126149 2 -R 8 SDM S UNITE D STATE S ENVIRONMENTA L PROTECTIO N AGENC Y REGIO N 8 159 5 Wynkoo p Street Mailcode : EPR-S A DENVER , C O 80202-112 9 Phon e (800) 227-891 7 http://www.epa.gov/region0 8
Ref : 8EPR-S RMa y 16 , 201 3 MEMORANDU M SUBJECT : Mino r

Modificatio n o f

th e Selecte d Remed

y Californi aGulc h Superfun d Sit e American Smeltin g an

d Refinin g Compan

y (ASARCO ) Smelters/Slag/Mil l Site s Operable Uni t

5 Lak e County , CqTotjad

o FROM : Lind aKiefe r

Projec t Manage r TO : Californi aGulc h Superfun d Sit e Fil e PURPOS E Th e purpos e o f

thi s memorandu

mi s t o documen

t th e Environmenta

l Protectio n Agency' s (EPA's ) justificatio n fo r

aminor modificatio n o f

th e remedie s selecte

d fo r Operable Uni t

5 , th e Californi a Gulc h Superfun d Sit

e (th e Site)
. EP A issue d tw o ROD s fo r OU5 : th e RO D fo r

th e AV/CZ L site s o n OU 5 was issued o n Septembe r 29 , 2000 , an

d th e RO D fo r

th e EGW A site s on OU 5 wa s issue d o n Octobe

r 31 , 2000
. Thi s modificatio n applie s t o bot h RODs
. Th e modificatio n describe d herein i s considere d minor because i t

ha s non-significant

o r mino r impact o n th e overal l scope , performance , o r cost o f th e selecte d remedy
. 

### BACKGROUND Bot h th e Septembe

r 29 , 2000 an

d th e Octobe r 31 , 2000 RO D discus s th e use o f a n overla y distric t whic h woul dprovide ascreening proces s t o identif y propertie s wher

e specia l precaution s o r requirements ma

y b e needed
. The overla

y distric t was ratifie dby th

e Lak e Count y Commissione

r i n Novembe

r 200 4 an d the n repealed i n Apri l 2005
. Th e contaminants o f

concer n (COCs ) ar

e arsenic , cadmium , copper , lead , an d zinc
. MODIFICATIO N O F TH E SELECTE D REMED Y EP A an d CDPH E hav

e determined tha

t institutiona

l control s ar

e neede d fo r wast e lef t i n plac e t o assur e tha t contaminated soil s abov

e th e actio n level s fo r

tw o o f th e contaminants o f

concer n(COCs) , lea d an d arsenic , fo r

residentia

l o r commercia

l propertie s whic h eve

r i s th e case , an d fine sla g ar e removed o

r covered befor

e residentia

l o r commercia

l use s ar e mad e o f th e property , . t o ensur e prope r maintenance o f

an y cove r an d t o protect huma n healt h an d th e environment
. Th e objective s o f

th e institutiona

l control s ar

e a s follows : 1
. Reduc e o

r contro l huma

n exposur e t o contaminants o f

concern , an d 2
. Maintai n th

e integrit y o f an dpreven t disturbance s o f

th e engineere

d feature s o

r structure s o f

th e curren t o r futur e remedies
. Lake Count

y passe d a n ordinance , whic h wa

s recorded by th

e Count y Cler k o n Apri l 15 , 2013 , establishin g institutiona

l control s fo r

OU5
. Unde

r thi s ordinance , fo r

area s wher e i n OU 5 wit

h engineere d remedies , th

e Count y wil l no t issue apermit

fo r an y activit y on propert

y tha t contain s adesignated engineered remed y unles s th

e permi t applican t ha s secure d approva l fo r thos e activitie s fro mth

e CDPHE
. Fo r

al l othe r portion s o f

OU 5 no t designated a

s par t o f a n engineere

d remedy , th

e ordinanc e provide s tha

t an y excavation o

r othe r eart h remova l activit y tha t exceeds 1 0 cubi c yard s require s CDPH E approva l fo r suc h activit y a s aconditio n preceden

t t o th e Count y granting apermit
. Finally , th e ordinanc e provide s tha

t al l permit

applicant s shal l b

e provide d wit h irrforrriatio n regarding bes t managemen

t practice s regarding potentially contaminated soil s an d th e applican

t must certif y the y hav e receive d an

d reviewe d thi s informatio n befor e apermit wil l b e issued
. BASI S FO RTH E DETERMINATIO N THA T MODIFICATIO N I S MINO R Thi s modificatio n i s considere d t o b e non-significant

o r mino r base d o n th e following :

• Scope : Thi s modificatio n doe s no t chang e th e containmen

t technology , th

e physical area o f th e response , remediatio n goal s t o b e achieved , an

d th e typ e an d volum e o f waste s t o b e addressed
.

• Performance : Thi s modificatio n does no t chang e th e performanc e o f

th e existin g remedy
.

• Cost : Th

e costs o f establishin g an

d implementin g th

e ordinanc e versu s th

e overla y distric t ar e expected t

o b e similar
. cc : Crai g Gander , CDPH E

2