Recomputation of Ambient Water Quality in the Santa Ana River Watershed

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Collin Lawson
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1 Recomputation of Ambient Water Quality in the Santa Ana River Watershed July 9, 2013 Prepared for: Basin Monitoring Program Task Force

3 Basin Monitoring Program Task Force Project Director Mark Norton, PE, LEED SAWPA Principal-in-Charge Mark Wildermuth, PE Project Manager Andy Malone, PG Data Collection Veva Weamer Groundwater- Level Mapping Tara Rolfe, PG Calculation of Statistics Eric Chiang, PhD Groundwater- Quality Mapping Samantha Adams Interpretive Tools Andy Malone, PG Report Veva Weamer

4 Data Collection Collection July through August 2012 Last three years of data Water-quality data Water-level data Well information Data Formats Microsoft Excel spreadsheets Microsoft Access database Hard Copy

5 Data Collection Well Information (if new) Well Name Well Type Well Status Well X-Y Coordinates Ground-Surface Elevation Distance from Reference Point to Ground Surface Reference Point Type Depth of Well Casing Depth Intervals of Well Perforations

6 Data Collection Groundwater-Level Data Well Name Measurement Date/Time Depth from Reference Point to Water Level Activity of Well During Measurement Measurement Method

7 Data Collection Groundwater-Quality Data Well Name Sample Date/Time Analyte Name Result Detection Limit Units Analytes of Interest Alkalinity, Total (as CaCO3) Bicarbonate Calcium Carbonate Chloride Electrical Conductivity (Specific Conductance) Fluoride Magnesium Nitrate as NO 3 or Nitrate as N ph Potassium Silica Sodium Sulfate Total Dissolved Solids

8 Today s Presentation Why do we recompute ambient groundwater quality? How do we recompute ambient groundwater quality? How do we utilize the results?

14 Moreno Valley

15 San Bernardino

16 Current Ambient TDS in Groundwater ( )

17 Key Ingredients for Salt/Nutrient Management 1. Characterization of the hydrologic system 2. Numeric water-quality objectives 3. A monitoring and surveillance program 4. Method for estimating ambient quality 5. Predictive computer-simulation models

18 Background 1950s to the 1990s Salinity increasing in surface and ground waters First salt management plan developed in 1969 First Basin Plan developed in 1973 Importation of high-quality SWP water in 1973 Basin Plan updates in the 1980s and 1990s include salt management plans and wasteload allocations for N/TDS Dischargers disagreed with 1995 Basin Plan update and threaten suit

19 Background Chaos and fighting?...not true! The region had seriously reviewed causation, and identified the primary salt stressors What was lacking: Regulatory certainty Business reasons to address the emerging salinity problem

20 Background Regulatory Uncertainty: Objectives and sub-basins were not defensible TDS: About 200 wells; Two years of data Sub-basin boundaries didn t make hydrologic sense Business Reasons: Cost to comply with water quality objectives was ~ $3-5 billion Imported water becoming scarce and expensive Basin Plan would limit water recycling opportunities

21 Background Regional Board agreed to a review of the water quality standards, but did not have money to fund process Stakeholders offered to: Form a Task Force to direct the institutional and scientific process Fund the effort

22 Nitrogen/TDS Task Force Task Force members: Wastewater dischargers Water supply agencies Upper & Lower Basin agencies Federal agencies invited (USGS & USEPA) Environmental representatives generally absent Regional Board staff Hired a team of consultants to lead the effort Risk Sciences Institutional scope and facilitation Wildermuth Environmental Technical scope

23 Double-Edged Sword Regional Board agreed to participate with understanding that all parties must agree in advance to live with the results Standards might be more or less restrictive Dischargers repeatedly claimed that they would live with process based on good science Education, consensus, and integrity

24 Technical Scope of Work Establish sub-basins based on hydrogeology Establish anti-degradation water-quality objectives (SWRCB Resolution 68-16) based on historical data Estimate current ambient quality of the groundwater Calculate assimilative capacity Difference between the objective and current ambient quality Develop new POTW wasteload allocations Establish an on-going monitoring and assessment program Establish maximum benefit water quality objectives and salt management commitments

26 Revision of Sub-Basin Boundaries The boundaries for groundwater management zones are consistent with the hydrology A distinct hydrologic unit with a consistent groundwater flow system Areas of recharge connected with areas of discharge

37 Procedures to calculate groundwater quality objectives Develop volume-weighted management zone estimates of TDS and nitrate concentrations Concentration MZ = Mass MZ / GW Volume MZ historical ambient conditions ( ) Objective setting period current ambient conditions ( ) Measure of compliance

38 Procedures to calculate groundwater quality objectives Reasoning: The 20-year period spanned variations in the precipitation record The period was consistent with SWRCB Resolution (Anti-deg policy) The volume-weighting accounts for the complexity of the hydrogeology The management zone concept recognizes the natural hydraulic and water-quality gradients across the watershed

39 TDS Concentration (mg/l NO3-N Concentration (mg/l 600 Ow ner Name: Local Name: WE ID: TDS and NO3-N Concentration Time Series EAST VALLEY WATER DISTRICT PL 25A TDS New TDS ADFM NO3-N New NO3-N Year 0

40 Develop WQ Point Statistics at Each Well Each well must have at least three data points in separate years during the 20-year analysis period. TDS and Nitrate-nitrogen Computed a TDS and nitrate statistic that accounts for variability resulting from: sampling error analytical error hydrological/climatic events non-homogeneous hydrogeologic properties

41 - Conceptual Figure -

42 View Sample Map

45 C amb = 1/V T * S(V i * c i ) Water Level Grid Cell Properties: Specific yield, concentration Bottom of A quifer

46 Concentration MZ = Mass MZ / GW Volume MZ

47 Relative Mass of TDS in the Orange Orange County/Irvine Management Zones by Grid Cell 2006 TDS Mass (g) per grid cell

48 Compute Ambient Water Quality for Management Zones Post-process GIS grid Ambient TDS and NO 3 in each MZ Historical ( ) Objective Current ( ) Compliance Recomputation Compliance Every three years , , , Calculate assimilative capacity Objective - Current

49 Insert AC map Objectives

50 Insert AC map Current Ambient TDS

51 Insert AC map

52 Insert AC map Current Ambient NO 3 -N

53 Insert AC map

54 Assimilative Capacity Management Zones with assimilative capacity Regional Board, at its discretion, can permit discharges at TDS and N0 3 concentrations higher than the objective Management Zones that lack assimilative capacity Discharges to these basins must have TDS and N0 3 concentrations at or below the objectives (SWRCB Order No Rancho Caballero decision)

55 TIN (mg/l-n) Streambed Recharge (acre-ft/yr) 10 Annual Recharge to Riverside-A Figure 7a-TIN_RA Estimated Annual Streambed Recharge and Volume-Weighted TIN Concentration of the Santa Ana River to the Riverside-A Management Zone Scenario 7a - Planned Reuse in ,000 1-Year Volume-Weighted Average for TIN in Recharge 10-Year Volume-Weighted Running Average for TIN in Recharge 8 40, , , , Water Year 0

56 TIN (mg/l-n) Streambed Recharge (acre-ft/yr) 10 8 Annual Recharge to Riverside-A Figure 7a-TIN_RA Estimated Annual Streambed Recharge and Volume-Weighted TIN Concentration of the Santa Ana River to the Riverside-A Management Zone Scenario 7a - Planned Reuse in 2010 Nitrate-N Objective for Riverside-A (6.2 mg/l) Current Ambient Nitrate-N S36for Riverside-A (5.2 mg/l-n) 1-Year Volume-Weighted Average for TIN in Recharge 10-Year Volume-Weighted Running Average for TIN in Recharge 50,000 40, , , , Water Year 0

57 Insert time-series charts

58 Questions?

Using the Waste Load Allocation Model (WLAM) to Develop Effluent Limitations and Waste Discharge Requirements

Using the Waste Load Allocation Model (WLAM) to Develop Effluent Limitations and Waste Discharge Requirements Background The Regional Water Quality Control Board establishes water quality objectives to