Geology and Ground Water in the Farmington-Granby Area Connecticut GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1661 Prepared in cooperation with the Connecticut Water Resources Commission Geology and Ground Water in the Farmington-Granby Area Connecticut By ALLAN D. RANDALL G.EOLOGICAL SURVEY WATER-SUPPLY PAPER 1661 Prepared in cooperation with the Connecticut floater Resources Commission UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1964 UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director The U.S. Geological Survey Library catalog card for this publication appears after page 129. For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 CONTENTS Page Abstract________________________________________________________ 1 Introduction._____________________________________________________ 2 Purpose and scope of investigation____________________________ 2 Location and areal extent______-_____-___-_______-_-_--____--_ 3 Previous investigations.-______________________________________ 3 Methods of investigation,______________________________________ 6 Acknowledgments. ____________________________________________ 6 Well-numbering system._______________________________________ 7 Map-location system._________________________________________ 7 Geography ________ ________________________________________________ 8 Physiography and drainage.__________________________________ 8 Climate._____________________________________________________ 11 Population___ _______________________________________________ 13 Geology._____________ _ __________________________________________ 14 Geologic units______________________________________________ 14 Geologic history______________________________________________ 14 Preglacial history________________________________________ 14 Glaciation._______________________________________________ 16 Deglaciation_ _____________________________________________ 17 Postglacial history_________________________________________ 19 Physical characteristics and water-yielding properties of the geologic units__ 19 Consolidated rocks___________________________________________ 19 Crystalline rocks of pre-Triassic age.________________________ 19 Areal distribution and thickness.________________________ 20 Lithology_____________________________________________ 20 Stratigraphic relations_________________________________ 21 Water-yielding properties._____________________________ 22 Newark group_____________________________________________ 27 Areal distribution and thickness.________________________ 27 Lithology___________________________________________ 29 Stratigraphic relations..______________________________ 31 Water-yielding properties_________________-___-______-__ 31 Unconsolidated deposits._______________________________________ 44 Ground-moraine and drumlin deposits_______________________ 44 Areal distribution and .thickness __________-_____-_____--- 44 Lithology__ ______._-_______-_______________------_-_ 45 Stratigraphic relations___--_-----_----_---_--__-----_-_- 47 Water-yieiding properties,___________________-_--__---_- 48 Ice-contact deposits._______________________________________ 50 Areal distribution and thickness.________________________ 50 Lithology __ _ _-_-_________-___________--__--_------_- 51 Stratigraphic relations.----_______________--____-__---__ 56 Water-yielding properties..________________--__--_--_--_ 56 Valley-train deposits. _ ________________-_-______-_--__-----_ 59 Areal distribution and thickness.__ _____-_-__--_-___-___ 59 Lithology________-________-______-___---_-_---_----- 60 Stratigraphic relations___ _ ____________ _______________ 62 Water-yielding properties______-_____-___-_____------- ._ 62 in IV CONTENTS Physical characteristics and water-yielding properties, etc. Continued Consolidated rocks Continued Page Alluvial deposits_______________-____________--___-----_-- 65 Areal distribution and thickness._______--___---_--_----_ 65 Lithology_______________________________________ 66 Water-yielding properties.--________________---_------__ 67 Ground-water availability in the stratified drift and alluvial deposits ________________________________________________ 68 Ground water.____________________________________________________ 69 Occurrence ___________________________________________________ 69 Recharge and discharge._______________________________________ 72 Recharge._ _______________________________________________ 72 Discharge._______________________________________________ 74 Use of ground water.__________________________________________ 78 Water-level fluctuations_-________________---__----_--_---_----_ 81 Natural fluctuations._________________-___--____------_---_ 83 Seasonal fluctuations_______-_-____--__-_--_--_-----_-__ 83 Long-term trends______________________________________ 85 Maximum range of fluctuation._________________________ 86 Effect of geology and topography________________________ 86 Fluctuations due to pumping________________________________ 87 Types of wells and springs..____________________________________ 90 Drilled wells___--__-______________________--______--___-__ 90 Jetted wells__ _____________________________________________ 91 Driven wells._____________________________________________ 91 Dug wells ________________________________________________ 92 Springs__ _______________________________________________ 92 Quality of ground water________________________________________ 96 Chemical characteristics of ground water _____________________ 96 Quality as related to source_________________________________ 97 Quality as it influences use________________________________ 103 Bacterial contamination in ground water.____________________ 104 Temperature of ground water__________--____________-_----__--_ 108 Logs of wells and test borings-____________________-______-__-----_-_ 109 Selected references_________________________________________________ 124 Index._________________________________________________________ 127 ILLUSTKATIONS [Plates are in separate volume] PLATE 1. Bedrock topography and surficial geology of the Farmington- Granby area. 2. Geologic cross sections. 3. Ground-water availability in the stratified drift and alluvial deposits of the Farmington-Granby area. Pago FIGURE 1. Index map of Connecticut, showing area of this report, towns, and status of ground-water investigations______-____--_ 4 2. Areas in Connecticut covered by U.S. Geological Survey water- supply papers referring to ground water and published prior to 1930___.__________________ - -- 5 CONTENTS V Page FIGURE 3. Map-location system__________________________________ 8 4. Physiographic divisions and drainage in and near the Farm- ington-Granby area____________ ___--______-_-_---_ 9 5. Outcrop of crystalline rock, showing ice formed when ground water issued from joint openings in the rock during winter months. _ _____________________________________________ 22 6. Outcrop of igneous rock of the Newark group, showing well- developed vertical and horizontal joints_________________ 33 7. Depths of domestic and farm wells finished in the Newark group.______-__-_________-__-____-____-_______----_- 35 8. Rock thicknesses penetrated by domestic and farm wells finished in the Newark group._________________________ 36 9. Glaciofluvial beds in the ice-contact deposits.______________ 53 10. Lower unit of the valley-train deposits_-____________-_--_- 60 11. Cross section through wells EG 33 and 36, showing water levels and topography in a part of East Granby__________ 72 12. Total discharge and estimated ground-water discharge of Salmon Brook at Granbrook Park from October 1949 through September 1950______________._______-_-_-- 77 13. Water-level fluctuations in four observation wells finished in unconsolidated deposits.______________--______-_---- 82 14. Water-level fluctuations in eight observation wells finished in the Newark group.___________________________________ 83 15. Diagrammatic section of a well that is being pumped, showing its drawdown, cone of depression, and area of influence____ 87 16. Hydrograph of water levels in well EG 33 from October 17 through October 25, 1957. Measurements were made by an automatic recorder_______________________________ 89 17. Diagrammatic representation of the chemical character of ground water in the Farmington-Granby area____________ 102 18. Fluctuations of ground-water temperatures____________---- 109 TABLES Page TABLE 1. Normal monthly precipitation.___________________________ 11 2. Summary of climatological data at Hartford, Conn__________ 12 3. Evaporation at Reservoir No. 1, West Hartford, Conn_______ 13 4. Area and population of towns in the Farmington-Granby area. _ 13 5. Geologic units in the Farmington-Granby area______________ 15 6. Records of drilled wells involved in pumping tests.__________ 43 7. Estimated use of ground water for public water-supply sys­ tems during 1957_____________-_____--__-_-___-_------- 79 8. Estimated use of ground water for private domestic water supplies during 1957___________________-__-_-__----_-- 80 9. Estimated total use of ground water in 1957 in the Farmington- Granby area, by.categories of use__________-___--_----_ 80 10. Estimated total ground-water use in 1957 in the Farmington- Granby area, by towns___________________-_-_---_--- 80 11. Records of selected observation wells in the Farmington- Granby area______________________________-___--_--- 84 VI CONTENTS Page 12. Records of selected springs in the Farmington-Granby