Willamette Basin TMDL: Clackamas Subbasin September 2006 CHAPTER 6: CLACKAMAS SUBBASIN TMDL Table of Contents WATER QUALITY SUMMARY......................................................................................... 3 Reason for action ........................................................................................................................................................... 3 Who helped us................................................................................................................................................................ 3 Subbasin 303(d) Listed Parameters Addressed by a TMDL ..................................................................................... 4 SUBBASIN OVERVIEW ................................................................................................... 5 Land Use and Ownership.............................................................................................................................................. 6 Watershed Descriptions ................................................................................................................................................ 7 Upper Clackamas Watershed....................................................................................................................................... 7 Collawash River and Hot Springs Fork Drainages ...................................................................................................... 8 Oak Grove Fork........................................................................................................................................................... 8 Roaring River Watershed ............................................................................................................................................ 8 Fish Creek Watershed.................................................................................................................................................. 9 South Fork Clackamas Watershed............................................................................................................................. 10 North Fork Clackamas............................................................................................................................................... 10 Lower Clackamas Tributaries.................................................................................................................................... 10 Clear Creek Watershed.............................................................................................................................................. 10 Richardson and Rock Creeks..................................................................................................................................... 11 Eagle Creek Drainage................................................................................................................................................ 11 Water Use..................................................................................................................................................................... 12 Flow Gauges.............................................................................................................................................................. 15 CLACKAMAS SUBBASIN TEMPERATURE TMDL ...................................................... 16 Temperature Pollutant Identification........................................................................................................................ 16 Waterbodies Listed for Temperature ........................................................................................................................ 17 Pollutant Identification ............................................................................................................................................... 17 Beneficial Use Identification ....................................................................................................................................... 18 Salmonid Stream Temperature Requirements ........................................................................................................... 18 Target Criteria Identification..................................................................................................................................... 18 Existing Heat Sources.................................................................................................................................................. 21 Nonpoint Sources of Heat.......................................................................................................................................... 21 Point Sources of Heat ................................................................................................................................................ 21 Temperature TMDL Approach Summary................................................................................................................ 25 Temperature TMDL Analytical Methods Overview ................................................................................................ 25 Seasonal Variation....................................................................................................................................................... 27 Loading Capacity......................................................................................................................................................... 31 Critical Condition ...................................................................................................................................................... 31 Allocations.................................................................................................................................................................... 32 Wasteload Allocations ................................................................................................................................................. 32 Waste Load Allocations in Small Streams................................................................................................................. 32 Excess Load.................................................................................................................................................................. 37 Surrogate Measures..................................................................................................................................................... 37 OREGON DEPARTMENT OF ENVIRONMENTAL QUALITY 6-1 Willamette Basin TMDL: Clackamas Subbasin September 2006 Clackamas Subbasin Shade Curves ........................................................................................................................... 38 Margin of Safety .......................................................................................................................................................... 43 Reserve Capacity ......................................................................................................................................................... 44 CLACKAMAS SUBBASIN BACTERIA TMDL ............................................................... 45 Beneficial Use Identification ....................................................................................................................................... 47 Target Criteria Identification..................................................................................................................................... 47 Analytical Approach.................................................................................................................................................... 48 Existing Sources........................................................................................................................................................... 49 Nonpoint Sources of Bacteria.................................................................................................................................... 49 Point Sources of Bacteria........................................................................................................................................... 49 Seasonal Variation....................................................................................................................................................... 51 Current Conditions...................................................................................................................................................... 51 Cow Creek................................................................................................................................................................. 54 Sieben Creek (Drainage Ditch).................................................................................................................................. 55 Rock Creek Watershed .............................................................................................................................................. 57 Deep Creek, North Fork Deep Creek, Tickle Creek.................................................................................................. 58 Bargfeld Creek........................................................................................................................................................... 62 Load Duration Curve .................................................................................................................................................