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REPORT Assessment of Water Quality Impacts from Potential Land Development Deep Creek Lake Garrett County, Maryland URCES MANAGEMENT URCES May 2007 ENVIRONMENTAL RESO ENVIRONMENTAL Environmental Resources Management 350 Eagleview Blvd., Suite 200 Exton, PA 19341 www.erm.com TABLE OF CONTENTS TABLE OF CONTENTS 1 LIST OF FIGURES 2 LIST OF TABLES 4 1. SUMMARY 6 2. DEEP CREEK LAKE DATASETS AND WATERSHED LOADS 8 2.1. DATA INVENTORY 8 2.1.1. GIS and Mapping 9 2.1.2. Water Quality 9 2.1.3. Flow Data 11 2.1.4. Water Surface Elevation Data 14 2.1.5. Land Use 14 2.2. RUNOFF FLOW AND LOAD ESTIMATES 16 2.2.1. Runoff Flow Estimates 16 2.2.2. Load Estimation Methodology 18 3. VOLLENWEIDER ANALYSIS 31 4. ANALYSIS OF FIELD DATA 33 4.1. CARLSON’S TSI SCORES 33 4.2. THE NITROGEN TO PHOSPHORUS RATIO 37 5. BATHTUB MODEL APPLICATION AND RESULTS 40 5.1. MODEL INPUTS AND ASSUMPTIONS 40 5.1.1. Parameters and Constants 40 5.1.2. Precipitation Data 42 5.1.3. Land Use and NPS Data 43 5.1.4. Algorithm Selection 44 5.2. MODEL RESULTS AND EUTROPHICATION ASSESSMENT 46 6. CE-QUAL-W2 MODEL APPLICATION AND RESULTS 51 6.1. BATHYMETRY, GRID AND ENGINEERING FEATURES 52 6.2. TIME VARYING BOUNDARY CONDITION DATA 56 6.2.1. Meteorological data 56 6.2.2. Inflow and outflow rates and the water surface elevation 57 6.2.3. Inflow temperatures 58 6.3. CE-QUAL-W2 SIMULATIONS AND RESULTS 59 6.3.1. Circulation patterns and stratification 59 6.3.2. Residence Time and Water Age 62 6.3.3. Total suspended solids 64 7. CONCLUSIONS AND RECOMMENDATIONS 70 8. REFERENCES 73 APPENDIX A: GLOSSARY 76 APPENDIX B: METHODOLOGY FOR DEVELOPING LAND USE ACREAGES 77 APPENDIX C: WATER QUALITY DATA 78 APPENDIX D: COMMENTS RECEIVED AND RESPONSES 79 DEEP CREEK LAKE WATER QUALITY ASSESSMENT PAGE 1 LIST OF FIGURES Figure 2-1 Deep Creek Lake and tributaries .................................................... 8 Figure 2-2 Youghiogheny River Flow Record ............................................... 12 Figure 2-3 Youghiogheny Watershed and USGS Station 3076500.............. 13 Figure 2-4 USGS Flow gauges in the vicinity of Deep Creek Lake (source: USGS, 2006)......................................................................................................... 14 Figure 2-5 Existing and potential land uses for Deep Creek Lake (source: MDP 2006)........................................................................................................... 15 Figure 2-6 Deep Creek Lake sub-watersheds ................................................ 18 Figure 2-7 Existing and projected total phosphorus NPS loads for Deep Creek Lake .......................................................................................................... 29 Figure 2-8 Existing and projected total nitrogen NPS loads for Deep Creek Lake...................................................................................................................... 29 Figure 3-1 Vollenweider analysis for each scenario (source: Vollenweider, 1975) ..................................................................................................................... 32 Figure 4-1 Deep Creek Lake chlorophyll a concentrations (source: MDE) 34 Figure 4-2 TSI scores based on 2000-2003 chlorophyll a values (source: MDE).................................................................................................................... 35 Figure 4-3 Deep Creek Lake secchi depth measurements (source: MDE). 36 Figure 4-4 TSI scores based on 2000-2003 secchi depth values (source: MDE).................................................................................................................... 36 Figure 4-5 Deep Creek Lake total phosphorus concentrations (source: MDE).................................................................................................................... 37 Figure 4-6 TSI scores based on 2000-2003 total phosphorus values (source: MDE).................................................................................................................... 37 Figure 4-7 Total nitrogen vs. total phosphorus – Deep Creek Lake (1999 to 2000) ..................................................................................................................... 38 Figure 4-8 Total nitrogen to total phosphorus ratio frequency histogram 39 Figure 5-1 Precipitation record (2002-2005) at NCDC Station Oakland 1 SE, Oakland, Maryland............................................................................................ 42 Figure 5-2 Total yearly precipitation (2002-2005) at NCDC Station Oakland 1 SE, Oakland, Maryland .................................................................................. 43 Figure 6-1 Deep Creek Lake and tributaries .................................................. 53 Figure 6-2 Deep Creek Lake CE-QUAL-W2 grid showing longitudinal segments.............................................................................................................. 55 Figure 6-3 Side view of the grid representing the main branch of Deep Creek Lake .......................................................................................................... 55 Figure 6-4 Summary of total inflow (cms) to Deep Creek Lake for 2005... 57 Figure 6-5 Hydropower outflows (cms) from Deep Creek Lake for 2005 . 58 Figure 6-6 Observed (blue) and computed (red) water surface elevation. 58 Figure 6-7 Observed and computed tributary temperatures. ..................... 59 Figure 6-8 Typical winter temperatures in Deep Creek Lake (19 Jan 2005) ............................................................................................................................... 61 DEEP CREEK LAKE WATER QUALITY ASSESSMENT PAGE 2 Figure 6-9 Typical early spring temperatures in Deep Creek Lake (12 April 2005) ..................................................................................................................... 61 Figure 6-10 Typical, stratified, mid-summer temperatures in Deep Creek Lake (15 August 2005) ....................................................................................... 62 Figure 6-11 Typical late fall (near-overturn) temperatures in Deep Creek Lake (21 Oct 2005) .............................................................................................. 62 Figure 6-12 Water age during a period of high inflow................................. 63 Figure 6-13 Water age during a period of low inflow and stratification ... 64 Figure 6-14 Upstream TSS concentrations – Base and Moderate Development Scenarios..................................................................................... 67 Figure 6-15 Downstream TSS concentrations – Base and Moderate Development Scenarios..................................................................................... 67 Figure 6-16 Upstream TSS concentrations – Base and Rapid Development Scenarios.............................................................................................................. 68 Figure 6-17 Downstream TSS concentrations – Base and Rapid Development Scenarios..................................................................................... 68 Figure 6-18 Upstream TSS concentrations – Base and Capacity Cases...... 69 Figure 6-19 Upstream TSS concentrations – Base and Capacity Cases...... 69 DEEP CREEK LAKE WATER QUALITY ASSESSMENT PAGE 3 LIST OF TABLES Table 2-1 2005 estimated Deep Creek Lake watershed land use areas (source: MDP)..................................................................................................... 15 Table 2-2 Sub-watershed drainage areas surrounding Deep Creek Lake . 16 Table 2-3 USGS station summary .................................................................... 17 Table 2-4 2002 CBP Phase 5 Watershed Model Land Use in the Deep Creek Lake Watershed, Garrett Co., MD ................................................................... 20 Table 2-5 Comparison of MDP to CBP land use area estimates.................. 20 Table 2-6 CBP land use proportions by MDP Land Use .............................. 22 Table 2-7 CBP nutrient and solids nonpoint source load rates (Mandel, 2006) ..................................................................................................................... 22 Table 2-8 Existing Case (2005) – Deep Creek Lake sub-watershed land use areas ..................................................................................................................... 23 Table 2-9 Moderate Growth Scenario – Deep Creek Lake sub-watershed land use areas ..................................................................................................... 24 Table 2-10 Rapid Growth Scenario – Deep Creek Lake sub-watershed land use areas .............................................................................................................. 25 Table 2-11 Capacity Analysis Scenario – Deep Creek Lake sub-watershed land use areas ..................................................................................................... 26 Table 2-12 Existing Case (2005) – Nonpoint source load estimates by sub- watershed............................................................................................................ 27 Table 2-13 Moderate Growth Scenario – Nonpoint source load estimates by sub-watershed............................................................................................... 27 Table 2-14 Rapid Growth Scenario – Nonpoint source load estimates by sub-watershed .................................................................................................... 28 Table

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