7 t t

Site y UNITID ITATII INVIRONMINTAL PROTICTION AGINC B t~ 1 rlea- c vtve

REGION I Other J F KENNEDY FEDERAL BUILDING BOSTON MASSACHUSETTS 02203====J

October 6 1986

Robert Hartley Hazardous waste Enginering Research Laboratory us Environmental Protection Agency 26 West St Clair Cincinnati Ohio 45268

Dear Bob

Attached is Olins proposal for the six-inch clay layer for the cap at the western Sand and Gravel site I have also attached my correspondence with Olin regarding the cap design

I will be meeting with Olin later this month so I would appreciate any comments you have on this

If you have any questions on this please feel free to call me at PTS 835-3641

Sincz

John~~ cca Richard Boynton RI VT Superfund Chief

Felix Harvey RIDEM

- wo Attachments

I I I middotI

I I I middotI

the more middotspecific termbullhydraulic conductmiddotivityt middot An acceptable

method for soil hydraulic conductivity has been includedmiddotmiddot-ln

the oppendix to thismiddot document middot middot middot middotmiddot middot middot ~

In situ soils can be considered acceptable as aoilbull ltiner

materJmiddotpliovidedmiddot themiddot apeciflcationsmiddot in thisgui~nce Jre met middot

Natural soil liners should be free of conduits ndochan)lelsmiddot middot

whicbVould middotconveyliquida middotthr~ugh the li~er middot lhia middot inc1ude~

root holes sand lenses cracks fractures etc~middot middot- middot middott middotmiddotmiddot ~

E Cap (Final middotcover) Design middotmiddot

1 The Regulation

The cap or final cover middotmust be designed t~ -minimize infil shy

tration of precipitation into the landfill after closure~middot t It

must be no more permeable tha~ the liner syst~middot It ~ust

) operate with minimum maintenance and promote draina~e from middot ita middot

surface while - minimizi~ erosion middot It must also be designed so

that settli~ and subsidence are accommodated to 1-niAize the

potential for disruption of continuity and function of the final

cover

middot 2 Guidance

(a) The cap or final cover should be middotpl c ~ over each

cell ~s 1 is completed In case here landfil~a arbull operated

with multiple lift~ (cella place($ vertically on ~op ot each

other) final cover cannot of co ae middotbe pl c untU th fin 1

lift ia ~ cat~~pleted altho h ln eri cov r houl4 b deS d to middot

each cell bullbull lt is bullcompl t d

Where po aible wh n larve c ed hou d

be pl ced filling pr r 1bull 1 0 po b 1

2

1 nolz pr

I I I middotI

the more middotspecific termbullhydraulic conductmiddotivityt middot An acceptable

method for soil hydraulic conductivity has been includedmiddotmiddot-ln

the oppendix to thismiddot document middot middot middot middotmiddot middot middot ~

In situ soils can be considered acceptable as aoilbull ltiner

materJmiddotpliovidedmiddot themiddot apeciflcationsmiddot in thisgui~nce Jre met middot

Natural soil liners should be free of conduits ndochan)lelsmiddot middot

whicbVould middotconveyliquida middotthr~ugh the li~er middot lhia middot inc1ude~

root holes sand lenses cracks fractures etc~middot middot- middot middott middotmiddotmiddot ~

E Cap (Final middotcover) Design middotmiddot

1 The Regulation

The cap or final cover middotmust be designed t~ -minimize infil shy

tration of precipitation into the landfill after closure~middot t It

must be no more permeable tha~ the liner syst~middot It ~ust

) operate with minimum maintenance and promote draina~e from middot ita middot

surface while - minimizi~ erosion middot It must also be designed so

that settli~ and subsidence are accommodated to 1-niAize the

potential for disruption of continuity and function of the final

cover

middot 2 Guidance

(a) The cap or final cover should be middotpl c ~ over each

cell ~s 1 is completed In case here landfil~a arbull operated

with multiple lift~ (cella place($ vertically on ~op ot each

other) final cover cannot of co ae middotbe pl c untU th fin 1

lift ia ~ cat~~pleted altho h ln eri cov r houl4 b deS d to middot

each cell bullbull lt is bullcompl t d

Where po aible wh n larve c ed hou d

be pl ced filling pr r 1bull 1 0 po b 1

2

1 nolz pr

I I II

trench operations where filling prcgresses fro~ one end of

the trench to the other

(b) Tbe cap (final cover) should consist of the following

as a ainiauaa

(1) A vegetated top cover as described in parauraph middotmiddot(c)

of this section -middot (2) A middle drainage layer as described in par~graph

(d) of this sectionr and

(3) A low permeability bottom layer as described in

paragraph (e) of this section

(c) The vegetated top cover shouldamp

(1) Be at least 60 centimeters (24 inches) t~ickr

(2) Support vegetation that will effectively minimize

erosion without need for continuing application of fertilizers

irrigation or other man-applied materials to ensure viability

and persistence (Pertilizers water and other materials may

be applied during the closure or post-closure period if necessary

middot to establish vegetation or to repair damiQ e )J

(3) Be planted with persistent species that will effectshy

ively aintbullize erosion and that do not have a root system

that will penetrate beyond the vegetative and drainage layerr

(4) Bampve a final top slope after allowanc for settling

and subsidence of between t hree and five percent unless the

owner or operator knows that an alternate slope will effectively

proaote drainage and not subject the closed facility to erosion

ror slopes exc eCSing f 1ve percent th axim eroaion rate

I I I -I

should not exceed 20 tonsacre usi~ the USDAPniversal Soil

Loss Equation (USLE)J and

(5) Have a surface drainage system capable of conducti~

middot run-off across the cap without fo~in erosion rills and gullies bull

(d) The drainage layer shoulda

(1) Be at least 30 centimeters (12 inchea)middotthick with a sat shy

urated hydraulic conductivity not les8 than 1 X lo-3 ~

cmtaecr

(2) Bave a final bottom slope of at least two percent

after allowance for settling and subsidence

(3) To prevent clogy ing be overlain by a graded ~ranular

or synthetic fabric filter that meets the specifications of

section c 2 b of this guidance and

(4) Be designed so that diacharoe flows freely in the

lateral direction to minimize head on bullnd flow through the low

permeability layer

(e) The low permeability layer should have two componentsamp

(1) The upper component should

(A) Consist of

(B) Be protected from dam~~ge below and above the membrane

by at least 15 centimeterbull (6 inchel) of bedding bullaterial no

coar1er than Unified Soil Clalsification Syat (uses) 1and (SP)

And vhich il free of rock fractured atone debril ~obblea

rubbish roots and Iudden changes in grade (alope) Ibe drainshy

age layer and lower soil (clay) coaaponent Jaay aerv aa bedding

ateriala when in direct cont ct ith ynthtic eapa if they

eet the ap cificationl contain d h r in1

25

I I I I

(C) Have a final uppe~ alope (in contact with the bedding

material) of at least two percent after allowance for settling r

anCI

(D) Be loca~e~ wholly below the aver~bull ~epth of frost

penetration in the area

(2) Tbe lower component ahoulda

(A) Inclu~e at leaat 60 centilleters (24 inches) of soil

recompacte~ to the maximum practical extent but capable if

plbullcbullCI on a flra baae of being recompacte~ to a aaturated

hydraulic conductivity of not more than 1 X lo-7 ~aecr

(B) Have the aoil emplace~ in lifts not exceeCiing 15

cent~eters (6 inchea) before copactlon to maximize the

effectiveneas of compaction

middot (f) In deaig ning the final cover owners an~ operatorbull

shoulCI estimate and accCIIIIIodate the amount of aettling and middot

subsidence expected as a reault ofa bull

(1) The incorporation of containerized liqulds prior to

the ban ~posed March 22 1982 (47 PR l2316)r and

(2) Degra~ation and long-tara conaolidation of waste

3 Discussion

The guidance calla for placing the final cover at closure

of each cell or preferably aa filling of the cell progreases

In soae casea auch aa when operatlo a are con4ucteCI in ultiple

11 ta final co r c nnot be applied until the top cell is filled

teaa aubatanti 1 tnt rt cov r should be pplied to other cella

n ltipla lU andfUl bull

26

I I I I

The Agency believes that a three layer final cover (cap)

will adequately mi~imize infiltration of precipitation which is

the primary purpose of the fina~ cover The final cover a~ts to

minimize infiltration by causing precipitation to run off thro~ h bull bull bull bull bull bull bull 0 bull bull middot bull bull bull bull bull bull bull bullbull

uae of slopes drainage layers and impermeable and slightly bull bullbull bull bull bull bull bull bull bull bull bull bullbull 0 bull bull bull

pe~eampble barriers by minimizing infiltration the generation -middot of leachate will also be minimized thereby reducing long-term

bull bull bull bull bull bull bull bull bull bull bull r bull bull bull bull

discharge of Pllutants to the groun~ water to a bare mintmum To prevent the bullbathtub effect bull ie to prevent the landfill

frCXI f~lling with leachate after closure when the leachate collection aystem ceases to function the final cover must be no

middot more peraeable than the most impermeable component of the liner

ayatez (or of the underlyi~ soils) In this way no more preshy

cipitation h allowed to infiltrate the cell than can escape

thro~h the bottom liner Prevention of the bullbathtub effectbull

ia important to eliminate the possibility o~ surface overflow ormiddot

~ration thro~h porous surface strata The latter phenomenon

ia largely the cause of the problems at Love Canal in N w York

Other functions of the final cover include prev ntion of con~amination

of aurtace run-off prevention of wind dispersal of hazardous

waates and prev ntion of direct contact with hazardoua waatea

by ople nd animala atraylng onto the aite

e top layer should have t least two feet of soU capable

of us ain ng plant speci a which will Uecti ly in ice

o on o f t waa cho1en bee uae it will acc odate

ocSy cov r plant1ngl and 1 typic 1

ra c h n h wa te n nt ndustry today

e EOO

-not have root aystema which can be expected to penetrbulltl beyond

If they penetrate deeper~ middot

they can damage the i~tegrity of the low pe~eability layer

the final elope

should be at least three percent to prevent pooling due to irreyushy

laritiea of the surface and vegetation but leas than five pershy

The Agency recognizee that

operated with multiple vertical lifts or

perce~t may

ownera and operatorbull using different final

alopea ahould determine that an alternate elope will not be

beset with eroaion problema and that it will promote efficient

~riculture Universal Soil

tool for uae in evalshy

The USLS predictbull average annual soil The equation iaa

in tonaacr

ctor tonal ere

middotmiddot bull

I I II

bull

Species planted shou~d not require continuing man-made appli shy

ationa of water or fertilizers to sustain growth since middotsuch 0 bull bull

applications cannot be guaranteed in the long term Application

of water and fertilizer ia of courae acceptable during the middotearly stages of the post-closure care period aa the plant growth

ia being established middot The plant species chosen should also

-middot

the vegetated and drainage layers

After allowance for settling and aubsidence

cent to prevent excessive erosion

perated aa piles limiting final slope to five

not be practical bull

drainage The U~ Department of

Loaa Equation (USLE) ia recommended as a

uating eroaion potential

loaa aa the product of aix quantifiable factora

A bull RXLSCP

where A bull average annual ao11 loaa R bull rainfall and run-off eroaivity It bull soil erodibility f L bull alope-le~ tb fac or 8 bull slop -ateepne ctor C bull cover n f c or P bull practice f

28

I I II

The data necessary as input to this equatioo is described

in Evaluating Cover Systems for Solid and Hazardous Waste middot I

(Sw-867) September 1980 us EPA The maxilum rate o~ ~roaio~

for any part of the cover should not exceed 2 0 middottonsa~re in

or4er to minimize the potential for gully development and fl~ure

maintenance The agricultural data base indicats that rates as middot

low as 13 tonacre are achievable for a sllt-lo~ so~l sloped

4 percent with a blue grass v~etative cover lhe ~ency

believes that 2 tonsacre can be more readily achieved and

does not significantly increase cover maintenance The top

layer should also have some means of conducting run-off (eg

swales or conduits) to safely pass run-off velocities and

volume without eroding the cover

The second layer or drain~e lay r ia analogous in function

to the leachate collection system over the liner It should be

at least 12 inches thick to provide capacity to handle water

from major sustained storm events and should be co~structad of

porous materials (at least 1 X lo-3 ~sec hydraulic conducshy

tivity) Drainage tiles or other collection devices are not

necessary The Agency believes that the ccbina~ton of very

porous aedia a final mini un two p rcent slope after settling

and the lapemeabla nature of the layer bane th ill affactiv ly

conduct precipitation infiltrating the v~etatlve layer off of

the landfill As with the leachate coll c ton the

drainega layer should be ov tlain with a gr du Ot nul r

or synth tic fabric fUt r to pr v nt pl g l o th poro

dia with fin earth p rticlea c r~l d do r th

I I

~ I I

lay~r To prevent fluid ~roc backin9 up into the drainage

layer the diacharge at the ai~e should flow freely

The function of the low permeability layer ia to reject

fluid tranamiaaion thereby cauaing infiltrating precipitation

to ~xit through the drainage layer It ahould conaiat of

at leaat two componentbull lhe upper component ahould be et bull

leaat a 20 mil thick aynthetic membrane While the regulationbull

do not apecity that the final cover Pr~v~~ infiltration the

requirtaent that it be no more permeable than the bottom

liner aa a practical matter neceaaitatee the uee of bull aynthetic

mebrane lhia ia ao b caua the regulatory requirement for

the liner ayatem ~oea apecify that leachate be contained and

thia will ~ tranelated in ~oat cabullbullbullmiddot into a very nearly

iaper1Deable eyntletic merbrane liner

The minimum thickneal rec~bull~de~ ~or the eynthetic component

of the cap (20 mil) ia 1bullbullbull than that apecified for the liner

(30 wdl) becaua (l) the cap ia not expect d to come in contact

with Ch-ical leachatebull Which might haaten failur an~ (2)

once pl ced th potential for ~amage ia am ll ae compared to

ete ia placed onthe potential for underliner dam ge Where

the lin~r t~oughout th op rating life of the cell While

int ct (30 + ye ra in the abeencP o ~ ge) th aynthetic aantl lly prevent t~ af r of pracipit tionccponent wil

ry n r y urooduction ouldhr0l9h it a 4 frbullYDth tic ea a ehould

at eix inchbullbull o ~ t ri 11

y n4 or tin r bull ln

30

bull bull

I I

~ I -I

bull

drainage layer media above the synthetic cap together with

the soil (clay) liner under it can effectively function as

the bedding materialmiddot

middot Even with protection from damage the synthetic cap willmiddotmiddot

not last forever At some point perhaps in the far distant

future the synthetic membrane will degrade A~ that time middot middot middot

the function of Jilnimizing infiltration will fall to the

second component ~ 2-foot minimum clay soil cap with a maximum r

middothydraulic conductivity of 1 X middotlo-7 emsec Altho~h some

all middotamount of precipitation will seep throuuh this secondary

cap the amount of leachate generated will be quite small ~nd

escape to 1 round water should be minimal Unless damaged or

fffected by differential aettling the secondary soil liner

should remain intact and effective into the distant future

One source of damage that can disrupt the continuity of the

tpermeable layers is frost heaving Por this reason the

iapbullrmeable lay r should ~ wholly belov the averaye depth of

frost penetration in th area Thia may necessitate a thicker

c p th n would otherwise be n ceaa ry

on of th or difficult pro l ma aaaociated with deshy

aQning final co r for landfllla 1 how to allow for settling

nd subsidenc s tling occurs r sult of natural

c ac ton and co olid tlon nd biological degradation of

0 nic lt r 1 t1v y un to ly dhtributed and

ly occur ahort y a t r cloture Subaidence is

a inc 1 nda to be unevenly diatribshy

u ult n cS f ren l lIQ which in turn can

ll

I I I I

cause ~iaruption in conti~uity of the final cover It moat often

cure as the result of final release of liqui~a ~rom and

collapae of drums Subaid~ncbull may not occur for a number of

years following closure For new landfills and for new cella not locbulltbulld over ~xiating celle middoteubaidence due to drum C9llapae

ahoul~ not be a problem As of March 27 1982 liquids in conshy

-tainera have been essentially banned from landfill~ (47 FR 12316)

EPA intends to develop specific ~eaign requirementbull Which

will ensure adequate allowance for settling and eubaidence As

of thie writing however tle Agency lackbull sufficient information

to ~udge the effectiveness of various deai~n options Therefore

this guidance suggests simply that ownera and operatorbull eetimate

the amount of subsidence and allow for it in the fin 1 cover deeign

a beat they can The final result abould be a minimum tbre

ercent final elope after aettling and aubaidence During the poat-cloaure period th r4tgulationa require tbat the d ging

effecta o~ aettling and aubaidenc ( g dieruption of the

continuity and elope of the firal co r) be repair d It tlua

behoovebull the owner or operator to de uat ly Uo tor eub id nc

and aettling Aa th Agency e luat bull altern t1 ode of

d aigniog f n 1 cover to ff cti ly llow for aettli

urtler guid c or

regul tiona co ring th aubj ct

auggeation ich own r

bull o at 1 at rt

n bull ia o at bull in 1 clo 0 t

in ov l

bull

EPA to le~li~wt that thP moat se-vere eubaideonce and settling

problema occur rather aoon after closure It may be preferable

therefore from both an environmental and coat atandpoint to

delay placement of the relatively exP-naive final cover for aix

middotmontha or more in thoae caaea Where aubatantial subsidence or

settling are expected By so doing expensive repairs to the-middot final cover may be avoided lhia would require an extension in

the 180 day limit to the closure period impoaed in Subpart G

In deciding Whether to ~rant auch an extension in accordance

vith th~ rulea of Subpart G the pPrmitting official will

normally reauire iratallation of an expendable interim cover

capable of minimizing precipitati~n- migration into the landfill

unleaa it is clear that the liner and leachate collection

ayatema are functioning and are expected to continue to function

during th extend~~ closure ~riod The A~ency solicits inforshy

mation on the effectiveneaa of this and other approaches to

dealing with the aettlin9au~aidPnce problem bull

33

1. barcode 556861
2. barcodetext SDMS Doc ID 556861

I I I -I

should not exceed 20 tonsacre usi~ the USDAPniversal Soil

Loss Equation (USLE)J and

(5) Have a surface drainage system capable of conducti~

middot run-off across the cap without fo~in erosion rills and gullies bull

(d) The drainage layer shoulda

(1) Be at least 30 centimeters (12 inchea)middotthick with a sat shy

urated hydraulic conductivity not les8 than 1 X lo-3 ~

cmtaecr

(2) Bave a final bottom slope of at least two percent

after allowance for settling and subsidence

(3) To prevent clogy ing be overlain by a graded ~ranular

or synthetic fabric filter that meets the specifications of

section c 2 b of this guidance and

(4) Be designed so that diacharoe flows freely in the

lateral direction to minimize head on bullnd flow through the low

permeability layer

(e) The low permeability layer should have two componentsamp

(1) The upper component should

(A) Consist of

(B) Be protected from dam~~ge below and above the membrane

by at least 15 centimeterbull (6 inchel) of bedding bullaterial no

coar1er than Unified Soil Clalsification Syat (uses) 1and (SP)

And vhich il free of rock fractured atone debril ~obblea

rubbish roots and Iudden changes in grade (alope) Ibe drainshy

age layer and lower soil (clay) coaaponent Jaay aerv aa bedding

ateriala when in direct cont ct ith ynthtic eapa if they

eet the ap cificationl contain d h r in1

25

I I I I

(C) Have a final uppe~ alope (in contact with the bedding

material) of at least two percent after allowance for settling r

anCI

(D) Be loca~e~ wholly below the aver~bull ~epth of frost

penetration in the area

(2) Tbe lower component ahoulda

(A) Inclu~e at leaat 60 centilleters (24 inches) of soil

recompacte~ to the maximum practical extent but capable if

plbullcbullCI on a flra baae of being recompacte~ to a aaturated

hydraulic conductivity of not more than 1 X lo-7 ~aecr

(B) Have the aoil emplace~ in lifts not exceeCiing 15

cent~eters (6 inchea) before copactlon to maximize the

effectiveneas of compaction

middot (f) In deaig ning the final cover owners an~ operatorbull

shoulCI estimate and accCIIIIIodate the amount of aettling and middot

subsidence expected as a reault ofa bull

(1) The incorporation of containerized liqulds prior to

the ban ~posed March 22 1982 (47 PR l2316)r and

(2) Degra~ation and long-tara conaolidation of waste

3 Discussion

The guidance calla for placing the final cover at closure

of each cell or preferably aa filling of the cell progreases

In soae casea auch aa when operatlo a are con4ucteCI in ultiple

11 ta final co r c nnot be applied until the top cell is filled

teaa aubatanti 1 tnt rt cov r should be pplied to other cella

n ltipla lU andfUl bull

26

I I I I

The Agency believes that a three layer final cover (cap)

will adequately mi~imize infiltration of precipitation which is

the primary purpose of the fina~ cover The final cover a~ts to

minimize infiltration by causing precipitation to run off thro~ h bull bull bull bull bull bull bull 0 bull bull middot bull bull bull bull bull bull bull bullbull

uae of slopes drainage layers and impermeable and slightly bull bullbull bull bull bull bull bull bull bull bull bull bullbull 0 bull bull bull

pe~eampble barriers by minimizing infiltration the generation -middot of leachate will also be minimized thereby reducing long-term

bull bull bull bull bull bull bull bull bull bull bull r bull bull bull bull

discharge of Pllutants to the groun~ water to a bare mintmum To prevent the bullbathtub effect bull ie to prevent the landfill

frCXI f~lling with leachate after closure when the leachate collection aystem ceases to function the final cover must be no

middot more peraeable than the most impermeable component of the liner

ayatez (or of the underlyi~ soils) In this way no more preshy

cipitation h allowed to infiltrate the cell than can escape

thro~h the bottom liner Prevention of the bullbathtub effectbull

ia important to eliminate the possibility o~ surface overflow ormiddot

~ration thro~h porous surface strata The latter phenomenon

ia largely the cause of the problems at Love Canal in N w York

Other functions of the final cover include prev ntion of con~amination

of aurtace run-off prevention of wind dispersal of hazardous

waates and prev ntion of direct contact with hazardoua waatea

by ople nd animala atraylng onto the aite

e top layer should have t least two feet of soU capable

of us ain ng plant speci a which will Uecti ly in ice

o on o f t waa cho1en bee uae it will acc odate

ocSy cov r plant1ngl and 1 typic 1

ra c h n h wa te n nt ndustry today

e EOO

-not have root aystema which can be expected to penetrbulltl beyond

If they penetrate deeper~ middot

they can damage the i~tegrity of the low pe~eability layer

the final elope

should be at least three percent to prevent pooling due to irreyushy

laritiea of the surface and vegetation but leas than five pershy

The Agency recognizee that

operated with multiple vertical lifts or

perce~t may

ownera and operatorbull using different final

alopea ahould determine that an alternate elope will not be

beset with eroaion problema and that it will promote efficient

~riculture Universal Soil

tool for uae in evalshy

The USLS predictbull average annual soil The equation iaa

in tonaacr

ctor tonal ere

middotmiddot bull

I I II

bull

Species planted shou~d not require continuing man-made appli shy

ationa of water or fertilizers to sustain growth since middotsuch 0 bull bull

applications cannot be guaranteed in the long term Application

of water and fertilizer ia of courae acceptable during the middotearly stages of the post-closure care period aa the plant growth

ia being established middot The plant species chosen should also

-middot

the vegetated and drainage layers

After allowance for settling and aubsidence

cent to prevent excessive erosion

perated aa piles limiting final slope to five

not be practical bull

drainage The U~ Department of

Loaa Equation (USLE) ia recommended as a

uating eroaion potential

loaa aa the product of aix quantifiable factora

A bull RXLSCP

where A bull average annual ao11 loaa R bull rainfall and run-off eroaivity It bull soil erodibility f L bull alope-le~ tb fac or 8 bull slop -ateepne ctor C bull cover n f c or P bull practice f

28

I I II

The data necessary as input to this equatioo is described

in Evaluating Cover Systems for Solid and Hazardous Waste middot I

(Sw-867) September 1980 us EPA The maxilum rate o~ ~roaio~

for any part of the cover should not exceed 2 0 middottonsa~re in

or4er to minimize the potential for gully development and fl~ure

maintenance The agricultural data base indicats that rates as middot

low as 13 tonacre are achievable for a sllt-lo~ so~l sloped

4 percent with a blue grass v~etative cover lhe ~ency

believes that 2 tonsacre can be more readily achieved and

does not significantly increase cover maintenance The top

layer should also have some means of conducting run-off (eg

swales or conduits) to safely pass run-off velocities and

volume without eroding the cover

The second layer or drain~e lay r ia analogous in function

to the leachate collection system over the liner It should be

at least 12 inches thick to provide capacity to handle water

from major sustained storm events and should be co~structad of

porous materials (at least 1 X lo-3 ~sec hydraulic conducshy

tivity) Drainage tiles or other collection devices are not

necessary The Agency believes that the ccbina~ton of very

porous aedia a final mini un two p rcent slope after settling

and the lapemeabla nature of the layer bane th ill affactiv ly

conduct precipitation infiltrating the v~etatlve layer off of

the landfill As with the leachate coll c ton the

drainega layer should be ov tlain with a gr du Ot nul r

or synth tic fabric fUt r to pr v nt pl g l o th poro

dia with fin earth p rticlea c r~l d do r th

I I

~ I I

lay~r To prevent fluid ~roc backin9 up into the drainage

layer the diacharge at the ai~e should flow freely

The function of the low permeability layer ia to reject

fluid tranamiaaion thereby cauaing infiltrating precipitation

to ~xit through the drainage layer It ahould conaiat of

at leaat two componentbull lhe upper component ahould be et bull

leaat a 20 mil thick aynthetic membrane While the regulationbull

do not apecity that the final cover Pr~v~~ infiltration the

requirtaent that it be no more permeable than the bottom

liner aa a practical matter neceaaitatee the uee of bull aynthetic

mebrane lhia ia ao b caua the regulatory requirement for

the liner ayatem ~oea apecify that leachate be contained and

thia will ~ tranelated in ~oat cabullbullbullmiddot into a very nearly

iaper1Deable eyntletic merbrane liner

The minimum thickneal rec~bull~de~ ~or the eynthetic component

of the cap (20 mil) ia 1bullbullbull than that apecified for the liner

(30 wdl) becaua (l) the cap ia not expect d to come in contact

with Ch-ical leachatebull Which might haaten failur an~ (2)

once pl ced th potential for ~amage ia am ll ae compared to

ete ia placed onthe potential for underliner dam ge Where

the lin~r t~oughout th op rating life of the cell While

int ct (30 + ye ra in the abeencP o ~ ge) th aynthetic aantl lly prevent t~ af r of pracipit tionccponent wil

ry n r y urooduction ouldhr0l9h it a 4 frbullYDth tic ea a ehould

at eix inchbullbull o ~ t ri 11

y n4 or tin r bull ln

30

bull bull

I I

~ I -I

bull

drainage layer media above the synthetic cap together with

the soil (clay) liner under it can effectively function as

the bedding materialmiddot

middot Even with protection from damage the synthetic cap willmiddotmiddot

not last forever At some point perhaps in the far distant

future the synthetic membrane will degrade A~ that time middot middot middot

the function of Jilnimizing infiltration will fall to the

second component ~ 2-foot minimum clay soil cap with a maximum r

middothydraulic conductivity of 1 X middotlo-7 emsec Altho~h some

all middotamount of precipitation will seep throuuh this secondary

cap the amount of leachate generated will be quite small ~nd

escape to 1 round water should be minimal Unless damaged or

fffected by differential aettling the secondary soil liner

should remain intact and effective into the distant future

One source of damage that can disrupt the continuity of the

tpermeable layers is frost heaving Por this reason the

iapbullrmeable lay r should ~ wholly belov the averaye depth of

frost penetration in th area Thia may necessitate a thicker

c p th n would otherwise be n ceaa ry

on of th or difficult pro l ma aaaociated with deshy

aQning final co r for landfllla 1 how to allow for settling

nd subsidenc s tling occurs r sult of natural

c ac ton and co olid tlon nd biological degradation of

0 nic lt r 1 t1v y un to ly dhtributed and

ly occur ahort y a t r cloture Subaidence is

a inc 1 nda to be unevenly diatribshy

u ult n cS f ren l lIQ which in turn can

ll

I I I I

cause ~iaruption in conti~uity of the final cover It moat often

cure as the result of final release of liqui~a ~rom and

collapae of drums Subaid~ncbull may not occur for a number of

years following closure For new landfills and for new cella not locbulltbulld over ~xiating celle middoteubaidence due to drum C9llapae

ahoul~ not be a problem As of March 27 1982 liquids in conshy

-tainera have been essentially banned from landfill~ (47 FR 12316)

EPA intends to develop specific ~eaign requirementbull Which

will ensure adequate allowance for settling and eubaidence As

of thie writing however tle Agency lackbull sufficient information

to ~udge the effectiveness of various deai~n options Therefore

this guidance suggests simply that ownera and operatorbull eetimate

the amount of subsidence and allow for it in the fin 1 cover deeign

a beat they can The final result abould be a minimum tbre

ercent final elope after aettling and aubaidence During the poat-cloaure period th r4tgulationa require tbat the d ging

effecta o~ aettling and aubaidenc ( g dieruption of the

continuity and elope of the firal co r) be repair d It tlua

behoovebull the owner or operator to de uat ly Uo tor eub id nc

and aettling Aa th Agency e luat bull altern t1 ode of

d aigniog f n 1 cover to ff cti ly llow for aettli

urtler guid c or

regul tiona co ring th aubj ct

auggeation ich own r

bull o at 1 at rt

n bull ia o at bull in 1 clo 0 t

in ov l

bull

EPA to le~li~wt that thP moat se-vere eubaideonce and settling

problema occur rather aoon after closure It may be preferable

therefore from both an environmental and coat atandpoint to

delay placement of the relatively exP-naive final cover for aix

middotmontha or more in thoae caaea Where aubatantial subsidence or

settling are expected By so doing expensive repairs to the-middot final cover may be avoided lhia would require an extension in

the 180 day limit to the closure period impoaed in Subpart G

In deciding Whether to ~rant auch an extension in accordance

vith th~ rulea of Subpart G the pPrmitting official will

normally reauire iratallation of an expendable interim cover

capable of minimizing precipitati~n- migration into the landfill

unleaa it is clear that the liner and leachate collection

ayatema are functioning and are expected to continue to function

during th extend~~ closure ~riod The A~ency solicits inforshy

mation on the effectiveneaa of this and other approaches to

dealing with the aettlin9au~aidPnce problem bull

33

1. barcode 556861
2. barcodetext SDMS Doc ID 556861

I I I I

(C) Have a final uppe~ alope (in contact with the bedding

material) of at least two percent after allowance for settling r

anCI

(D) Be loca~e~ wholly below the aver~bull ~epth of frost

penetration in the area

(2) Tbe lower component ahoulda

(A) Inclu~e at leaat 60 centilleters (24 inches) of soil

recompacte~ to the maximum practical extent but capable if

plbullcbullCI on a flra baae of being recompacte~ to a aaturated

hydraulic conductivity of not more than 1 X lo-7 ~aecr

(B) Have the aoil emplace~ in lifts not exceeCiing 15

cent~eters (6 inchea) before copactlon to maximize the

effectiveneas of compaction

middot (f) In deaig ning the final cover owners an~ operatorbull

shoulCI estimate and accCIIIIIodate the amount of aettling and middot

subsidence expected as a reault ofa bull

(1) The incorporation of containerized liqulds prior to

the ban ~posed March 22 1982 (47 PR l2316)r and

(2) Degra~ation and long-tara conaolidation of waste

3 Discussion

The guidance calla for placing the final cover at closure

of each cell or preferably aa filling of the cell progreases

In soae casea auch aa when operatlo a are con4ucteCI in ultiple

11 ta final co r c nnot be applied until the top cell is filled

teaa aubatanti 1 tnt rt cov r should be pplied to other cella

n ltipla lU andfUl bull

26

I I I I

The Agency believes that a three layer final cover (cap)

will adequately mi~imize infiltration of precipitation which is

the primary purpose of the fina~ cover The final cover a~ts to

minimize infiltration by causing precipitation to run off thro~ h bull bull bull bull bull bull bull 0 bull bull middot bull bull bull bull bull bull bull bullbull

uae of slopes drainage layers and impermeable and slightly bull bullbull bull bull bull bull bull bull bull bull bull bullbull 0 bull bull bull

pe~eampble barriers by minimizing infiltration the generation -middot of leachate will also be minimized thereby reducing long-term

bull bull bull bull bull bull bull bull bull bull bull r bull bull bull bull

discharge of Pllutants to the groun~ water to a bare mintmum To prevent the bullbathtub effect bull ie to prevent the landfill

frCXI f~lling with leachate after closure when the leachate collection aystem ceases to function the final cover must be no

middot more peraeable than the most impermeable component of the liner

ayatez (or of the underlyi~ soils) In this way no more preshy

cipitation h allowed to infiltrate the cell than can escape

thro~h the bottom liner Prevention of the bullbathtub effectbull

ia important to eliminate the possibility o~ surface overflow ormiddot

~ration thro~h porous surface strata The latter phenomenon

ia largely the cause of the problems at Love Canal in N w York

Other functions of the final cover include prev ntion of con~amination

of aurtace run-off prevention of wind dispersal of hazardous

waates and prev ntion of direct contact with hazardoua waatea

by ople nd animala atraylng onto the aite

e top layer should have t least two feet of soU capable

of us ain ng plant speci a which will Uecti ly in ice

o on o f t waa cho1en bee uae it will acc odate

ocSy cov r plant1ngl and 1 typic 1

ra c h n h wa te n nt ndustry today

e EOO

-not have root aystema which can be expected to penetrbulltl beyond

If they penetrate deeper~ middot

they can damage the i~tegrity of the low pe~eability layer

the final elope

should be at least three percent to prevent pooling due to irreyushy

laritiea of the surface and vegetation but leas than five pershy

The Agency recognizee that

operated with multiple vertical lifts or

perce~t may

ownera and operatorbull using different final

alopea ahould determine that an alternate elope will not be

beset with eroaion problema and that it will promote efficient

~riculture Universal Soil

tool for uae in evalshy

The USLS predictbull average annual soil The equation iaa

in tonaacr

ctor tonal ere

middotmiddot bull

I I II

bull

Species planted shou~d not require continuing man-made appli shy

ationa of water or fertilizers to sustain growth since middotsuch 0 bull bull

applications cannot be guaranteed in the long term Application

of water and fertilizer ia of courae acceptable during the middotearly stages of the post-closure care period aa the plant growth

ia being established middot The plant species chosen should also

-middot

the vegetated and drainage layers

After allowance for settling and aubsidence

cent to prevent excessive erosion

perated aa piles limiting final slope to five

not be practical bull

drainage The U~ Department of

Loaa Equation (USLE) ia recommended as a

uating eroaion potential

loaa aa the product of aix quantifiable factora

A bull RXLSCP

where A bull average annual ao11 loaa R bull rainfall and run-off eroaivity It bull soil erodibility f L bull alope-le~ tb fac or 8 bull slop -ateepne ctor C bull cover n f c or P bull practice f

28

I I II

The data necessary as input to this equatioo is described

in Evaluating Cover Systems for Solid and Hazardous Waste middot I

(Sw-867) September 1980 us EPA The maxilum rate o~ ~roaio~

for any part of the cover should not exceed 2 0 middottonsa~re in

or4er to minimize the potential for gully development and fl~ure

maintenance The agricultural data base indicats that rates as middot

low as 13 tonacre are achievable for a sllt-lo~ so~l sloped

4 percent with a blue grass v~etative cover lhe ~ency

believes that 2 tonsacre can be more readily achieved and

does not significantly increase cover maintenance The top

layer should also have some means of conducting run-off (eg

swales or conduits) to safely pass run-off velocities and

volume without eroding the cover

The second layer or drain~e lay r ia analogous in function

to the leachate collection system over the liner It should be

at least 12 inches thick to provide capacity to handle water

from major sustained storm events and should be co~structad of

porous materials (at least 1 X lo-3 ~sec hydraulic conducshy

tivity) Drainage tiles or other collection devices are not

necessary The Agency believes that the ccbina~ton of very

porous aedia a final mini un two p rcent slope after settling

and the lapemeabla nature of the layer bane th ill affactiv ly

conduct precipitation infiltrating the v~etatlve layer off of

the landfill As with the leachate coll c ton the

drainega layer should be ov tlain with a gr du Ot nul r

or synth tic fabric fUt r to pr v nt pl g l o th poro

dia with fin earth p rticlea c r~l d do r th

I I

~ I I

lay~r To prevent fluid ~roc backin9 up into the drainage

layer the diacharge at the ai~e should flow freely

The function of the low permeability layer ia to reject

fluid tranamiaaion thereby cauaing infiltrating precipitation

to ~xit through the drainage layer It ahould conaiat of

at leaat two componentbull lhe upper component ahould be et bull

leaat a 20 mil thick aynthetic membrane While the regulationbull

do not apecity that the final cover Pr~v~~ infiltration the

requirtaent that it be no more permeable than the bottom

liner aa a practical matter neceaaitatee the uee of bull aynthetic

mebrane lhia ia ao b caua the regulatory requirement for

the liner ayatem ~oea apecify that leachate be contained and

thia will ~ tranelated in ~oat cabullbullbullmiddot into a very nearly

iaper1Deable eyntletic merbrane liner

The minimum thickneal rec~bull~de~ ~or the eynthetic component

of the cap (20 mil) ia 1bullbullbull than that apecified for the liner

(30 wdl) becaua (l) the cap ia not expect d to come in contact

with Ch-ical leachatebull Which might haaten failur an~ (2)

once pl ced th potential for ~amage ia am ll ae compared to

ete ia placed onthe potential for underliner dam ge Where

the lin~r t~oughout th op rating life of the cell While

int ct (30 + ye ra in the abeencP o ~ ge) th aynthetic aantl lly prevent t~ af r of pracipit tionccponent wil

ry n r y urooduction ouldhr0l9h it a 4 frbullYDth tic ea a ehould

at eix inchbullbull o ~ t ri 11

y n4 or tin r bull ln

30

bull bull

I I

~ I -I

bull

drainage layer media above the synthetic cap together with

the soil (clay) liner under it can effectively function as

the bedding materialmiddot

middot Even with protection from damage the synthetic cap willmiddotmiddot

not last forever At some point perhaps in the far distant

future the synthetic membrane will degrade A~ that time middot middot middot

the function of Jilnimizing infiltration will fall to the

second component ~ 2-foot minimum clay soil cap with a maximum r

middothydraulic conductivity of 1 X middotlo-7 emsec Altho~h some

all middotamount of precipitation will seep throuuh this secondary

cap the amount of leachate generated will be quite small ~nd

escape to 1 round water should be minimal Unless damaged or

fffected by differential aettling the secondary soil liner

should remain intact and effective into the distant future

One source of damage that can disrupt the continuity of the

tpermeable layers is frost heaving Por this reason the

iapbullrmeable lay r should ~ wholly belov the averaye depth of

frost penetration in th area Thia may necessitate a thicker

c p th n would otherwise be n ceaa ry

on of th or difficult pro l ma aaaociated with deshy

aQning final co r for landfllla 1 how to allow for settling

nd subsidenc s tling occurs r sult of natural

c ac ton and co olid tlon nd biological degradation of

0 nic lt r 1 t1v y un to ly dhtributed and

ly occur ahort y a t r cloture Subaidence is

a inc 1 nda to be unevenly diatribshy

u ult n cS f ren l lIQ which in turn can

ll

I I I I

cause ~iaruption in conti~uity of the final cover It moat often

cure as the result of final release of liqui~a ~rom and

collapae of drums Subaid~ncbull may not occur for a number of

years following closure For new landfills and for new cella not locbulltbulld over ~xiating celle middoteubaidence due to drum C9llapae

ahoul~ not be a problem As of March 27 1982 liquids in conshy

-tainera have been essentially banned from landfill~ (47 FR 12316)

EPA intends to develop specific ~eaign requirementbull Which

will ensure adequate allowance for settling and eubaidence As

of thie writing however tle Agency lackbull sufficient information

to ~udge the effectiveness of various deai~n options Therefore

this guidance suggests simply that ownera and operatorbull eetimate

the amount of subsidence and allow for it in the fin 1 cover deeign

a beat they can The final result abould be a minimum tbre

ercent final elope after aettling and aubaidence During the poat-cloaure period th r4tgulationa require tbat the d ging

effecta o~ aettling and aubaidenc ( g dieruption of the

continuity and elope of the firal co r) be repair d It tlua

behoovebull the owner or operator to de uat ly Uo tor eub id nc

and aettling Aa th Agency e luat bull altern t1 ode of

d aigniog f n 1 cover to ff cti ly llow for aettli

urtler guid c or

regul tiona co ring th aubj ct

auggeation ich own r

bull o at 1 at rt

n bull ia o at bull in 1 clo 0 t

in ov l

bull

EPA to le~li~wt that thP moat se-vere eubaideonce and settling

problema occur rather aoon after closure It may be preferable

therefore from both an environmental and coat atandpoint to

delay placement of the relatively exP-naive final cover for aix

middotmontha or more in thoae caaea Where aubatantial subsidence or

settling are expected By so doing expensive repairs to the-middot final cover may be avoided lhia would require an extension in

the 180 day limit to the closure period impoaed in Subpart G

In deciding Whether to ~rant auch an extension in accordance

vith th~ rulea of Subpart G the pPrmitting official will

normally reauire iratallation of an expendable interim cover

capable of minimizing precipitati~n- migration into the landfill

unleaa it is clear that the liner and leachate collection

ayatema are functioning and are expected to continue to function

during th extend~~ closure ~riod The A~ency solicits inforshy

mation on the effectiveneaa of this and other approaches to

dealing with the aettlin9au~aidPnce problem bull

33

1. barcode 556861
2. barcodetext SDMS Doc ID 556861

I I I I

The Agency believes that a three layer final cover (cap)

will adequately mi~imize infiltration of precipitation which is

the primary purpose of the fina~ cover The final cover a~ts to

minimize infiltration by causing precipitation to run off thro~ h bull bull bull bull bull bull bull 0 bull bull middot bull bull bull bull bull bull bull bullbull

uae of slopes drainage layers and impermeable and slightly bull bullbull bull bull bull bull bull bull bull bull bull bullbull 0 bull bull bull

pe~eampble barriers by minimizing infiltration the generation -middot of leachate will also be minimized thereby reducing long-term

bull bull bull bull bull bull bull bull bull bull bull r bull bull bull bull

discharge of Pllutants to the groun~ water to a bare mintmum To prevent the bullbathtub effect bull ie to prevent the landfill

frCXI f~lling with leachate after closure when the leachate collection aystem ceases to function the final cover must be no

middot more peraeable than the most impermeable component of the liner

ayatez (or of the underlyi~ soils) In this way no more preshy

cipitation h allowed to infiltrate the cell than can escape

thro~h the bottom liner Prevention of the bullbathtub effectbull

ia important to eliminate the possibility o~ surface overflow ormiddot

~ration thro~h porous surface strata The latter phenomenon

ia largely the cause of the problems at Love Canal in N w York

Other functions of the final cover include prev ntion of con~amination

of aurtace run-off prevention of wind dispersal of hazardous

waates and prev ntion of direct contact with hazardoua waatea

by ople nd animala atraylng onto the aite

e top layer should have t least two feet of soU capable

of us ain ng plant speci a which will Uecti ly in ice

o on o f t waa cho1en bee uae it will acc odate

ocSy cov r plant1ngl and 1 typic 1

ra c h n h wa te n nt ndustry today

e EOO

-not have root aystema which can be expected to penetrbulltl beyond

If they penetrate deeper~ middot

they can damage the i~tegrity of the low pe~eability layer

the final elope

should be at least three percent to prevent pooling due to irreyushy

laritiea of the surface and vegetation but leas than five pershy

The Agency recognizee that

operated with multiple vertical lifts or

perce~t may

ownera and operatorbull using different final

alopea ahould determine that an alternate elope will not be

beset with eroaion problema and that it will promote efficient

~riculture Universal Soil

tool for uae in evalshy

The USLS predictbull average annual soil The equation iaa

in tonaacr

ctor tonal ere

middotmiddot bull

I I II

bull

Species planted shou~d not require continuing man-made appli shy

ationa of water or fertilizers to sustain growth since middotsuch 0 bull bull

applications cannot be guaranteed in the long term Application

of water and fertilizer ia of courae acceptable during the middotearly stages of the post-closure care period aa the plant growth

ia being established middot The plant species chosen should also

-middot

the vegetated and drainage layers

After allowance for settling and aubsidence

cent to prevent excessive erosion

perated aa piles limiting final slope to five

not be practical bull

drainage The U~ Department of

Loaa Equation (USLE) ia recommended as a

uating eroaion potential

loaa aa the product of aix quantifiable factora

A bull RXLSCP

where A bull average annual ao11 loaa R bull rainfall and run-off eroaivity It bull soil erodibility f L bull alope-le~ tb fac or 8 bull slop -ateepne ctor C bull cover n f c or P bull practice f

28

I I II

The data necessary as input to this equatioo is described

in Evaluating Cover Systems for Solid and Hazardous Waste middot I

(Sw-867) September 1980 us EPA The maxilum rate o~ ~roaio~

for any part of the cover should not exceed 2 0 middottonsa~re in

or4er to minimize the potential for gully development and fl~ure

maintenance The agricultural data base indicats that rates as middot

low as 13 tonacre are achievable for a sllt-lo~ so~l sloped

4 percent with a blue grass v~etative cover lhe ~ency

believes that 2 tonsacre can be more readily achieved and

does not significantly increase cover maintenance The top

layer should also have some means of conducting run-off (eg

swales or conduits) to safely pass run-off velocities and

volume without eroding the cover

The second layer or drain~e lay r ia analogous in function

to the leachate collection system over the liner It should be

at least 12 inches thick to provide capacity to handle water

from major sustained storm events and should be co~structad of

porous materials (at least 1 X lo-3 ~sec hydraulic conducshy

tivity) Drainage tiles or other collection devices are not

necessary The Agency believes that the ccbina~ton of very

porous aedia a final mini un two p rcent slope after settling

and the lapemeabla nature of the layer bane th ill affactiv ly

conduct precipitation infiltrating the v~etatlve layer off of

the landfill As with the leachate coll c ton the

drainega layer should be ov tlain with a gr du Ot nul r

or synth tic fabric fUt r to pr v nt pl g l o th poro

dia with fin earth p rticlea c r~l d do r th

I I

~ I I

lay~r To prevent fluid ~roc backin9 up into the drainage

layer the diacharge at the ai~e should flow freely

The function of the low permeability layer ia to reject

fluid tranamiaaion thereby cauaing infiltrating precipitation

to ~xit through the drainage layer It ahould conaiat of

at leaat two componentbull lhe upper component ahould be et bull

leaat a 20 mil thick aynthetic membrane While the regulationbull

do not apecity that the final cover Pr~v~~ infiltration the

requirtaent that it be no more permeable than the bottom

liner aa a practical matter neceaaitatee the uee of bull aynthetic

mebrane lhia ia ao b caua the regulatory requirement for

the liner ayatem ~oea apecify that leachate be contained and

thia will ~ tranelated in ~oat cabullbullbullmiddot into a very nearly

iaper1Deable eyntletic merbrane liner

The minimum thickneal rec~bull~de~ ~or the eynthetic component

of the cap (20 mil) ia 1bullbullbull than that apecified for the liner

(30 wdl) becaua (l) the cap ia not expect d to come in contact

with Ch-ical leachatebull Which might haaten failur an~ (2)

once pl ced th potential for ~amage ia am ll ae compared to

ete ia placed onthe potential for underliner dam ge Where

the lin~r t~oughout th op rating life of the cell While

int ct (30 + ye ra in the abeencP o ~ ge) th aynthetic aantl lly prevent t~ af r of pracipit tionccponent wil

ry n r y urooduction ouldhr0l9h it a 4 frbullYDth tic ea a ehould

at eix inchbullbull o ~ t ri 11

y n4 or tin r bull ln

30

bull bull

I I

~ I -I

bull

drainage layer media above the synthetic cap together with

the soil (clay) liner under it can effectively function as

the bedding materialmiddot

middot Even with protection from damage the synthetic cap willmiddotmiddot

not last forever At some point perhaps in the far distant

future the synthetic membrane will degrade A~ that time middot middot middot

the function of Jilnimizing infiltration will fall to the

second component ~ 2-foot minimum clay soil cap with a maximum r

middothydraulic conductivity of 1 X middotlo-7 emsec Altho~h some

all middotamount of precipitation will seep throuuh this secondary

cap the amount of leachate generated will be quite small ~nd

escape to 1 round water should be minimal Unless damaged or

fffected by differential aettling the secondary soil liner

should remain intact and effective into the distant future

One source of damage that can disrupt the continuity of the

tpermeable layers is frost heaving Por this reason the

iapbullrmeable lay r should ~ wholly belov the averaye depth of

frost penetration in th area Thia may necessitate a thicker

c p th n would otherwise be n ceaa ry

on of th or difficult pro l ma aaaociated with deshy

aQning final co r for landfllla 1 how to allow for settling

nd subsidenc s tling occurs r sult of natural

c ac ton and co olid tlon nd biological degradation of

0 nic lt r 1 t1v y un to ly dhtributed and

ly occur ahort y a t r cloture Subaidence is

a inc 1 nda to be unevenly diatribshy

u ult n cS f ren l lIQ which in turn can

ll

I I I I

cause ~iaruption in conti~uity of the final cover It moat often

cure as the result of final release of liqui~a ~rom and

collapae of drums Subaid~ncbull may not occur for a number of

years following closure For new landfills and for new cella not locbulltbulld over ~xiating celle middoteubaidence due to drum C9llapae

ahoul~ not be a problem As of March 27 1982 liquids in conshy

-tainera have been essentially banned from landfill~ (47 FR 12316)

EPA intends to develop specific ~eaign requirementbull Which

will ensure adequate allowance for settling and eubaidence As

of thie writing however tle Agency lackbull sufficient information

to ~udge the effectiveness of various deai~n options Therefore

this guidance suggests simply that ownera and operatorbull eetimate

the amount of subsidence and allow for it in the fin 1 cover deeign

a beat they can The final result abould be a minimum tbre

ercent final elope after aettling and aubaidence During the poat-cloaure period th r4tgulationa require tbat the d ging

effecta o~ aettling and aubaidenc ( g dieruption of the

continuity and elope of the firal co r) be repair d It tlua

behoovebull the owner or operator to de uat ly Uo tor eub id nc

and aettling Aa th Agency e luat bull altern t1 ode of

d aigniog f n 1 cover to ff cti ly llow for aettli

urtler guid c or

regul tiona co ring th aubj ct

auggeation ich own r

bull o at 1 at rt

n bull ia o at bull in 1 clo 0 t

in ov l

bull

EPA to le~li~wt that thP moat se-vere eubaideonce and settling

problema occur rather aoon after closure It may be preferable

therefore from both an environmental and coat atandpoint to

delay placement of the relatively exP-naive final cover for aix

middotmontha or more in thoae caaea Where aubatantial subsidence or

settling are expected By so doing expensive repairs to the-middot final cover may be avoided lhia would require an extension in

the 180 day limit to the closure period impoaed in Subpart G

In deciding Whether to ~rant auch an extension in accordance

vith th~ rulea of Subpart G the pPrmitting official will

normally reauire iratallation of an expendable interim cover

capable of minimizing precipitati~n- migration into the landfill

unleaa it is clear that the liner and leachate collection

ayatema are functioning and are expected to continue to function

during th extend~~ closure ~riod The A~ency solicits inforshy

mation on the effectiveneaa of this and other approaches to

dealing with the aettlin9au~aidPnce problem bull

33

1. barcode 556861
2. barcodetext SDMS Doc ID 556861

-not have root aystema which can be expected to penetrbulltl beyond

If they penetrate deeper~ middot

they can damage the i~tegrity of the low pe~eability layer

the final elope

should be at least three percent to prevent pooling due to irreyushy

laritiea of the surface and vegetation but leas than five pershy

The Agency recognizee that

operated with multiple vertical lifts or

perce~t may

ownera and operatorbull using different final

alopea ahould determine that an alternate elope will not be

beset with eroaion problema and that it will promote efficient

~riculture Universal Soil

tool for uae in evalshy

The USLS predictbull average annual soil The equation iaa

in tonaacr

ctor tonal ere

middotmiddot bull

I I II

bull

Species planted shou~d not require continuing man-made appli shy

ationa of water or fertilizers to sustain growth since middotsuch 0 bull bull

applications cannot be guaranteed in the long term Application

of water and fertilizer ia of courae acceptable during the middotearly stages of the post-closure care period aa the plant growth

ia being established middot The plant species chosen should also

-middot

the vegetated and drainage layers

After allowance for settling and aubsidence

cent to prevent excessive erosion

perated aa piles limiting final slope to five

not be practical bull

drainage The U~ Department of

Loaa Equation (USLE) ia recommended as a

uating eroaion potential

loaa aa the product of aix quantifiable factora

A bull RXLSCP

where A bull average annual ao11 loaa R bull rainfall and run-off eroaivity It bull soil erodibility f L bull alope-le~ tb fac or 8 bull slop -ateepne ctor C bull cover n f c or P bull practice f

28

I I II

The data necessary as input to this equatioo is described

in Evaluating Cover Systems for Solid and Hazardous Waste middot I

(Sw-867) September 1980 us EPA The maxilum rate o~ ~roaio~

for any part of the cover should not exceed 2 0 middottonsa~re in

or4er to minimize the potential for gully development and fl~ure

maintenance The agricultural data base indicats that rates as middot

low as 13 tonacre are achievable for a sllt-lo~ so~l sloped

4 percent with a blue grass v~etative cover lhe ~ency

believes that 2 tonsacre can be more readily achieved and

does not significantly increase cover maintenance The top

layer should also have some means of conducting run-off (eg

swales or conduits) to safely pass run-off velocities and

volume without eroding the cover

The second layer or drain~e lay r ia analogous in function

to the leachate collection system over the liner It should be

at least 12 inches thick to provide capacity to handle water

from major sustained storm events and should be co~structad of

porous materials (at least 1 X lo-3 ~sec hydraulic conducshy

tivity) Drainage tiles or other collection devices are not

necessary The Agency believes that the ccbina~ton of very

porous aedia a final mini un two p rcent slope after settling

and the lapemeabla nature of the layer bane th ill affactiv ly

conduct precipitation infiltrating the v~etatlve layer off of

the landfill As with the leachate coll c ton the

drainega layer should be ov tlain with a gr du Ot nul r

or synth tic fabric fUt r to pr v nt pl g l o th poro

dia with fin earth p rticlea c r~l d do r th

I I

~ I I

lay~r To prevent fluid ~roc backin9 up into the drainage

layer the diacharge at the ai~e should flow freely

The function of the low permeability layer ia to reject

fluid tranamiaaion thereby cauaing infiltrating precipitation

to ~xit through the drainage layer It ahould conaiat of

at leaat two componentbull lhe upper component ahould be et bull

leaat a 20 mil thick aynthetic membrane While the regulationbull

do not apecity that the final cover Pr~v~~ infiltration the

requirtaent that it be no more permeable than the bottom

liner aa a practical matter neceaaitatee the uee of bull aynthetic

mebrane lhia ia ao b caua the regulatory requirement for

the liner ayatem ~oea apecify that leachate be contained and

thia will ~ tranelated in ~oat cabullbullbullmiddot into a very nearly

iaper1Deable eyntletic merbrane liner

The minimum thickneal rec~bull~de~ ~or the eynthetic component

of the cap (20 mil) ia 1bullbullbull than that apecified for the liner

(30 wdl) becaua (l) the cap ia not expect d to come in contact

with Ch-ical leachatebull Which might haaten failur an~ (2)

once pl ced th potential for ~amage ia am ll ae compared to

ete ia placed onthe potential for underliner dam ge Where

the lin~r t~oughout th op rating life of the cell While

int ct (30 + ye ra in the abeencP o ~ ge) th aynthetic aantl lly prevent t~ af r of pracipit tionccponent wil

ry n r y urooduction ouldhr0l9h it a 4 frbullYDth tic ea a ehould

at eix inchbullbull o ~ t ri 11

y n4 or tin r bull ln

30

bull bull

I I

~ I -I

bull

drainage layer media above the synthetic cap together with

the soil (clay) liner under it can effectively function as

the bedding materialmiddot

middot Even with protection from damage the synthetic cap willmiddotmiddot

not last forever At some point perhaps in the far distant

future the synthetic membrane will degrade A~ that time middot middot middot

the function of Jilnimizing infiltration will fall to the

second component ~ 2-foot minimum clay soil cap with a maximum r

middothydraulic conductivity of 1 X middotlo-7 emsec Altho~h some

all middotamount of precipitation will seep throuuh this secondary

cap the amount of leachate generated will be quite small ~nd

escape to 1 round water should be minimal Unless damaged or

fffected by differential aettling the secondary soil liner

should remain intact and effective into the distant future

One source of damage that can disrupt the continuity of the

tpermeable layers is frost heaving Por this reason the

iapbullrmeable lay r should ~ wholly belov the averaye depth of

frost penetration in th area Thia may necessitate a thicker

c p th n would otherwise be n ceaa ry

on of th or difficult pro l ma aaaociated with deshy

aQning final co r for landfllla 1 how to allow for settling

nd subsidenc s tling occurs r sult of natural

c ac ton and co olid tlon nd biological degradation of

0 nic lt r 1 t1v y un to ly dhtributed and

ly occur ahort y a t r cloture Subaidence is

a inc 1 nda to be unevenly diatribshy

u ult n cS f ren l lIQ which in turn can

ll

I I I I

cause ~iaruption in conti~uity of the final cover It moat often

cure as the result of final release of liqui~a ~rom and

collapae of drums Subaid~ncbull may not occur for a number of

years following closure For new landfills and for new cella not locbulltbulld over ~xiating celle middoteubaidence due to drum C9llapae

ahoul~ not be a problem As of March 27 1982 liquids in conshy

-tainera have been essentially banned from landfill~ (47 FR 12316)

EPA intends to develop specific ~eaign requirementbull Which

will ensure adequate allowance for settling and eubaidence As

of thie writing however tle Agency lackbull sufficient information

to ~udge the effectiveness of various deai~n options Therefore

this guidance suggests simply that ownera and operatorbull eetimate

the amount of subsidence and allow for it in the fin 1 cover deeign

a beat they can The final result abould be a minimum tbre

ercent final elope after aettling and aubaidence During the poat-cloaure period th r4tgulationa require tbat the d ging

effecta o~ aettling and aubaidenc ( g dieruption of the

continuity and elope of the firal co r) be repair d It tlua

behoovebull the owner or operator to de uat ly Uo tor eub id nc

and aettling Aa th Agency e luat bull altern t1 ode of

d aigniog f n 1 cover to ff cti ly llow for aettli

urtler guid c or

regul tiona co ring th aubj ct

auggeation ich own r

bull o at 1 at rt

n bull ia o at bull in 1 clo 0 t

in ov l

bull

EPA to le~li~wt that thP moat se-vere eubaideonce and settling

problema occur rather aoon after closure It may be preferable

therefore from both an environmental and coat atandpoint to

delay placement of the relatively exP-naive final cover for aix

middotmontha or more in thoae caaea Where aubatantial subsidence or

settling are expected By so doing expensive repairs to the-middot final cover may be avoided lhia would require an extension in

the 180 day limit to the closure period impoaed in Subpart G

In deciding Whether to ~rant auch an extension in accordance

vith th~ rulea of Subpart G the pPrmitting official will

normally reauire iratallation of an expendable interim cover

capable of minimizing precipitati~n- migration into the landfill

unleaa it is clear that the liner and leachate collection

ayatema are functioning and are expected to continue to function

during th extend~~ closure ~riod The A~ency solicits inforshy

mation on the effectiveneaa of this and other approaches to

dealing with the aettlin9au~aidPnce problem bull

33

1. barcode 556861
2. barcodetext SDMS Doc ID 556861

I I II

The data necessary as input to this equatioo is described

in Evaluating Cover Systems for Solid and Hazardous Waste middot I

(Sw-867) September 1980 us EPA The maxilum rate o~ ~roaio~

for any part of the cover should not exceed 2 0 middottonsa~re in

or4er to minimize the potential for gully development and fl~ure

maintenance The agricultural data base indicats that rates as middot

low as 13 tonacre are achievable for a sllt-lo~ so~l sloped

4 percent with a blue grass v~etative cover lhe ~ency

believes that 2 tonsacre can be more readily achieved and

does not significantly increase cover maintenance The top

layer should also have some means of conducting run-off (eg

swales or conduits) to safely pass run-off velocities and

volume without eroding the cover

The second layer or drain~e lay r ia analogous in function

to the leachate collection system over the liner It should be

at least 12 inches thick to provide capacity to handle water

from major sustained storm events and should be co~structad of

porous materials (at least 1 X lo-3 ~sec hydraulic conducshy

tivity) Drainage tiles or other collection devices are not

necessary The Agency believes that the ccbina~ton of very

porous aedia a final mini un two p rcent slope after settling

and the lapemeabla nature of the layer bane th ill affactiv ly

conduct precipitation infiltrating the v~etatlve layer off of

the landfill As with the leachate coll c ton the

drainega layer should be ov tlain with a gr du Ot nul r

or synth tic fabric fUt r to pr v nt pl g l o th poro

dia with fin earth p rticlea c r~l d do r th

I I

~ I I

lay~r To prevent fluid ~roc backin9 up into the drainage

layer the diacharge at the ai~e should flow freely

The function of the low permeability layer ia to reject

fluid tranamiaaion thereby cauaing infiltrating precipitation

to ~xit through the drainage layer It ahould conaiat of

at leaat two componentbull lhe upper component ahould be et bull

leaat a 20 mil thick aynthetic membrane While the regulationbull

do not apecity that the final cover Pr~v~~ infiltration the

requirtaent that it be no more permeable than the bottom

liner aa a practical matter neceaaitatee the uee of bull aynthetic

mebrane lhia ia ao b caua the regulatory requirement for

the liner ayatem ~oea apecify that leachate be contained and

thia will ~ tranelated in ~oat cabullbullbullmiddot into a very nearly

iaper1Deable eyntletic merbrane liner

The minimum thickneal rec~bull~de~ ~or the eynthetic component

of the cap (20 mil) ia 1bullbullbull than that apecified for the liner

(30 wdl) becaua (l) the cap ia not expect d to come in contact

with Ch-ical leachatebull Which might haaten failur an~ (2)

once pl ced th potential for ~amage ia am ll ae compared to

ete ia placed onthe potential for underliner dam ge Where

the lin~r t~oughout th op rating life of the cell While

int ct (30 + ye ra in the abeencP o ~ ge) th aynthetic aantl lly prevent t~ af r of pracipit tionccponent wil

ry n r y urooduction ouldhr0l9h it a 4 frbullYDth tic ea a ehould

at eix inchbullbull o ~ t ri 11

y n4 or tin r bull ln

30

bull bull

I I

~ I -I

bull

drainage layer media above the synthetic cap together with

the soil (clay) liner under it can effectively function as

the bedding materialmiddot

middot Even with protection from damage the synthetic cap willmiddotmiddot

not last forever At some point perhaps in the far distant

future the synthetic membrane will degrade A~ that time middot middot middot

the function of Jilnimizing infiltration will fall to the

second component ~ 2-foot minimum clay soil cap with a maximum r

middothydraulic conductivity of 1 X middotlo-7 emsec Altho~h some

all middotamount of precipitation will seep throuuh this secondary

cap the amount of leachate generated will be quite small ~nd

escape to 1 round water should be minimal Unless damaged or

fffected by differential aettling the secondary soil liner

should remain intact and effective into the distant future

One source of damage that can disrupt the continuity of the

tpermeable layers is frost heaving Por this reason the

iapbullrmeable lay r should ~ wholly belov the averaye depth of

frost penetration in th area Thia may necessitate a thicker

c p th n would otherwise be n ceaa ry

on of th or difficult pro l ma aaaociated with deshy

aQning final co r for landfllla 1 how to allow for settling

nd subsidenc s tling occurs r sult of natural

c ac ton and co olid tlon nd biological degradation of

0 nic lt r 1 t1v y un to ly dhtributed and

ly occur ahort y a t r cloture Subaidence is

a inc 1 nda to be unevenly diatribshy

u ult n cS f ren l lIQ which in turn can

ll

I I I I

cause ~iaruption in conti~uity of the final cover It moat often

cure as the result of final release of liqui~a ~rom and

collapae of drums Subaid~ncbull may not occur for a number of

years following closure For new landfills and for new cella not locbulltbulld over ~xiating celle middoteubaidence due to drum C9llapae

ahoul~ not be a problem As of March 27 1982 liquids in conshy

-tainera have been essentially banned from landfill~ (47 FR 12316)

EPA intends to develop specific ~eaign requirementbull Which

will ensure adequate allowance for settling and eubaidence As

of thie writing however tle Agency lackbull sufficient information

to ~udge the effectiveness of various deai~n options Therefore

this guidance suggests simply that ownera and operatorbull eetimate

the amount of subsidence and allow for it in the fin 1 cover deeign

a beat they can The final result abould be a minimum tbre

ercent final elope after aettling and aubaidence During the poat-cloaure period th r4tgulationa require tbat the d ging

effecta o~ aettling and aubaidenc ( g dieruption of the

continuity and elope of the firal co r) be repair d It tlua

behoovebull the owner or operator to de uat ly Uo tor eub id nc

and aettling Aa th Agency e luat bull altern t1 ode of

d aigniog f n 1 cover to ff cti ly llow for aettli

urtler guid c or

regul tiona co ring th aubj ct

auggeation ich own r

bull o at 1 at rt

n bull ia o at bull in 1 clo 0 t

in ov l

bull

EPA to le~li~wt that thP moat se-vere eubaideonce and settling

problema occur rather aoon after closure It may be preferable

therefore from both an environmental and coat atandpoint to

delay placement of the relatively exP-naive final cover for aix

middotmontha or more in thoae caaea Where aubatantial subsidence or

settling are expected By so doing expensive repairs to the-middot final cover may be avoided lhia would require an extension in

the 180 day limit to the closure period impoaed in Subpart G

In deciding Whether to ~rant auch an extension in accordance

vith th~ rulea of Subpart G the pPrmitting official will

normally reauire iratallation of an expendable interim cover

capable of minimizing precipitati~n- migration into the landfill

unleaa it is clear that the liner and leachate collection

ayatema are functioning and are expected to continue to function

during th extend~~ closure ~riod The A~ency solicits inforshy

mation on the effectiveneaa of this and other approaches to

dealing with the aettlin9au~aidPnce problem bull

33

1. barcode 556861
2. barcodetext SDMS Doc ID 556861

I I

~ I I

lay~r To prevent fluid ~roc backin9 up into the drainage

layer the diacharge at the ai~e should flow freely

The function of the low permeability layer ia to reject

fluid tranamiaaion thereby cauaing infiltrating precipitation

to ~xit through the drainage layer It ahould conaiat of

at leaat two componentbull lhe upper component ahould be et bull

leaat a 20 mil thick aynthetic membrane While the regulationbull

do not apecity that the final cover Pr~v~~ infiltration the

requirtaent that it be no more permeable than the bottom

liner aa a practical matter neceaaitatee the uee of bull aynthetic

mebrane lhia ia ao b caua the regulatory requirement for

the liner ayatem ~oea apecify that leachate be contained and

thia will ~ tranelated in ~oat cabullbullbullmiddot into a very nearly

iaper1Deable eyntletic merbrane liner

The minimum thickneal rec~bull~de~ ~or the eynthetic component

of the cap (20 mil) ia 1bullbullbull than that apecified for the liner

(30 wdl) becaua (l) the cap ia not expect d to come in contact

with Ch-ical leachatebull Which might haaten failur an~ (2)

once pl ced th potential for ~amage ia am ll ae compared to

ete ia placed onthe potential for underliner dam ge Where

the lin~r t~oughout th op rating life of the cell While

int ct (30 + ye ra in the abeencP o ~ ge) th aynthetic aantl lly prevent t~ af r of pracipit tionccponent wil

ry n r y urooduction ouldhr0l9h it a 4 frbullYDth tic ea a ehould

at eix inchbullbull o ~ t ri 11

y n4 or tin r bull ln

30

bull bull

I I

~ I -I

bull

drainage layer media above the synthetic cap together with

the soil (clay) liner under it can effectively function as

the bedding materialmiddot

middot Even with protection from damage the synthetic cap willmiddotmiddot

not last forever At some point perhaps in the far distant

future the synthetic membrane will degrade A~ that time middot middot middot

the function of Jilnimizing infiltration will fall to the

second component ~ 2-foot minimum clay soil cap with a maximum r

middothydraulic conductivity of 1 X middotlo-7 emsec Altho~h some

all middotamount of precipitation will seep throuuh this secondary

cap the amount of leachate generated will be quite small ~nd

escape to 1 round water should be minimal Unless damaged or

fffected by differential aettling the secondary soil liner

should remain intact and effective into the distant future

One source of damage that can disrupt the continuity of the

tpermeable layers is frost heaving Por this reason the

iapbullrmeable lay r should ~ wholly belov the averaye depth of

frost penetration in th area Thia may necessitate a thicker

c p th n would otherwise be n ceaa ry

on of th or difficult pro l ma aaaociated with deshy

aQning final co r for landfllla 1 how to allow for settling

nd subsidenc s tling occurs r sult of natural

c ac ton and co olid tlon nd biological degradation of

0 nic lt r 1 t1v y un to ly dhtributed and

ly occur ahort y a t r cloture Subaidence is

a inc 1 nda to be unevenly diatribshy

u ult n cS f ren l lIQ which in turn can

ll

I I I I

cause ~iaruption in conti~uity of the final cover It moat often

cure as the result of final release of liqui~a ~rom and

collapae of drums Subaid~ncbull may not occur for a number of

years following closure For new landfills and for new cella not locbulltbulld over ~xiating celle middoteubaidence due to drum C9llapae

ahoul~ not be a problem As of March 27 1982 liquids in conshy

-tainera have been essentially banned from landfill~ (47 FR 12316)

EPA intends to develop specific ~eaign requirementbull Which

will ensure adequate allowance for settling and eubaidence As

of thie writing however tle Agency lackbull sufficient information

to ~udge the effectiveness of various deai~n options Therefore

this guidance suggests simply that ownera and operatorbull eetimate

the amount of subsidence and allow for it in the fin 1 cover deeign

a beat they can The final result abould be a minimum tbre

ercent final elope after aettling and aubaidence During the poat-cloaure period th r4tgulationa require tbat the d ging

effecta o~ aettling and aubaidenc ( g dieruption of the

continuity and elope of the firal co r) be repair d It tlua

behoovebull the owner or operator to de uat ly Uo tor eub id nc

and aettling Aa th Agency e luat bull altern t1 ode of

d aigniog f n 1 cover to ff cti ly llow for aettli

urtler guid c or

regul tiona co ring th aubj ct

auggeation ich own r

bull o at 1 at rt

n bull ia o at bull in 1 clo 0 t

in ov l

bull

EPA to le~li~wt that thP moat se-vere eubaideonce and settling

problema occur rather aoon after closure It may be preferable

therefore from both an environmental and coat atandpoint to

delay placement of the relatively exP-naive final cover for aix

middotmontha or more in thoae caaea Where aubatantial subsidence or

settling are expected By so doing expensive repairs to the-middot final cover may be avoided lhia would require an extension in

the 180 day limit to the closure period impoaed in Subpart G

In deciding Whether to ~rant auch an extension in accordance

vith th~ rulea of Subpart G the pPrmitting official will

normally reauire iratallation of an expendable interim cover

capable of minimizing precipitati~n- migration into the landfill

unleaa it is clear that the liner and leachate collection

ayatema are functioning and are expected to continue to function

during th extend~~ closure ~riod The A~ency solicits inforshy

mation on the effectiveneaa of this and other approaches to

dealing with the aettlin9au~aidPnce problem bull

33

1. barcode 556861
2. barcodetext SDMS Doc ID 556861

bull bull

I I

~ I -I

bull

drainage layer media above the synthetic cap together with

the soil (clay) liner under it can effectively function as

the bedding materialmiddot

middot Even with protection from damage the synthetic cap willmiddotmiddot

not last forever At some point perhaps in the far distant

future the synthetic membrane will degrade A~ that time middot middot middot

the function of Jilnimizing infiltration will fall to the

second component ~ 2-foot minimum clay soil cap with a maximum r

middothydraulic conductivity of 1 X middotlo-7 emsec Altho~h some

all middotamount of precipitation will seep throuuh this secondary

cap the amount of leachate generated will be quite small ~nd

escape to 1 round water should be minimal Unless damaged or

fffected by differential aettling the secondary soil liner

should remain intact and effective into the distant future

One source of damage that can disrupt the continuity of the

tpermeable layers is frost heaving Por this reason the

iapbullrmeable lay r should ~ wholly belov the averaye depth of

frost penetration in th area Thia may necessitate a thicker

c p th n would otherwise be n ceaa ry

on of th or difficult pro l ma aaaociated with deshy

aQning final co r for landfllla 1 how to allow for settling

nd subsidenc s tling occurs r sult of natural

c ac ton and co olid tlon nd biological degradation of

0 nic lt r 1 t1v y un to ly dhtributed and

ly occur ahort y a t r cloture Subaidence is

a inc 1 nda to be unevenly diatribshy

u ult n cS f ren l lIQ which in turn can

ll

I I I I

cause ~iaruption in conti~uity of the final cover It moat often

cure as the result of final release of liqui~a ~rom and

collapae of drums Subaid~ncbull may not occur for a number of

years following closure For new landfills and for new cella not locbulltbulld over ~xiating celle middoteubaidence due to drum C9llapae

ahoul~ not be a problem As of March 27 1982 liquids in conshy

-tainera have been essentially banned from landfill~ (47 FR 12316)

EPA intends to develop specific ~eaign requirementbull Which

will ensure adequate allowance for settling and eubaidence As

of thie writing however tle Agency lackbull sufficient information

to ~udge the effectiveness of various deai~n options Therefore

this guidance suggests simply that ownera and operatorbull eetimate

the amount of subsidence and allow for it in the fin 1 cover deeign

a beat they can The final result abould be a minimum tbre

ercent final elope after aettling and aubaidence During the poat-cloaure period th r4tgulationa require tbat the d ging

effecta o~ aettling and aubaidenc ( g dieruption of the

continuity and elope of the firal co r) be repair d It tlua

behoovebull the owner or operator to de uat ly Uo tor eub id nc

and aettling Aa th Agency e luat bull altern t1 ode of

d aigniog f n 1 cover to ff cti ly llow for aettli

urtler guid c or

regul tiona co ring th aubj ct

auggeation ich own r

bull o at 1 at rt

n bull ia o at bull in 1 clo 0 t

in ov l

bull

EPA to le~li~wt that thP moat se-vere eubaideonce and settling

problema occur rather aoon after closure It may be preferable

therefore from both an environmental and coat atandpoint to

delay placement of the relatively exP-naive final cover for aix

middotmontha or more in thoae caaea Where aubatantial subsidence or

settling are expected By so doing expensive repairs to the-middot final cover may be avoided lhia would require an extension in

the 180 day limit to the closure period impoaed in Subpart G

In deciding Whether to ~rant auch an extension in accordance

vith th~ rulea of Subpart G the pPrmitting official will

normally reauire iratallation of an expendable interim cover

capable of minimizing precipitati~n- migration into the landfill

unleaa it is clear that the liner and leachate collection

ayatema are functioning and are expected to continue to function

during th extend~~ closure ~riod The A~ency solicits inforshy

mation on the effectiveneaa of this and other approaches to

dealing with the aettlin9au~aidPnce problem bull

33

1. barcode 556861
2. barcodetext SDMS Doc ID 556861

I I I I

cause ~iaruption in conti~uity of the final cover It moat often

cure as the result of final release of liqui~a ~rom and

collapae of drums Subaid~ncbull may not occur for a number of

years following closure For new landfills and for new cella not locbulltbulld over ~xiating celle middoteubaidence due to drum C9llapae

ahoul~ not be a problem As of March 27 1982 liquids in conshy

-tainera have been essentially banned from landfill~ (47 FR 12316)

EPA intends to develop specific ~eaign requirementbull Which

will ensure adequate allowance for settling and eubaidence As

of thie writing however tle Agency lackbull sufficient information

to ~udge the effectiveness of various deai~n options Therefore

this guidance suggests simply that ownera and operatorbull eetimate

the amount of subsidence and allow for it in the fin 1 cover deeign

a beat they can The final result abould be a minimum tbre

ercent final elope after aettling and aubaidence During the poat-cloaure period th r4tgulationa require tbat the d ging

effecta o~ aettling and aubaidenc ( g dieruption of the

continuity and elope of the firal co r) be repair d It tlua

behoovebull the owner or operator to de uat ly Uo tor eub id nc

and aettling Aa th Agency e luat bull altern t1 ode of

d aigniog f n 1 cover to ff cti ly llow for aettli

urtler guid c or

regul tiona co ring th aubj ct

auggeation ich own r

bull o at 1 at rt

n bull ia o at bull in 1 clo 0 t

in ov l

bull

EPA to le~li~wt that thP moat se-vere eubaideonce and settling

problema occur rather aoon after closure It may be preferable

therefore from both an environmental and coat atandpoint to

delay placement of the relatively exP-naive final cover for aix

middotmontha or more in thoae caaea Where aubatantial subsidence or

settling are expected By so doing expensive repairs to the-middot final cover may be avoided lhia would require an extension in

the 180 day limit to the closure period impoaed in Subpart G

In deciding Whether to ~rant auch an extension in accordance

vith th~ rulea of Subpart G the pPrmitting official will

normally reauire iratallation of an expendable interim cover

capable of minimizing precipitati~n- migration into the landfill

unleaa it is clear that the liner and leachate collection

ayatema are functioning and are expected to continue to function

during th extend~~ closure ~riod The A~ency solicits inforshy

mation on the effectiveneaa of this and other approaches to

dealing with the aettlin9au~aidPnce problem bull

33

1. barcode 556861
2. barcodetext SDMS Doc ID 556861

bull

EPA to le~li~wt that thP moat se-vere eubaideonce and settling

problema occur rather aoon after closure It may be preferable

therefore from both an environmental and coat atandpoint to

delay placement of the relatively exP-naive final cover for aix

middotmontha or more in thoae caaea Where aubatantial subsidence or

settling are expected By so doing expensive repairs to the-middot final cover may be avoided lhia would require an extension in

the 180 day limit to the closure period impoaed in Subpart G

In deciding Whether to ~rant auch an extension in accordance

vith th~ rulea of Subpart G the pPrmitting official will

normally reauire iratallation of an expendable interim cover

capable of minimizing precipitati~n- migration into the landfill

unleaa it is clear that the liner and leachate collection

ayatema are functioning and are expected to continue to function

during th extend~~ closure ~riod The A~ency solicits inforshy

mation on the effectiveneaa of this and other approaches to

dealing with the aettlin9au~aidPnce problem bull

33

1. barcode 556861
2. barcodetext SDMS Doc ID 556861