BLACK LAKE PHOSPHORUS AND ALGAE CONTROL PLAN Prepared for Black Lake Special District Prepared by Herrera Environmental Consultants, Inc. Note: Some pages in this document have been purposely skipped or blank pages inserted so that this document will copy correctly when duplexed. BLACK LAKE PHOSPHORUS AND ALGAE CONTROL PLAN Prepared for Black Lake Special District 120 State Avenue Northeast, No. 303 Olympia, Washington 98501 Prepared by Herrera Environmental Consultants, Inc. 2200 Sixth Avenue, Suite 1100 Seattle, Washington 98121 Telephone: 206-441-9080 June 16, 2015 CONTENTS Executive Summary ......................................................................................... v 1. Introduction ............................................................................................ 1 2. Project Background and Data Sources ............................................................. 3 2.1. Lake Watershed .................................................................................. 3 2.2. Lake Water Quality .............................................................................. 8 2.2.1. Water Quality Profiles .............................................................. 8 2.2.2. Trophic State Parameters ......................................................... 10 2.3. Cyanotoxins ...................................................................................... 15 2.4. Fisheries .......................................................................................... 22 2.5. Recreational and Beneficial Uses ............................................................. 23 3. Sediment Phosphorus ................................................................................ 25 3.1. Methods .......................................................................................... 25 3.2. Results ............................................................................................ 26 4. Water Budget ......................................................................................... 29 4.1. Methods .......................................................................................... 29 4.2. Results ............................................................................................ 30 5. Phosphorus Budget ................................................................................... 33 1.1. Methods .......................................................................................... 33 5.1. Results ............................................................................................ 35 6. Phosphorus and Algae Control Methods Evaluation ............................................. 43 6.1. Alum Treatment ................................................................................. 43 6.1.1. Alum Treatment Strategy ......................................................... 43 6.1.2. Aluminum Dose and Chemical Requirements ................................... 44 6.1.3. Alum Treatment Cost Estimates .................................................. 46 6.2. Phoslock Treatment ............................................................................ 47 6.2.1. Phoslock Treatment Strategy ..................................................... 47 6.2.2. Phoslock Dose Requirements...................................................... 47 6.2.3. Phoslock Treatment Cost Estimates ............................................. 49 7. Alum Treatment Plan and Objectives ............................................................. 51 7.1. Treatment Plan ................................................................................. 51 7.2. Treatment Objectives .......................................................................... 52 8. Next Steps ............................................................................................. 55 8.1. Final Design ...................................................................................... 55 8.2. Permitting........................................................................................ 55 i pjj 15-05987-000 black lake p-a cntrl plan.docx 8.3. Technical Specifications and Contractor Procurement .................................... 56 8.4. Treatment Oversight ........................................................................... 56 8.5. Water Quality Monitoring ...................................................................... 57 8.5.1. Jar Test .............................................................................. 57 8.5.2. Treatment Monitoring .............................................................. 57 8.5.3. Post-Treatment Monitoring ....................................................... 59 8.6. Reporting ......................................................................................... 59 9. References ............................................................................................ 61 APPENDICES Appendix A Lake Modeling Report Appendix B Water and Nutrient Budgets and Data Appendix C Sediment Data TABLES Table 2 1. Black Lake Physical Features. ........................................................... 3 Table 2-2. Carlson’s Trophic State Indices and Criteria for Lakes. ............................ 10 Table 2-3. Cyanobacteria Presence in Algae Scum Samples from Black Lake. ............... 22 Table 2-4. Known Fish Species in Black Lake. .................................................... 22 Table 4-1. Black Lake Depth-Storage Table. ...................................................... 30 Table 4-2. Black Lake Annual Water Budget, January 2010 Through December 2012. ..... 31 Table 5-1. Winter, Summer, and Annual Phosphorus Inputs to Black Lake, 2010– 2012. ....................................................................................... 37 Table 5-2. Summer Phosphorus Outputs from Black Lake, 2010–2012. ....................... 41 Table 5-3. Comparison of Summer Internal Phosphorus Input Estimates for Black Lake, 2010–2012.......................................................................... 42 Table 6-1. Alum Treatment Doses and Costs for Three Black Lake Scenarios. ............... 48 Table 7-1. Comparison of Alum Treatment Doses in Washington. ............................. 52 Table 7-2. Alum Treatment Objectives for Summer Trophic Status in Black Lake. ......... 52 ii pjj 15-05987-000 black lake p-a cntrl plan.docx FIGURES Figure 2-1. Black Lake Location Maps. .............................................................. 4 Figure 2-2. Black Lake Watershed Land Cover. .................................................... 6 Figure 2-3. Black Lake Watershed Model Sub-Basins. ............................................. 7 Figure 2-4. Black Lake Monitoring Locations. ....................................................... 9 Figure 2-5. Secchi Depth and Epilimnion Chlorophyll Summer Mean and Range, Black Lake 1992–2014........................................................................... 11 Figure 2-6. Epilimnion Chlorophyll versus Secchi Depth, Black Lake 1992–2014. ............ 13 Figure 2-7. Total Phosphorus Summer Mean and Range, Black Lake 1992–2014. ............. 14 Figure 2-8. Surface Total Phosphorus versus Epilimnion Chlorophyll, Black Lake 1992–2014. ................................................................................ 16 Figure 2-9. Trophic State Indices, Black Lake 1992–2014. ....................................... 17 Figure 2-10. Black Lake Cyanotoxin Data Summary. ............................................... 19 Figure 2-11. Microcystin in Algae Scum, Black Lake 2010–2014. ................................. 20 Figure 2-12. Black Lake Algae Scum in Summer 2011. ............................................. 21 Figure 3-1. Black Lake Sediment Core Photographs. ............................................. 27 Figure 3-2. Sediment Phosphorus Concentrations in Black Lake, March 2015. ............... 28 Figure 4-1. Conceptual Water Budget for Black Lake. ........................................... 29 Figure 4-2. Black Lake Depth – Volume Relationship. ............................................ 31 Figure 4-3. Black Lake Inflows and Outflows, 2010–2012. ....................................... 32 Figure 5-1. Conceptual Phosphorus Budget for Black Lake. ..................................... 34 Figure 5-2. Black Lake External Phosphorus Inputs, 2010–2012. ................................ 38 Figure 5-3. Black Lake Summer Phosphorus Outputs, 2010–2012. .............................. 39 Figure 5-4. Monthly Black Lake Phosphorus Flux in 2010. ....................................... 39 Figure 5-5. Monthly Black Lake Phosphorus Flux in 2011. ....................................... 40 Figure 5-6. Monthly Black Lake Phosphorus Flux in 2012. ....................................... 40 iii pjj 15-05987-000 black lake p-a cntrl plan.docx EXECUTIVE SUMMARY Black Lake, located in Olympia, Washington, has high nutrient levels that result in cyanobacteria (blue-green algae) blooms. These blooms have occurred in most years since routine lake monitoring began in 1992. Water quality data collected by Thurston County since 1992 shows that Black Lake is eutrophic (high nutrients and algae) due to high phosphorus concentrations. Lake sediments are a primary source of the phosphorus during summer when it is released from iron as anoxic (no oxygen) conditions develop in the bottom waters. The excess phosphorus fuels excess cyanobacteria that float to the surface to form scums and often produce various cyanotoxins (chemicals which are toxic humans,