final aquifer pump test report - records collections
TRANSCRIPT
33)05
FINALAQUIFER PUMP TEST REPORT
DRAKE CHEMICAL SUPERFUND SITELOCK HAVEN, PENNSYLVANIA
VOLUME I
CONTRACT NUMBERDACW45-90-C-0117
APRIL 1992
GANNETT FLEMING, INC.BALTIMORE, MARYLAND
AR303775
Gannett Fleming GANNETT FLEMING, INC.Suite 200
ENGINEERS AND PLANNERSBaltimore, MO 21210Fax; (301)433-6520Offlca: (301) 433-5832
April 24, 1992
Craig Peoneil, Project ManagerEnvironmental BranchU.S. Army Corps of Engineers, Omaha DistrictCEMRO-ED-EC215 N. 17th StreetOmaha, NE 68102-4978
RE: Drake Chemical Superrund SiteContract No. DACW 4S-90-C0117Final Aquifer Pump Test Report
Dear Mr. Peanell:
Gannett Fleming is pleased to submit three copies, Hieigdtny one unbound copy, of the FinalAquifer Pump Test Report for the Drake Chemical Superfdnd Site, Lock Haven, Pennsylvania. Fivecopies of the final report will be delivered separately to Mr. Roy Schrock of EPA. Additional copies ofthe report, if needed, will be available to be mailed to you next week.
If you have any questions about this submittal, please contact me or Mark Mummert, ourAssistant Project Manager and the principal author of this report
Sincerely,
GANNETT FLEMING, INC.
Chen-yu Yen, PhProject Manager
CYYrkai
Enclosures
cc: Roy Schrock (EPA)David SheridanMark Mummert
GF: 27337.080
A Tradition of Excellence Since 1915SR303776
OUTLINEAQUIFER PUMP TEST REPORT
DRAFT
TEXT
Page
1.0 INTRODUCTION ...:................................... 1-1
1.1 Site Background and History ............................ 1-11.2 Hydrogeologic Setting Characterization ...................... 1-3
2.0 REPORT OBJECTIVE ................................... .2-1
3.0 POTENTIOMETRIC SURFACE MAPPING AND TREND DATA ......... 3-1
3.1 Potentiometric Surface Mapping .......................... 3-13.2 Trend Data .....................................
4.0 DRILLING AND WELL INSTALLATION ....................... 4-1
4.1 Introduction ...................................... .4-14.2 Drilling and Sampling ................................ 4-34.3 Well Construction ................................... 4-10
4.3.1 monitoring wells .............................. 4-104.3.2 test well ................................... 4-1-1
4.4 Well Development .................................. 4-124.4.1 monitoring wells .............................. 4-124.4.2 test wett ................................... 4-144.4.3 test well redevelopment .......................... 4-14
4.5 Surveying ....................................... 4-16
5.0 AQUIFER TESTING .................................... .5-1
5.1 fit-situ Hydraulic Conductivity Testing ...................... 5-15.2 Step-Drawdown Test ................................ .5-35.3 72-Hour Pump Test ................................. .5-5
5.3.1 pump test setup ................................ 5-55.3.2 data validation ................................ .5-65.3.3 data correction ................................ 5-65.3.4 data analysis ................................. .5-9
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___ OUTLINEAQUIFER PUMP TEST REPORT
DRAFT(continued)
Page
5.4 Recovery Test .........'........................... 5-155.5 Wastewater Treatment Plant Dewatering .................... 5-15
6.0 MODELING OBJECTIVE .................................. 6-1
7.0 MODELING APPROACH .................................. .7-1
7.1 Identification of Models Being Used (MODFLOW & MODPATH) ..... 7-17.2 Conceptual Model .................................. .7-17.3 Previous SWIFT MODEL .............................. 7-7
8.0 GROUNDWATER FLOW MODELING ......................... 8-1
8.1 Model Set-up ..................................... .8-18.2 Model Calibration .................................. .8-68.3 Extraction Well Placement ............................. 8-118.4 Sensitivity Analysis ................................. 8-16
9.0 SUMMARY OF FINDINGS ................................. 9-1
9.1 Potentiometric Surface Mapping .......................... 9-19.2 Drilling and Well Installation ............................ 9-29.3 Aquifer Testing ................................... .9-39.4 Groundwater Flow Model .............................. 9-4
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LIST OF PLATES
Plate Page1
3-1 Potentiometric Surface - October 11, 1990 ..........................
3-2 Potentiometric Surface - November 14, 1990 .........................
3-3 Potentiometric Surface - December 11, 1990 .........................
3-4 Potentiometric Surface - March 14, 1991 ...........................
3-5 Potentiometric Surface - July 9, 1991 .............................
3-6 Potentiometric Surface - August 26, 1991 ...........................
3-7 Potentiometric Surface - October 17, 1991 ..........................
3-8 Bottom of Sand and Gravel Layer Contour Map .......................
3-9 Potentiometric Surface - August 29, 1991 ...........................
1 Plates are located at the rear of mis report
in
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LIST OF FIGURES
Figure Page
1-1 Location Map ............ f ............................. 1-2
1-2 General Arrangement for Groundwater Remediation .................. 1-4
3-1 Trend Data Obtained from MW-M125 .......................... 3-11
4-1 Test Well Location Map ................................... 4-2
4-2 South-North Cross Section A-A' .............................. 4-6
4-3 West-East Cross Section B-B' ................................ 4-7
5-1 Hydrograph of Trend Data - August 23-26, 1991 .................... 5-8
5-2 Pump Test Drawdown Contour Plot ........................... 5-11
7-1 Long-Term Average Water Levels ............................. 7-4
7-2 Hydraulic Conductivity Values Developed from Kriging ................ 7-8
8-1 Grid Area and Boundary Conditions ............................ 8-2
8-2 Recharge Values ........................................ 8-5
8-3 MODFLOW Simulated Groundwater Levels ....................... 8-9
8-4 Flowlines for 1 Well Extraction System ......................... 8-13
8-5 Flowlines for 5 Well Extraction System - Southwest to Northeast Configuration 8-14
8-6 Flowlines for 5 Well Extraction System - Southeast to Northwest Configuration 8-15
IV
aR303780
LIST OF TABLES
Easfi3-1 Well Construction Details .................................. .3-2
3-2 Summary of Water Level Measurements .......................... 3-7
4-1 Summary of Soils Analyses .................................. 4-5
5-1 Summary of Slug Testing Results .............................. 5-2
5-2 Summary of Step Testing Results .............................. 5-4
5-3 Observed Drawdown During Pump Test of TW-1 ................... 5-10
5-4 Summary of Pump Testing Results ............................ 5-13
5-5 Summary of Results Based on Wastewater Treatment Plant Dewatering ...... 5-16
7-1 Long-Term Average Groundwater Levels ......................... 7-3
7-2 Measured Values of Hydraulic Conductivity ....................... 7-5
8-1 Bottom of Layer Elevations .................................. 8-4
8-2 Calibration Results ....................................... 8-7
8-3 Hydraulic Conductivity (feet/day) ............................. 8-10
8-4 Sensitivity of Predicted Water Level Elevations .................... 8-18
ftR30378l
: . APPENDICES
A. BORING AND WELL CONSTRUCTION/DEVELOPMENT LOGS
A. 1 New Drake Wells Installed by Gannett Fleming, Inc.A.2 Drake Wells Installed During Previous InvestigationsA.3 American Color & Chemical Corp. WellsA.4 TTammgntiiU Wells
B. SEVEN ROUNDS OF GROUNDWATER LEVEL MEASUREMENTS
C. TREND DATA
D. CONFIRMATION NOTICES
E. LABORATORY ANALYTICAL RESULTS
E.1 Hydrant WaterE.2 Soil SamplesE.3 Test Well Total Solids
F. SURVEY NOTES
G. SLUG TESTING DATA
H. STEP-DRAWDOWN TEST DATA
H.1 HydrographsH.2 Data Logger DataH.3 Manual MeasurementsH.4 Well Efficiency Calculation
I. PUMP TEST AND RECOVERY TEST DATA
LI HydrographsL2 Data Logger DataL3 Manual MeasurementsL4 Computer Program OutputL5 Calculations
J. LONG-TERM AVERAGE WATER LEVEL DATA
K. MODFLOW INPUT AND OUTPUT FILES
K.1 Calibration RunK.2 Example Runs for Extraction Well Placement
L. RESPONSES TO COMMENTS ON THE DRAFT REPORT
vi
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AR3Q3783
1.0 INTRODUCTION
This report presents the results of aquifer pump testing and groundwater flow modelingconducted for the U.S. Army Corps of Engineers (USAGE), Omaha District of the DrakeChemical Site located in Lock Haven, Pennsylvania. This report was prepared by GannettFleming, Inc. in response to Contract Number DACW45-90-C-0117. The report has beenprepared in accordance with the Scope of Services dated July 2, 1990. It summarizes datarequired for the design of a groundwater extraction system.
1.1 Site Background and History
The Drake Chemical Site is located south of the City of Lock Haven in Clinton County,Pennsylvania. A pictorial view of the site and adjacent areas is presented in Figure 1-1.Adjacent to the Drake Chemical property is a large apartment complex, a large shopping center,a municipal park, an elementary school, several churches, the American Color and ChemicalCompany, the Gorham property, and. the Hammermill Paper Company industrial facility. TheBald Eagle Creek runs less than half a mile south of the site and the West Branch of theSusquehanna River is located approximately three-fourths of a mile north of the site.
Drake Chemical, Inc. (Drake) purchased the site in 1962 for manufacturing specialtyintermediate chemicals for the production of dyes, pharmaceutical, cosmetics, herbicides, andpesticides. The organic compound 2,3,6 trichlorophenyl acetic acid (also known as the herbicideFenac*) was manufactured at the plant and is a major site contaminant. Activities at this sitebefore 1962 are unclear, however, there are indications that the site may have been used forchemical production as early as 1951. The site has been inactive since 1982.
Drake was cited several times between 1973 and 1982 for violations of environmental, healthand safety regulations. Emergency cleanup activities were initiated at the site in 1982 by EPAafter Drake failed to respond to a request for voluntary cleanup. During the emergency cleanup,
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sludge and liquids from process drums and storage tanks were removed from the site and a fencewas erected around the site. Starting in 1983, the EPA conducted three phases of Superfundremedial investigation/feasibility studies (RI/FS)/'*The Phase I RI/FS, completed in 1984,focused on a leachate stream running offsite towards Bald Eagle Creek. A Record of Decision(ROD) was signed to remedy the leachate stream by covering the upper reaches of the streamwith natural soils and a clay cap, ar»4 installing a conduit drain from the site to Bald Fagl<»Creek. The Phase n RI/FS, which addressed onsite buildings, surface features, soil, sludgesand groundwater, was completed in 1986. The Phase H ROD directed the demolition ofbuildings and tanks followed by disposal in an offsite landfill. There, was no provision forremediation of the soil, sludges, and groundwater in this phase. The Phase IH RI/FS, completedin 1988, was initiate to define the extent of groundwater contamination. In 1988, a ROD wassigned after the completion of the Phase HI RI/FS. The ROD addressed the remedial action onthe contaminated sludge/soils/sediments and groundwater at the site. The remedial action forthe groundwater decontamination includes pumping and treating the contaminated groundwaterto an acceptable level for discharge.
As shown in Figure 1-2, the Drake Chemical Site is divided into three zones. Zone I includesthe property of the now-demolished Drake Chemical plant Zone n is between the site and StateRoute 220, and Zone ffl is between State Route 220 and Bald Eagle Creek.
1.2 Hydrogeologk Setting Characterization
Lock Haven is situated in a broad northeast-southwest trending valley underlain by Devonianshales and limestones. The valley is bounded on the north by the Allegheny Front, which is thesouthern scarp of the gently folded Appalachian Plateaus physiographic province, and on thesouth by Bald Eagle Mountain, which is the northernmost ridge of the intensely folded Valleyand Ridge physiographic province.
North of Lock Haven, the West Branch of the Susquehanna River descends the Allegheny Frontand bends sharply to the northeast to continue on to Williamsport. South of Lock Haven, Bald
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Eagle Creek flows northeastward along the base of Bald Eagle Mountain. Bald Eagle Creek-- ;*«
empties into the West Branch of the Susquehanna River on the east side of Lock Haven. Thus,the City of Lock Haven, including the Drake Chemical Site, lies in an northeastward pointing,triangular flood plain delineated by the West Branch of the Susquehanna River on the north,Bald Eagle Creek on the south, and uplands on the west
The Quaternary alluvium which underlies the site and adjacent areas consists of clay to sandyclay and silt floodplain deposits. In many locations, the flood plain has been filled with cinders,gravel, silty sands and mixtures of various other materials. The surficial materials coarsen ingrain size with depth to sand and gravel stream channel deposits, then finally to medium tocoarse grained sands mixed with gravel-sized sandstone fragments. The underlying bedrockconsists of shale and limestones of the Marcellus, Old Port, and Keyser Formations.
Groundwater flows generally east and south from the Drake Chemical Site toward Bald EagleCreek. Variations within the alluvial materials affect the flow rates and directions. However,elevation of bedrock surface has been repeatedly identified as the major factor affectinggroundwater flow in the area (Environmental Science and Engineering (ESE) and ChemicalWaste Management (CWM), 1985; Environmental Research and Technology, Inc. (ERT), 1986;and Halliburton NUS, 1988). Bedrock is shallow on the southern portion of the American Colorand Chemical Site and slopes sharply to the north and east Groundwater flow generallyparallels this bedrock contour.
The Phase HI RI has identified a buried channel that appears to be an erosional feature withinthe limestone bedrock (Plate 3-8). The channel has a depth of approximately 100 to 110 feet,which is 50-60 feet deeper than the top of the bedrock. The channel is oriented in an east-westdirection roughly.paralleling Bald Fagte Creek. It is filled with brown, fine grained, well sortedsand with some silt and gravel dispersed throughout The Phase in RI concluded that thechannel does not affect or influence groundwater flow directions or contaminant migration.
1-5
AR303788
AR303789
2.0 REPORT OBJECTIVE
The purpose of this report is to summarize data required for the design of a groundwaterextraction system. Methods and results from the following activities are included:
• Potentiometric Surface Mapping - Seven rounds of groundwater levelmeasurements were taken to determine groundwater fluctuations prior to andfollowing the aquifer pump test. These results are summarized in Chapter 3.
• Drilling and Well Installation - One test well and three monitoring wells wereinstalled for the aquifer pump test The methods of drilling, well constructionand well development for these wells are summarized in Chapter 4.
• Aquifer Testing - In-situ hydraulic conductivity testing, step-drawdown testing,and pump testing were conducted to aid in establishing aquifer hydraulicparameters necessary for the groundwater modeling and the design of agroundwater extraction system. The methods and results of these work items aredescribed in Chapter 5.
• Groundwater Flow Model - A groundwater flow model was developed for use inthe design of a groundwater extraction system. Documentation of thedevelopment of this model is contained in Chapters 6 through 8.
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&R3Q379G
SR3Q379
3.0 POTENTIOMETRIC SURFACE MAPPING AND TREND DATA
3.1 Potentiometric Surface Mapping
Gannett Fleming collected seven rounds of groundwater level measurements from monitoringwells at the Drake Chemical Site, neighboring properties, and various locations in Lock Haven.Wells included in the groundwater monitoring program were selected on the basis of theirscreened interval and geographical location. Construction details of the selected wells are listedin Table 3-1. Well construction and/or boring lop are presented in Appendix A. Well locationsare shown on Plate 3-1. Gannett Fleming also monitored the level of Bald Eagle Creek duringeach round of groundwater level measurements by means of a staff gage on the west abutmentof the Castanea bridge.
Gannett Fleming collected five rounds of measurements before the 72-hour pump test, one roundof measurements immediately prior to the test, and one round after the test Monitoring wellMW-M9 was added to the program after the second round of measurements. The new test well(TW-1), three new monitoring wells (OW-1, OW-2, and OW-3), and six Hammerraillmonitoring wells1 were added after the third round of measurements. Monitoring well MW-M9and the Hammermill wells were added in order to provide more data to the west of the site.Monitoring well MW-M21 was physically removed during excavation for expansion of the Cityof Lock Haven wastewater treatment plant The bottom elevation of monitoring well MW-M21,524 feet, was six feet higher than the bottom of the excavation. Therefore no water levelmeasurements for MW-M21 were made after the fourth round of the monitoring program.
1 Hammermill monitoring wells MW-H1, MW-H4 and MW-H5 are located west of thearea covered by the Plates as shown on the aeration basin sketch in Appendix A.4.
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The groundwater level measurements from each round are presented in Appendix B, and theresults are summarized in Table 3-2. The period of measurements extends from October 1990to October 1991. Groundwater levels generally rose from October 1990 through March 1991as a result of recharge from precipitation and snow melt and reduced evapotranspiration.Groundwater levels generally declined from March 1991 through October 1991 as a result ofincreased evapotranspiration, drought, and dewatering at the City of Lock Haven wastewatertreatment plant
Potentiometric surface maps based on the seven rounds of measurements are presented inPlates 3-1 through 3-7. Not all groundwater level measurements were used to plot thepotentiometric surface contours. The plots were prepared based on groundwater levelmeasurements considered most representative of conditions in the lower sand and gravel layerof the overburden. This particular layer was of greatest interest as it constitutes the bulk of thesaturated overburden in Zones I and n where the Phase m Record of Decision indicatesgroundwater extraction wells are to be located. Although some wells screened in the upper unitwere monitored, most notably the wells located within the fenced area of Zone I (i.e.,monitoring wells MW-MS, MW-M6, MW-M7, and MW-M108), data from these wells were notused to plot potentiometric surfaces because similar shallow wells were not monitored at theAmerican Color & Chemical Corporation plant To plot the potentiometric surface using datafrom shallow wells only on the Drake site would produce a skewed depiction of groundwaterflow.
The potentiometric surface maps indicate groundwater in the sand and gravel layer flowsgenerally in eastern and southeastern directions from Zone I toward Zone n and the Bald FagleCreek. The hydraulic gradient across the site is relatively gentle (approximately 0.3%). Thechange in potentiometric surface elevation from MW-M9 to MW-M119, a distance ofapproximately 4000 feet, is less man 12 feet The gradient is steeper in the vicinity ofmonitoring well MW-8 in the southwest comer of the American Color and Chemical plant,where bedrock is closer to ground surface and slopes more sharply than bedrock in other areas.The potentiometric surface contour maps reflect to some extent the bottom of sand and gravel
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TABLE 3-2SUMMARY OF WATER LEVEL MEASUREMENTS
DRAKE CHEMICAL SITE
ROUND I11-Oct-90
ROUND II14-NOV-90
ROUND III11-DOC-90
ROUND IV14-M3T-91
ROUND V09-JU1-91
ROUND VI26-Aug-91
ROUND VII07-Oct-91
WELL ID Bev. Bav. Change Bav. Change Bev. Change Bav. Change Bav. Change Sev. Change-0115s-
OW-1 545.21 541.82 -3.39 540.34 -1.48 540.29 -0.05; 540.49: 540.38 -0.11
OW-3 544.88 541.71 -3.17 540.27 -1.44 540.17 -0.10-0.30
MW-M2 545.56 545.98 0.42 546.74 -0.24 545.98 0.24 544.51 -1.47 543.63 -0.88 543.24 -0.39
MW-M4 543.20 544.60 1.40 544.33 -0.27 544.95 0.62 542.09 -2.36 540.77 -1.32 540.59 -0.18
MW-M6 547.85 549.29 1.44 549.02 -0.27 549.57 0.55 546.42 -3.15 546.29 -1.13 545.42 0.1355B29: 552.87 S43i2S:
MW-M9 552.53 552.82 0.29 551.12 -1.70 549.94 -1.18 549.90 -0.04533.2* 0.7*
MW-M13 542.70 544.62 1.92 544.20 -0.42 544.80 a 60 541.45 -3.35 540.38 -1.07 540.61 0.23542475 -&Q5:
541.62 543.29 1.67 54Z97 -0.32 0.63 540.35 539.03 -1.32 539.27 0.24ismm
543.38 544.59 1.21 544.36 -0.23 544.38 0.52-0.70
MW-M102 545.73 546.28 0.55 546.30 0.02 546.65 0.35 545.24 -1.41 543.98 -1.26 543.28 -0.7054* 3S .54-t.SZ- -0.80
MW-M104 545.27 545.89 0.62 545.69 -0.20 545.96 0.27 544.43 -1.53 542.68 -1.75 541.87 -0.81-4.98 540.45-
MW-M109 54Z65 544.32 1.67 543.96 -0.36 544.60 0.64 540.94 -3.66 539.67 -1.27 539.95 0.28540.2*: 540i70;
MW-M113 540.77 54Z22 1.45 541.55 -0.67 541.92 0.37 539.92 -2.00 538.98 -0.94 540.22 1.24V.02
MW-M117 540.99 542.68 1.6 542,19 -0.49 542.65 0.46 539.95 -2.70 S3&97 -0.98 539.68 0.7153S.30; 0,93:
MW-M122 542.66 544.31 1.6 544.01 -0.30 544.75 0.74 538.93 -5.82 536.33 -2.60 536.43 0.10MW-M12* msw 543.65 52 63 527.9S -0,05.-MW-M125 543.31 544.79 1.48 544.51 -0.28 545.11 0.60 541.72 -3.39 540.31 -1.41 540.20 -0.11
-0.09*MW-2S 545.91 546.88 0.97 546.74 -0.14 547.08 0.34 544.35 -Z23 543.90 -0.95 543.73 -0.17
546.50 -0.29;MW-5 550.58 551.37 0.79 551.34 -0.03 5S1.38 0.04 549.32 -2.06 548.59 -0.73 548.56 -0.03
549,8* 545.66- 5*7.90 aooMW-7 550.06 550.83 0.77 551.01 0.18 550.83 -0.18 549.03 -1.80 547.87 -1.16 548.13 0.26£$ 556.50 556.34 5S5.lt -0.03'4 547.56 549.19 1.63 548.70 -0.49 549.57 0.87 I 546.09 -3.48 546.03 -0.06 545.01 -1.02
3"7 &R303798
TABLE 3-2 (Continued)
SUMMARY OF WATER LEVEL MEASUREMENTSDRAKE CHEMICAL SITE .
WELL IDMW ISISMW-20'&*£&£*'—•'MW-25&&&&$•..'* ":iMW-HCTRLMWf-H*MW-H2'MV&S3K ' "MW-H4KfV&filSf': ::Staff Gage
ROUND 111-Oct-90
Bev.r& siiii
545.63-•••"•|llii
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ROUND II14-NOV-90
Bev.HeM545.83545.63:550.44itlilt
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ROUND III11 -Dec-90
Bev.iliiii545.68mum550.56iHiiii-|;:.v.x. .:.£:«.-.:•
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ROUND IV14-Mar-91Q uow*
i *i3*f545.865*5.0*550.69HW548.20iH546.805*5.40541.405*£BQ540.19
Change
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ROUND V09-Jul-91
Bev.$!ii&544.655*4.68548.475*4.3*544.39?9@fc&544.475*2i8*;;540.90|S*li3Sfe539.34
Change••;*2i£
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-2.22;|, '**$&&
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-2.33:" '3&»
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-0.85
ROUND VI26-Aug-91
Bev.544s4*543.99f'544l30'547.51;i:S»*25li
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-; «•'537.89
Change*&#*-0.66
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ROUND VII07-Oct-91
Bev.5*4.02543.67•543,80'547.52
; 543,9$544.22544,03543.97;'s*2.6r541.58•5»2>02539.89
Change-4J.39-rO.32-aso0.01-0.2ft------2.00
SUMMARY
#Up#Even#Down
--
•Maximum IncreaseMinimum IncreaseMinimum DeclineMaximum Decline
AverageChange
-
3901
Z340.01
-0.32-0.32
1.09
5035
0.180.02
-0.02-0.67
-0.26
3804
1.200.04
-0.02-0.77
a 38
00
51——
-0.50-15.02
-2.67
0045——
• -0.06-2.60
-1.07
— i27
1.240.00000
-1.02
6.03
NOTE Bevation in feet above mean sea level.
>
3-8 AR303799
layer contour, map presented in Plate 3-8. Gannett Fleming prepared Plate 3-8 based on datapresented in previous RI reports on the Drake Chemical site and data on the AC&C site obtainedfrom the Pennsylvania Department of Environmental Resources in WHliamsport.
Potentiometric surface contours are relatively more closely spaced at the American Color andChemical plant and the former Drake Chemical plant in Zone I where the «"iri and gravel layeris relatively less thick and less continuous as a result of excavation and placement of finer-grained, less conductive fill material2. The phreatic (saturated) zone occurs in both thefiner-grained fill and the underlying, coarser sand and gravel layer. Potentiometric surfacecontours are more widely spaced in Zones n and HI where bedrock is relatively deeper and thesand and gravel layer is thicker and more continuous. The phreatic zone generally occursentirely within the sand and gravel layer and does not encroach into the overlying finer-grainedfill and flood plain deposits.
The potentiometric surface maps of the last three rounds of water level measurements reveal theimpact of the dewatering operation at the Lock Haven wastewater treatment plant to thenortheast of the site. The Quandel Group, Lie. has been performing the dewatering to permitexcavation and construction of a pumping station as part of the Bald Eagle Creek dike project.Massive dewatering by means of a well point system began June 19,1991. The dewatering ratehas been approximately 350 gallons per minute (GPM)3, and it is anticipated that dewateringwill continue through December 1991. Within the excavation, an area 40.7 feet by 34.7 feet
2 Excavations included the Bald Eagle Cross Cut Canal between the Drake and AmericanColor and Chemical sites, a canal boat basin on the Drake site, building foundations,underground storage tanks, wastewater lagoons, and sludge disposal trenches and pits.
3 October 10, 1991 telephone conversation with Mr. Ken Koprinnikar, wastewatertreatment plant supervisor.
3-9
flR3038QO
was lined with sheet piling and dewatered to an elevation of approximately 518 feet*. Theexcavation activity affected two wells. Monitoring well MW-M21 was completely removed asthe bottom of the excavation extended below the bottom elevation of the well. Monitoring wellMW-M124 was left in the sloping sidewall of the excavation approximately 10 feet outside thesheet piling; its riser pipe was cut off at an elevation of 545.195, and a temporary cover wasplaced over the well. The water level in MW-M124 was measured during the final three roundsof water level measurements and during the pump test. Because of its removal, monitoring wellMW-M21 was not included in the final three rounds of water level measurements.
The dewatering activity affected groundwater levels over a large area; however, it resulted inless than a foot of drawdown in the area around the pump test well TW-1. The water level inwell MW-M125, which is located approximately 2,100 feet from the dewatering operation and162 feet from the test well (TW-1), was continuously monitored from January to August 1991(see Figure 3-1). The water table decline observed at MW-M125 from April to August wasapproximately 5 feet The seasonal water table decline began in late April, while the massivedewatering operation did not begin until June 19. The hydrograph depicted in Figure 3-1 showsan apparent increase in the water table's rate of decline when the dewatering operation began.Comparison of the hydrographs of wells not affected by the dewatering with the hydrograph ofMW-M125 suggests that only approximately 0.5 feet of drawdown appears attributable to thedewatering operation. The impact of the dewatering was significantly greater at monitoringwells closer to the treatment plant, such as MW-M122 and MW-M124 where the estimateddrawdown was 4.9 and 12.1 feet, respectively. The hydraulic conductivity and transmissivityin Section 5.5.
4 October 10, 1991 telephone conversation with Mr. George Rushanan, Jr., QuandelGroup, Inc. Project Superintendent
5 The new top of riser pipe elevation was surveyed by the Quandel Group, Inc.
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3R30380I
(S3HON1) NOLLVlIdlOiHd
CM
OGC
ft QLU
enOILUGC
(I33d) NOI1VA313
3"u SR303802
The presence of a recharge mound in Zone I is indicated by the relatively shallow water levelsmeasured atMW-M5, MW-M6, and MW-M7, and MW-M108. These wells, which are the onlyremaining wells within the fenced area of Zone I, are screened in a silty fine sand layer abovethe sand and gravel layer. Groundwater level measurements from these wells were not used toplot the potentiometric surface contours, so the mounding in Zone I does not appear in thepotentiometric surface plots (Plates 3-1 through 3-7). Similar mounding has been reported inthe finer materials overlying the sand and gravel layer at the American Color and Chemical plantto the west of Zone I (Environmental Research and Technology, Inc., 1986). Shallow moundingin Zone I will complicate excavation and incineration of contaminated sludge, soils andsediments as called for in the Phase UI ROD (U.S. Environmental Protection Agency, 1988).
3.2 TREND DATA
Gannett Fleming installed a pressure transducer and data logger at monitoring well MW-M125to collect long-term trend data prior to the pump test The data logger recorded a groundwaterlevel measurement every six hours from January 14 to August 26, 1991. Monitoring wellMW-M125 is located approximately 150 feet from the test well and screened in the buriedchannel (Plate 3-8). Long-term trend data are presented in Appendix C, and a hydrograph basedon these data is presented in Figure 3-1. Precipitation data obtained from the NOAA NationalClimatic Data Center and the City of Lock Haven wastewater treatment plant are also plottedin Figure 3-1.
The static water level generally ranges from approximately 544 to 545 feet from January 14through April 27, 1991. During this trend, the graph of the water level in the well correlateswell with the trend of the precipitation data. The data suggest rain water and snow meltinfiltrate fairly rapidly to recharge the aquifer, and the quantity of precipitation is adequate tomaintain the water level within a relatively narrow range.
3-12
8R303803
The hydrograph shows the water level in MW-M125 steadily declined from approximately545 feet to 540.5 feet during the period of April 27 to August 8, 1991. The decline is mostprecipitous from mid-June to mid-July. It is evident from the hyetograph that rainfall eventsoccurred less frequently during June and July. According to data compiled by the NationalOceanic and Atmospheric Administration (1991), rainfall in Lock Haven totalled 1.89 inches inMay, 1.59 inches in June, and 1.20 inches in July. The Central Mountain Division, whichincludes Clinton, Centre, Qearfield, E1V, and Cameron Counties, received only approximatelyhalf its normal rainfall during these months. On July 24,1991, the Governor declared a droughtemergency in 39 central Pennsylvania counties including Clinton County. Observations factoredinto the declaration of a drought emergency include groundwater levels, streamflows, soilmoisture, and precipitation deficits.6
The data suggest that quantities of precipitation were not adequate to recharge the water tableduring the drought The lack of response of the water level in the well to specific precipitationevents suggests that less precipitation was infiltrating to the water table. The reduced infiltrationmay be a result of increased evapotranspiration, increased storage in the growing vadose(unsaturated) zone, and/or increased surface runoff because of more intense rainfall events. Themassive dewatering operation begun June 19 at the wastewater treatment plant 2,100 feet awaymay also have contributed to the decline of the water level hi MW-M125. From August 8 toAugust 26, the hydrograph began to flatten as the water table approached its seasonal low.
6 November 12, 1991 telephone conversation with Mr. Mike Packard of the PennsylvaniaDepartment of Environmental Resources, Water Resources Management Bureau.
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AR30380U
AR303805
4.0 WELL DRILLING, INSTALLATION AND DEVELOPMENT
4.1 Introduction
This chapter describes the drilling, installation, and development of the test well (TW-1) andthree new monitoring wells (OW-1, OW-2, and OW-3). These activities were performed inaccordance with the USAGE Scope of Services dated July 2, 1990, the Final Quality Controland Sampling Plan (QCSP) dated December 1990, and Confirmation Notices presented inAppendix D. Gannett Fleming and its subcontractor Pennsylvania Drilling Company, Inc.performed most of these activities during the period of December 17, 1990 toFebruary 13, 1991.
The new wells were installed in order to conduct a 72-hour constant rate pumping test in Zone Hof the site. The locations of the test well and three new monitoring wells are shown inFigure 4-1. The test well was intentionally located in a buried channel in the bedrock in orderto maximize available drawdown during the 72-hour constant rate pump test Halliburton NUSconfirmed the existence of this buried channel during the Phase HI remedial investigation(Halliburton NUS, 1988). The channel trends in an east-west direction roughly parallelingnearby Bald Eagle Creek.
Water used during these activities was obtained from the City of Lock Haven water hydrantadjacent to the Zone I gate. Gannett Fleming sampled the water from this hydrant prior to itsuse. Gannett Fleming Environmental Laboratory analyzed the sample for volatile organics,semi-volatile organics, pesticides and PCBs, total and dissolved metals, cyanide, chlorine, anda select list of secondary drinking water parameters. Results of hydrant water analyses arepresented in Appendix E.1. The laboratory results proved the hydrant to be an acceptablesource for drilling operations.
Hydrant water was used to steam clean the drill rig, well construction materials, and alldownhole tools and equipment used to drill, install, and develop the wells. Equipment was
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AR303806
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DRAKE CHEMICAL, INC. SITEMW-I8B
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TEST WELL LOCATION MAPLEGEND
• AM. COLOR & CHEMICAL MONITOR WELLQannatt Flamlna Q HAMMERMILL MONITOR WELL
AM, fummra 8 3 DRAKE CHEMICAL MONITOR WELL® DRAKE CHEMICAL WELL
SCALE (INSTALLED BY GANNETT FLEMING)if0' MW"M"7 INCLUDED IN GANNETT FLEMING
GROUNDWATER MONITORING PROGRAM
4"2 SR303807
steam cleaned at the decontamination pad in Zone I. Hydrant water was also used to combatrunning sands encountered during well drilling and installation and to jet monitoring well OW-1during well development Volumes of water removed during well development exceededvolumes of water added during well 4rilM"g, installation, and development
Cuttings generated during drilling were contained and transported to Zone I where they werespread out in low-lying areas. Wastewater generated during well drilling and development wascontained and discharged into the unlined lagoon in Zone L
Well drilling, installation, and development was performed in modified Level D and Level Cpersonal protective equipment as required by the Final Safety, Health, and Emergency ResponsePlan (SHERP) dated December 1990 governing these activities.
4.2 DRILLING AND SAMPLING
An Acker AD-82 drill rig was used to drill the test well and three new monitoring wells. Thedriller used a 4-inch I.D. hollow stem auger to permit collection of soil samples as he advancedthe borings. The monitoring wells were installed through the 4-inch I.D. auger. The drillerused an 8-inch I.D. hollow stem auger and an 8-inch solid stem auger to ream the test wellboring prior to installation of the test well through the hollow stem auger.
Soil samples were collected with a split-barrel sampler in accordance with ASTM D 1586-84(Standard Method for Penetration Test and Split-Barrel Sampling of Soils). Samples werecollected continuously for the first 10 feet and then at 5-foot intervals to the end of the boring.The project geologist screened the soil samples with a photo-ionization detector (PID) calibratedto 100 ppm isobutylene and visually classified the samples in accordance with ASTM D 2488-84(Standard Practice for Description and Identification of Soils (Visual-Manual Procedure)).Boring logs are presented in Appendix A.l.
4-3
SR303808
Soil samples from the screened interval of the test well and three new monitoring wells wereanalyzed by Gannett Fleming's Geotechnical Laboratory for grain size distribution in accordancewith ASTM D 421 and 422 (Standard Practice for Dry Preparation of Soil Samples for Particle-Size Analysis and Determination of Soil Constants and Standard Method for Particle-SizeAnalysis of Soils), Atterberg Limits in accordance with ASTM D 4318 (Standard Test Methodfor Liquid Limit, Plastic Limit, and Plasticity Index of Soils), and moisture content in accordancewith ASTM D 2216 (Standard Practice for Wet Preparation of Soil Samples for Particle-SizeAnalysis and Determination of Soil Constants). Visually similar samples were composited.Additional samples corresponding to the screened interval of the test well were analyzed frommonitoring well OW-1 in order to select the test well screen slot size and filter pack material.Analytical results are summariTed in Table 4-1, and complete laboratory reports are presentedin Appendix E.2.
Cross sections based on the four new borings and borings from previous investigations areshown in Figures 4-2 and 4-3. Figure 4-2 is a south-north cross section (A-A') across theburied channel, and Figure 4-3 is an west-east cross section (B-B') along the buried channel.
The borings penetrated four basic soil units: An uppermost layer of fill and floodplain deposits(ML), an alluvial layer of silty sand and gravel (sandstone fragments (GM, ML, SW-SM, SP-SM, SM), a more uniform alluvial layer of silty sand (SM), and a gray silty clayey fine sandlayer (SC-SM).
The uppermost unit is a moist brown silt layer extending from the surface to a depth ofapproximately 9 feet Some black slag is present in the upper foot of unit 1. The fine sandcomponent of the brown silt layer generally increases with depth. This layer appears to berecent fill material and flood plain deposits. No PID measurements above background levelswere recorded on soil samples collected from the brown silt layer at borings OW-1 and OW-3.PID measurements were slightly above background on samples collected from this layer at TW-1and OW-2. No odors were noted.
4-4
AR303809
TABLE 4-1
SUMMARY OP SOILS ANALYSESDRAKE CHEMICAL SITE
Well IDTW-1
OW-1
OW-2
OW-3
SampleDepth***r— •Range1
15-22
25-2730-31.3
35-41.4
42.4-81.4
15-22
25-41
41-50.550.5-5255-56.560-72.0
30-32
35-36
41-41.8
35-37
40-41J
TTi ff f Am] ffof flMtyiand Description
CM
MLSW-SM
SP-SM
SM
SM
SM
SMSMSMSM
SM
SM
SC-SM
OC-GM
SM
Sitty gravelw/aandSatw/sandWefl gradedsandw/nk,gravelPoorly
w/tflt,gravelSaty sand
Sitty sandw/gnveltitty sandw/gravelsaty sandtitty sandsaty sandsitty sand
Sflty Sandw/gnvelSitty landw/gravelSitty clayeysand
Saty-clayeygravelw/MndSaty sand
X Gravel
Coane
33
.6
15
-
13
12
--3-
6
6
"
21
-
Fine
14
121
30
13
27
22
4-115
36
20
14
31
-
*Sand
Coane
5
-6 .
8
4
8
6
2-43
8
7
2
15
3
Medium
4
113
13
9
9
11
815189
8
10
8
9
7
Fine
25
2342
25
54
24
28
63745366
28
43
38
21
68
%SiltorCay
19
7612
9
20
19
21
23111117
14
14
38
18
22
1 Feet below ground noftee.
4-5
SR303810
UNSCANNED ITEM(S)
ONE OR MORE OF THE FOLLOWING ITEMS MAY BE ASSOCIATEDWITH THIS DOCUMENT:
PHOTOGRAPHSDRAWINGS
OVERSIZED MAPSROLLED MAPS
PLEASE CONTACT THE CERCLA RECORDS CENTER TO VIEW THEITEM(S)
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The second unit extends from approximately 9 to 42 feet below the surface and ranges incomposition from silt with sand to silty gravel with sand. Cobbles and boulders may also bepresent The gravel is mostly gray and brown, fine- to medium-grained, subangular sandstonefragments. The material appears to be stratified glacial outwash. The coarseness of thematerial, the angularity of the gravel, and the range of grain sizes suggest this material has nottravelled far from its source. The second unit is virtually completely saturated as the water tablewas measured at approximately 10 feet below the ground surface during the well drilling andinstallation program.
Elevated PID measurements were noted on soil samples collected from the silty sand with gravellayer at all four borings. The highest PID measurements were noted on soil samples fromboring OW-2, which is closest to Zone L A sweet odor and weed killer odor were noted on soilsamples from this unit
The third unit extends from approximately 42 feet to bedrock and consists of tan to light brown,silty fine to medium sand. This unit is more uniform and features less gravel than the overlyingoutwash. The third unit was encountered in all boxings except OW-2 which was not sampled
i
to the depth of this unit The material appears to be an earlier deposit of glaciofluvial material.The finer grain size and greater degree of sorting indicates the material has been transportedfarther from its source than the overlying stratified outwash. Halliburton NUS (1988) reportedthat the type of gravel (quartz and feldspar) found in unit 3 suggests an igneous source material.
The results of the present and previous investigations indicate unit 3 occupies a buried bedrockchannel (see Plate 3-8 for location of the channel). Borings outside the buried channel generallyencounter bedrock at depths of 35 to SO feet and do not penetrate unit 3. The buried channelfirst became evident when Phase n boring E-3 was drilled to a depth of 76.5 feet withoutpenetrating bedrock. Two and possibly three Phase m borings also intersected the buriedchannel. Phase ffl soil boring SB-100 was located approximately 170 feet east-northeast ofmonitoring well MW-E3 and drilled to a depth of 60 feet without encountering bedrock.Phase m boring SB-101 penetrated the buried channel at a point approximately 410 feet east-
4-8
8R303813
northeast of. monitoring well MW-E3. Limestone bedrock was reportedly encounteredunderlying unit 3 type material within the buried channel at a depth of 98 feet at boring SB-101(monitoring well MW-M125), which is located approximately 150 feet northeast of the new testwell (TW-1)7. Unit 3 type material may also have been encountered at Phase m boringMW-M120 where a very uniform fine to medium sand was reportedly sampled at a depth of 58to 60 feet and bedrock was encountered at a depth of 110 feet Monitoring well MW-M120 islocated •approximately 2,050 feet east of monitoring well MW-E3. None of the boringscompleted during the present investigation were advanced to bedrock. The deepest boring(TW-1) was advanced to a depth of 88 feet
Elevated PID measurements were recorded on all soil samples from unit 3. Measurementsranged from 0.5 to 4.5 ppm (isobutylene equivalent) on samples from the test well boring(TW-1). The highest measurements were recorded on samples from approximately 42 to 55feet A sweet odor like weed killer was noted on soil samples from 42 to 65 feet A PIDmeasurement of 2.5 ppm (isobutylene equivalent) and a sweet odor were noted on the one unit 3soil sample collected from boring OW-3. PID measurements on unit 3 soil samples fromboring OW-1 ranged from 0.1 to 0.4 ppm (isobutylene equivalent), and no odor was noted.
The fourth unit was found only in boring OW-2 and consists of a very dense gray silty clayeyfine sand. It is believed this material was encountered at a depth of approximately 39 feet basedon auger penetration. A sample of the material was collected from 41.0 to 41.8 feet The unitappears to extend to a depth of 42 feet as the borehole collapsed to that level after the auger wasadvanced to 45 feet and withdrawn to 40 feet The test well (TW-1) was sampled continuouslyfrom 35 to 45 feet and did not encounter the silty clayey sand of the fourth unit
The fourth unit may be a depression rilling or till deposited in the buried channel between thetwo layers of outwash material (units 2 and 3). The unit appears to correlate with material
7 This finding is based on rock fragments recovered on a roller bit at SB-101. No bedrockwas actually cored.
4-9
AR3038U
described as "claystone, gray, weathered and partially decomposed" which was encountered from38.5 to 42.0 feet below the surface at Phase U boring E-3, which is located approximately250 feet southwest of monitoring well OW-2. The classification appears to be a misnomer as34.5 feet of "sandstone fragments" were penetrated beneath the "claystone" layer before boringE-3 was terminated at 76.5 feet without reaching bedrock. The fourth unit may also correlatewith the gray silty clay with fine to coarse sand encountered from 35 to 36.5 feet, overlyinggray shaley claystone, at Phase m boring MW-M115. The absence of the gray silty clayey finesand in other borings may be a result of discontinuous deposition or erosion prior to depositionof the younger outwash of unit 2. It is also possible that, with the exception of boringMW-M115, the material was not distinguished from the weathered gray claystone on which itmay have been deposited outside the limits of the buried channel.
A PID measurement of 0.3 ppm (isobutylene equivalent) was noted on the sample of unit 4material from OW-2. No odors were noted.
43 WELL CONSTRUCTION
Construction logs for the test well and three new monitoring wells installed by Gannett Flemingare presented in Appendix A.I.
4.3.1 Mnnitnrhiy Welfa
The three monitoring wells (OW-1, OW-2, and OW-3) were constructed of 2-inch I.D., flush-joint, threaded, Schedule 40 PVC riser pipe and screen. Each monitoring well features a 10-footslotted screen and 4-inch-krag plug. The slot size is 0.010 inch. The riser pipe extends fromme top of me screen to a point approximately 2 feet above the ground surface and is capped witha vented plug.
The boring was backfilled with Best (Best Sand Corporation) 1020 grade sand to a pointapproximately 2 feet above the top of the screen. Filter pack gradation data are included in
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8R3Q38I5
Appendix E-2. A 5- to 14-foot-thick seal of bentonite pellets or slurry was placed above thefilter pack and allowed to hydrate (a minimum of) two hours. The remainder of the boring wasbackfilled with cement-bentonite grout to a depth of approximately 3 feet below the groundsurface.
The remaining annular, space was backfilled with concrete, and a 3-foot-square, 4-inch-thickconcrete pad was constructed at the ground surface. A 5-foot-long, 4-inch diameter steel casingwas embedded into the concrete and set approximately 2 feet above ground level to protect theextended riser pipe. The protective casing features an aluminum locking cap and padlock.Three 4-inch diameter, concrete-filled steel posts were equally spaced around the well andembedded in the concrete pad. A tag identifying the well number, the USAGE Omaha District,and the top of casing elevation was affixed to each aluminum locking cap.
The alignment of each monitoring well was tested with a 5.4-foot-long, 1.75-inch O.D. PVCbailer. The bailer passed freely through all three monitoring wells.
4.3.2 Test WeU
The test well (TW-1) was constructed of nominal 6-inch I.D., flush-joint, threaded, Schedule 80PVC riser pipe and continuous-slot screen. The screened interval extends from approximately15 to 85 feet below the ground surface. A 6-inch plug was installed at the bottom of the screen.The riser pipe extends from the top of the screen to a point approximately 2 feet above theground surface. Stainless steel centralizers were installed at depths of 15,45, and 75 feet belowthe ground surface.
The screen slot size and filter pack material were selected based on the results of analyses of soilsamples collected from 15 to 72 feet at boring OW-1, which is located approximately 15 feetfrom the test well. The slot size is 0.020-inch for the screen interval from 35 to 85 feet and0.030-inch for the screen interval from 15 to 35 feet Best grade 1635 sand was used to backfill
4-11
flR3038!6
the boring to a depth of 35 feet, and Best grade 1020 sand was used to backfill the boring froma depth of 35 to 13 feet.
After completion of development, a 5-foot-thick seal of bentonite pellets was placed above thefilter pack. The portion of the seal above the water table was added in 1-foot lifts and allowedto hydrate two hours between lifts. The remainder of the annulus was backfilled with cement-bentonite grout to a depth approximately 3 feet below the ground surface.
A 3-foot-square, 4-inch-thick concrete pad was constructed at the ground surface. A 5-foot-long, 8-inch diameter steel casing was embedded into die concrete and set approximately 2 feetabove ground level to protect the extended riser pipe. The protective casing features analuminum locking cap and padlock. Three 4-inch diameter, concrete-filled steel posts wereequally spaced around the well and embedded in the concrete pad. A tag identifying the wellnumber, the USAGE Omaha District and the top of casing elevation was affixed to the aluminumlocking cap.
The alignment of the test well was tested with a 10.3-foot-long, 4.5-inch diameter PVC pipesuspended from a 5.0-inch diameter PVC hoisting plug. The pipe passed freely through the testwell.
4.4 WELL DEVELOPMENT
Development logs for the test well and three new monitoring wells installed by Gannett Flemingare presented in Appendix A.I. Water generated during well development'was collected in a300-gallon trailer-mounted tank and hauled to the unlined lagoon in Zone I for disposal.
4.4.1 Mnnitnriny Wglfa
Monitoring wells OW-1, OW-2, and OW-3 were developed by surging, bailing, and pumping.Monitoring well OW-1 was also jetted with hydrant water to remove a small amount of cement
4-12
!' AR3038I7
which had inadvertently entered the well during construction. A mechanical surge blockattached to drill rods was used to surge OW-3. The other monitoring wells were surged withan air-driven development pump with bushings at both ends.
Bailing was attempted at each of the monitoring wells but proved ineffective. As a result, thewells were developed with an air-driven well development pump operated by a gas-driven aircompressor. A controller permitted the regulation of pump recharge and discharge intervals.The pumping rate varied from approximately 1 to 2 gallons per minute. The volume of waterremoved from each well varied from 367 to 695 gallons.
Temperature, pH and specific conductivity were monitored during well developmentGroundwater temperature was approximately 11° C, and pH was 5.5. Specific conductivityranged from 3,600 S' at OW-1 to 7,000 S and 7,800 S at OW-3 and OW-2, respectively. Boththe low pH and high conductivity are attributable to high concentrations of dissolved iron in thegroundwater. The dissolved iron is highly conductive and when it oxidizes from ferrous toferric iron, it produces excess acidity and lowers the pEL The oxidation of organic componentsin the groundwater promotes the reduction and subsequent dissolution of iron. A final turbidityof 28 Nephelometxic Turbidity Units (NTUs) was measured at TW-1. Final turbiditymeasurements at OW-1, OW-2, and OW-3 were 23, 99 and 50 NTUs respectively. The waterappeared to turn from pale yellow to orange with exposure to the atmosphere. Development wasterminated when little or no sediment entered the well and temperature, pH, and specificconductivity had -«*ahiii»grf- A one-quart jar of water was collected and photographed at thecompletion of development Photographs are attached to the well development logs presentedin Appendix A.I.
1 1 Siemen (S) - 1 ,uMHO/cm2.
4-13
HR3038I8
4.4.1 Test Wefl
The test well (TW-1) was developed January 25-28, 1991 by mechanical surging, bailing, andpumping. A bailer was used to remove sediment from the well prior to and after surging. Thetest well was surged with a mechanical surge block attached to drill rods. The well was pumpedat approximately 6 to 7 gallons per minute (GPM) and was drawn down approximately 3 to 3.5feet More than 1,800 gallons of water were removed from the well during development.
Temperature, pH and specific conductivity were monitored during well development.Groundwater temperature was approximately 12° C, pH was 5.5, and specific conductivity wasapproximately 3,800 S. The final turbidity measurement was 28 NTU. The water turned frompale yellow to orange with exposure to the atmosphere. Development was terminated when littleor no sediment entered the well and temperature, pH, and specific conductivity had stabilized.A one-quart jar of water was collected and photographed at the completion of development Aphotograph of the water is attached to the test well development log presented in Appendix A.I.A water sample was collected at the completion of development and analyzed for total solids.The laboratory analysis indicated a total solids content of 4,570 mg/kg. The laboratory reportis presented in Appendix E.3.
4.43 Test Well Redevelopment
On August 9,1991, Gannett Fleming attempted to perform a step-drawdown test on the test well(TW-1). Pumping at approximately 48 GPM, the well ran dry hi approxiinately 2.5 minutes.The well was also pumped at rates varying from 16 to 20 GPM and ran dry hi less than fourhours. Because of the well's diminished performance, Gannett Fleming undertook a programof activities intended to enhance the yield of die test well prior to performing another step-
4-14
flR3038!9
drawdown test .and the 72-hour constant rate9. The program of activities is set forth hiConfirmation Notice No. 5 (Appendix D).
A video camera was passed through the test well to examine the condition of the screen. Nounusual conditions were observed.
Each Bart test kits were used to analyze groundwater from the test well for iron-related bacteria(1KB), sulfate-reducing bacteria (SRB), and slime-forming bacteria (SLYM). The IRB testindicated the presence of iron-related bacteria plus a mixture of enteric and pseudomonadbacteria. The SRB test indicated the presence of sulfate-reducing bacteria plus a variety of otherbacteria. The SLYM test indicated the presence of a variety of slime-forming bacteria, whichmay also include pseudomonad and enteric types of bacteria, Gannett Fleming also sampledmonitoring well OW-3 and found similar results10.
Gannett Fleming added two pounds of commercial pool cUorinator consisting of 65% calciumhypocfalorite to eliminate bacteria and allowed the chlorine to remain in the well overnight. Thenext day, the well was surged with a bristled surge block and then purged. Gannett Flemingacidified the well by adding a 55-gallon drum of industrial grade muriatic acid to dissolve irondeposits. The acid remained in the well overnight Gannett Fleming surged the well with thebristled surge block, added water to dilute the acid, and purged the well dry again.
Substantial improvement in the well's pumping performance was observed the next day. Thewell was pumped at rates varying from approximately 27 to 42 GPM over a period of 3.5 hours.
9 Mr. Gordon G. Lewis, Geological Engineer, Geotechnical Branch, Omaha District,USAGE, was present during redevelopment of the test well.
10 At the completion of the recovery test following the 72-hour constant rate pumping test,GF again sampled the test well (TW-1) for stime-fonning bacteria and iron-relatedbacteria. TW-1 again tested positive for all types of bacteria.
4-15
flR303820
The average discharge was approximately 39 GPM. The water became less turbid as pumpingcontinued. It was determined that the test well was sufficiently redeveloped to proceed with thestep-drawdown and 72-hour constant rate pump test.
Gannett Fleming's experience indicates biofouling of wells is a problem requiring attention inthe design of the groundwater extraction wells hi Zone n.
4.5 SURVEYING
Gannett Fleming established horizontal coordinates and vertical elevations for the top of casingfor the three new monitoring wells and the test well using available survey monuments from thePhase m RI. Survey notes are presented in Appendix F.
4-16
ftR30382l
AR303822
5.0 AQUIFER TESTING
Gannett Fleming tested the overburden aquifer in Zone n by means of in-situ hydraulicconductivity testing (i.e., slug testing), a step-drawdown test, a 72-hour constant rate pump test,and a recovery test These activities were performed in accordance with the USAGE Scope ofServices (U.S. Army Corps of Engineers, 1990) dated July 2, 1990 and the Final QualityControl and Sampling Plan (Gannett Fleming, 1990) dated December 1990. The activities wereperformed in modified Level D and Level C personal protective equipment as required by theFinal Safety, Health, and Emergency Response Plan (Gannett Fleming, 1990) dated December1990 governing these activities.
5.1 IN-STTU HYDRAULIC CONDUCTTVnY TESTING\
After the completion of well development, Gannett Fleming performed in-situ hydraulicconductivity tests on the three new monitoring wells (OW-1, OW-2, and OW-3) and the test well(TW-1). In February 1991, Gannett Fleming performed two falling head and two rising headtests at each well except OW-2 where Gannett Fleming performed three sets of tests. Pursuantto Confirmation Notice No. 5 (Appendix D), Gannett Fleming performed one additional fallinghead and one additional rising head test at the test well (TW-1) and monitoring well OW-3 inAugust 1991. The additional testing of TW-1 was performed prior to the redevelopmentactivities described in Section 4.4.3.
The tests and analyses were conducted in accordance with the methods set forth by Bouwer andRice (1976). The slug test consisted of instantaneously changing the water level in the well andmeasuring the rate of recovery with a pressure transducer connected to a data logger. A solidPVC positive displacement body (slug) was instantaneously inserted into or withdrawn from the
»
water to induce the change in head. A 5-feet by 4-inch diameter slug was used in the test well,and a 3.25-feet by 1.5-inch diameter slug was used in the monitoring wdls.
5-1
AR303823
The Aqtesolv computer program (Duffield and Rumbaugh, 1989) was used to calculate valuesof hydraulic conductivity based on Bouwer and Rice analysis of recovery data. Results of thein situ hydraulic conductivity testing are summarized in Table 5-1. Recovery data and computerprogram output are presented in Appendix G.
TABLE 5-1
SUMMARY OF SLUG TESTING RESULTSDRAKE CHEMICAL SHE
WellID
TW-1
OW-1
OW-2
OW-3
Trial
12312123123
Hydraulic Conductivity (ft/min)Falling Head
Test4.30 x 10*3.25 x 10*3.98 x 10-37.31 x 1046.83 x 10-39.47 x 1O35.83 x IV31.02 x Ifr22.82 x 10-22.58 x 10-23.11 xlO-2
Rising HeadTest
2.25 x 10*2.31 x 10*3.99 xlO47.74 x Ifr18.43 x 10-31.27 x lO"21.43 x 10-21.50 x 10-23.57 x 10-23.51 x 10-22.86 x 10-2
Hydraulic Conductivity (ft/day)Falling Head
Test656111014815113745
Rising HeadTest336111218.2122515141
Hydraulic conductivity values range from approximately 4 x 10"3 feet/minute at TW-1 toapproximately 3 x 10* feet/minute at OW-3. The values at TW-1 and OW-3 measured inAugust 1991 did not vary significantly from the values measured in February 1991. Thehydraulic conductivity values are within the range of typical values for fine to coarse sandsreported by Driscoll (1986) and the U.S. Environmental Protection Agency (1990).
5-2
8R303821*
5.1 STEP-DRAWDOWN TEST
Gannett Fleming attempted to perform a step-drawdown test August 9, 1991, but the test wasunsuccessful as the test well ran dry in less than four hours of pumping at rates varying from16 to 20 GPM. It was also noted that the test well ran dry in less than 2.5 minutes whenpumped at approximately 48 gallons per minute. After consultation with the USAGE, GannettFleming redeveloped the well as described in Section 4.4.3.
Gannett Fleming performed a successful step-drawdown test August 23,1991. The test well waspumped for consecutive 60-minute periods at successive rates of approximately 29, 34, 40, and45.5 GPM. During the test, Gannett Fleming monitored the pumping rate and water levels inTW-1, OW-1, OW-2, and OW-3. Water levels were measured with electronic water levelindicators and with pressure transducers connected to a data logger. Step-drawdown test data,including time-drawdown plots and recovery data, are presented in Appendix H. Results of thestep-drawdown test are summarized in Table 5-2. The specific capacity of the well decreasedfrom approximately 1.29 GPM/ft. to 0.89 GPM/ft. as the pumping rate increased from 29 GPMto 45.5 GPM.
*
Weather conditions were relatively stable during the step-drawdown test No rain was measured;the barometric pressure fell from 30.20 to 30.17 inches of mercury; the temperature increasedfrom 82°F to 83°F; and the relative humidity decreased from 64%to61%11.
Gannett Fleming collected a groundwater sample from the test well at the completion of the step-drawdown test Results of laboratory analyses of groundwater samples are presented in theDraft Treatability Testing Report (Gannett Fleming, 1991).
11 Barometric pressure, temperature, and relative humidity data were obtained from NOAAweather radio report issued from Williamsport/Lycoming County Airport, which isapproximately 20 miles east of the site and within the West Branch Susquehanna RiverValley.
5-3
AR303825
TABLE 5-2
SUMMARY OF STEP TESTING RESULTSDRAKE CHEMICAL SITE
TestStep
Number1234
PumpingRate(gpm)29344045.5
SpecificCapacity(gpm/ft)1.291.191.050.89
Drawdown After 60 Minutes (ft)TestWellTW-122.61628.66137.95751.041
Observation Wells
OW-1
2.8513.3443.9704.513
OW-2
1.0931.5351.6961.777
OW-3
0.7740.9881.1901.385
Data collected during the step-test were used to evaluate the efficiency of the test well by thesimple graphical method described by Bierschenk (1964) and suinmarized in Driscoll (1986).The graphical analysis and subsequent calculation of the ratio of laminar head loss to total headloss yield a value approximately 45%. This means that much of the head loss caused byinefficiency is associated with turbulent flow rather than laminar flow. However, subsequentcalculation of true well efficiency based on empirical equations developed from modifiednonequilibrium equations described by Jacob (Driscoll, 1986) indicated that the true well.efficiency is approximately 86%. Well efficiency calculations are presented in Appendix H.4.
5-4
SR303826
5.3 72-HOUR PUMP TEST i
5.3.1 Pmnp Test Set-Up
Gannett Fleming performed a 72-hour constant rate pumping test August 26-29, 199112. A5-horsepower stainless steel submersible electric13 pump was used to pump water from the test
' well (TW-1) at a constant rate of approximately 35 GPM. The cumulative discharge anddischarge rate were monitored with a Rockwell flowmeter. A groundwater volume of 152,472gallons was discharged during a continuous pumping period of 4,334 minutes. Water dischargedfrom the well was conveyed to a temporary pool constructed in Zone L The water wascontained in the pool until the completion of the recovery test when it was allowed to drain intothe unlined lagoon.
Gannett Fleming collected a round of static water level measurements the morning of August 26prior to starting the 72-hour pump test (Plate 3-6). During the pump test, pressure transducersand data loggers were used to monitor drawdown at the following wells: TW-1, OW-1, OW-2,OW-3, MW-M4, MW-M125, MW-E3, MW-M18, MW-M15, and MW-M115. Electronic waterlevel indicators were also used to manually monitor drawdown in the above mentioned wells andother wells during the course of the pump test Gannett Fleming measured the water level ofall the Drake wells included in the groundwater monitoring program at least once during thecourse of the pump test
Pressure transducers in the test well (TW-1) and three new monitoring wells (OW-1, OW-2, andOW-3) were connected to an in situ Hermit 2000 data logger programmed to collect data on a
12 Mr. Paul Anderson, Project Geologist, Engineering Division, Omaha District, USAGE,was present during the pump test and recovery test
13 A liquid propane generator was used to power the pump.
5-5
AR303827
modified logarithmic time scale for the first 2 minutes, then at 30-second intervals until10 minutes of pumping elapsed, then at 2-minute intervals until 100 minutes of pumping elapsed,and then at 5-minute intervals for the remainder of the pumping. Pressure transducers in theother monitoring wells were connected to in situ Hermit 1000 data loggers programmed tocollect data at 5-minute intervals.
5.3.2 Data Validation
Pump test data, including water level measurements and time-drawdown plots for wells affectedby the pumping, are presented in Appendix I. The data collected by the data logger andpressure transducers installed at the test well (TW-1) and the three monitoring wells (OW-1,OW-2, and OW-3) constructed by Gannett Fleming agreed with manual measurements and wereconsidered valid. In addition, the data collected by the data loggers and pressure transducersinstalled at monitoring wells MW-M4 and MW-M18 agreed with manual measurements and wereconsidered valid. Comparison of manual measurements with data recorded from transducers inobservation wells MW-E3, MW-M15, MW-M115, and MW-M125 indicated the data loggerrecords did not match the log of manual measurements as a result of various equipment failures.Despite the equipment failures, analysis of drawdown at these four wells was possible as a resultof measurements taken manually with water level indicators. Manual measurements ofdrawdown during the pump test also permitted analysis of data from monitoring wells MW-E1,MW-M2, MW-M5, MW-M6, MW-M7, MW-14, and MW-109.
5.3.3 Data Correction
GF attempted to identify unidirectional and rhythmic changes in the water table which wouldnecessitate correction of the pump test data. Corrections are often necessary to ensure that thedata reflect responses to pumping at the test well rather than other aquifer stresses. With thisin mind, GF evaluated three items: trend data prior preceding the pump test, background welldata during the pump test, and weather conditions. The results of this analysis are described inthe following paragraphs.
5-6
AR3Q3828
Trend data obtained from MW-M125 during the three days prior to the pump test are plotted inFigure 5-1. The data do not indicate a trend change; however, an extremely small semi-diurnalrhythmic fluctuation is apparent. The data indicate the water level in the well was fluctuatingbetween 540.16 and 540.22. The graph shown in Figure 5-1 begins at approximately 2100 onAugust 23 as the well was completing recovery from pumping performed during the step testwhich ended the same day at 1732. The elevation of the water level in the well generally peaksbetween 0200 and 0500 and between 1700 and 1900 and generally ebbs at 0000 and between1000 and 1200 each day as it fluctuates within a narrow range of 0.06 feet This patterngenerally repeats itself in the hydrographs of many of the observation wells during the courseof the pump test Kruseman and de Ridder (1990) have attributed diurnal fluctuations inunconfined aquifers to different day and night evapotranspirationr rates. The water table dropsduring the day as consumptive use by plants increases and recovers during the night when plantstomata are closed. Evapotranspiration rates in late August are relatively high and may producesmall fluctuations in the water table especially in an area such as Zone n where the land isdensely vegetated and the water table is relatively close to the ground surface. Of course, thefluctuation may also be the result of other factors, whose rhythmic nature is less apparent, ora combination of such factors, including barometric pressure, temperature, wind, and thedewatering operation at the wastewater treatment plant Correction of the pump test data for theobserved rhythmic fluctuation, whatever it's source, is not considered necessary because thefluctuation is relatively minor and the pump test began and ended at approximately the samehour of the day.
Monitoring well MW-M115 was selected as the background well. The well is located hiZone HL approximately 1,655 feet away from the test well (Plate 3-1). The data recorded fromthe pressure transducer in monitoring well MW-M115 do not agree with manual measurementsand -were deemed unreliable. Manual measurements indicate the water level at MW-M115dropped 0.04 feet; however, only two measurements were made during the pump test The dropis within the range of fluctuation of the trend data recorded at MW-M125. The drop is alsowithin the range of fluctuation (0.06 feet) recorded at monitoring well MW-M112 during thecourse of the pump test Monitoring well MW-M112 is closer to the test well (962 feet away)
5-7
&R3Q3829
LOCM
oorLL.GLLJ
a mO
IQLLJCC
(133d) NOI1VA313
s-a AR3Q3830
I-and was measured more frequently during the pump test The pump test data from MW-M112generally reveal the same pattern of semi-diurnal fluctuation observed, in the trend data fromMW-M125. After measuring 0.06 feet of drawdown 817 minutes into the test (clock time0734), the water level returned to its static level 1353 minutes into the test (clock time 1630).
i i
A drawdown of 0.05 was measured 2313 minutes into the test (clock time 0830), and only0.01 foot of drawdown was measured 2740 minutes into the test (clock time 1537). Aninsufficient number of measurements was recorded at MW-M115 to permit recognition of thesemi-diurnal pattern. The background well data do not clearly indicate a unidirectional trendin water level during the pump test, so no correction of the pump test data is deemed necessary.
The weather during the pump test was generally hazy, hot, and humid. No precipitation wasmeasured in Lock Haven during the period of August 20-30. The average low temperature was63.8°F and the average high temperature was 90.4"? in Lock Haven during the period ofAugust 26-30. Barometric pressure ranged from approximately 30.17 to 30.34 inches ofmercury, relative humidity ranged from 60% to 100%, and winds were calm or less man10 miles per hour during the pump test14. Mornings were usually foggy until mid-morningwhen the fog dissipated. The fog was particularly dense the morning of August 27. Nocorrection of the pump test data because of weather conditions is deemed necessary.
5.3.4
The final values of drawdown observed at the test well and the observation wells monitoredduring the pump test are summarized in Table 5-3. A plot of drawdown contours at the end ofthe 72-hour pump test is shown in Figure 5-2. The drawdown contours are generally elongatedin a northeast-southwest direction parallel to the buried channel, Bald Eagle Creek, and BaldFagle Mountain.
14 Barometric pressure, relative humidity, and wind information was obtained from NOAAweather radio reports issued from Williamspoit/Lycoming County Airport
5-9
AR303831
TABLE 5-3OBSERVED DRAWDOWN DURING PUMP TEST OF TW-1
Pumping Test(8-29-91)Reference
Savallon(MSL)
Static WaterSevation(8-26-91)
Minutes SincePumping Started
Drawdown(Feet)
MVV-M2PillliitlSS!MW-M5mm&mmmm
0822•X'X-XvMvX •;•"•'•••:•:•>:•:•*•:•:•:•
1227554isop:f;vK:i;i;:'S:::;;::;jjWg-;::SiffiSiiSSiil
53a41IliiiSl'
537.37
MW-M115•MwiMd:':*'<'>>x K*>KvX'X*>>
MW-M119
MW-M124"""
5-10 AR303832
FIGURE 5-2
DRAKE CHEMICAL. INC
\
PUMP TEST DRAWDOWN CONTOUR PLOTLEGEND
* MONITORED BY TRANSDUCER/ DATA LOGGERDURING TEST
• AM. COLOR & CHEMICAL MONITOR WELLGann«tt F lamina Q HAMMERMILL MONITOR V/ELL
•«» AM»-n~£t« 8 3 DRAKE CHEMICAL MONITOR WELL« DRAKE CHEMICAL WELL
SCALE (INSTALLED BY GANNETT FLEMING)if0' MW'MII7> INCLUDED IN GANNETT FLEMING
GROUNDWATER MONITORING PROGRAM
s-n SR303833
A potentiometric surface contour plot based on final water level measurements during the pumptest is presented in Plate 3-9. Zone I monitoring wells MW-M5, MW-M6, MW-M7, and MW-M108 were considered in preparing the plot No water level measurements during the pump testare available from American Color and Chemical Corporation.
The pump test data were analyzed using the Theis (1935) method and the Thiem-Dupuit method(Thiem, 1906 and Dupuit, 1863). Only observation wells exhibiting at least 0.1 feet ofdrawdown were analyzed. Although the Theis method was developed to describe unsteady-stateflow in a confined aquifer, the method also applies to unconfined aquifers that do not exhibitdelayed yield or delayed water table response. The Thiem-Dupuit method also applies becausethe pumping test had approached a virtual steady-state after 72 hours of pumping. The pumptest generally meets the assumptions required by these two models (e.g., homogeneous aquiferof seemingly infinite area! extent, horizontal water table, constant discharge rate, fullypenetrating test well) with the notable exception of uniform aquifer thickness. The aquifer isroughly twice as deep in the buried channel as it is elsewhere in Zone n. The problem ofuneven aquifer thickness does not apply in the case of monitoring wells also located in the buriedchannel (OW-1, OW-2, OW-3, MW-E3, and MW-M125). To minimize complications withrespect to wells located outside the buried channel, the pumping rate at the test well wasrestricted to approximately 35 GPM. By pumping at a lower rate, Gannett Fleming sought tominimize the disruption of flow lines as a result of uneven dewatering of the aquifer because ofvarying aquifer thickness.
The Aqtesolv computer program (Duffield and Rumbaugh, 1989) was used to calculate valuesof hydraulic conductivity and transmissivity based on pump test data using the Theis method.The Dupuit formula was used to manually c?iaiigt«» values of hydraulic conductivity andtransmissivity based on pump test data. Results of the pump testing are summarized inTable 5-4. Computer program output and manual calculations are presented in Appendix I.
5-12
8R303831*
s-13 AR303835
Hydraulic conductivity values generated by the Theis method range from approximately5.12 x 10-3 feet/minute at MW-M5 to approximately 8.04 x 10"1 feet/minute at MW-M109.Monitoring well MW-M5 is screened in a silty fine sand layer above the sand and gravel layerin Zone I where relatively lower hydraulic conductivities might be anticipated.
The Dupuit formula generated hydraulic conductivity values of 1.21 x 10*2 feet/minute for theinterval between monitoring wells OW-1 and MW-E3 and 1.27 x 10*2 feet/minute for the intervalbetween monitoring wells OW-2 and MW-M4. The Dupuit formula could not be used tocalculate the hydraulic conductivity of the interval between monitoring wells OW-3 andMW-M125 because drawdown was slightly greater at monitoring well MW-M125 which islocated approximately 100 feet farther from the test well. Although this phenomenon may bethe result of a faulty performance by observation well OW-3, it is more likely the result ofinterference from the dewatering operation at the wastewater treatment plant that was on-goingduring the performance of the pump test in Zone n. Monitoring well MW-M125 is believed tobe within the fringe of the zone of influence of the dewatering operation. Analysis of waterlevels of selected monitoring wells before and after dewatering at the treatment plant suggest thatmonitoring well MW-M125 may have been drawn down approximately 0.45 feet at the time ofthe pump test as a result of the dewatering operation. An analysis of the aquifer based onpumping associated with the dewatering at the wastewater treatment plant is presented inSection 5.5.
The results determined using the Dupuit formula are considered to be the most accurate resultsas the pump test had approached a virtual steady state after 72 hours of pumping. The resultsgenerated for the six observation wells closest to the test well (monitoring wells OW-1, OW-2,OW-3, MW-M4, MW-E3, and MW-M125) are considered the most accurate as these wellsexhibited the greatest amount of drawdown during the pump test The results generated forobservation wells farther from the test well, where observed drawdowns were smaller, areconsidered relatively less reliable.
5-14
SR303836
5.4 RECOVERY TEST
Gannett Fleming performed a recovery test immediately following the completion of the 72-hourconstant rate test The pump and discharge piping remained set in the well until the completionof the recovery test Gannett Fleming used water level indicators and pressure transducersconnected to data loggers configured in the same manner as for the pump test to monitorrecovery of the test well and monitoring wells for a period of approximately 12 hours.Recovery test data, including time-recovery plots for wells affected by the pumping, arepresented in Appendix I.
Results from the test well (TW-1) and the three closest observation wells (OW-1, OW-2, andOW-3) were analyzed using the Theis recovery method. The Aqtesolv computer program(Duffield and Rumbaugh, 1989) was used to perform the analysis. Values of hydraulicconductivity and transmissivity generated by analysis of the recovery data are «irpnf ri 4 inTable 5-4.
Gannett Fleming collected a groundwater sample from the test well at the completion of therecovery test Results of laboratory analyses of groundwater samples are presented inTreatabiUty Testing Report (Gannett Fleming, 1991).
5.5 WASTEWATER TREATMENT PLANT DEWATERING
Water level data from the four monitoring wells closest to the wastewater treatment plant wereused to calculate values of hydraulic conductivity and transmissivity. The Dupuit formula wasused to calculate these values based on drawdown caused by the massive dewatering operationbegun June 19,1991 as part of the facilities expansion program necessitated by construction ofthe flood control dike along Bald Eagle Creek. Round 5, 6, and 7 water levels from selectedwells were analyzed to estimate drawdown in monitoring wells MW-M124, MW-M122,MW-Ml 19, and MW-M125 as a result of the dewatering operation. According to the treatmentplant supervisor, the pumping rate during dewatering is approximately 350 GPM. Results ofthe analysis are summarized in Table 5-5.
5-15
flR303837
TABLE 5-5
SUMMARY OF RESULTS BASED ON DEWATERINGAT THE WASTEWATER TREATMENT PLANT
Round
V
VI
VH
WellID
MW-M124
MW-M122
MW-M119
MW-M125MW-M124
MW-M122
MW-M119
MW-M125MW-M124
MW-M122
MW-M119
MW-M125
EstimatedDrawdown
(feet)
12.12
2.37
0.60
0.0011.83
3.97
0.60
0.2912.85
4.12
0.45
0.45
Hydraulic ConductivityK
(ft/min)
—
0.12
0.10
0.11-
0.16
0.11
0.12—
0.14
0.09
0.11
(ft/day)
—
176
144
154—
232
151
167—
204
135
153
Transmissivity(ft*ft/min)
—
4.27
3.55
9.23—
5.47
3.63
9.87—
4.86
3.32
9.03
5-16
SR303838
AR303839
6.0 MODELING OBJECTIVE
Extensive groundwater modeling was done by Halliburton NUS as part of the Phase in RI(Halliburton NUS, 1988). The modeling described in this report updated and built upon theprevious modeling. Also, the modeling of this report was conducted to achieve separateobjectives from those set by the Halliburton NUS modeling.
As noted in the Scope of Services, dated July 2, 1990, the following modeling objectives wereset for this effort:
The model should s>" a*3 aquifer characteristics of the overburdenabove the bedrock.
Data from the pump test should be used in the model.
Data from previous investigations should be validated and used to enhance modelperformance, where applicable.
The model should be calibrated to existing conditions at the site.
The model should be sensitive to future site changes, including changes toinfiltration rates at the site after remediation and groundwater elevation effectscaused by the Susquehanna River and Bald Eagia Creek.
The model should be definitive for design of an efficient and effectivegroundwater extraction system.
The MODFLOW model, which is readily available to the USAGE, should beused.
6-1
AR3038UO
AR3038U
7.0 MODELING APPROACH
7.1 Identification of Models
Two separate but related computer programs were used to simulate groundwater flow patternsof the overburden material above the bedrock. The first program was the Modular Three-Dimensional Finite-Difference Groundwater Flow Code, also known as MODFLOW.MODFLOW was developed by the United Stated Geological Survey (McDonald and Harbaugh,1988). It is well documented, publicly available and generally accepted within the scientificcommunity. The second program is referred to as MODPATH and is the code written tocompute and display flowlines in conjunction with MODFLOW. MODPATH also wasdeveloped by the USGS (Pollock, 1989). It is a relatively new computer program that hasrecently been finding use by groundwater scientists and engineers. Both MODFLOW andMODPATH were constructed to run on an IBM PC compatible microcomputer.
.7*1 Conceptual Model
Based upon the hydrogeologic setting described in Section 1.2, a conceptual model ofgroundwater flow was developed for the Drake Site. Groundwater flows generally east andsouth from the Drake Site. The aquifer receives recharge from infiltrating precipitation andlateral groundwater flow from upgradient areas. The aquifer is hydraulically connected to theBald Fagle Greek, which can serve as a discharge or recharge area depending upon creek waterlevel. Elevation of bedrock and variations within alluvial materials affect flow rates anddirections within the aquifer.
Gannett Fleming began the development of a groundwater flow model by generating a waterlevel contour map to which the MODFLOW model could be calibrated. Data from the followingwater level measurements were analyzed to determine the long-term average groundwater levelsthat establish these contours:
7-1
SR3038U2
• Seven rounds by Gannett Fleming from October 1990 to October 1991.
• Nine rounds taken by REMCOR, Inc., at American Color and Chemical wellsduring the September 1990 to October 1991 period.
• Seven rounds reported by REMCOR, Inc. in the 1990 Pump Test Report forAmerican Color and Chemical wells.
* Three rounds taken by Halliburton NUS as part of the Phase UJRI from January1988 to May 1988.
* Two rounds taken by Keystone Environmental Resources, Inc. at American Colorand Chemical wells during May and June 1987.
» Five rounds taken by Halliburton NUS as part of the Phase I RI from October1983 to February 1984.
A .table and graphs showing the data from these measurements are contained in Appendix J. Thedata were used to estimate the annual average water levels shown in Table 7-1 and Figure 7-1.Data were not available to evaluate effects of the impoundment at the ACC site. However, theimpoundment at the Drake site does affect the groundwater model by cawing a recharge moundin the water table. Figure 7-1 shows the actual long-term average water table conditions andFigure 8-3 shows the simulation results. Both contain mounding beneath the Drake site.
Table 7-2 summarizes hydraulic conductivity values that have been calculated at the DrakeChemical Site. Values ranged from the 0.06 feet/day value observed in shallow well MW-M6to the 204 feet/day value observed at overburden well MW-M122. The results demonstrateconsiderable variation in hydraulic conductivity. A portion of the variation may be attributedto formation and gradation changes within alluvial materials. The variation may also beattributable to changes in testing methods. For example, hydraulic conductivity values for wells
7-2
flR3Q38l*3
TABLE 7-1
LONG-TERM AVERAGE GROUNDWATER LEVELSDRAKE CHEMICAL SITE
Location
ZonalZone II
Zone ffl
ACCSite
Off-Site,
Well ID
MW-M2MW-M4MW-M125MW-E3MW-M15MW-M112OW-1OW-2OW-3TW-1
MW-M119MW-M115MW-M117MW-M11AMW-M113
MW-18BMW-21MW-20MW-28MW-2BMW-25MW-8MW-14MW-1MW-6MW-5MW-7MW4
MW-M102MW-M104MW-M124MW-M122MW-M»Staff Gage
Annual Level By Year
1983
544.7542.4542.6543.4540.7541.4
--.-
539.0539.5540.1537.9539.8
545.8545.5545.6545.0546.2549.7556.0548.1547.1549.9550.7550.2546.0544.3544.2640.9542.0550.7-
1984
547.8547.7547.3548.1546.3547.0
-.--
544.5545.1545.7546.0545.4
550.2549.9550.0549.4550.6554.1560.4552.5551.4554.3555.0554.6550.4549.8549.1545.8547.0553.5-
1986
544.8543.0543.0543.8541.5542.3-.--
539.8540.3541.0541.3540.7
545.4545.1545.2544.6545.8549.3555.6546.7546.6549.5550.3549.8545.6545.3544.7541.4542.5555.4-
1987
546.4
544.5544.3545.1543.1543.8...-
541.3541.9542-5542.8542.2
545.2545.2545.3544.4545.6549.2555.6547.9546.8549.4550.2549.5545.3545.0544.4 •541.1542.2555.1-
1988
545.0543.03.543.1543.9541.6542.2...-
539.7540.1540.9541.0540.4
545.5544.7544.9544.7545.9549.5556.0548.1547.0549.7550.5549.7545.6545.5544.9541.5542.7551.5-
1990
545.5543.6543.7544.6542.1542.9...-
540.2540.7541.4541.7541.1
545.9545.3545.5545.7546.2549.9556.2548.1547.4550.1550.8550.3546.3545.9545.4542.0543.1552.4-
1991
546.0545.0545.1546.1543.6544.3545.2545.0544.9545.1
541.5541.7542.6542.8541.9
547.3545.6545.9546.3547.1550.7556.3549.6547.3550.7551.4550.8546.7546.7546.0543.7544.8552.8540.2
Long-TennAvenge546544544545542543..-
.
541541542542542
546546546546547550557549548550551551547546546542543553-
Note: Supporting data are shown in Appendix J.
7-3
HR3038W
TABLE 7-2
MEASURED VALUES OF HYDRAULIC CONDUCTIVITYDRAKE CHEMICAL SITE
Well ID
TW-1
OW-1
OW-2
OW-3
MW-E1MW-E3
MW-M2
MW-M4
MW-M5
MW-M6
MW-M9
MODFLOW GridLocation
Row
9
9
9
9
510
5
8
10
10
7
Column
11
11
11
11
710
9
11
8
7
.
HydraulicConductivity(ft/day)
6.24.75.73.23.35.72.2
10.59.8
11.112.115.825.513.68.4
14.718.320.621.630.737.0
40.637.244.851.450.541.236.640.856.99.64
79.321.3268
18.4287
0.217.40.04
33.11.56
MeasurementMethod
Slug test - falling headSlug test - falling headSlug test - falling headSlug tent - riling headSlug test - rising headSlug tftt - rising h**dRecovery observationSlug test - falling headSlug tort * frflfag headSlug test • rising headSlug test - rising headRecovery observation72 Jf uuww test
Slog test - falling headSlug test - failing headSlug **tt - falling h**Slug test - rising headSlug test - rising headSlug ten* - risp*g headRecovery observation72-hr pump test
Slug test - falling headSlug teat - falling headSlug teat - foiling beadSlug test - rising headSlug test - rising headSlug test • rising headRecovery observation/ S"**ir UTff I T72-hr pump testBail testT2,-ttt putnp testBail test72-hr Dumo testBail test72-hr unrnp twtBail test72-hr pomp testBail test72-hr numn testBail test
Source
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7-5
TABLE 7-2 (Cont'd.)
MEASURED VALUES OF HYDRAULIC CONDUCTIVITYDRAKE CHEMICAL SITE
Well ID
MW-M11AMW-M13MW-M14
MW-M15
MW-M18
MW-M102MW-M104MW-M112MW-M113MW-Ml 15MW-Ml 17MW-Ml 19MW-M122MW-M124MW-M125
MW-4MW-18BMW-20MW-21MW-25MW-28
MODFLOW Grid
Row
161512
12
7
121517151510349
66s5116
Column
1398
13
10
4121112131620172121
476536
HydraulicConductivity(ft/day)
9.922.102.69
1634.25
5118.5
28715.625.62.92
91.649.616.0143204158
0.440.60
14019819819819810590.7
A&QaUIVBDlBOtMethod
Bail testBail testBail test72-hr t>nmp testBail test/2™Hr D*'Hfl? testBail teat72-hr puiui) testSlue testSlua testStaff testStaff testStaff testSluz testExcavation dewtterinzExcavation dewaterinffExcavation dewaterinff100-minpump testRecovery72-hr vaasD test72™ "T B ""P test
72-hr Vfftp tost72-hr B fw test72-hr oumo test24— *IT o""*r* test72-hr pump test
Source
mmSigj
ffl(2)
(2}(2)
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m(4)(4)
(4)
(4)(3)<3)(3)(3)(3)(3)
Sources: (1) Phue U RI/FSPhMcOI RI/FSREMCOR GraundwBter Mankorinf Report
Army Corps of Engineer!, Field Investigation for the Aquifer Pump Test Report
(1) Phu(2) Phu(3) RE(4) U.S.
7-6
AR303847
MW-M125, MW-M5 and MW-M6 ranged up to three orders of magnitude within each well.Bail tests and slug tests, which determine hydraulic conductivities within the influence of a singleborehole, tended to show much lower values than those measured during pump tests. Pump testsmeasure hydraulic conductivity of aquifer material laying between the test and observation wells.As explained in Section 4.4.3, biofouling could also affect well performance. Biofouling orclogging are more likely to have a greater impact on single well test methods than on multiplepump test results.
Hydraulic conductivity values that were representative of the aquifer are needed for input to theMODFLOW Model. These values were generated by taking the highly variable conductivitynumbers listed in Table 7-2 as input into the Kriging portion of Surfer" (Golden Software).Kriging is a regional variable theory technique that converts calculated values at scattered knownlocations to regional values. This process was used to generate a contour map (Figure 7-2) ofhydraulic conductivities from calculated values listed in Table 7-2. Hydraulic conductivitieswere interpolated from Figure 7-2 into a 19 x 22 matrix of values which were then entered inthe MODFLOW Model. In summary this procedure took data with large variability for knownpoints and generated values that could be used to begin the calibration process.
7.3 Previous SWIFT Model
During the Phase m RI the Sandia Waste Isolation Flow and Transport (SWIFT) Program wasused to provide a means for evaluating long-term contaminant migration patterns, particularlyas they might impact Bald Eagle Creek and to a lesser extent areas where no wells wereavailable to sample groundwater quality; and to provide a means of assessing the effects ofgroundwater treatment strategies which were developed in the feasibility study. The SWIFTmodel used a finite-difference solution grid with 15 columns and 17 rows. It simulated steadystate groundwater flow and transient transport of contaminants. The groundwater model featuredthree vertical zones. Two of the zones were located within the overburden porous media andthe bedrock was considered as a single conceptual zone.
7-7
The SWIFT model was developed to operate on a mainframe computer. It is more complex thanMODFLOW and would be less efficient when used to design a groundwater extraction system.Compared to the SWIFT model, the MODFLOW model incorporated the following conceptualdifferences:
Number of Layers: One layer was used in the MODFLOW model to representthe sand and gravel overburden aquifer. The SWIFT model had employed threelayers representing the perched water, sand and gravel, and bedrock aquifers.
Extent of Model Grid: The MODFLOW model used the same orientation for itsmodel grid as was used by the SWIFT model.' However, the model grid wasextended 1,000 feet to the west to allow analysis of pumping at the AmericaColor and Chemical site and to reduce effects of boundary condition ongroundwater levels within Zone n.
Bottom Elevations: The MODFLOW model used an updated representation ofthe bottom of sand and gravel (Plate 3-8) as bottom elevations for its one layer.
Recharge: A long-term average recharge rate observed for the SusquehannaBasin is used by the MODFLOW model. Since no vegetation exists in Zone I,a higher recharge rate is used to account for the increased percolation in this area.The SWIFT model recharge rate was not identified in the Phase m RI.
7-9
flR303850
8
RR30385I
1
8.0 GROUNDWATER FLOW MODELING
8.1 Set-Up of the MODFLOW Model
The model area (Figure 8-1) covered by the MODFLOW finite-difference grid encompasses theACC site, Drake Zones I through m, and land extending southward to the Bald Eagle Creek.In plan view, the model area resembles a rectangle measuring 3,500 feet in the north-southdirection by 4,500 feet in the east-west direction. The southeast comer of the model area istruncated by Bald Eagle Creek. Gannett Fleming overlayed a grid composed of 19 rows and22 columns on the model area. Gannett Fleming centered the grid on the test well (TW-1),which is located at the center of row 9 and column 11. The row heights and column widthsrange from 150 to 300 feet. Grid lines are spaced more closely in Zones I and n of the DrakeChemical site in order to permit better resolution in the area where extraction wells are to belocated.
The MODFLOW program has the ability to «»nmlate constant head, no flow and general headboundary conditions. The no flow boundary condition is not applicable to the Drake Site, and
. the general head boundary condition requires hydraulic conductivity values that are not available.The MODFLOW model for the Drake site uses constant head boundaries along the perimeterof the model. In other words, the model incorporates the assumption that groundwaterelevations along its perimeter remain constant over time. Groundwater elevations along thenorth, east and west boundaries are set equal to the long-term average levels described in Section7.2. The surface elevation of Bald Fagle Creek serves as a constant head boundary along thesouth side of the MODFLOW model. Surface water elevations at this constant head boundaryare taken from the staff gage readings described in Section 3.1. Cells south and east of BaldEagle Creek are inactive. The model area is of sufficient size that boundary condition effectson groundwater levels in the vicinity of the proposed groundwater extraction system are deemedto be negligible.
8-1
AR303852
The MODFLOW model incorporates one layer representing groundwater within the alluvial"material above the bedrock. The Phase m RI report concluded that groundwater in the bedrockhad been only marginally affected by Drake-related contamination, and the Scope of Servicesspecifies that the MODFLOW model should only simulate the alluvial material.
In the model, the one aquifer layer is unconfined. Bottom elevations were derived from thebottom of sand and gravel layer contour map, (Plate 3-8) which Gannett Fleming prepared basedon the logs of 17 borings from previous investigations which were advanced to the top ofbedrock. Table 8-1 presents the 19 by 22 matrix of the bottom elevations used by theMODFLOW model.
The model incorporates two separate recharge rates (Figure 8-2). A rate of 14.5 inches/year(3.3xlQ-3 ft/day), which is the long-term observed average for the West Branch of theSusquehanna River as reported by Taylor, et aL (1983), is assigned to all areas except Zone I.The surface of Zone I has been graded to eliminate storm water runoff. Storm water in Zone Icollects in unlined depressions and percolates as additional groundwater recharge. Thispercolation contributes to a higher recharge rate in Zone I. The lack of vegetation in Zone Ialso contributes to a higher recharge rate because evapotranspiration is reduced in areas wherethere is no plant growth. Evapotranspiration was decreased by 25% to account for lack ofvegetation in Zone I. FJiminating surface runoff and decreasing evapotranspiration in Zone I,increases the recharge rate to 26.5 inches/year (6.1 x ICf3 ft/day). This rate is approximately12 inches/year higher than recharge in surrounding areas. Two MODFLOW model calculationswere made using different recharge rates to confirm the suitability of using an increased rate forZone I. Output from the calculations using only the regional recharge rate for the entire Drakesite was compared to calculations using higher recharge rates in Zone I. When the model wasrun with a single recharge rate, it did not reproduce the mounding in Zone I that can be seen
i
in Figure 7-1.
8-3
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8.2 Model Calibration
The strategy for calibration consisted of repeated trial and error adjustment of the MODFLOWmodel to determine what hydraulic conductivity values would most accurately reproduce long-term average groundwater elevations. Hydraulic conductivity was considered to be the mostuncertain of the various input parameters. Values of hydraulic conductivity obtained throughfield methods were input into the kriging portion of SURFER™ to assign regional hydraulicconductivity values to each cell of the model grid. These values were then adjusted through thecalibration process until the model adequately simulated long-term groundwater elevations. Finalhydraulic conductivities were within the range of values commonly reported for sand and gravelaquifers. The final pattern of hydraulic conductivity values determined through the calibrationprocess was comparable to the initial pattern of hydraulic conductivity values estimated bykriging.
A total of 33 observation points were used to check the accuracy of model predictions. These33 observations, shown in Table 8-2, consisted of data from 19 Drake wells, 13 ACC wells, andthe staff gage on the west abutment of the Castanea Bridge over Bald Eagle Creek. Eachcalibration trial represented a steady-state solution obtained from the model using the rechargerates, boundary conditions, and bottom of layer elevations described in Section 8-1. Thehydraulic conductivity data collected in the field are found in Table 7-2. The initial values usedin the model that were estimated by kriging are shown in Figure 7-2. These values wereadjusted through calibration until the solution shown in Figure 8-3 was obtained. Finalhorizontal hydraulic conductivity values varied between 0.3-300 feet/day and are shown inTable 8-3.
Differences between hydraulic conductivities found through calibration verses these determinedthrough field methods can be attributed to the modeling process. The conductivity value usedin modeling is an average value for the entire cell. Cell sizes varied and ranged from 150 feetby 150 feet to 350 feet by 350 feet. The conductivities found in the field were for a specificpoint and not the entire area of the cell. An example of this can be demonstrated by looking at
8-6
AR3Q3857
TABLE 8-2
CALIBRATION RESULTSDRAKE CHEMICAL SITE
Well ID
MW-E3
MW-M2
MW-M4
MW-M11A
MW-M15
OW-1
OW-2
OW-3
TW-1
MW-M102
MW-M104
MW-M112
MW-M113
MW-M115
MW-M117
MW-M119
MW-M122
MW-M124
MW-M125
MW-4
MW-18B
MW-20
MW-21
MW-25
Row
10
5
8
16
12
9
9
9
9
1
2
15
17
15
15
10
3
4
9
6
6
5
5
11
Column
10
911
13
13
11
11
11
11
4
12
11
1218
16
20
17
21
124
7
6
5
3
Groundwater Levels (ft. J
Long-TermAvenge545.01
545.74
544.16 •
541.92542.69
545.21
545.01
544.88
545.14
546.13
545.53
543.43
541.64
541.32
542.04 •
540.86
543.46
542.32
544.16
546.56
546.47
546.04
545.92
550.34
MODFLOWSimulation
545.66
546.16
545.42
541.52
543.76
545.39
545.39
545.39
545.39
546.57
545.17
543.46
540.87
541.05
541.55
541.58
543.71
542.05
545.07
547.3
546.9
546.96
547.04
550.59
MSL)
Difference•0.65
-0.42-1.26
0.4
-1.07
-0.18
•0.38
-0.51
-0.25
-0.44
0.36
-0.03
1.07
0.27
0.49
-0.72
-0.25
0.27
-0.91
-0.74
-0.43
-0.92
-1.12
-0.25
8-7
flR303858
TABLE 8-2 (Cont'd.)
CALIBRATION RESULTSDRAKE CHEMICAL SITE
Well ID
MW-28
MW-2BMW-8
MW-14
MW-1
MW-6
MW-5
MW-7
Bald EagleStaff Gage
Row
6
6
13
12
10
10
7
11
13
Coiuma6918
5
7
1
7
22
Groundwater Levels (ft AMSL)
Long-TeemAverage
545.70
546.75
556.6
548.69
547.65
550.50
551.28
550.68
540
MODFLOWSimulation
547.06
546.25
555.60
548.78
548.52
549.24
551.00
549.41
540
Difference
-1.36
0.5
1.0
-0.09
-0.87
1.26
0.28
1.27
0.0
Sum of Differences =- -5.68Average of Differences =« -0.17Coefficient of Determination, r2 =» 0.96
8-8
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the data for cell row 9, column 11. The calibration process did not seem to favor either theresults of pump test data or the results of data gathered by single borehole tests (bail or slugtests). Calibration hydraulic conductivities for certain cells more closely approximately thepump test numbers than the bail/slug test numbers; for other cells the opposite effect wasobserved.
A copy of the MODFLOW output for the calibration run is presented in Appendix K. As shownin Table 8-2, there was a very high linear correlation (r2s».96) between model predictions andobserved values. On average, the model slightly overestimated groundwater elevations. For 26of the 33 observation points, the MODFLOW simulated values were within one foot of observedvalues. The largest difference between observed and simulated values was 1.36 feet, whichoccurred at well MW-28 in the American Color and Chemical area. As shown in Figure 7-1,the groundwater levels in this area exhibit a complex flow path that could not be completelyreproduced with the MODFLOW model. Because this area is approximately 800 feet fromZone n, this discrepancy should not significantly impact use of the MODFLOW model toevaluate alternative extraction well systems.
8.3 Extraction Well Placement
Gannett Fleming used the MODFLOW and MODPATH/MODPLOT computer programs to drawflowlines for extraction systems that would capture groundwater contaminates in Zones I and n.Cell-by-cell budget and head information output from MODFLOW along with stress packageand aquifer property information were used to track particles through time within the aquifer.MODPATH can predict flowlines from a specified cell location backward in time to points ofrecharge, effectively describing the capture zone of an extraction well field. A map view offlowlines can be used to identify the capture zone of a well extraction system.
8-11
A limitation of MODPATH is the requirement that all calculations be done under steady-stateMODFLOW conditions. In other words, MODPATH needs to have a non-changing flow fieldover time in order for it to draw flowlines. Comparison of MODFLOW output from 30-yeartransient calculations with steady-state calculations shows the pumping-induced cone ofdepression reaching steady state conditions within approximately seven days. Furthermore, asnoted in Section 5.3.4, the pump test reached a virtual steady state condition within 72 hours.Thus, for design of a well extraction system, use of steady-state flow field is an acceptableassumption.
Various well extraction systems were modeled to determine a system to capture groundwatercontaminates in Zones I and n. The first extraction system utilized a single well located atTW-1 (row 9, column 11) with a 35 gpm pumping rate. This system was effective in drawingflow through Zone I from the western boundary of the model grid (Figure 8-4). A moreeffective system that draws flow from Zones I and n consists of five wells. Two orientationswere modelled, one along a southeast-northwest diagonal line and the other along a southwest-northeast diagonal. Both configurations used well TW-1 as the center well along the five welldiagonal. Pumping rates for each well were set as 10, 15, 20, 25 and 30 gpm with the lowestpumping rate in the southernmost well with pumping rates increasing to the north. Thesoutheast-northwest alignment is oriented roughly perpendicular to the general hydraulic gradientin the area. The southwest-northeast alignment is oriented roughly parallel to the hydraulicgradient. Figure 8-5 is a plot of flowlines for the southwest-northeast diagonal alignment Theplot of flowlines far the southeast-northwest diagonal is shown in Figure 8-6. Both five wellconfigurations show water is pulled through Zones I and n to the extraction wells. Output fromthe MODFLOW simulations for the three extraction systems is presented in Appendix K-2.
The combination of the MODFLOW and MODPATH/MODPLOT programs should be suitablefor designing an efficient and effective well extraction system to capture groundwatercontaminates in Zones I and IL
8-12
SR303863
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8.4 Sensitivity Analysis
A sensitivity analysis was performed to evaluate how model predictions would change with! :
changes in selected components of the model. Three model changes were addressed.
» Increased and decreased values of hydraulic conductivity used across the entiremodel.
The purpose of this change was to test the uniqueness of the distribution ofhydraulic conductivities determined by the calibration. If this change has apronounced effect on water levels, then it would imply that the distribution usedfor the original simulation may be the most appropriate for this site.
• Increased and decreased constant head values .along the west boundary of themodel between and including rows 1 to 13, column 1. Constant heads were alsochanged along the north boundary at row 1, columns 1 to 13.
These boundary cells represent the location from which the model shows lateralinflow of groundwater. This change addresses uncertainty in their constant headvalues. If this change has a pronounced effect on water levels, then it wouldimply that constant heads were set at appropriate values.
• Dry cells (which MODFLOW considers to be inactive, no flow cells) at row 12,column 1; row 13, column 1; row 14, column 1.
This sensitivity analysis addresses comment no. 17 in Appendix L. The regionwhere dry cells were established represents the elevated bedrock location west ofthe.Drake Site. It is an anomalous feature that has potential to influencepredicted water surface elevations downgradient from the area. The bedrock isnearly impermeable, steeply sloped and near the surface. Since the area has not
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been studied during the RI/FS or the RD, it is not known how it affectsgroundwater flow patterns. However, it may have the effect of directing lateralgroundwater flow area around the area. To simulate such a condition dry cells,which act as no-flow areas, were used in this sensitivity analysis. This changeis considered reasonable because the saturated thickness at this location is lessthan 1.5 feet If in fact water levels at this location were reduced, then onewould expect the cells at this location to be dry creating no flow areas.
Effects of the three changes are summarized in Table 8-4. The changes are judged in terms ofthe effect on water levels at the center of Zone I, Zone n and the ACC site.
Changes in hydraulic conductive values resulted in unreasonable estimates of water surfaceelevations over entire model. Thus the hydraulic conductivities used in original simulation areconsidered appropriate for this site.
The change in constant head values had small but noticeable effects on water levels.Furthermore, the effects of changing constant head values decreases when comparing a cell atthe ACC site, Zone I and Zone IL Thus the constant head values used in the original simulationare considered appropriate.
The dry cells had no effect on water levels. This finding confirms that moving the modelboundaries beyond the previous boundaries established by Halliburton NUS (see page 7-9) wasan appropriate way to address uncertainty associated with the high bedrock west of the site.
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. Table 8-4
Sensitivity of Predicted Water Level Elevationsto Changes in Selected Components of the Model
Praia* Chemical Site
ScenarioOriginal Simulation
Hydraulic Conductivity Changes
Divided by 10Multiplied by 10
Constant Head Changes
Subtract 2.5 feetAdd 2.5 feet
Dry CellsWater
(Level After ChangHydraulic Conductivity Changes
Divided by 10Multiplied by 10
Constant Head Changes
Subtract 2.5 feetAdd 2.5 feet
Dry Cells
PredictedZone ILocation(R8, C7)547.2
561.7545.3
545.6548.8547.2
1 Water Levels (ft AMSL)ZoneELocation(R9, C12)
545.1
557.0543.6
544.3545.9545.1
Level Changes (ft)f») . (Orijrinal Simulation J vtti)' ^ • *
14.5-1.9
-1.61.60
11.9-1.5
-0.80.80
ACC Site(R12, C4)549.7
571.1546.1
548.3551.1549.6
21.4-3.6
-1.41.4
-0.1
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9.0 SUMMARY OF FINDINGS
This report presents the results of aquifer pump testing and groundwater flow modelingconducted for the U.S. Army Corps of Engineers (USAGE), Omaha District of the DrakeChemical Site located in Lock Haven, Pennsylvania. The data and material presented in thisreport are required for the design of a groundwater extraction system. The findings areorganized according to the following task requirements: potentiometric surface mapping, drillingand well installation, aquifer testing, and groundwater flow modeling.
9.1 Potentiometric Surface Mapping
Seven rounds of water level measurements were collected from October 1990 through March1991. Fifty one wells and a staff gage on Bald Eagle Creek were included in the measurements.A potentiometric surface map was drawn for each of the seven rounds. Groundwater levelsgenerally rose from October 1990 through March 1991 and declined from March 1991 throughOctober 1991. Trend data for well MW-M125 show mat water levels declined approximately5 feet during the latter time period.
The potentiometric surface maps identify groundwater levels in the lower sand and gravel layerof the alluvial material, which is of greatest interest because it represents the bulk of saturated
i
overburden in Zones I and n where groundwater extraction wells are to be located. Thepresence of a recharge mound in Zone I is indicated by shallow water levels measured at wellsMW-M5, MW-M6, MW-M7 and MW-M108, but the mound is not shown on the potentiometricsurface map because these wells are screened above the sand and gravel layer.
Potentiometric contours indicate that groundwater flows generally in eastern and southeasterndirections from Zone I toward Zone n and Bald Eagle Creek. The hydraulic gradient is steepestwhere bedrock is shallow in die southwestern comer of the American Color and Chemicalproperty, which indicates the contours reflect to some extent the bedrock surface.
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9.2 Drilling and Well Installation
A test well (TW-1) and three new monitoring wells (OW-1, OW-2 and OW-3) were installedduring the period of December 1990 to February 1991. The test well was located in the buriedbedrock channel in order to maximize available drawdown during the 72-hour constant ratepump test.
South-north and west-east cross sections were drawn based on the four new borings and boringsfrom previous investigations. These cross sections identified four basic soil units: an uppermostlayer of fill and floodplain deposits, an alluvial layer of silty sand and gravel (sandstonefragments), a more uniform alluvial layer of silty sand, and a gray silty clayey fine sand layer.The first three units were found at depths of approximately 0-9, 9-42 and 42-98 feet below theground surface, respectively. The fourth unit was observed from 39 to 42 feet below groundsurface only in boring OW-2, but appears to correlate with similar material found in boringsMW-E3 and MW-Ml 15. Absence of the gray silty clayey fine sand in other borings may bea result of discontinuous deposition or erosion at the Drake Site.
The monitoring wells were constructed of 2-inch I.D. Schedule 40 PVC riser pipe and the testwell was constructed of 6-inch I.D. Schedule 80 PVC riser pipe. Observation well screens were10 feet in length and installed at depths corresponding to the approximate midpoint of thescreened interval of the test well. The test well screen was 70 feet in length and installed at adepth of 15 to 85 feet. All wells were developed by surging, bailing and pumping.Development continued until little or no sediment entered the well, and temperature, pH andspecific conductance stabilized. Following a failed step test of TW-1 on August 9, 1991, thewell was redeveloped by treatment with chlorine and acid, surging with a bristled surge block,and pumping.
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9.3 Aquifer Testing
Gannett Fleming determined specific capacity, hydraulic conductivity and transmissivity of thesand and gravel alluvial aquifer by means of in situ hydraulic conductivity testing, a stepdrawdown test, a 72-hour constant rate pump test and a recovery test The in situ hydraulicconductivity of all four wells was measured by instantaneously changing well water levels viathe insertion or withdraw of a solid PVC "slug.* Based upon this slug testing hydraulicconductivity was found to range from an average of 4.8 feet/day at TW-1 to an average of44.3 feet/day at OW-3.
Following redevelopment, a step-drawdown test was performed at TW-1 on August 23, 1991.The test well was pumped for four consecutive 60-minute periods at successive rates ofapproximately 29, 34, 40 and 46 GPM. Specific capacity of the well decreased from1.3 GPM/ft to 0.9 GPM/ft as the pumping rate increased. True well efficiency, based uponmodified nonequilibrium equations described by Jacob, was estimated to be 86%.
%
From August 26 through August 29, 1991, a 72-hour 35-GPM constant rate pump test wasconducted at TW-1. During the pump test, pressure transducers and data loggers were used tomonitor drawdown at the following wells: TW-1, OW-1, OW-2, OW-3, MW-M4, MW-M125,MW-E3, MW-M18, MW-M15 and MW-115. No correction of pump test data was deemednecessary to account for rhythmic fluctuation of water levels, unidirectional trends of waterlevel, or weather condition effects on water levels.
Pump test data were analyzed using Theis, Dupuit and Bouwer-Rice methods. Hydraulicconductivities ranged from a value of 1,160 feet/day at MW-M109 to 7 feet/day at wellMW-M5. Results using the Dupuit method are considered to be most accurate as the pump testhad'approached a virtual steady state after 72 hours of pumping.
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Gannett Fleming conducted a recovery test immediately following completion of the 72-hourconstant rate pump test Using the Theis method, hydraulic conductivity was calculated to be16, 31, 37 and 2.3 feet/day for wells OW-1, OW-2, OW-3 and TW-1, respectively.
The Dupuit formula was also used to calculate hydraulic conductivity and transmissivity basedon drawdown caused by the massive dewatering operation begun at the Lock Haven wastewatertreatment plant June 19, 1991. Round 5, 6 and 7 water levels were used to estimate drawdownin wells MW-M124, MW-M122, MW-Ml 19 and MW-M125. The calculations determined thathydraulic conductivities in the vicinity of these wells ranges from 143 to 204 feet/day.
9.4 Groundwater Flow Model•
A MODFLOW model $iin'??ata3 aquifer characteristics of the sand and gravel alluvial materialabove the bedrock. Aquifer testing data from this and previous investigations are used in themodel. The model is calibrated to long-term average water levels at the site. An interfacebetween the MODFLOW model and the MODPATH-MODPLOT program may be used todesign a groundwater extraction system.
A long-term average water level contour map was developed by using groundwater levelsmeasured between October 1983 and October 1991. Since hydraulic conductivities calculatedduring this time period were highly variable, a Kriging procedure was used to developed amatrix of hydraulic conductivity values for use in the MODFLOW model.
A 19 row by 22 column finite difference grid is used in the MODFLOW modeL Constant headboundary conditions are established along the perimeter of the rectangular grid. • The modelfeatures one layer representing the sand and gravel alluvial material above the bedrock. Thelayer is unconfined with bottom elevation taken from Plate 3-8, which was hand drawn fromboring logs prepared during hydrogedogic studies for both the Drake and the American Colorand Chemical sites. Recharge in the MODFLOW model is set at 14.5 inches/year except in
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Zone I where a higher rate of 26.5 inches/year is used to account for lack of surface runoff andtranspiration.
The strategy for model calibration consisted of repeated trial and error adjustment of theMODFLOW model to determine what hydraulic conductivity values would most accuratelyreproduce long-term average groundwater elevations. Each calibration trial represented a steady-state solution obtained from the model using the specified recharge rates, boundary conditions,and bottom of layer elevations. The initial hydraulic conductivity value were those obtainedfrom Kriging. These values were varied until acceptable agreement between long-term averageand simulated groundwater levels was obtained. Final horizontal hydraulic conductivity valuesranged from 0.1 to. 300 feet/day.
A copy of the MODFLOW output file for the calibration run are presented in Appendix K~ Atotal of 33 observation points were used to check me accuracy of model predictions. These 33observations, shown in Table 8-2, consisted of data from 19 Drake wells, 13 ACC wells* andthe staff gage on the west abatement of the Castanea Bridge over Bald Eagle Creek. There wasa very high linear correlation ( =.96) between model predictions and observed values. Onaverage, the model slightly overestimated groundwater elevations. For 26 of the 33 observationpoints, the MODFLOW ftimiilafffd values were within one foot of observed values. The largestdifference between observed and simulated values was 1.36 feet, which occurred at well MW-28in the American Color and Chemical area. The groundwater levels in this area exhibit acomplex flow path that could not be completely reproduced with the MODFLOW model.Because this area is approximately 800 feet from Zone n, this discrepancy should notsignificantly impact use of the model's use as a tool to evaluate alternative extraction wellsystems.
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rcis
Bierschenk, W.H., 1964, Determining well efficiency by multiple step-drawdown tests,Publication 64, International Association of Scientific Hydrology.
Bouwer, H. and Rice, R.C., 1976, A slug test for determining hydraulic conductivity ofunconfined aquifers with completely or partially penetrating wells, Water Resources Research,12:423-28.
Driscoll, F.G., 1986, Groundwater and weUs, 2nded., Johnson Division, St Paul, Minnesota.
Duffield, G.M. and Rumbaugh, m, J.O., 1989, Aqtesolv: aquifer tess solver, version 1.00,Geraghty and Miller Modeling Group, Reston, Virginia.
Dupuit, J., 1863, Etudes theoriques etpratiques sur le mouvement des eaux dans les canauxd&couverts et a. trovers les terrains permeables, 2eme edition, Dunot, Paris.
Environmental Science and Engineering, Inc., and Chemical Waste Management, Inc., 1985,Ammended closure plan, American Color and Chemical Corporation, Lock Haven,. PA, Preparedfor American Color and Chemical Corporation, December, 1985, ESE Project No. 85271-0200.
Environmental Research and Technology, Inc., September 1986, Supplemental hydrogeologicinvestigations of the American Color and Chemical Site, Lock Haven, Pennsylvania.
Gannett Fleming, Inc., December 1990, Final quality control and sampling plan, DrakeChemical Superjund Site, Lock Haven, Pennsylvania.
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Gannett Fleming, Inc., November 1991, Draft treatabiUty testing report, Drake ChemicalSuperjund Site, Lock Haven, Pennsylvania, Prepared for the U.S. Army Corps of EngineersContract Number DACW45-90-C-0117.
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Kniseman, G.P. and de Ridder, N.A., 1990, Analysis and evaluation of pumping test data, 2nded,, International* Institute for Land Reclamation and Improvement, Publication 47, TheNetherlands.
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Pollock, D.W., 1989, Documentation of 'computerprograms to compute and display pathUnesusing results from the U.S. Geological Survey modular three dimensional finite-differencegroundwater flaw model, Including Open File Report 89-622, Published by the U.S. GeologicalSurvey.
Remcor, Inc., 1991, 1990 ground water monitoring report, American Color and ChemicalCorporation.
Taylor, L.E., W.H. Werkheiser and M.L. Kriz, 1983, Groundwater resources of the westbranch Susquehanna River Basin, Pennsylvania, Water Resources Report 56, Commonwealthof Pennsylvania Department of Environmental Resource Bureau of Topographic and GeologicSurvey. 143 pp.
Theim, G., 1906, Hydrologische methoden, Gebhardt, Leipzig.
Theis, C.V., 1935, The relation between the lowering of the piezometric surface and the rateand duration of discharge of a well using groundwater storage, Transactions, AmericanGeophysical Union, Washington, D.C., pp. 518-524.
U.S. Army Corps of Engineers, July 2, 1990, Scope of services for Drake Chemical SuperjundSite, Lock Haven, PA aquifer pump test and groundwater treatabiUty study.
U.S. Environmental Protection Agency, September 29, 1988, Record of Decision, DrakeChemical Site, Lock Haven, Pennsylvania.
U.S. Environmental Protection Agency, 1990, EPA handbook, groundwater, volume 1: groundwater and contamination, Office of Research and Development, EPA/625/6-90/016a.
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