MILL RUN WATERSHED TMDL Blair and Cambria Counties Prepared for: Pennsylvania Department of Environmental Protection January 12, 2007 TABLE OF CONTENTS INTRODUCTION .......................................................................................................................... 1 LOCATION .................................................................................................................................... 1 SEGMENTS ADDRESSED IN THIS TMDL ............................................................................... 3 CLEAN WATER ACT REQUIREMENTS ................................................................................... 3 SECTION 303(D) LISTING PROCESS ........................................................................................ 4 BASIC STEPS FOR DETERMINING A TMDL .......................................................................... 5 SAMPLING RATIONALE ............................................................................................................ 5 WATERSHED BACKGROUND................................................................................................... 6 METALS METHODOLOGY ........................................................................................................ 6 TMDL ENDPOINTS...................................................................................................................... 8 TMDL ELEMENTS (WLA, LA, MOS)......................................................................................... 9 TMDL METALS ALLOCATION SUMMARY............................................................................ 9 MILL RUN SEGMENT WATERSHED SILTATION TMDL.................................................... 10 Reference Watershed Approach ............................................................................................... 13 Selection of the Reference Watershed...................................................................................... 13 WATERSHED ASSESSMENT AND MODELING ................................................................... 16 TMDLS......................................................................................................................................... 17 Background Pollutant Conditions............................................................................................. 17 Targeted TMDLs ...................................................................................................................... 17 Margin of Safety ....................................................................................................................... 18 Load Allocation ........................................................................................................................ 18 Adjusted Load Allocation......................................................................................................... 18 TMDL ....................................................................................................................................... 19 CALCULATION OF SEDIMENT LOAD REDUCTIONS ........................................................ 19 CONSIDERATION OF CRITICAL CONDITIONS ................................................................... 20 CONSIDERATION OF SEASONAL VARIATIONS................................................................. 20 RECOMMENDATIONS FOR IMPLEMENTATION (METALS AND SEDIMENT).............. 20 PUBLIC PARTICIPATION ......................................................................................................... 21 GIS DATA SETS.......................................................................................................................... 24 REFERENCES ............................................................................................................................. 32 TABLES Table 1. Mill Run Segments Addressed................................................................................... 1 Table 2. Applicable Water Quality Criteria............................................................................. 9 Table 3. Summary Table–Mill Run Watershed ....................................................................... 9 Table 4. Comparison Between Mill Run Segment and Racket Brook................................... 14 Table 5. Existing Sediment Loads for Mill Run Segment ..................................................... 16 Table 6. Existing Sediment Loads for Racket Brook............................................................. 17 Table 7. Targeted TMDL for the Mill Run Segment Watershed........................................... 18 Table 8. Load Allocations, Loads Not Reduced, and Adjusted Load Allocations for Mill Run Segment............................................................................................................ 19 Table 9. TMDL, MOS, LA, LNR, and ALA for Mill Run Segment..................................... 19 i Table 10. Sediment Load Allocations & Reductions for Mill Run Segment Error! Bookmark not defined. FIGURES Figure 1. Mill Run Watershed................................................................................................... 2 Figure 2. Location Map of the Mill Run Segment Watershed ................................................ 12 Figure 3. Location Map of the Reference Watershed, Racket Brook ..................................... 15 APPENDICES Appendix A. AVGWLF Model Overview & GIS-Based Derivation of Input Data .................. 22 Appendix B. AVGWLF Model Inputs for the Mill Run Segment Watershed and Racket Brook Reference Watershed ................................................................................. 25 Appendix C. Equal Marginal Percent Reduction Method.......................................................... 27 Appendix D. Equal Marginal Percent Reduction Calculations for the Mill Run Segment TMDL ................................................................................................................... 28 Appendix E. Information Sheet for the Mill Run Watershed TMDL........................................ 29 ATTACHMENTS Attachment A. Excerpts Justifying Changes Between the 1996, 1998, and 2002, Section 303(d) Lists and 2004 and 2006 Integrated Lists................................................33 Attachment B. TMDLs By Segment...........................................................................................36 Attachment C. Water Quality Data Used in TMDL Calculations...............................................42 Attachment D YSI Continuous Sonde Data ...............................................................................44 Attachment E. Comment and Response......................................................................................46 ii TMDL1 Mill Run Watershed Blair and Cambria Counties, Pennsylvania INTRODUCTION This report presents the Total Maximum Daily Load (TMDL) developed for stream segments in the Mill Run Watershed (Figure 1). This was done to address impairments noted on the 1996, 1998, and 2002 Pennsylvania Section 303(d) lists, and the 2004 and 2006 Integrated Lists required under the Clean Water Act and covers two segments on this list (Table 1). High levels of metals and siltation caused these impairments. The TMDL addresses the two metals (iron and aluminum) identified as impairing the stream from urban runoff and combined sewer overflows (CSOs) and sediment associated with small residential runoff. Table 1. Mill Run Segments Addressed State Water Plan (SWP) Subbasin: 11-A Little Juniata River and Frankstown Branch Segment Year Stream Stream Source Cause Miles ID Listed Name Code Combined Sewer Overflow 6564 1996 Mill Run 16403 Unknown 3.9 Urban Runoff/Storm Sewers 20000327- 2002 Mill Run 16403 Small Residential Runoff Siltation 0.8 1001-TAS See Attachment A, Excerpts Justifying Changes Between the 1996, 1998, and 2002 Section 303(d) lists and the 2004 and 2006 Integrated lists. The use designations for the stream segments in this TMDL can be found in PA Title 25 Chapter 93. LOCATION Mill Run flows about 8.6 miles from its headwaters to its confluence with Beaverdam Branch. Mill Run is impaired from its mouth upstream 4.7 miles, at which point, the stream no longer flows through an urban landscape (Figure 1). The watershed is located predominately in Blair County with a small section in Cambria County and drains approximately 13 square miles in State Water Plan Subbasin 11A. The aquatic life use for Mill Run is high quality cold water fisheries from its source to the Allegheny Reservoir and warm water fisheries from the reservoir to the mouth. 1 Pennsylvania’s 1996, 1998, and 2002 Section 303(d) lists were approved by the U.S. Environmental Protection Agency. The 2004 and 2006 Integrated Lists have been approved by the U.S Environmental Protection Agency. The 1996 Section 303(d) list provides the basis for measuring progress under the 1996 lawsuit settlement of American Littoral Society and Public Interest Group of Pennsylvania v. EPA. 1 Figure 1. Mill Run Watershed 2 Mill Run flows through the lower portion of Altoona City before it enters Beaverdam Branch. The stream is channelized in areas as it travels through Altoona. The Mill Run Watershed can be reached traveling on the PA Turnpike to exit 146 (US 220/I-99). Upon exiting the Turnpike, merge onto US220/I-99 N and follow this to Altoona City. Several major roads intersect the watershed including: PA-36 and PA-764 (Figure 1). SEGMENTS ADDRESSED IN THIS TMDL The Mill Run Watershed is affected by pollution from