STATE OF RHODE ISLAND DEPARTMENT OF ENVIRONMENTAL MANAGEMENT Office of Water Resources 235 Promenade Street, Providence, RI 02908 FINAL Pathogen TMDL for Saugatucket River, Mitchell Brook, Rocky Brook and Indian Run Brook May 16, 2003 i Table of Contents LIST OF ACRONYMS AND TERMS ............................................................................................... a EXECUTIVE SUMMARY ................................................................................................................. c 1. Description of Waterbody, Priority Ranking, Pollutant of Concern, and Pollutant Sources ........... c 2. Description of Applicable Water Quality Standards........................................................................d 3. Total Maximum Daily Load Analysis ............................................................................................. e 4. Establishing a numeric water quality target......................................................................................f 5. Required reductions (Load Allocation/Waste Load Allocation).......................................................f 6. Strengths and Weaknesses in the TMDL Process............................................................................g 7. Implementation Plans........................................................................................................................j 8. Monitoring Plan for TMDLs Developed Under the Phased Approach............................................n 9. Public Participation..........................................................................................................................n 1.0 INTRODUCTION .........................................................................................................................1 1.1 Background ................................................................................................................................1 1.2 Pollutant of Concern...................................................................................................................1 1.3 Applicable Water Quality Standards..........................................................................................3 1.4 Designated Uses .........................................................................................................................3 1.5 Water Quality Criteria................................................................................................................4 2.0 DESCRIPTION OF THE WATERBODIES .................................................................................4 2.1 Saugatucket River ......................................................................................................................4 2.2 Indian Run Brook.......................................................................................................................5 2.3 Rocky Brook ..............................................................................................................................5 2.4 Mitchell Brook .........................................................................................................................10 2.5 Unnamed Tributaries................................................................................................................10 3.0 DESCRIPTION OF THE SAUGATUCKET RIVER WATERSHED........................................12 3.1 Watershed Description and Location .......................................................................................12 3.2 Topography ..............................................................................................................................12 3.3 Climate .....................................................................................................................................14 3.4 Ecology.....................................................................................................................................14 3.4.1 Forest Habitat ...................................................................................................................................14 3.4.2 Wetland Habitat................................................................................................................................14 3.4.3 Wetland Wildlife ..............................................................................................................................15 3.5 Geology ....................................................................................................................................15 3.5.1 Geomorphic Features........................................................................................................................15 3.5.2 Geology ............................................................................................................................................16 3.5.3 Soils ..................................................................................................................................................16 3.6 Land Use ..................................................................................................................................18 3.7 Sanitary Connections, Stormwater System, and Water Supply................................................18 3.7.1 Sanitary Connections........................................................................................................................18 3.7.2 Storm Sewer System.........................................................................................................................19 3.7.3 Water Supply .................................................................................................................................22 ii 4.0 DESCRIPTION OF WATER QUALITY MONITORING ACTIVITIES..................................22 4.1 1996-1999 URI Study................................................................................................22 4.1.1 Dry Weather Fecal Coliform Data....................................................................................................24 4.1.2 Wet weather Fecal Coliform Monitoring..........................................................................................24 4.1.3 Interim Survey ..................................................................................................................................27 4.2 RIDEM Supplementary Monitoring (2000) .............................................................................30 4.2.1 Dry Weather Data.............................................................................................................................30 4.2.2 Wet Weather Data.............................................................................................................................31 5.0 WATER QUALITY CHARACTERIZATION ...........................................................................43 5.1 Dry Weather Characterization..................................................................................................43 5.1.1 URI 1997 Water Quality Study ........................................................................................................43 5.1.2 RIDEM Supplementary Monitoring (2000)......................................................................................43 5.2 Wet Weather Characterization .................................................................................................45 5.2.1 URI Water Quality Study (1997)......................................................................................................45 5.2.2 RIDEM Supplementary Monitoring (2000)......................................................................................45 5.2.3 URI & RIDEM Combined Data Sets................................................................................................46 5.3 Other Water Quality Data.........................................................................................................46 5.4 Weighted Average Approach ...................................................................................................46 5.5 Calculation of the Percent Exceedance Value..........................................................................47 6.0 WATER QUALITY IMPAIRMENTS ........................................................................................48 6.1 Rocky Brook ............................................................................................................................50 6.1.1Rocky Brook Segment 3 (Headwaters to Curtis Corner Road) .........................................................50 6.1.2 Rocky Brook Segment 2 (Curtis Corner Road to Rocky Brook Reservoir outlet) ...........................51 6.1.3 Segment 1(Rocky Brook Reservoir outlet to Railroad St.)...............................................................52 6.2 Indian Run Brook.....................................................................................................................53 6.2.1 Segment 2 (Headwaters to Indian Run Reservoir outlet)..................................................................53 6.2.2 Segment 1 (Indian Run Reservoir outlet to Indian Run Brook mouth at Peace Dale Guild)............55 6.3 Mitchell Brook .........................................................................................................................57 6.3.1 Segment 1 (Headwaters to Rose Hill Transfer Station)....................................................................57 6.4 Saugatucket River & Unnamed Tributaries .............................................................................59