DATA UPDATE AND ON-SITE FEASIBILITY REPORT SALTESE FLATS WETLAND RESTORATION INVESTIGATION Spokane County, Washington Prepared for: SPOKANE COUNTY DIVISION OF UTILITIES PUBLIC WORKS BUILDING 1026 W. BROADWAY AVE. SPOKANE WA 99260 Prepared by: 1120 Cedar Street Missoula, MT 5802 15320 East Marietta Ave, Suite 9A Spokane Valley, WA 99216-1870 January 2010 Project No. 100002604 Data Update and On-Site Feasibility Report Saltese Flats Wetland Restoration Investigation CONTENTS Page 1.0 INTRODUCTION ............................................................................................................................... 1 1.1 Purpose and Scope ...................................................................................................................... 1 1.2 Additional Data Sources .............................................................................................................. 5 2.0 ADDITIONAL DATA SUMMARY .................................................................................................. 6 2.1 Topographic Surveys................................................................................................................... 8 2.2 Photographic Documentation ...................................................................................................... 9 2.3 Meteorological Data Compilation ............................................................................................. 10 2.4 Soil Borings and Well Installations ........................................................................................... 12 2.5 Wetland Delineation .................................................................................................................. 12 2.6 Surface Water Stage and Discharge .......................................................................................... 16 2.7 Water Management at Saltese Flats .......................................................................................... 22 2.8 Groundwater Levels .................................................................................................................. 24 2.9 Water Quality ............................................................................................................................ 27 3.0 WATER BUDGET ........................................................................................................................... 32 3.1 Methodology ............................................................................................................................. 32 3.2 Water Budget Scenarios ............................................................................................................ 34 3.3 Shelley Lake and Gravel Pit Infiltration .................................................................................... 41 4.0 RESTORATION FEASIBILITY SCREENING ............................................................................... 44 4.1 Restoration Scenario Alternatives ............................................................................................. 44 4.2 Screening Criteria ...................................................................................................................... 44 4.3 Option A Alternatives ............................................................................................................... 44 4.4 Option B Alternatives ................................................................................................................ 45 4.5 Option C Alternatives ................................................................................................................ 46 4.6 Preferred Restoration Alternatives ............................................................................................ 46 4.7 Review of Washington State Reclaimed Water Use Standards ................................................ 46 5.0 CONCLUSIONS AND RECOMMENDATIONS ............................................................................ 48 6.0 REFERENCES .................................................................................................................................. 50 APPENDICES APPENDIX A Topographic Maps APPENDIX B Example Photographic Documentation APPENDIX C Soil Boring Logs APPENDIX D Analytical Data and Laboratory Reports APPENDIX E Wetland Delineation Maps, Forma, and Photos APPENDIX F Surface Water Levels and Discharge Data and Groundwater Elevation Data APPENDIX G Water Budget Scenarios January 2010 ii .00 Data Update and On-Site Feasibility Report Saltese Flats Wetland Restoration Investigation TABLES Table 2-1. Annual Precipitation at Liberty Lake ....................................................................................... 10 Table 2-2. Monthly Precipitation at Pine Terrace, Spokane, and Coeur d’Alene ...................................... 10 Table 2-3. Cowardin Vegetation Types Within Routine Mapping Areas .................................................. 13 Table 2-4. Cowardin Vegetation Types Within Reconnaissance Mapping Areas ..................................... 14 Table 2-5. Surface Water Monitoring Locations ....................................................................................... 17 Table 2-6. Discharge Comparison Between Saltese Flats and Liberty Creek............................................ 18 Table 2-7. Saltese Flats Flow Estimates .................................................................................................... 22 Table 2-8. Preliminary Annual Groundwater Level Fluctuation Estimates ............................................... 26 Table 2-9. Offsite Well Summary .............................................................................................................. 27 Table 2-10. Synoptic Nutrient Sampling Results for Saltese Flats ............................................................ 29 Table 3-1. Average Outflow (cfs) from Saltese Flats by Modeling Scenario ............................................ 35 Table 3-2. Average Outflow (Ac-Ft) from Saltese Flats by Modeling Scenario ....................................... 35 Table 3-3. Summary of Shelley Lake Infiltration Rate Calculations ......................................................... 42 FIGURES Figure 1-1. Saltese Flats Location................................................................................................................ 2 Figure 1-2. Saltese Flats Watershed Delineation ......................................................................................... 3 Figure 1-3. Saltese Flats Restoration Options .............................................................................................. 4 Figure 2-1. Regional Monitoring and Data Source Locations ..................................................................... 6 Figure 2-2. Saltese Flats Monitoring and Data Source Locations ............................................................... 7 Figure 2-3. Saltese Flats Photo-Point Locations .......................................................................................... 9 Figure 2-4. Average Monthly Precipitation at Stations Surrounding Saltese Flats ................................... 11 Figure 2-5. Precipitation Cumulative Departure Plots ............................................................................... 11 Figure 2-6. Watershed and Surface Water Related to Saltese Flats ........................................................... 16 Figure 2-7. Liberty Creek Discharge Data ................................................................................................. 18 Figure 2-8. Liberty Creek Discharge Data ................................................................................................. 19 Figure 2-9. Water Levels for Liberty Creek and Saltese Flats Inlets ......................................................... 19 Figure 2-10. Water Levels for Shelley Lake and Saltese Flats Outlets...................................................... 20 Figure 2-11. Water Levels for Shelley Lake and Saltese Flats Outlets...................................................... 21 Figure 2-12. Saltese Flats Water Management Features ............................................................................ 23 Figure 2-13a. Shallow Groundwater Elevations-May 2009 ...................................................................... 25 Figure 2-13b. Shallow Groundwater Elevations-June 2009 ...................................................................... 25 Figure 2-14. Depth to Groundwater-May 2009 ......................................................................................... 26 Figure 2-15. Piper Diagram of Water Quality Sampling Results .............................................................. 28 Figure 3-1. Water Budget Components for Average Year, Baseline Condition ........................................ 36 Figure 3-2. Water Budget Components for Average Year With 8MGD Reclaimed Water....................... 38 Figure 3-3. Plot of Data for Shelley Lake Infiltration Rate Estimates ....................................................... 41 January 2010 iii .00 1.0 INTRODUCTION This document summarizes new data and evaluates feasibility for restoration options at Saltese Flats. Sal- tese Flats is located in Spokane County southeast of the city of Spokane Valley (Figure 1-1). The area known as Saltese Flats occupies roughly 1,200 acres of land that lies within a watershed of approximately 14,000 acres (Figure 1-2). The Flats includes land that functions as