Evaluation of Groundwater Resources of Bernards Township, Somerset County, New Jersey M2 Associates Inc. 56 Country Acres Drive Hampton, New Jersey 08827 EVALUATION OF GROUNDWATER RESOURCES OF BERNARDS TOWNSHIP SOMERSET COUNTY, NEW JERSEY APRIL 11, 2008 Prepared for: Bernards Township 1 Collyer Lane Basking Ridge, NJ 07920 Prepared by: Matthew J. Mulhall, P.G. M2 Associates Inc. 56 Country Acres Drive Hampton, New Jersey 08827-4110 908-238-0827 Fax: 908-238-0830 EVALUATION OF GROUNDWATER RESOURCES OF BERNARDS TOWNSHIP SOMERSET COUNTY, NEW JERSEY TABLE OF CONTENTS INTRODUCTION............................................................................................................. 1 GEOLOGY ...................................................................................................................... 5 PHYSIOGRAPHIC PROVINCE ............................................................................................ 5 SURFACE WATER .......................................................................................................... 6 Watersheds............................................................................................................. 6 Stream Classifications........................................................................................... 7 Headwaters............................................................................................................. 9 SOILS ......................................................................................................................... 10 BEDROCK.................................................................................................................... 13 Formations............................................................................................................ 13 Highlands ........................................................................................................... 13 Piedmont ............................................................................................................ 16 Structure ............................................................................................................... 17 Secondary Porosity ............................................................................................. 17 Faults .................................................................................................................... 17 Bedding/Jointing.................................................................................................. 18 GLACIAL DEPOSITS...................................................................................................... 19 GROUNDWATER SYSTEMS ....................................................................................... 20 STORAGE AND TRANSMISSION CAPABILITY.................................................................... 20 PRECAMBRIAN IGNEOUS AND METAMORPHIC ROCKS...................................................... 21 Location ................................................................................................................ 21 Aquifer Characteristics........................................................................................ 21 FELTVILLE FORMATION................................................................................................. 24 Location ................................................................................................................ 24 Aquifer Characteristics........................................................................................ 24 PREAKNESS BASALT.................................................................................................... 25 Location ................................................................................................................ 25 Aquifer Characteristics........................................................................................ 25 TOWACO FORMATION................................................................................................... 26 Location ................................................................................................................ 26 ii Aquifer Characteristics........................................................................................ 26 HOOK MOUNTAIN BASALT ............................................................................................ 27 Location ................................................................................................................ 27 Aquifer Characteristics........................................................................................ 27 BOONTON FORMATION ................................................................................................. 27 Location ................................................................................................................ 27 Aquifer Characteristics........................................................................................ 28 HYDROGEOLOGIC ZONES ............................................................................................. 28 AQUIFER RECHARGE.................................................................................................... 30 Hydrologic Cycle.................................................................................................. 30 Water Balance.................................................................................................... 30 Precipitation........................................................................................................ 32 Surface-Water Runoff......................................................................................... 34 Evapotranspiration.............................................................................................. 35 Groundwater Runoff ........................................................................................... 36 Groundwater Recharge Methods........................................................................ 37 Groundwater....................................................................................................... 37 Baseflow............................................................................................................. 38 Hydrograph Separation ...................................................................................... 38 Posten (1984) Method ........................................................................................ 39 7Q10/MA7CD10 ................................................................................................. 40 NJGS Modified Method ...................................................................................... 41 Groundwater Recharge Rates............................................................................. 44 Precambrian Igneous and Metamorphic Rocks.................................................. 44 Jurassic Igneous and Metamorphic rocks .......................................................... 46 Jurassic Sedimentary rocks................................................................................ 50 WATER SUPPLY.......................................................................................................... 52 DEMAND ..................................................................................................................... 52 DEPENDABLE YIELD..................................................................................................... 54 Definition............................................................................................................... 54 Drought Effects and Recharge............................................................................ 54 Planning Threshold.............................................................................................. 56 DWELLING UNIT DENSITIES........................................................................................... 57 SEWER SERVICE AREA................................................................................................. 58 NITRATE DILUTION ....................................................................................................... 60 Nitrate.................................................................................................................... 60 Existing Regulations............................................................................................ 60 Proposed Regulations ......................................................................................... 61 iii Trela-Douglas Model............................................................................................ 62 Acceptance......................................................................................................... 62 Assumptions....................................................................................................... 62 Equation ............................................................................................................. 63 CONCLUSIONS............................................................................................................ 65 REFERENCES.............................................................................................................. 70 TABLES 1. Watersheds, Streams, and Surface-Water Classifications in Bernards Township, Somerset County, New Jersey. 2. Types, Slopes, Approximate Areas, and Septic Limitations of Soils in Bernards Township, Somerset County, New Jersey. 3. Bedrock Types and Approximate Areas Beneath Bernards