ML20353A293

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Enclosure 16 - Response to Request for Additional Information - Soil & Materials Engineers, Inc., 1982, Ground-Water Hydrology of the Westinghouse Electric Corporation Plant, Richland County, South Carolina: Report No. H-8119, March 1, 1982
ML20353A293
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Site: Westinghouse
Issue date: 12/18/2020
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Westinghouse
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Office of Nuclear Material Safety and Safeguards
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LTR-RAC-20-94, EPID L-201-RNW-0016
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WESTINGHOUSE NON-PROPRIETARY CLASS 3 6 to LTR-RAC-20-94 Date: December 18, 2020 Enclosure 16 Response to Request for Additional Information Soil & Material Engineers, Inc., 1982, Ground-Water Hydrology of the Westinghouse Electric Corporation Plant, Richland County, South Carolina: Report No. H-8119, March 1, 1982

SOIL & MATERIAL ENGINEERS INC: ENGINEERING-TESTING-INSPECTION 1302 Elmore Street, Columbia, South Carolina 29203 Phone (803) 252-5101 March 1, 1982 Davis & Floyd Engineers 1319 Reynolds Street P.O. Box 428

~ Greenwood, S.C. 29646 Attention: Mr. Carl Burrell

Subject:

Submission of Final Report, "Ground-Water Hydrology *Of the Westinghouse Electric Corporation Plarit, Richland County, South Carolina" S&ME Report No. H-8119 i

Gentlemen:

As authorized, Soil & Material Engineers, Inc. has completed the ground-water hydrology study for the above referenced project. This report summarizes the results of our investigation and our conclusions regarding the hydrologic properties of strata beneath and in the immediate vicinity of the subject site. The report also contains our evaluations of the previous on-site investigations, and a summary of regional geologic and hydrogeologic investigations made in southern Richland County.

Soil & Material Engineers, Inc. appreciates the opportunity to have worked with Davis & Floyd Engineers and Westinghouse Electric Corporation. Should you or your client have any questions concerning the results of the study or this report, do not hesitate in contacting us.

Yours very truly, SOIL & MATERIAL ENGINEERS, INC.

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B. C. Spigner, RPG Senior Hydrogeologist Hydr9logy Division W. Everett Glover,Jr.,PE Senior Engineer S.C. Registration No. 8561

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GROUND-WATER HYDROLOGY of the WESTINGHOUSE ELECTRIC CORPORATION PLANT RICHLAND COUNTY, SOUTH CAROLINA f*

t SOIL. & MATERJAL ENGINEERS, INC.

Hydrology Division 3025 McNaughton Drive Columbia, S.C. 29206 S&ME Rept. No. H-8119 March 1, 1982 SOIL* MATERIAL ENGINEERS INC

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l GROUND-WATER HYDROLOGY OF THE l WESTINGHOUSE ELECTRIC CORPORATION PLANT RICHLAND COUNTY, SOUTH CAROLINA r

I CONTENTS Page r-1

! 1. O

SUMMARY

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.,,.. 2. 0 INTRODUCTION 2.1 Background and Purpose .of Study 2 2.2 Scope---------------------------------------------------------- 5 f

l 2. 2.1 Scope of This Study and Report ------------------------- S

2. 2. 2 Area of Investigation -------------------:...---------------- S
2. 2. 3 .

Investigation Methods ------------------------------------

7 2.3 Previous Studies------------------------------------------------ 11

2. 3.1 On-Site Studies ------------------------------------------ 11
2. 3. 2 Regional Studies ----------------------------------------- 11 3.0 REGIONAL GEOLOGY AND HYDROLOGY
3. 1 Physiography--Stratigraphy--Climate ----------*------------------ 13 3.-1.1 Physiography and Climate ------------"-------------------- 13
3. 1. 2 Geologic Setting--Stratigraphy and Structure ------------:- 14 3.1.3 Summary of Geologic Formations --------------------------- 17

-i Basement Rocks---------------------------------------- 17 Tuscaloosa Formation ----:----------:---------------------- 17 Black Mingo Formation ---------------------------------- 18 Pliocene-Pleistocene Formations -------------------------- 20 3.2 Regional Hydrology----------------------------------------------- 21

3. 2. 1 Ground-Water Occurrence ---------------------------------- 21
3. 2. 2 Major Aquifer Systems and Ground-Water Use -------------- 24 Tuscaloosa Aquifer System ------------------------------ 24 Black Mingo Aquifer System ----------------------------- 26 Unconfined Aquifer System ------------------------------ 28 SOIL* MATERIAL ENGINEERS INC,

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4. O HYDROGEOLOGY OF THE SITE 4.1 Ground-Water Occurrence and Hydrogeologic Units --------------- - 29
4. 1. 1 General Overview ----------------------------------------- 29 I 4. 1. 2 Terrace Aquifer System (Unit I) -------------------------- 30 Available Data. Occurrence and Distribution ---=--:-------- 30 Thickness & Lit~ology _______ .;.. ___________________________ 30 Water-Bearing Properties -------------------------------- 31
4. 1. 3 Black Mingo Aquifer System ------------------------------- 32 Available Data. Occurrence and Distribution ------------ 32 Hydrogeologic Unit 11 ---------------------------------- 34 Hydrogeologic Unit . 111 ---------------------------------- 34
4. 1. 4 Tuscaloosa Aquifer System* ::._---=-:----*-:-_:;__-:-- ----------------- .35
4. 2 Hydraulic Properties ---------,---------------------.,..--------------- 37
4. 2.1 General Principles ----------------------------------------- 37
4. 2. 2 Hydraulic *Properties. of the Terrace Unit ------------------- 38
4. 2. 3 Hydraulic Properties of the Black Mingo Units --------------* 40 I 4. 3 Utilization and Movement of Ground Water ----------------:--------- 41 1,
4. 3. 1 General Concepts and Ground-Water Pumpage -------------- 41

', 4.3.2 Lateral Ground-Water Flow--Terrace Unit ------------------ 42

4. 3. 3 Vertical Ground-Water Flow--Leakage ---------------------- 44 I.*
' 5. 0

SUMMARY

OF CONCLUSIONS i.

5. 1 Hydrogeologic Units and Ground-Water Movement ---------:--------- 46
5. 2 Ground-Water Monitoring Program - - - - ----------------------- 47
6. 0 SELECTED REFERENCES ---------------------------------------------- 49 APPENDICES ----------------------------------------------------. ---------- 50 ii SOIL lo MATl!IIIAL ENGINE&IIS INC

ILLUSTRATIONS FIGURE Page 2-1 Map of Central South Carolina Showing Location of the WEC Plant and Vicinity----------------:-------------------- 3 2-2 Detailed Map of the WEC Plant Site Showing Topography, Waste Facilities, and Monitor Wells (modified from Davis and Floyd, 198~)----------------------------------------- (in pocket) 2-3 Map of Southern Richland County Showing Locations of Selected Water Wei ls-------------------------------------- -6 3-1 Generalized Geologic Cross-Section, A-A'-, of Southern Richland County----------------------------------------- -16 Generalized North-South Hydrogeologic Cross-Section 8-8 1 ,

of the WEC Site (showing Major Hydrogeologic Units and Gamma-Log Correlations)-------------------.:.. ____________ _ _(in pocket) 4-2 North-South Hydrogeologic Cross-Section C-C', of the Terrace Hydrogeologic Unit between Process Area and Sunset Lake-------------------------*-------------------- (in pocket) 4-3 East-West Hydrogeologic Cross-Section D-D' of the Terrace Hydrogeologic Unit South of the Process Area---- (in pocket) 4-4 North-South Hydrogeologic Cross-Section of the Terrace and Upper Black Mingo Hydrogeologic Units at *the WEC Site-----------. ---------------------- *------------------- (in pocket)

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4-5 Potentiometric Map of the Terrace Unit WEC Site, November 15, 1981---------------------------------------- (in pocket) 4-6 Map of the WEC Site showing locations of Monitor Wells---- (in pocket)

SOIL* MATERIAL ENGINEERS INC.

TABLES Page

' 3-1 Summary of Data on Selected Wells in Sbutheastern Richland County, S. C. -------------------------------- (Appendix)

'l-1 Summary of Hydraulic Conductivity Data on the Terrace Unit, WEC Site, (data from LETCo, 1980a)------------- 39 4-1 Summary of Water-Level Data at the WEC Site---------- (Appendix)

'l-3 Stratigraphic Log of Stratigraphic Test Hole ST 3q_.: ___ _ (Appendix)

SOIL & MATERIAL ENGINEERS INC.

1.0

SUMMARY

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The WEC site is underlain by four hydrogeologic units; from land surface, these are: the Terrace Unit (Unit I), the Upper Black Mingo Unit (Unit II),

f an artesian sand aquifer (Unit 111) within the Black Mingo Formation, and the

! Tuscaloosa Formation (Unit IV).

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I The hydrogeology of the Terrace Unit in the area between the main plant I

and Sunset Lake was adequately documented during a study by Davis & Floyd

    • ,*..i Engineers and Law Engineering Testing Company (Davis & Floyd, 1980); LETCo, (1980a, 1980b). The information compiled by Davis & Floyd and LETCo, and the additional information compiled during this study indicates that ground water within the Terrace Unit occurs under water-table conditions and that the lateral flow of ground water within this unit is toward the south-southwest. Interpretations of I

ground-water movement in this unit, ~a~e from water-level. measurements in November 1981, supports the original conclusions of Davis & Floyd and LETCo.

This lateral flow is strongly influenced by topography, locations of recharge and discharge areas, and horizontal stratification of beds within this unit. Therefore, the movement of contaminants in the Terrace Unit will be predominantly by lateral flow in the direction of ground-water movement. A small spring, a man-made pond, and Sunset Lake are natural discharge areas for the Terrace Unit, and their lower topographic elevation exerts the dominant influence on the hydraulic gradient on the water table. Therefore, these natural discJ,arge areas would likely limit the lateral movement of contaminants past Sunset Lake.

, The Black Mingo Formation underlies the Terrace Unit, and two hydrogeologic t units have been defined within this formation: the upper unit (Unit II) is a confining bed, and the lower unit (Unit 111) is an artesian sand aquifer. Hydro-geologic Unit 11 is composed predominantly of clay and shale. The lithology, thickness, and estimated extremely low vertical hydraulic conductivity (K') of this unit in the area south of the main plant indicates that this unit should be an effective confining bed. It should greatly reduce the probability of vert_ical migration of contaminants through this unit. Even if vertical hydraulic conductivities were several orders of magnitude greater than estimates provided in this report. much greater vertical hydraulic gradients than now exist would be needed to cause downward vertical leakage of contaminants into underlying aquifers.

SOIL a MATERIAL ENGINEERS INC.

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2. O INTRODUCTION

2.1 BACKGROUND

AND PURPOSE OF STUDY l The Westinghouse Electric Corporation (WEC) Plant is located in southern Richland County, South Carolina (Fig. 2-1)

  • The plant site is located in the upper
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Coastal Plain, with some of the site property lying within the flood plain of Mill Creek, a tributary of the Congaree River- The main manufacturing building is constructed on ancient terrace deposits at an elevation of approximately 1110 ft above MSL (mean sea level).

Various wastewater treatment facilities and operations are located immediately southwest of the main building and were described in a report by Davis & Floyd, Inc. (1980). Thus, it is not necessary to review these in detail here. These fac:;ilities, site topography, monitor well locations and other features are shown in Fig. 2-2 (Appendix). a map from the Davis & Floyd (1980)

  • report.

., Immediately southwest of these wastewater treatment facilities, a small man-made pond and Sunset Lake lie on the flood plain of Mill Creek at elevations of approximately 115-125 ft MSL. A small spring discharges into the northern edge of the small pond. According to the report by Davis & Floyd, a hydrogeologic investigation was initiated in 1980 when elevated concentrations of fluoride and ammonia nitrogen were detected in the pond and the spring.

As part of the Davis & Floyd investigation, 28 shallow monitoring wells were installed in 1980 by Law Engineering & Testing Company (LETCo). Two reports by LETCo contain descriptions. of the well installation, shallow stratigraphy and hydrogeology of a portion of the WEC site (LETCo, 1980a, 1980b). Water sampling and hydrogeologic analyses by Davis & Floyd indicated that the shallow Terrace aquifer southwest of the main plant building was contaminated and that ground water in the Terrace aquifer flowed in a south-southwesterly direction toward the pond and Sunset Lake. Subsequent to the investigation by Davis & Floyd, Inc.,

WEC and regulatory officials questioned the need for additional monitoring wells and whether it is likely that deeper aquifers beneath or adjacent to the site could become contaminated.

In September, 1981, Soil & Material Engineers (S&ME) Inc. was contracted by Davis & Floyd, Inc. to review previous studies and make recommendations as to whether additional hydrogeologic investigations were warranted. At a meeting with SOIL* MATERIAL ENGINEE.RS INC:.

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IUSGS

~-~I" FROM: AUGUSTA, GA. FIGURE 2-1. MAP OF TOPOGRAPHIC MAP CENTRAL S.C. SHOWINC 1 : 250, 000 SOIL I PAATERIAL ENGINEERS iNC. LO~ATION OF THE ENGINEERING.fESTING-INSPECTtON WEC SITE.

a>WMW~ sount CA&OUNA the Dc1vis & Floyd Project Manager and WEC officials 'on September 22, 1981, the following objectives were outlined:

1. Review available hydrogeologic reports for the site and available basic data that have been collected, and determine if the existing monitor-ing network is adequate to monitor the potential movement of contaminants through the shallow aquifer system.

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2. DP.termine, from existing data, if there is a potential for contam-inating deeper fresh-water aquifers bP.neath the site.

In our original proposed scope of work dated October 2, 1981 we outlined the following six tasks or work elements:

1. Meet with WEC officials and the Davis & Floyd Project Manager to review available data, plant facilities, and monitor well locations.
2. Reveiw existing hydrogeological reports of the site.
3. RP.view available well records in the files of State agencies and review other geologic data that* may be available.
4. Obtain geophysical logs of several existing wells at and . in the vicinity of the WF.C site to explore the deeper strata penetrated by existing wells.
5. Attend a meeting with WEC and Davis & Floyd officials to present the preliminary findings of our ini.tial data review, and geophysical logging.
6. Prepare a report of the additionai data collected and review of the existing (Davis & Floyd, 1981) hydrogeological report.

Our preliminary findings and conclusions were presented to the Davis ~ Floyd Project Manager and WEC officials at a meeting on December 11, 1981. At that meeting it was agreed to perform the following consulting services:

1. Of:ltain split-spoon samples from the bottom of Wells W-2 and W-3 to determine the lithology and mineralogy of strata in the bottom of these wells.
2.
  • construct a four-inch diameter monitor well southwest of Well W-15 that would tap the Black Mingo Aquifer System at an approximate depth of 70-80 ft below land surface.
3. Construct a two-inch diameter well located in close proximity to the four-inch diameter well.

These services were to be performed in order to ( 1) estimate the hydraulic characteristics of upper strata within the Black Mingo Aquifer System; ( 2) provide a 4-inch diameter monitoring well tapping the uppermost aquifer within the Black Mingo Aauifer System; and (3) provide a shallow monitor well tapping the Terrace Unit whic:h could be used to monitor piezometric head and water quality.

SOIL & MATERIAL ENGINEERS INC.

r 2.2 SCOPE

2. 2.1 Scope of This Study and Report Considerable hydrogeologic and geochemical data were collected on the shallow strata at the WEC site during the Davis & Floyd ( 1980) study. However, this information was limited to depths Qf about 30 ft below land surface. Hydrogeologic data were not available on strata below the shallow geologic unit.
  • Two deeper environmental monitor wells were completed at the site in 1963 and 1969 (W-1) and two additional environmental monitor wells (Wells W-2, W-3) were installed in 1977. It was recommended that geophysical logs (gamma-ray and capiler) should provide useful hydrogeologic data on these four monitor wells that could be correlated with off-site data from previous studies made in southern Richland* . County.

After review of these geophysical data collected by S&ME, and other reports on or adjacent to the site, several test wells were recommended to properly assess the hydrogeologic properties of strata below the shallow geologic unit. Because of the availability of considerable hydrogeologic data on shallow strata and geophysical data on the deeper wells at the site, it was agreed to limit hydrogeologic testing of deeper strata to one test hole at a location believed to be the most strategic location.

An adjacent shallow well was to provide pertinent hydraulic data on shallow strata.

Hydrogeologic data from private and other water wells in the vicinity of the WEC property were obtained from well record files of state or federal agencies, well-drilling contractors, or other consultants (Sec. 2. 2. 3). Site maps, topographic elevations and elevations of previously constructed monitor wells at the site were available from the previous studies. Water-level measurements made by WEC pe.rson-nel or others and stra~igraphic boring logs of previously installed monitor wells were also made available.

2. 2. 2 Area of Investigation The scope of this project required two study areas: ( 1) the WEC plant site, in particular, the southern part of the property; and ( 2) an adjacent, or regional, study area. The plant site study area is the area defined by previous on-site studies (Fig. 2-2, Appendix). The regional study area (Fig. 2-3) was defined by the hydrogeologic data that could be obtained from published reports, data in state agency files, and our preliminary review of these reports and data.

SOIL & MATERIAL ENGINEERS INC, J

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  • PLANATION St'ructure contours on top of basement 00- rock in reference to MSL in feet.
..,3 Well location and number.

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'.-A* Location of ~eologic 30 29 e

0 u T Cl 1 2 3 c:::I --iii SCALE IN MILES SOURCE OF BASE MAP: County Road Map S.C. Dept. Highways and Public Transportation 1: 125. ODD 28 27 26

2. 2. 3 Investigation Methods f
  • Report and Data Review l Report and data review involved the review and analysis of both on-site and off-site data. The most comprehensive on-site re_port was the Davis & Floyd ( 1980) report, which included two reports prepared by LETCo ( 1980a, 1980b). Our approach in reviewing these reports was to utilize the basic data and derive independent conclusions regarding the hydrogeology of shallow strata on the site.

Basic data from these reports were utilized to construct hydrogeologic cross-sections in order to interpret the shallow subsurface stratigraphy of the site. Since completion of the Davis & Floyd Report, WEC personnel have periodically measured water levels and collected samples for water-quality analyis by Davis & Floyd. These data were made available for our review and interpretation.

Our review of off-site reports is summarized in Sec .. 2. 3. Basically, there are*

few published hydrogeologic reports available for southern Richland County.

Therefore, hydrogeologic data in the files of several state agencies and one federal agency were reviewed and .analyzed for any information that would aid in interpreting the hydrogeology of strata at the WEC site. These data consisted of well records in the files of the SCWRC (S. C. Water Resources Commission), the SCDHEC (S.C. Dept. Health and Environ~ental Control), the SCGS (S.C.

Geological Survey), and the USGS (U.S. Geological Survey-Water Resources Division).

These well records, normally supplied by well drillers, and consultants, consist of well-construction data, driller's log*s, information on yield of the well, and location. Sometimes geologic cuttings *(ditch samples) are collected and geophysical logs are made on certain wells. Our review indicated that information on water wells in southern Richland County and in the vicinity of the WEC site, in particular, is very general. Since much of the data in state and federal files has not been field checked or verified for accuracy, these data provide only a rough indication of ground-water conditions in the. regional study area.

In our review of these well records, we utilized the records, geophyical logs, driller's logs and other records which appeared to be the most complete.

SOIL & MATERIAL ENGINEERS INC.

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Some of the wells utilized in our regional hydrogeologic evaluation are shown on Fig. 2-3. Many of the well locations could not be verified with an accuracy of

+/- 0. 5 mile; therefore, these locations should be regarded as approximate. For this report and for future reference, the well location grid utilized by S&ME is shown on Fig. 2-3. This grid, based on 5-minute latitude-longitude rectangles, is utilized for numbering wells by both the SCWRC and SCDHEC. Some of these wells and various geologic cross-sections published by others are discussed in Sec. 3. O*

..,.... Geophysical Logging In order to derive some stratigraphic information on the deeper environmental wells installed at the site, caliper logs and natural gamma-ray logs were run by S&ME's geophysical logging department.

l The caliper log is obtained with an electronic caliper probe which measures borehole diameter as it moves upward through the *°borehole: In a cased hole, the caliper log is useful in accurately measuring the depth of casing, in determining casing integrity (casing breaks if they exist), and in locating the positions of well screens and probable screen ruptures. Because well-construction data were not available on the deeper monitor wells at the site, we ran the caliper logs to determine* the depth and integrity. of casing and well screens. It was not necessary to obtain caliper logs of the 28 shallow monitor wells (W-6 through W-33) because well-construction. data were available for these wells.

The natural gamma-ray log (frequently referred to as gamma log) is a log obtained with an electronic* gamma probe (or sonde). This log is one of the most useful logs for obtaining subsurface information from water wells and stratigraphic test holes. Basically, the gamma probe measures the natural gamma radioactivity emitted by strata in the borehole. The gamma probe, which contains no radioactive source, electronically "counts" or measures the !ntensity of gamma rays emitted by strata. Because the gamma probe is unaffected by well casing, a gamma log can be obtained from a cased well.

In sedimentary rocks, such as the sands and clays that underlie the WEC site, clays contain and emit a higher gamma count than sands. Therefore, clays which are generally confining beds, can be differentiated from sands which are generally SOIL 6 MATE II I AL ENGINEERS INC.

r r aquifers. The specific response (log signature) unit in a given area must be established.

of a ' stratum, bed, or lithologic Therefore, good stratigraphic logs in f representative wells at a given locality are absolutely necessary_ to establish the gamma response, or signature. The accuracy of stratigraphic correlations of strata I from well to well by gamma-log interpretion is strongly weakened if wells are spaced too far apart. A "reasonable well spacing" for a given area must be established. This reasonable spacing must be established on a thorough knowledge j

of the- subsurface geology.

Gamma logs were obtained from five wells (W-1,W-2,W-3,W-25, and W-27) and one abandoned water w_ell adjacent to the site. In several wells, two gamma logs were obtained, with different time counts, to establish the best log signature. Our interpretations and subsurface correlations with these logs are discussed in Sec.

4. O;. These interpretations were utilized to construct a hydrogeologic cross-section of ihe site, and in determining the proper depth to install a deep stratigraphic test hole (ST34).

Drilling and Stratigraphic Sampling As mentioned earlier, considerable geologic information on shallow strata (to a depth of about 30 ft below land surface) was available in the area south of the main plant building. However, the geology of deeper strata was largely unknown.

Our preliminary gamma-log correlations of the deeper strata (approximately 30-60 ft below land surface) in Wells W-1, W-2, and W-3 indicated the probable existence of clay confining beds below the Terrace unit, but information on their specific thickness, and physical and_ hydrogeologic character was limited. Therefore, stratigraphic (split-spoon) samples were obtained from the bottom of the deeper environmental monitor wells (W-2, W-3), and a stratigraphic test hole (ST34) was drilled to obtain samples of the Terrace unit and deeper strata.

Caliper logs of Wells W-1 and W-3 indicated that screens had not been placed in these wells, and thc1t strata below the casing in Well W-2 had collapsed and had

  • apparently filled the casing (indicating sand). Thus, Wells W-2 and W-3, at least, did- not contain bottom plugs, and split-spoon samples were obtained to determine the stratigraphy in the bottom of these wells.

SOIL & MATERIAL ENGINEERS INC.

r Stratigraphic Test ST34 and Well W-34 Our preliminary data review and geophysical logging indicated the probable existence of clay confining beds of the Black Mingo Formation underlying the Okefenokee Formation at the WEC site. The SCDHEC ( 1981) also inferred that a confining bed existed below the Okefenokee Formation in the vicinity of the WEC site.

Stratigraphic samples from ST34 were obtained by standard split-spoon sampling and mud-rotary drilling. Samples were obtained at 5-ft intervals and wash samples were observed between split-spoon intervals and described in the field by a hydro-I,.

geologist. A detailed geologist field log was maintained during the drilling. Split-I sp~on samples were placed in glass sample jars and transported to the laboratory fot detailed lithologic description by a hydrogeologist. The hole was terminated at a depth of 85 ft in the Black Min~Forii'lation. No aquifer *was present within the j,

Black Mingo Formation at the site; and this test hole was pluggea with cement r grout.

Well W-34 was extended by mud-rotary drilling to a depth of 24 ft. A two-inch diameter PVC continuous slot screen was installed at a depth of 18 ft-23 ft below land surface. Clean quartz gravel was installed in the annular space between the screen and borehole wall to a depth of 16 ft-24 ft. A bentonite seal, 2-ft thick, was installed above the gravel at a depth of 14 ft to 16 ft. The annular r*

,i space above the bentonite seal was then filled with neat cement grout to land I

surface. The well was developed with fresh tap water from a portable water tank.

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  • SOIL* MATIAIAL ENGINEl!AI INC.
2. 3 PREVIOUS STUDIES
2. 3. 1 On-Site Studies One of the major objectives of this study involved a comprehensive review and analysis of the Davis & Floyd (1980) and lETCo ( 1980a; 1980b) studies and r

t reports. In addition published geologic or hydrogeologic studies made in areas adja-I cent or in the vicinity of the site were to be reviewed and evaluated for ap-plicable data. A partial listing of the reports reviewed for this study are in-duded in Sec. 6. O. A number of other general or regional-type reports were reviewed for applicable data. The most important, however, are listed in Sec.

6. O. Many of these references are quot~d in later sections of this report. Thus, a detailed review and analysis of the specific contents of these reports are not reviewed in* detail here.

'I The 1980 Davis & Floyd and LETCo reports provide a fairly comprehensive I assessment of the hydrogeology of the Terrace Aquifer System in the a_rea between

l. the main plant and Sunset Lake. Most of the 28 monitor wells installed as a part I of their study were located in this area. The general hydrogeology of the Terrace Unit beneath other portions of the site was evaluated with other borings.

The basic data, hydrogeologic cross-sections of the shallow strata, ground-water movement and quality data provides the most comprehensive information of the hydrogeology of these shallow strata within 10-15 miles of the site.

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2. 3. 2 Regional Studies A number of regional or general-type reports contain information on the geology and hydrogeology of areas that include southern Richland County. Many of these reports contain little basic data that can be used with a reasonable de-gree of accuracy in interpreting the specific hy~rogeology of strata beneath or adjacent to the WEC site. The most pertinent of the references consulted, are summarized below. Getzen (1969) studied the subsurface and near-surface geology of the area between Wateree and Fort Jackson, with emphasis on the stratigraphy of the Tuscaloosa Formation. He also provided pertinent informa-tion on the water-bearing properties of Tuscaloosa aquifers. Padgett ( 1980) studied the near-surface and subsurface stratigraphy of the Black Mingo For-mation in the Wateree-Eastover area. Although this report was not specifically SOIL & MATERIAL ENGINEERS INC.

made to evaluate the hydrogeologic properties of the Black Mingo, his lithologic de*scriptions and geologic cross-sections provide pertinent data that can be used for hydrogeologic analysis.

Several published reports are available that describe the regional hydro-geology of southern Richland County or adjacent areas. The ground-water re-sources of the Wateree areas were described in a hydrogeologic report by Park

( 1980), published by the SCWRC. . When* combined with geophysical and drillers' logs obtained from wells in the study area, Park 1 s hydrogeologic descriptions provide pertinent data for analysis.

A report on the S.C. Recycling & Disposal (SCR&D) site, located adjacent to the WEC site, was prepared by hydrogeologists with the Ground-Water Protection Division of the SCDHEC ('1981). This report described the hydrogeology of the unconfined shallow aquifers beneath the site. A shallow-well monitoring network of 11 wells was constructed to monitor the movement of ground water and to evaluate the extent of ground-water contamination. The three deepest auger borings drilled by the SCDHEC provide the most pertinent stratigraphic information.

The specific hydi-ogeology of geologic formations beneath the shallow sediments was not addressed in the SCDHEC study. The deepest SCDHEC well (Well Q29-f1) was drilled into the top of Black Mingo Formation clays at 45-47 ft below land surface.

When the data from all of these reports are combined and interpreted, they provide an adequate description of the hydrogeology of the sedimentary strata in I

..l southern Richland County. The on-site reports are obviously the most pertinent and comprehensive. The reports by the SCDHEC ( 1980), Getzen ( 1969). Padgett

( 1980), and Park ( 1980) were the most useful of the regional reports.

SOIL & MATERIAL ENGINEERS INC.

3. O REGIONAL GEOLOGY AND HYDROLOGY The occurrence, movement, and availability of ground water in any area are intimately related to the stratigraphy and structure of underlying geologic forma-tions. Similarly, the near-surface geology largely controls the physiography of an area. The relationship of the geology, physiography and climate of an area ultimately controls the recharge of ground water to geologic formations beneath that area.

The term "regional" can be used to refer to any scale--from a few square miles to many hundreds of square miles. 'In this report, 11 regional 11 refers to the area shown in Fig. 2-3, southeastern Richland County. This area lies within the following USGS 7. 5 minute topographic guadrangles: Fort Jackson South, Saylors Lake, Congaree, Gadsden, Eastover, and Wateree. The purpose of this i

settion is to briefly summarize those 11 regional 11 relationships that are important in understanding the occurrence and movement of ground water beneath and adjacent to the WEC site. In Sec. 4.0 the site-specific hydrogeology is presented in greater detail.

3.1 PHYSIOGRAPHY--STRATIGRAPHY--CLIMATE

.3. 1. 1 Physiography and Climate Southeastern Richland County lies within the upper Coastal Plain subprovince of the Atlantic Coastal Plain. The topography of this area varies from very flat terrain with poor drainage near the Congaree River to well dissected, mature terrane in the Ft. Jackson South quadrangle.

The physiography of the upper Coastal Plain is controlled by the unconsol-idated sands and clays of the Coastal Plain which are easily weathered in comparison to the hard, consolidated crystalline rocks north of Columbia, S. C. Columbia is located on the Fall Line which separates the Piedmont physiographic province to the northwest from the Coastal Plain province to the southeast.

The climate of southeastern Richland County has a pronounced effect on the availability of water available as recharge to the underlying geologic formations.

Precipitation, which is mainly in the form of rain is fairly well distributed through-out the year. The average annual rainfall is about 50 inches, with spring and early summer being the wettest seasons. Droughts, which may be severe to SOIL lo MATERIAL ENGINEERS INC:.

agricultural production, are normally described- as.. mild and sometimes occur in late summer and early fall. Some farmers in southeastern Richland County and in adjacent counties have turned to irrigation to avoid crop failures during these droughts. Although ponds and streams are used where sufficient, many crops are being increasingly irrigated by ground water.

The topography of the area surrounding the WEC plant is flat with only slight local relief. Several ancient marine "terraces" occur in the vicinity of the plant.

These terraces have been mapped over large areas by their topographic elevations,

-- which may vary only a few tens of feet over large areas. The WEC plant is located on the Okefenokee terrace, which has a range in elevation of about 130 ft MSL to 150 MSL near Columbia (Colquhoun, 1965). Southeast of the plant site, the Wicomico terrace has an elevation of 100 to 120 ft MSL. The Sunderland terrace occurs northwest of the WEC site, with elevations ranging from 170 to 190 ft MSL.

3.1. 2 Geologic Setting--Stratigraphy and Structure Sedimentary rocks (sediments), primarily sands and clays, underlie the upper Coastal Plain in Richland County. Outcrops are rare, and only a few feet or tens of feet of these sediments are exposed in a given area. Therefore, most of the knowledge on the geology of these sediments must come from interpretation of sub-surface information obtained from stratigraphic test wells or water wells. Some of the water wells used in our regional geologic and hydrogeologic analysis are shown in Fig. 2-3, and the available data on these wells are summarized in Appendix Table 3-1.

These sediments in Richland County thicken from a few tens of feet at Columbia at the Fall Line to approximately 700 ft 'near the Wateree River in south-ernmost Richland County. These sedimentary rocks, ranging from Late Creta-ceous to Recent in age, overlie pre-Cre_taceous crystalline "bedrock" or "basement".

The upper surface of the basement dips toward the southeast at a rate of about 20-40 ft/mi (Fig. 2-3). The overlying sedimentary formations also dip toward the southeast and thicken in the direction of dip. Because of this southeastward dip, wells penetrate a certain geologic unit (bed or stratum) at progressively greater depths toward the southeast.

Several water wells in southeastern Richland County (Fig. 2-3) have pene-trated the entire thickness of sedimentary rocks, terminating at or near the top SOIL & MATERIAL ENGINEERS INC.

of basement. Well 27Q-5 penetrated the top of -basement at a depth of 540 ft:

Further southeast, Wells 26Q-3 (658 ft) and 26R-1 (680 ft) were terminated at the top of crystalline bedrock. Many water wells located 10-15 mi northwest of the WEC site near Columbia and in the western part of Ft. Jackson have pene-trated crystalline bedrock. Unfortunately, within several miles of the WEC site, we have not found any records of water wells that have been drilled to bedrock:

thus, the geologic structure map (Fig. 2-3) must be regarded as a generalized representation of the dip of the bedrock surface.

The generalized geologic cross-section of southeastern Richland County (Fig.

3-1) shows our interpretation of the subsurface stratigraphy. This cross-section is perpendicular to the geologic structure contours in Fig. 2-3; thus, the cross-sec}ion should approximately represent the true dip of the geologic formations.

A similar geologic cross-section was prepared by Getzen ( 1969), based on information obtained from Wells 28P-1, 27Q-s, and 26R-2; and more recently, Padgett ( 1980) constructed a geologic cross-section from information obtained from Wells 26Q-3, and 26R-1. Park C1980) used Well 26Q-2 in his hydrogeologic cross-section of Sumter County. Although there are some differences in the geologic interpre-tations of these investigators, the subsurface geology of southeasternmost Richland County near the Wateree River has been fairly well established.

Bec~use the sedimentary rocks thicken to more than 600 ft toward the south-east, it should be expected that some strata (or lithologic units) present in south-easternmost Richland County will not be present at the WEC site. At the WEC site, the crystalline bedrock occurs at an elevation of about -100 to -150 ft MSL (ft below mean sea level). Therefore, with topographic elevations of 110-140 ft MSL, the sedimentary rocks at the WEC site should be about 240 ft to 290 ft thick, depending on land-surface elevation at a particular point (Fig. 3-1).

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3. 1. 3 Summary of Geologic Formations The correlation of subsurface geologic formations (stratigraphic correlation) from well to well in a given area depends on the accuracy of information available and distance between wells. Although exposures of geologic formations are rare and the number of deep water wells in southern Richland County penetrating below Coastal Plain sedimentary rocks are widely spaced, the subsurface geology of these formations are fairly well known on a regional basis.

As stated previously in this report, several published reports or M. S.

theses describe the subsurface geology of southern Richland County or adjacent counties. Getzen ( 1969) described the stratigraphy of the Upper Cretaceous Tuscaloosa Formation in southea*stern Richland County. Smith ( 1979) and Padgett

( 1~80) studied the stratigraphy of Tertiary age sediments in Lexington and Rich-land Counties. The near-surface geology of the- upper Tertiary and Pleistocene terrace sediments was described by Colquhoun ( 1965)

  • The following descriptions of geologic formations are based, in part, on these and other published references, supplemented with water-well information from various well-record files.

Basement Rocks The geology of basement rocks in southern Richland County is poorly known because few wells have been drilled into these rocks. Compared to overlying formations, these rocks are essentially considered as "impermeable" or relatively impermeable. Therefore, these rocks are relatively unimportant to the overall geology and water-bearing properties of overlying sediments.

Tuscaloosa Formation The Tuscaloosa Formation overlies bedrock and is the oldest sedimentary formation in southern Richland County. _ The Tuscaloosa was deposited on the eroded surface of bedrock during Late Cretaceous time. Although the lithology of the Tuscaloosa varies considerably in local areas, it has certain characteristics which are recognizable over large geographic areas.

In southern Richland County the Tuscaloosa Formation has been penetrated or tapped by many water wells; some of these wells are plotted on Fig. 2-3.

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In general, the Tuscaloosa is a somewhat complex assortment of lithologies. It contains vari -colored (generally "light-colored") fine-to coarse-grained quartzose, feldspathic (containing feldspar) sands; and light-colored (grey, red, brown, purple, yellow) clays containing variable amounts of silt or sand. Fine-to-medium-grained gravel, and mica and lignitic wood framents are common constituents in this formation.

The Tuscaloosa Formation thins from about 300-350 ft in southeastern Rich-land County to less than 100 ft near Columbia (Fig. 3-1). Getzen (1969) sub-divided the Tuscaloosa into 10 lithologic units (beds) in southeastern Richland County, which he designated by the letters "a" through "j". The upper part of what Getzen termed Tuscaloosa has been shown by several more recent studies (Smith, 1969; Padgett, 1980) to be the Black Mingo Formation.

In the middle and lower Coastal Plain and near the Wateree River in Richland County, the Black Creek Formation probably overlies the ruscaloosa Formation.

However, at and in the immediate vicinity of the WEC site, the Black Creek Formation is believed to be absent, and the Black Mingo Formation overlies the Tuscaloosa Formation (SCDHEC, 1981).

Black Mingo Formation i:*i The Black Mingo Formation is the oldest Tertiary age geologic formation in southern Richland County. The subsurface geology (stratigraphy) of this unit

!., has been studied by a number of investigators, especially in the last five years.

  • *, Padgett ( 1980) studied the near surface and subsurface stratigraphy of this I formation in southern Richland County and adjacent areas and reviewed previous I

I. reports that describe the geology of this formation.

Padgett ( 1980) showed that the Black Mingo Formation in Godspeed Farm Well fI No. 1 (Well 26R-1, Fig. 2-3) is approximately 100 ft thick and consists of ( 1) an upper deltaic unit and ( 2) a lower transgressive marine clay with a basal sand. He showed that the Black Mingo Formation thickened toward the south-east and is approximately 200 ft thick at Pinewood in Sumter County. Toward the northwest, in the Congaree River Valley, the upper part of the Black Mingo Formation has been removed by erosion. Therefore, in the immediate vicinity of the WEC site, the thickness of the Black Mingo Formation has been estimated to be only about 75 ft (SCDHEC, 1981).

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As illustrated in Fig. 3-1, if the 75 ft thick -estimate for the Black Mingo is correct and if it thins toward the northwest, it eventually pinches out between the WEC site and Well 30P-2. The base of the Black Mingo Formation in Fig. 3-1 was drawn with a southeastward dip of 10-15 ft/mi, a rate consistent with published values. However, many geologists have recognized the fact that the contact between the Black Mingo and underlying Tuscaloosa is problematic (Siple, 1959; Colquhoun, et al, 1969). This is _because the lithologic similarity of the Black Mingo and underlying Cretaceous age formations (either Black Creek or.

Tuscaloosa) make the contact difficult to define in the subsurface, particularly with cuttings from rotary-drilled wells. Therefore, in the absence of specific subsurface information from wells in the vicinity of the WEC site, the thicknes_s and stratigraphic relationships of the Black Mingo can not be accurately defined. The mo~t complete stratigraphic data on the Black Mingo are from interpretation and co~relation with gamma logs on WEC monitoring wells (W-1, W-2, and W-3) and from split-spoon samples in test well ST~4. The upper part of the Black Mingo Formation at the WEC site is a dark - to medium-gray carbonaceous (lignitic) clay and shale which is as much as 60 ft thick (Wells W-3,ST3ll).

As shown by Padgett ( 1980) the Black Mingo Formation in southern Richland County is a complex and variable assortment of lithologies (rock t~pes) deposited in marginal marine to deltaic environments. In these depositional environments, fine-grained sediments such as clays and silts dominate, with lenses (bP.ds) of

  • coarser-grained sand being locally present. Although the Black Mingo contains a wide range of grain sizes, it is typically known for the clays and shales which are dominant. These clays are typically dark-grey to brown, micaceous, highly plastic, and carbonaceous. They have been traced laterally for many miles frorri water-well records and outcrop data. Beds of light to medium-grey opaline claystone, with a smooth conchoidal fracture are common in the upper part of this formation. In Sumter County and adjacent area_s, these beds were named the Tavern Creek bed by Padgett ( 1980).

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Pliocene- Pleistocene Formations In southern Richland County, sand and clay beds are exposed in scattered drainage ditches and road cuts. These sediments are generally on the order of 20 ft to 40 ft thick and are often referred to as Plio-Pleistocene sediments in reference to their late Tertiary (Pliocene) to Pleistocene ages. During late Tertiary to Pleistocene time, a series of marine terraces were formed, which have been named by geologists. In the immediate vicinity of the WEC site, the Okefenokee terrace has an elevation of 130 ft to 150 ft MSL. Some geologists have assigned formal geologic names to the sediments underlying these terraces. Thus, the Okefenokee Formation underlies the Okefenokee terrace.

These Plio-Pleistocene sediments contain various admixtures of silts, clays, and sands in beds which thicken or thin appreciably* within short distances.

The lithology of one bed (sand, for example) commonly grades laterally or verti-cally into another lithology(sandy clay,* for example}. Thus, even within a site-specific area of only a few hundreds of square feet, it is not unusual to find that the subsurface geology of these sediments is often difficult to correlate from one well to another.

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3.2 REGIONAL HYDROLOGY One of the objectives of this study was to evaluate the potential movement of ground water from the shallow geologic formation into deeper geologic formations beneath the WEC site. In accomplishing this objective, one of the work tasks was to review and evaluate existing subsurface information at the site and to corre-late this information to subsurface information on geologic formations adjacent to or in the vicinity of the site. Because the subsurface geology of southern Richland County has not been mapped in detail by either geologists or hydrogeologists, some confusion exists,* especially between geologists and hydrogeologists, concern-ing the nomenclature applied to various geologic "formations" in this area. There-fore, a brief explanation is necessary on the nomenclature applied to various hydro-geologic units in this report.

3. 2. 1 Ground-Water Occurrence The occurrence, movement, and availability of ground_ water in southern Richland County are related to the stratigraphy (type of sediments) and structure (primarily the attitude) of underlying strata. A geologic formation, as formally defined by a geologist, is a recognizable stratum or several strata of similar litho-logic character that is mappable or "traceable" within a certain geographic area.

Some geologic formations, such as the Tuscaloosa Formation, contain a number of lithologic units such as clays, sands, clayey sand and gravel beds.

A hydrogeologic unit is a stratum, or several strata, that have similar water-bearing (hydrologic) properties. An aquifer is a hydrogeologic unit that transmits ground water or yields appreciable quantities of ground water to wells. Aquifers in -southern Richland County are generally sands, clayey sands, or gravelly sands and these occur within all of the geologic formations in the area. One aquifer may be composed of relatively "clean 11 or well sorted medium to coarse sand and may yield appreciable quantities of ground water to wells. The same aquifer may contain appreciable quantities of clay or silt in another area, and would not be as permeable; and consequently would not yield as much ground water.

A confining bed is a hydrogeologic unit that is less permeable and does not*

readily transmit ground water or yield appreciable quantities of ground water to wells. Some confining beds are relatively impermeable, and others may be suffi-ciently permeable to allow some movement of ground water through them; but they SOIL & MATERIAL ENGINEERS INC

-I

would not yield appreciable quantities of g*round. ~ater to water wells or even monitor wells~ In southern Richland County, c~nfining beds occur within all of the major geologic formations and are generally composed of relatively pure clay, silty clays, or clayey silts. Some clay beds within the Black Mingo Formation are especially known for their relatively impermeable nature.

In most of the study area (Fig. 2-3) the subsurface boundaries of either the major geologic formations or major hydrogeologic units have not been precisely mapped* by geologists or hydrogeologists except on a generalized basis. The vertical boundaries of a geologic formation may not actually coincide with the boundaries of a hydrogeologic unit. For example, at some places in the study area a sand occurs in the base of the Black Mingo Formation that is similar to a sand bed in the upper part of the underlying Tuscaloosa Form!E:ltion. Therefore, these sands, although in two different geologic formations, would be considered as !one hydrogeologic unit--an aquifer

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Confined and Unconfined Aquifers Ground water in southern Richland County occurs under both artesian (confined) and water-table [unconfined) conditions. Artesian aquifers are aquifers that are confined, or contained, by confining beds. The water level in a well tapping an artesian aquifer will rise above the top of the aquifer; this water level represents a point on the piezometric surface, an imaginary "pressure" surfac_e connecting points to which water will rise in tightly cased wells completed in the same aquifer. The water level in a well tapping a water-table aquifer defines the water table, the imaginary surface at which pressure is atmospheric.

Water levels in wells penetrating a water-table aquifer may rise to a level at, above, or below the water table, depending on the well depth and whether the well is in a recharge or discharge area (Lohman, 1972).

In southern Richland County (Fig. 2-3) artesian aquifers occur within the Tuscaloosa and Black Mingo Formations. Ground water in the near-surface geo-logic formations gnerally occurs under water-table conditions. The artesian aquifers are recharged from two sources ( 1) rain falling in the outcrop areas located at higher elevations, and (2) vertical leakage through relatively permeable confining beds. The recharge areas for artesian aquifers within the Tuscaloosa Formation are located north of the WEC site in the Columbia-Ft. Jackson area.

Because these areas are located at altitudes higher than those in southeastern Richland County, considerable artesian pressure is built up as ground water moves down the hydraulic gradient. The Black Mingo Formation does not contain such an extensive outcrop area. Therefore, recharge to artesian Black Mingo aquifers must occur from downward vertical leakage from shallow water-table aquifers or from upward vertical leakage from artesian Tuscaloosa Formation aquifers.

Recharge of water-table aquifers in southern Richland County occurs pri-marily from rainfall and infiltration in the immediate area, and the water table generally reflects subtle differences in topography. Topographically high areas are generally recharge areas, and lower areas are discharge areas

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3. 2. 2 Major Aquifer Systems and Ground-Water Use Information compiled during this study indicates that three major aquifer systems occur in southern Richland County: ( 1) t~e Tuscaloosa Aquifer System, (2) the Black Mingo A~uifer System and (3) a surficial, or unconfined aquifer system. The Tuscaloosa Aquifer System, for practical purposes, is con-sidered equivalent to the Tuscaloosa Formation, and the Black Mingo Aquifer System i~ considered equivalent to the Black Mingo Formation. Various shallow geologic formations are included within the unconfined aquifer system and this series of sands and clays have not been named on a regional basis.

Tuscaloosa Aquifer System This series of sands and clays make up one of the most important artesian aquifer systems in the upper Coastal Plain. Clays occur within the Tt*scaloosa

\

anti separate this aquifer system into a. . number of aquifers. ~

This aquifer system underlies all of southern Richland County and artesian aquifers within this system supply ground water to many wells in this area. There are a number of beds within the Tuscaloosa aquifer system that are composed of medium-to coarse-grained sand and fine-to-medium gravel. These sand beds, which are as much as 20 ft to 40 ft thick, are prolific artesian aquifers.

The piezometric surface of this multiple-aquifer system, which may consist of several piezometric surfaces, has not been mapped in southern Richland County. Consequently, the direction of ground-water movement within this arte-sian aquifer system can only be inferred. Presumably, rainfall infiltrates 'the ourcrop areas at high elevations ( +300 - +400 ft MSL) near Columbia and moves down the hydraulic gradient toward the south and southeast. About 15-20 mi down the dip in southern Richland County, major river valleys would be natural discharge areas for ground water moving through this aquifer system. Thus, the.

WEC site is presumably located in a ground-water discharge area of the Tuscaloosa.

As shown in Fig~ 3-1, several wells at and in the vicinity of the WEC site tap artesian sand aquifers within the Tuscaloosa (Wells 30P-2, 30Q-2, 30Q-3). Well 30P-2, an abandoned test well at Atlas Road School, was reportedly terminated in "clay" at 115 ft. However, well 30Q-2 reportedly tapped a "porous sand" at 200 ft, which is interpreted to be a Tuscaloosa artesian aquifer.

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Some wells in the Hopkins area (Grid 29Q, Fig. 2..:..3) and many small-diameter domestic wells northeast of the WEC site (Grid 29P) tap artesian sand aquifers within the Tuscaloosa Aquifer System. Most of these wells supply private homes (domestic wells) and small businesses, industries, trailer parks, and schools.

Our review of well records indicates that there are no large-capacity Tuscaloosa wells located within about five miles of the WEC site. To the southeast, where Tuscaloosa aquifers thicken and are mor~ permeable, several large-capacity irrigation wells (26R-1,27Q-1) tap this aquifer system.

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,I

Black Mingo Aquifer System Specific hydrogeologic units within the Black Mingo Formation have not yet been mapped in this area (Camille Ransom, S. C. Water Resources Commission, personal communic., 1981) Therefore, the Black Mingo 11 Formation 11 rather than "aquifer system ", is most often used by hydrogeologists in describing the hydrologic properties of this unit. A review of available water-well records at the SCWRC and USGS indicates that many water wells in the area between Hopkins and Eastover (Fig. 2-3) probably tap sand aquifers within the Black Mingo Formation. However, drillers' and geophysical logs and other specific well-construction data are rather fragmentea. Some of the available well records for the study area are summarized in Appendix Table 3-1, and the wells are plotted on Fig. 2-3.

Several public-supply wells at Eastover (27Q-2, 27Q-3) and two wells at the EcEntire NG Air Base ( 2~Q-1, 28Q-2) tap Black Mingo aquifers at depths of less than 200 ft. Specific pumping-test data on Black Mingo wells in the study area are not available, but some reported specific capacities of wells are in the range of less than 4 gpm/ft to about 10 gpm/ft. Local well drillers report that there is a considerable variation in hydrologic *properties of aquifers within this aquifer system (Mr. P. McNeil, Heater Well Co., personal communic., 1981). This erratic hydrologic behavior is, in part, related to the depositional environment of Black Mingo strata. Sands commonly thin or grade laterally into sandy silts or even silty clays within relatively short distances. Thus, it is not unusual for relatively poor yielding wells to be located in fairly close proximity to higher yielding wells.

In the immediate vicinity of the WEC site (Fig. 3-1) wells deeper than about 125 ft would penetrate the Tuscaloosa Formation. Well 30Q-3 (WEC Well W-1),

reportedly drilled to a depth of 140 ft probably encountere~ Tuscaloosa sediments.

Currently, the open-hole section of this well ( 71-76 ft) is within the Black Mingo Formation. Well 30Q-2 reportedly penetrated "black mud and water" from land surface to 20 ft; impermeable clays from 20-200 ft; and a porous sand at 200 ft.

While these reported data are admittedly poor, they do fit the stratigraphic sequence as illustrated in Fig. 3-1.

Ground water in Black Mingo aquifers occurs under artesian conditions where these aquifers are confined between clays. Near outcrop areas, ground water in shallow Black Mingo aquifers may occur under "semi-confined" or water-table SOIL & MATERIAL ENGINEERS INC.

conditions. Therefore, Black Mingo aquifers i_') southeastern Richland County receive recharge both from outcrop areas and from vertical leakage.

Many private and a number of public-supply wells have been drilled in the Hopkins area (Grid 29Q, Fig. 2-3) which tap or that have been drilled through the Black Mingo. In this area, we have not found readily available well records, geophysical and drillers' logs that could aid in tracing the subsurface distribution of aquifers and confining beds within the Black _Mingo Formation.

The following conclusions concerning the Black Mingo Aquifer System in southeastern Richland County are based on ':the regional analysis of available data and orFsite s*tudies (discussed in Sec. 4. O).

1. In the immediate vicinity of the WEC site (within about five miles) ground water in lower Black Mingo aquifers occurs under artesian conditions because of clay confining beds in the upper part of this aquifer system (Fig. 3-1).
2. Strata within the Black Mingo are not known to outcrop within five miles of the WEC site. Thus, Black Mingo aquifers have 11 relatively 11 limited access to direct rehcarge.
3. Artesian Black Mingo aquifers in the vicinity of the WEC site should have relatively low artesian pressure, or head.
4. These Black Mingo aquifers should have "relatively poor" hydraulic properties relative to the more prolific artesian aquifers in the upper Coastal Plain, such as those in the Tuscaloosa Aquifer System.
s. Because artesian Tuscaloosa aquifers are recharged at higher elevations near Columbia, they should have higher artesian pressures than Black Mingo aquifers; thus,
6. Lower Black Mingo aquifers would be expected to receive consider-able recharge by vertical upward leakage from higher head Tuscaloosa aquifers.
7. Extremely large ground-water withdrawals from Black Mingo aquifers in the vicinity of the WEC site are unlikely if a potential ground water user needed "large" quantities of ground water; that is, quantities SOIL & MATERIAL ENGINEERS INC

in excess of several to as much as 1O mgd (mil_!ion gallons per day); if this quan-tity of ground water were needed, ground-water users would likely drill wells in-to more prolific Tuscaloosa aquifers. A properly designed and constructed Black Mingo well field with a number of large-diameter wells might supply as much as several million gallons per day of ground water. However, because Black Mingo aquifers in the vicinity of the site are relatively thin, less than about 20 ft thick, it is unlikely that a large-capacity well field could be supplied by Black Mingo aquifers.

V.

8. Published data are not available that accurately defines the contact or stratigraphic relationship between the Black Mingo and Tuscaloosa Formations.
, The separation of the Black Mingo and Tuscaloosa Formations near the site (Fig. 3-1) is based on reported data and should be considered as a generalized representation. In terms of downward vertical ground-water movement and pot-ential contaminant movement at the WEC site, an accurate definition of this is not considered to be of critical importance for the purposes of this study.

Unconfined Aquifer System The Plio-Pleistocene sediments in southern Richland County contain shallow sand aquifers, which are often not confined by overlying clays. Thus, ground water in these shallow aquifers generally occurs under unconfined (water-table) conditions. Actually the hydrogeology of these shallow aquifers is poorly known in southern Richland County, except in some site-specific localities. Most of the data on this aquifer system have been collected during site-specific studies, such as the study of the SCR&D site made by the SCDHEC (1981), and the com-prehensive hydrogeologic study of thee WEC site made by Davis & Floyd (1980) and LET Co ( 1980a; 1980b).

Records are available on approximately 25-50 shallow wells in the regional study area at the SCWRC and USGS. These records indicate that the unconfined aquifer system supplies ground water to many small-diameter ( 2-inch, 4-inch) domestic wells in southern Richland County. These wells are typically 25-50 ft deep, and are equipped with shallow jet pumps that yield several gallons of water per minute, a yield sufficient to supply the drinking-water needs of an average family. These well records indicate that some of the shallow wells in the general vicinity of the WEC site often contain objectional amounts of iron.

4. 0 HYDROGEOLOGY OF THE S*ITE 4.1 GROUND-WATER OCCURRENCE AND HYDROGEOLOGIC UNITS
  • 11. 1. 1 General Overview -

Three major aquifer systems underlie the WEC site: the Terrace Aquifer System, the Black Mingo Aquifer System, and the Tuscaloosa Aquifer System.

These three major aquifer systems can be further differentiated into four local hydrogeologic units at the WEC site (Fig. 4-1) with data currently available, as follows:

Unit I, the uppermost unit, is referred to as the Terrace Unit. This unit is regarded as a single hydrogeologic unit, even though the lithology and hydrologic properties vary considerably .

Unit II, the upper part of the Black Mingo Formation (or Aquifer System) consists primarily of clay and shale beds that function as a con-fining unit which restricts downward vertical ground-water flow.

Unit 111, an artesian aquifer within the Black Mingo Aquifer System, consists of sand, and is tapped by several environmental monitor wells at the site.

Unit IV, the Tuscaloosa* Formation (Aquifer System), has been pene-trated by one monitor well at the site.

Crystalline 11 basement" rocks underlie the Tuscaloosa Formation at the site, and cot.1ld be considered at a fifth hydrogeologic unit, but the hydrogeologic proper-ties of these rocks are considered as relatively unimportant to the hydrogeology of overlying sediments.

Within the main area of interest for this study, the immediate area of the WEC plant and south to Sunset Lake, a knowledge of the hydrogeologic properties of crystalline basement rocks and overlying units_ IV and 111 are not as impor-tant as the hydrogeologic properties of the Terrace Unit (Unit I) and the upper part of the Black Mingo Formation (Unit 11). Therefore, the hydrogeology of Units I and 11 are described in greater detail in this report.

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4. 1. 2 Terrace Aquifer System (Unit I)

Available Data, Occurrence and Distribution Considerable information is available on the thickness, lithology, and lateral distribution of Unit I at and in the immediate vicinity of the site. As part of the Davis & Floyd ( 1980) study, LET Co ( 1980a; 1980b) installed 28 monitor wells that tap this unit, and they constructed geologic cross-sections of the site from the boring logs. Most of these monitor *wells are located in the area between the main plant building and Sunset Lake (Fig. 2-2, Appendix), providing good strati-graphic coverage of the Terrace Unit in this part of the WEC property. The re-maining wells were installed at various locations surrounding the main* plant, pri-marily to provide additional stratigraphic information on the shallow strata.

Interpretations of these boring logs indicate that the Terrace Unit likely un-de)'"lies the entire WEC property and areas adjacent to the property. Additional stratigraphic information on Unit I is provided by the geophysical logs of monitor wells W-1, W-2, and W-3, stratigraphic samples from test hole TH 34., and moni-tor Well W-34.

Hydrogeologic cross-sections of the Terrace Unit (Figs. 4-2, 4-3) were con-structed from boring logs prepared by LETCo ( 1980a, 1980b), boring log from test hole TH 34, geophysical data, and observation of the upper 15-20 ft of the terrace sediments exposed in the escarpment north of the pond. The locations of these cross-sections are shown in Fig. 2-2 (Appendix). The position of the base of this aquifer system (Figs. 4-2, 4-4) is based on interpretation of gamma logs obtained from the deeper monitor wells and the geologist log of test hole Tl-134. As shown in Figs. 4-1 and 4-4, there is a pronounced gamma log signa-ture at the contact between the sandy basal Terrace Unit and the top of the un-derlying Black Mingo Formation (Unit I I). Therefore, the contact between Units I and 11 can be determined fairly accurately from gamma-log interpretation.

As shown in Fig.4-1, the ba~al surface of'the Terrace Unit slopes gently in a south-southwest direction toward the Congaree River. The Terrace Unit is equivalent to the Okefenokee Formation which is a poorly sorted mixture of sands, clays, silts and gravel.

Thickness and Lithology The Terrace Hydrogeologic Unit is considered to extend from land surface SOIL & MATERIAL ENGINEERS INC.

to the top of the underlying Black Mingo Form~tion f Aquifer System) (Fig. 4-1) .

Therefore, the thickness of this unit varies with topography across the WEC pro-perty. The thickness varies from about 20 ft at Well W- 2 to about 40 ft beneath the storage area south of the main* plant, and is *about 25 ft thick beneath the area surrounding the pond and Sunset Lake.

As shown in Figs. 4-2, 4-3, and 4-4, the _Terrace Unit is composed of a rather compl_ex assortment of clays, silt~, clayey silty sands or sandy silts, and sandy gravelly silts. The correlation of individual strata (lithologic units) in Figs. 4-2 and 4-3 is difficult, even between wells located only 150 ft apart. In general, strata within this unit become coarser with depth, and the basal part of this unit below the water table consists of gravelly, sandy silts which are locally clayey.

Water-Bearing Properties f

Interpretation of the considerable number of wells tapping or drilled through the Terrace Unit indicates that there are no continuous clays between the water table and land surface (Figs. 4-2, 4-3). Therefore, ground water within the Terrace Unit occurs under water-table (unconfined) conditions. In general, the water table within the Terrace Unit is a subdued replica of the topography and is at atmospheric pressure. Thus, the recharge to and discharge from aquifers within this unit, under natural hydraulic gradients, Is controlled, in part, by the topography of the immediate area. The hydraulic gradient of the water table in Unit I is very low and depends on topography, location of recharge and discharge areas, type and amount and duration and intensity of precipitation (which is the source of recharge), and hydraulic properties of the aquifer. The small spring located on the north side of the pond is a point discharge area for ground water moving through this unit (Fig. 4-4). Presumably, other small seepage springs are present along the pond and along the north side of Sunset Lake which would serve as natural discharge areas for the Terra~e Unit (Fig.4-3).

Typically, the fluctuation of the water table in an unconfined aquifer is greater In recharge areas, and less in discharge areas; The range of the annual fluctuation of the water table in the Terrace Unit is estimated to be about 1 O ft.

Fluctuations may be slightly greater in the area of the main plant and less near the pond and Sunset Lake, which are natural discharge areas.

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The water-bearing properties of the Terrace__ Unit have been determined on the basis of the installed monitor wells and hydraulic conductivity data on selected wells. These properties are summarized in the cross-sections of the site (Appendix). Interpretation of boring logs of monitor wells indicates that the gravelly, sandy, silt unit in the bottom of the Terrace Unit appears to be the most permeable. As shown in Fig. 4-3, strata within the screens opposite this unit have fairly low hydraulic conductivities ( 0~ 02 ft/day to O. 34 ft/day) which are typical values for a poorly sorted silt. In some areas, this unit would be considered more of a confining bed than an aquifer

  • The water-bearing properties of the Terrace Unit in the area between the plant and Sunset Lake can be summarized as follows:
1. The coarser-grained strata in the basal part of the Terrace Unit are probably the most permeable, and these basal strata, composed pri-marily of gravelly, poorly sorted, sandy silt or silty fine sands, should-dominate the lateral flow of ground water within this unit.
2. Although the Terrace Unit is lithologically complex, it could be considered reasonably uniform in terms of its water-bearing properties in the area between the main plant and Sunset Lake.
3. Because of the relatively poor sorting of strata within this unit, the water-bearing properties are expected to vary considerably over an area of hundreds or thousands of square feet. Therefore, minor incon-sistencies in measured water levels or water-quality analyses should be expected.
4. The small spring indicates that some preferential flow occurs within the Terrace Unit, and may indicate that lenses of coarser-grained strata probably exist, such as small ancient channel sands.

4.1. 3 Black Mingo Aquifer System Available Data, Occurrence and Distribution The Black Mingo Formation is interpreted to underlie the entire WEC site, and the full thickness of this formation was penetrated in Well W-1, reportedly drilled to an original depth of 140 ft (Fig.4-1). Gray clay was reportedly pene-tr"::lted from approximately 30 ft to 71 ft below ground surface, and packed sand from 71-140 ft. The caliper log indicates that the borehole in the interval 71-76 ft SOIL II, MATERIAL ENGINEERS INC.

is open within the Black Mingo Formation *(Fig.__4-1). , As much as 60 ft of the Black Mingo Formation was penetrated in Well W-3, and Well W-2 penetrated the upper 35 ft of this formation. Reported information is available on Well 30Q-6, a well drilled in the general vicinity of the main plant in 1963 to a depth of approximately 1 OS ft. Gray clay occurred below the Terrace Unit (approximately 30 ft) to 105 ft below ground surface: The clay was reportedly cased off to a depth of 105 ft and the well produced 107 gpm *with a drawdown of 15 ft.

  • The most complete lithologic data on the Black Mingo Formation was obtained ti from test hole TH34. The lithologic; log of this well (Appendix Table 4-3) indi-cates that the upper part of the Black Mingo Formation consists of 58 ft of light-to medium-gray to dark-gray clays and shale in the interval from 27-85 ft below land surface (Fig. 4-1). The lithology and color of these clays and the shale ar~ indicative of the marine to marginal marine environment in which the Black Mihgo Formation in southern Richland* County was deposited. The dark-gray shale with a conchoidal fracture in the interval from 49-57 ft is characteristic of the Black Mingo Formation.

A split-spoon sample of the Black Mingo obtained from 61-62. 5 ft in Well W-2 consists of saturated, fine- to coarse-grained quartzose sand which is poorly sorted. This sand is interpreted to be within Unit 111, an artesian aquifer within the Black Mingo Formation (see Fig.4-1). The split-spoon sample obtained from 78-79. 5 ft in Well W-3 is composed of gray, plastic clay within Unit II.

In summary, the borehole data available on the Black Mingo Formation at the WEC site provide rather conclusive evidence that the Black Mingo Formation beneath the WEC site consfsts of two hydrogeologic units that differ markedly in their hydrologic properties. The hydrologic characteristics of these two units are summarized in the following sections. The hydraulic properties of these two units are summarized in Sec. 4. 2 and the question* of vertical leakage is considered in greater detail.

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Hydrogeologic Unit 11 The thickness of Unit II ranges from about 35 ft to as much as 60 ft in the central plant site area (Fig. 4-1). In test hole W-34, Unit II consists of 58 ft of light- to medium-gray, carbonaceous , micaceous clays and dark-gray, carbona-ceous brittle shale with a massive, conchoidal fracture. Except for some thin laminae, no horizontal stratification was noted in the samples; and except for some moisture in the upper 3 ft of this ~nit, the remainder of the unit to the 85-ft depth was dry. These data indicate that:

1. The clays and shale in Unit II in the immediate vicinity of Wells W-3 and test hole TH34 should function as an effective confining bed.
2. Hydrogeologic correlations of Unit 11 between test hole TH 34 and W-3, and between Well W-3 to Well W-1, and from Well W-1 to W-2 are reasonable.
3. Correlations based on gamma-log interpretation must be qualified
  • because of the relatively long distance between Well W-3 and W-1, and the fact that strata can thin or thicken appreciably from one well to another.

Additionally, structural discontinuities of _beds, such as faults, can occur between widely-spaced wells, and unless recognized, can cause errors in stratigraphic correlations. However, there is no evidence of un_usual thickening or thinning of strata or of structural displacement between these wells (Fig. 4-1), nor are there published references available that in-dicate that such structural discontinuities exist in this area. It should be noted, in fact, that there are several gamma-log "kicks" within Unit II that can be reasonably correlated between these wells.

Hydrogeologic Unit 111 The hydrogeologic properties of Unit 111 can be inferred from descriptions of Well W-1, the reported data on Well 30Q-6, a stratigraphic sample from Well W-2, and from the regfonal analysis of well data -in the vicinity of the WEC site.

As shown in Fig. 4-1, Well W-1 penetrated the full thickness of the Black Mingo Formation, and reportedly encountered packed sand in the interval from 71 ft to 140 ft. The gamma and caliper logs indicate that a sand occurs from 71-76 ft which is not caved into the borehole. This would support the packed sand de-scription. As shown in Fig. 3-1, this sand is interpreted to be a basal sand of the Black Mingo Formation. This interpretation is consistent with that of Padgett ( 1980) who showed that the Black Mingo Formation in southeastern Rich-SOIL & MATERIAL ENGINEERS INC.

land County contained a basal sand, overiain l:>_y -clays.

Well 30Q-6 reportedly produced 105 gpm with a drawdown of 15 ft, indicating that the well had a theoretical specific capacity of about 7 gpm /ft of drawdown.

This specific capacity is within the range of other O /s values of wells tapping Black Mingo artesian aquifers in southern Richland County. The fine- to coarse-grained sand obtained from the bottom of Well W-2 is interpreted to be from Unit II I.

Water-level measurements in Wells W-1, W-2, and W-3 made on November 19, 1981 indicate that ground water in Unit 111 occurs under artesian conditions, and the water levels in these wells rise approximately 1S ft to 20 ft above the top of this unit. These measurements indicate that the piezometric surface of Unit 111 slopes from northeast (from Well W-2) to southwest (toward Well W-3).

These data and data obtained from off-site Black Mingo wells indicate that the basal sand of the Black Mingo Formation at and in the *general vicinity of the WEC site is an artesian sand aquifer which is confined by the overlying clays in the Black Mingo Formation.

4. 1. 4 Tuscaloosa Aquifer System The Tuscaloosa Formation is a major hydrogeologic unit in southern Rich-land County, and underlies the Black Mingo Formation at the WEC site. Only one well [Well W-1] at the site is known to have penetrated into the Tuscaloosa

_.,-. Formation. Therefore, information on the hydrogeologic properties of the Tus-caloosa has been obtained from off-site wells tapping this formation. The Tus-cal*oo~a Formation is interpreted to be approximately 100-140 ft thick at the site.

The top of the Tuscaloosa Formation would be penetrated at an elevation of ap-proximately +30 to +40 ft MSL in the vicinity of the main plant and at approxi-mately mean sea level near the southeastern property boundary.

Well W-1 reportedly penetrated sand from about 71-140 ft. As shown in Fig.3-1 (Well 300-3), this well is interpreted to have penetrated the upper part of the Tuscaloosa Formation. Well 300-2, north of the WEC site, reportedly penetrated a sand at a depth of 200 ft, which is interpreted to be an artesian aquifer within the Tuscaloosa Formation.

Although considerable information is available on Tuscaloosa wells in south-eastern Richland County, few wells are known to have penetrated this formation SOIL & MATERIAL EIIIGINEERS INC.

within several miles of the site. Therefore, the .specific water-bearing proper-ties of this aquifer system at the WEC site can only be inferred from the re-gional data (see Sec.3.2.2). If the Tuscaloosa Formation is only 100-140 ft thick beneath the site, the prolific artesian aquifers within this formation in southeastern. Richland County would not be expected to exist at the site. It is reasonable to inferr that at least several artesian sand aquifers occur within the Tuscaloosa Formation at the site. However, because of the hydrogeologic na-ture of the overlying Black Mingo Formation summarized in this report, the hydrogeologic properties of the Tuscaloosa Formation are considered to be of minor importance in the analysis of the hydrogeology of overlying units.

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4. 2 HYDRAULIC PROPERTIES
4. 2. 1 General Principles The hydraulic properties of an aquifer which are important in predicting the hydraulic performance of an aquifer are hydraulic conductivity (K), transmissivity (T), storage coefficient (S), and specific yield _(Sy). The radial, or horizontal, velocity of ground water moving throug~ a granular aquifer is controlled by the porosity of the aquifer (n), the hydraulic gradient (dh/dl), and the hydraulic conductivity (K).

The hydraulic conductivity is actually the volume rate of flow of ground water through a unit cross-sectional area of an aquifer (measured at right-angles to the ground-water flow direction, at a certain viscosity). The K is expressed in units of length /time, commonly in cm /sec or ft/day. For many years, th~ K was commonly called "field perme~bility" and was exp_ressed as gpd /ft 2

  • The transmissivity (T) of an aquifer ls simply the K times the saturated thickness (m) of the aquifer; it is the rate at which ground water is transmitted through a unit width of an aquifer at a unit hydraulic gradient. Units of T are generally expressed as ft2/day or as gpd/ft in older hydraulics literature.

The storage coefficient (SJ of an artesian (or confined) aquifer is basically equivalent to the specific yield (Sy) of a water-table (or unconfined) aquifer.

These are dimensionless coefficients that express the storage properties or be-havior of aquifers. The S is the volume of water an aquifer releases from or takes into storage per unit surface area of the aquifer per unit change in head.

The S of most confined aquifers ranges from about 10-S to 10- 3, and the S (or Sy) of most unconfined aquifers ranges from o. 1 to o. 3.

The radial, or essentially the "horizontal", velocity of ground water moving through a porous aquifer can be calculated from K, n (porosity), and the hydrau-lic gradient. The average linear velocity, v, can be calculated with a modifi-cation of the Darcy equation:

- K dh (Eq. 4-2) v=n ar The vertical movement of ground water from one aquifer through a confining bed into another aquifer is controlled by the vertical hydraulic conductivity of the confining bed (K'), the thickness of the confining bed (b'), and the differ-SOIL lo MATERIAL ENGINEERS INC.

i

ence in hydraulic head of the two aquifer*s, or head *differential (dh). The ver-tical movement of ground water through or from the release of storage in a con-fining bed is termed leakage, and an aquifer which gains or loses ground water by vertical leakage is termed a leaky aquifer.

4. 2. 2 Hydraulic Properties of the Terrace Unit Available information on the hydraulic conductivity of the Terrace Unit is summarized in Table 4-1. These values* express the lateral, or radial, hydraulic conductivity (K) of strata within the Terrace Unit. These five wells are located In a radial line south of the waste-storage facilities and are therefore located in the area of most importance. The K values range from o.* 02 ft/day to 0. 88 ft/day.

These values are within the general range of K values for a silty sand or sandy silt. In terms of ground-water production and contaminant movement, these are ge:nerally low values.

Because of horizontal stratification of beds in the Terrace Unit, the vertical hydraulic conductivity (K 1) of strata within this unit should be expected to be much less than the values In Table 4-1. Therefore, the lateral flow rate of ground water moving through the Terrace Unit should logically be much greater than the vertical flow rate. This greater lateral flow would tend to cause greater lateral dispersion of contaminants.

Assuming a saturated aquifer thickness of approximately 25 ft, and an average K of 0. 37 ft/day, the average transmissivity (T) of the Terrace Unit would be approximately 9 ft 2/day (or 67 gpd /ft). These are comparatively low T *values, and indicate that strata. within this unit would be considered a very poor aquifer in terms of ground-water production potential for this part of the upper Coastal Plain. However, it would not be unusual that locally the K of sands within this unit could be high enough to yield small to moderate quanti-ties of ground water (approximately 5-20 gpm) _to wells.

With lithologic logs of the monitor wells located south of the main plant 1 reasonable estimates of hydraulic conductivity can be made in additional monitor wells. Therefore, the permeability of strata within Unit I _is fairly well docu-mented with the data available from the Davis and Floyd ( 1980) and Letco ( 1980a; 1980b) reports.

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I .*:il TABLE 4-1.

SUMMARY

OF HYDRArJLIC CONDUCTIVITY DATA ON THE TERRACE UNiT, WEC SITE, (data from LETCo~* 1980a).

LAND SURFACE HYDRAULIC CONDUCTIVITY, K SCREENED INTERVAL WELL NO. ELEV. (Ft) cm/sec aod/ftZ ft/day BELOW LS ( Ft) ELEVATION, (Ft, M!iLJ W-7 134.1 1. 2 X 10- 4 2.5 0.34 15.5 - 18.5 118.6 - 115.6 W-9 135.2 3.1 X 10- 4 6.5 0.88 15.S - 18.S 119.7 - 116.7

-5 w

I W-10 138.3 8.1 X 10 1. 7 0.02 18.5 - 23.S , 119.8 - 114.8 f ,*,

W-12 136.8 1.2 X 10- 4 2.5 0.34 25.5 - 28.S 111-.3 - 108.3 W-14 134.S 1 .1 X 10- 4 2.3 0.30 23.5 - 28.5 111. 0 - 106. O

4. 2. 3 Hydraulic Properties of the Black Ming~ Units Quantitative hydraulic data on the monitor wells penetrating the Black Mingo Formation ( Units II and 111) are not available. However, interpretation of data collected from test hole TH3/J and geophysical logging of Wells W-1, W-2, and W-3 provide a reasonably good qualitative indication of the hydraulic behavior of the upper Black Mingo Hydrogeologic Unit (Unit II), which is the unit of importance in regard to possible downward leakage of ground water.

At test hole TH34, Black Mingo strata in the interval 27 ft to 85 ft below land surface is composed primarily of light- to dark-gray clays, shale and clay-:

stone (Append.ix Table 4-3), Except for some moisture in the upper 3 ft of this unit, these beds were dry when samples were obtained during the test drilling.

The clays become plastic when wet in the laboratory. The shale bed from 4~57 ft is massive with a conchoidal fracture when samples are broken, Field and laboratory estimates of the radial K of these clay and shale beds range from less than 10- 7cm/sec to 10- 10cm/sec. Because of the massive structure of these beds, the vertical K is estimated to be in the 10- 9 cm/sec to ,o- 11 cm/sec range.

A one-ft thick bed of dry, fine, clayey silty sand and silt occurs from 64-65 ft, The K of this bed is estimated to be less than ,o- 5cm/sec.

A split-spoon sample from the Black Mingo (Unit II) in Well W-3 at a depth of 78-79. 5 ft below land surface is also composed of gray, plastic clay. The K and K' of this clay are estimated to be extremely low also (less than 10- 7cm/sec).

These data indicate that Unit II is a very effective confining bed in the vicinity of T*p4, W-34, and W-3. Additionally, gamma log correlation* from Well W-3 to Wells W-1 and W-2 (Fig.4-1) incicates that at least the upper 30 ft of the Black Mingo Formation is composed of clay or silty clay. Even though the gamma log does not provide quantitative hydraulic data, reasonable interpretation indicates that the Unit II underlies the Terrace Unit (Unit I) In the area from the main plant build-ing to Well W-3 and TH34 near Sunset Lake. The confining bed also extends north of Well W-1 to Well W-2 (Fig.4-1).

Specific hydraulic data are not available on the hydraulic properties of Unit 111. However, based on the information reported for Well 30Q-6 and the split-spoon sample from Well W-2, this unit should have a relatively high K. That is, a well with a specific capacity of 7 gpm /.ft indicates an artesian aquifer that would yi~ld several hundred gallons per minute of ground water to a properly constructe

_ 4 0- m"***m*-,.***..... ~.

  • water well located near the main plant buifding. _However, artesian Black Mingo aquifers in the general vicinity of the site are relatively thin, contain poorly sorted sediments, and Black Mingo wells have erratic yields.

4.3 UTILIZATION AND MOVEMENT OF GROUND WATER

4. 3. 1 General Concepts and Ground-Water Pumpage Ground-water movement through aquifers and relatively permeable confining beds is controlled by natural features such as locations of recharge and discharge areas, rainfall and rainfall departure, and othe_r climatic events, such as rainfall duration and intensity, and stratigraphic relationships of adjacent strata, and the

,. hydraulic properties of these strata. Ground-water fluctuations and ground-water flow directions and rates are also affected by man-induced factors, such as co~struction of drainage facilities and most notably by pumping of wells. In order to* provide a reasonable evaluation of ground-water movemerit, it is necessary to consider all of these natural and man-induced factors, even though detailed evaluation of each factor is unnecessary.

Ground water within the boundaries of the WEC site is currently not utilized as a source of drinking water nor for industrial process use. Well W-5, a small-diameter well, with a reported depth of 22 ft, has reportedly been used in the past for washing machinery and similar purposes. Therefore, except for this well, there is no ground-water pumpage within the property boundaries of the WEC.

There is currently no pumpage of ground water on properties immediately ad)acent to the WEC site. Much of the area south, southeast, southwest, and west of the site is undeveloped wetland which lies below the 100-year flood ele-vation of approximately 130 ft MSL. Several tracts of farmland south of Sunset Lake and west of the site are utilized during the farming season, but there is no ground-water pumpage in these areas. Relatively small quantities of ground water are withdrawn from wells in areas north, northeast, and east of Bluff Road (Co. Road 48). However, to our knowledge, there are no pumping wells located within an approximate radius of 2000 ft of the main plant building.

Artesian sand aquifers occur within the Black Mingo and Tuscaloosa Forma-tions in areas surrounding the WEC site. The effects of pumping on an artesian aquifer can extend for hundreds or several thousands of feet, depending on the SOIL & MATERIAL ENGINEERS INC pumping rate and hydraulic properties of the ~quifer-. Whether a sufficient quantity of ground water could be pumped from artesian aql!ifers within the Black Mingo and Tuscaloosa Formations in areas adjacent to the site that wou 1d significantly influence the movement of ground water in these aquifers at the site is not currently known. However, pumpage from wells in the vicinity of the site would have ~o be much greater than the quantity currently pumped in order to significantly affect ground water flow directions and rate at the site.

,;: These data indicate that ( 1) presently there is no significant ground-water pumpage from the Terrace Unit or from the Black Mingo and Tuscaloosa artesian aquifers that influences the flow of ground water in these units beneath the WEC site and ( 2) it is doubtful that a sufficient number of wells could be loca-ted sufficiently close to the site to affect ground-water flow in the area soutti-west of the main plant. Additionally, as discussed later in this report, it is doubtful that pumpage from artesian Black Mingo or Tuscaloosa aquifers could significantly affect the movement of ground water within the Terrace Unit.

4. 3. 2 Lateral Ground-Water Flow -- Terrace Unit The lateral flow of ground water in the Terrace Unit was studied by Davis and Floyd ( 1980) and by LET Co ( 1980a, 1980b)
  • A piezometric map of the area south and southwest of the waste treatment facilities was made by Da.vis 6 Floyd Engineers ( 1980, Fig. 1) from water-level measurements obtained in Phase I observation wells. A second piezometric map was made by LETCo from water-level readings of_ 28 observation~ wells on July 16, 1980 (LETCo, 1980b, Fig. 1) From these maps, Davis & Floyd and LETCo concluded that the lateral flow of ground water south of the main plant was toward the south-southwest into the pond and Sunset Lake, and they correctly inferred that the pond and Sunset Lake inter-sected the water table within the Terrace Unit. Our interpretation of flow, made from measurements ~ade in November, 1981 (Fig. 4-4) supports the original con-clusions of Davis & Floyd and LETCo.

A number of water-level measurements have been made in the monitor wells at the site by WEC personnel. A piezometric map of the Terrace Unit from water-level measurements made by WEC personnel on November 15, 1981 is shown in Fig. 4-4, and other water-level measurements are summarized in Appendix Table 4-2.

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These piezomet.-ic maps and other hydrog~ologic* data summarized in this re-port indicate that the principle controls on the lateral flow of ground water in Unit I are ( 1) locations of local recharge and discharge areas, ( 2) horizontal stratification of strata within Unit I, and ( 3) the p-resence of the upper Black Mingo confining bed (Unit 11) which restricts downward flow of ground water.

Therefore, our conclusions of lateral ground-water movement through Unit I are consistent with those of Davis & Floyd ( 1980) and LET Co ( 1980b) that:

1. Ground water in the Terrace Aquifer System flows in a south-southwesterly direction toward Sunset Lake.
2. The predominant movement will continue to be in this direction, under natural hydraulic gradients, which will be the predominant direction of longitudinal dispersion.
3. The spring, pond, and Sunset Lake are point or line-sources of ground-water discharge which will tend to act as hydraulic barriers to the movement of contaminants past Sunset Lake.

These conclusions are also consistent with those of hydrogeologists with the SCOH EC ( 1981)

  • They showed that ground-water flow is controlled by topography and locations of local discharge areas. They also illustrated ( 1981, Figs. 13-17) that the ground-water flow direction in the surficial aquifer is influenced by differential recharge rates; and that flow directions vary depending on the time water-level measurements are made relative to local rainfoll events. However, flow direction changes at the SCR&D site were relatively minor and would not significantly affect the directions and rates of ground-water movement in this shallow, water-table aquifer.

The hydraulic gradient (dh /di) of the water table can be measured from the piezometric map (Fig. 4-4). This gradient is utilized in the modified Darcy equation (Eq. 4. 2) to calculate the average linear velocity, v, of ground water.

If a reasonable porosity value (n) of 30 percent for Unit I is chosen, an average hydraulic gradient of O. 025 ft/ft is measured from Fig. 4-4, and let K= O. 4 ft/day, the v would be approximately 2. 5 x 1 o- 4ft/day (= 0.1 ft/yr). If we let K =

10 ft/day, which is probably more representative of the more permeable strata within the Terrace Unit, the v would be approximately O. 9 ft/day (=. 325 ft/yr, rounded). These values represent an extremely wide range for the average linear velocity of ground water moving through this unit, and it is reasonable to expect that average linear velocities would vary considerably.

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Lithologic analysis of samples from test h9le-TH 34, an analysis of boring logs prepared by LETCo ( 1980a, 1980b) and the geophysical logging indicates that the basal part of the Terrace Unit probably contains the most permeable strata. This basal unit, shown in the hydrogeologic cross-sections, is interpreted to be approxi-mately 10 ft to 1S ft thick and is composed of sandy gravelly silt or fine sand containing variable amounts of gravel and clay. The K of this thin unit is esti-mated to be several orders of magnitude higher than Unit 11 strata and overlying strata within Unit I. Therefore, the comparatively higher K of this basal unit should be expected to dominate the direction and rate of ground-water movement through Unit I.

4. 3. 3 Vertical Ground-Water Flow -- Leakage In order to calculate the amount of vertical leakage through or the release of; storage in a relatively permeable confining bed, it is necessary to know the lithology, thickness, and vertical h'ydrci"ulic conductivity (K') of the confining bed, and the hydraulic heads at the top and bottom of the confining bed. It is also necessary to determine the lateral continuity of the confining bed and the hydraulic characteristics of units overlying and underlying the confining bed.

The most common methods for deterr.ining leakance of a confining bed (Jacob-Hantush or Modified Hantush) require a pumping well with properly positioned observation wells. Use of these methods is ideally suited to water-supply hydro-geology where ( 1) confining beds are relatively permeable, ( 2) where considerable leakage of ground water from storase within a confining bed is expected or known to occur, ( 3) long-term pumFing from a well or wells in an artesian aquifer below the confining bed is possible, and ( 4) there is very little concern for in-troducing any possible contaminants into an artesian aquifer with the artificially-created head differentials. Condit>;ms ( 1) through ( 3) are not expected of Unit II at the WEC site: Since condition (4) requires reasonable caution, these methods are generally not ideally suited to analyzing leakage of Unit 11 at the site. Therefore, the hydraulic character of Unit 11 was evaluated by ( 1) utiliz-ing available K data from the Terra:~ Unit (Table 4-1), stratigraphic sampling of Wells W-2 and W-3, and by ob:airing split-spoon samples for analysis from test hole TH 311.

Originally, test hole TH34 w2s :~ be completed as a 4-inch diameter monitor well in the uppermost aquifer wit~ir. the Black Mingo Formation (Unit 111). Well

~"" ""'"""'""'""""~

  • W-:-34, a 2-inch diameter monitor 'Melt, was to be located immediately adjacent to

TH34, with the screen set opposite the basal strata within Unit I. However, de-tailed stratigraphic sampling of test hole TH34. (Appendix Table !1-3) indicated that Unit 11 is composed of 58 ft of relatively impermeable clays and shale. Thus, installation of a screen in this test hole was not necessary and the borehole was grouted and plugged. Well W-34 was completed in the basal strata within Unit I to provide an additional water-level and water-quality monitor well at a strategic location.

Estimates of radial and vertical hydraulic conductivity of Unit 11 and the

  • geophysical logging indicates that this unit is an effective confining bed or aquiclude, in the area near the pond and Sunset Lake between Wells W-3 and test hole "rH 34. Interpretation of Fig. 4-1 indicates that along a subsurface pro-file from Well W-3 to Well W-1 it rs reasonable to conclude that Unit II is laterally continuous between these wells; and from test hole TH 34 to Well W-1. This con-clusion is also supported by the reported description of gray clay from about 30 ft to 105 ft in Well 30Q-6 (the 1963 well} and from off-site data from SCDHEC Well Q 29-fl which penetrated several feet of clay at 45-47 ft below land surface (SCDHEC, 1981}. The estimated K1 values of 10- 7cm/sec, and conservative Unit 11 thickness of 20 ft in the area southwest of the main plant would require extremely high vertical hydraulic. gradients to artificially induce the movement of ground water from Unit I through Unit 11, even neglecting any ionic exchange between ground water from Unit I and any moisture in Unit 11. As mentioned in Sec. 4. 3. 1, there are no producing Black Mingo water wells on the site or sufficiently close to the WEC site which could create such high artificially induced vertical hydraulic gradients.

SOIL & MATERIAL ENGINEERS INC.

i

  • I
5. o

SUMMARY

OF CONCLUSIONS 5.1 HYDROGEOLOCIC UNITS AND GROUND-WATER MOVEMENT This study indicates that three major aquifer systems underlie the WEC site that have been correlated in wells located off the site. The shallowest aquifer sys-tem is the Unconfined Aquifer System which is approximately 30 ft to SO ft thick in the vicinity of the site. At the WEC site, this aquifer system has been designated as the Terrace Hydrogeologic: Unit in this report and is equivalent to the Okefenokee Formation, composed of sediments of Pliocene to Pleistocene age.

1J<

The Black Mingo Formation (Aquifer System) underlies the Terrace Unit and has been shown to consist of two hydrogeologic units. The upper part of the Black Mingo Formation has been designated as Hydrogeologic Unit 11 and consists of relatively low permeability clays, shales, and claystone which act as a confin-ing bed. A basal sand within the Black Mingo Formation has been designated as Unit 111 and is an artesian sand aquifer which is tapped by several monotor wells at the site.

The Tuscaloosa Formation lies between the overlying Black Mingo Formation and underlying crystalline basement rocks, and has been interpreted to be approximately 100 ft to 140 ft thick at the site. One monitor well has penetrated into the top of the Tuscaloosa Formation at the site, and information from off-site Tuscaloosa wells has been used to correlate Tuscaloosa strata from off-site wells to this well. The Tuscaloosa Formation has been designated as Hydrogeologic Unit IV In this report. The hydrogeologic properties of Unit IV have been summarized fn;,m a considerable number of Tuscaloosa wells in southeastern Richland County.

At the WEC site, the hydrogeologic properties of aquifers and confining beds within this unit are considered to be less important than Jhe properties of overlying geologic formations.

The hydrogeology of the Terrace Unit in the area between the main plant and Sunset Lake was discussed in some detail in a hydrogeologic Investigation by Davis & Floyd Engineers. This investigation involved the construction of 28 monitor wells in Unit I, and the well construction and hydrogeology of the Terrace Unit was described in two reports prepared by LAW Engineering and Testing Company (LETCo). The number of monitor wells installed during the Davis & Floyd ( 1980) study and the hydrogeologic information obtained adequately presented the hydrogeology of the Terrace Unit. Therefore, additional monitor SOIL & MATERIAL ENGINEERS INC.

wells were considered unnecessary.

Geophysical logging of on-site monitor wells and the construction of one test hole at a strategic location have added considerable ~nowledge to the hydrogeology of the Black Mingo Formation as well as the Terrace Unit beneath other parts of the site. A pronounced "kick" or signature on gamma ray logs can be used to trace the contact between the Terrace Unit and underlying confining beds of Unit II.

The lateral flow of ground water in the Terrace Unit (Unit I) in the area between the main plant and Sunset Lake has been shown to occur in a south-southwest direction. Ground water flowing through this unit in this area of the site, discharges into a small spring, a pond, and Sunset Lake, and it is unlikely that contaminated ground water would move past Sunset Lake. There are no Terrace Unit water wells located in the area south of Sunset Lake.

Information collected during this study indicates that the upper part of the Black Mingo Fcrmation (Unit 11) is a relatively effective confining bed that would tend to reduce the possibility that ground water will move by downward vertical leakage into underlying aquifers. Estimates of vertical hydraulic conductivity (K')

are *m the range of 1 O- 7 cm/sec to 1 O- l l cm / sec. S *mce th ere .1s no pumpage f rom the artesian B!ack Mingo aquifer (Unit 111) at the site, any vertical leakage would have to be caused by natural hydraulic gradients. It is unlikely that the low natural hydraulic gradients between Units 111 and I could cause th~s leakage, even if vertical hydraulic conductivities were many times greater than those estimated from the available data.

-\

5.2 GROUND-*1tATER MONITORING PROGRAM A considerable number of monitor wells (30) are available for monitoring the direction and rate of ground-water movement and the potential movement of con-taminants in the Terrace Unit. Most of these monitor wells are located south of the main plant in the main area of concern. A review of these monitor well lo-cations and the vertical placement of well screens and water levels indicates that:

1. r,e number and areal distribution of monitor wells between the plant and Sunset Lake are adequate to define ground-water flow direction and the poten:ial movement of contaminants in this area. The number and lo-cations of monitor wells located in other parts of the site are limited. At SOIL 6 MATERIAL ENGINEERS II\IC this time, however, the need for additional monitor wells in these areas has not been demonstrated with the data currently available. If water-level monitoring is continued on a systematic basis,. the range of water-level fluctuations can continue to be defined,- and piezometric maps can be used to interpret ground-water flow directions.
2. An analysis of well-screen positions with respect to Terrace Unit thickness and water table positions_ within this unit indicates that the screens in wells located between the main plant and Sunset Lake are adequate-ly positioned.

Three environmental monitor wells at the site currently tap* the Black Mingo Formation. Geophysical logging of these wells and information from one strati-graphic test hole near Sunset Lake indicate that these three wells can be used to mopitor the piezometric surface of Unit 111. Therefore, the need for additional Black Mingo monitor wells has not been Indicated on the basis of information evaluated for this study.

-i SOIL & MATERIAL ENGINEERS INC.

_I

6, 0 SELECTED REFERENCES Colquhoun, D.J., 1965 Terrace Sediment Complexes in Central South Carolina:

Atlantic Coastal Plain Geological Association Field Conference 1965 Guidebook, 62 p.

Colquhoun, D.J., Heron, S.D., Jr., Johnson, H.S., Pooser, W.K., and Siple, G.E., 1969, Up-Dip Paleocene-Eocene Stratigraphy of South C.arolina:

S.C. State Development Board, Division of _Geology, Geologic Notes, v.13, no. 1, p. 1-25 *

. Davis & Floyd, Inc., Consulting Engineers, 1980, Groundwater Investigations, Westinghouse Electric Corporation Nuclear Fuel Division, Columbia, South Carolina, Unpublished Consulting Report, Job Number 3067-1.

Getzen, R. T., 1969, Cretaceous Stratigraphy of the Upper Coastal Plain in Central South Carolina: M.S. Thesis, University of South Carolina, Columbia, South Carolina, 67 p.*

Hantush, M.S., 1955, Nonsteady Radial Flow in an Infinite Leaky Aquifer:

Am. Geophys., Union Trans., v. 36, no. 1, p.95-100.

i

___ ...:._, 1960, Modification of the Theory of Leaky Aquifers: Jour. Geophys.

Research, v. 65, no. 11, p. 3713-3725. *

  • Johnson, Phillip W., 1978, Reconnaissance of the Ground Water Resources of Clarendon and Williamsburg Counties, South* Carolina,: S.C. Water Resources Commission Report #13, *columbia, South Carolina, 72 p.

Law Engineering Testing Company (LETCo), 1980a, Report of Preliminary Geohydrologic Assessment Westinghouse Nuclear Fuel Facility, Columbia, South Carolina: Consulting Report No. CO-537, dated June 12, 1980, 9 p.

, 1980b, Phase II - Generalized Geohydrologic Exploration Westinghouse Nuclear Fuel Facility, Columbia, South Carolina, Consulting Report No.

CO-537, dated August 1, 1980, 11 p.

Lohman, S.W., 1972, Ground-Water Hydraulics: U.S. Geol. Survey Prof.

Paper 708, 70 p.

Padgett, Gary G., 1980, Lithostratigraphy of the Black Mingo Formation in Sumter, Calhoun, and Richland Counties, South Carolina: M.S. Thesis, University of South Carolina, 68 p.

Park, A. Drennan, 1980, Ground-Water Resources of Sumter and Florence Counties, South Carolina: South Carolina Water Resources Commission Report 133, 43 p.

Pooser, W. K., 1965, Biostratigraphy of the Cenozoic Ostracods from South Carolina: University of Kansas Paleontologicar Institute ( 38),

Arthropoda, Art. 8, 80 p.

Siple, G. E., 1957, Ground Water in the South Carolina Coastal Plain: Jour.

Am. Water Works Assoc., v. 49, no. 3, p. 283-300.

, 1959, Guidebook for the South Carolina Coastal Plain Field Trip of the Carolina Geological Society, Nov. 16-17, 1957: S.C. State Dev.

Bd., Div. of Geology Bull. 24, 27 p.

SOIL & MATERIAL ENGINEERS INC

-119-

Smith, G.E., Ill, 1979, Lithostra:igraphic Relationships of Coastal Plain Units in Lexington County 2,d Adjacent Areas, South Carolina:

M.S. Thesis, University of Sou:h Carolina, Columbia, 139 p.

SCDHEC, 1981, Investigation of C round Water at South Carolina Recyling and Disposal Company Bluff ~oad Site, Richland County, South Carolina: Ground-Water Prc-:ec:ion Division, S.C. Department of Health and Environmental Cc,:,tr.,l, Columbia, South Carolina, Open-File Report, 42 p.

South Carolina Water Resources C .:>m:lission, 1971, Water Use in South Carolina, 1970: Columbia, S.~ut, Carolina, 114 p.

Taylor, V .A., 1949, Geology of t..-ie ~olumbia North Quadrangle: M.S.

Thesis, University of South Carolina.

Van Nieuwenhuise, D.S., 1978, C str:code Biostratigraphy and Stratigraphy of the Black Minge Formation, South Carolina Coastal Plain: Ph. D. Disse:!"ta:ion, University of South Carolina, Columbia, South Caroitna, 92 p.

-so- SOIL & MATERIAL ENGINEERS INC.

APPENDICES i '

---, I I

--i Suulh C*rulln* __

SOIL & MATERIAL ENGINEERS WELL

SUMMARY

K1d1IJ11.J TAULE 3 I.

SUMMARY

OF WATER* WELL DATA, SOUTHEASTERN RICHLAND COUNTY, S.C l:ii.MI:: JOII 11.l, !::L.fil.ll.

r  :,1uL  :-r-s,:--;;  ! L tlludera*.;~~-1~-;;~:;::,Loc tlon -------

Woll Toni Cuing Cuing l'ump Dole Chomlcol Woll

,*, II ttu th,mller Longllulllll CMSL) UII D1plh Dlo, Doplh Roll Comp, LOIi ,\nolyHo Cana. Aem1rk1 i

! ll !iti W1terce Cun Club P,S, Camma Unk.

I

'""

  • 1 80 39 Near Wueree R, I

2uQ 1 26Q*WI 165 Te&t Well Ind. Sydnor Hyrodyn1mlcs I Tapo Hercules Site Test I Estm.

,--**;;.,. 1 I

11,ll X I llh 1111 .......

1115 I *lln, Tu51 Woll 11111, 11111 bllu .......

1ml, t.70 II 11/73 Drlllan re .....

~y,lnur lly*h udynt1111lu, I C11llllllhl ..

I 11.11 I 11,11 *1 I 1111 1111111 I ... 1 vi .. 11

( 11111 hold I hi, 11111111 I **I 1,1,11 1111*.

11/1 /IU I o1y11u All,mlh.

,c.ic I J1o1C-,J1

'-*Im, 1ml, !.llu Cad*1u:,:d F11rm1 Irr, 6U0 Ru11, CP L11y ne A t11n tic No. I Cammi See Padgett, 1981, (26R-dl) Su1>*>lles Cenler Dluo* 1--*- c ..*

26R*2 Topo ** Teat Hole on Bates Old River Test 3911 Ceologlc Geuen ( 191i9, DH 5-1)

I I

i

! E1tm. I 2~R-3 26R-cl 1115 Test Well Ind 5911 10 1115 20110 6/7'1 Drlllers Sydnor Hydrodynamics. 10" SCN: 103' from 1117-5112 Ft, R rC-6J Hercules Site Test ees-amma (Park, 1910).

HQ-I Codspei:d F11rms Irr, None Unk. Burrle \Yell Drilling No, 2 PumfJed 2000*2500 CPM for ! 3 Mu*/Yr.

Supplies Cenler Pivot lrrig. Sy*tum.

Z7Q-2 Eastover CW No. 2 P.S. 120 6 102 120 1/76 C1mma GP Coleman Well Co, Samples to SCDHEC at "N,:w" Watur 1/16/76 SCN~&" dla, 102*112, WW, ,045 Slut Tank, I 27Q-l RIC-60 Eastover CW No. 3 P.S. 156 3/77 Drlller1 Unk.

I Camma Heater Well Co. SCN: 77-87 Samples to SCDHEC Gdmma Loo bv H1111tur w.,11 I

.tu; l*'UHM 11-03 (4/~l)

I - ~ -*'* *

    • ! .- .. - *., * ~ I ,_. * * * * '

"i:

  • I Soull~ £ilrolini!' __

SOIL & MATERIAL ENGINEERS WELL

SUMMARY

,, ' Richland TABLE l 1,

SUMMARY

OF WATER-WELL DATA, SOUTHEASTERN RICHLAND COUNTY, S,C. !Ir.Ml~ JOII !Ill, H-8119 1 l.lLI~

Wull llu TI  ;,a~~-.-.:-;11,ud rEl .. llon Number longllud I CMBLl Own r/Looallon w~i, Uaa Tol*l1c"i"i1no'culngl D plh DI , ID plh RPump' Dall la Comp.I Loa Chomlc I An lv***

I Wall Con

  • R1m rk1 1270 q IRIC-153 I I !360 Topo R. S. Henderson Dom.I 201 89 10 I 9/591 Drillers Unk,I West Columbia Well Drilling, 9/59.

I I Estm.

1270*5 33 53 151 80 q3 15 210 Topo Test Hole Test I sqq Ceologlc Cetzen (1969, DH S-51) TD IN Basement al 5110 (-330 MSLJ.

2BP-1 33 SB ao q1 1110 Water Well Near Ml. Elon Ch.

I Dom,I Z05 19611 Unk,I See Cetzen I1'HI Upper Marine MBR Kte.

280-1 33 5q 25 McEntlre Air P.S.I 70 Comp 80 117 50 National Guard 1/18/68 SCN Repl, 65-70 Ft.

B se 280*2 33 5q 10 McEntlre Air P,SJ 127 Comp BOO 35 National Guard 1/18/67 SCN Repl, 11!*127 Ft.

B se 29P-1 RIC-77 j33 57 Defender Indus. I Ind, 6 Camm Unk.,

80 56 9031 Garners Ferri PVC 10/20/78 Rd. uses 29P*2 RIC-10 Ill 57 80 56 Mr. McGregor Hopkins Hwy (Co.

I Dom,1 301 I

-- STL 8 I 210 Drillers (good)

CP Healer Wall Co,, 1956 Screen: an di , 210-2111; 210-nq; Rd. 37) 280-2811: & 290-2911, 29Q* 1 Q29-f1 135 Test Well Mon.I 117 I 2 I 17 8/80 I Ceologlst I Comp I Yes SCDHEC (1981). 211 PVC SCN 17-22 SCDHEC Topo SCDHEC Sita W~I PVC (DHECI SCDHEC Pen, Tight Clay at 115 Ft.

Estm, SCR&D 29Q 2 Q29-f2 135 Test Well SCDHECIMon, 1 311 I 2 I 9.5 8/BOICeologlsll Comp I Yes I SCDHEC (1981) 211 PVC SCN 9.5-1Q,5, SCDHEC Topa SCR&D Site Well PVC (DHEC) SCDHEC Estm.

z90 .. 3 Q29-f3 135 Test \Veil SCDHEC1Man, 1 211 I Z I 111 B/BOICeologlstl Comp I Yes I SCDHEC (1981), zu PVC SCN 1q-19 SCDHEC Topo SCR&D Site Well PVC (DHECJ l5CDHEC Estm.

,:..'U'. I\IJ<M II-OJ (4/Ul)
  • *,l

~1!~11-: South C rolln* SOIL & MATERIAL ENGINEERS WELL

SUMMARY

tH~ll'V Richland TABLE 3-1.

SUMMARY

OF WATER-WELL DATA, SOUTHEASTERN RICHLAND COUNTY, S.C S&ME JOB 00, H-8119 lwUMEall Na.

BIiia Number Latitude Elaullon anglludo ( M SL) Ownar/Loaallan Wall Tolll c.;,ng cuing Pump Data U11 Daplh Dia. Daplh Raia comp. Loa*

Ch mla I AnalyHI Woll Con

  • Remark 290-4 135 Campbell's ABN 28 2 Gamma Comp No SCDHEC (1981)

Topo Garage Dom STL S&ME SCDHEC Estm, 290-1 3q 00 qg Twin Lkes Rec; P,S, 113 6 103 Drlllers Heater- Well Co., 9/69:

10 5/f 18 Are , Ft, Jackson 1 11 SCN. 103-108.

290-2 RIC-511 34 03 00 BO 59 00 U.S. Army Ft. Jackson P,S, q&o

. 6 Geologic Lllhologlc Log-USGS 290-3 RIC-53 3q 02 55 U,S, Army P.S, 135 6 Geologlc Llthologlc Log-USGS 80 59 00 Ft, Jackson (1) Sox Brothers Orig, lOP-1 33 57 Domestic Well Dom, 136 80 55 Ne r lntersec, Co Rapt, 101 of Perm, S nd Underlying Clays Rd 88 & Hwy 76 D t Drlller- unknown.

30P-2 33 56 153 Atlas Road SCH, ABN 115 Driller rept.25-115 ft only clays.

80 58 .J"opo.. Te t Well Rept, Rept, Abandoned test hole.

Estm, Data lOQ-1 RIC-61 150 Larson Property Dom. 39.5 Gamma Unk.

Topo, Bluff Road. 5/17/77 Estm, lOQ-2 ns Private Well Dom. 200 Unk, Unk. Unk, Drlllcr rept. 0-20 black mud 6 water;20-200 rt "Impermeable" clay; at 200 rt Topo (1) ( 1) ,_

Estm. porous sand.

30Q-3 137 Well W-1 OBS 140 q 62 Unk. 1969 Gamma Comp PAR

~lie Westinghouse Elect. Rept. STL no +/- Callper WEC Rept. Orig, TD=}40 Ft No Screen.

ap Corp, (WEC) pump open-hole 71- 76 t.

76 tos61.M~ I ft""*" In 7~ l=t hv <;r.MF lOQ-11 tlll Well W-2 OBS 70 4 Not 1977 Gamma Comp PAR Caliper WEC Coleman Well DRLG.

~rl:*

Toco Westinghouse Elect.

Corp.

Rept STL Pump to :l.,}J Strat. sample 61-62 by S'1,IE.

SIJU.: !OHM 11-03 (4/81)

    • ,i
1 ','11 South Carolina SOIL & MATERIAL ENGINEERS WELL

SUMMARY

,,o1it*1'\* Richland SI.ME JOB NO H-8119

- TALBE 1-1  !;UMMARY OF WAH,~~.Q.~TA SOUTHEASTERN RICHLAND COUNTY S,C, i5Ult Stal a I LallludalEravallan Ownor/Loaallon Wall Talal Cuing Cuing P~;,P *D*I* Qeaphyaloal Charnlaal Wall R1rnark1 1 Wall Ma. Numbar Longlludo CMIL) U a Dapth Dia, Doplh Rall Comp, Loo* Anolyua Con,.

30Q*S 117.9 WEC Well W-3 OBS 79.5 qa Not 1977 Camm PAR Coleman Well Drllllng Sita Mao Ad( cent to pond near Sunset Lake STL Pump Caliper to li2 ft Geophysical Logs by S&ME I JOQ *6 Estm.

1qo WEC Unnumbered ABN Rept, II or Rept. 107 1963 None N,A, Unk. Exact TD unknown. Rept.30-105 ft.

Cray clay, Rapt produl:ed 107 gpm/15 rt 1b1ndoned well 105 6 105 Rept. R.ept.

I approx.

Estm WEC Well W-5 In IND Estm, 115 Unk. Estm, Pre Data Partial Unk

!."~:,'!.°!..~.!~~-';"~eked sand from 105 ft Driller unknown. Old domestic well; I 30Q*7 1311.0 SlteMp Equipment storage area 22
!: 5 1960'1 gpm WEC formerly supplled house, Now occaulon use for ~aner I yard u~e. Shallow (et oumo, n sm!.!l....E!i!!!J?..!!!IUSe, OBS 1Z q Estm, NA 1977 See geop. PAR  :

30Q*I 117, 5 WEC Well W-11 10 ft NE Well W-3 PVC 10 logs for Coleman Well Drllllng W-3 None Dec. Drlller11 NA Stratigraphic test hole, S&ME Rig CME-55 3UQ *9 125,0 :t \VEC Stratl~~hlc ABN 85.0 None estm Test Hole S 311). - 1981 Ceolqglst NA 18 spilt-spoon simples from LS lo TD

,~om ~° iftyf~fqt~ of WEC Pfug Llthologlc Logged In field g lab by hydrogeologlst.

levW-1! Term In Black Mlnao Formation.

' lOQ-10 125.0 estm WEC Well W-311 Location 80 ft W.

OBS 211, D 2 PVC 18 NA Dec See logs 1981 for Yes Obs S&ME;Rlg CME-55, 2-ln SCN IB-23 In basal Terrace Unit, gravel ~*ck(: Ben:! .

from of Pond, STH 311A Seal 111-1 fj; cement grout 0- II. sq.

  • 0 ElevW-1! ft abova WEC Wells W-6 See Borln!I Logs In LETCo Rapt. 1980b NOTE through W-33 See Remarks Ceologlst logs.

I I

I: *,*u* l\ 1"*1 11-01 (4/81)

I

.1 .1 \j TABLE LJ-2.

SUMMARY

OF WATER:..LEVEL DATA, WEC SITE NOTE: These water-level data are contained in Davis & Floyd ( 1981).

WELL ELEV. DATE WATER LEVEL MEASURED REMARKS NO. M. P. MEASURED BELOW -M~-P~1-ELEV. BY Phas,!! 1 Data 5/22/80 WEC Personnel See LAW ( 1980a) ( 11 Wells)

Wells 6, 7,8,9, 10, 11, 12, 13, 14, 15, & 16.

5/30/80 LA\A/ Engineering See LAW (1980a) (7 Wells)

Vlells 7,8,9,10,11,12,&13.

(missing were wells 6,14,15,16,17~.

6/3/80 LA~ Eng lneering See LAVI ( 1980a). ( 12 Wells)

(Piezometric A,1ap by Davis ~ Floyd, Wells 6 through 17.

1981, Fi9.l) 6/3/80 !Readings supplied See Davis & Floyd ( 1981, Table 111).

. by LA\'/ Engr. Wells 6* through 17. ( 12 Wells)

Phas~ 11 Data 7/10/80 LAW Engineering See LAW ( 1980b) (only 3 -\'iells)

Wells 18, 19, & 24.

7/13/80 LAW Engineering See LAW (1980b) (12 Wells)

/' Wells 18, 19, 20, 21, 22, 23, 24, 25, 26, 28, 29, & 30.

(missing were wells 6 through 17, 27, 31, 32, & 33). .

7/16/80 I , . I I LAW Engineering See LAW ( 1980b)

( Piezomefric Map, LAW, 19~0b, Fig. 1) (measured all 28 wells, wells 6 through 33).

7/16/80 !Readings supplied See Davis & Floyd ( 1981, Table VI).

by LAW Engr. Wells 18 through 33. (16 Wells)

I , *. ,,. - *--** - : ,., . .  : ... ~l *'g 1'ABLt: 4-2 *

SUMMARY

Ut- WA*1 t:K:..L1:v1:L DA.I A, WI:~ SI 11::

NOTE: These water-level data collected since completion of Da:'fis & Floyd ( 1981) Report

  • ELEV. DATE . WATER LEVEL MEASURED

-- REMARKS WELL NO. M. P. MEASURED BELOW M.P. ELEV. BY 1/21/81 Measurements frorr WEC Personnel Measurements made prior to bailing; TOC measurements in ft & in. (24 Wells measured). Wells 7 through 21, Wells 23 through 28, Wells 31, 32 & 33.

Did not measure Wells 6, 22, 29&30.

1/23/81 (Special Water Ari alysis Rep ort) 5/6/81 Measurements from WEC Personnel Measurements made prior to bailing.

TOC (27 Wells measured)

Measured Wells 6 through 33, except Well 22.

5/12/81 (Special Water Ar alysis Re~ ort) 9/1/81 '* WEC Personnel Measured. depth and water level in Well W-5 (intake pipe was remg:ved).

Well Is 21. 7 ft deep No water-level measurement.

11/15/81 Most measurement! WEC Personnel Measured all 28 wells.

made from TOC; (Wells 6 through 33). **

Some from L.S. See data on following page.

I

I

-* - .~-1 TABLE 4-2.

SUMMARY

OF WATER:..LEVEL DATA, WEC SITE WATER-LEVEL MEASUREMENTS NOVEMBER 15, 1981 NOTE: Water- level measurements in ft and inches. These were converted to decimal readings without rounding to nearest tenth: These should be rounded to nearest tenth I

  • WELL ELEV. DATE WATER LEVEL MEASURED REMARKS NO. M. P. MEASURED BELOW M.P. ELEV. BY W-6 137.81 11/15/81 11.25 126.56 WEC Personnel M.P. = L.S.

W-7 135.89 11/15/81 11.83 124.06 WEC Personnel M.P. = TOC W-8 134.34 11/15/81 13. 5 120.84 WEC Personnel M.P. = L.S.

W-9 137.0 11/15/81 11. 75 125.25 WEC Personnel M.P. = TOC W-10 138.28 11/15/81 17. 66 120.62 WEC Personnel M.P. = L.S.

W-11 141. 32 11/15/81 17.66 123.66 WEC Personnel M.P. = TOC W-12 138. 70 11/15/81 14.75 123. 95 WEC Personnel M.P. = TOC W-13 139.41 11/15/81 12.33 127.08 WEC Personnel M.P. = TOC W-14 136.50 11/15/81 13.92 122.58 WEC Personnel M.P. = TOC W-15 128.85 11/15/81 11.66 117.19 WEC Personnel M.P. = TOC W-16 129.48 11/15/81 7.16 122.32 WEC Personnel M.P. :;: TOC W-17 139.03 11/15/81 see remarks M. P. = TOC ( ?) stated as 4~ 511

(= 0.38 ft) above L.S. Reading listed as 12' 11 1= (?).

W-18 138.58 11/15/81 11.83 126.75 WEC Personnel M.P. = L.S. '

W-19 143.70 11/15/81 23.54 120.16 WEC Personnel M.P. = TOC ..

W-20 116.11 11/15/81 8.0 108.11 WEC Personnel M.P. = TOC W-21 117.90 11/15/81 J 10.33 107.57 WEC Personnel M.P. = TOC W-22 137.96 11/15/81 12.0 125.96 WEC Personnel M.P. = L.S.

W-23 140.66 11/15/81 16.5 124.16 WEC Personnel M.P. = TOC W-24 143. 17 11/15/81 12.75 130.42 WEC Personnel M.P. = TOC W-25 117.26 11/15/81 9.5 107.76 WEC Personnel M.P. = TOC W-26 142.82 11/15/81 23.08 119.74 WEC Personnel M.P. = TOC W-27 123.16 11/15/81 9.0 114.16 WEC Personnel M.P. = TOC W-28 139.95 11/15/81 12.25 127.7 WEC Personnel M.P. = TOC

-\i TABLE 4-2.

SUMMARY

OF WATER:..LEVEL DATA, WEC SITE WELL ELEV. DATE WATER LEVEL MEASURED REMARKS NO. M.P. MEASURED BELOW M.P, ELEV. BY W-29 139.9E 11/15/81 13. 58 126.4 WEC Personnel M*,P. = TOC W-30 138.37 11/15/81 11.92 126.45 WEC Personnel M.P. = L,S.

\V-31 138.24 11/15181 9,83 128.41 WEC Personnel M.P. = L.S.

\V-32 141.81 11/15/81 18, 16 123.65 WEC Personnel M.P. = TOC W-33 140.78 11/15/81 15,0 125.78 WEC Personnel M,P. = TOC

\

I

Table 4-3. Lithologic (Stratigraphic) Log of Westinghouse Test Hole No. TH34 SPLIT SAMPLE SPOON SAMPLE DEPTH INTERVAL BLOW NO. NO. (FEET) -- COUNTS

  • DESCRIPTION 1 1 1. 5 - 2.0 2-2-3 Sand, moderate yellowish brown ( 10 YR 5/4), fine-very coarse, clayey; with very fine quartz gravel, slightly micaceous, dry.

1 1 2.0 - 2.5 Sand, dark yellowish brown (10 YR 4/2), fine to coarse, clayey, with fine quartz gravel; and clay, dark brown ( 5 YR 2/2), lignitic, dry.

2 3 4.0 - 4.5 4-5-3 Clay, very sandy, light brown (5 YR 5/6), moist, silty, plastic.

2 4 4. 5 - 5. 0 Sand, moderate yellowish brown (5 YR 5/4), fine to very coarse, with quartz gravel; and clayey, poorly sorted sand, moist.

2 5 5.0 - 5.5 Sand, same as above, grad-ing downward into clay, moderate brown ( 5 YR 4/4),

slightly moist, slightly micaceous, plastic.

3 6 9.0 - 10.0 1-2-1 Silt, pale yelloiwsh brown (composite) ( 10 YR 6 /2), very mica-ceous, clayey, slightly plastic.

3 7 10.0 - 10.5 Silt, same as above.

q 8 14. 0 - 15. 5 3-3-5 Clay, moderate brown (composite) ( 5 YR 4/4), micaceous, silty, moist.

5 9 18.0 - 18.5 Silty clay, moderate yel-lowish brown ( 10 YR 5/4) grading downward with sharp break into Sand, fine to medium, micaceous, quartzose, loose, moist, permeable *

.J

continued Table 4-3 SPLIT SAMPLE SPOON SAMPLE DEPTH INTERVAL BLOW NO. NO. (FEET) COUNTS DESCRIPTION 5 10 19.0 - 19.S Sand, silty, slightly clayey, micaceous, very fine to fine, moist, permeable.

6 11 24. 0 - 25. 5 4-5-4 Sand, coarse-very coarse (composite) micaceous, with fine gravel, quartzose, silty, not much clay. Moderate to high permeability.

7 12 29.0 - 30.5 3-3-5 Clay, medium gray (N 5),

very plastic, no bedding or laminae (massive),

slightly moist. Very low permeability.

8 13 34.0 - 35.5 3-5-6 Glay, dark gray (N 3), dry, (composite) massive. Very low permea-bility.

9 14 39.0 - 40.S 4-7-11 Clay, medium gray (N 5),

(composite) massive, dry. Plastic when wet in lab. Very low permeability.

10 15 44.0 - 45.5 4-5-7 Clay I medium dark gray (composite) (N 4), dry, micaceous, mas-sive. Plastic when wet in lab. Very low permeability.

11 16 49. 0 - so. 5 20-37-48 Shale 1 medium dark gray (composite) (N4), hard, blocky with conchoidal fracture, dry, lustrous sheen. Very low permeability.

12 17 54.0 - 55.3 Shale1 same as above, (composite) except lighter color-medium gray (NS), Very low .

permeability.

13 18 59.0 - 59.S 35.:. 50,3- Clay, light gray (N7),

slightly silty, micaceous, dry, plastic when wet.

Very low permeability.

13 19 59.5-59.7 Clay, silty, light gray ( N 7) micaceous, plastic when wet.

Very low permeability.

continued Table 4-3 SPLIT SAMPLE SPOON SAMPLE DEPTH INTERVAL BLOW NO. NO. (FEET) COUNTS DESCRIPTION 14 20 64.0 - 64.S 12-25-32 Sand, very fine to fine, clayey, silty, dry. Over-all high plasticity. Low permeability.

14 21 64. 5 - 65.0 Silt, clayey, light gray (N 7) micaceous, with

.. sparse fine to medium sand

- grains, dry. Low permea-bility.

14 22 65.0 - 65.S Clay, silty, medium gray

{NS), micaceous, with some fine to medium sand grains; grading downward at 65. 2 ft to: Clay, medium light g*ray (N 6), massive, blocky.

Very low permeability.

15 23 69. 5 - 70.0 22 soIs Clay, light gray (N7),

massive, not micaceous, no silt or sand. Very low permeability.

15 24 70. 0 - 70. 4 Clay, same as above.

16 25 74.0 - 74.8 28-so/s- Clay, same as above.

17 26 79.0 - 79.5 14-23-31 Clay, same as above, slightly silty; low permeability.

17 27 79.S - 81.0 Silt, same as above light gray. Low permeability.

18 28 84.0 - 84.8 31-so,4- Claystone, medium gray, massive, blocky, dry.

Very low permeability.

Total Depth 85. O ft Summary 0 - 27 OKEFENOKEE FORMATION - PLEISTOCENE (TERRACE HYDROGEOLOGIC UNIT)

Alternating beds of poorly sorted, fine to coarse sands, silt, and clays with quartz gravels scattered throughout. Very fine to coarse quartzose sand from 18. 5 - 27. 0 ft most permeable. Screen was set at 18 - 23 ft in Well W-34

  • continued Table 4-3 27 -- 85 BLACK MINGO FORMATION ( HYDROGEOLOGIC UNIT 11}

27-49 Beds of medium-gray to dark gray, massive, micaceous, CLAY. Plastic when wet. Very low permeability. Moist in upper few feet only; dry below.

49-57 Medium to medium dark gray SHALE, dry, blocky with conchoidal fracture, massive, with lustrous sheen when broken.

57.:...65.2 Light gray, micaceous CLAY and SILTY CLAY, with low permeability; with 1. 0 ft bed of very fine to fine CLAYEY SIL TY SAND and clayey, light-gray, micaceous SILT.

Low permeability, plastic when wet, except for granular silt stratum (64.5 - 65.0 ft).

65.2-76 Light to medium light gray, non-micaceous, massive CLAY, dry in borehole, plastic when wet in lab. Essentially no permeability.

76-83 Light-gray, massive, non-micaceous CLAY and massive slightly SILTY CLAY, dry, low permeability. Plastic when wet in lab.

83-85 Medium gray, massive, dry CLAYSTONE, blocky, Very J*ow permeability.

NOTES

1. Color designation Standard: Geol. Soc. of America, Rock-Color Chart, 1975.
2. Permeability (hydraulic conductivity) descriptions are qualitative estimates from visual field observation of drill cuttings and laboratory classification of split-spoon samples.
3. Standard Blow Count is number of blows required to drive 1 3/8 in I.D., 2 - in O.D. Split Barrel Sampler 6. inc:..hes with 140 Pound Hammer* Falling 30 inches.

Field and Lab Analyses by B. C. Spigner Senior Hydrogeologist

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