## ADMINISTRATIVE

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Explanatio n o f Significan t Difference s F o r Th e Midval e Sla g Operabl e Unit On e Superfun d Site *^ ?

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## S f Fi L INTRODUCTIO N Thi s Explanatio n o f Significan t Difference s (ESD ) ha s bee n prepare d t o documen t th e change s t o t h e Midval e Slag

, Operabl e Uni t No

. 1 (OU1 ) Superfun d Site Recor d o f Decisio n (ROD)

. Th e RO D was issue d b y th e U.S

. Environmenta l Protectio n Agenc y (EPA ) o n Apri l 28

, 1995

. Th e selecte d remed y i s describe d i n th e RO D a s Alternativ e 3

. T h e Uta h Departmen t o f Environmenta l Qualit y (UDEQ ) i s th e lea d agenc y a t th e site

, wit h suppor t provide d b y the EPA

. The changes t o the RO D hav e bee n mad e a s a resul t o f ne w informatio n tha t UDE Q an d th e EP A receive d subsequen t t o th e issuanc e o f th e ROD

. Thi s ES D wil l addres s two change s t o the remed y presente d i n the RO D and ar e describe d i n detai l late r i n this document

. Thes e change s d o no t fundamentall y alte r th e sitewid e remed y presente d in th e ROD

. Th e modifie d remed y wil l remai n protectiv e o f huma n healt h an d th e environment

. Thi s ES D i s prepare d i n fulfillmen t o f EPA' s publi c participatio n responsibilitie s unde r Sectio n 117(c ) o f th e Comprehensiv e Environmenta l Response

, Compensation

, an d Liabilit y Ac t o f 1980

, 4 2 U.S.C

. Sectio n 9601

, e t seq

. (CERCLA)

, a s amende d b y th e Superfun d Amendment s

a n d Reauthorizatio n Ac t o f 198 6 (SARA)

, an d Sectio n 300.435(c)(2)(i ) o f th e Nationa l Oi l an d Hazardou s Substance s Contingenc y Pla n (NCP)

, 4 0 Cod e o f Federa l Regulation s (CFR ) Part 300

. Thes e law s and regulation s requir e EP A t o publis h a n ES D whe n the remed y t o b e implemente d differ s significantl y fro m th e remed y describe d i n th e ROD

. Thi s ES D an d supportin g documentatio n wil l becom e a permanen t par t o f th e administrativ e

recor d fil e fo r th e sit e an d i s availabl e fo r publi c revie w a t th e followin g locations : E P A Superfun d Record s Cente r 9 9 9 18t h Street

, Fift h Floo r Denver

, Colorad o 8020 2 Hours : Monday-Frida y 8:0 0 am"

- 4:30p m Telephone : (303)312-647 3 Uta h Departmen t o f Environmenta l Qualit y Divisio n o f Environmenta l Respons e an d Remediatio n 1 6 8 Nort h 195 0 West

, Firs t Floo r Sal t Lake City

, Uta h 8411 6 Hours : Monday-Frida y 8:00a m - 5:00pm Telephone : (801)536-447 9Tyle r

Branc h Librar y 3 1 5 Sout h Woo d Midvale

, Uta h 8404 7 SUMMAR Y O F SIT E HISTORY

, CONTAMINATIO N

PROBLEMS

, AN D SELECTE D REMED Y Littl e informatio n i s availabl e describin g historica l activitie s o n OU 1 prio r t o th e 1940's

. Befor e tha t time

, i t i s generall y believe d tha t th e lan d wa s use d a s pastur e wit h no industria l activities

. A 195 2 aeria l photograp h o f th e souther n two-third s o f OU 1 showe d n o evidenc e o f commercial/industria l

us e o r disturbe d groun d wit h th e exceptio n o f a smal l landfill (les s tha n 1

acre ) an d a n associate d unpave d road

. Disposa l o f domesti c tras h an d househol d good s occurre d

o n th e southwes t corne r o f th e L F Parce l fro m approximatel y th e 1940' s unti l a landfill wa s establishe d b y th e count y i n th e 1960's

. Th e Sout h Valle y Wate r Reclamatio n Distric t operate d t h e Midval e WWT P o n th e Midval e OU 1 Sit e (L R Parcel ) fro m 195 9 unti l 1986

. Th e plan t originall y consiste d o f a tricklin g filte r system

. A n aerated lagoo n syste m consistin g o f thre e lagoon s wa s adde d i n 197 6 an d operate d until th e closur e o f th e WWT P i n 1986

. Th e lagoon s

wer e close d accordin g t o a n approve d Closur e Pla n and materia l excavate d a s par t o f the Interstat e Highwa y 21 5 constructio n projec t wa s subsequentl y deposite d o n th e forme r lagoo n location

. Th e lan d t o th e sout h o f th e Midval e Sla g OU 1 Sit e wa s th e sit e o f historica l smeltin g activitie s beginnin g i n 1871 an d endin g i n 1958

. I t i s th e smeltin g activitie s tha t ar e presume d t o accoun t fo r th e contaminant s detecte d a t OU1

. T h e forme r smelte r sit e i s bein g addresse d unde r CERCL A a s Operabl e Uni t 2 o f th e Midval e Sla g Site

. Ther e ar e n o known discret e wast e source s a t OU1

. Th e onl y suspecte d wast e feature s withi n th e OU 1 boundarie s ar e th e smal l landfill an d abandone d WWT P an d associate d lagoons

. Sit e characterizatio n dat a sugges t tha t bot h o f th e feature s hav e no t contribute d t o elevate d level s

o f th e contaminant s o f concern (arsenic

, cadmium

, an d lead ) detecte d i n sit e soils

. I t i s inferre d fro m availabl e dat a tha t th e meta l (an d metalloid ) contaminant s detecte d o n OU 1 ar e derive d fro m discret e wast e source s identifie d o n OU2

. T h e transpor t mechanism s postulate d t o accoun t fo r contaminant s a t OU 1 includ e th e following : Win d transpor t o f sla g dus t ont o OU 1 fro m sla g pile s o n OU2

. • Surfac e wate r transpor t o f sla g dus t an d possibl e large r particle s ont o O U 1 fro m sla g pile s

o n OU2

. • Fallou t o f smelte r fum e ont o OU 1 fro m smelte r chimney s o n OU 2 and/o r th e sout h chimne y o n OU 1 o f th e Sharo n Stee l site

. • Deliberat e placemen t o f sla g an d possibl e othe r smelte r wast e ont o OU 1 t o fil l wetland s

o r othe r lo w areas, an d t o san d road s i n the Wincheste r Estate s developmen t durin g sno w

o r ic e events

. T h e majo r component s o f th e selecte d remedy

, as presente d in th e ROD

, includ e th e following :

• Excavatin g nativ e surfac e soil s a t 1 4 residentia l yard s (Parce l WENW ) t o a minimu mdept

h o f 1 8 inche s wit h confirmatory samplin g t o identif y area s requirin g additiona l excavation

. Clea n fil l i s t o b e importe d t o restor e th e origina l grade

, an d eac h yar d wil l b e restore d a s closel y a s possibl e t o it s origina l condition

. Th e wastes

, bein g non

hazardous

, woul d b e transporte d t o th e neares t soli d wast e (RCR A Subtitl e D ) landfill

. • Placin g a compacte d permeabl e soi l cove r (Non-RCR A Cap ) ove r expose d nativ e soil s i n 

### th e undevelope d residentia l are a (Parce l WESE)

. Th e ca p woul d be accomplishe d usin g a portio n o f existin g clea n fil l fro m th e L G an d L R parcels

. Thi s remedia l actio n woul d be couple d wit h erosio n control s (gradin g an d revegetation

, an d groun d wate r monitoring)

. T h e fina l compacte d surfac e wil l be covere d wit h topsoi l an d revegetate d wit h nativ e plant s t o minimiz e erosio n b y win d and surfac e water

. • Implementin

g deed restriction s o r othe r institutiona l control s o n th e remainin g parcel s o f the operabl e uni t t o prohibi t residentia l land us e unless additiona l remediatio n t o residentia l soi l clea n u p level s occurs

. DESCRIPTIO N O F TH E SIGNIFICAN T DIFFERENCE S AN D TH E BASI S FO R THOS E DIFFERENCE S T h e firs t chang e i s th e eliminatio n o f th e requirement t o plac e a 2-foot-thic k permeabl e soi l cover

ove r contaminate d soi l o n Parce l WESE

. Instea d o f coverin g contaminate d soi l o n th e WES E Parcel

, contaminate d soi l wil l be excavate d an d relocate d t o Midval e Sla g Operabl e Uni t 2

. Th e 

### second chang e i s t o eliminat e th e requirement t o no t breac h th e monolaye r soi l cove r on Parcel WESE

. Th e RO D required

, as a measur e t o preven t futur e developmen t activitie s fro m breachin g the soi l cover , tha t dee d restriction s or othe r institutiona l control s b e implemente d on th e WES E parcel

. Thi s contro l i s n o longe r necessar y du e t o th e remed y chang e o n tha t parcel

. The changes reflecte d i n thi s ES D ar e based o n ne w informatio n that the UDE Q an d the EP A receive d subsequen t t o th e issuanc e o f th e ROD

. Th e UDE Q determine d tha t th e informatio n support s th e nee d t o correc t and/o r clarif y certai n aspect s o f th e remed y describe d i n th e ROD

. Thes e change s d o no t fundamentall y alte r th e overal l approac h o f th e sitewid e remedy

. Modificatio n o f tw o foo t permeabl e soil s cove r o n Parcel WESE : Th e RO D require s a 2-foot

thic k monolaye r soil s cove r o n Parce l WESE

. A vegetatio n pla n woul d the n be implemente d wit h drough t toleran t plan t specie s consisten t wit h th e loca l ecosystem

. Continue d sit e investigation s concurrent wit h th e remedia l desig n hav e indicate d that

, contaminate d soil s ar e generall y withi n th e uppermos t 6 inche s fo r th e majorit y o f th e site

. Du e t o th e proximit y o f th e Midval e Sla g OU 2 Site

, i t i s mor e economical t o excavat e an d relocat e th e contaminate d soils

. Thi s modificatio n t o th e RO D offer s two advantages ; one , i t i s mor e economical ; an d two i t provide s fo r clean

, developabl e property

. Initia l cos t comparison s indicat e tha t possibl y 3 0 t o 4 0 percen t reductio n i n tota l remediatio n cos t fo r th e WES E parce l ma y be realized

. Thi s saving s

ca n b e mostl y attribute d t o th e fac t tha t lowe r cost s ar e incurre d i n excavating

, loading

, hauling

, an d unloadin g 6 inche s o f materia l than woul d b e i f 1 8 inche s o f fil l materia l wer e excavated

, loaded

, hauled

, an d unloade d wit h simila r hau l distances

. Thi s chang e i s i n complianc e wit h al l Applicabl e o r Relevan t an d Appropriat e Requirements

.Eliminatio n

o f control s implemente d fo r th e protectio n o f th e permeabl e soi l cover : Du e t o th e remed y chang e an d eliminatio n o f th e permeabl e soi l cover , th e nee d t o protec t th e cove r i s n o longe r needed

. Thi s leaves th e WES E parce l mor e developabl e b y no t restrictin g futur e excavation

. 

### SUPPOR T AGENC Y COMMENT S
T h e EP A concur s wit h th e remed y changes presente d i n thi s ESD

. AFFIRMATIO N O F TH E STATUTOR Y DETERMINATION

S Considerin g the ne w informatio n tha t ha s bee n develope d and the changes tha t hav e bee n mad e t o th e selecte d remedy

, UDE Q an d EP A believ e th e remedy : remain s protectiv e o f huma n healt h

an d th e environment ; complie s wit h applicabl e o r relevan t federa l an d stat e requirement s appropriat e t o this remedia l actio n at the tim e the origina l RO D wa s signed ; i s cos t effective ; and utilize s permanen t solution s t o th e maximum exten t practicabl e fo r thi s site

. PUBLI C PARTICIPATIO N

ACTIVITIE S Notic e i s hereb y mad e that thi s ES D an d it s supportin g documentatio n i s availabl e fo r revie w through th e administrativ e recor d fil e locate d a t th e abov e liste d locations

.