Geohydrology of the Weldon Spring Ordnance Works, St. Charles County, Missouri
By DOUGLAS N. MUGEL
U.S. GEOLOGICAL SURVEY
Water-Resources Investigations Report 96-4171
Prepared in cooperation with the U.S. ARMY CORPS OF ENGINEERS
Rolla, Missouri 1996 U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary
U.S. GEOLOGICAL SURVEY Gordon P. Eaton, Director
The use of firm, trade, and brand names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey.
For addtional information write to: Copies of this report can be purchased from:
District Chief U.S. Geological Survey U.S. Geological Survey Information Services 1400 Independence Road Box 25286 Mail Stop 100 Federal Center Rolla, MO 65401 Denver, CO 80225 CONTENTS
Abstract...... ~^ 1 Introduction ...... ^ 2 Purpose and Scope...... 4 Physical Setting of the Weldon Spring Ordnance Works ...... 4 Previous Studies...... 4 Approach ...... ^ 6 Acknowledgments...... 7 Geohydrology of the Weldon Spring Ordnance Works...... 10 Bedrock Geology...... 10 General Structure...... 10 Stratigraphy ...... 11 Overburden Geology...... 18 Geohydrologic Units...... 20 Ground- Water Flow...... 22 Summary ...... ^ 26 References Cited...... 28
PLATES [Plates are at the back of this report] 1.-13. Maps showing: 1. Location of monitoring wells, geotechnical borings, domestic wells, and trenches at the Weldon Spring ordnance works, exclusive of the Weldon Spring chemical plant and the Weldon Spring quarry, St. Charles County, Missouri 2. Location of monitoring wells, geotechnical borings, domestic wells, and trenches at and in the vicinity of the Weldon Spring chemical plant, St. Charles County, Missouri 3. Structure of the top of the Chouteau Group, Weldon Spring ordnance works, St. Charles County, Missouri 4. Structure of the top of the Fern Glen Formation, Weldon Spring ordnance works, St. Charles County, Missouri 5. Altitude of the top of bedrock and generalized geology, Weldon Spring ordnance works, St. Charles County, Missouri 6. Altitude of the top of the unweathered unit of the Burlington-Keokuk Limestone, Weldon Spring ordnance works, St. Charles County, Missouri 7. Depth to the top of the unweathered unit of the Burlington-Keokuk Limestone, Weldon Spring ordnance works, St. Charles County, Missouri 8. Thickness of the weathered unit of the Burlington-Keokuk Limestone, Weldon Spring ordnance works, St. Charles County, Missouri 9. Thickness of the strongly weathered subunit of the weathered unit of the Burlington-Keokuk Limestone, Weldon Spring ordnance works, St. Charles County, Missouri 10. Thickness of overburden, Weldon Spring ordnance works, St. Charles County, Missouri 11. Altitude of the base of the glacial drift confining unit, Weldon Spring ordnance works, St. Charles County, Missouri 12. Thickness of the upper part of the shallow aquifer (base of glacial drift confining unit to top of the unweathered unit of the Burlington-Keokuk Limestone), Weldon Spring ordnance works, St. Charles County, Missouri 13. Geologic units in which monitoring wells are completed, Weldon Spring ordnance works, St. Charles County, Missouri
Contents III PLATES Continued 14.-16. Maps showing: 14. Potentiometric surface of the shallow aquifer, September 1994 and 1995, Weldon Spring ordnance works, St. Charles County, Missouri 15. The relation of the potentiometric surface of the shallow aquifer and the top of bedrock, Weldon Spring ordnance works, St. Charles County, Missouri 16. The relation of the potentiometric surface of the shallow aquifer and the base of the glacial drift confining unit, Weldon Spring ordnance works, St. Charles County, Missouri
FIGURES 1. Map showing location of the Weldon Spring ordnance works and selected geologic, hydrologic, and cultural features...... 3 2. Generalized stratigraphic column for the Weldon Spring ordnance works, showing geohydrologic units...... 8 3. Hydrogeologic section A-A^...... 12 4. Hydrogeologic sectionB-B'...... 13
TABLES 1. Stratigraphic and selected well construction data for U.S. Army monitoring wells, USGS-series and MWGS-series monitoring wells, and the Army well...... 32 2. Stratigraphic and well construction data for U.S. Department of Energy monitoring wells ...... 42
ABBREVIATIONS USED IN THIS REPORT AEC U.S. Atomic Energy Commission COE U.S. Army Corps of Engineers DGLS Missouri Division of Geology and Land Survey DOE U.S. Department of Energy GIS Geographic Information System GWOU Ground-Water Operable Unit PMC Project Management Contractor RI Remedial Investigation RQD Rock Quality Designation USGS U.S. Geological Survey WSCP Weldon Spring chemical plant WSOW Weldon Spring ordnance works WSQ Weldon Spring quarry WSSRAP Weldon Spring Site Remedial Action Project WSTA Weldon Spring training area ______
Sea level: In this report, "sea level" refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929) a geodetic datum derived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called Sea Level Datum of 1929.
IV Contents Geohydrology of the Weldon Spring Ordnance Works, St. Charles County, Missouri
By Douglas N. Mugel
ABSTRACT The overburden units are, in ascending order: residuum, basal till, glacial till, including a Bedrock units at the Weldon Spring ord glacial outwash subunit, the Ferrelview Forma nance works in St. Charles County, Missouri, dip tion, loess, alluvium, and fill. Some of the thickest to the northeast at about 60 feet per mile, as mea overburden occurs in the northern part of the sured by the top of the Chouteau Group. The top training area and north of the training area and of the bedrock forms a generally east-west trend may be caused by a larger thickness of glacial ing ridge through the Weldon Spring training area drift. The paleodrainage centered about the and the Weldon Spring chemical plant. This sur unnamed tributary to Dardenne Creek that con face contains a large, broad bedrock low centered tains Burgermeister spring appears to have been about the unnamed tributary to Dardenne Creek partially filled by glacial drift, and a surface-water that contains Burgermeister spring. The low has divide now exists southeast of the tributary. been interpreted to be a paleodrainage that existed The upper, more permeable part of the shal before deposition of glacial drift. This feature low aquifer consists of the residuum, basal till, consists of smaller, more elongate paleovalleys at glacial outwash (where there is no glacial till and west of the chemical plant where more dense below it), and the weathered unit of the Burling- drillhole data provide better definition. ton-Keokuk Limestone. The lower, less perme The uppermost bedrock unit throughout able part of the shallow aquifer consists of the most of the ordnance works is the Burlington- unweathered unit of the Burlington-Keokuk Keokuk Limestone of Mississippian age. It is sub Limestone and the Fern Glen Formation. Gener divided based on weathering characteristics into a ally, the upper part of the shallow aquifer thins to lower, unweathered unit; an upper, weathered the north, reflecting the thin to absent weathered unit; and a strongly weathered subunit of the unit north of the training area and chemical plant. weathered unit. The unweathered unit is a light to A glacial drift confining unit consists of parts of medium gray, coarse to less commonly fine crys the glacial till and the Ferrelview Formation. talline, thin to massive bedded, fossiliferous, Ground water as recharge and discharge probably cherty limestone. The unweathered unit can be moves in fractures through this unit. It confines silty or argillaceous, or can locally be dolostone ground water where the potentiometric surface of or siltstone. The weathered unit is characterized the shallow aquifer is above its base. There are by an increase in mostly horizontal fractures and stream reaches where the streams have cut partings, increased porosity, vugs, voids, breccia, through the glacial drift confining unit to expose and discoloration by iron oxides. A strongly the underlying shallow aquifer. weathered subunit of the weathered unit is identi A potentiometric surface map of the shal fied in some monitoring wells where these fea low aquifer shows a large ground-water mound in tures are particularly abundant or intense. the south-central part of the training area. This
Abstract 1 mound is part of a generally east-west trending the WSOW and the WSCP in the Weldon Spring ground-water ridge through the training area and quarry (WSQ) in the southern part of the WSOW (fig. the chemical plant that defines a ground-water 1) also resulted in contamination of ground and sur divide. Precipitation that percolates downward face water (MK-Ferguson Company and Jacobs Engi through fractures in the glacial drift confining unit neering Group, 1992). Details regarding the produc recharges the shallow aquifer. Where the glacial tion and subsequent demolition of the WSOW can be drift confining unit is not present, precipitation found in reports by International Technology Corpora can be expected to recharge the shallow aquifer tion (1993), Schumacher (1993), and Schumacher and others (1993). Details regarding the operation of the more readily. There is the potential for ground- WSCP can be found in reports by MK-Ferguson Com water flow in permeable overburden units where pany and Jacobs Engineering Group (1992), Schuma the potentiometric surface is above the top of bed cher (1993), and Kleeschulte and Emmett (1986). rock. Generally, the residuum and locally other The former WSOW currently (1996) consists of overburden units of the shallow aquifer poten several different properties and owners. The U.S. tially become more important as mediums of Army (hereafter referred to as the Army) retains own ground-water flow north and downgradient of the ership of 1,655 acres of the former WSOW, known as ground-water ridge. This is probably limited the Weldon Spring training area (WSTA; fig. 1). The where clay-rich zones in the residuum confine WSCP, immediately east of the WSTA, and the WSQ ground water below in the bedrock. Because the are owned by the U.S. Department of Energy (DOE). thickness of the weathered unit generally de In addition to the Army and DOE, other current (1996) creases to the north, it generally becomes a less owners of the former WSOW property are the Mis important medium of ground-water flow down- souri Department of Conservation (August A. Busch gradient to the north. Also to the north, the poten Memorial Wildlife Area and Weldon Spring Conser tiometric surface of the shallow aquifer is above vation Area), the St. Charles County Consolidated the base of the glacial drift confining unit over a School District (Francis Howell High School), the large area, indicating that the aquifer is confined. University of Missouri, the Missouri Highway and Upward ground-water gradients measured in Transportation Department (pi. 1), the Weldon Spring monitoring well pairs, Burgermeister and other Heights subdivision, and a private golf course. springs, the gaining unnamed tributary to Dar- Contaminant-related studies and clean-up activ denne Creek upstream of Burgermeister spring, ities conducted by the DOE at the WSCP and WSQ and Dardenne Creek indicate ground-water dis are referred to as the Weldon Spring Site Remedial charge in the northern part of the ordnance works. Action Project (WSSRAP). Contaminant-related stud ies and activities on the remainder of the WSOW, including the WSTA, are being conducted by the U.S. Army Corps of Engineers (COE). INTRODUCTION In 1995, the Army and DOE prepared a joint During World War II, the Weldon Spring ord ground-water operable unit (GWOU) work plan to nance works (WSOW) was a U.S. Army explosives address ground-water contamination at the WSOW production facility that occupied 17,232 acres of land (Argonne National Laboratory, 1995). This work plan in St. Charles County, Missouri (fig. 1). The Weldon currently (1996) is being used for the preparation of a Spring chemical plant (WSCP), a 217-acre section of joint Army and DOE ground-water remedial investiga the WSOW, was operated by the U.S. Atomic Energy tion (RI) report for the WSOW. To prepare the joint Commission (AEC) from 1957 to 1966 for processing work plan, it was necessary to integrate geologic and uranium (fig. 1). These two activities resulted in local ground-water data collected independently by the Army ized nitroaromatic and radioactive contamination of and DOE into a comprehensive geohydrologic descrip soil, ground and surface water, and buildings (Interna tion of the WSOW. This would facilitate the correlation tional Technology Corporation, 1992, 1993; MK-Fer- of water-quality data between Army and DOE monitor guson Company and Jacobs Engineering Group, ing wells and, thereby, contribute to the understanding 1992). Disposal of wastes and demolition debris from of the extent of contamination and potential spread of
Geohydrology of the Weldon Spring Ordnance Works, St. Charles County, Missouri 90*55' 90'35'
38'55' -
Former Weldon Spring ordnance works 45' -
38'35' -
8 KILOMETERS EXPLANATION
ANTICLINE Dashed where approximately located (from McCracken, 1971) FAULT Approximately located; dashed where inferred; dotted where concealed or postulated. U, upthrown side; D, downthrown side (from Whittield and others, 1989)
Introduction contamination at the WSOW. The U.S. Geological nounced and the topography consists of gently rolling Survey (USGS) conducted a study from 1993 to 1996 hills sloping to the north. Average annual precipitation in cooperation with the COE to create a common data is 38.5 in. (inches; National Oceanic and Atmospheric base for Army and DOE geohydrologic data and to use Administration, 1994). these data together with USGS and Missouri Division of Geology and Land Survey (DGLS) data to develop a comprehensive geohydrologic description of the Previous Studies WSOW, exclusive of the WSQ. The WSOW has been the subject of much inves tigation. This section briefly mentions some of the Purpose and Scope studies that have described the geology or ground- water hydrology of the WSOW, exclusive of the WSQ, The purpose of this report is to present the or the region. Reports by Kleeschulte and Emmett results of the geohydrologic study of the WSOW. This (1986) and Kleeschulte and Emmett (1987) also sum report contains a geohydrologic description of the marize geologic, hydrologic, and contaminant investi WSOW, which consists of descriptions of the geology gations, and summaries of several geologic and ground-water hydrology. The geohydrologic investigations also are presented in the report by description of the WSOW integrates Army, DOE, Meyer,Jr. (1991). USGS, and DGLS data collected mostly from 1983 to 1995. An important component of this study was the The geology and ground-water hydrology of the re-logging of bedrock and overburden core samples WSOW were summarized and additional data require from Army monitoring wells and bedrock core sam ments were identified in the joint Army and DOE ples from some DOE monitoring wells. Emphasis was GWOU work plan (Argonne National Laboratory, placed on re-logging the Burlington-Keokuk Lime 1995). Work to meet these requirements was con stone1 . Geologic descriptions presented in this report ducted in 1995 by the Army and the DOE and con also are based on down-hole geophysical logging of sisted of installing several new monitoring wells, some monitoring wells and onsite mapping of over drilling three angle (30° from vertical) borings, con burden units. The ground-water hydrology of aquifers ducting hydraulic conductivity tests on these borings and confining units is described, including interpreta and some monitoring wells, conducting tracer tests, tions regarding the occurrence and movement of and measuring water levels in wells. ground water. This report does not address contami Before the joint Army and DOE RI, which cur nant distribution and movement or surface-water rently (1996) is being prepared, the Army and the hydrology. DOE completed separate RIs. The RI completed by the Army for the WSOW (International Technology Corporation, 1992) characterized the contamination of Physical Setting of the Weldon Spring soils, surface water, sediments, and manmade struc Ordnance Works tures at the WSOW, exclusive of the WSTA, WSCP, and the WSQ. The RI completed by the Army for the The WSOW is situated along the boundary WSTA (International Technology Corporation, 1993) between the Dissected Till Plains of the Central Low described the geohydrology at the WSTA and the land Province and the Salem Plateau of the Ozark Pla remainder of the WSOW, excluding the WSCP and the teaus Province (Fenneman, 1938; fig. 1). An east-west WSQ, and also characterized contamination at the trending ridge occurs in the southern part of the WSTA. Monitoring wells were installed, soil and rock WSTA and WSCP. This ridge divides surface water cores were logged, monitoring wells and springs were flowing south to the Missouri River from water flow sampled, and water levels in wells were measured ing north to the Mississippi River. South of this divide, (International Technology Corporation, 1993). The streams are strongly incised and the topography is rag results of quarterly water-level measurements and ged. North of the divide, stream incision is less pro- water-quality analyses were reported in quarterly ground-water monitoring reports for the WSOW, ^sage follows nomenclature of the Missouri Division of exclusive of the WSCP and WSQ (International Tech Geology and Land Survey. nology Corporation, 1996).
Geohydrology of the Weldon Spring Ordnance Works, St. Charles County, Missouri The RI for the WSCP (MK-Ferguson Company cal Survey, written commun., 1944). A later investiga and Jacobs Engineering Group, 1992) contains the tion by the USGS evaluating the water availability at results of geologic and hydrologic studies performed the WSOW summarized the regional geology (Rob by the DOE as part of the WSSRAP. It contains sev erts, 1951). In 1983, a 3-year study was initiated to eral structure contour maps of the WSCP and vicinity. determine the extent and magnitude of ground- and Data generated in support of the RI also are presented surface-water contamination from the WSCP and the in other reports (MK-Ferguson Company and Jacobs WSQ. Regional geology and hydrology; water-quality Engineering Group, 1989, 1990). Geologic, geotechni- data from the raffinate pits, nearby streams, and the cal, and hydrologic data for the RI also are summa shallow aquifer collected from 1984 through 1986; rized in a report evaluating the suitability of the WSCP seepage-run data for several streams; and discharge site as a location for a mixed low-level radioactive and data for several springs are included in several reports hazardous waste disposal facility (MK-Ferguson (Kleeschulte andEmmett, 1986, 1987; Kleeschulte Company and Jacobs Engineering Group, 1991). A and others, 1986). Data (including water-level data) report by Durham (1992) summarizes a numerical collected from 1986 through 1989 as part of Phase II model to simulate ground-water flow in the shallow of that study are presented by Kleeschulte and Cross aquifer at the WSCP and also presents geologic and (1990). Regional and local geology and hydrology, hydrologic data from the RI. Annual ground-water including contaminant transport, background water monitoring results are presented in annual environ quality, and the results of a regional three-dimensional mental reports (MK-Ferguson Company and Jacobs ground-water flow model are presented by Kleeschulte Engineering Group, 1996). and Imes (1994). Contaminant attenuation in the over Before the beginning of the WSSRAP in 1986, burden and bedrock, the geochemistry of the intersti several investigations were conducted at the WSCP. A tial water in sludges of the raffinate pits, the decommissioning study at the WSCP and WSQ was geochemical controls on the extent and magnitude of performed, which involved installing several monitor contaminant migration from the raffinate pits within ing wells at the WSQ (National Lead Company of the overburden, and the sources of increased concen Ohio, Inc., 1977). A preliminary geologic character trations of contaminants in the shallow aquifer in the ization was made at the raffinate pits at the WSCP, vicinity of the WSCP are given by Schumacher (1990, which contain wastes from the processing of uranium 1993). Geochemical, hydrologic, and water-quality and thorium (Berkeley Geosciences Associates, 1984). data collected from 1990 through 1992 to characterize That characterization was based on data from seven the geochemistry of the overburden and to determine monitoring wells installed to the top of bedrock. A the environmental fate of nitroaromatic compounds at more extensive characterization of the raffinate pits the WSTA and vicinity properties are presented by area was done in 1983 (Bechtel National, Inc., 1984) Schumacher and others (1993). Geochemical, hydro- that included the installation of additional boreholes, logic (including water-level data), and water-quality monitoring wells and piezometers, and excavating data collected from 1992 through 1995 at the WSOW trenches and conducting geophysical surveys. Work are presented by Schumacher and others (1996). performed by Bechtel National, Inc. (1987) as part of The DGLS has conducted investigations at the an investigation to site a disposal facility at the WSCP WSOW for several years. The bedrock geology for included boreholes, monitoring wells, trenches, geo two 7-1/2 minute quadrangles in which the WSOW is physical surveys, aquifer testing, and water-quality located has been mapped (Whitfield, 1989; Whitfield sampling. and others, 1989). An investigation to better define the The USGS was first involved in geologic and relation between precipitation, surface runoff, and hydrologic investigations at the WSOW in 1943 and ground-water recharge to and discharge from the shal 1944, following a request by the War Department to low aquifer at the WSOW was conducted by the investigate contamination of ground and surface water DGLS from 1987 through 1990 (Missouri Division of by "red water" from WSOW production processes. Geology and Land Survey, 1991). Results of dye trac Wells and springs were sampled, and water-table map ing, stream gaging, water-level monitoring, a karst ping indicated that ground water north of the ground- features inventory, geophysical surveys, onsite recon water divide at the WSOW discharged to Dardenne naissances, and the delineation of recharge areas are Creek (V.C. Fishel and C.C. Williams, U.S. Geologi presented in that report, along with a discussion of
Introduction previous DGLS dye traces. The DGLS also conducted face geology of the WSOW, exclusive of the WSQ. an investigation from 1990 to 1991 to identify shallow Reference to the WSOW in this report generally refers ground-water discharge points around the WSTA to the study area. (Price, 1991). Results of additional dye tracing, a karst To develop a comprehensive geohydrologic features inventory, water-level monitoring, and the description of the WSOW, the first task was to review delineation of recharge areas are presented in that the geologic data that were available and identify any report. Results of a DGLS investigation to identify inconsistent terminology or data. Inconsistencies were overburden units and define the engineering and possible between the descriptions of the geology at the chemical properties of these units at the WSTA are WSCP by DOE and throughout the rest of the WSOW given by Rueff (1992). That study involved the use of by the Army. Several documents were reviewed, trenches, pits, and borings at the trenches to determine including the RI reports for the WSTA (International and map the overburden units and laboratory testing of Technology Corporation, 1993), the WSOW (Interna the overburden units to determine engineering proper tional Technology Corporation, 1992), and the WSCP ties. (MK-Ferguson Company and Jacobs Engineering The locations of monitoring wells that were Group, 1992). Monitoring well drill core logs were installed at the WSOW as part of previous investiga reviewed. Based on the review, correlation of geology tions are shown on plates 1 and 2. The densest cover from the WSCP to the WSTA and other parts of the age of monitoring wells is at and in the vicinity of the WSOW was difficult because the Army and the DOE WSCR Most of these monitoring wells were installed did not use the same terminology to describe bedrock by the DOE and are denoted as MW-series wells. The drill cores and did not subdivide the Burlington- locations of these monitoring wells and a large number Keokuk Limestone in the same way. In addition, veri of geotechnical borings at the WSCP also drilled by fication of unit contacts for Army cores was needed. the DOE are shown on plate 2. The DOE also installed Specifically, while both agencies described monitoring five deep monitoring wells: MWGS-1 and MWGS-2, wells as shallow or deep and the Burlington-Keokuk located immediately south of the WSCP, and MWGS- Limestone as upper or lower, only the DOE subdi 3, MWGS-4, and MWGS-5, located north of the study vided the Burlington-Keokuk Limestone into a weath area in the August A. Busch Memorial Wildlife Area. ered unit and an unweathered unit at the WSCP (fig. The Army also has installed a large number of moni 2). Because the upper, weathered unit is more perme toring wells, denoted as (1) MWV- and MWVR- for able than the underlying unweathered unit (MK-Fer monitoring wells completed in the overburden; (2) guson Company and Jacobs Engineering Group, MWS- for monitoring wells completed in the shallow 1992), contaminated ground water probably flows bedrock; and (3) MWD- for monitoring wells com more readily through the weathered unit. However, it pleted in the deep bedrock. These wells and the was not clear initially if these same units could be USGS-series monitoring wells installed by the USGS described outside the WSCP and, if so, what criteria in 1986 are located at the WSOW exclusive of the could be used to define them. WSCP and WSQ (pi. 1). Well clusters, consisting of two or more monitoring wells, occur in several places Bedrock cores had previously been collected by throughout the WSOW. Several active or abandoned the Army and DOE during monitoring well installa domestic wells for which geologic data exist are iden tion and, in the case of the DOE, also from geotechni tified by a DGLS well log number (pi. 1). One of these cal borings at the WSCP. The USGS and a represen wells (4843) is located on the WSTA and is referred to tative of the DOE Project Management Contractor as the "Army well." (PMC) familiar with the criteria used to make unit dif ferentiations worked together to ensure consistency of geologic descriptions of the bedrock by the Army and Approach DOE. After several of the Army and DOE bedrock cores were reviewed jointly, the differentiation of The study area includes most of the former weathered and unweathered units of the Burlington- WSOW and some properties outside the boundary of Keokuk Limestone, which had been applied by the the former WSOW (fig. 1). This area was chosen DOE (MK-Ferguson Company and Jacobs Engineer because it includes almost all the monitoring wells and ing Group, 1992), was adopted to describe the Army geotechnical borings used to characterize the subsur cores, and common criteria for differentiating units
Geohydrology of the Weldon Spring Ordnance Works, St. Charles County, Missouri were developed. A previously unrecognized subunit of nical borings, domestic wells, and DGLS overburden the weathered unit, termed the strongly weathered trenches. This data base contains geologic data, water- subunit, was identified in some Army and DOE cores. level data, and well construction data, such as surface Several Army cores were logged jointly in detail. Sev and top-of-casing altitudes and screen and sand pack eral DOE cores were reviewed jointly to verify that intervals. Construction data for Army monitoring both the USGS and the DOE PMC representative wells are from International Technology Corporation agreed on the location of the weathered unit/unweath- (1993). Construction data for DOE monitoring wells ered unit contacts previously identified by the DOE are from MK-Ferguson Company and Jacobs Engi PMC, and strongly weathered subunits were identified neering Group (1992) and were also provided by the where present. The USGS logged the remainder of the DOE PMC. Some revisions to the top of bedrock and Army cores and photographed all the Army cores for unit contacts for DOE cores were made based on the future reference. These logs contain rock descriptions DOE PMC representative's review of DOE core logs and measurements of core recovery, rock quality des and photographs. Geologic and well construction data ignation (RQD), and fractures per foot. The DOE for domestic wells are from drill cuttings logs pre PMC representative reviewed the logs and photo pared by the DGLS and stored at the DGLS well log graphs of the remainder of the DOE cores, which had library in Rolla, Missouri. previously been taken by the DOE PMC, to confirm The GIS data base was used to produce several the top of bedrock and the weathered unit/unweath- maps. Data for surface altitude maps were plotted, ered unit contacts and to identify strongly weathered hand-contoured, and digitized. Thickness maps were subunits. prepared by mathematically determining surface alti Whereas all the DOE drill cores are from the tudes on a 1,000-ft (foot) center grid, subtracting the Burlington-Keokuk Limestone, some of the Army grid values on one surface from those on the overlying monitoring wells penetrate older units. The Burling surface, and hand-contouring these thickness data ton-Keokuk Limestone/Fern Glen Formation contact along with drill hole thickness data. This procedure was identified in several Army cores after some assis allows thickness contours to more accurately reflect tance from a representative of the DOE PMC to define unit thicknesses than if only drill hole thickness data this contact. were used. However, only drill hole data were used to Because overburden units had previously been create the thickness map of the strongly weathered identified in core samples only from DOE monitoring subunit, because this subunit occurs anywhere in the wells and geotechnical borings, overburden samples weathered unit and is, therefore, not defined by sur from all but two Army monitoring wells were re faces above and below it. The GIS data base was used viewed to identify overburden units. Because these to plot data for a potentiometric surface map using samples had been stored for several years, some of the depth-to-water measurements made by the USGS. samples were desiccated, causing difficulty in identi Two maps were made by subtracting the potentiomet fying overburden units in some cases. To supplement ric surface from geologic structure surfaces. The GIS these overburden data, the stream banks of parts of data base also was used to plot data for two hydrogeo- logic sections. Schote Creek and its tributaries in the northern part of the WSTA and the southern part of the August A. Busch Memorial Wildlife Area upstream of Lake 35 Acknowledgments (pi. 1) were examined to identify these overburden units. The author thanks PC. Patchin of the Morrison Down-hole natural gamma logging was done in Knudsen Corporation, who worked closely with the several Army and DOE monitoring wells. The purpose author to standardize geologic descriptions of bedrock of logging these wells was to determine characteristic units for the Army and DOE and helped the author natural gamma activities for the weathered unit and compile geologic data for DOE monitoring wells and the strongly weathered subunit that correlated with the geotechnical borings. Appreciation is also extended to core and to then identify these units in the few moni Julie Reitinger of MK-Ferguson Company for her toring wells where no core existed. assistance in compiling geologic, water-level, and A geographic information system (GIS) data well-construction data for DOE monitoring wells. The base was developed for the monitoring wells, geotech author thanks J.L. Bognar, formerly with Jacobs Engi-
Acknowledgments SYSTEM SERIES STRATIGRAPHIC THICKNESS, LITHOLOGY GEOHYDROLOGIC REMARKS UNIT The St. Charles County well HOLOCENE field is located in the Alluvium 0-120 Silt, sand, gravel Alluvial aquifer Missouri River alluvium in the southern part of the Weldon Spring ordnance works Loess 0-11 Silty clay to silt Not classified None 0-22 Ferrelview Formation Clay to silty clay Confines the shallow aquifer only where base of unit is Glacial drift QUATERNARY Sandy and silty below potentiometric surface PLEISTOCENE clay to clayey silt, confining unit of shallow aquifer, mainly in with scattered August A Busch Memorial rock fragments Wildlife Area Glacial till 0-47 Occurs as a subunit of the Glacial outwash 0 - 30 (°) Sand to clayey, glacial till at monitoring wells sandy silt MWS-108, MWVR-24, MWD-106, and possibly also DGLS trench T-6 Sandy, clayey, Appears to be present mainly in western and north-central Basal till (d) 0-10 silty gravel or gravelly silt parts of chemical plant and eastern training area 0-38 Clay, chert, silt, LJthology is variable. Where Residuum * ' sand; locally Upper part of the shallow aquifer clay-nch, it may locally contains limestone confine ground water fragments Limestone; gray to orange-brown, commonly silty, Weathered unit overlies Weathered 0-112.5 argillaceous, unweathered unit where unit cherty, porous, both are present. Strongly vuggy, fractured. weathered subunit of the Locally siltstone weathered unit is identified Buriington-Keokuk 0-185 where weathering features Limestone W are particularly abundant MISSISSIPPIAN Limestone; light to or intense medium gray, Unweathered cherty. Locally 0-113{+) O unit silty or argillaceous. Locally dolostone, siltstone Lower part of the shallow aquifer Commonly vuggy; some Cherty dolostone quartz- or calcite-lined and limestone geodes Fern Glen Formatioi Meppen Limestone 0-18 Massive chert-free Member limestone Shaley, finely KINDERHOOKIAN Chouteau Group 0 - 45{+) crystalline limestone Bachelor Formation 0-2 Sandstone None Bushberg 0-20 DEVONIAN Sandstone Sandstone UPPER Sulphur Springs 0-45 Confining unit Group Fossiliferous, oolitic Glen Park 0-25 Limestone limestone with clay seams ORDOVICIAN CINCINNATIAN Maquoketa 0-11 Calcareous or Identified in study area only Shale dolomitic shale at monitoring well MWGS-2 Rgure 2. Generalized stratigraphic column for the Weldon Spring ordnance works, showing geohydrologic units (modified from Kleeschulte and Imes, 1994). 8 Geohydrology of the Weldon Spring Ordnance Works, St. Charles County, Missouri SYSTEM SERIES STRATIGRAPHIC THICKNESS, LJTHOLOGY GEOHYDROLOGIC REMARKS UNIT (a) IN FEET (b) UNIT Coarsely crystalline Oldest unit to crop out in Kimmswick Limestone 41 - 104 limestone; cherty Middle aquifer study area near base Interbedded Decorah Group 25 - 36 (+) limestone MOHAWKIAN and shale Plattin Limestone Rnely crystalline 70 - 125 limestone Confining unit Rnely crystalline Joachim Dolomite 80 - 105 silly dolostone, siltstone, shale ORDOVICIAN None St. Peter Sandstone 120 - 150 (9) Sandstone Powell Dolomite 50 - 60 (9) Dolostone Cotter Dolomite 200 - 250 (9) Cherty dolostone with shale Jefferson City Dolomite 160 - 180 (9) Dolostone Dolostone, Roubidoux Formation 150 - 170 (9) O sandstone Deep aquifer Deepest unit in St. Charles County to supply water to Gasconade Dolomite (h) Cherty dolostone, sandstone public water-supply wells Eminence Dolomite (h) Dolostone High salinity may prevent use of water in study (h) Dolostone, quartz area Potosi Dolomite druse CAMBRIAN Dolostone, DC Derby-Doerun Dolomite (h) Aquifer characteristics LLJ siltstone, shale Confining unit unknown at study area; confining unit in Ozark Davis Formation (h) Shale, dolostone, region limestone Bonneterre Formation (h) St. Francois aquifer in Ozark Dolostone region but yield and Not classified salinity unknown in study Lamotte Sandstone (h) Sandstone area PRECAMBRIAN Igneous rocks (undifferentiated) Igneous rocks Confining unit None a) Bedrock stratigraphy conforms with Missouri Division of Geology and Land Survey stratigraphy presented in Thompson (1995). Bedrock stratigraphy differs slightly from stratigraphy for the Weldon Spring ordnance works area presented in Whitfield (1989) and Whitfield and others (1989). b) Unless otherwise indicated, maximum thicknesses shown are maximum thicknesses at wells. Thicknesses may be greater in other parts of study area where well data do not exist. c) Subunit thickness is 30 feet at monitoring well MWS-108, 7 feet at MWVR-24R, 1 foot at MWD-106, and possibly 2 feet at DGLS trench T-6. d) Unit is part of U.S. Department of Energy nomenclature (MK-Ferguson Company and Jacobs Engineering Group, 1992) not recognized by Rueff (1992). Thin intervals of this unit have tentatively been identified by the U.S. Geological Survey at monitoring wells MWS-3 and MWS-21. e) Residuum is composed of the residual material from the weathering of the uppermost bedrock unit and possibly younger rocks, including locally post-Mississippian rocks. The uppermost bedrock unit in most places is the Buriington-Keokuk Limestone. f) Usage follows nomenclature of the Missouri Division of Geology and Land Survey. g) Unit thicknesses are from Kleeschurte and Imes (1994). h) Insufficient data to make thickness estimates. Figure 2. Generalized stratigraphic column for the Weldon Spring ordnance works, showing geohydrologic units (modified from Kleeschulte and Imes, 1994) Continued. Acknowledgments neering Group, for his assistance in identifying the ing Eureka-House Springs Anticline located about 1 Fern Glen Formation in Army cores and T.L. Thomp mi (mile) southwest of the WSOW (fig. 1), accounts son of the DGLS for providing information regarding for the northeast dip of the rocks at the WSOW This the stratigraphy of bedrock units at the WSOW. The dip is illustrated in structure-contour maps of the top input of L.A. Durham of Argonne National Laboratory of the Fern Glen Formation, the Bushberg Sandstone, and Jeff Carman of Jacobs Engineering Group regard and the St. Peter Sandstone over an area much larger ing the geohydrology of the WSCP also was helpful. than the WSOW (MK-Ferguson Company and Jacobs Engineering Group, 1992). It also is shown in several structure-contour maps of geohydrologic units in St. GEOHYDROLOGY OF THE WELDON Charles County (Kleeschulte and Imes, 1994). Results SPRING ORDNANCE WORKS of this study confirm a northeast dip at the WSOW, as illustrated by the top of the Chouteau Group (base of This section presents a discussion of the geohy the Fern Glen Formation) that dips about 60 feet per drology of the WSOW with emphasis on the geologic mile to the northeast (pi. 3). Structure contours of the framework. The geology of the WSOW is described in top of the Fern Glen Formation are shown on plate 4. separate sections for bedrock and overburden. Struc Because of the gradational facies contact between the ture and thickness maps are included to show unit dis Fern Glen Formation and the overlying Burlington- tributions, altitudes, and thicknesses. The section on Keokuk Limestone (Thompson, 1986), this surface is bedrock geology presents the structural setting of the a less reliable indicator of structure than the top of the WSOW and descriptions of bedrock units. The section Chouteau Group. The northeast dip also is reflected in on overburden geology presents descriptions of un- the regional outcrop pattern of bedrock units, where consolidated units and a thickness map of the overbur progressively younger units are exposed from south den. The ground-water hydrology at the WSOW is west to northeast. Bedrock units older than the Burl- described in separate sections on geohydrologic units ington-Keokuk Limestone crop out in the southern and ground-water flow. Interpretations are concen part of the WSOW (pi. 5) as a consequence of north trated on the shallow aquifer of a three-aquifer system east dipping strata and deep incision by tributaries to that has previously been described for St. Charles the Missouri River. More details concerning regional County (Kleeschulte and Imes, 1994). structural features are presented by Kleeschulte and Imes (1994). The WSOW does not contain any definitively Bedrock Geology mapped faults. However, a fault, which has been inferred east of the study area, is postulated to extend The bedrock geology of the WSOW is described into the northeastern part of the study area (Whitfield in two separate sections. The section on general struc and others, 1989; fig. 1; pi. 5). The fault, known as the ture describes regional and local structure, including Cottleville Fault, is a normal fault with the north side bedding attitude, faults, joints, and the top of bedrock downthrown and is estimated to have occurred surface. The section on stratigraphy describes bedrock between Pennsylvanian and Quaternary time (J.W. stratigraphy, lithology and weathering characteristics, Whitfield, Missouri Division of Geology and Land and the distribution and thickness of units. Survey, oral commun., 1992). Also, a northwest- trending reverse or thrust fault has been interpreted in General Structure the western part of the WSOW and northwest of the The WSOW is on the extreme northeast flank of WSOW, based on drill cutting logs for three domestic the Ozark Dome, one of several domes and arches, wells (MK-Ferguson Company and Jacobs Engineer together with intracratonic basins that define the over ing Group, 1992). However, surficial geologic map all structure of the midcontinent region of the United ping by the DGLS (Whitfield and others, 1989) and States (Snyder, 1968). Uplift of the Ozark Dome pro this study did not indicate a fault in the western part of duced a broad area of Paleozoic rocks that dip periph the WSOW, although for this study drill-core data in erally away from the Precambrian St. Francois this area are sparse. Mountains in southeastern Missouri (Snyder, 1968). Vertical joint sets have been mapped at the This regional dip, together with the northwest-trend WSOW. MK-Ferguson Company and Jacobs Engi- 10 Geohydrology of the Weldon Spring Ordnance Works, St. Charles County, Missouri neering Group (1992) concluded that joint sets are ori relief is indicated on plate 5 where data are less dense. ented northwest and northeast and a minor set is Little subsurface data exist south of the WSTA; con oriented north. Mapping of joints at quarries and expo tours are dashed to reflect the lack of data and are sures along drainages near the WSQ showed a major approximately located to show the top of bedrock sur set oriented N70°W to N80°W, two secondary sets ori face similar to but slightly lower in altitude than the ented N50°W to N60°W and N60°E to N80°E, and a land surface. The altitude of the top of the bedrock minor set oriented north (MK-Ferguson Company and also is approximated where a distinct residuum/bed Jacobs Engineering Group, 1992). Earlier mapping of rock contact is difficult to identify. Because the upper the limestone bluffs near the WSQ showed a major part of the bedrock is weathered in many areas and joint set oriented N70°W and two less prominent sets because residuum is essentially extremely weathered oriented N60°E and north (Berkeley Geosciences rock, the contact between the two is gradational, and Associates, 1984). Roberts (1951) lists two joint sets the assigned value is approximate in some cases. Also, in the WSOW area one set oriented from N30°W to because the USGS-series monitoring wells were not N60°W and the other set oriented from N30°E to cored, the bottom of casing was assumed to be the top N72°E. International Technology Corporation (1993) of bedrock, and this value is, therefore, approximate. also described two joint sets in the WSOW one ori The top of bedrock forms a generally east-west ented N3°W to N65°W and the other oriented N30°E trending ridge in the southern to central part of the to N72°E. MK-Ferguson Company and Jacobs Engi WSTA and the southern part of the WSCP (pi. 5). The neering Group (1992) indicated that some stream seg elevated position and proximity of the WSOW relative ments are controlled by joint orientations. The to the Missouri River and the deep incision by tributar predominant stream segment mean orientation is ies to the Missouri River have resulted in a steeper N65°W, another set of stream segments has a mean slope of the top of bedrock to the south of this ridge orientation of N38°E, and a third set has a mean orien than to the north. The top of the bedrock north of the tation of N10°W (MK-Ferguson Company and Jacobs ridge is characterized by lows in the bedrock surface Engineering Group, 1992). Several tributaries of Dar- that trend approximately northward. Overlying the denne Creek trend from N40°E to N50°E (V.C. Fischel bedrock north of the ridge is residuum and glacial and C.C. Williams, written commun., 1944). deposits. The surface drainage has changed since preglacial time because of the deposition of glacial The control for the altitude of the top of the bed drift, and the preglacial surface drainage, as shown by rock surface (pi. 5) is core data and auger refusals at the altitude of the top of bedrock (pi. 5), is aligned monitoring wells, geotechnical borings and borings at with the present drainage only in places. A large, DGLS trenches, and DGLS logs of domestic wells. broad low in the bedrock surface centered about the Auger refusal refers to a situation whereby an auger unnamed tributary to Dardenne Creek (fig. 1) that con drill can penetrate no further because of resistance and tains Burgermeister spring (pi. 5) is interpreted to be is normally regarded as the top of bedrock. However, one such paleodrainage. Farther south, at and west of drill augers can be prematurely stopped by a chert bed the WSCP where more dense drill-hole data provide or boulder in the residuum. The altitude of the top of better definition, this large feature consists of smaller, bedrock has been adjusted for a few data points where more elongate depressions in the top of bedrock sur this is thought to have occurred. In areas where control face (pi. 5). These have been referred to as troughs data are densely spaced, such as at the WSCP, plate 5 (Kleeschulte and Imes, 1994) or paleochannels (MK- shows that the top of the bedrock has strong relief. Ferguson Company and Jacobs Engineering Group, Strong relief over short distances is indicated locally at 1992). In this report they are referred to as paleoval well clusters, such as MWS-23 and MWD-23, where leys to distinguish them from the larger paleodrainage the two altitudes of the top of bedrock differ by 19 ft they compose. (table 1, at the back of this report). Because the core log for MWS-23 (J.G. Schumacher, U.S. Geological Stratigraphy Survey, written commun., 1992) indicates that the lower part of what was identified as overburden may Stratigraphic and geohydrologic data and rela instead be fracture-fill material in bedrock, the altitude tions for the WSOW are shown in a Stratigraphic col of the top of bedrock for MWD-23 was used for the umn (fig. 2), monitoring well data tables (tables 1, 2), altitude of the top of bedrock map (pi. 5). Less local and hydrogeologic sections (figs. 3, 4; pi. 1). The Geohydrology of the Weldon Spring Ordnance Works 11 o I a o. o (Q O FEET 800 S oa 3 0)o 5' (Q 700 - 600 - UNWEATHERED UNIT OF THE BURUNGTON- KEOKUK UMESTONE 500 -1 FORMATIONS OLDER THAN FERN GLEN 400 -I FORMATION 0.5 1 MILE 0.5 1 KILOMETER 300 DATUM IS SEA LEVEL EXPLANATION VERTICAL EXAGGERATION X 22 WEATHERED UNIT OF THE BURLJNGTON-KEOKUK POTENTIOMETRIC SURFACE OF SHALLOW 1 ' LIMESTONE AQUIFER Dashed where approximately located 1113 FERN GLEN FORMATION OPEN INTERVAL OF MONITORING WELL --- CONTACT Dashed where approximately located Well clusters are shown as a single well TD -» - BASE OF GLACIAL DRIFT CONFINING UNIT Widely 107 TOTAL DEPTH OF HOLE. IN FEET spaced dots where approximately located Rgure 3. Hydrogeologic section A-A' (location of section shown on plate 1). CM -r- 9 9 ill CO I B B' FEET 700 -i 600 - 500 - m UNWEATHERED UNIT OF THE BURLJNGTON- OVERBURDEN KEOKUK UMESTONE O FORMATIONS OLDER (D O 400 - THAN FERN GLEN FORMATION 0.5 1 MILE (D 0.5 1 KILOMETER 300 (D DATUM IS SEA LEVEL VERTICAL EXAGGERATION X 22 2. E o EXPLANATION 3 CO WEATHERED UNIT OF THE BURLJNGTON-KEOKUK - POTENTIOMETRIC SURFACE OF SHALLOW LIMESTONE AQUIFER Dashed where approximately (D located FERN GLEN FORMATION OPEN INTERVAL OF MONITORING WELL a CONTACT Dashed where approximately located Well clusters are shown as a single well D> TD BASE OF GLACIAL DRIFT CONFINING UNIT Widely 107 TOTAL DEPTH OF HOLE, IN FEET 8 spaced dots where approximately located 8"O Rgure 4. Hydrogeologic section B-B' (location of section shown on plate 1). stratigraphic column (fig. 2) was modified from a ing wells MWS-101 and MWS-102 (pi. 1) is the stratigraphic column for St. Charles County in a report Kimmswick Limestone. Monitoring well MWS-102 by Kleeschulte and Imes (1994). Modifications reflect was completed in the Decorah Group, which is the changes specific to the WSOW, changes from re-log oldest unit for which drill core information exists in ging drill cores, or changes in DGLS stratigraphic the study area. South of the study area, the Plattin groupings and nomenclature (Thompson, 1995). Other Limestone of Ordovician age forms the valley floor of sources of information for this stratigraphic column the Little Femme Osage Creek (P.C. Patchin, Morrison are Whitfield (1989), Whitfield and others (1989), Knudsen Corporation, written commun., 1995). MK-Ferguson Company and Jacobs Engineering The Maquoketa Shale of Ordovician age has Group (1992), and Rueff (1992). Bedrock stratigraphy been reported to be present only in the eastern part of and selected well construction data for Army monitor St. Charles County, east of the WSOW (Kleeschulte ing wells, USGS-series monitoring wells, MWGS- and Imes, 1994). However, about 10 ft of Maquoketa series monitoring wells, and the "Army well" are Shale has been identified in DGLS logs of drill cut given in table 1. Bedrock stratigraphy and selected tings from two deep monitoring wells installed by the well construction data for all other currently (1996) DOE: MWGS-2 (DGLS log 28669), which is south of active and abandoned DOE monitoring wells are pre the WSCP (pi. 1), and MWGS-5 (DGLS log 28672), sented in table 2, at the back of this report. Strati- which is approximately 0.8 mi north of the central part graphic data for the DOE geotechnical borings are on of the study area (not shown on the plates) on the file at the office of the U.S. Geological Survey, Rolla, August A. Busch Memorial Wildlife Area (logs on file Missouri. Hydrogeologic sections that terminate near at the well log library of the Missouri Division of Burgermeister spring are shown in figures 3 and 4; the Geology and Land Survey, Rolla, Missouri). Strong locations of these sections are shown on plate 1. peaks in the natural gamma logs for both monitoring Hydrogeologic section A-A' (fig. 3) is drawn approxi wells correlate at slightly higher altitudes with the mately parallel to the down-dip direction, and the dip intervals of Maquoketa Shale identified in the logs. is distorted by the vertical exaggeration of the section. The Maquoketa Shale, however, has not been identi Because both hydrogeologic sections represent the fied in DGLS well logs for any domestic wells at the surfaces depicted by surface-altitude maps, the con WSOW, and it was not identified in cores from the two tacts on the sections are curved rather than straight Army monitoring wells (MWD-18 and MWS-103) lines between monitoring wells. that intersected the part of the stratigraphic section Little information is available for the deep bed where the Maquoketa Shale occurs. The Maquoketa rock units at the WSOW, particularly the upper Cam Shale appears to be absent over most of the WSOW brian units. The deepest public-water-supply well in and is probably present only as isolated post-Ordovi- St. Charles County is completed in the Gasconade cian erosional outliers. Dolomite of Ordovician age. The oldest unit to crop Upper Devonian Series formations at the out in St. Charles County is the Cotter Dolomite (fig. WSOW are the Glen Park Limestone and the Bush- 2), which crops out in the extreme southwestern part berg Sandstone, which form the Sulphur Springs of the county about 7 mi southwest of the WSOW Group (Thompson, 1995). The previous definition of (Missouri Division of Geology and Land Survey, the Sulphur Springs Group at the WSOW included an 1977). Any knowledge of units deeper than the Gas unnamed shale, the Glen Park Limestone, the Bush- conade Dolomite comes from a few oil and gas explo berg Sandstone, and the Bachelor Formation. The Sul ration holes in St. Charles County and from phur Springs Group previously was assigned to the projections of information from areas to the south Upper Devonian Series and the Kinderhookian Series where these units are shallower and more data are of Mississippian age (Whitfield, 1989; Whitfield and available. others, 1989). Incomplete intervals of the Sulphur The Kimmswick Limestone of Ordovician age Springs Group are present in cores from three moni (fig. 2) is the oldest bedrock unit to crop out in the toring wells. The entire interval is present at monitor study area. It forms the valley floor of the Little ing well MWD-18, where it is 20 ft thick. Femme Osage Creek (pi. 1) and its tributaries in the Mississippian rocks of the Kinderhookian Series southwestern part of the study area (Whitfield, 1989). are the Bachelor Formation and the Chouteau Group The uppermost bedrock unit encountered at monitor (Thompson, 1995). The Bachelor Formation is present 14 Geohydrology of the Weldon Spring Ordnance Works, St. Charles County, Missouri in cores from two monitoring wells (MWD-05 and where in the unweathered unit, it is more common MWD-18) where it is a thin (1-2 ft) quartz sandstone. near the top where the contact with the weathered unit The Chouteau Group is a finely crystalline limestone generally is gradational. with many shale seams and is present in cores from The unweathered unit of the Burlington-Keokuk two monitoring wells where its thickness is 21 ft Limestone is a light to medium gray, coarse to less (MWD-18) and 23 ft (MWD-05). The partial thick commonly fine crystalline, thin to massive bedded, ness of the Chouteau Group at one domestic well fossiliferous, cherty limestone that can be silty or (DGLS log 11390; pi. 1) that was completed partially argillaceous, or can locally be dolostone or siltstone. in the Chouteau Group is 45 ft. The chert is white to, less commonly, gray or blue- Mississippian rocks of the Osagean Series are gray and occurs as thin beds, lenses, and nodules. The the Fern Glen Formation and the Burlington-Keokuk limestone can be extremely cherty or relatively chert Limestone. The Fern Glen Formation is present in free, as noted in the lower part of the Burlington- cores from six monitoring wells, but its entire thick Keokuk Limestone at some of the deeper monitoring ness was penetrated by only one monitoring well wells. The dolostone is brown and occurs at some of (MWD-05), where it is 67 ft thick. The Fern Glen For the monitoring wells as distinct beds interbedded with mation in these cores generally is a finely crystalline limestone in the lower part of the Burlington-Keokuk dolostone and less commonly limestone, with chert Limestone. The contact between the Burlington- interbedded or as nodules. Parts of the Fern Glen For Keokuk Limestone and Fern Glen Formation is grada mation are characterized by "pinpoint" porosity (abun tional and difficult to identify because of their facies dant pores as large as approximately 1/16 in. in relation (Thompson, 1986). diameter). It also commonly contains some quartz- or The topography of the top of the unweathered calcite-lined or -filled vugs, as large as 1 in. in diame unit is shown on plate 6. The top of the unweathered ter, which have been called geodes (Whitfield, 1989; unit is shown as a surface, although the contact Whitfield and others, 1989; John Bognar, Jacobs Engi between the weathered and unweathered units gener neering Group, oral commun., 1993). A massive, ally is gradational. No information exists for this sur finely to coarsely crystalline limestone generally free face south of the WSTA. Because many of the Army of chert, known as the Meppen Limestone Member, monitoring wells in the WSTA are completed in the occurs as the basal unit of the Fern Glen Formation weathered unit and do not reach the unweathered unit, and is 18 ft thick at monitoring well MWD-05. A 15-ft the altitude of the top of the unweathered unit is not thickness is reported for the Meppen Limestone Mem known for much of the WSTA. Because the weathered ber in Whitfield and others (1989). unit is thin or absent in most monitoring wells north of The Burlington-Keokuk Limestone is the upper the WSTA and WSCP, the top of the unweathered unit most bedrock unit throughout most of the WSOW, is the same as or is close to the top of bedrock over and, consequently, more drill core data exist for it than much of this area. This similarity between the top of for any other unit. Little information exists for the the unweathered unit and the top of bedrock exists in Burlington-Keokuk Limestone south of the WSTA; the paleodrainage centered about the unnamed tribu except for monitoring wells installed at the WSQ, only tary to Dardenne Creek that contains Burgermeister three monitoring wells have been installed south of the spring, but only partially at the paleovalleys to the WSTA. The Burlington-Keokuk Limestone has been south (pi. 5). A depression exists in the top of the removed by erosion at all three of those locations. unweathered unit in the western part of the WSTA. Geotechnical borings drilled south of the WSTA This area is centered on monitoring well MWD-15 before the construction of the WSOW (pi. 1) were where the weathered unit is considered to compose the drilled only to the top of bedrock. entire Burlington-Keokuk Limestone. However, the The Burlington-Keokuk Limestone is divided Burlington-Keokuk Limestone at monitoring well into an upper weathered unit and a lower unweathered MWD-15 is not weathered throughout the entire thick unit. The term "unweathered" is used in a relative ness, but instead contains alternating intervals of sense because some of the weathering features that weathered and unweathered rock. The value used on characterize the weathered unit also occur in the plate 6 for this monitoring well is the top of the Fern unweathered unit, but less commonly and at a lower Glen Formation. If more data were available, this intensity. Although this weathering may occur any deeply weathered area might be shown to be smaller Geohydrology of the Weldon Spring Ordnance Works 15 with some elongation, reflecting structural (joint) con the weathered unit commonly is porous and, in trol, as has been suggested for the bedrock paleoval- extreme cases, chalky. leys at the WSCP (MK-Ferguson Company and The weathered unit contains a large number of Jacobs Engineering Group, 1992). horizontal fractures and partings along bedding planes. The top of the unweathered unit also can be rep Horizontal fracture and parting surfaces commonly resented by the depth of weathering, as defined by the show some rounding, which may be evidence of solu depth from land surface to the top of the unweathered tion of carbonate minerals. The surfaces commonly unit (pi. 7). An inverse relation exists between the have carbonate minerals and iron and manganese depth to the top of the unweathered unit and the alti oxides precipitated on them. Vertical and oblique frac tude of the top of the unweathered unit (pi. 6). That is, tures also occur and exhibit the same solution and pre areas where the depth to the unweathered unit is large cipitation features. Vertical and oblique fractures, correspond to some degree to "lows" in the altitude of however, are not present as much in core as horizontal the top of the unweathered unit. The patterns do not fractures because they probably are less common and exactly correspond because the depth to the top of the are less likely than horizontal fractures to be inter unweathered unit contains a variable amount of over sected by vertical drill holes. The core from two burden. angled holes drilled by DOE showed vertical fractures The weathered unit of the Burlington-Keokuk spaced an average of 10 ft apart and a horizontal-to- Limestone is characterized by alterations that have vertical fracture ratio of approximately 20:1 (MK-Fer been superimposed on the rock by weathering. These guson Company and Jacobs Engineering Group, alterations are lithology and color changes, an increase 1992). The vertical fractures tend to be enlarged and in porosity, and an increase in fractures. clay filled near the land surface and become tight at The weathered unit commonly is a porous, silty shallow depths (MK-Ferguson Company and Jacobs and argillaceous, cherty limestone, or less commonly Engineering Group, 1992). Both horizontal and verti siltstone. The silty and argillaceous material is concen cal fractures are not limited to the weathered unit nor trated by the solution of carbonate minerals and the to shallow depths. These features may occur any accumulation of insoluble silts and clays during the where, but are more common in the weathered unit. weathering process. The silty and argillaceous lime Chert beds and lenses tend to be fractured into many stone and siltstone, as well as the purer limestone, small pieces along variably oriented fractures, which commonly are orangish-brown because of discolora is an indication that the chert is more brittle than the tion by iron oxides. This discoloration permeates the limestone and that at least some of the fractures are rock as well as occurring along fracture and parting due to drilling. However, secondary iron and manga surfaces. nese oxide mineralization occurs along some of the Porosity in the weathered unit is greater than in chert fracture surfaces, indicating that some of the the unweathered unit and ranges from "pinpoint" breakage occurred along pre-existing fractures. The ("sponge-like", where pores are particularly abundant) density of fractures and partings in the weathered unit porosity to solution vugs and larger openings (voids), results in lower values of RQD than values for the some of which are associated with breccia. Vugs can unweathered unit and probably contributes to the gen be sites of core breakage and can contribute to low erally lower core recovery in the weathered unit. core recovery and low RQD, which is a measure of the The weathered unit is present in most of the competency of the rock. Vugs and larger voids can be WSOW where data exist (pi. 8), but its presence is not filled or partially filled by clay or a mixture of clay, determined south of the WSTA where no core data silt, and chert gravel (MK-Ferguson Company and exist for the Burlington-Keokuk Limestone. The Jacobs Engineering Group, 1992). The removal of this weathered unit is present at all monitoring wells and fill by drilling fluid results in poor core recovery. Loss geotechnical borings at the WSTA and WSCP, except of fluid during drilling also is associated with zones of at MWD-18 (pi. 1) where the Burlington-Keokuk core loss (MK-Ferguson Company and Jacobs Engi Limestone is not present. For a few monitoring wells neering Group, 1991). Garstang (1991) states that in well clusters, core drilling began below the bottom voids appear to have limited vertical and lateral conti of the weathered unit, and the presence of the weath nuity and that no open subsurface network of voids ered unit is indicated by another monitoring well in the was identified using a downhole camera. The chert in well cluster (tables 1, 2). At the August A. Busch 16 Geohydrology of the Weldon Spring Ordnance Works, St. Charles County, Missouri Memorial Wildlife Area north of the WSTA and The thickness map of the strongly weathered WSCP, the weathered unit is absent or generally thin subunit (pi. 9) is based partially on some assumptions. compared to its thickness at the WSCP and WSTA (pi. Where present at the WSTA, the strongly weathered 8). Except for monitoring well MWD-15 (pi. 1), where subunit occurs only in the uppermost part of the the weathered unit is considered to compose the entire weathered unit in the monitoring wells that penetrate Burlington-Keokuk Limestone and is 112.5 ft thick, the total thickness of the weathered unit. Based on this and monitoring well MW-4003 (pi. 1) that also has an occurrence, the strongly weathered subunit is assumed unusually thick section of the weathered unit (83.2 ft), not to be present in monitoring wells at the WSTA that the weathered unit ranges from 0 to 66.5 ft thick. penetrate a substantial but incomplete thickness of the Some monitoring wells were not completed deep weathered unit without intersecting the strongly enough to penetrate the unweathered unit, particularly weathered subunit. For the same reason, if a substan over much of the WSTA, and are shown with a sepa tial amount of weathered unit exists below the strongly rate symbol on plate 8 to indicate partial thicknesses weathered subunit in monitoring wells at the WSTA, for the weathered unit. Some correspondence exists that amount of strongly weathered subunit is assumed between the thickness of the weathered unit (pi. 8) and to be its total thickness. These assumptions cannot be the top of bedrock (pi. 5). For example, the paleoval- made at and in the vicinity of the WSCP where the ley that extends through the eastern part of the WSCP strongly weathered subunit is not always at the top of also is shown as a thin (less than 20 ft in places) area the weathered unit and where more than one interval of the weathered unit. Also, a "high" in the top of the of strongly weathered subunit can occur. The largest bedrock surface (pi. 5) in the western part of the known thickness of the strongly weathered subunit is WSCP partially corresponds to an area of thick weath at monitoring well MW-2009 (pi. 2), where it is a min imum of 33.5 ft thick. For DOE monitoring wells with ered unit (pi. 8). more than one interval of strongly weathered subunit, A strongly weathered subunit of the weathered the sum of individual intervals was used to construct unit of the Burlington-Keokuk Limestone has been plate 9. The DOE has suggested that zones of strongly identified where weathering features are particularly weathered Burlington-Keokuk Limestone seem to be abundant or intense. Typically, this subunit contains relatively continuous across the WSCP (J.C. Dille and intervals of poorer core recovery than the remainder of P.C. Patchin, Morrison Knudsen Corporation, written the weathered unit. Some of these intervals probably commun., 1994). are voids where the clay fill has been removed by drill The thickness of the strongly weathered subunit ing fluid. In a few cases where the core loss is extreme (pi. 9) does not correspond well with the thickness of and occurs immediately below auger refusal, the core the weathered unit (pi. 8). A lack of correspondence is loss interval has been reinterpreted to represent resid most obvious at monitoring well MWD-15 (pi. 1), uum, and the top of bedrock has been adjusted from where the entire Burlington-Keokuk Limestone is con previous logs. Another lithologic feature common in sidered to be the weathered unit, but where no strongly the strongly weathered subunit is breccia. The breccia weathered subunit is present. Also, little correspon is vuggy and is characterized by chert and less com dence is seen between the thickness of the strongly monly by limestone fragments in a weakly cemented, weathered subunit (pi. 9) and the topography of the sandy, clayey, and sometimes limey matrix. Poor core top of bedrock (pi. 5). recovery from breccia intervals is common. Down-hole natural gamma geophysical logs The strongly weathered subunit has a more lim were completed for several monitoring wells that have ited distribution than the weathered unit at the WSTA drill core to determine characteristic natural gamma and WSCP, although data are sparse in the east-central activities for the weathered unit and the strongly part of the WSTA (pi. 9). Drill-core data north of the weathered subunit and to determine if any other geo WSTA and WSCP, although not as dense as at the physical signals existed. Natural gamma activity is WSTA and WSCP, do not indicate the presence of the due to radioactive decay of clay minerals (Keys and strongly weathered subunit in this area, except imme MacCary, 1971). The clay mineral content is higher in diately north of the WSCP. There are no core data for the weathered unit than in the unweathered unit at the the strongly weathered subunit south of the WSTA and WSOW. Generally, the natural gamma activity WSCP. decreased with depth, indicating a decrease in weath- Geohydrology of the Weldon Spring Ordnance Works 17 ering. For most natural gamma logs, however, it was The lowermost overburden unit is residuum, difficult to identify distinct geophysical changes that which is the residual material resulting from the chem correlated with the weathered unit/unweathered unit ical weathering of rock. Residuum is derived from the contact, that identified a strongly weathered subunit, uppermost bedrock units and younger units that were or that confirmed the top of bedrock. Despite this gen once present. Residuum at the WSOW consists of eral lack of definition, natural gamma logs were used insoluble clay, chert, silt, and sand and locally contains to identify the weathered unit and the top of bedrock at limestone fragments. The residuum is variable in com two monitoring wells (USGS-1 and USGS-6) for position, both spatially and vertically, ranging from which drill core does not exist. clay-rich to chert-rich. Chert ranges from broken The Warsaw Formation, which is shale and gravel-size fragments to beds of sufficient thickness to cherty limestone, overlies the Burlington-Keokuk stop drill augers prematurely above the top of bedrock. Limestone, but it has not been identified as bedrock at Although loss of drilling fluid into the residuum has the WSOW. The DGLS (Whitfield and others, 1989; been reported during drilling at the WSCP (Bechtel Missouri Division of Geology and Land Survey, 1991) National, Inc., 1984; MK-Ferguson Company and has shown that the Warsaw Formation crops out in the Jacobs Engineering Group, 1991), no voids have been eastern part of the WSCP and to the east and north of reported in the residuum at the WSCP (MK-Ferguson the WSCP. However, these areas probably are resid Company and Jacobs Engineering Group, 1991). uum with residual Warsaw-type chert, instead of War Information regarding possible voids in the residuum saw Formation bedrock (Peter Price, Missouri throughout the remainder of the WSOW is not avail Division of Geology and Land Survey, oral commun., 1995). able. The overburden at monitoring well MWS-08 (pi. 1) contains 20 ft of white to cream-colored clay, Overburden Geology tentatively identified as kaolinite, that is interpreted to be part of the residuum. This occurrence of kaolinite The stratigraphy of overburden units at the may be similar to kaolinite deposits of the fire clay dis WSCP is presented in the RI report for the WSCP tricts of east-central Missouri. Clay deposits have been (MK-Ferguson Company and Jacobs Engineering reported in St. Charles County, although no mining Group, 1992). Overburden units at the WSOW were has been reported there (McQueen, 1943). Clay depos not identified by the Army as part of their RI, but were its were mined as nearby as St. Louis County to the the subject of a later investigation at the WSTA east of St. Charles County, Warren County to the west, (Rueff, 1992). As part of that study, overburden units and Franklin County to the southwest (Searight and were exposed by excavating several trenches, and bor Patterson, 1967). Clay deposits can occur as filled ings were drilled at the trenches. Also, overburden sinkholes, some of which are in the Burlington- units were identified by interpreting descriptions con Keokuk Limestone (McQueen, 1943). tained in logs previously prepared for the monitoring Basal till, which occurs above the residuum and wells as part of the RI (International Technology Cor poration, 1992), but the overburden samples from the below the glacial till, is described for the WSCP (MK- monitoring wells were not logged. These overburden Ferguson Company and Jacobs Engineering Group, samples were reviewed to identify overburden units as 1992), and this terminology has been adopted for the part of this study (data on file at the office of the U.S. WSOW in this report (fig. 2). This unit, which ranges Geological Survey, Rolla, Missouri). For many moni from 0 to 10 ft thick, is a sandy, clayey, silty gravel, or toring wells, the units that were identified did not gravelly silt, characterized by angular chert loosely agree with the interpretations made by Rueff (1992). bound in a silty matrix. It occurs in areas of bedrock The overburden stratigraphy presented by DOE for the lows and is thin or absent in areas of bedrock highs WSCP (MK-Ferguson Company and Jacobs Engineer (MK-Ferguson Company and Jacobs Engineering ing Group, 1992) and the overburden stratigraphy pre Group, 1992). Basal till has been identified in two sented by Rueff (1992) for the WSTA also differ Army monitoring wells (MWS-03 and MWS-21; pi. slightly. The overburden stratigraphy presented in fig 1) on the east side of the WSTA (monitoring well logs ure 2 for the entire WSOW is intended to unify the two on file at the U.S. Geological Survey Office, Rolla, and, therefore, differs slightly from both. Missouri). 18 Geohydrology of the Weldon Spring Ordnance Works, St. Charles County, Missouri Rueff (1992) identified what was termed a present at monitoring well MWS-108, the glacial out- "preglacial deposit" in four trenches in the south-cen wash is considered a subunit of the glacial till (fig. 2) tral part of the WSTA in the same stratigraphic posi because glacial outwash also has been identified in tion as the basal till. The "preglacial deposit" is two other Army monitoring wells (MWD-106 and described as thin (as much as 4.5 ft thick) silt, silty MWVR-24; pi. 1) with glacial till above and below it. clay, silty sand, and clay. Kaolinite composes 60 to 80 Glacial outwash also may be present below glacial till percent of the clay-size fraction of three samples of the at DGLS trench T-6 (pi. 1). "preglacial deposit" from one trench (Schumacher and The Ferrelview Formation, which overlies the others, 1993). Because at least some of the clay in the glacial till, is a clay to silty clay with scattered sand, "preglacial deposit" may be residual kaolinite, as gravel, and rock fragments. It typically has less sand described previously, this unit may be residual in ori and more clay than the underlying glacial till and has gin. Alternately, Rueff (1992) suggests that the many hairline fractures or macropores (Rueff, 1992). "preglacial deposit" could be glacial outwash, which Theories for the origin of the Ferrelview Formation would likely correlate with glacial outwash deposits include it being glacial till plain sediment or a result of identified in three Army monitoring wells (fig. 2). in-situ weathering of glacial till or loess (Rueff, 1992; Because at least part of the "preglacial deposit" may MK-Ferguson Company and Jacobs Engineering belong to other overburden units, its existence as a dis Group, 1992). The Ferrelview Formation is similar in tinct unit at the WSOW is not clear, and it is not shown appearance to the glacial till. It was difficult to differ in the stratigraphic column for the WSOW in this entiate the two in the review of Army overburden sam report (fig. 2). ples. The distribution of the Ferrelview Formation The glacial till, or clay till of DOE terminology, probably is similar to that of the glacial till. consists of sandy and silty clay to clayey silt, with Loess overlies the Ferrelview Formation (fig. 2). scattered chert, limestone, igneous and metamorphic Rueff (1992) identified two loess units, the Roxana gravel and cobbles. The glacial till also is character Silt and the overlying Peoria Loess. Two loess units ized by hairline fractures and joints (Rueff, 1992; J.G. were not recognized by the DOE until they were iden Schumacher, U.S. Geological Survey, oral commun., tified in 1995 during the drilling of monitoring well 1994). Iron and manganese oxides have been noted MW-4024 (pis. 1, 2; PC. Patchin, written commun., near these fractures as staining and nodules (Rueff, 1995). However, the generic term loess is used by the 1992). This unit occurs throughout most of the WSCP DOE (MK-Ferguson Company and Jacobs Engineer and WSTA, but is thickest in the northern part of the ing Group, 1992) and is used in this report. The loess WSTA (47 ft thick in a boring at DGLS trench T-8), is silty clay to silt, has a sporadic distribution (MK- thins to the south, and is thin to absent along the south Ferguson Company and Jacobs Engineering Group, ern part of the WSTA. The thickness of the glacial till 1992), and can be as much as 11 ft thick. determined for this report at some Army monitoring Locally, alluvium overlies older overburden wells, particularly MWS-05 (0 ft) and MWS-08 (4 ft) units or bedrock (fig. 2). Its composition varies greatly along the southern part of the WSTA, is less than that depending on location and is as much as 120 ft thick in estimated by Rueff (1992; 22 ft at MWS-05; 22.5 ft at the floodplain of the Missouri River (fig. 1). MWS-08). The southern terminus of the glacial till, Variable thicknesses of fill occur throughout the which is due to nondeposition or erosion, is not well WSOW because of past earthmoving activities as part defined, but probably is in the southern part of and in of the construction of the WSOW and WSCP. In places south of the WSTA. The distribution and thick extreme cases (raffinate pit dikes), the fill is as thick as ness of the glacial till north of the WSTA and WSCP 30 ft (MK-Ferguson Company and Jacobs Engineer are not as well known as they are at the WSTA and ing Group, 1992). Alternatively, past earthmoving WSCP because the data are less dense; however, 32 ft activities have removed overburden for use elsewhere of glacial till has been identified at monitoring well as fill. Approximately 15 to 20 ft of overburden is esti MWS-107 (pi. 1). Thirty feet of fining-upward, mated to have been removed at monitoring well medium-coarse sand to clayey, sandy silt that overlies MWS-14 (pi. 1; J.G. Schumacher, oral commun., residuum and underlies the Ferrelview Formation (fig. 1995). 2) has been identified as glacial outwash at monitoring The thickness of the overburden varies through well MWS-108 (pi. 1). Although glacial till is not out the WSOW (pi. 10). The overburden thickness Overburden Geology 19 data for plate 10 are based in part on some new and aquifer; and the definition of a leaky confining unit, reinterpreted top-of-bedrock data that were not used termed the glacial drift confining unit. for previous overburden thickness maps (MK-Fergu- Permeability and hydraulic conductivity data for son Company and Jacobs Engineering Group, 1992; the residuum, basal till, and glacial outwash are lim Rueff, 1992). Data that represent extreme cases of cut ited. The permeability of the residuum is considered to or fill also are not included on plate 10. Isopach lines be variable because of its heterogeneous composition were not extended south of the WSTA and WSCP (MK-Ferguson Company and Jacobs Engineering because of the sparse drill-hole data there. Some of the Group, 1992). Bognar (1991) stated that a hydraulic thickest overburden occurs in the northern part of the conductivity value of 2.8 ft/day (feet per day) for the WSTA and north of the WSTA, but because overbur residuum at the WSCP was estimated by the DGLS den samples were not collected for some of the moni based on data from other locations. Although the toring wells in this area (MWGS- and USGS-series residuum is considered to be part of the shallow aqui monitoring wells), data for individual overburden fer, it may locally be a confining unit where it is partic units do not exist for these wells. The larger overbur ularly clay-rich. Hydraulic conductivity measurements den thicknesses may be caused by larger thicknesses at the residuum/bedrock contact at the WSCP range of glacial drift, rather than thicker residuum. For from 0.4 to 267 ft/day, but these data probably are not example, the glacial till/residuum contact at a boring representative of the residuum (MK-Ferguson Com at the DGLS trench T-8 (pi. 1) is at a depth of 61 ft pany and Jacobs Engineering Group, 1992). The per from the land surface (Rueff, 1992). Less glacial drift meability of the basal till probably is larger than that was deposited south of the bedrock "high" in the of some other overburden units because of its large WSTA (pi. 5), which may be the result of the bedrock sand and gravel content (MK-Ferguson Company and high impeding the flow of the ice sheet to the south or Jacobs Engineering Group, 1992). The glacial out- the removal of glacial drift by postglacial erosion wash is a local feature and is thick at only one moni (Rueff, 1992). Thick overburden occurs in some toring well (MWS-108 where it is 30 ft thick; pi. 1). Its places where the top of the bedrock is low (pis. 5, 10). sandy composition indicates that it is permeable. It is For example, the paleodrainage centered about the considered a part of the shallow aquifer only where no unnamed tributary to Dardenne Creek that contains glacial till occurs below it (MWS-108 and possibly Burgermeister spring appears to have been partially DGLS trench T-6; pi. 1). filled by glacial drift, and a surface-water divide now exists southeast of the tributary. Also, the paleovalley The permeability of the glacial till and Ferrel- that extends through the eastern part of the WSCP view Formation is substantially less than that of the aligns with a linear area of thick overburden on the underlying overburden units, the Burlington-Keokuk overburden thickness map. Limestone, and the Fern Glen Formation that compose the shallow aquifer (fig. 2). The hydraulic conductivity of the glacial till at the WSCP averages 6.5 x 10'5 Geohydrologic Units ft/day based on in-situ constant head permeability tests (Bognar, 1991) and averages 3.4 x 10"5 ft/day based on The geohydrologic units in St. Charles County in-situ slug tests (MK-Ferguson Company and Jacobs include an alluvial aquifer and shallow, middle, and Engineering Group, 1992). Hydraulic conductivity deep bedrock aquifers separated from each other by from laboratory measurements ranges from 9.1 x 10"6 confining units (Kleeschulte and Imes, 1994; fig. 2). to 0.01 ft/day and averages 7.4 x 10"5 ft/day for the The St. Francois aquifer is even deeper (fig. 2), but it glacial till and ranges from 1.1 x 10"5 to 0.01 ft/day is at such great depths in St. Charles County that its and averages 1.3 x 10"4 ft/day for the Ferrelview For hydrologic properties and water quality are not well mation at the WSCP (MK-Ferguson Company and known. The geohydrologic units at the WSOW are Jacobs Engineering Group, 1992). In-situ constant head shown in figure 2, which is modified from Kleeschulte permeability tests of the Ferrelview Formation averaged and Imes (1994) for specific conditions at the WSOW. 6.6 x 10'5 ft/day at the WSCP (Bognar, 1991). These modifications are revisions in the stratigraphy The glacial till and the Ferrelview Formation (discussed in the Bedrock Geology and Overburden together, or separately where only one is present, com Geology sections of this report); the inclusion of resi pose the glacial drift confining unit, with the exception duum, basal till, and glacial outwash in the shallow that the glacial outwash subunit is part of the shallow 20 Geohydrology of the Weldon Spring Ordnance Works, St. Charles County, Missouri aquifer where there is no glacial till below it (MWS-108 The weathered and the unweathered units of the and possibly DGLS trench T-6; pi. 1; fig. 2). Because Burlington-Keokuk Limestone are geologic units that ground water as recharge and discharge probably are distinguished from each other based on physical moves in fractures through the glacial till and the Fer- characteristics. Because these physical characteristics relview Formation, the glacial drift confining unit can increase the ability of the weathered unit to transmit be regarded as a leaky confining unit. Although it does water, these units can also be regarded as geohydro- not actually confine ground water throughout most of logic units. For example, the lower RQD of the weath the WSTA and WSCP where the potentiometric sur ered unit as compared to that of the unweathered unit face of the shallow aquifer is below its base, it con is mainly a function of the larger number of mostly fines ground water locally, particularly to the north of horizontal fractures and partings that transmit water. the WSTA and WSCP where the potentiometric sur The voids and breccia zones in the weathered unit also face is above its base. The structure of the base of the are more permeable, although the voids are sometimes glacial drift confining unit, which is the same as the at least partially clay-filled (Carman, 1991). This dis top of the residuum, except where glacial outwash and tinction of the weathered unit and the unweathered basal till locally occur (fig. 2), is shown on plate 11. unit as different geohydrologic units has been recog The structure of the base of the glacial drift confining nized for the WSCP and vicinity by the DOE (MK- unit is similar to the top of bedrock surface (pi. 5); the Ferguson Company and Jacobs Engineering Group, paleodrainage centered about the unnamed tributary to 1992) and can also be applied to the remainder of the Dardenne Creek containing Burgermeister spring and WSOW. Hydraulic conductivity data from both the the bedrock paleovalleys west of and at the WSCP are WSCP and the remainder of the WSOW support this reflected by lows in this surface. Reaches where distinction. Hydraulic conductivities measured by streams have cut through the glacial drift confining DOE for the WSCP and vicinity using slug tests range from 5 x 10'3 to 0.75 ft/day (average of 0.09 ft/day) for unit to expose the underlying shallow aquifer also are 17 monitoring wells completed in the unweathered shown on plate 11. These reaches were approximately unit and from 0.06 to 12.8 ft/day (average of 1.97 located by projecting where streambed altitudes are ft/day) for 7 monitoring wells and piezometers com below the base of the confining unit and examining pleted in the weathered unit (compiled from data in stream banks along parts of Schote Creek and its tribu Durham, 1992). Durham (1992) states that most of the taries. Because the confining unit has been removed in higher hydraulic conductivity values are from moni these reaches, the shallow aquifer can be considered to toring wells in the northern one-half of the WSCP. extend to the land surface. The extent of these condi Hydraulic conductivities measured by the Army for tions transverse to the stream is not known. The gla the WSTA and for the WSOW north of the WSTA and cial till confining unit is thin to absent in other places WSCP using slug tests range from 1.3 x 10'4 to 0.01 including but not limited to the southern part of the ft/day (average of 1.4 x 10~3 ft/day) for 9 monitoring WSTA (pi. 11). The southern terminus of the glacial wells completed in the unweathered unit and from 6.8 till confining unit is probably in the southern part of x 1Q-4 to 0.08 ft/day (average of 0.01 ft/day) for 12 and in places south of the WSTA. monitoring wells completed in the weathered unit Kleeschulte and Imes (1994) include the Fern (compiled from data in International Technology Cor Glen Formation with the Burlington-Keokuk Lime poration, 1993). The difference in the hydraulic con stone in the shallow aquifer. Although hydraulic con ductivities measured by the Army and DOE may ductivity data are insufficient to verify this inclusion reflect different slug test methods used or differences (there is only one monitoring well completed in the in well construction. However, the trend for both sets Fern Glen Formation and four monitoring wells that of measurements is the same the weathered unit gen straddle the Fern Glen Formation/Burlington-Keokuk erally has higher hydraulic conductivities than the Limestone contact), the physical appearance of the unweathered unit. Fern Glen Formation indicates that inclusion in the The strongly weathered subunit of the weath shallow aquifer is warranted. The Fern Glen Forma ered unit is characterized by increased amounts or a tion generally is more porous and vuggy than the greater intensity of the same characteristics that distin lower, unweathered Burlington-Keokuk Limestone, guish the more permeable weathered unit from the less and it probably is at least as permeable. permeable unweathered unit. These characteristics Geohydrologic Units 21 include lower RQD, lower core recovery, more breccia itoring wells include those that are presently (1996) and vugs, and increased porosity. This subunit would, active, inactive, and have been abandoned. The open therefore, appear to be a more permeable unit than the interval consists of the well screen and sand filter pack rest of the weathered unit. However, because monitor or the uncased part of open bedrock wells. This map ing wells generally are only partially completed in the facilitates correlation of data from well to well strongly weathered subunit, hydraulic conductivity throughout the WSOW, regardless of whether the data are sparse, and the hydrologic significance of the wells are Army or DOE monitoring wells. Because of strongly weathered subunit has not been clearly dem long completion intervals for some DOE monitoring onstrated. Two DOE monitoring wells are completed wells, many more monitoring wells at and in the vicin exclusively in the strongly weathered subunit; a slug ity of the WSCP are completed in both the weathered test was performed on one of these. Four Army moni and unweathered units than there are at the WSTA or toring wells are completed exclusively in the strongly other parts of the WSOW. Many of the Army monitor weathered subunit; slug tests were performed on two ing wells at the WSTA are completed in the weathered of these. Hydraulic conductivities determined from 8 unit of the Burlington-Keokuk Limestone, but the base packer tests exclusively on the strongly weathered of this unit was not penetrated during the drilling of subunit ranged from 0.25 to 24 ft/day (average of 8.57 some of these monitoring wells. Fewer Army monitor ft/day), and hydraulic conductivities from 16 packer ing wells are completed in the unweathered unit of the tests exclusively on the weathered unit without any Burlington-Keokuk Limestone than DOE monitoring strongly weathered subunit ranged from less than 1.8 x wells. Some of the deeper Army monitoring wells are 10'3 to 25.8 ft/day (average of 3.42 ft/day; compiled at least partially completed in units below the Burling from data in Bechtel National, Inc., 1987). ton-Keokuk Limestone. Geologic data are not avail The weathered unit, residuum, basal till, and able to determine specific units in which most of the USGS-series monitoring wells and some DOE moni glacial outwash (where there is no glacial till below it) toring wells are completed. Several clusters of two or is the upper, more permeable part of the shallow aqui more monitoring wells exist and, especially at the fer, which overlies the lower, less permeable part of WSCP, commonly consist of one monitoring well the shallow aquifer (unweathered unit of the Burling- completed in the weathered unit and one completed in ton-Keokuk Limestone and the Fern Glen Formation; the unweathered unit. Other monitoring well clusters fig. 2). The contact between the upper and lower parts consist of one monitoring well straddling the weath of the shallow aquifer is gradational. A thickness map ered unit/unweathered unit contact and the other well of the upper part of the shallow aquifer is shown on completed in only one of these units (pi. 13). Other plate 12. The upper part of the shallow aquifer is combinations exist, including well clusters with one thickest at two monitoring wells (MWD-15 and MW- well completed in the overburden unit and the other 4003; pis. 1, 8) where the weathered unit is thickest. A well completed in the weathered unit, or with one of partial thickness of the upper part of the shallow aqui the monitoring wells in a unit below the Burlington- fer is shown on plate 12 for much of the WSTA Keokuk Limestone. because the bottom of the weathered unit was not pen etrated by many monitoring wells. The bedrock pale- ovalley that extends through the eastern part of the Ground-Water Flow WSCP (pi. 5) is reflected as a thin upper part of the shallow aquifer (pi. 12) because the weathered unit is Ground-water flow at the WSOW has been thin there (pi. 8). Generally, the upper part of the shal described previously both at a small scale for the low aquifer thins to the north, reflecting the thin to WSTA and the WSCP (MK-Ferguson Company and absent weathered unit north of the WSTA and WSCP. Jacobs Engineering Group, 1992; International Tech The thickness of the upper part of the shallow aquifer nology Corporation, 1993) and at a larger scale for all also is larger in the vicinity of monitoring well MWS- of St. Charles County (Kleeschulte and Imes, 1994). 108 (pi. 1) because of the thick (30 ft) glacial outwash The latter report includes the results of simulation of at this location. ground-water flow for the three-aquifer system. This The geologic units in which monitoring wells section is not a comprehensive description of all are completed are shown in tables 1 and 2 and are aspects of ground-water flow at the WSOW. Instead, shown on a well completion map (pi. 13). These mon this section presents interpretations of ground-water 22 Geohydrology of the Weldon Spring Ordnance Works, St. Charles County, Missouri flow in the shallow aquifer at the WSOW that are are normally or occasionally dry. The upward hydrau based on an improved understanding of the geohydro- lic head differences and the overburden monitoring logic framework of the WSOW resulting from this wells that are dry probably are the result of topo study. graphic positions and locations adjacent to streams. The WSCP is located in part of the shallow Most monitoring wells and well clusters are along aquifer recharge area. This is demonstrated for the streams that have either been classified as losing WSCP by downward hydraulic head gradients in most streams (Missouri Division of Geology and Land Sur monitoring well clusters, most of which have the vey, 1991; Price, 1991) or not classified but where deeper monitoring well completed in the unweathered streambed altitudes are above the potentiometric sur unit. Historical hydraulic head differences for these face. The potentiometric surface is below the bottom well clusters range from less than 1 ft to generally less of the overburden monitoring wells that are dry. The than 10 ft, although a few monitoring well clusters upward hydraulic head differences between monitor have larger hydraulic head differences. One well clus ing wells along streams that are completed in the over ter (MW-2018 and MW-2019; pi. 2) historically shows burden and the bedrock indicate upward ground-water a hydraulic head difference of as much as 25 ft (data flow. Ground water discharges to gaining reaches of on file at the U.S. Geological Survey office, Rolla, streams, but does not discharge to streams where the Missouri). The vertical component of the hydraulic potentiometric surface is below the streambed. head gradient at this well cluster, measured between Instead, ground water can flow from the bedrock to the midpoints of the open intervals of the monitoring the overburden where the overburden is permeable. wells, is approximately 0.43 ft of hydraulic head per Both upward and downward hydraulic head dif foot of altitude. Monitoring well clusters composed of ferences exist at Army monitoring well pairs com a monitoring well completed in the weathered unit and pleted in the bedrock at the WSTA. Less than a 2-ft a deeper well straddling the weathered unit/unweath- upward hydraulic head difference historically exists ered unit contact show historical downward hydraulic between monitoring well MWD-02, which is com head differences that generally are less than 1 ft. pleted in the unweathered unit of the Burlington- The WSTA generally is considered part of the Keokuk Limestone, and monitoring well MWS-02, recharge area for the shallow aquifer. However, histor which is completed mostly in the weathered unit of the ical water-level data collected by the Army show that Burlington-Keokuk Limestone (pi. 1). An upward both downward and upward hydraulic head differ hydraulic head difference of less than 0.5 ft also exists ences exist (International Technology Corporation, between monitoring wells MWD-06 and MWS-06 (pi. 1995), depending on local conditions. Downward 1), both of which are completed in the unweathered hydraulic head differences indicate ground-water unit. An upward hydraulic head difference of 12 to 17 recharge, and upward hydraulic head differences may ft exists between monitoring well MWD-05, com indicate local discharge zones along streams. Down pleted in the Fern Glen Formation, and monitoring ward hydraulic head differences are more common at well MWS-05, which straddles the Burlington- Army monitoring well clusters consisting of a moni Keokuk Limestone/Fern Glen Formation contact (pi. toring well completed in the overburden unit and at 1). These two monitoring wells are located along a least one monitoring well completed in the bedrock. A stream in a steeply incised valley (pi. 1). An upward downward hydraulic head difference ranging from less hydraulic head difference ranging from 30 to 50 ft than 1 ft to as much as 6 ft exists most or all of the exists between monitoring wells MWD-18 and MWS- time at six of these monitoring well clusters. However, 18 (pi. 1), which also are located in a steeply incised an upward hydraulic head difference of less than 2 ft valley. Both of these monitoring wells are completed historically exists between one monitoring well com in formations deeper than the Fern Glen Formation pleted in the bedrock and its paired monitoring well and, therefore, are below the shallow aquifer (table 1; completed in the overburden (MWS-09 and MWV-09; fig. 2). However, the water-level measurements for pi. 1). Upward hydraulic head differences of less than monitoring well MWS-18 are suspect, possibly 2 ft also occasionally exist at two other monitoring because of poor hydraulic connection between the well pairs completed in the overburden and bedrock aquifer and the monitoring well (Price, 1991). Historic (MWV-01 and MWS-01, MWV-13 and MWS-13; pi. downward ground-water hydraulic head differences 1). Six monitoring wells completed in the overburden between Army bedrock monitoring well pairs at the Ground-Water Flow 23 WSTA generally were about 1 ft between monitoring Land Survey, 1991; Price, 1991). The altitudes of wells MWS-09 (completed in the strongly weathered perennial streams and springs were used as data val subunit of the weathered unit) and MWD-09 (com ues; potentiometric contours were drawn below the pleted in the unweathered unit) and generally less than altitudes of intermittent streams and springs. 2 ft between monitoring wells MWS-15 and MWD-15 The potentiometric surface map of the shallow (which are both completed in the weathered unit). aquifer (pi. 14) shows a large ground-water mound in Limited water-level data from recently (1995) the south-central part of the WSTA. This mound is installed monitoring wells indicate downward hydrau part of a generally east-west trending ground-water lic head differences of approximately 1 ft between ridge through the WSTA and WSCP that defines a monitoring wells MWS-23 (completed in the weath ground-water divide approximately coincident with ered unit) and MWD-23 (completed in the unweath the surface-water divide. The ground-water ridge indi ered unit), and approximately 4 ft between monitoring cates ground-water recharge. Areas north and south of wells MWS-25 (completed in the weathered unit) and the ground-water ridge are downgradient from it. The MWD-25 (completed mostly in the unweathered unit). downgradient position of monitoring wells USGS-02, A potentiometric surface map of the shallow USGS-07 (pi. 1), and MWGS-03 (approximately 0.8 aquifer was prepared using mainly water-level mea mi north of the central part of the study area) is surements collected by the USGS on September 25 reflected by small tritium concentrations in water sam and 26, 1995 (pi. 14; Schumacher and others, 1996). ples from these wells (Schumacher, 1993). Water levels measured in September 1994 (Schuma Precipitation that percolates downward through cher and others, 1996) were used for a few monitoring fractures in the glacial drift confining unit recharges wells for which water-level measurements in Septem the shallow aquifer. Where this unit is not present, ber 1995 were not available. The different measure such as where the streams have incised through it (pi. ment date did not affect the position of potentiometric 11) and probably in parts of the southern part of the contours because the water levels generally do not WSTA and south of the WSTA, precipitation can be vary substantially with time (Kleeschulte and Imes, expected to recharge the shallow aquifer more readily. 1994). For the same reason, this map is considered to Reaches where the streams are projected to have be representative of the potentiometric surface at any eroded through the glacial drift confining unit (pi. 11) time. Where water-level measurements were available correspond to some of the losing stream reaches that for two or more monitoring wells in a well cluster, the are identified in Missouri Division of Geology and measurement in the uppermost unit was used. Mea Land Survey (1991), Price (1991), and Kleeschulte surements of perched ground water that exists locally and Emmett (1986) and are shown on plate 14. The in the overburden at the WSCP (MK-Ferguson Com removal of the glacial drift confining unit and expo pany and Jacobs Engineering Group, 1992) were not sure of the underlying shallow aquifer facilitates the used. Because the water level in the weathered unit loss of streamflow to the subsurface. can be expected to be higher than in the underlying Ground-water flow in the upper part of the shal unweathered unit in recharge areas and where only low aquifer is not limited to the weathered unit of the one well is present and it is in the unweathered unit, Burlington-Keokuk Limestone, but can also occur the water level was not used except as a general guide locally in permeable overburden units. The relation of to position potentiometric contours. Where no weath the potentiometric surface of the shallow aquifer (pi. ered unit is present and the unweathered unit is at the 14) and the top of bedrock (pi. 5) is shown on plate 15. top of the bedrock, as is the case for some monitoring This relation also is shown in hydrogeologic sections wells north of the WSTA and WSCP away from the A-A (fig. 3) and B-B' (fig. 4). The potentiometric sur main area of recharge, the water level in the unweath face is below the top of bedrock for most of the ered unit generally was used. Where the only well recharge area along the ground-water divide, and parts present straddles the weathered unit/unweathered unit of the permeable weathered unit and strongly weath contact, as is the case for many of the DOE monitoring ered subunit are unsaturated. Locations where the wells surrounding the WSCP, the water level was potentiometric surface is above the top of bedrock (pi. used. Other information used to position potentiomet 15) indicate the potential for ground-water flow in per ric contours on plate 14 is the altitude of the stream- meable overburden units. However, ground water may beds and springs (Missouri Division of Geology and be confined to the bedrock in some places by clay-rich 24 Geohydrology of the Weldon Spring Ordnance Works, St. Charles County, Missouri zones in the residuum. During drilling, the overburden Wildlife Area (monitoring wells MWS-105 and was dry at some monitoring wells until drilling pene MWD-105; MWS-106 and MWD-106; MWS-107 and trated the overburden/bedrock contact (M. Jank, Inter MWD-107; MWS-109 and MWD-109; and MWS-112 national Technology Corporation, oral commun., and MWD-112; pi. 1). Hydraulic heads above land 1995). Therefore, ground-water flow may not occur in surface exist at monitoring well MWD-106 and some the overburden in all areas indicated on plate 15. The times at monitoring well MWS-106. Other ground- potential for ground-water flow in permeable overbur water discharge features in the northern part of the den units exists at places along the ground-water study area include Burgermeister and other springs ridge, along parts of bedrock paleovalleys at the (Missouri Division of Geology and Land Survey, WSCP where the top of bedrock is low (MK-Ferguson 1991; Price, 1991) and the gaining unnamed tributary Company and Jacobs Engineering Group, 1992; pis. 5, to Dardenne Creek upstream of Burgermeister spring 15), in the north central part of the WSTA, and (Kleeschulte and Emmett, 1986), although other throughout much of the August A. Busch Memorial streams reaches in the vicinity are losing (pi. 14). In Wildlife Area north of the WSTA and WSCP, down- the northern part of the WSOW, north of the study gradient from the ground-water ridge. Generally, the area, ground water discharges to Dardenne Creek, residuum and locally other overburden units of the which flows to the Mississippi River (Kleeschulte and shallow aquifer, particularly the 30-ft thick glacial out- Imes, 1994; fig. 1). Where the aquifer is confined in wash subunit at monitoring well MWS-108 (pi. 1), discharge areas, ground water probably discharges potentially become more important as mediums of mainly through fractures in the glacial drift confining ground-water flow north and downgradient of the unit. ground-water ridge, but are probably less important Burgermeister spring is an important point of where clay-rich zones in the residuum confine ground ground-water discharge, and it contains contaminants water below in the bedrock. Also, because the thick that can be traced to operations at the WSCP and ness of the weathered unit generally decreases to the WSOW (Schumacher, 1993). From 1985 through north and the unit is absent at several monitoring wells 1990, the mean annual discharge from the spring at the August A. Busch Memorial Wildlife Area (pi. ranged from 0.19 to 0.26 ft3/s (cubic foot per second; 8), the weathered unit generally becomes a less impor Kleeschulte and Imes, 1994). Ground water discharg tant medium of ground-water flow downgradient to ing from Burgermeister spring has been traced from the north, and the more permeable upper part of the the east fork of the west tributary of Schote Creek, shallow aquifer becomes thinner (pi. 12). with a traveltime estimated between 12 and 24 hours, Along the ground-water ridge that defines the and from the middle fork of the west tributary of recharge area, the potentiometric surface of the shal Schote Creek, with a travel time of 62 hours (Missouri low aquifer generally is well below the base of the gla Division of Geology and Land Survey, 1991). Both of cial drift confining unit (pi. 16). The presence of an these tributaries are in a different surface-water basin unsaturated thickness of the shallow aquifer below the than Burgermeister spring. Ground-water flow to confining unit means that the aquifer is an unconfined Burgermeister spring also has been traced from angle (water table) aquifer in this area, even though it is hole AH-2004 (pi. 2), with a traveltime of 2-1/2 to 3 below a confining unit. Downgradient to the north, the days, and from MW-2032 (pi. 2), with a traveltime of potentiometric surface gradually rises in relation to the 7 to 9 days (P.C. Patchin, oral commun., 1996). Other base of the confining unit (pi. 16; figs. 3, 4). Farther sources of ground water to Burgermeister spring north, the potentiometric surface is above the base of include the raffinate pits and probably the east tribu the glacial drift confining unit over a large area, indi tary of Schote Creek (Schumacher, 1993). A potentio- cating that the aquifer is confined (pi. 16; figs. 3, 4). metric-surface trough centered around Burgermeister This area of confined conditions is centered around the spring indicates the convergence of ground-water flow unnamed tributary to Dardenne Creek that contains to the Burgermeister spring area (pi. 14). This trough Burgermeister spring and discharges to Lake 34 (pi. approximately aligns with the bedrock paleodrainage 16). (pi. 14). This alignment has been interpreted to indi Upward ground-water gradients, indicating cate that depressions on the top of bedrock (paleoval- ground-water discharge, exist at the five Army moni leys) may be areas of increased permeability toring well clusters at the August A. Busch Memorial (Kleeschulte and Imes, 1994). Ground-Water Flow 25 Ground-water flow in the shallow aquifer has Keokuk Limestone is unsaturated, and the potentio been characterized as diffuse with superimposed dis metric surface of the shallow aquifer is in the Fern crete flow zones (Kleeschulte and Imes, 1994). Dye Glen Formation (pi. 14). The intersection of the top of traces (Missouri Division of Geology and Land Sur the Chouteau Group (pi. 3) with the potentiometric vey, 1991; Price, 1991) demonstrate discrete ground- surface is approximately shown as a dotted line on the water flow to springs. Although monitoring well den potentiometric surface map, south of which the Fern sity decreases north of the WSCP, existing data indi Glen Formation is unsaturated. This line is the south cate that the weathered unit thins to the north, ern boundary of the saturated part of the shallow aqui including along the flow path to Burgermeister spring fer. (pi. 8). The weathered unit is absent at monitoring well MWD-105, which is along the flow path, and at moni toring well MWD-106, which is near Burgermeister SUMMARY spring (pis. 1, 8). Because of this and the existence of the bedrock paleodrainage, ground water that flows A geohydrologic description of the Weldon toward Burgermeister spring may have a substantial Spring ordnance works (WSOW) was developed to component that flows through the residuum or at the facilitate the correlation of water-quality data between residuum/bedrock contact. Also, as ground water U.S. Army (Army) and U.S. Department of Energy flows toward Burgermeister spring, the shallow aqui (DOE) monitoring wells and, thereby, contribute to the fer changes from an unconfined to a confined aquifer understanding of the extent of contamination and (pi. 16; figs. 3, 4). Ground water flows from one sur potential spread of contamination at the WSOW. The U.S. Geological Survey (USGS) conducted a study face-water basin to another, but, based on existing from 1993 to 1996 in cooperation with the U.S. Army data, does not cross a subsurface bedrock high. The Corps of Engineers (COE) to create a common data topographic high that separates surface-water basins is base for Army and DOE geohydrologic data, and to not due to a subsurface bedrock high, but is instead use these together with USGS and Missouri Division due to an increased thickness of overburden that may of Geology and Land Survey (DGLS) data to develop be glacial in origin (pis. 5, 10). a comprehensive geohydrologic description of the Little monitoring well data exist south of the WSOW, exclusive of the Weldon Spring quarry WSTA and WSCP to trace ground-water flow from the (WSQ). east-west trending ground-water ridge that represents The WSOW is on the extreme northeast flank of the recharge area. A number of perennial and intermit the Ozark Dome. Uplift of the Ozark Dome produced tent springs occur along the deeply incised tributaries a broad area of Paleozoic rocks that dip peripherally to the Missouri River in this area, particularly in the away from the Precambrian St. Francois Mountains in southeastern part of the WSOW, and dye traces to southeastern Missouri. This regional dip, together with some of these springs have been conducted (Missouri the northwest-trending Eureka-House Springs Anti Division of Geology and Land Survey, 1991; Price, cline located about 1 mile southwest of the WSOW, 1991). These springs are mostly in the Burlington- accounts for the northeast dip of the rocks at the Keokuk Limestone (Missouri Division of Geology and WSOW about 60 feet per mile for the top of the Land Survey, 1991). Generally, the potentiometric Chouteau Group. The Burlington-Keokuk Limestone surface gradient is greater to the south than to the of Mississippian age is the uppermost bedrock unit north of the ground-water ridge, reflecting the topo throughout most of the WSOW. Bedrock units older graphic control over the potentiometric surface. than the Burlington-Keokuk Limestone crop out in the Because the bedrock dips to the northeast, the potenti southern part of the WSOW, a consequence of north ometric surface slopes counter to it south of the east dipping strata and deep incision by tributaries to ground-water divide, whereas it slopes in the same the Missouri River. direction north of the divide. Because of the bedrock The top of the bedrock forms a generally east- dip, bedrock units become progressively older to the west trending ridge in the southern to central part of southwest. The intersection of the top of the Fern Glen the Weldon Spring training area (WSTA) and the Formation (pi. 4) with the potentiometric surface is southern part of the Weldon Spring chemical plant approximately shown on the potentiometric surface (WSCP). Because subsurface data are sparse south of map as a dashed line, south of which the Burlington- the WSTA, the top of bedrock is approximated in this 26 Geohydrology of the Weldon Spring Ordnance Works, St. Charles County, Missouri area. The top of the bedrock north of the ridge, where thin compared to that at the WSCP and WSTA. Except monitoring well data are available, contains a large, for two monitoring wells where the weathered unit is broad bedrock low centered about the unnamed tribu unusually thick, the thickness of the weathered unit tary to Dardenne Creek that contains Burgermeister ranges from 0 to 66.5 feet. The strongly weathered spring. This is interpreted to be a paleodrainage that subunit has a more limited distribution than the weath existed before the deposition of glacial drift. This fea ered unit. ture consists of smaller, more elongate paleovalleys at The overburden units are, in ascending order: and west of the WSCP where more dense drill hole residuum, basal till, glacial till, including a glacial out- data provide better definition. wash subunit, the Ferrelview Formation, loess, allu The un weathered unit of the Burlington-Keokuk vium, and fill. The residuum is variable in compo Limestone is a light to medium gray, coarse to less sition, ranging from clay-rich to chert-rich, contains commonly fine crystalline, thin to massive bedded, chert, silt, and sand, locally contains limestone frag fossiliferous, cherty limestone that can be silty or ments, and is locally kaolinite-rich. The basal till is a argillaceous, or can locally be dolostone or siltstone. sandy, clayey, silty gravel, or gravelly silt, character The contact between the Burlington-Keokuk Lime ized by angular chert loosely bound in a silty matrix. stone and the underlying Fern Glen Formation is gra- The glacial till consists of sandy, silty clay to clayey dational and difficult to identify because of their facies silt, with scattered chert, limestone, igneous, and relation. The weathered unit of the Burlington-Keokuk metamorphic gravel and cobbles, and is characterized Limestone, which overlies the unweathered unit where by hairline fractures and joints with iron and manga both are present, is characterized by alterations that nese oxide staining and nodules. As much as 30 feet of have been superimposed on the rock by weathering. fining-upward, medium-coarse sand to clayey, sandy These alterations are lithology and color changes, an silt, identified as glacial outwash, has locally been increase in porosity, and an increase in mostly hori identified as a subunit of the glacial till. The Ferrel zontal fractures and partings, some of which have view Formation overlies the glacial till and is a clay to undergone solution. The silty and argillaceous lime silty clay with scattered sand, gravel and rock frag stone and siltstone, as well as the purer limestone, ments, with typically less sand and more clay than the commonly are orangish-brown because of discolora underlying glacial till, and with many hairline frac tion by iron oxides. This discoloration permeates the tures or macropores. The Ferrelview Formation is sim rock as well as occurring along fracture and parting ilar in appearance to the glacial till, and it was difficult surfaces. Vugs and voids, some of which are associ to differentiate the two in the review of Army overbur ated with breccia, can be filled or partially filled by den samples. Overlying the Ferrelview Formation is clay or a mixture of clay, silt, and chert gravel, and the loess, which is silty clay to silt and has a sporadic dis removal of this fill by drilling fluid results in poor core tribution. Locally, alluvium and fill overlie older over recovery. Loss of fluid during drilling also is associ burden units or bedrock. Some of the thickest over ated with zones of core loss. Weathering features burden occurs in the northern part of the WSTA and occur throughout the Burlington-Keokuk Limestone, north of the WSTA and may be caused by a larger but are more common in the weathered unit. A thickness of glacial drift, rather than thicker residuum. strongly weathered subunit of the weathered unit has The paleodrainage centered about the unnamed tribu been identified where these features are particularly tary to Dardenne Creek that contains Burgermeister abundant or intense. Where present, it occurs as a sin spring appears to have been partially filled by glacial gle subunit at the top of the weathered unit at the drift, and a surface-water divide now exists southeast WSTA, but can occur as more than one subunit any of the tributary. where in the weathered unit at and in the vicinity of The shallow aquifer of a previously defined the WSCP. three-bedrock-aquifer system for St. Charles County The weathered unit is present at all the monitor was modified in this study to include permeable over ing wells and geotechnical borings at the WSTA and burden units (residuum, basal till, and glacial outwash the WSCP, except at one where the Burlington- where there is no glacial till below it) with the Burl Keokuk Limestone is not present. At the August A. ington-Keokuk Limestone and the Fern Glen Forma Busch Memorial Wildlife Area, north of the WSTA tion. The shallow aquifer was further defined by an and WSCP, the weathered unit is absent or is generally upper, more permeable part, which consists of the per- Summary 27 meable overburden units and the weathered unit of the ridge, but are probably less important where clay-rich Burlington-Keokuk Limestone, and a lower, less per zones in the residuum confine ground water below in meable part, which consists of the unweathered unit of the bedrock. Because the thickness of the weathered the Burlington-Keokuk Limestone and the Fern Glen unit generally decreases to the north and is absent at Formation. Generally, the upper part of the shallow several monitoring wells at the August A. Busch aquifer thins to the north, reflecting the thin to absent Memorial Wildlife Area, the weathered unit generally weathered unit north of the WSTA and WSCP. becomes a less important medium of ground-water A glacial drift confining unit, consisting of parts flow downgradient to the north. of the glacial till and the Ferrelview Formation, was Along the ground-water ridge that defines the defined in this study. Because ground water as re recharge area, the potentiometric surface of the shal charge and discharge probably move in fractures low aquifer generally is well below the base of the gla through this unit, it is considered to be a leaky confin cial drift confining unit, indicating that the aquifer is ing unit. Although it does not actually confine ground an unconfined aquifer in this area. Downgradient to water throughout most of the WSTA and WSCP the north, the potentiometric surface is above the base where the potentiometric surface of the shallow aqui of the glacial drift confining unit over a large area, fer is below its base, it confines ground water locally, indicating that the aquifer is confined. Upward particularly to the north of the WSTA and WSCP ground-water gradients measured in monitoring well where the potentiometric surface of the shallow aqui pairs, Burgermeister and other springs, the gaining fer is above its base. There are stream reaches where unnamed tributary to Dardenne Creek upstream of the streams have cut through the glacial drift confining Burgermeister spring, and Dardenne Creek indicate unit to expose the underlying shallow aquifer. ground-water discharge in the northern part of the WSOW. A potentiometric surface map of the shallow aquifer shows a large ground-water mound in the south-central part of the WSTA. 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Charles County, Missouri, 1987-90: U.S. Geological Price, Peter, 1991, Shallow groundwater investigations at Survey Open File Report 93-648, 106 p. the Weldon Spring training area, St. Charles County, McQueen, H.S., 1943, Geology of the fire clay districts of Missouri: Rolla, Missouri Division of Geology and east central Missouri: Rolla, Missouri Division of Land Survey, 74 p. Geology and Land Survey, v. 28, 2nd sen, 250 p. Roberts, C.M., 1951, Preliminary investigation of ground- McCracken, M.H., 1971, Structural features of Missouri: water occurrences in the Weldon Spring area, St. Rolla, Missouri Division of Geology and Land Survey Charles County, Missouri, with further notes on Prob Report of Investigations 49, 99 p. with plate. lems of the Weldon Spring area, Missouri, by C.V. References Cited 29 Theis: U.S. Geological Survey Open-File Report 82- Searight, W.V., and Patterson, S.H., 1967, Fire clay, in U.S. 1008, 36 p. Geological Survey, and Missouri Division of Geology Rueff, M.L., 1992, Surficial materials investigation at the and Land Survey, 1967, Mineral and water resources Weldon Spring training area, St. Charles County, Mis of Missouri: U.S. 90th Congress, 1st Session, Senate souri: Rolla, Missouri Division of Geology and Land Document 19, 399 p.; also Missouri Geological Survey Survey Report 92-91-GS, 41 p. and Water Resources, v. 43, 2nd ser., p. 107-111. Schumacher, J.G., 1990, Geochemical data for the Weldon Snyder, F.G., 1968, Tectonic history of midcontinental Spring chemical plant site and vicinity property, St. United States, in UMR Journal: University of Mis- Charles County, Missouri 1989-90: U.S. Geological souri-Rolla, p. 65-78. Survey Open-File Report 90-351, revised in 1991, Thompson, T.L., 1986, Paleozoic succession in Missouri, 47 p. part 4, Mississippian system: Rolla, Missouri Division 1993, Geochemistry and migration of contaminants of Geology and Land Survey Report of Investigations at the Weldon Spring chemical plant site, St. Charles 70, 182 p. County, Missouri 1989-91: U.S. Geological Survey 1995, The stratigraphic succession in Missouri: Open-File Report 93-433, 102 p. Rolla, Missouri Division of Geology and Land Survey, Schumacher, J.G., Merton, L.M., Hockanson, E.A., and v. 40, 2nd series, revised, 190 p. DeRusseau, S.N., 1996, Hydrologic and water-quality Whitfield, J.W, 1989, Geologic map of the Defiance 7 1/2' data for the Weldon Spring ordnance works, St. quadrangle, St. Charles County, Missouri: Rolla, Mis Charles County, Missouri 1992-95: U.S. Geological souri Division of Geology and Land Survey Open-File Survey Open-File Report 96-218, 101 p. Map 89-255-GI, scale 1:24,000. Schumacher, J.G., Sutley, S.J., and Cathcart, J.D., 1993, Whitfield, J.W, Brill, K.G., and Krummel, W.J., 1989, Geo Geochemical data for the Weldon Spring training area logic map of the Weldon Spring 7 1/2' quadrangle, St. and vicinity property, St. Charles County, Mis Charles County, Missouri: Rolla, Missouri Division of souri 1990-92: U.S. Geological Survey Open-File Geology and Land Survey Open-File Map 89-252-GI, Report 93-153, 84 p. scale 1:24,000. 30 Geohydrology of the Weldon Spring Ordnance Works, St. Charles County, Missouri C/) LLJ CO Table 1. Stratigraphic and selected well construction data for U.S. Army monitoring wells, USGS-series and MWGS-series monitoring wells, and the Army well [Except as noted, stratigraphic intervals are interpretations of the cored interval only and are not extrapolated above or below the cored interval or from nearby wells; BK, Burlington-Keokuk Limestone; SW, strongly weathered subunit of the weathered unit of the Burlington-Keokuk Limestone; W, weathered unit of the Burlington-Keokuk Limestone; UNW, un weathered unit of the Burlington-Keokuk Limestone; FG, Fern Glen Formation; CH, Chouteau Group; BCH, Bachelor Formation; SS, Sulphur Springs Group; MK, Maquoketa Shale; KM, Kimmswick Limestone; DC, Decorah Group; PT, Plattin GeohydrologyoftheWeldon Limestone; JM, Joachim Dolomite; SP, St. Peter Sandstone; ft, feet; OVB, overburden; ?, questionable; --, not present; ND, no data; DGLS, Missouri Division of Geology and Land Survey; values are depths below land surface, in feet, except as noted; well construction data from International Technology Corporation (1993) and from data on file at the U.S. Geological Survey, Rolla, Missouri] Unit interval Burlington-Keokuk Limestone (BK) Land Strongly a surface Filter-pack or Top of weathered Weathered Unweathered Fern Glen Chouteau 5' altitude Units to which open-hole bed subunit unit unit Formation Group (O (ft above well is open interval rock BK (SW) (W) (UNW) (FG) (CH) O Well sea level) (thickness in ft)a (ft) (ft) (ft) (ft) (ft) (ft) (ft) (ft) 3 MWV-01 595.8 OVB 7.3-15.0 15.0 ND ND ND ND ND ND Works,ice MWS-01 b 595.9 BK(12W, 5 UNW) 26.0-43.0 15.2 15.2-44.6C 15.2-23.0 15.2-38.0 38.0-44.6C ND ND MWV-02 603.1 OVB 8.8-16.8 17.0 ND ND ND ND ND ND r* MWS-02 603.9 BK(15.3W,2.7UNW) 37.8-55.8 15.5 ND ND ND ND ND ND 3-O MWD-02b 604.1 BK (UNW) 107.5-125.0 17.1 d 17.1-133.5C 17.1-27.4C 17.1-53.3C 53.3-133.5 133.5-149.3C ND 5" MWS-03b 633.7 BK (2.7 W, 14.3 UNW/ 46.0-63.0 41.0 41.0-59.5C - 41.0-48.7 48.7-59.5c ND ND (0 O MWS-04b 622.5 BK(11.4SW, 7.6 W) 20.6-39.6 11. Od 11.0-39.6c'e 11.0-32.06 1 1 .0-39.6c'e ND ND ND 0c MWS-05 599.1 BK (5.6 UNW)/FG (17.6) 43.8-67.0 35.0 ND ND ND ND ND ND Missouri MWD-05b 599.1 FG(18)/CH(0.1) 98.0-116.1 37.0 37.0-49.4 37.0-41.4 41.4-49.4 49.4-116.0 116.0-138.6 MWS-06 619.8 BK (UNW) 40.0-60.0 21.8 ND ND ND ND ND ND MWD-06b 619.9 BK (UNW) 112.1-129.5 21.9 2 1.9-1 50. Oc 21.9-37.5 21.9-37.5 37.5-150.0c ND ND MWS-07b 639.4 BK (10.6 SW, 8.4 W/'g 44.0-63.0 43. 5d 43.5-60.0c'e 43.5-54.6c 43.5-60.0c'e ND ND ND MWV-08 688.8 OVB 9.8-23.8 23.8 ND ND ND ND ND ND MWS-08b 688.9 BK(7.5SW, 7.5W/g 27.5-42.5 26.5d 26.5-41 .5C 26.5-35.0 26.5-41. 5C ND ND ND MWV-09 634.5 OVB 10.4-25.4 25.4 ND ND ND ND ND ND MWS-09 634.2 BK (SW) 31.6-46.6 25.0 ND ND ND ND ND ND MWD-09b 634.6 BK (UNW) 121.4-146.0 25.8 25.8-151. l c 25.8-53.0 25.8-53.0 53.0-151. l c ND ND MWS-10b 652.5 BK (SW) 27.0-43.0 23.1 24.0-60.0c'h 24.0-54.0h 24.0-54.0h 54.0-60.0C ND ND MWS-ll b 674.8 BK(5.1 SW, 11.2W/ 40.7-57.0 30.5 30.5-55.0C 30.5-45.8 30.5-55.0C ND ND ND MWS-12b 655.0 BK (3 SW, 14 W) 31.0-48.0 22.1 22.5-49.1 c'h 22.5-34.0h 22.5-49. l c'h ND ND ND Table 1 . Stratigraphic and selected well construction data for U.S. Army monitoring wells, USGS-series and MWGS-series monitoring wells, and the Army well Continued Unit interval Sulphur Bachelor Springs Maquoketa Kimmswick Decorah Plattin Joachim St. Peter Formation Group Shale Limestone Group Limestone Dolomite Sandstone (BCH) (SS) (MK) (KM) (DC) (PT) (JM) (SP) Well (ft) (ft) (ft) (ft) (ft) (ft) (ft) (ft) Remarks MWV-01 ND ND ND ND ND ND ND ND MWS-01 b ND ND ND ND ND ND ND ND MWV-02 ND ND ND ND ND ND ND ND MWS-02 ND ND ND ND ND ND ND ND Units open to well based on MWD-2 stratigraphy MWD-02h ND ND ND ND ND ND ND ND Top of bedrock at 13.2? MWS-03b ND ND ND ND ND ND ND ND MWS-04b ND ND ND ND ND ND ND ND Top of bedrock at 14.6? MWS-05 ND ND ND ND ND ND ND ND Units open to well based on MWD-5 stratigraphy MWD-05b 138.6-140.8 140.8-1 50.5C ND ND ND ND ND ND 9 MWS-06 ND ND ND ND ND ND ND ND Top of bedrock and units open to well based on to'0) MWD-6 stratigraphy D> MWD-06b ND ND ND ND ND ND ND ND TJ 3; o' MWS-07b ND ND ND ND ND ND ND ND Top of bedrock at 37.5 or 54.6? D> O. MWV-08 ND ND ND ND ND ND ND ND w 9 MWS-08b ND ND ND ND ND ND ND ND Top of bedrock at 33.0? »a o. MWV-09 ND ND ND ND ND ND ND ND ». MWS-09 ND ND ND ND ND ND ND ND Unit open to well based on MWD-9 stratigraphy o 0 MWD-09b ND ND ND ND ND ND ND ND 3 2 MWS-10b ND ND ND ND ND ND ND ND c o o' MWS-ll b ND ND ND ND ND ND ND ND 3 MWS-12b o»O. ND ND ND ND ND ND ND ND D> Table 1. Stratigraphic and selected well construction data for U.S. Army monitoring wells, USGS-series and MWGS-series monitoring wells, and the Army well Continued o Unit interval Sulphur Bachelor Springs Maquoketa Kimmswick Decorah Plattin Joachim St. Peter Formation Group Shale Limestone Group Limestone Dolomite Sandstone (BCH) (SS) (MK) (KM) (DC) (PT) (JM) (SP) Well (ft) (ft) (ft) (ft) (ft) (ft) (ft) (ft) Remarks MWV-13 ND ND ND ND ND ND ND ND MWS-13b ND ND ND ND ND ND ND ND MWS-14b ND ND ND ND ND ND ND ND Top of bedrock at 35.0? MWS-15 ND ND ND ND ND ND ND ND Top of bedrock and units open to well based on MWD-15 stratigraphy; auger refusal in MWS-15 at 15.0 MWD-15b ND ND ND ND ND ND ND ND Top of bedrock at 16.0 (auger refusal) or 34.0? MWV-16 ND ND ND ND ND ND ND ND MWS-16b ND ND ND ND ND ND ND ND MWV-17 ND ND ND ND ND ND ND ND MWS-17b ND ND ND ND ND ND ND ND MWV-18 ND ND ND ND ND ND ND ND a9 MWS-18 ND ND ND ND ND ND ND ND Units open to well based on MWD-18 stratigraphy to MWD-18b 70.0-71.1 71.1-91.0 _ 91.0-150.3° ND ND ND ND too MWS-19Ab'j ND ND ND ND ND ND ND ND f) to MWS-19b ND ND ND ND ND ND ND ND Previously referred to as MWS-19B a. V) (D MWS-20b ND ND ND ND ND ND ND ND (D MWS-21 b ND ND ND ND ND ND ND ND * MWV-22 ND ND ND ND ND ND ND ND 2. 0 MWS-22b ND ND ND ND ND ND ND ND o 3 MWS-23b ND ND ND ND ND ND ND ND % 5 o'Z MWD-23b ND ND ND ND ND ND ND ND 3 MWV-24b'j a. ND ND ND ND ND ND ND ND a MWS-24b ND ND ND ND ND ND ND ND tA MWVR-24 ND ND ND ND ND ND ND ND Table 1. Stratigraphic and selected well construction data for U.S. Army monitoring wells, USGS-series and MWGS-series monitoring wells, and the Army well- Continued Geohydrologyol Unit interval Burlington-Keokuk Limestone (BK) Land Strongly theWe: surface Filter-pack or Top of weathered Weathered Unweathered Fern Glen Chouteau altitude Units to which open-hole bed subunit unit unit Formation Group (ft above well is open interval rock BK (SW) (W) (UNW) (FG) (CH) Q. Well (ft) (ft) O sea level) (thickness in ft)a (ft) (ft) (ft) (ft) (ft) (ft) Wo MWS-25 680.8 BK(W) 47.0-59.6 36.2 ND ND ND ND ND ND to MWD-25b 681.1 BK(0.8W, 11. 5 UNW) 102.2-114.5 36.5 36.5-114.5° 36.5-103.0 103.0-114.5° ND ND MWS-26b OrdnanceW 672.4 BK(W) 41.5-54.5 40.6 40.6-65.0° 40.6-65.0° ND ND ND MWS-101 b 489.5 KM 50.0-85.0 44.0 MWS-102b 479.2 DC 57.5-90.0 53.0 o MWS-103b ------v> 527.7 SS (5)/KM (32) 28.0-65.0 24.0 <« MWS-104b 564.7 BK(20.9W, 12.2UNW/ 22.9-56.0 15.5 16.1-54.9°'h --? I6.1-43.8h 43.8-54.9° ND ND o MWS-105 573.7 BK (UNW) 30.2-69.2 28.7 ND ND ND ND ND ND 5" MWD-105b 573.7 BK(15.1 UNW)/FG(21.9)f 115.3-152.3 28.9 28.9-130.4 .. 28.9-130.4 130.4-150.0° ND O o MWS-106 530.7 BK (UNW) 25.0-48.0 21.8 ND ND ND ND ND ND | MWD-106b 531.0 BK(18.1 UNW)/FG(15.4) 114.7-148.2 23.5 23.5-132.8 - 23.5-132.8 132.8-151.5° ND Missouri MWS-107b 607.2 BK (26.5 W, 7 UNW) 52.0-85.5 49.0 49.0-85.5° 49.0-78.5 78.5-85.5° ND ND MWD-107b 607.2 BK (UNW) 121.5-134.0 46.0 46.0-134.0° 46.0-79.0 79.0-134.0° ND ND MWS-108b 604.4 BK (UNW)f 52.0-85.0 50.3 50.3-84.3° -- 50.3-84.3° ND ND MWS-109 550.3 BK (UNW) 41.2-75.5 22.0 ND ND ND ND ND ND MWD-109b 550.4 BK ( 1 9.8 UNW)/FG( 14.4) 105.1-139.3 21.8 21.8-124.9 - 21.8-124.9 124.9-149.8° ND MWS-110b 604.8 BK(24W, 10.5 UNW) 55.0-89.5 15.5 15.5-89.5° 15.5-79.0 79.0-89.5° ND ND MWS-lll b 620.8 BK(W) 42.0-75.2 35.5 35.7-75.2°'h 35.7-75.2°'h ND ND ND MWS-112b 572.6 BK (4.8 W, 7.7 UNW) 23.7-36.2 18.0 18.0-62.5° 18.0-28.5 28.5-62.5° ND ND MWD-112 572.9 BK (UNW)? 93.3-105.8 18.3 ND ND ND ND ND ND Table 1. Stratigraphic and selected well construction data for U.S. Army monitoring wells, USGS-series and MWGS-serfes monitoring wells, and the Army well Continued Unit interval Sulphur Bachelor Springs Maquoketa Kimmswick Decorah Plattin Joachim St. Peter Formation Group Shale Limestone Group Limestone Dolomite Sandstone (BCH) (SS) (MK) (KM) (DC) (PT) (JM) (SP) Well (ft) (ft) (ft) (ft) (ft) (ft) (ft) (ft) Remarks MWS-25 ND ND ND ND ND ND ND ND Top of bedrock and units open to well based on MWD-25 stratigraphy MWD-25b ND ND ND ND ND ND ND ND MWS-26b ND ND ND ND ND ND ND ND MWS-101 b - - - 44.0-85.0C ND ND ND ND MWS-102b - - - 53.0-54.0 54.0-90.0C ND ND ND MWS-103b - 24.0-33.0 - 33.0-65.3C ND ND ND ND MWS-104b ND ND ND ND ND ND ND ND Strongly weathered subunit from 22.9 to 43.8? MWS-105 ND ND ND ND ND ND ND ND Units open to well based on MWD- 1 05 stratigraphy MWD-105b ND ND ND ND ND ND ND ND MWS-106 ND ND ND ND ND ND ND ND Units open to well based on MWD-106 stratigraphy GO MWD-106b ND ND ND ND ND ND ND ND S MWS-107b ND ND ND ND ND ND ND ND 1 MWD- 107 ND ND ND ND ND ND ND ND o'3- MWS-108b ND ND ND ND ND ND ND ND D» 3 Q. MWS-109 ND ND ND ND ND ND ND ND Units open to well based on MWD- 1 09 stratigraphy U (D (D MWD-109b ND ND ND ND ND ND ND ND (0s Q. MWS-110b ND ND ND ND ND ND ND ND 2. MWS-lll b ND ND ND ND ND ND ND ND o 0 MWS-112b ND ND ND ND ND ND ND ND u c MWD- 112 ND ND ND ND ND ND ND ND Retrofit of USGS-7; top of bedrock from MWS-112 S o 3 Q. S 5> Table 1. Stratigraphic and selected well construction data for U.S. Army monitoring wells, USGS-series and MWGS-series monitoring wells, and the Army well Continued o 1 Unit interval Q. 5 Burlington-Keokuk Limestone (BK) 0 o Land Strongly surface Filter-pack or Top of weathered Weathered Unweathered Fern Glen Chouteau (D altitude Units to which open-hole bed subunit unit unit Formation Group 1 (ft above well is open interval rock BK (SW) (W) (UNW) (FG) (CH) Q. Well sea level) (thickness in ft)a (ft) (ft) (ft) (ft) (ft) (ft) (ft) (ft) 0 3 USGS-1 589 BK (UNW) 57-107 38? 38(?)-107c'J ND 38-48 ? 48-107c ? ND ND T35'-i USGS-2 554 BK at 50 50k at 50* ND ND ND ND ND (0 O USGS-2A 559 OVB (24)?/BK (57) 50? 50(?)-107c'j ND ND ND ND a. 26-107 ND 3 D> USGS-3 585 BK 66-80 66k 66-80c'j ND ND ND ND ND O (D USGS-4 601 BK 30-107 30k 30-107CJ' ND ND ND ND ND O USGS-5 580 BK 23-87 23k 23-87c'J ND ND ND ND ND f 56(?)-107c'j r* USGS-6 590 BK (UNW) 70-107 56? ND 56-70 ? 70-107 ? ND ND 3"O USGS-71 572.9 BK (UNW)? 32-105.8 18.3 1 8.3-1 05.8C-J ND ND ND ND ND 5"D> USGS-8 625 BK 60-107 60k 60-107C'J ND ND ND ND ND w 0 USGS-9 590 BK 24-90 24k 24-90c'J ND ND ND ND ND 0c 3 v? MWGS-1 647.7 ?/KM ?-320 22.6 ND ND ND ND ND ND 55' MWGS-2m 647.1 JM(14)/SP(16.5) 631-661.5 22 22-180 ND ND ND 180-245 245-265 w co MWGS-3 485 BK ?-98.5 29.7 ND ND ND ND ND ND MWGS-4 484.7 ?/KM ?-310 29.4 ND ND ND ND ND ND MWGS-5m 485.3 SP? 612-620 30 30-135 ND ND ND 135-185 185-228 Army Well 670 BK(103.5)/FG(50)/ 41.5-235 41.5k 110-145 ND ND ND 145-195 195-223 (DGLS 4843) CH(28)/SS(12) Table 1. Stratigraphic and selected well construction data for U.S. Army monitoring wells, USGS-series and MWGS-series monitoring wells, and the Army well Continued Unit interval Sulphur Bachelor Springs Maquoketa Kimmswick Decorah Plattin Joachim St. Peter Formation Group Shale Limestone Group Limestone Dolomite Sandstone (BCH) (SS) (MK) (KM) (DC) (PT) (JM) (SP) Well (ft) (ft) (ft) (ft) (ft) (ft) (ft) (ft) Remarks USGS-1 ND ND ND ND ND ND ND ND Top of bedrock and units identified from gamma log USGS-2 ND ND ND ND ND ND ND ND Well open only at bottom of casing USGS-2A ND ND ND ND ND ND ND ND Top of bedrock assumed to be same as USGS-2 (top of bedrock in USGS-2A was earlier picked at 26 ft) USGS-3 ND ND ND ND ND ND ND ND USGS-4 ND ND ND ND ND ND ND ND USGS-5 ND ND ND ND ND ND ND ND USGS-6 ND ND ND ND ND ND ND ND Top of bedrock and units identified from gamma log USGS-71 ND ND ND ND ND ND ND ND Well has been retrofitted to MWD-1 12; top of bedrock from MWS- 112 USGS-8 ND ND ND ND ND ND ND ND USGS-9 ND ND ND ND ND ND ND ND CO 3 MWGS-1 ND ND ND ND ND ND ND ND Top of bedrock approximated from MW-4019 (nearby); units open to well based on stratigraphy in paired well MWGS-2 3a 3" o' MWGS-2m - 265-285 285-296 296-400 400-428 428-540 540-645 645-66 1.5C Top of bedrock approximated from MW-4019 (nearby) D> a MWGS-3 ND ND ND ND ND ND ND ND Top of bedrock and units open to well based on W MWGS-5 stratigraphy; MWGS-3, MWGS-4, and (D [Stratigraphic intervals are interpretations of the cored interval only and are not extrapolated above or below the cored interval, or from nearby wells; BK, Burlington-Keokuk Limestone; SW, strongly weathered subunit of the weathered unit of the Burlington-Keokuk Limestone; W, weathered unit of the Burlington-Keokuk Limestone; UNW, unweathered unit of the Burlington-Keokuk Limestone; ft, feet; OVB, overburden; ?, questionable; , not present; ND, no data; values are depths below land surface, in feet, except as noted; except as noted, data are from P.C. Patchin, Morrison Knudsen Corporation; Julie Reitinger, MK-Ferguson Company; and MK-Ferguson Company and Jacobs Engineering Group (1992)] Unit interval Burlington-Keokuk Limestone (BK) Land Strongly surface Filter-pack or Top of weathered altitude Units to which open-hole bed subunit Weathered Unweathered z? (ft above well is open interval rock BK (SW) unit (W) unit (UNW) D> Well sea level) (thickness in ft)a (ft) (ft) (ft) (ft) (ft) (ft) Remarks MW-2001 b - 3- 611.8 BK (21.7 W, 10.7 UNW)C 31.6-64.0 26.5 26.5-60.0d 26.5-53.3 53.3-60.0d o' MW-2002b 28.5-60.0d'f - 28.5-60.0d'f D> 623.8 BK (W)c 31.7-64.0 28.5e ND Top of bedrock at 24.5 (auger a3 refusal)?; paired with MW-2021 MW-2003b 38.8-59.0d'f 38.8-59.0d'f 1 637.1 BK (3.7 W, 2.5 SW, 7.3 W, 41.5-64.0 38.8e 45.2-47.7 ND Top of bedrock at 32.5 (auger n 9.0 SW)° 55.0-59.0d refusal)? o 3 (0 MW-20048 642.8 BK (9.6 W, 4.9 SW, 1.2 W, 54.3-77.0 37.0e 37.0-72.0d'f 37.0-5 1.7f 37.0-70.0f 70.0-72.0d Top of bedrock at 51.7?; paired with 7.0 UNW)C 63.9-68.8 MW-2029 nC 5' MW-2005 635.7 BK(1.7SW, 6.8 W, 50.0-81.0 44.8e 44.8-76.0d'f 44.8-5 1.7f 44.8-76.0d'f ND Top of bedrock at 32.7?; paired with 3 a 3.8 SW, 18.7W)C 58.5-62.3 MW-2022 of MW-2006 634.2 BK(3.5W, 3.8 SW, 6.6 W, 27.0-71.0 22.6 22.6-65.5d 30.5-34.3 22.6-58.1 58.1-65.5d Paired with MW-2026 cf 6.9 SW, 1 0.3 W, 12.9 40.9-47.8 c UNW)C V) MW-2007 651.9 BK (9.3 W, 4.4 SW, 13W, 62.3-99.0 59.0 59.0-94.0d 71.6-76.0? 59.0-89.0 89.0-94.0d Possible SW 59.0-66.8; 10.0 UNW)c'h -Q SW 71.6-76.0 is questionable D> 3. MW-2008b'S 622.7 BK(17.3W, 11.7UNW)C 34.0-63.0 31.5 31.5-57.0d - 31.5-51.3 51.3-57.0d Paired with MW-2025 (D MW-20098 636.3 BK (SW)C 27.2-58.6 20.5 20.5-54.0d 20.5-54.0d 20.5-54.0d ND m MW-2010 642.9 BK (W)c 37.2-64.0 32.8 32.8-59.0d - 32.8-59.0d ND 3 (D (2 MW-2011 653.2 BK (34.8 W, 7.7 UNW)C 36.5-79.0 32.0 32.0-74.0d - 32.0-71.3 71.3-74.0d Paired with MW-2030 3 MW-2012b 634.8 BK(21.7W, 18.5UNW)C 29.3-69.5 25.5 25.5-60.0d 25.5-51.0 51.0-60.0d o 3_ MW-2013 645.4 BK (28.7 W, 15.0 UNW)C 31.3-75.0 27.5 27.5-70.0d .. 27.5-60.0 60.0-70.0d Clustered with MW-2027 and O 5' MW-2033 (Q MW-2014 647.6 BK(7.2W, 10.8 SW, 37.0-64.0 33.0 33.0-59.0d 33.0-36.7 33.0-59.0d ND 2. 9.0 W)c 44.2-55.0 w MW-2015 657.7 BK(0.4SW, 1 5.3 W, 4.7 47.3-86.0 45.5 45.5-80.5d 45.5-47.7 45.5-70.4 70.4-80.5d Paired with MW-2028 Jv SW, 2.7 W, 15.6UNW)C 63.0-67.7 Table 2. Stratigraphic and well construction data for U.S. Department of Energy monitoring wells Continued o 9 Unit interval O3- Q. Burlington-Keokuk Limestone (BK) 3 o CO Land Strongly O surface Filter pack or Top of weathered Unweathered "£ altitude Units to which open-hole bed subunit Weathered unit 9 (ft above well is open interval rock BK (SW) unit (W) (UNW) Well sea level) (ft) (ft) (ft) Remarks 9 (thickness in ft)a (ft) (ft) (ft) O. O MW-2016b 635.7 BK(1.8SW, 86.0UNW)C 62.7-150.5 54.0 57.7-1 48. 6d'' 57.7-64.5' 57.7-64.5' 64.5-148.6d Clustered with MW-2023, MW- COg 2024, and MW-2032 5' MW-2017 657.9 BK(4.0SW, 14.2W, 30.0-69.0 23. 5C 23.5-64.0d'f 23.5-34.0f 23.5-61.8 f 61.8-64.0d Top of bedrock at 29.0?; contacts of CO 6.8 SW, 6.8 W, 48.2-55.0? lower SW interval questionable; O 7.2 UNW)C paired with MW-2034 Q. 3 Q) 3 MW-2018 661.7 BK (SW)C 37.4-69.0 32.5 32.5-65.0d 32.5-65.0d 32.5-65.0d ND Paired with MW-2019 O » MW-2019 661.5 BK (UNW)C 103.0-116.4 ND 81.0-116.0d-' ND ND 81.0-116.0d'' Paired with MW-2018 9 MW-2020) 655.1 BK (7.5 SW, 23.8 W, 36.5-119.6 23.7C 36.5-1 19.6d'j 36.5-44.0' 36.5-67.8' 67.8-119.6d Top of bedrock questionable -» 51.8UNW)h because roller bit was used to r* 36.5; W/UNW at 47.5?; retrofit 3-O ofMW-2044 Q> MW-2021 b 624.6 BK (UNW)C 96.3-111.0 ND 81.5-110.7d'' ND ND 81.5-110.7d'' Paired with MW-2002 (0 MW-2022 636.1 BK (UNW) 112.0-126.5 ND 100.5-128.0d'' ND ND 100.5-1 28. Od'' Paired with MW-2005 o0 c 3 MW-2023 635.8 BK (UNW) 68.5-91.5 ND ND ND ND ND No log; unit open to well based on ? stratigraphy in MW-2016; clus 55's tered with MW-2016, MW-2024, (0 and MW-2032 O c MW-2024 634.9 BK (UNW) 135.0-149.6 ND ND ND ND ND No log; unit open to well based on stratigraphy in MW-2016.; clus tered with MW-2016, MW-2023, and MW-2032 MW-2025b'S 622.2 BK (UNW) 94.0-108.6 ND 70.5-1 08 .6d-' ND ND 70.5-108.6d'' Paired with MW-2008 MW-2026 634.8 BK (UNW) 105.5-118.0 ND 81.0-118.0d'' ND ND 81.0-118.0d'' Paired with MW-2006 MW-2027 644.3 BK (UNW)C 107.0-122.0 ND 80.2-120.0d'' ND ND 80.2-120.0d-' Clustered with MW-2013 and MW-2033 MW-2028 657.8 BK (UNW)C 116.0-131.5 ND 9 1.6- 131. 2*' ND ND 91.6-131.2d-i Paired with MW-201 5 MW-2029*5 643.1 BK (UNW) 89.0-101.3 ND ND ND ND ND No log; unit open to well based on stratigraphy in paired well MW- 2004 MW-2030b 652.9 BK (12 W, 16.5 SW) 30.5-59.0 29.5 29.5-60.9d 42.5-60.9d 29.5-60.9d ND Paired with MW-2011 Table 2. Stratigraphic and well construction data for U.S. Department of Energy monitoring wells Continued Unit interval Burlington-Keokuk Limestone (BK) Land Strongly surface Filter pack or Top of weathered Unweathered altitude Units to which open-hole bed subunit Weathered unit (ft above well is open interval rock BK (SW) unit (W) (UNW) Well sea level) (thickness in ft)a (ft) (ft) (ft) (ft) (ft) (ft) Remarks MW-2031« 660.6 OVB (3.0VBK (9.5 W) 55.0-67.5 58.0 58.0-67.5d - 58.0-67.5d ND 9 MW-2032 635.8 OVB (5.2)/BK (5.4 W)h 48.0-58.6 53.2e 53.2-60.0d'f 53.2-60.0d-f ? ND Top of bedrock at 48.5 (auger (5*D> refusal)?; W/UNW at 58.5?; clustered with MW-2016, a> MW-2023, and MW-2024 3- o' MW-2033 644.8 OVB (0.1)/BK (23.1 W) 23.1-46.3 23.2 23.2-47.5d _ 23.2-47.5d ND Clustered with MW- 2013 and Q> MW-2027 a MW-2034 658.2 BK (14.3 W, 3.4 SW, 34.5-60.0 34.5 34.5-60.0d 48.8-52.2 34.5-60.0d ND Paired with MW-20 17 1 7.8 W) o 0 I MW-2035 667.0 BK(10.3 W, 4.4UNW) 62.8-77.5 35.0 35.0-77.5d 35.0-59.5 35.0-73.1 73.1-77.5d c o MW-2036 655.9 BK(2.7SW,2.6W1.6 52.5-68.0 46.0 46.0-68.0d 46.0-55.2 46.0-64.6 64.6-68.0d oSt. SW, 5.2 W, 3.4 UNW) 57.8-59.4 3 a MW-2037 656.7 BK (SW)C 45.5-63.5 40.0C 40.0-6 1.0d-f 40.0-6 1.0d'f 40.0-6 1.0d'f ND Top of bedrock at 43.5? a>% MW-2038 665.0 ND 55.0-71.5 52.5 ND ND ND ND Rock not cored; no samples or log ^ C MW-2039 663.4 ND 53.3-69.0 44.5 ND ND ND ND Rock not cored; no samples or log 0 MW-2040 662.4 ND 54.5-74.0 44.5 ND ND ND ND Rock not cored; no samples or log "§(D MW-2041 661.6 ND 61.5-82.0 43.0 ND ND ND ND Rock not cored; no samples or log (D MW-2042 662.7 ND 56.0-77.5 43.5 ND ND ND ND Rock not cored; no samples or log