United States Department of the Interior'• GEOLOGICAL JURVEYHATER RESOURCES DIVISION lDA &208 Carroll Building

( 8600 Ln Snlle RoadTowaon, Maryland 21204

November 3, 1983

Ms. Stephanie Del Re'U.S, Environmental Protection AgencyOffice of Haste ProgramsEnforcementWashington, D,C, 20460

Dear Ms, Del Re1: Rui Army Creek Landfill

Don Vroblesky has completed hia review and discussion of the existingdata concerning Array Creek (Llangollen) landfill, New Castle County,Delaware, as part of the U.S. Geological Survey hydrogeologic supportfor the U.S. Environmental Protection Agency. The report isattached, As requested by Roy Shroclt, his packet also containsxerox copies of most of the cited references.

Enclosure

cc: Roy ShrockPhiladelphia, Pennsylvnnia

REVIEW AND DISCUSSION OF EXISTING DATA

CONCERNING ARMY CREEK (LLANGOLLEN) LANDFILL

AND DELAWARE SAND AND GRAVEL LANDFILL,

NEW CASTLE COUNTY, DELAWARE

Don Vroblesky, HydrologtstU.S. Geological Survey, Towson, Maryland

A.This review has been prepared by the U.S. Geological Survey

as part of the cooperative hydrogeologie support for the U.S.Environmental Protection Agency (EPA) Enforcement Investigationand a l t e r n a t i v e s assessment. The purpose Is to summarizeprevious efforts and to l i s t any additional tasks related tohydrogeologv w h i c h need to be p e r f o r m e d to f u l l y assess thecontamination of the soil, surface-water, and ground-water at theArmy Creek Landfill and the Delaware Sand and Gravel Landfill forthe purpose of selecting optimum remedial actions. Cost analysesand p o l i t i c a l o p p o s i t i o n to s p e c i f i c o p tions are not addressedhere.

B. EBEYJQUSS e v e r a l r e p o r t s have been p u b l i s h e d on the ground-water

hydrology in the general area of the Army Creek Landfill. Thesereports Include:

1. Water level measurements (Boggess and Coskery, 1956,Coskery, 1957, 1960, 1961a, 1961b; Coskery and Rasmussen, 1958;M a r i n e , 1955; M a r i n e and Rasmussen, 1954; M a r t i n and Denver,1982).

2. A h y d r o l o g i o a t l a s of the W i l m i n g t o n area by the U.S.G e o l o g i c a l Survey for the p e r i o d 1950-1961 (Adams and Boggess,1964).

3. Reports on the g r o u n d - w a t e r resources of Delaware(Marine and Rasmussen, 1955; Sundstrom, P i c k e t t , and V o r r i n ,1975; Roy F. Weston, Inc., 1970; W o o d r u f f , 1969, 1970) and ofnorthern Delaware s p e c i f i c a l l y (Martin, In review, Rasmussen andothers, 1957; Sundstrom and Pickett, 1971; Sundstrom and others,1967).

4. A report on the water resources of the Delmarva Peninsula(Gushing and o t h e r s , 1973).

A d d i t i o n a l r e p o r t s have been p u b l i s h e d on the s p e c i f i c

hydrology of the Anny Creek L a n d f i l l s i n c e g r o u n d - w a t e rcontamination was f i r s t detected in 1971. These reports include:Apgar (1975, 1976); Apgar and Langmuir (1971); Baedecker andApgar (in press); Baedecker and Back (1979a, 1979b); Clark(1979); DeWalle and Chian (1981), Fiore and Satterthwaite (1973)-,Geraghty and M i l l e r , Inc. (1982); Lee (1981, 1932); Lee andMcGovern (1982a, 1982b); Leis and o t h e r s (1976); M i l l e r (1982);Miller and Sllka (1981); New Castle County (1979); Niesen (1974);NUS Corporation (1983); Roy F. Weston, Inc. (1972, 1973a, 1973b,1973c, 1973d, 1973e, 1974a, 1974b, 1974c, 1975a, 1975b, 1976,1977a, 1977b, 1978, 1980a, 1980b, 1980c, 1981); Webb (1974), andSatterthwalte and Apgar (1972). Some of the consulting reportsby Roy F. Weston, Inc., and by Ecology and Environment, Inc.,have been p u b l i s h e d by specific authors. These references arecited under the author's name. Specific contents of the abover e p o r t s are d i s c u s s e d where a p p r o p r i a t e in the f o l l o w i n gsections. Complete references are cited at the end of this.report.

C. SQDBCLE CQHIBQ1 MEASURES 1DEHUEJED IB IHE BAJiffii1. CJaaiir.fi al liazatdaua waste laadlill la iaslude mfias.jjr.es.d£.s.L£U£Ld La miaimize. ialili.ta.iiaa a.ad cr.fi.i2.ai saaiatDiaaaimxgraiiaiua. Surface capping (synthetic or natural cover materials)i b. Regrading to control surface-water runoff

o. Revegetation

Requ irements:1 ) E s t i m a t e o f t h e c o n t r i b u t i o n o f v e r t i c a li n f i l t r a t i o n to leachnte generation.

2) Estimate of the amount of water that w i l l enter therefuse after reduction of i n f i l t r a t i o n .

A v a i l a b l e data:Based on hydrologic mass balance calculations, Lee andMcGovern (1982a, p. 4,3) has e s t i m a t e d that o n l y 0.4% of thewater moving t h r o u g h Army Creek l a n d f i l l is from v e r t i c a li n f i l t r a t i o n . This fig u r e is probably low because the data usedin the mass b a l a n c e c a l c u l a t i o n appear to be or the a q u i f e rt h i c k n e s s and not for the s a t u r a t e d l a n d f i l l t h i c k n e s s . A morecorrect statement would be that only 0.4& of the combined ground-water flow through the f i l l and through the iqu|f:r immediatelybeneath t h e f i l l i s d e r i v e d from v e r t i c a l i n f i l t r a t i o n o fp r e c i p i t a t i o n through t h e f i l l . Baedeaker a n d Apgar ( i n press,p.5) e s t i m a t e that 70% of the leachate general!on o r i g i n a t e s asi n f i l t r a t i n g p e r c o l a t i o n a n d o n l y 301* from l a t e r a l i n f l o w .

Thicknesses of s a t u r a t e d r e f u s e are shown Ni e s s e n(1974), New C a s t l e County (1979), and D e W a l l e and C h i a n (1981),T h e c o n t r i b u t i o n o f i n f i l t r a t i o n t o g e n e r a t i o n o f l a n d f i l ll e a c h a t e can be c a l c u l a t e d based on these f i g u r e s , An e s t i m a t eo f t h e a m o u n t o f p r e c i p i t a t i o n i n f i l t r a t i o n a n d g r o u n d - w a t e rI n f i l t r a t i o n t o t h e f i l l i s a l s o g i v e n i n R o y F , Wcston(1974).P a p e r s by C l a r k (1979), Roy F. W e s t o n (1974), and N i e s e n (1974)

o r, r, - r ' : f.f\'• n 11 u v, -j ,•' <j o

contain e s t i m a t e s of the amount of water that w i l l enter therefuse after reduction of infiltration.

Data deficiencies:None.

2. EfuliflJ. fijjcfuaUaii &ad di£fifts.iU al aaslaa iihas.a beJ.aw.. .

a. On-site in a newly constructed landfillb. Off-site in a suitable facility

Requirements:1) Suitable location to receive the wastes2)Evaluation of the p o s s i b i l i t y of releasing

contaminants during handling and transport.3) Location of areas within the fill containing wastes

disposed of below the seasonal water-table.

Available data:Of primary hydrogeolog ic importance in d e t e r m i n i n g

possible locations for a new onsite l a n d f i l l is the configurationof the clay layers and the water table. The thickness of thu redc l a y c o n f i n i n g u n l t a t the Army Creek L a n d f i l l s i t e is shown in areport by Roy F. Weston (1973a). Geologic c o n d i t i o n s elsewherein New Castle County are discussed in reports cited in B3 above.

The p o t e n t i a l for release of c o n t a m i n a n t s duringhandling and transport depends on the chemical s t a b i l i t y of wastematerial. Although leachate tests have not been done on thewaste material, the presence of a plume of contaminated ground-w a t e r i n d i c a t e s t h a t t h e m a t e r i a l i s h i g h l y l e a c h able.Excavation and h a n d l i n g t e c h n i q u e s would have to includerainwater d i v e r s i o n and control of surface-water runoff.

A p a p e r by Niessen (1974) c o n t a i n s maps showing thebottom of the f i l l , the thickness of the f i l l , the thickness ofsaturated refuse in January, 1974, and the e l e v a t i o n of the watertable. Most of these maps can also be found in New Castle County(1979), and DeWalle and Chion (1981). These data can be usedalong with w a t e r - t a b l e e l e v a t i o n maps of the wet season todetermine the location of areas w i t h i n the f i l l containing wastesdisposed of below the seasonal water-table.

Data def ic lend es :None. An a l t e r n a t i v e apparently not c o n s i d e r e d is

removal of the waste b u r i e d beneath the seasonal water-table to ahydrogeological ly sound, temporary storage area. The excavationscould then be backfilled to above the seasonal w a t e r - t a b l e , andthe waste m a t e r i a l could b e r e t u r n e d t o t h e o r i g i n a l f i l l a n dreburied. The same r e q u i r e m e n t s and a v a i l a b l e data as abovep e r t a i n t o t h i s a l t e r n a t i v e .

I n •; - •111 u o 'j

3 . JasiiUJlulittn pj LWdJiau walls. wiihla iliaReq;il rements i

1) Evaluation of the degree of treatment required tobring such presumably high concentrations to withinacceptable limits for discharge!

2} E v a l u a t i o n of the p o s s i b i l i t y of re left singcontaminants during the well i n s t a l l a t i o n process.

3) EvnlUBtlon of the effects of mixing of the leachatewith uncontaminated, oxygenated ground-water inducedto move into and through the f i l l material as aresult of the pumping.

Available data:This option has been discussed briefly by Clark (1979),

suggesting that the leaehate could be discharged into a countysewer. It has also been discussed indirectly by Roy F. Wcston(1974) in relation to dralnlines. The report discusses optionsof what to do with the leaehate, Including rec Irculat ion andspray irrigation. Treatabillty studies of the leaehate collectedfrom down-gradient wells has been done (Fiore and Satterthwal te,1973), The d e t e r m i n a t i o n was that the only i n t e r i m treatmentfeasible would be l i m e a d d i t i o n , f i l t r a t i o n , and f i n a l pHadjustment. This treatment would substantially reduce the amountof metals in solution, but would not effectively reduce COD andammonia c o n t a m i n a t i o n . The study determined that if waterquality s u i t a b l e for recharge of an aquifer used for publicsupply is desired, then additional treatment must be used, suchas a c t i v a t e d carbon, ion exchange, and r e v e r s e osmosis, Thesemethods all concentrate contaminants in the spent carbon or brinesolution rather chemical or biological degradation of them,c r e a t i n g a p r o b l e m of r e s i d u e d i s p o s a l . Leaehate collecteddirectly from the f i l l will be more highly concentrated that thesamples for the treatability study. Extraction analyses done onleaehate taken d i r e c t l y from the f i l l ( l e t t e r to Harry Otto,DNREC, from USEPA Southeast Research Lab., 5/18/74) show largeamounts of organic acids and industrial chemicals, particularlyphenols, r e l a t i v e to the other s i t e wells. The amount oftreatment req u i r e d for the leaehate w i l l therefore be greaterthan indicated by the study.

The p o s s i b i l i t y of r e l e a s i n g c o n t a m i n a n t s d u r i n g thewell I n s t a l l a t i o n process depends on the l e a o h a b i l i t y of them a t e r i a l , w h i c h has been discussed in "C2" above. W e l lI n s t a l l a t i o n methods must be chosen which u t i l i z e as l i t t l e wateras possible in order to minimize leaehate generation.

The effects of m i x i n g oxygenated water w i t h oxygen-d e f i c i e n t l e a e h a t e o n o r g a n i c c h e m i s t r y i s d i s c u s s e d i nBaedecker and Apgar (in press) and Baedeoker and Back (1979a,1979b). If most of the Iron in the e x i s t i n g leaehate plume isdue to d i s s o l u t i o n of aquifer matrix by leaehate, as suggested byBnedecker and Apgarlin press), then water flowing i n t o the f i l l ,m i x i n g w i t h l e a c h n t e , a n d b e i n R removed b y w e l l s i n t h e f i l lw o uld be e x p e c t e d to c o n t a i n s u b s t a n t i a l l y less iron than Is

i o

found in wells pumping leachatt? from the aquifer.

Data deficiencies:Treatability studies of leachate immediately adjacent

to or preferably in the f i l l m a t e r ial are needed to evaluate thisoption. Suitable methods of disposal of the contaminantsconcentrated by the a d d i t i o n a l t r e a t m e n t methods must bedetermined.

4. Cat jf&aiioERequirements:

1) I n d i c a t i o n s that gasses are present in s u f f i c i e n tamount to be hazardous.

Available data:OVA readings at the well heads in November, 1981

(Ecology and E n v i r o n m e n t , 1982) show high values at the ArmyCreek l a n d f i l l , i n d i c a t i n g that methane and other volatileorganic gasses ure present in explosive concentrations at severalwells.

Data deficiencies;None concerning hydrogeo logy, although a risk

assessment should be determined before i n i t i a t i n g additionald r i l l i n g , grading, or excavation at the f i l l .

5. HaRequirements:

Assessment of the t i m e neooessary to d e p l e t e thel a n d f i l l of leachable m a t e r i a l .

Avallable data:The a v a i l a b l e data is largely q u a l i t a t i v e . The time to

r e s t o r e the a q u i f e r has been e s t i m a t e d at 25 years (New CastleCounty, 1977), but it has been observed, for example, that somelandfills from the days of the Roman Empire are s t i l l producingleachate (Freeze and Cherry, 1979, p. 437). Baedecker and Apgar(in press, p,24) p o i n t out t h a t the r e f r a c t o r y n a t u r e of manyorganic compounds and t h e i r tendency to remain coated on aquiferm a t e r i a l s may cause contamination problems long after theconcentrations of major,inorganic c o n s t i t u e n t s return to pre-landf i 11 condi t ions.

Data d e f i c i e n c i e s :The amount of leaehate tc be generated and the time

ncocessary to d e p l e t e the l a n d f i l l of l e a c h a b l e m a t e r i a l areunknown a n d p o s s i b l y u n k n o w a b l e f a c t o r s . I f t h i s o p t i o n i schosen, it must be assumed th a t the n q u i f e r w i l l be unusable forat least s e v e r a l g e n e r « t i o n s .

i l\ 2* j i "/

D. QEEiSIUi CQHIEQL ME&SUBES 1DENTJEJED IN IHE &AMP.1i .Ha. Milan.*

Requirements: \1) Rate of ground-water movement2) Rate of leachate input to ground-water system3) Rate of attenuation of pollutants4) Rate of mechanical dispersion of pollutants5)General behavior of contaminants in ground-water Ly.item,

Available data:This option relys on. natural attenuation and dispersion

of the leachate by the aquifer. The rate of ground-watermovement depends on aquifer hydraulic conductivity (k) and on thehead gradient (I): velocity=KI. Ground-water flow velocities andtravel times between the Llangollen l a n d f i l l and nearby majorproduction wells have been calculated (Roy F. Weston, 1973a);however, they were based on head gradients for 1972 and probablyneed to be reevaluated based on more recent head data and updatedtransmissivity values. The head gradient can be determined fromwater table and plezometric maps. L i m i t i n g the data to thosewells screened at approximately the same depth below the watertable w i l l reduce the effects of v e r t i c a l flow on the headgradient calculation. Water table or piezometric maps can befound for specific years in almost all of the reports on thesit e . The h y d r a u l i c c o n d u c t i v i t y is a f a c t o r r e l a t e d to theaquifer matrix. It can be computed from transmissity by dividingtransmissivity by the thickness of the aquifer. Transmissivitiesbased on pumping and recovery tests have been calculated for thestudy area (Roy F. Weston, 1973b). The thickness of the aquifercan be found in boring logs (in EPA f i l e s , P h i l a d e l p h i a ) or canbe estimated if necessary.

The rate of leachate input to the ground-water is afunction of the amount of water e n t e r i n g the f i l l and of theleaohability of the refuse. The amount of water(Q) entering thef i l l from horizontal flow can be calculated from Darey's Law:Q=KIA, where A= a c r o s s - s e c t i o n a l area of the saturated wastethrough which water flows. K and I are calculated as above. Thearea (A) can be d e t e r m i n e d from maps of the thickness ofsaturated refuse (found in Niessen, 1974; New Castle Co., 1979,DeWalle and Chian, 1981). The amount of v e r t i c a l i n f i l t r a t i o ncan be calculated as discussed in C-l above.

Although the t e a c h a b i l i t y of the waste is an unknownfactor, a q u a l i t a t i v e measure of the amount of leaohate beinggenerated can be determined based on the amount of water enteringthe f i l l and the known c o n c e n t r a t i o n of c o n t a m i n a n t s in theground water. This is p r o b a b l y a d e q u a t e for purposes ofdetermining the impact of a "no-notion" decision.

The r a t e of a t t e n u a t i o n o f o r g a n i c c o m p o u n d s Inl e a c h a t e moving through the a q u i f e r at L l n n g o 1 1 en l a n d f i l l hasbeen estimated by Webb (197-1) and DeWalle and Chian (1981), Thedegree of d i l u t ' i o n duo to d i s p e r s i o n can be c o m p u t e d u s i n g ,,c h l o r i d e as the c o n s e r v a t i v e species. C h l o r i d e analyses from

wells at the site are available for calibration for each yearfrom 1973 to 1983. A summary of chloride analyses for four wellsat the site can be found in Baedecker and Apgar (in press, Fig.6). A cross-section ot the c h l o r i d e plume in mid 1973 showingmovement through the punctured clay is shown in DeWalle andChlan (1981).

The general behavior of the organic contaminants in theaquifer at Llangollen l a n d f i l l is discussed in papers byBaedecker and Apgar (in press) and Baedecker and Back (1979a,1979b).

Data deficiencies:None

Q-C BE£s.£nlRequirements :

1) Determination of optimum pumping rates and wellspacing.

2) E v a l u t i o n of the e f f e c t s of Increased pumpingon the amount of uncontaminated water wasted.

Available data:Appropriate hydrogeologio parameters can be calculated

as in "Dl" above. The parameters can be used to calculatedrawdown curves. An a l t e r n a t i v e approach is to use an existing2-D ( M i l l e r , 1982) or quasi 3-D ( M a r t i n , in review) ground-waterflow model of the area to simulate the various pumping scenarios.

Data deficiencies :If one of the existing f low-model F is used, then It

would be neooessary to reduce the g r i d size and to i m p r o v e thec a l i b r a t i o n . Stream bed leakance Is a f a c t o r that is not welldefined end may have to be manipulated to f a c i l i t a t e calibration,

3. ir.fi.aj.ni6.at oj £r_au.njd-imi.fi.r tuojeatj w.e_u diKhauss, ia air_£ftime.ui. clam at Lhe wumiugj.au SKD/IE*.

Requirements;Treatabillty tests on the leachate.

Aval t a b l e data :T r e a t a b i l i t y tests of the Llangollen l a n d f i l l leahate,

as e x t r a c t e d from d i s c h a r g e w e l l s , have been done (Fiore andSatter thwai t e, 1973). The conclusions are c i t e d in C3 above.The study was based on analyses from 1973. More recent analyses(Baedecker and Apgar, in press) show that a l t h o u g h the majorinor g a n i c c o n s t i t u e n t s have changed l i t t l e , the number of organiccompounds and the o r p a n i o .carbon c o n t e n t of the l e a c h a t e haveg r e a t l y deer eas ed.

Data dof io ieno ies :U p d a t e d t r e a t a b i l i t y t e s t s need t o b e done t o

" k 1 1 0 a j } 3

adequately evaluate the leachate treatment options. Ifadditional treatment Is deemed neecessary, such as activatedcarbon, ion exchange, or reverse osmosis, then a suitable methodof disposal of the contaminants concentrated by such treatmentmust be decided on.

4. lr.aatn)£u,i al aumi£i.fia.L iadjjs.uial.* a.ad ar.LKfl.ia walluuuMJ s. al£££l£d by caniaroiaaai r_ejLaa.5.as. itam lit DeJ.a.w.ar.eaad Ctfutl and AUDX Ctaals

Requirements:Same as "D3" above.

Available data:Same as "D3n above.

Data def iciencies;Same as nD3n above.

ai lafitaaty ivUl di&£ua.U£.s. iar. iipj.io.wiiu ir.&fl.ia)£au.

Requirements:Same as "D3" above.

Av a i l a b l e data: 'Same as "D311 above.

Data def iclenc i es :Same as "D3" above r e g a r d i n g a q u i f e r r e i n j e c t l o n .

Industrial use w i l l depend on the s p e c i f i c i n d u s t r i a l toleranceto the type of w a t e r and on the q u a l i t y of the r e s u l t i n gwastewater.

6. MiniiDLziwj pji-s.ii£ fitQjJDJhjyftlat flumpoge ta mlaimLza

Requirements:Determination of the optimum pumping balance between

ground-water i n t e r c e p t i o n wells and supply w e l l s r e q u i r e d tom a i n t a i n maximum supply with m i n i m a l withdrawal for d i v e r s i o n ofcontaminat ion.

Aval 1 ab le data :This option can be addressed in the same manner as "D2"

above.

Dnta def ic i cnc i es :Same ns "D2" above.

R 0 L 0 S 7 l|

1. Aiandaumaul oj roimJLfiiBiiL. iDLdjisltifll* and ctLxaie. wallajiCBlifis. Blie_c.ie_d. Jm fittauminani telejufis. learn Itie DeJ.fl.imtc Sandami Cw.y.fii amd AJMD^ Cttds

Requirements :l)The p o t e n t i a l for contamination of these supplies2) The availability of an alternate water supply source

Available data:The potential for contamination can be qualitatively

determined as described in "Dl" above. The a v a i l a b i l i t y of analternate ground-water supply can be addressed using the ground-water flow model by Martin (in review). The modeled area isdivided into v e r t i c a l layers, so i n d i v i d u a l layers can bestressed and the resulting effects of the stress on the otherlayers can be seen. One scenario tested by the model was theeffects over a 25-year period of the decrease in purnpage by Amoooin October, 1980. The simulation predicted a head recovery of120 feet in the lower aquifer.

Data deficiencies;If the model by M a r t i n (in review) is used, then the

grid should be reduced and the effects of local geology should beincorporated.

8. B££ha.Lg£ b.airj.£r. fcjj fitiulLy ialuLLaa lie.ni Ihs. waltt i&lUs. Lattifi. Eaiofljaj: Aaiiilar. icmth al lue tusliaE

Requirements :1) Areal d i s t r i b u t i o n of head differences between the

water table aquifer and the Potomae Aquifer.2) Chemical analyses from both aquifers in the area of

the proposed recharge barrier in order to determine theeffects of m i x i n g of the two types of water onp r e c i p i t a t i o n of solids and well clogging.

3) Evaluation of the drawdown in the water-tableaquifer as related to possible changes in the directionof flow and the transport of contaminants in the water-table aquifer.

4) Amount of recharge required to a t t a i n the desiredhead dis tr ibut ion.

Available data:The a v a i l a b l e data on the water-table aquifer appear to

be l i m i t e d to the northwest of the f i l l (upgradi ent ). The FITreport (Lee and McGovern, 1982a) shows some w e l l s south of thef i l l which have no counterpart in the legend, such as wells R-2,R-3, Dl , D2 , etc., but apparently these wells are e i t h e r f i l l e din or n o t h i n g is known about the depth.

Data def io i one i esIf R-2, R-3, Dl , D2 , e t c . are of unknown d e p t h or are

deep, then a d d i t i o n n l datn must be obtained south of the recoveryw e l l s y s t e m . T h i s i n v o l v e s i n s t a l l a t i o n o f w a t e r - t a b l e

"piezometers" and at least one or two wells from which watirtable samples can be obtained for analysis.

9. RtslarjUifta ol Atrny CtaaJs eiDJi Atnm fay JJjs dmicimu S.LCJ. Unai ifflfi&jBl uaa MfiJittftd as. a tamii aiItfiJD Ulfi,

Requirements:1, Evaluation of leachate Impact on surface-water bodies,2. Evaluation of methodology of restoration

Available data:The limited data available indicate that stream-water

concentrations of iron and manganese increase significantly dueto discharge from recovery wells and that concentrations of iron,cadmium, chromium, lead, copper, nickel, zinc, and s i l v e r areover the maximum value for protection of fresh-water aquatic life(Lee and McGovern, 1982a).

Data Deficiencies:Stream-sediment samples need to be collected and

analyzed in order to determine the value of this option. If theresults indicate that s i g n i f i c a n t contamination has occurred,then r e s t o r a t i o n o p t i o n s need to be addressed, such asdetermining whether dredging will release iuur ; contaminants thanno-action. If dredging is decided on, then p suitable method ofdisposal of the waste is needed.

E.

In order to e v a l u a t e any of the o p t i o n s r e q u i r i n g wastetreatment, updated t r e a t a b i l i t y tests need to be done. If It isfound that t r e a t m e n t m e t h o d s such as a c t i v a t e d carbon, ionexchange, or r e v e r s e osmosis are necoessary, then a s u i t a b l emethod of disposal of treatment residue must be determined. Ifexisting ground-water flow models are used to evaluate options,the g r i d size w i l l have to be reduced and the framework w i l l haveto be updated to account for localized geology; however this canbe done without a d d i t i o n a l field work.

Additional fieldwork is neccessary to determine the effectof l a n d f i l l and leachate recovery operations on surface-waterbodies. S t r e a m - s e d i m e n t samples need to be c o l l e c t e d andanalyzed. If the results indicate that significant contaminationhas occurred, then restoration options need to be addressed, suchas determining whether dredging w i l l release more contaminantsthan no-action. If dre d g i n g is decided on, then a suitablemethod of disposal of the waste is needed.

The amount of i n f o r m a t i o n known about w e l l s R-3, R-4, Dl,etc, is not clear from the l i t e r a t u r e . If these arc not u s a b l ew e l l s s a m p l i n g t h e w a t e r - t a b l e a q u i f e r , then a d d i t i o n a li n f o r m a t i o n hat to be cohered in order to e v a l u a t e t h e o p t i o n of

c a g r o u n d - w o t e r d i v i d e by g r a v i t y i n j e c t i o n r e c h a r g e

10

water This r e q u i r e s t he i n s t a l l a t i o n o f a d d i t i o n a l?pleVo'meterS" and well(s) in the area south of the leaehaterecovery welIs.

n 11 w L. •*/ j i I

APPENDIX - ANNOTATION OF SELECTED LITERATURE

ai Gc.ajjad=.Halfi.r. Co.aXamiaaUfi.aAlias laud Hllb. lat Ua.afiaJL.lfca Uadim* New CaaULe Cajiau*DfilOtfata (Satterwaite and Apgar, 1972).

The report c o n t a i n s maps showing the bottom of the upperPotomac confining beds in the landfill v i c i n i t y , the bottom ofthe Columbia Formation in the l a n d f i l l v i c i n i t y , an isopach ofthe upper Potomac c o n f i n i n g bed, the plezometrlc levels forSept., 1972, the theoretical ground-water flow pattern in Sept.,1972, and the known extent of contamination in Sept., 1972. Alsopresented are presumed background water quality analyses.

Two papers by M. A. Apgar (1975, 1976) suggesting that theunderlying clays of the Potomao Group were probably removed inplaces during development of the landfill.

Ground Haiat CaaUrolaaUan AiiftfliaUd with ike.LaadiiUL Mas Cas.Ua Cajialit* DsJwata* Exum ai CaaUmiaaUaa aadELOJ!O.S£d CattmJJfi EtasejluLas.* Jaaiiacji iiii (Weston, 1973a).

This report contains maps of the thickness of the redc o n f i n i n g u n i t at the top of the Potomac Formation in thevicinity of Llangollen landf i l l , and ground-water flow directionsand water quality (9/72) in the Upper Potomac aquifer. Ground-water flow v e l o c i t i e s and t r a v e l times between the Llangollenl a n d f i l l a n d m a j o r p r o d u c t i o n w e l l s i n t h e v i c i n i t y a r ecalculated based on head gradients for 1972. Chemical analysesi n c l u d e c h l o r i d e . T he p r o p o s e d c o r r e c t i v e m e a s u r e s were" toi n s t a l l w e l l s a n d p i e z o m e t e r s t o d e t e r m i n e a q u i f e rcharacteristics and to intercept the contamination.

E.y.aj,iia.Uaa al Gtauiui Haiti. Aiiaile-bUlli aadU.aa£allfi.a Ar_s.a* (Weston, 1973b)

The report contains a q u i f e r t ransmiss i vi t ies and storagecoefficients calculated from pumping and recovery tests and a mapshowing the contaminated area. The recommendation was to reducethe pumping rates In existing wells.

me.n3ar.tt.udun) la UaJu aad ai.he.ts. Itam jy*. BJ.. Bcj Lt He.ai.aa* Jas 11 tuiu 1211*The memorandum discusses the p o s i t i v e and negative impacts

of several a l t e r n a t i v e s : leachate pumping and discharge w i t h notreatment; pumping and treating to remove metals only; pumpingand t r e a t i n g for metals and ammonia; s u p p l y i n g d e f i c i t waterquantity to the Artesian Water Company from other water systems;u t i l i z i n g r e t r i e v a l system v / i t h v a r i o u s o p t i o n s ; t r e a t i n gleachate in the a q u i f e r and l a n d f i l l ; p l a n n i n g to pump fromexist ing wel 1 s for e i t h e r treatment and discharge or for d r i n k i n gwater; no action, condemning aquifer.

ai£niQtandJuin 1.0 Er-su&fii Ellas Item j^Ailis. U a. a scale, a laadlUl utainjcai. aU.acaaU.rn* IttIix

The memorandum pr e s e n t s economic and t e c h n i c a l r a t i o n a l e fori n i t i a l r e d u c t i o n o f t h e n u m b e r o f p o t e n t i a l a l t e r n a t i v e s f o r

"' 0i Jj

\

t r e a t i n g the L l a n g o l l e n l a n d f i l l In o r d e r to prevent Itscontamination of a major portable water aquifer. Total haulageof l a n d f i l l materials to new si to, as well as li n i n g the landfillbottom are ruled out as viable solutions. Certain options ofcontrolling water infiltration are discussed.

EacaMJFiore and Satterthwaite,1973).

The report concluded that the only Interim treatmentfeasible would be lime addition, filtration, and final pHAdjustment, this treatment would substantially reduce the amountof metals in solution, but would not ef f e c t i v e l y reduce COD andammonia contamination. The study determined that if waterquality suitable for public supply of aquifer recharge Isdesired, then additional treatment must be used, such activatedcarbon, ion exchange, and reverse osmosis.

EifiJi.miaa.ut EaaslJiUil:! SUid^ Lafl.fib.aU Caulta! £U?J£ei£S. JarLlaiuallau Laud-CLLl (Niessen, 1974).

The report contains maps showing the e l e v a t i o n s of thelandfill floor, the contours of refuse thickness, the elevationsof the top of the clay beneath the f i l l , a p p r o x i m a t e dates ofrefuse emplacement, thickness of saturated refuse, and theelevation of the water table as of Jan., 1974. The reportexamines hydrogeolg ic control alternatives for I s o l a t i n g thel a n d f i l l and i n c i n e r a t i o n al terntit ives for the u l t i m a t e d i s p o s a lof the refuse. It concludes that i t is u n c e r t a i n w h e t h e r thehydrogeologic isolation of the leachate would be effective enoughto restore the a q u i f e r to its previous p u r i t y , and thatuncertainty remains as to the technical f e a s i b i l i t y of certaintypes of incinerators.

Lallan la Du Bam ^ QUO* Ifi-stiaiaU Sauiflas. Sasliaiu DfiJ.aw.ars.Das a time a J. al MaUitaJ. Bas.ajit££i* itaro lue USE£A* Saji.Uiaas.i£ujfii&niDaaiaj. B£i£.au: h LaJjataiau.*, Ac ill liL 12.11.

The l e t t e r c o n t a i n s the r e s u l t s of analyses of leachatesamples by an extraction method designed to separate the leachateinto portions containing n e u t r a l , a c i d i c , and basic compounds.The samples were from a well directly in the f i l l , Recovery Well-3, Well #29, and one of the Artesian Wells. The l a n d f i l lleachate contained large amounts of organic acids and i n d u s t r i a lchemicals. Recovery Well-3 and W e l l #29 were less contaminated.The Artesian W e l l Company well was uncontaminated. The water inthe l a n d f i l l was found to be strongly buffered near a neutralpH, so the l a n d f i l l materials did not constitute an odor problem;however, if they were to escape the l a n d f i l l and encounter anacid environment, as in some cooking, gasses would be released.

Earnings, in i.h£ YiciaiU ol ft SoiJ_d Basl£ Lanjdiill in Ua_ , . .

(Sundstrom, 19V4).This report concluded t h c t (1) the Lower Potomac a q u i f e r was

c o m p l e t e l y d e v e l o p e d or n e a r l y c o m p l e t e l y developed by e x i s t i n g

1 3 A f i 0 C ' J (j 1 9

wells in the area; (2) there appeared to be l i t t l e or no dangerof leachate contamination from the Llangollen landfill to theLower Potomac aquifer in the Midvale-Llangol len Estates area;(3)sal t-wat er contamination from the Delaware River had notoccurred in the Lower Potomac aquifer in the Midvale-LUngollenEstates area; (4) the l i m i t of development of water from the wellsin the Upper Potomac aquifer on a sustained basis was estimated tobe about 6,500,000 gpd or less in the study area; (5) as ofJanuary 1, 1974, the Upper Potomac aquifer had received leachatecontamination in much of a 310-acre area in the study area; (6)the Pleistocene and subcropping Potomac aquifer beneath and southof the l a n d f i l l had received leachate contamination and waspassing the contamination to the Upper Potomac aquifer inplaces; (7) Army Creek had received leachate contamination bydischarge from the Pleistocene aquifer to the creek In places;and (8) a small r i s e in chlorides in the water from the AmocoPolymer Plant well f i e l d wells PW-2 and PW-3 located in thenortheastern p a r t of the area was caused by s l i g h t leachatecontamination rather than salt-water from the Delaware River.

P.te.fia,r.a,l.Q.ti S&.SS.L lac. A tray Ctaajs LLLaneQileaJ. Laadli.llBQJjadUislej. Mo_yfiJTJj£r. ILzlSL. 1.811 (New Castle County, 1977).

The paper discusses v a r i o u s r e m e d i a l a c t i o n scenarios.These are a t t e n u a t i o n ; hydrogeologic controls ( p r e c i p i t a t i o ninfiltration reduction, interception of ground-water inflow, andcollection of leachate w i t h i n the landfill); removal of thesource (transport to Another l a n d f i l l or incineration); hastend e c o m p o s i t i o n ( s p r a y - i r r i gat i on or a n n e l i d i c consumption.Leachate treatment and i n c i n e r a t i o n are examined in d e t a i l .

Er.fiLfie.ejlia£s. iDtaliJ. (New Castle County) 1979).A number of p o s s i b l e s o l u t i o n s were dis c u s s e d at the

rountable m e e t i n g . A t t e n u a t i o n , a n o - a c t i o n a l t e r n a t i v e , wasthe least costly and appeared to have some degree of technicalmerit, but was rejected because of the degree of risk associatedwith Artesian Water Company's well field. Removal of the sourcewas also considered. Moving the l a n d f i l l was considered to bejust t r a n s p o r t i n g the p r o b l e m c o mpounded by the costs ofexcavation, transportation, and r e l a n d f i l l i n g . I n c i n e r a t i o n wasrejected because of high cost and t e c h n i c a l complications.Recycling of the leaohate through the l a n d f i l l was eliminatedbecause Delaware's humid c l i m a t e would result in an ever-i n c r e a s i n g a m o u n i o f l e a c h a t e g e n e r a t i o n . A n n e l i d i cdecomposition wns rejected because it would only be a p p l i c a b l e to10ft o f t h e l a n d f i l l mass. H y d r o g e o l o g i c c o n t r o l w a s t h ea l t e r n a t i v e recommended, which included relocation of recoveryw ells closer to the source, applying a r e l a t i v e l y impermeablecover to the l a n d f i l l surface, and d i v e r t i n g ground-water flowaround the l a n d f i l l .

. .far, AHM CtaeJi Uiudli-U (curk, 1979)The report c o n t a i n s maps showing the p o t e n t lometr io surface

of the Upper Potomac a q u i f e r p r i o r to i n s t a l l a t i o n of c o n t r o lm e a s u r e s ind In M a r c h , 1976 and the extent of c o n t a m i n a t i o n

14

migration as of August, 1973, and May, 1978. Hydrologic controls(precipitation I n f i l t r a t i o n ^eduction, interception of ground-water inflow, and collection of leachate wi'hin the fill) andr e m o v a l o f t h e source a r e d i s c u s s e d . Spray I r r i g a t i o n ,r e cycling, and a n n e l i d i c consumption nre examined as well aspressure maintenance and landfill aeration. The recommendationsare to minimize leachate production by surface capping andu p g r a d i e n t t r e n c h i n g , and m a x i m i z e l e a c h a t e recovery byconstruction of new recovery wells w i t h i n or closer to thelandfill and phasing out the existing recovery system.

dis_cjis.s.Juafi Ihc. £ti£JDLfi.aj ialifuisait ol theThe general behavior of the o r g a n i c contaminants in the

aquifer at Uangollen l a n d f i l l is discussed in papers by Baedeckerand Apgar (in press) and Baedecker and Back (1979a, 1979b). Thereports conclude that beneath the landlfll and ' immediatelydowngradlentof the landltll large amounts iron and manganese ared i s s o l v e d , organic m a t t e r is o x i d i z e d and reduced, oxygen isconsumed, ammonia is adsorbed and n i t r a t e is reduced. Fartherdowngradient , iron and manganese precipitate, less organic matteris oxidized and reduced, and a d d i t i o n a l ammonia is removed byion exchange. Farther downgrad l e n t , the water chemistry ispredominantly controlled by mixing. The r a t i o of reduced nitrogento n i t r a t e can be used to i n d i c a t e the location of reducingfronts as the leachate migrates. One report (Baedecker and Back,1979a) suggests that ethylene may act as a conservative species att h i s s i t e and may t h e r e f o r e be u s e f u l as a tracer in transportmodeling. The paper by Baedecker and Apgar (in press) is ac o n c e p t u a l c h e m i c a l m o d e l u s i n g c h l o r i d e as a conservativetracer ,

Efifl.sltiJLli.ii SLudjt Xat the. Discharge. pJ Caularoiutds.!!I ram A.r_my CteaJj Laadlili Becoicti! iveila* Mew GoalieDfiJ.a_wat£ (Roy F. Weston, 1980).

The report concludes that the State Road Pump Station hadi n s u f f i c i e n t capacity to receive all recover well flows; thatintroduction of all or any recovery well flows to the WilmingtonWWTP would have m i n i m a l i m p a c t on e f f l u e n t q u a l i t y , u n i toperation, or sludge disposal; that the Delaware River would bem i n i m a l l y affected in terms of w a t e r q u a l t i t y by discharge ofrecovery well flows to cither the Wilmington WWTP or Army Creek;and that s e l e c t i v e presentment f a c i l i t i e s were not necessary.

pj lease. Qmnljca in Be. 11 is'aiat ikat a Sal Id Ha.auLandliU (Dewalle and Chian, 1981).

The most significant aspect of t h i s paper is a discussion ofa t t e n u a t i o n of o r g a n i c s in the s o i l at Army Creek L a n d f i l l .Notably, a t t e n u a t i o n tends to decrease w i t h decreasing molecularw e i g h t , p o s s i b l y because of the d e e r e n r . i n g a d s o r p t i v e capacitythat lower molecular w e i g h t compound.1 have w i t h respect to thesoil adsorptive complex. The l i m i t e d r i n t n i n d i c a t e that most oft h e b i o l o g i c a l d e g r a d a t i o n o f t h e l e u c h u t e o c c u r s d u r i n g t h ef i r s t few hundred m e t e r s of p e r m e a t i o n . Trace o r g a n i c s showed a90 * c o n c e n t rat I on r e d u c t i o n for e v e r y 200 m e t e r s permeatec1through the aquifer.

A R 3 - u S 8

Ei.fi.ld JajstaaUsaUftas. eJ. Uaj2a.aUP,Hfi.d tlaio.tilfi.jji w,as.le, £il&s.«. AH dtfl-laeij: SjJUfii oj Atnw Cte.ej$ LaadlUl e.ad Dalai/ate Sand andGULKi laaif.111 (Lee and McGovern, 1982a)

Thfi report contains ground-water e l e v a t i o n maps for 9/72,6/75, 3/76, 7/77, 1978, 2/81, and 11/81. The r e p o r t alsocontains n hydrologic mass balance in Army Creek and DelawareSand and Gravel landfills, chemical analyses for 11/81, and agraph showing the r e l a t i o n s h i p between pumpage and influencedistance.

Ekld HuaaLUBlicas. o_l UasaaltPJLlejj Hazardm Wasla Silti*. HellDti-UitLg ill Dfila_w.aE.£ Sand aod GrJUfil LaOiUHJ, (Lee and McGovern,1982b).

This report discusses the ground-water conditions at theDelaware Sand and Gravel Landfill based on three monitoring wellsand two boreholes in the area. The report contains boring logs,chemical analyses, and water levels for specific wells, as wellas the results of a magnetometer study which was unsuccessful indelineating buried magnetic objects in the drum-pit area.

oJ ike. Basojau-Wfi-U Siilan) I at ibs.LfUUUJLLJU NfiJff Cas.iifi. Cftjialju Dalajyatfi . (Geragh ty and M i 1 1 er ,1982)

The report used a linear gradient model to pre d i c t theeffects of the then "proposed" relocation of the recovery-wellsystem to a site closer to the fill. The conclusions were (1)the ground-water d i v i d e created by the existing recovery-wellsystem appeared to allow two significant segments of the plume toc o n t i n u e to d r i f t toward the A r t e s i o n w e l l f i e l d ; (2) theproposed new recovery-well program could expose the aquifer tomore extensive contamination; (3) a larger number of wells closerto the f i l l would be more effective; (4) a recharge program couldprovide additional d i l u t i o n and diversion.

in. the. £aiojDa£ AsuilfiXSj. Mfi.iv Ca.5li£Cfl-UB.ly.iDfiifliya.ta (Martin, in review).

The quasi 3-d model used s i m u l a t e s flow in three a q u i f e r sand intervening confining units of the Potomac Formation in NewCastle County. The calibrated model was used to evaluate changesin water levels resulting from f i v e possible scenarios of futurepumpage. One of the scenarios was based on the assumption of nochange in pumping rates for the next 25 years. The resultsindicate that the reduction of pumpage at Amoco that occurred inOctober, 1980, should p r o d u c e a head recovery of 120 ft. Otherscenarios arc: (1) assume that Amooo pumpage did not decrease, (2)redistribute pumpage, (3) include expected increases In pumpage,(4) reduction of ground-water use by s u b s t i t u t i o n of others u p p l i e s , such as surface-water or ground-water ou t s i d e the studyarea .

16

BEEEBE1&ESAdams, J.K., and Boggess, D. H., 1963, Water-table, surface-

drainage, and Engineering soils map of the W11m ing ton area,Delaware: U.S. Geological Survey Hydrologlc InvestigationsAtlas HA-79.

Apgar, M.A., 197S, We can't afford to let t h i s happen again,Delaware Conservationist, 9, p. 19-22.

_______, 1976, Recovery of a leachate-contaminated aquiferfor water supply use: National Ground Water QualitySymposium, 3rd, Las Vegas, 1976, Paper presented orally,National Water Well Association.

Apgar, M.A., and Lanagmuir, D., 1971, Groundwater pollutionpotential of a landfill above the water table: Ground Water6, p. 76-96.

Baedeoker, M.J., and Back, W., 1979a, Hydrogeological processesand chemical r e a c t i o n s at a l a n d f i l l . Ground W a t e r 17, p.429-437.

___________, 1979b, Modern marine sediments as a naturalanalog to the chemically stressed environment of a landfill:Journal of Hydrology 43, p. 393-414.

Baedecker, M.J., and Apgar, M.A., in press, H y d r o c h e m i c a lstu d i e s at a l a n d f i l l in Delaware: N a t i o n a l Academy ofScience, 27 p.

Boggesr,, D.H., and Coskery, O.J., 1956, Delaware, in Water levelsand artesian pressures in o b s e r v a t i o n wells in the UnitedStates, 1954: U.S. Geological Survey Water-Supply Paper1321, p. 13-21.

Clark, D.C., 1979, Remedial action a c t i v i t i e s for Army CreekLandfill: Proceedings of the f i f t h Annual Research Symposiumon Solid Waste, Orlando, Florida March 26-28, 1979.

Coskery, O.J., 1957, Delaware, In Water l e v e l s and artesianpressures in observation wells In the United States, 1955,U.S. Geological Survey Water-Supply Paper 1404, p. 13-21.

_________, 1960, Delaware, in Ground-water levels in theUnited sfates, 1956-1957: U.S. Geo l o g i c a l Survey Water-Supply Paper 1537, p. 9-15.

________, 1961a, Water levels in Delaware - 1957: DelawareGeological Survey Water-Level Report No. 6.

_________, 1961b, Water levels in Delaware - 1958s DelawareGeological Survey Water-Level Report No, 7, 17, p.

C o s k e r y , O.J., and R a s r n u s s e n , W.C., 19 5 8 , W a t e r l e v e l s i n

17 ^ ''' 'J'-' 'j (j 3

Delaware - 1956: Delaware Geological Survey Water-LevelReport No. 5.

Gushing, E.M., Kantrowitz, I.H., and Taylor, K.B., 1973, Waterresources of the Delmarva Peninsula: U.S. Geological SurveyProfessional Paper 822, 58 p.

DeWalle, F.B., and Chian, S.K., 1981, Detection of trace organicsin well water near a s o l i d waste l a n d f i l l : Journal ofAmerican Water Works Association, pp. KG6-211.

Fiore, M.E., and Satlerthwaite, W.E., 1973, P r e l i m i n a r yt r e a t a b i l i t y study report: Written correspondence from RoyF. Weston, Inc. to Stephen Kowalchuk Jr., Department ofPublic Works, New Castle County, Delaware, 7 p.

Freeze, R.A., and Cherry, J.A., 1979, Groundwater, Prentice-Hall,Inc., Edgewood C l i f f s , New Jersey, 604 p.

Geraghty and M i l l e r , Inc., 1982, Evaluation of the recovery wellsystem for the L l a n g o l l e n L a n d f i l l , Consultants report byGeraghty and M i l l e r , Inc., for the A r t e s i a n Water Company,Newark, Delaware, 28 p.

Jordan, R.R., 1976, The Columbia Group (Pleistocene) of Delaware,Pslnl's Guidebook 3rd annual f i e l d trip: Thompson, A.M.editor, Petroleum Exploration Society of New York, Universityof Delaware, p. 103-109. _.. .._

Lee, C.K., 1981, S i t e i n s p e c t i o n report: U.S. E n v i r o n m e n t a lProtect ion Agency, Philadelphia, Pennsylvania.

_______, 1982, A hydrologic survey; U.S. EnvironmentalProtection Agency, P h i l a d e l p h i a , Pennsylvania.

Lee, C.K., and McGovern, J.G., 1982a, F i e l d i n v e s t i g a t i o n s ofuncontrolled hazardous waste s i t e s , a hydrologic survey ofArmy Creek L a n d f i l l and Delaware Sand and Gravel Landfill,New C n s t l e County, D e l a w a r e , FIT p r o j e c t : Task report byEcology and Environment, Inc. to the U.S. EnvironmentalProtection Agency.

______________________, 1982b, F i e l d i n v e s t i g a t i o n s ofu n c o n t r o l l e d hazardous waste s i t e s , w e l l d r i l l i n g a tDelaware Sand and Gravel L a n d f i l l , New Castle County,D e l a w a r e , FIT p r o j e c t : Task r e p o r t by Ecology andEnvironment, Inc. to the U.S. Environmental Protection Agency.

L e i s , W a l t e r , and o t h e r s , 1976, Con t r o l program for l e a o h a t ea f f e c t i n g a m u l t i p l e a q u i f e r system, Army Creek L a n d f i l l : iuP r o c e e d i n g s of the N a t i o n a l C onference on D i s p o s a l ofResidues on Lnnd, September, 1976.

M a r i n e , J.W., 1955, D e l w a r e i n W a t e r l e v e l s n n d a r t e s i a npressures in o b s e r v a t i o n w e l l s in the U n i t e d Sidles in 1952:

ic no r>'' " '•• >•< i•10 /I 'I .'] i i I . '-i r' i "

U.S. Geological Survey Water-Supply'Paper 1221, p. H-18.

Marine, I.W., and Rasmussen, W.C., 1954, Delaware, in Waterlevels and artesian pressures in the United States in 1951:U.S. Geological Survey Water-Supply Paper 1191, p. 11-16.

i___________, 1955, Preliminary report on the geology and

ground-water resources of Delaware: Delaware GeologicalSurvey Bulletin 4, 336 p.

Martin, M.M., in review, Simulated ground-water flow in thePotomac Aquifers, New Castle County, Delaware: U.S.Geological Survey Open File Report.

Martin, M.M., and Denver, J.M., 1982, Hydrologic data for thePotomac Formation in New Castle County, Delaware: U.S.Geological Survey Water-Resources I n v e s t i g a t i o n s Open-FileReport 81-916, 148 p.

M i l l e r , W.J., 1982, An analysis and computer s i m u l a t i o n ofground-water flow in the vicinity of Army Creek Landfill, NewCastle County, Delaware: Unpublished Master's Thesis,University of Delaware, Department of Civil Engineering.

M i l l e r , W.J., and Silka, L.R., 1981, Application of Computermodeling for the investigation of ground-water contamination:Fourth Annual M a d i s o n Conference of A p p l i e d Research andPractice on M u n i c i p a l and I n d u s t r i a l Waste, Sept 28-30, 1981,pp. 361-382.

New Castle County, Areawide Waste Treatment Management Program,1977, Preparatory paper for Army Creek (Llangollen) landfillroundtable, November 17-18, 1977: New Castle County Delaware.

______ _, 1979, Army Creek L a n d f i l l t e c h n i c a lroundtable, November 17- 18, 1978, summary proceedings(draft): New Castle County Delaware,

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in '''"' -' '-' S B 0

the L l a n g o l l e n L a n d f i l l , New C a s t l e County, Delaware!Consultants report by Roy F. Weston, Inc. for the Departmentof Public Works, New Castle County, Delaware.

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________ „, I973a, Groundwater contamination associated theL l a n g o l l e n l a n d f i l l , New Castle County, Delaware, extent ofcontamination and proposed cor r e c t i v e procedures: Consultantsreport by Roy F. Weston, Inc. for the Department of PublicWorks, New Castle County, Delaware.

_________, 1973b, E v a l u a t i o n of ground-water a v a i l a b i l i t yand pumping capacity of the Llangollen area: Consultantsr e p o r t by Roy F. Weston, Inc. for the Department of P u b l i cWorks, New Castle County, Delaware, 8 p.

__________, 1974, P r e l i m i n a r y f e a s i b i l i t y study, leachatecontrol sTrotegies for Llangollen l a n d f i l l , New Castle County,D e l a w a r e : C o n s u l t a n t s r e p o r t by Roy F. W e s t o n , Inc. for theDepartment of P u b l i c Works, New Cnstle County, Delaware, 55 p.

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Consultants report by Roy F. Weston, Inc. for the Deportmentof Public Works, New Castle County, Delaware.

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, 1971), General ground-water q u a l i t y in fresh-wafeTa'quTTers of Delaware: Delaware Geological Survey Reportof Investigation No. 15, 22 p.

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