past 25 years. 1988 1988 2012
A Groundwater Recharge Project for the Santa Margarita GW Basin would provide multiple benefits to the region. Replenish over-drafted aquifers Provide up to 6,000 AF of drought storage. Reduce energy needed for well pumping. Benefits SVWD, SLVWD, MHA, and all other pumpers in the Santa Margarita GW Basin. Higher groundwater levels provide increased base flows in streams and springs, and help riparian habitats. Increased stream flow provides more flow for endangered species in San Lorenzo River. Benefits SLVWD, SCWD, other surface water stakeholders.
Current Available RW for Groundwater Replenishment ranges from 0.4 to 0.9 mgd 1.20 Scotts Valley WRF Average Daily Flows, 2014 1.00 0.80 Flow, MGD 0.60 0.40 Influent Flow Secondary Effluent Flow Recycled Water Demand 0.20 0.00
Projected Available Source Water for Advanced Purification Facility (APF) and Injection Water for GWR Year Annual Available Source for APF, AFY Available Purified Water for Injection, AFY (a) 2015 718 574 2020 738 590 2025 758 606 2030 778 622 2035 798 638 (a) Assumes 80-percent recovery for the APF treatment processes
Recycled Water quality is relatively good and can be treated to meet Primary and Secondary drinking water MCLs. Constituent Units MCL Ave Max (95th %ile) General Physical Constituents Turbidity NTU 0.2 0.52 0.95 0.08 Biochemical Oxygen Demand (BOD) mg/l 1.91 4.62 1 Total Suspended Solids (TSS) mg/l 1.58 2.19 0.5 Total Organic Carbon (TOC) mg/l 9.27 12 7.8 Color CU 15 (b) 18.33 30 10 Temperature ºC ph units 7.50 8 7 Odor (at 60 C) TON 3 (b) 20 40 3 Langelier Index (at 25 C) -- 0.42 0.74 0.17 General Mineral Constituents Total Dissolved Solids (TDS) mg/l 500 (a) 542.07 674.62 480 Alkalinity (as CaCO3) mg/l 209.38 280 170 Calcium (Ca) mg/l 48.01 49 46.02 Magnesium (Mg) mg/l 17.29 20 15.16 Sodium (Na) mg/l 101.36 140 5.61 Potassium (K) mg/l 33.57 35 30.29 Ammonia (NH4) mg-n/l 0.38 0.738 0.045 Bicarbonate (HCO3) mg/l 221.42 280 175.68 Sulfate (SO4) mg/l 250 (a) 94.61 104.42 87 Phosphate (PO4) mg/l 0.31 0.31 0.31 Chloride (Cl) mg/l 250 (a) 166.25 191.27 140 Min
June 2014 Regulations for Groundwater Replenishment Reuse Projects Treatment Requirements Water Quality Requirements Prior to Recharge Spreading (i.e., surface application) Oxidation Filtration Disinfection Soil aquifer treatment Injection with FAT* (i.e., subsurface application) Oxidation, Filtration Reverse Osmosis 12-log virus reduction (99.9999999999%) 10-log Giardia cyst reduction (99.99999999%) 10-log Crypto oocyst reduction (99.99999999%) Drinking water MCLs 10 mg/l total nitrogen Action levels for lead and copper TOC 0.5 mg/l for injection TOC 0.5/RWC for spreading Advanced Oxidation Process (AOP) *FAT = full advanced treatment, i.e., advanced water purification (AWP)
June 2014 Regulations for Groundwater Replenishment Reuse Projects Other Requirements: Underground Retention Time minimum of 2 months. Blending Water for injection, up to 100% purified water; for spreading, initial max 20% recycled water blend. APF Treatment Train must have at least 3 separate processes to achieve the 12-10-10 log removal. Long-Term Monitoring - must have monitoring wells and regular sampling plan to confirm the underground retention time requirements are being met.
Advanced Purification Facility Treatment Process Flow Diagram City of Scotts Valley Secondary Effluent Existing Media Filtration / UV Disinfection RW Equalization Tank UF RO AOP PW Tank Injection Well Existing Facilities Treatment Processes Scotts Valley WWTP Target Process Log Removal / Inactivation Credits Scotts Valley WRF UF RO UV/ AOP Aquifer Total Log Removal/ Inactivation DDW Required Log Removal/ Inactivation Additional Safety Factor Log Above DDW Pathogen Virus 1 4 0 1 6 6 18 12 6 Giardia 1 1 4 1 6 0 13 10 3 Cryptosporidium 1 1 4 1 6 0 13 10 3
APF modular treatment processes provide operational flexibility and relatively small facility footprint. Ultrafiltration System Reverse Osmosis System UV / AOP System
Groundwater Injection Capacity and Travel Time Study SVWD is exploring injection of purified water to replenish the over-drafted Lompico GW aquifer. The Santa Margarita GW Basin Groundwater Model (2015) was used to evaluate the potential for injection into the Lompico aquifer. The model evaluated: The injection rate of ~650 AFY and the ability of the aquifer to receive and retain the purified water The underground retention time to the nearest drinking water wells The long-term storage capacity of the Lompico aquifer
The shut-down Hanson Quarry property is at the southern end of the SM Basin and could be an appropriate location for injection.
Injection wells to provide direct recharge of the Lompico Aquifer were modeled with the hydro-geological MODFLOW model and database. Existing Drinking Water Well Proposed Purified Water Injection Well
GW Model results show underground retention time to nearest drinking water wells is significantly greater than the required 2 months minimum. Existing Drinking Water Well Proposed Purified Water Injection Well Extent of ~6-month Underground Retention Time
GW Model results show underground retention time to nearest drinking water wells is significantly greater than the required 2 months minimum. Existing Drinking Water Well Proposed Purified Water Injection Well Extent of ~1-year Underground Retention Time
GW Model results show underground retention time to nearest drinking water wells is significantly greater than the required 2 months minimum. Existing Drinking Water Well Proposed Purified Water Injection Well Extent of ~2.5-year Underground Retention Time
GW Model results show underground retention time to nearest drinking water wells is significantly greater than the required 2 months minimum. Existing Drinking Water Well Proposed Purified Water Injection Well Extent of 5-year Underground Retention Time
The GW Model shows that the Lompico Aquifer under HQ can continue to receive the volumes of injection water for over 20 years. Lowest Surface Elevation in Hanson Quarry - 554 feet Elevation of SM/Lompico Contact - 480 feet
Additional groundwater storage in the Lompico aquifer portion of the Santa Margarita Basin plateaus at approximately 6,000 AF. Groundwater Storage for drought
After ~10 to 15 years, injected water starts to provide greater increases to base flows in local streams and springs.
The stored groundwater could be used for additional drought pumping for regional water partners.
Injecting water into the Lompico aquifer at the southern end helps to raise water levels throughout the basin over time. 2012
Injecting water into the Lompico aquifer at the southern end helps to raise water levels throughout the basin over time. Future 10-Years Model assumes injection of ~650 AFY at Hanson Quarry
Injecting water into the Lompico aquifer at the southern end helps to raise water levels throughout the basin over time. Future 20-years Injection in the south helps to raise water levels in the north as well.
Injecting water into the Lompico aquifer at southern end helps to raise water levels throughout the basin over time. Future 28-years The entire Santa Margarita Basin benefits from raised water levels, even though injection is just in the south.
GW Model shows that recharge of purified water benefits the overall Santa Margarita GW basin Injected water can provide drought storage up to approximately 6,000 AF. Injection of purified water creates a local mound that helps raise levels throughout the Lompico aquifer. Higher groundwater levels reduce pumping energy use and cost. Higher groundwater levels provide increased base flows in streams and springs, and helps endangered species in San Lorenzo River. SLVWD could increase GW pumping to reduce withdrawals from the San Lorenzo River.
Project Alternative No. 1: APF at City WRF and Associated Infrastructure
Estimated Life Cycle Costs for Alternatives Alt. Description Potential Supply (AFY) Conceptual-Level Project Cost (mil $) Annualized Cost ($/AF) 1.a Advanced Purification Facility at SV WRF 560 $19.5 $2,090 2.a 2.b 2.c 2.d Advanced Purification Facility at Hanson Quarry, Pipeline Alternative A. Recycled Water line extension, Concentrate disposal tie-in to existing outfall at Graham Hill Rd. Advanced Purification Facility at Hanson Quarry, Pipeline Alternative B. Recycled Water pipeline replacement, Concentrate disposal tie-in to existing outfall at Graham Hill Rd. Advanced Purification Facility at Hanson Quarry, Pipeline Alternative C. Recycled Water pipeline extension, Concentrate disposal tie-in to existing outfall at Estrella Dr. Advanced Purification Facility at Hanson Quarry, Pipeline Alternative D. Recycled Water pipeline replacement, Concentrate disposal tie-in to existing outfall at Estrella Dr. 560 $19.7 $2,150 560 $21.2 $2,290 560 $19.7 $2,200 560 $20.8 $2,250
SMGB GWR Program Schedule
Questions and Discussion Flow, MGD 1.20 1.00 0.80 0.60 0.40 0.20 0.00 Scotts Valley WRF Average Daily Flows, 2014 January February March April May June July August September October November December Influent Flow Secondary Effluent Flow Recycled Water Demand