Final Draft 9/07 Total Maximum Daily Loads for Phosphorus To Address 9 Eutrophic Ponds in Rhode Island _______________________________ Almy Pond, Newport Brickyard Pond, Barrington Gorton Pond, Warwick North Easton Pond, Middletown, Newport Roger Williams Park Ponds, Providence Sand Pond, Warwick Spectacle Pond, Cranston Upper Dam Pond, Coventry Warwick Pond, Warwick Prepared By: Office of Water Resources Rhode Island Department of Environmental Management 235 Promenade St. Providence, RI 02908 September, 2007 I Final Draft 9/07 TABLE OF CONTENTS TABLE OF CONTENTS..................................................................................................................... I TABLE OF FIGURES ...................................................................................................................... III LIST OF TABLES..............................................................................................................................IV LIST OF ACRONYMS AND TERMS .............................................................................................VI LIST OF ACRONYMS AND TERMS .............................................................................................VI ABSTRACT .................................................................................................................................... VIII 1.0 INTRODUCTION ...........................................................................................................................1 1.1 Scope and Purpose of Eutrophic Pond TMDLs............................................................................1 1.2 Pollutants of Concern and Applicable Criteria............................................................................1 1.3 Priority Ranking ...........................................................................................................................3 1.4 Antidegradation Policy.................................................................................................................3 2.0 WATERSHED/WATERBODY DESCRIPTIONS .........................................................................4 2.1 Almy Pond.....................................................................................................................................4 2.2 Brickyard Pond.............................................................................................................................5 2.3 Gorton Pond .................................................................................................................................6 2.4 North Easton Pond .......................................................................................................................7 2.5 Roger Williams Park Ponds..........................................................................................................8 2.6 Sand Pond.....................................................................................................................................9 2.7 Spectacle Pond .............................................................................................................................9 2.8 Upper Dam Pond........................................................................................................................10 2.9 Warwick Pond.............................................................................................................................11 3.0 CURRENT WATER QUALITY CONDITIONS ..........................................................................12 3.1 Almy Pond...................................................................................................................................13 3.2 Brickyard Pond...........................................................................................................................14 3.3 Gorton Pond ...............................................................................................................................16 3.4 North Easton Pond .....................................................................................................................19 3.5 Roger Williams Park Ponds........................................................................................................20 3.6 Sand Pond...................................................................................................................................22 3.7 Spectacle Pond ...........................................................................................................................24 3.8 Upper Dam Pond........................................................................................................................26 3.9 Warwick Pond.............................................................................................................................27 4.0 POLLUTION SOURCES ..............................................................................................................29 4.1 Overview.....................................................................................................................................29 4.2 Stormwater Runoff......................................................................................................................29 4.3 Waterfowl and Other Wildlife.....................................................................................................30 4.4 Wastewater .................................................................................................................................30 4.5 Streambank and Shoreline Erosion ............................................................................................31 4.6 Atmospheric................................................................................................................................32 4.7 Internal Loading.........................................................................................................................32 4.8 Almy Pond...................................................................................................................................36 4.9 Brickyard Pond...........................................................................................................................37 4.10 Gorton Pond ...............................................................................................................................38 4.11 North Easton Pond .....................................................................................................................39 4.12 Roger Williams Pond..................................................................................................................40 i Final Draft 9/07 4.13 Sand Pond...................................................................................................................................42 4.14 Spectacle Pond ...........................................................................................................................43 4.15 Upper Dam Pond........................................................................................................................44 4.16 Warwick Pond.............................................................................................................................46 5.0 TMDL ANALYSIS........................................................................................................................47 5.1 Margin of Safety (MOS)..............................................................................................................47 5.2 Critical Conditions and Seasonal Variation...............................................................................47 5.3 Numeric Water Quality Target ...................................................................................................47 5.4 Technical Analysis......................................................................................................................50 5.5 Existing Waterbody Loads..........................................................................................................51 5.6 Loading Capacity and Allocation of Allowable Loading ...........................................................51 6.0 IMPLEMENTATION....................................................................................................................55 6.1 Storm Water Management ..........................................................................................................55 6.2 Structural Stormwater BMPs......................................................................................................63 6.3 Waterfowl Control ......................................................................................................................64 6.4 Internal Phosphorus Control......................................................................................................65 6.5 Specific Implementation Activities..............................................................................................66 6.5.1 Almy Pond ...........................................................................................................................66 6.5.2 Brickyard Pond ....................................................................................................................67 6.5.3 Gorton Pond .........................................................................................................................69 6.5.4 North Easton Pond ...............................................................................................................71