McAllister Wellfield Numerical Model (Section 1-4) Interim Report April 2002 Prepared for: The City of Olympia Public Works Department Olympia, Washington Prepared By: CDM 11811 NE 1st Street, Suite 201 Bellevue, WA 98005 CDM Project No. 19896.29422.Task7.Tsk7C Contents Executive Summary ..................................................................................................................viii Section 1 Introduction 1.1 Background...................................................................................................... 1-1 1.2 Purpose and Objectives of the Model.............................................................. 1-2 1.3 Interim Report Organization........................................................................... 1-3 Section 2 Conceptual Model Development 2.1 Description of Model Area .............................................................................. 2-1 2.1.1 Entire Model Area.............................................................................. 2-1 2.1.2 McAllister Area Description.............................................................. 2-2 2.2 Geologic History .............................................................................................. 2-3 2.3 Geologic and Hydrogeological Units .............................................................. 2-4 2.3.1 Holocene Alluvial and Deltaic Sediments (Sand and Gravel) .......... 2-5 2.3.2 Vashon Recessional Outwash (Qvr).................................................. 2-5 2.3.3 Vashon Glacial Till (Qvt)................................................................... 2-5 2.3.4 Vashon Advance Outwash (Qva)...................................................... 2-5 2.3.5 Kitsap Formation (Qf)........................................................................ 2-6 2.3.6 Salmon Springs Formation (Sea Level Aquifer, Qc).......................... 2-6 2.3.7 McAllister Gravel............................................................................... 2-6 2.3.8 Undifferentiated Quaternary and Tertiary (TQu)............................. 2-7 2.4 Climate............................................................................................................. 2-7 2.5 Groundwater Flow .......................................................................................... 2-7 2.6 Hydraulic Properties ....................................................................................... 2-8 2.7 Groundwater Recharge...................................................................................2-10 2.7.1 Precipitation Recharge......................................................................2-10 2.7.2 Subsurface Inflow .............................................................................2-10 2.7.3 Lake Seepage.....................................................................................2-11 2.8 Groundwater Discharge .................................................................................2-11 2.8.1 Pumping............................................................................................2-12 2.8.2 Springs and Seeps.............................................................................2-12 2.8.3 Major Rivers......................................................................................2-13 2.8.4 Stream Discharge..............................................................................2-14 2.8.5 Subsurface Flow to Puget Sound......................................................2-14 2.8.6 Evaporation and Transpiration ........................................................2-15 2.9 Water Budget Summary for Model Area .......................................................2-15 A iii P:\19896 - City of Olympia\29422 \7PROJDOC\2final.rpt\McA_040902_fnl.doc Contents Section 3 Model Construction 3.1 Model Code and Software Employed ............................................................. 3-1 3.2 Model Domain and Grid ................................................................................. 3-2 3.3 Model Structure............................................................................................... 3-3 3.4 Material Properties .......................................................................................... 3-4 3.5 Precipitation Recharge..................................................................................... 3-5 3.6 Groundwater Pumping................................................................................... 3-6 3.7 Springs ............................................................................................................. 3-7 3.8 Kettle Lakes...................................................................................................... 3-8 3.9 Streams and Rivers .......................................................................................... 3-9 3.10 Other Boundary Conditions...........................................................................3-10 Section 4 Model Calibration 4.1 Calibration Objectives...................................................................................... 4-1 4.2 Steady-State Calibration .................................................................................. 4-1 4.2.1 Targets................................................................................................ 4-1 4.2.2 Calibration Methodology .................................................................. 4-4 4.2.3 Steady-State Calibration Results........................................................ 4-5 4.2.4 Water Budget..................................................................................... 4-9 4.3 McAllister Springs Capture Zone Analysis....................................................4-11 Section 5 Transient Calibration ................................................................................. 5-1 Section 6 Wellfield Operation Predictions ............................................................... 6-1 Section 7 Summary........................................................................................................ 7-1 Section 8 References...................................................................................................... 8-1 Appendices Appendix A Model Layer Surface Elevation Figures Appendix B Time-Varying Water Levels for Key Calibration Wells Appendix C Technical Review Comments Response A iv P:\19896 - City of Olympia\29422 \7PROJDOC\2final .rpt\McA_040902_fnl.doc Tables Table 2-1 USGS Thurston County Model Hydraulic Properties Table 2-2 Conceptual Water Budget Table 3-1 Model Layering and Hydrogeologic Units Table 3-2 Distribution of Pumping Table 3-3 Key Kettle Lake Details Table 3-4 Key River and Stream Details Table 4-1 Statistical Weighting for Observation Well Water Levels in Entire Model Table 4-2 Statistical Weighting for Observation Well Water Levels in McAllister Area Table 4-3 Weighted and Unweighted Calibration Statistics for McAllister Area Table 4-4 Weighted and Unweighted Calibration Statistics for Model Table 4-5 Mass Balance Summary Table 4-6 Mass Balance Summary for Key Hydrologic Features Figures Figure 2-1 McAllister Model Area Figure 2-2 McAllister Area Figure 2-3 Surficial Geology of McAllister Area Figure 2-4 Pumping Wells in Major Aquifer Units Figure 2-5 Annual Precipitation at Olympia Airport (1980-99) Figure 2-6 Average Monthly Precipitation at Olympia Airport (1980-99) Figure 2-7 Observed Groundwater Levels and Interpreted Contours - Qvr Figure 2-8 Observed Groundwater Levels and Interpreted Contours - Qva Figure 2-9 Observed Groundwater Levels and Interpreted Contours - Qc Figure 2-10 Observed Groundwater Levels and Interpreted Contours - TQu Figure 2-11 Precipitation-Groundwater Recharge Model Figure 2-12 Lake St. Clair Stage Level 1992-2000 Figure 2-13 Conceptual Model of Lake St. Clair Figure 2-14 Aquifer Pumping by Aquifer Figure 2-15 McAllister Springs Discharge 1997-2001 Figure 3-1 Finite-Difference Grid for the Model Domain Figure 3-2 Finite-Difference Grid in the McAllister Area Figure 3-3 USGS’ Thurston County Model Grid Figure 3-4 Hydraulic Conductivities in Layer 1 (Qvr) Figure 3-5 Hydraulic Conductivities in Layer 2 (Qvt) Figure 3-6 Hydraulic Conductivities in Layer 3 (Qva) Figure 3-7 Hydraulic Conductivities in Layer 4 (Qf) Figure 3-8 Hydraulic Conductivities in Layers 5 and 6 (Qc) Figure 3-9 Hydraulic Conductivities in Layer 7 (TQu) Figure 3-10 Hydraulic Conductivities in Layer 8 (TQu) A v \\gigsvr\common\19896 -29422\7PROJDOC\rpt_outline.doc List of Figures Figure 3-11 Hydraulic Conductivities in Layer 9 (TQu) Figure 3-12 Section A-A’ through Model Figure 3-13 Section B-B’ through Lake St. Clair Area Figure 3-14 Section C-C’ through McAllister Springs Area Figure 3-15 Recharge Zonation Figure 3-16 Model Boundary Conditions – Layer 1 Figure 3-17 Model Boundary Conditions – Layer 2 Figure 3-18 Model Boundary Conditions – Layer 3 Figure 3-19 Model Boundary Conditions – Layer 4 Figure 3-20 Model Boundary Conditions – Layer 5 Figure 3-21 Model Boundary Conditions – Layer 6 Figure 3-22 Model Boundary Conditions – Layer 7 Figure 3-23 Model Boundary Conditions – Layers 8 & 9 Figure 4-1 Steady-state Calibration Wells in McAllister Area (McAllister Gravel and Sea Level Aquifers) Figure 4-2 Steady-state Calibration Wells in Lake St. Clair Area (McAllister Gravel and Sea Level Aquifers) Figure 4-3 Calibration Data Weighting Zones Figure 4-4 McAllister Area Weighting Zones Figure 4-5 Steady-state Modeled Heads (Qvr - layer 1) Figure 4-6 Steady-state Modeled Heads