GROUNDWATER EXPLORATION AND DEVELOPMENT PROGRAM Results of Phase I and Phase II Investigations STAFFORD FARM PROPERTY FAUQUIER COUNTY, VIRGINIA May 2014 Presented to: Mr. Paul S. McCulla Fauquier County EMERY & GARRETT GROUNDWATER INVESTIGATIONS, LLC 56 Main Street • P.O. Box 1578 Meredith, New Hampshire 03253 New England Mid-Atlantic South Atlantic Emery & Garrett Groundwater Investigations, LLC 56 Main Street • P.O. Box 1578 Meredith, New Hampshire 03253 (603) 279-4425 www.eggi.com Fax (603) 279-8717 May 13, 2014 Mr. Paul S. McCulla Fauquier County Administrator 10 Hotel Street 2nd Floor Warrenton, VA 20186 Dear Paul, Emery & Garrett Groundwater Investigations, LLC (EGGI) is pleased to present to you the following report that summarizes Phases I and II of Emery & Garrett Groundwater Investigations, LLC’s (EGGI’s) groundwater exploration and development program conducted at Stafford Farm in Fauquier County, Virginia. We hope you find the information contained herein responsive to your needs. If you have any questions regarding this material, please do not hesitate to contact us. Best regards, Kenneth C. Hardcastle, P.G. Mark B. Wingsted Senior Structural Geologist Geologist Emery & Garrett Groundwater Investigations, LLC 56 Main St. • P.O. Box 1578 Meredith, New Hampshire 03253 (603) 279-4425 www.eggi.com Fax (603) 279-8717 GROUNDWATER EXPLORATION AND DEVELOPMENT PROGRAM Results of Phase I and Phase II Investigations Stafford Farm Property Fauquier County, Virginia May 2014 TABLE OF CONTENTS Page I. INTRODUCTION..............................................................................................................1 II. PHASE I INVESTIGATIONS ..........................................................................................2 A. Summary .................................................................................................................2 B. Defining the Hydrogeologic Conditions ...............................................................2 III. PHASE II INVESTIGATIONS ........................................................................................7 A. Geophysical Methods .............................................................................................7 B. Findings of the Magnetometer/VLF Surveys ......................................................8 C. Findings of the ABEM Resistivity Surveys ..........................................................9 D. Results .....................................................................................................................9 IV. RECOMMENDATIONS ...................................................................................................9 V. LIMITATIONS ................................................................................................................11 VI. REFERENCES .................................................................................................................11 FIGURE Figure 1 Topographic Setting of Stafford Farm APPENDICES Appendix A Environmental Data Resources, Inc. Report (EDR) on Compact Disc Appendix B Magnetometer/VLF Surveys and Electrical Resistivity Surveys PLATES Plate 1 Geophysical Surveys and Proposed Exploratory Test Well Locations Plate 2 Bedrock Geology, Lineaments, Existing Wells, and Potential Threats to Groundwater Quality Emery & Garrett Groundwater Investigations, LLC 56 Main Street • P.O. Box 1578 Meredith, New Hampshire 03253 (603) 279-4425 www.eggi.com Fax (603) 279-8717 GROUNDWATER EXPLORATION AND DEVELOPMENT PROGRAM Results of Phase I and Phase II Investigations Stafford Farm Property Fauquier County, Virginia May 2014 I. INTRODUCTION This report summarizes Phases I and II of Emery & Garrett Groundwater Investigations, LLC (EGGI’s) groundwater investigation conducted at Stafford Farm, located in Fauquier County, Virginia (Figure 1). The intent of this investigation is to assess the potential for developing a public potable supply well(s) as a source of drinking water for proposed County administration buildings. Additional water supply demands at Stafford Farm may be needed in the future, as development plans are subject to change. The first part of this report summarizes the data collection and analysis conducted in the Phase I study. The second portion of this report reviews the geophysical investigations (Phase II). Data collected from the first two Phases of this groundwater development program were analyzed and resulted in the selection of nine Exploratory Test Well sites. These well sites are identified as STA-1, STA-2, STA-3, STA-4, STA-5, STA-6, STA-7, STA-8, and STA-9. Subsequent Phases of this Groundwater Exploration and Development Program will include the following: Phase III Drill exploratory test wells at identified geologic target sites. Phase IV Convert highest yielding test wells to larger-diameter production wells. Phase V Conduct long-term yield and water quality tests on production wells in accordance with Fauquier County regulations. Phase VI Prepare final Groundwater Use Management Plan, submittal of Hydrogeological Report, and Obtain Final Groundwater Withdrawal Permits, as needed. Groundwater Exploration and Development–Phases I and II–Stafford Farm Property Page 2 II. PHASE I INVESTIGATIONS A. Summary The intent of the Phase I investigation was to conduct a hydrogeologic analysis/assessment of the potential availability of groundwater resources within the Stafford Farm Project Site. Work efforts completed in Phase I included: 1) Detailed investigation of the local bedrock geology: Detailed geologic field mapping was carried out to determine bedrock type and bedrock fracture characteristics that may enhance groundwater flow. 2) Delineation of fractured bedrock aquifers with the help of the following methods: a) Lineament analysis (e.g., measurement of lineament length and orientation, assessment of lineament coincidence between one aerial platform and another, and correlation of lineaments to observed bedrock fractures). b) Fracture characterization within available bedrock exposures. 3) Identification of contributing watersheds. 4) Location of contaminant threats/existing land uses proximal to Stafford Farm that could potentially degrade groundwater quality. 5) Compilation and evaluation of data on existing wells within the Study Area. B. Defining the Hydrogeologic Conditions 1) Bedrock Geology Groundwater resources must be derived from available bedrock aquifers within the project site. Groundwater extracted from fractured bedrock aquifers is directly influenced by the bedrock’s inherent chemical and physical characteristics. The inherent hydrogeologic factors known to most strongly influence the quality and quantity of groundwater derived from bedrock aquifers are: 1) the degree to which rock units are layered, foliated, or bedded; 2) the dip of the layering; 3) the presence of geologic contact surfaces of contrasting rock types; and 4) the chemical composition of the rocks. Emery & Garrett Groundwater Investigations, LLC Groundwater Exploration and Development–Phases I and II–Stafford Farm Property Page 3 The geology of the Study Area was investigated through a detailed program of geologic field mapping to provide insights into the spatial variation of the hydrogeologic factors listed above. A result of the mapping program was the compilation of a geologic base map for the Study Area (Plate 1, View A). This map was compiled through the evaluation of soil exposures and rock “float”1 identified by EGGI geologists within the Study Area. The findings of EGGI’s evaluations supplemented geologic mapping previously conducted by others proximal to the project site (Rader et al, 1993; Geologic Map of Virginia). The existing geologic maps and EGGI's mapping indicate that the project site is underlain by greenstone of the Catoctin Formation. The greenstone is very poorly exposed at Stafford Farm. However, based on our field investigations, it was determined that the greenstone is fine- to medium-grained, weakly foliated, and tends to have a massive appearance. Epidote, pyrite, and magnetite often occur as accessory minerals. Stafford Farm is located on the eastern limb of the Blue Ridge Anticlinorium. In this area, the foliation within the bedrock typically trends north-northwest and dips steeply (85 degrees) toward the west (Plate 1, View A). No faults were identified in the immediate confines of the project area. Additional insights about the subsurface bedrock geology were gained from the results of the geophysical surveys (discussed in Section III). 2) Delineation of Fractured Bedrock Aquifers a) Introduction Besides being dependent on the physical and chemical composition of the bedrock units, the capacity of bedrock to be water bearing also depends on the occurrence of fractures, faults, or other bedrock discontinuities that provide avenues for the transmission of groundwater. The occurrence of bedrock discontinuities imparts secondary permeability to the rocks within the Study Area. Secondary permeability typically provides the main mechanism for groundwater movement in rocks. EGGI used a two-fold approach in investigating these secondary characteristics: 1) remote-sensing analysis of the site using multiple scales and types of aerial photography and imagery; and 2) measurement of available bedrock fracture characteristics contained within bedrock exposures present in the Study Area. It should be noted that the determination of secondary characteristics is separate and distinct from the evaluation of the bedrock’s inherent capability