TABLE OF CONTENTS Lower Walton Formation (Dsw) ....... 22 Page Oneonta Formation (Dgo) ........... 23 Undifferentiated Hamilton Group (Dh) .... 23 INTRODUCTION ...................... 1 Western Orange County ...... 23 PURPOSE AND SCOPE .................. 1 Eastern Orange County ....... 23 PREVIOUS INVESTIGATIONS ............. 1 Onondaga Limestone (Dou) .......... 23 MAP PREPARATION ................... 2 Helderberg Group (Dhg) ............ 24 Well Location System ............... 2 Undifferentiated Lower Devonian and ACKNOWLEDGEMENTS ................. 3 Silurian Rocks (Ds) ......... 24 LOCATION AND PHYSICAL FEATURES Undifferentiated Silurian Rocks I (Srp) .... 24 OF THE AREA .................. 3 Undifferentiated Silurian Rocks II (Sbs) ... 24 GROUND-WATER UTILIZATION ........... 3 Martinsburg Formation (On) .......... 25 Private Supplies .................. 3 Wappinger Group (OEw) ........... 25 Public Supplies ................... 4 Igneous and Metamorphic Bedrock ...... 25 GEOLOGIC HISTORY ................... 4 Undifferentiated Gneiss and Granite, OCCURRENCE AND MOVEMENT OF Granitic Gneiss (Mu and Mgu) .. 25 GROUND WATER ............... 5 Calcite and Dolomite Marble (Mb) ...... 26 Unconfined Aquifers ............... 5 EXPLORATION METHODS FOR DEVELOPING Confined Aquifers ................. 5 HIGH-YIELDING BEDROCK WELLS .. 26 WATERSHED AREA DELINEATION ......... 6 Topography .................... 27 GROUND-WATER AVAILABILITY .......... 6 Sand and Gravel Deposits ........... 27 Hydrologic Cycle ................. 6 Geologic Maps .................. 27 Water-Budget Analysis .............. 6 Fracture-Trace Analysis ............. 28 SURFICIAL SOILS ..................... 10 Federal and State Wetland Delineation .... 29 AQUIFER TYPES ..................... 10 Designation of High-Yielding Bedrock Well Sand and Gravel Aquifers ........... 10 Locations ............... 29 Bedrock Aquifers ................ 11 WATER QUALITY .................... 30 SAND AND GRAVEL AQUIFERS .......... 11 Dissolved Solids ................. 30 Glacial Till .................... 11 Iron and Manganese ............... 30 Aquifers of Glacial Origin ........... 11 Hardness ..................... 31 Alluvial Deposits ................. 12 Sodium and Chloride .............. 31 YIELD POTENTIAL OF Sulfate ....................... 32 SAND AND GRAVEL AQUIFERS .... 12 Nitrate ....................... 32 Beaverdam Brook Valley (O) ......... 12 Turbidity ..................... 32 Black Meadow Creek Valley (AA) ...... 12 Hydrogen Sulfide ................ 33 Greenwood Lake (Z) .............. 13 Radionuclides ................... 33 Manhagen Brook Valley (T) .......... 14 SURFACE WATER TREATMENT RULE ..... 34 Moodna Creek Valley (Q) ........... 14 EFFECTS OF LAND USE ON WATER QUALITY 34 Moodna Creek Valley (P) ........... 15 Waste Disposal .................. 35 Neversink-Basher Kill River Valleys (L) .. 15 Urbanization ................... 35 Pine Bush Valley (BB) ............. 16 POTENTIAL FOR WATER-QUALITY CHANGES 35 Ramapo River Valley (Y) ........... 17 GROUND-WATER EXPLORATION ......... 36 Rutgers Creek Valley (S) ............ 17 Sand and Gravel Aquifer ............ 36 Seeley Brook Valley (W) ............ 18 Bedrock Aquifers ................ 37 Shawangunk Kill Valley (M) .......... 18 CONCLUSIONS ...................... 37 Wallkill River Valley (U) ............ 19 Ground-Water Supply .............. 37 Tin Brook (I) ................... 20 Sand and Gravel Aquifers ........... 38 Wawayanda Creek Valley (V) ......... 21 Bedrock Aquifers ................ 38 Woodbury Creek Valley (X) .......... 21 Water Quality ................... 39 Additional Small Sand and Gravel RECOMMENDATIONS ................. 40 Deposits ................ 22 REFERENCES ....................... 42 YIELD POTENTIAL OF BEDROCK AQUIFERS . 22 Sedimentary Bedrock Aquifers ......... 22 TABLE OF CONTENTS (continued) LIST OF TABLES Aquifer Types in Orange County (at end of report) 15 Radon Surveillance Study of Orange County Table LIST OF FIGURES (at end of report) 1 Total Estimated Yield Capacity and Withdrawal of Wells for Existing and Proposed Public and Figure Private Water-Supply Systems in Orange County (1994) 1 Index Map 2 Estimated Present (1994) Withdrawal of 2 Location of Study Area Ground Water From Wells in Orange County 3 Physiographic Provinces 3 Estimated Recharge to the Bedrock Aquifer Per 4 Watershed in Orange County 5 Ground-Water Supply Development 4 Available Ground-Water Recharge Estimates 6 Watershed Area Delineation for the Respective Aquifers in Orange County 7 Watershed Areas of Orange County 5 Sand and Gravel Aquifer Summary 8 Generalized Hydrologic Cycle 6A Recharge Per Town 9 Recurrence of Annual Precipitation at 6B Estimated and Projected Water Demand Gardnerville, New York (1957-1993) Compared to Recharge to Bedrock Aquifers 10 Recurrence of Annual Precipitation at Under Normal and Drought Conditions Per Middletown, New York (1890-1907/1952-1993) Town 11 Recurrence of Annual Precipitation at Port 7 Estimated Recharge to Bedrock Aquifers Under Jervis, New York (1880-1855/1890-1993) Normal and Drought Conditions Per Watershed 12 Town Boundaries in Orange County 13 Significant Sand and Gravel Aquifers of Orange 8 Water Budget Analysis of Villages in Orange County County Presently Utilizing Bedrock Wells 14 Bedrock Aquifer Map 9 Summary of Sand and Gravel Deposits from the 15 Schematic Illustration of Occurrence of Ground Soil Survey of Orange County Water in Bedrock Aquifers 10 Sand and Gravel Aquifers Available for 16 Faults and Fracture Traces Development in the Respective Towns of 17 Illustration of Ground-Water Source Possibly Orange County Under the Influence of Surface Water 11 Bedrock Aquifers Available for Development in the Respective Towns of Orange County 12 Reported and Estimated Yield of Wells Appendix Completed in Bedrock Aquifers in Orange County Set 1 Sand and Gravel Aquifer Maps 13 Chemical Analyses and Maximum Contaminant Set 2 Bedrock Aquifer Maps Levels Required by NYSDOH for Community Set 3 Bedrock Aquifer Maps Water Systems 14 Water-Quality Analyses Showing Variations in Chemical Quality of Ground Water from the GROUND-WATER RESOURCES OF As with the 1972 Frimpter report, the aquifers ORANGE COUNTY, NEW YORK discussed in this report were mapped and their potential ORANGE COUNTY WATER AUTHORITY yields were estimated from currently-available GOSHEN, NEW YORK hydrogeologic data. Emphasis was placed on municipal water-supply systems in the County and on evaluating present and future water-supply demands of these systems. INTRODUCTION The GWRS also emphasizes the potential development of the bedrock aquifers in Orange County, which were not considered "dependable" sources of water supply by The Orange County Water Authority (OCWA) Frimpter (1972). retained Leggette, Brashears & Graham, Inc. (LBG) to The work on which this report is based consists conduct a Ground-Water Resources Study (GWRS) to of the following: update ground-water information and maps for the County. The purpose of the GWRS is to provide a basis for planning • Inventory of available well data and related present and future water-supply needs of the County and hydrogeologic data from 439 selected wells in the provide guidance for future development of high-yielding County. The wells were inventoried for the ground-water supplies. The GWRS indicates areas with Existing Conditions Report. inadequate or marginal water supplies and makes recommendations for development of additional ground- • Estimated present and future water demands to water supplies. the year 2020. The GWRS inventories existing ground-water supplies and potential areas for development of future • Mapping of the following layers created in supplies. Based on quantitative knowledge of the water AutoCAD files: resources that are available, local and County planners will be involved in setting development guidelines to safeguard - New York State Department of existing ground-water supplies and protect favorable Transportation (NYSDOT) base maps undeveloped areas for future development of ground-water (roads, municipal boundaries and supplies. This information will also be used to conduct names); future wellhead and aquifer protection programs. - wells inventoried in this Study; The previous plan to develop a large-scale water - State and Federal wetlands; supply for the County considered the development of a - hydrology; large surface-water supply and distribution of the water - Soil Survey (Olsson, 1981); throughout the Orange County Water Loop. The OCWA - topography; does not consider this plan to be a viable alternative for - watershed areas; development of water supply for the present and foreseeable - sand and gravel aquifers; future demands for the County. The water-supply - bedrock aquifer units; questions addressed by this report are whether ground - fracture traces and faults; water can be considered a feasible and favorable alternative - land use (Space Track, 1993); for water-supply development and whether the development - existing and potential contamination of additional ground-water supplies will be sufficient for sites; and meeting future water demands of the County. - designated locations for likely development of high-yielding bedrock PURPOSE AND SCOPE wells. The GWRS updates two previous published • Inventory of water-quality data from 84 wells in reports, "Ground-Water Basic Data, Orange and Ulster the County to determine water quality developed Counties, New York" by Frimpter (1970) and "Ground- from the respective aquifer types. Water