APPENDIX A

HYDROLOGY ASSES KENT

<N O i o o r-m o

A-l

2 7 2 2 7 6

llllllllllllllllllllllllllll 062

APPENDIX A

A. l INTRODUCTION

Radian Corpora t ion has ass i s ted in the eva lua t ion of remedia l ac t ion

a l te rna t ives for the Lipar i hazardous was te s i t e in Pi tman, New Je rsey . EPA

Region I I i s cons ider ing encapsula t ion and capping of the was te a rea and

co l lec t ion and d i scharge of contamina ted leacha te to the Glouces te r County

Ut i l i t i es Author i ty (GCUA) water t rea tment p lan t . The New Je rsey Depar tment

of Envi ronmenta l Pro tec t ion (DEP) requi res tha t a t rea tab i l i ty s tudy be

conducted p r ior to d i scharge of l andf i l l l eacha te to a publ ic ly owned

t rea tment works (POTff ) .

Under the leacha te co l lec t ion /POTff t rea tment a l te rna t ives , the

leacha te wi l l be co l lec ted by recovery wel l s p laced in s t ra teg ic loca t ions a t

the Lipar i s i t e . The product ion ra tes of these wel l s wi l l impact bo th the

quant i ty and qua l i ty of the proposed d i scharge to the POTff . In i t i a l cos t

es t imates for the wel l f i e ld co l lec t ion sys tem were repor ted in Radian (1982)

(43) . This e f for t suppor ted a cos t compar i son s tudy for compar i son of d i f ­

fe ren t remedia l ac t ion ac t iv i t i es .

This appendix provides cos t re f inements of Radian ' s p rev ious wel l

f i e ld cons t ruc t ion es t imates and opera t ion and main tenance cos t s . Also

presen ted a re cos t s for severa l scenar ios of wel l des ign and wel l s iz ing tha t

could accompl i sh the dewater ing . These cos t s can be used to assess cos t s fo r

fu ture de ta i led des ign . I t should be no ted tha t fu ture ac t iv i t i es a t the s i t e

may provide more s i te—spec i f i c informat ion su i tab le for ad jus t ing th i s

es t imate .

A.2 PURPOSE

As input to the t rea tab i l i ty s tudy of the Lipar i l andf i l l l eacha te

th i s ana lys i s provided a de te rmina t ion of pumping per iods and f low ra tes of

the leacha te co l lec t ion wel l s . This formed the bas i s for es t imates of

A-3

l eac ia te d i scharge to t i e POTW and of t i e percentage of GC3TA in f luent re ­

presen ted by t i e l eac ia te . l i e second purpose of t i i s task was to re f ine t i e

in i t i a l cos t es t imate fo r t i e dr i l l ing , cons t ruc t ion , and comple t ion of t en

wel l s in t i e Coiansey sands a t t i e Lipar i s i t e , wi ic i was p repared in an

ear l ie r Radian s tudy . T ie o r ig ina l wel l des ign bas i s was modi f ied to re f lec t

addi t iona l iydrogeologica l eva lua t ion and in te rpre ta t ion as to t i e probable

dewater ing requi rements . T ie fo l lowing were ob jec t ives of t i i s iydro logica l

eva lua t ion :

• Determine Coiansey Sand f i e ld pumping deve lopment

per formances f rom prev ious inves t iga t ions ;

• Provide to t i e t rea tab i l i ty s tudy t i e pro jec ted ra tes

of d i sc ia rge of p roduced groundwater .

9 Ref ine prev ious dewater ing t ime es t imates and pro jec ted

iead d i f fe rences across t i e s lur ry wal l ;

• Develop a conceptua l dewater ing p lan to a id in re f in ing

s ior t te rm and long te rm opera t ion and main tenance cos t

es t imates (par t icu la r ly t i e need for cont inued pumping

over t i e long te rm to main ta in a dewatered condi t ion

wi t i in t i e s lur ry wal l ) .

T i i s eva lua t ion was no t in tended to provide a f ina l des ign for t i e

wel l co l lec t ion sys tem.but ra t ie r to provide a re f inement of t i e prev ious work

so as to provide a be t te r approximat ion of conceptua l des ign cos t s .

A. 3 DEWATERING ESTD1ATS

Tie Coiansey Sand i s t i e main aqui fe r a t t i e s i t e wi ic i i s to be

enc losed by t i e s lur ry wal l . I t i s under la in by t i e Kirkwood c lay . For t i i s

s tudy t i e s i t e was assumed to be essen t ia l ly a "ba t i tub" due to t i e l a te ra l

A-4

coaf ia iag e f fec t f rom t i e s lur ry wal l aad t i e ver t ica l coaf iaemeat p rovided by

t i e uader ly iag EJ i rkwood Format ioa c lay . For a 3 - foo t th ick s lur ry wal l , a

permeabi l i ty va lue of 2 .84 z 10— * gpd/ f t1 (1 z 10—7 cm/sec) was assumed.

Permeabi l i ty of t i e Kirkwood c lay was assumed to be 2 .1 z 10- ' gpd/ f t1 . Ia

addi t ioa to permeabi l i ty , average va lues of s t a t ic water l eve ls were used for

t i e Coiaasey Saad , Ki rkwood Format ioa . aad Kirkwood c lay t i i ckaess . From

t i ese average da ta va lues , t i e" ra tes of l eakage aad t imes for dewater iag t i e

Coieasey Saads were ca lcu la ted . Tie summar ized resu l t s oa Table A—1 were t i ea

used to des iga a dewater iag program aad to prepare a cos t aaa lys i s

(Sec t ioa 4 .0) .

T ie f i r s t s tep to deve lop Table A—1 was to es t imate t i e to ta l volume

of g rouadwater i a t i e Coiaasey Saad t i a t would be eac losed by t i e s lur ry wal l

aad c lay f loor . T i i s was de te rmiaed by as iag t i e bas ic iydro-geologica l da ta

fo r t i e Coiaasey Saads (52) to deve lop t i e parameters aeeded to compute t i e

grouadwater sa tura ted volume. A p laa imeter was used to compute t i e a reas

wi t i i a t i e s lur ry wal l fo r t i e sa tura ted t i i ckaess of bo t i the upper aad lower

Coiaasey saads . T i i s was t i ea mul t ip l ied by t i e t i i ckaess aad by t i e spec i f ic

y ie ld to g ive a to ta l volume es t imate of grouad—water a t t i e s i t e . The to ta l

volume es t imated for t i e 16 acre s i t e was 3 ,554 ,000 cubic fee t of g rouadwater

i a the sa tura ted por t ioa of the Coiaasey Saads . Therefore , i f a des iga pump—

iag ra te for a dewater iag sys tem i s 100 ga l loas per miaute (gpm) (43) , i t

would t ake about 0 .5 years , us iag a vo lumet r ic aaa lys i s (wi thout i a f low

through t i e s lur ry wal l o r uader ly iag c lay) to dewater the aqui fe r to t i e top

of t i e Kirkwood c lay , assumiag per fec t d ra iaage .

T ie aez t s tep was to eva lua te t i e po tea t ia l fo r leakage across a

3—foot wide s lu r ry wal l uader idea l coadi t ioas ( i . e . , homogeaeous , i so t rop ic

aad ua i formly th ick aqui fe r ) . I a order to compute coaserva t ive leakage

va lues , i t was assumed tha t a mazimum head d i f fe rea t ia l of 24 fee t across t i e

s lur ry wal l would be maia ta iaed . T i i s d i f fe rea t ia l was d iv ided ia to 6 ver t i ­

ca l hydros ta t ic pressure zoaes . T i i s 24- foot va lue i s a l so the average

sa tura ted t i i ckaess of t i e Coiaasey Saad . T ie 1eagt i of t i e s lur ry wal l i s

pro jec ted to be about 3 ,120 fee t a rouad t i e s i t e . Tie Darcy grouadwater f low

TAUI.Ii A-1. SUMMARY OK SLURRY WALL AND KIRKWOOD CI.AY IMPACT I ON LII'AR 1 DliWATKRI NC LSTIMATKS

> I Oy

C i l c u l i l i o a U . r i i

1 . T c h a t 1 0 0 g p a i * • i l k t a l l o w

2 . H e w a t a r l u g a t 1 0 0 g p m l o r T c h u 2 0 g p m l o r T c b l * i t i l l t a l l o w

3 . S t a r r y w a l l a n i m a t e d l e a k a g e , a u o u t I l o w

4 . l e a k a g e i t r o i i K i r k w o o d c l a y , a o o u t f l o w

J . l a . l a g . ( . l u r r y w a l l a n d T k w ) I t l I t a g 1 1 1 a b a c k t o o r t g i a a l U k a l e t t e w a l a c l e v e l

4 . l e a k a g e ( r l a r r y w a l l a n d I k - ) t i l l i n g t o o r t g i a a l I I . s t a t i c w a t e r l e v e l a t ~ 4 f t a b o v e 1 1 a c l a y

7 . D e n a t u r i n g l e b l f r o a i T k w o r t g i a a l s t a t i c w a t e r l e v e l a t - I f e e t a b o v e T k w c l a y a t 1 0 0 g p m w i t h i n f l o w

M . D e n a t u r i n g T e b l f r o * T k w o r i g i n a l i t a l i c w a t e r l e v e l a t ~ 4 f e e l a b o v e T k w e l a y a t 2 0 | | i a w i l b I n f l o w

l . a a k a g e l a f l o w O r i v t n g llcad

_ S 0 U f i i l T k w * T c b 1

P c i a c a b i I 1 t y < g p d / f I * )

3 " S l u r r y V a l I

T l a i e t o O w a a l e r C o b a u a e y S a u d .

I k w e * ( Y e a r s )

Y e a r , t o K e f 1 1 1 t o T c b T k w O r i g i n a l O r i g i n a l

S t a t i o l a t e r S t a b l e V a t a r l e v e l L a v a l

2 . S 4 a 1 0 ( 1 a 1 0 * t a / i a u )

2 1. U . 4 . 1 0 " c w / i a c )

T e h e a t t e a t e d t o t a l g r o u n d w a t e r v o l u m e - 3 . J J 4 . 0 0 0 f t * .

w a t e r v o l u a e - I . 9 S 9 . 0 0 0 f t * . T t b l - I . S O S . 0 0 0 f t *

i i J g p d * I n f l o w

1 . 9 4 7 g p d I n f l o w

2 . J S 2 g p d I n f l o w

2 . J S 2 g p d i n f l o w ! aitlaal.d water voluaa - 4 7 3 . 9 3 3 f t *

N e t d i s c b a r g e - 9 B . 2

IP"

N e t I P "

* ! c b - C u b a n . a y S a n d * ' l c b w ~ u p p e r C u b a n a a y a a n d * * l c b I ~ l o w e r C o b a u a e y t e n d « T k w ~ K i r k w o o d P u m a l i o n • l k « e ~ K i r k w o o d F o r m a t i o n c l a y * g p m g a l l o n , p e r m i n u t e 1 g p d ~ g a l l o n , p e t d a y

O a> o>

equation was used to compute flow througi tie slurry wall. According to tiis equation, tie volume of flow is equal to tie product of tie permeability, hydraulic gradient and area (Q " KiA). Groundwater leakage through tie slurry wall was calculated to be 635 gpd.

Tie second potential zone of leakage at tie site is upward through tie Kirkwood Formation. At present tie hydraulic gradient is downward from

tie Cohansey Sand through tie Eixkvood clay into tie Kirkwood sand (52) low-ewer, after tie initial dewatering of tie Cohansey Sands tiis gradient will

reverse such that tie hydrostatic head in tie Kirkwood Formation will be an average of four feet above tie top of tie clay and into tie Cohansey Sand.

Again using tie Darey equation, a computed average upward leakage for tie 16-acre site would be 1,947 gpd (Table A-l). This is based on an average clay

thickness of 12 feet, a permeability of 2.1 z 10-' gpd/ft* (52), and an area

of 15 acres.

Once tie relative bottom and side leakages were estimated, their

impact on short and long-term pumping requirements was examined. Net pumping rates were estimated by computing tie difference between tie site dewatering flow and tie leakage inflow. It was assumed that a clay cap would be com­pletely impervious and, therefore, would allow negligible recharge to tie

Cohansey Sands from tie surface. If an optimum discharge could be maintained of 100 gpm, then dewatering would still be in tie order of about 0.5 years

with leakage inflows. On tie other hand, a more conservative volumetric approach due to tie possible difference in yield between tie upper and lower

Cohansey Sand would be that dewatering of tie upper sand would be at 100 gpm, followed by dewatering of the lower sands at 20 gpm. This would result in about 1.5 years to dewater tie Cohansey Sands, and would be tie more conser­vative estimate for conceptualizing a dewatering program.

A volumetric analysis was then conducted to determine tie time re­

quired for tie water level in tie Cohansey Sand to recover after a conceptual

dewatering period. Again it was assumed for tiis calculation tiat no leakage

would occur through tie surface capping system. Two possibilities were ex­

amined. First, tie time for leakage to fill tie area back to tie original average static water level in tie CoianSey Sand (i.e., 24 feet above tie top

of tie Eirkwood clay) was estimated. In tiis case if tie groundwater were to reeover witiin tie enclosed area to an original static water level, a downward

leakage into tie underlying Eirkwood Formation would be induced, possibly

resulting in contamination. Iierefore a second ease was examined. Under tiis

case, it was assnmed tiat tie groundwater recovers to tie prevailing hydro­static head of tie Eirkwood Formation, wiici is about 4 feet above tie top of tie clay. These two cases provide a range of values from wiici estimates of

dewatering requirements can be made.

Analyzing tie above witidrawal and leakage data summarized on Table A-l and using strictly a volumetric analysis approaci, tie initial dewatering

time under ideal conditions range from 0.5 to 1.5 years at a projected flow rate of 100 gpm to 20 gpm. If inward leakage! continued after tiis time it

would take approximately 4 years for tie static water level to recover to tie

hydrostatic iead level for tie Eirkwood Formation and it would take about 28

years to fully recover to tie original static water level, in tie Coiansey Sand. Several scenarios for pushing and monitoring programs were developed

using tiese higi and low values as tie bounds for continued dewatering cycles. Tie objective of tiese scenarios would be to maintain static water levels suci

tiat groundwater flows inward tirougi tie slurry wall tiereby preventing out­flow of contaminated groundwater. Tie results of tiis analysis were used in designing a conceptual well field (Section A, 4) and refining well field

(Section A.5) cost estimates.

A-8

A. 4 KiIHS55i»J ;AL WELL FIELD DESIGN

In earlier cost estimates (43), the well field design was based upon

tie assumption that pumping of 10 wells was continuous for very long periods of time. It was suggested that lower pumping rates may be required to sustain

a constant flow, due to well interference and the low productivity of the

lower Cohansey sands. Variable pumping rates pose problems in design of a well field. The pumps required under these conditions must perform over a wide range of dynamic pumping conditions. While pumps are available that can pump at these ranges of pumping rates there is the potential for significant stress on the pumps and motors'. Some methods that can be used to control the pumping rate include purchasing specially designed pumps, modifying off-the-

shelf pumps throttling the discharge, installing water level switches in the well, and using a variable speed drive system. In this analysis for refining well field costs, emphasis was placed on the use of off-the-shelf technology

to keep costs down and to ensure a reasonable supply of future materials.

Although pump diameter influences the well size, the well size is

also controlled by the expected formation productivity. The upper Cohansey

sand is quite permeable relative to the lower Cohansey sand. Once the upper Cohansey sand is dewatered, water yield from the lower Cohansey sand will

control the production of ground water and, as a result will dictate the configuration number, type and size of wells for dewatering. For instance a large diameter well can act as a collection sump, minimizing well losses,

which will be important for the final period of dewatering to the Lipari site. However, less expensive, smaller diameter wells may be suitable if the pumping

rates can be tailored to minimize well and formation losses.

The dewatering analysis in Section A.3 (Table A— 1) predicted that

the probable time required to dewater the slurry wall enclosed site would be approximately 0.5 year at 100 gpm for ten wells or about 1.5 years discharge rate ranging from 10 to 20 gpm. In practice, several years may be required because as the formation is dewatered, the drawdown interference between the

pumping wells will increase such that the pumping rates of the individual

veils vill iawe to be reduced or cycled ia order to collect *s much of tie

contaminated ground water as possible. Hie dewateriag times from Table A-l do aot reflect tie effects of well iaterfereaces. lie projected pumping periods

for tie site under 'ideal coaditioas are expected to be siort. separated by

loag periods of iaactivity.

Two types of wells were considered ia tiis evaluation a 4-iach well completed asiag a iollow stem auger and a 10-iaci well completed using a cable tool. Tie 4-iaci well would be equipped pimps with replacable plastic

iatpellers can. Ia tie seeoad case, tie 10-iaci well would have all staialess

steel pumps tiat would be expected to last tie life of tie pumpiag period aad

wiici could be decomaissioaed for storage after the pimping cycle, or used at other sites. Ia boti cases tie "off-the-shelf" pumps would be expected to

operate over a wide range of diseiarge rates. Therefore a variable speed drive system was iacluded to eoatrol tie diseiarge. Tiis portable, automatic

system tailors tie diseiarge to tie pumpiag requiremeats, wiici saves wear aad

tear oa tie pumps aid reduces tie requiremeats for oarsite field moaitoriag of

tie well field.

For tie conceptual wellfield design, tea dewateriag wells were

assumed; four ia tie waste area would be coastzueted of all staialess steel

aad six outside tie waste area would be a combination of FVC aad staialess steel. Ia tie latter case, tie staialess steel screen materials would be

positioned opposite tie saturated zone, while materials ia tie unsaturated zoae would be PVC. For tie purpose of tiis study two drilling methods were

used ia estimating well construction costs — installation of tea 4>—inch wells usiag a iollow stem auger aad iastallation of tea 10-iaci wells using a cable tool. Pumpiag equipmeat is to be "off-tie-sielf" aad diseiarge controlled by a variable speed drive system. Two pumpiag cycles after iaitial dewateriag

years aad 28 years) were used for estimatiag operation aad aaiateaaace costs.

A-10

070

A. 5 OTTT.T. ETFT.n COST REFINEMENT

Based upon the conditions noted in Sections A«3 and A.4, Radian's

previous cost estimate (43) has been refined for constructing a 10-well field

to withdraw ground water from the Lipari site. This cost refine-nent provides

a comparison of two different well sizes (4- and 10-inch) and technologies

(anger and cable tool). The conceptual well designs were based on the follow­

ing parameters:

• 4- or 10—inch wells • 42 foot average depth • 24 feet average screen length 9 21 feet of casing material (PVC and stainless steel

designs)

Refined cost estimates are presented in Table A-2. Estimated O&U costs for dewatering on a 4- or 28-year cycle after initial dewatering are

shown in Tables A-3 and A-4 respectively. Both tables assume an initial 1.5

year dewatering period.

A contingency estimate of 20% is to provide coverage for the in­

creased safety precautions that will be necessary for work undertaken at the Lipari site. The cost estimates presented do not contain any provisions for general and administrative costs that would be incurred by a prime contractor

in managing the various subcontractors who will be involved with construction of the well field. If EPA does not function as the prime contractor, that

cost (approximately 25% - 40%) should be added to the estimate. Also, these estimates do not include inflation, capital recovery costs, insurance or

interest charges, and provide no credit for salvage value.

A-ll

TAHT.g A-2. REFINED COST ESTIMATE FOR LIPARI COLLECTION SYSTEM FOR TWO DRILLING TECHNOLOGIES

Construction Cost

12" Bollow Stea 4" Vsll lager Construction

10* Cable Tool 10" toll

Constraction

foil drilling (10 foils) foil nstsrisls. tad iastsllstiou to sa swerage diftk of 42 ft. foil dswelopaaat sad safety equipment.

ganlnaent

10-3-3/4* 1/2 Bp stainless steel snbaorsibls poap.s for 10-inch well; 1-1 J/is* 1/2 BP snbasrsibla poap for 4—ineb vsll.

10 - Stsialsss stssl pnap shroud material st ISO each

10 - Switches sad wiring for pops st ll.OO sscb

10 - flew wnlwes sad parts st ISO sash

1-1/4* Staialsss stssl drop pips HPT for 10 wolls. leap >«»

Collection pipe to property bonndsry with installation - 1S00 ft st 112.10/ft

Variable speed driwe system lop saa (reusable systea)

TOTAL

133,000

1700 ea/17.000

1300

12.000

1500

12.000

123.000

127.000

1170.000

2540 ea/15.400

1300

. 12.000

2500

12.000

123.000

127,000

2U5.000 1230,400

TOTAL SBOCNDf AXSt C0LLECZ20N STSTEH

Constmotion of a 10 well field

Eaginseriag serwiaes st 15%

Contingencies st 20%

TOTAL CCMSTSOCrXON COSTS

1115.000

17.250

23.000

1155.250

1230.400

34,560

4*08"

1311.040

A-12

TABLE A-3. CONCEPTUAL 04M COST ESTIMATES 4-YEAR CYCLE

Caae I. 4-Tear Davetar lag Cpcle: Sroaad «atar reeersrt to original Eirfcrood Foraation grand ester lrral.

Parted! -1-1/2 Taari

1. Vail field inspection/monitoring eater leeels. sampling it/it at 1.392 bears

2. Repair asd raplaea 2 pnap failares. pssp asd laber

3. Coatsainaat monitoring 30 peoples at 3l.175

4. Centaltant. nanatenant and raparting

9. Pomp lag easts — oleetrieitp 32.338 bh at i0.05/br Total Odd Cost First Tsar

i 11.13d

3.000

33.250

13.000

3 32.013

P4ra* T.ar kfttr Inlrl.t Oearatarina 1. Veil fiald inspection. monitoring ester leeels.

raa pnpi t8/hr at 213 bra

2. Caasoltiag aaaageaaat aad reporting 3 2.288

3 1.228

2 •<"">

«"•«' 2.» Aft.e Initial Doeateriaa

1. Vail field iaepeetiea. aeaiteriag aatar leeels. roa paaps 38/br at 34 brs

2. Caasoltiag aaaageaaat aad ^reporting 3 1.571

3 512

2 -030

n»«l •»< F""> Tears After Initial Deeateriat

1. Vail fiald iaspaetiea. aeaiteriag aster laaals, raa poops 38/br at 34 brs

2. Caasoltiag aaaageaaat aad rapertiag 3 2.332

3 312

-Liza

Ta.r set'a lalt"' Peestarlot

1. Veil field start op. aoaiteriag. sampling 38/br at 830 brs

2. Cessaltiag. aaaageaaat tad rapertiag 313.200

3 3.340

« » «

i.— Other Font Tear g—

1. Repair tad replaee 1 poap failore

2. Ceetaaiaaat aeaiteriag 41.173/sample at 20 eaaplee „

3. Poapiag "seat, well field start op at sad of 4 peer epele - 313 Eeb at to.OS/it

t 1.500

17.330

31

319.131

Total far 4-pear deeateriag epele -310S.000

A-13

073

J

TABLE A-4. CONCEPTUAL O&M COST ESTIMATES 28- YEAR CYCLE

Gate II. 28-Tttr Derm tiring Cyolt: Groaad water rtoortr* ta original CoAtatty Saad grooad weter level.

Tnititl Period: -1-1/1 Tears

1. fall field laapeotioa/aonitoriag water levels, saopliag ]Whx at 1.392 knit

2. Repair tad rtvitea 2 pan? fail area. psap tad labor

3. Coataaiaaat to altering 30 staplea tt 51.175

4. Caataittat. aaaageaeat tad reporting

3. Pnaping easts - el tonicity 52.338 IwA tt 50.03/Ar Total Odd Cost Fine fttr

5 II .238

3.000

35.230

15.000

__Itill 5 57.013

T.» Pewstartar

1.. Wall field inspection. aonltoriag titer levels, raa paayt 58/Ar tt 218 Art

2. Caataltiag ataageaaat tad reporting 5 2.788

5 1.728

Tttr Twirls! Pawiterlat

1. fall field iatptotioa. isoni coring tattr levels. rna pnapt 58/Ar tt 84 Art

2. Caataltiag aaaageaeat tad reporting

V..w. 3 TAro-.H 78 After Tnifit-1 Pawtttriag

1. fall field iatptotioa. aoaitoriag water latelt. raa pnapt 58/Ar tt 800 Art

2. Caataltiag aaatgeaaat tad reporting

earl. T.tt Aft.- Twieitl Dettterint

Stat tt initial datateriag period: 1-1/2 years

5 1.572

532.900

5 512

1-M0

5 8.400

28 .300

587.013

Other 28 Tt»r Ore l . Eiwewies

1. Repair tad replant 2 pnap ftUarta

2. Caattainaat aoaitoriag tt yetrt 5. 10. 20. 28 51.175/staple tt 40 staples

3. Caataltiag aaaageaeat tad reporting tt years 5. 10, 20, 28

5 3.000

47.000

13.120

584,014

Total for 28-year deirttaring cycle -5288.000

A-14

074

A hydrogeologie assessmeat was conducted ia order to detemiae de^-

wateriag requiremeats aad to refiae well field cost estimates for remedial

aetioa at the Lipari hazardous waste site. ( x

Utilizing a volumetric analysis for detezaiaiag conceptual dewater-

iag aad recovery times, it is conservatively estimated that, under ideal conditions. it would tahe approximately 0.5 to 1.5 years to lower the gronad water level ia the 16 acre site dowa to the Kirkwood clay. It is calculated

that about 28 years would be required for the water level to recover to the

Cohaasey saads. However, discharge of contaminated grouad water from the site is likely if the water level is allowed to recover to this level. If the water level is allowed to recovery oaly to tke original average static water

level for the Sirtarood Formation. the refill time would be about 4 years. These time periods were used as a raage for developiag a maintenance dewater-

iag program aad for estimatiag costs.

Based oa the dewateriag times aad refiaed hydrogeological data, the

desiga aad costs for a 10-well field were refiaed. Aa additional considera-tioa ia this desiga was the effect of the lower productivity ia the lower

Cohaasey saads oa the pumpiag rate aad therefore oa well sizing. Estimates

were developed for both 4-iach aad 10-iach wells aad for drilliag using hollow stem auger aad cable tool for cost comparisoas. Coaeeptual costs for well

field constructioa were estimated to raage from about tl55,000 to 1311,000.

Costs for pempiag to maiataia lower water levels withia the slurry

wall were estimated usiag 4-year aad 28-year pumpiag cycles. The cost for the 4-year maiateaaace pumpiag was estimated to be about 1105.000; for the 28-

year program, the cost was estimated to be 1286,000.

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075