United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
EPA.RODR05-85 024
September 1985
Superfund
Record of Decision:
LeHillier/Mankato, MN
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA/ROD/R05-85/024
I. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
SUPERFUND RECORD OF DECISION
LeHillier/Mankato, MN
5. REPORT DATE
September 27, 1985
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
13. TYPE OF REPORT AND PERIOD COVERED
Final ROD Report
14. SPONSORING AGENCY CODE
800/00
16. SUPPLEMENTARY NOTES
16. ABSTRACT
The LeHillier/Mankato site is located in south-central Minnesota approximately
80 miles southwest of Minneapolis-St. Paul, adjacent to the City of Mankato. The
LeHillier area contained numerous natural and manmade depressions resulting from
changes in the channels of the Minnesota and Blue Earth Rivers, and from excavation of
sand and gravel. Between 1925 and 1960, these depressions were filled with miscel-
laneous rubbish. No records of the dumping activities or types of waste materials were
kept. In the fall of 1981, the Minnesota Pollution Control Agency (MPCA) received
information alleging that 'hazardous wastes had been disposed of at several dumps or
fill areas in LeHillier. A followup investigation confirmed the existence of these
disposal areas and contamination of the shallow sand and gravel aquifer with volatile
halogenated hydrocarbons, primarily trichloroethylene (TCE).
The selected remedial action includes: extraction, with partial treatment by air
stripping, of the contaminated ground water plume through adaptation of eight existing
U.S. Army Corps of Engineers (COE) ground water and flood control wells and constru-
tion of two new extraction wells; extension of the LeHillier community water system to
affected residents and businesses not currently serviced; and proper abandonment, in
accordance with State well codes, of individual wells formerly used as drinking water
supplies. This action will manage contaminant migration until contaminant levels
(see separate sheet)
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Croup
Record of Decision
LeHillier/Mankato, MN
Contaminated Media: gw, soil
Key contaminants: trichloroethylene
(TCE)
IB. DISTRIBUTION STATEMENT
19. SECURITY CLASS (This Report/
None
21. NO. OF PAGES
26
20. SECURITY CLASS (Tliispage/
None
22. PRICE
BPA Form 2220-1 (R«v. 4-77) PREVIOUS EDITION is OBSOLETE
-------
INSTRUCTIONS
1.
REPORT NUMBER
Insert Ihe lPA report number as it appears on Ihe cover of Ihe publkation.
LEAVE BLANK
2.
3.
RECIPIENTS ACCESSION NUMBER
Reserved for use by ~a.:h r~port redpient.
...
TITLE AND SUBTITLE
Title should indicate dearly an.d brieny th~ subj~~.t .:overa~e lJ.f the r~'port. and be disl'lay~'d prolllin~'ntly. S~'r suhlirk. if u~~..I. III ~maher
type or otherwise subordinate 1110 main title. When a report IS prepar~d In mon° than nne vulumc. rq"'al Ih~' prnuary till~'. 01.1" V"hllll~'
number and include sublitle for Ihe specific litle.
REPORT DATE
Each report shaU carry a date indicalinl at least monlh and year. Indkate th~' hasis IJII whidl it was ~'Ie.:t,'d (1'.1:.. .JQ/(' "lis.wc'. JQlc' "I
tlPP'OlItJl, dilr, 01 ""'ptlTtlrion, tic.).
6.
8.
PERFORMING ORGANIZATION CODE
Leave blank.
7.
AUTHOR IS)
Give namels) in ,'onvenlional order (Jolin R. Doc, J. Robe'" /)0('. ('11'.). List authur's afliliallull if il .liff~'rs frum Ih,' I"'rfmminl,! "'I,!ani.
zation.
8.
PERFORMING ORGANIZATION REPORT NUMBER
Insert if performinl orpnization wishes to assign this number.
9.
PERFORMING ORGANIZATION NAME AND ADDRESS
Give name, sUeet, city, stale. and ZIP code. Lisl no more than two levels of an urJ,!anilaliulial hircardlY.
10. PROGRAM ELEMENT NUMBER
Use the propam elemenl number under which Ihe report was prepared. Subordiniltc numbers ilia)' be indu.k" III 1'01 r.'"1 h.. '"s.
11. CONTRACT/GRANT NUM8ER
Insert conUact or pant number under which report was prepared.
12. SPONSORING AGENCV NAME AND ADDRESS
Include ZIP code.
13. TYPE OF REPORT AND PERIOD COVERED
Indica Ie inlerim fina!, etr., and if applicable, dates covered.
14. SPONSORING AGkNCV CODE
Insert appropriate code.
15. SUPPLEMENTARV NOTES
Enter information not included elsewhere bUI useful, such as:
To be published in, Supersedes, Supplements, etc.
18. ABSTRACT
Include a brief (200 words or 1,55) factual summary of the most sil!nilkant infurmation ~'untain,'" III II,,' '''I,ml. II Ih,' 1\""'11 ......t.1I1IS a
sianificant bibliopaphy or lilerature survey, meniion it here.
Prepared ill ~'oopc:ratiun wllh. hall\lallOIi 0'" l'r':"'"I~''' Oil "0""""",,' ..I'.
17. KEV WORDS AND DOCUMENT ANAL VSIS
(a) DESCRIPTORS. Select from the Thesaurus of t-:ngin\.'Crinlf. and Sdcntili.: Terms the prupc:' aUlhort,...d I,'IIIIS Ihalld...nllfy lh,' majm
concept of Ihe research and are sufficiently specific and preci5C to be u5CcI as mcl...x entrIes fur \.alilluj:lnl,!.
(b) IDENTIFIERS AND OPEN.ENDED TERMS. Use identifiers for project nan1\S, cude namcs, ellulpmcnt d~"I&:nalurs, ct\:, lJ~ "I'CII'
ended terms written in descriptor form for those subjects for which no desc:riplur exists.
(c) COSATI rn:LD GROUP. Held and group assilnments .Ire to be taken from the 1965 ('OS" 11 SUhjl'\.I C'al"j:ury Ust, Sinc,' the ma-
jority of documents are multidisciplinary in nature, the Primary Held/Group assignmenllsl will bc '1\\:.11 i~' disuphnc. area III' human
endeavor, or type of physical object. The applicationls) will be cruss.rderenced with scl'undary I il'ld/C ilUlIl' assll!f1l11l'uts Ihal ",'ill 1'11110'"
the primary postinlls),
18. DISTRIBUTION STATEMENT
Denote releasability to the public or limitation for reasons ulher than sc\.urity fur cnmple "I{d...a'c 1;..1111111"<1:' (il~' any a~.lil..lllhlr ,..
the public, with address and pri\:e.
19..20. SECURITY CLASSIFICATION
DO NOT submit classified reports to the National Te\.hnicallnformatiun servil-e,
21. NUMBER OF PAGES
Insert the total number of pales, including this one and unnumbered pages, but exdude di\tribulion lisl, il any.
22. PRICE
Insert the price s~t by the National fechnicallnformation Scrvi\.e or the Government Pnnting OITke, il' knuwn.
EPA Forni 2220-1 (Rn. .-77) (R....,..)
-------
SUPERFUND RECORD OF DECISION
LeHillier/Mankato, MN
Abstract - continued
reach drinking water quality. Total capital cost for the selected remedial action
is estimated to be $800,000 with first year operation and maintenance costs of
$70,000. The State of Minnesota will continue O&M for the remaining duration which
should not exceed 9 years.
-------
Record of Decision
Remedial Alternative Selection
Site:
LeHillier/Mankato, Mankato, Minnesota
DOCUMENTS -REVIEWED
I have reviewed the following documents describing the analysis of cost-effect-
iveness of remedial alternatives for the LeHillier/Mankato site:
- LeHillier Remedial Investigation;
- LeHil1ier Feasibility Study; and
- Summary of Remedial Alternative Selection.
DESCRIPTION OF SELECTED ALTERNATIVE
- A system of ten extraction wells with partial treatment by air stripping
which aggressively pumps and treats contaminated groundwater over a ten
year period or until acceptable levels in groundwater are reached. This
system is necessary to effectively control migration of contaminants
and protect current and future drinking water supplies for the City of
Mankato (Pop. 29,000).
- Extension of the LeHillier community water system to affected
, residents and businesses not currently serviced.
- Proper abandonment in accordance with State well codes of
individual wells formerly used as drinking water supplies.
- The selected alternative has total capital cost of $800,000
and first year operation and maintenance cost of $70,000.
Tne total 10 year present worth is Sl.3 ,million.
DECLARATIONS
Consistent with the Comprehensive Environmental Response, Compensation, and
Liability Act, 42 U.~.C. 9 9601 (CERCLA) and the National Contingency Plan,
40 CF~ Part 300 (NCP), 1 have determined that the selected remedy is cost-
effective and provides adequate protection of public health, welfare, and the
environment. The State of Minnesota has been consulted and agrees with the
-approved remedy. In addition, the action will require future operation and
-------
- 2 -
maintenance activities to ensure the continued effectiveness of the remedy.
These activities will be considered part of the approved remedy and eligible
for Trust Fund monies for a period of one year. In accordance with section
104(c)(3) ~f CERCLA, the State is required to ensure the continued operation
. and maintenance of the selected remedy after the first year.
This action will manage contaminant migration and will control and aggressively
reduce continuing sources, if any, until contaminant levels reach drinking
water quality. By periodically monitoring groundwater quality, operational
data will be used by United States Environmental Protection Agency (U.S. EPA)
and the State ~f Minnesota to evaluate performance and assess the likelihood
of reaching our goal of 10-6 lifetime cancer risks for trichloroethylene (TCE)
(2.8 ppb). We estimate that our goal can be achieved within a five to ten year
period, if any continuing sources are eliminated under this remedial action.
If this is not the case, source control actions will be evaluated versus
operation of the recommended alternative for a longer period. In addition,
the selected remedy is more cost-effective than other remedial action and is
necessary to protect public health, welfare, or' the environment.
M~~ (~)
Valdas v. Adamkus ~ ~
Regional Administrator
Region V
-------
Record of Decision
Remedial Alternative Selection
'LeHillier/Mankato, Mankato. Minnesota
SITE LOCATION
The LeHillier/Mankato site is in south-central Minnesota approximately 80 miles'
southwest of Minneapolis-St. Paul, adjacent to the City of Mankato. The study
area, is shown in Figure 1. The southern half includes the residential and
industrial area of unincorporated LeHillier and the northern half is a portion
of tne City of Mankato ~nown as West Sibley Park. The site is crossed by U.S.
Highway 169 and the Chicago and Northwestern 'Railroad. A Ranney collector
(water supply well), located at the northeastern edge of West Sibley Park near
the confluence of the Minnesota and Blue Earth Rivers, supplies 95 percent of
the City of Mankato's daily water requirements.
SITE HISTORY
The LeHillier area contained numerous natural and manmade depressions resulting
from changes in the channels of the Minnesota and Blue Earth Rivers and from
excavation of sand and gravel. Between 1925 and 1960, these depressions were
filled with miscellaneous rubbish. No records of the dumping activities or
types of waste materials placed in these depressions were kept.
In the fall of 1981. the Minnesota Pollution Control Agency (MPCA) received
information which alleged the disposal of hazardous wastes at several dumps or
fill areas in LeHillier. A followup investigation confirmed the,existence of
disposal areas and contamination of the shallow sand and gravel aquifer with
volatile halogenated hydrocarbons, primarily trichloroethylene (TCE).
In October 1981, MPCA began monitoring water quality in private wells located
in the area. Analytical results identified the presence of an elongated TCE
plume which generally ~aralleled the Blue Earth River along the eastern half of
LeHillier. '
A bottled water program was instituted by United States Environmental Protection
Agency (U.S. EPA) and was continued by MPCA for residents of LeHillier whose
well water contained TCE in concentrations greater than 25 ug/l. A Housing and
Urban Development (HUD) grant for construction of an alternative groundwater
supply well was sought and obtained by Blue Earth County on behalf of the
LeHillier community. A deep well was drilled in May and June 1984. The distri-
bution system was completed by the end of 1984. On January 7,1985, a court
order was issued which has been interpreted to make operation of the HUD deep
well water supply system contingent upon the installation of a sanitary sewer
system. LeHillier is now planning to construct a sewer system within a 5 year
period by seeking grants and selling $400,000 of municipal bonds. The City of
Mankato has approved operation of the HUD system. Most LeHillier residents are
now supplied with a penmanent clean water supply.
-------
,..--
. .-
.
. ..".,. .,
So&- : -------~...._~-~.~
. : ;- ",i-4;:~~.~~.~";;'::-t-
'.:\,,:----=:::.---.;...'. --==
. .:.:.u. -...:.;J... :-.~ - :.
,--::,.." .-.. .. ~--
.' =--~~----~
...fJ.:t '. I r . ..
,;r-:
,
,.
,I
~
-
0""
.' \
..,
......- ,. .t'.
.. '." _u."-i~. ':~4;-?:'('F~{: ' u' ,.
. -.."..... ~ ' ----.....' --
........ .~,:'.'~~' '.";'.. '1' --;:-~~ .: 0':::'" ~':,,-:""~ :,"""'';''''''''''0'
/_~7".;-a~'-'U"...- '8;~'~' ~7:'/ i' ; ; 1 . ~~i-':- ;..::~~ ,:' ....:'....."':1.'"
,"-:f~' ,,' ' ~EHILLIEi;:". ,,"'~ ,~~~ ~ :-", -.... ......: ~., -:<=-
/ --'", \ I _r" J I --:::- I ~ .;;...-...~~;./.- : -- -.~-.'
,/ ." ,/ -. , ! :----=:=-:-...; - ',,"...".' c.:/./ : :---~ . -.'<
:.-.,-- ,. /'OC -- ,.--~. ,-o-I:/r.;:::;a?--~'{( (----- :-;:.':"...." ,..'
, ."a', / ~ R/ -' '''-:-I~' .:" ,-..;. /1 ' :'0 ":.'
, ., ~ VER I~ ~'.>;' ,':'\ ~ II ':'," . ",', I :' ,,,.r=--
~:. . ,...' I .- ~;.~ l(1 -~ ',~ ''::;' " " I.. ",:-" I ,'.' ,
'~_.-' ....... '/ .\~~ ,,- ,~~~.,,',, '\ ' .", "
~,. ,. --- , ~'.'" ~ ,I" :~..:..':~ "''''41..1\'''\ ',' i: . ...,......, ,-{, . ::. ,::-
~~ " ' ~I ,,,:-: K ,:. ":' C ?'/--~- '-; ,....\, , , .' >\ --- ~ ..,..., :>:f"'" -
~~ \ '\ - ': t '.'~."~} ~:: \', ~; l ....'~., -----.....~~ .,', 4. ~_... ,,: . ~~: -..;
.--f:;. ," 2':: ;~----...;.... .8."', ;'~:'~,: -.:."'.i', . "~'J -~....,-
-.\' ....... "" -..r""'.-..._' ,"" ,,;,'~! ". ' .-~- ./
" , I '" .-/"'::'i'- -- , '" "" ,---I, i .~oo ?~-- -"
, ~~, \ """"",....~a-. : ,""" :'.:, ~',:' -Ii. ( /"'-!.'~ .~. ,: ,--, - ,.
o - -......... .J')" ' I I /~~~/ ," S:.-"t,;.ae; \\ ,\,,,,,- -- ~ - -l - ;:....,'.
'-----.I '" - . ~.-- " " .. ' " /' ': ' , '-. I " ,- ," ': I '/
, ~ "" " «. . '\~ - '" ,-- : . r\,,;/~ ' I. J', \ 'I' ---- ------=- ' : '
,- ,\\.--..'~?,:.... \ '}~\ ............ .. ~I . f r II .' :~~ .
'.~&.-C//"'il ~\' "..,.IP~~"'h:? ~ -,.:,' i II //:'//.:::--,.,,~.,"C'.' ~'-'--
~ ,~:i....~I\, \\\1~> :~....,~.---,~/ i.!'" -: ...............~,,..-,-_.,,............
".\ -;;;I/;~' , . ,--=-.:.'...:",:.-:;~'.--=--> '/>.;~ /./1 -/.---,,- /,7-";',r. . -:-
;~;) ~\~\ '.. IH((('",,,,,"-:.:;J-;..,'~J' ~,~/,~;/ (i~~--/ ;,".._:~:I ,
, , . ,-",' "" '" /~', ,. \ ';.: , '.;:' ~ ',;"'r-,.;.I.-' " .>,
-.
"
I~\
\.V
o
~II"\,",""
...~...
~.-~"",.~."
200C
SCAL: IN FiE":'
S:::UR::: I.:SGS :o\ln""o VIles': C"'='I:"I~'t ',~.~.
...- ..
=,-
L.E 104 I L.LIER
BLUE !~~T'"
COUNTY
FIGURE
LOCA i'IOf\i ,......:
LE"'IL~I:=, s;-:
-------
- 2 -
During the fall of 1982 and the spring of 1983. u.s. EPA conducted a preliminary
field investigation (FIT study) of the site. Monitoring wells were installed
and groundwater levels were measured. The general boundaries of the northern
half of the contaminant plume were identified based on analytical data for
monitoring well samples collected. As of May 1983, the northern edge of the
10 ug/l contour or the contaminant plume was estimated to be approximately
1/4-mile south of the City of Mankato water supply.
Based on the application of the FIT study, the site was scored (59.75) and
included by the U.S. EPA on the National Priorities List of uncontrolled
hazardous waste sites.
REMEDIAL INVESTIGATION
Although considerable investigation had been done on the area prior to 1984,
the existing data base for the LeHillier site was considered insufficient
to allow for the selection, screening, and evaluation of remedial action
alternatives for onsite or offsite control. To develop the additional data
needed, a Remedial Investigation (RI) was implemented (Final Work Plan,
May 1984 and the Addendum to the Work Plan, 'January 1985) and completed.
The primary objectives of the RI were to dete~ine the nature and extent of
contamination, acquire site-specific data required to support an exposure
assessment under the no action alternative and to support the Feasibility
Study (FS).
RI FIELD ACTIVITIES
RI field activities included a number of major tasks:
o
Installation of monitoring wells, surface water staff gauging
stations, and continuous water level recorders;
o Collection of water level data and testing of hydrogeologic
properties; ,
o Three rounds of groundwater sampling and analysis at private
production wells and monitoring wells;
o Drilling of boreholes for sampling analysis of groundwater
quality at different depths within the aquifer; and,
o Analysis of samples collected at two suspected source areas.
All field activities with the exception of water level monitoring
were performed between August 1984 and April 1985.
NATURE AND EXTENT OF CONTAMINATION
The nature and extent of contamination is shown in Figure 2. The area
contained within the 10 ug/l TCE isoconcentration line is approximately
50-acres.
-------
/
..' /
,..... /'-
"/
~NI &/
/", ~
-,' \'.
~ \\
'J
. . .
.--,.
~~~.
. .
;~
"-
"
"',
.~
"
-,-:"-
t'
/
iy
t
~~~.
---
~. "'ot .
Io.........((.'c,. .
. I
I
. )8 ....O&.
,
I
)
/
~
~...O..
\
,
. '.
U.I "
,
/
/
I
,
, .a S.-..:t"
.
tee ..
..,..
." S.&8IIG1.,
"."'0".0 .
--
'.
2
,,( .
, . 5.....04
.
IU
.
I
(
- -
- .
:
.
I, '
.\ C.
-""".. "
I..
,~ .......
: r
: .
-;::-.'...-
. ''::''
;..
.'~L 10 .-0 T:' C'ONC''''''..',O-'
M'-SU.UO'N I'. ..0...'0.'''<; -1.1..10
... "GlL.
27,.
"''''''''0 ...c Tel:~"Cf.'..':O.
M'AauaIO .. ..... .".. Mo.'YO.."'':
'IIr.8a.. ... VCiI&.
£'1
-...'" to &110 TCI co-.C""'..'" "0"
..'......,-.D'" "1110'.""''' ....'"
.....,GlI.
&,.,
10 ."0 ~OCA.'OOo 0" ".~~
000'
..,... ov....,,.. loalllllO...t 10
.-0 ,el CO-C'''''.,,'IO-
. .1
FICUR!
ANALYTICAL TCE CONCENTRATIONS
IN SuRFACE AQUIFER S.\M'LltlC
RQUNO 3. A'RIL "'0. '115
",."'~"I'. '1
-------
- 3 -
TCE concentrations shown in Figure 3 are typical of the maximum magnitude of
groundwater TCE contaminantion.
The analytical results for groundwater samples collected from different depths
. within boreholes scattered around the contaminated area indicate that ground-
water TCE concentrations are highest at the base of the sand and gravel aquifer
near the b~drock (St. Lawrence Dolomitic Siltstone) - overburden contact. A
possible explanation for this trend is that periodic recharge causes vertical
gradients capable of inducing downward contaminant transport. Once the TCE
plume reaches the basal unit of the aquifer, its further downward migration is
limited by the lower hydraulic conductivity of the bedrock aquiclude when
compared to that of the aquifer. At the ,base of the aquifer, the predominant
flow direction is horizontal. .
Although TCE concentrations in the upper weathered zone of the St. Lawrence
Siltstone underlying the sand and gravel may be elevated, .TCE concentrations
in the unweathered portion of this formation are expected to be below the
analytical method detection limits. TCE concentrations in water samples
taken from the deeper bedrock monitoring wells were consistently lower than
those in samples from the ~djacent shallower bedrock monitoring wells.
A few private bedrock wells in the area are contaminated with TCE (e.g., the
concentration of TCE in water taken from a residential well during Round 3 was
130 ug/l TCE). Downward vertical gradients in the bedrock, pumping-induced
vertical gradients, the possible poor seating of the casing into the bedrock
provide tne driving forces and the pathway for downward migration of TCE into
the bedrock. A probable pathway for cross contamination between the upper
contaminated sand and gravel aquifer and the lower Franconia Sandstone aquifer
exists. '
The boundaries of the TCE plume have not changed dramatically during the 11
months of RI monitoring in 1984-85. The predicted order-of-magnitude estimates
. of future TCE concentrations at the Ranney collector (TCE maximum concentration
~ 0.8 ug/l estimated ,to. occur in 50 years) were developed for the exposure
assessment under the no action alternative.
SOIL CONTAMINATION
In addition to the TCE 'identified in ground~ater, petroleum byproduct constituents
(ethylbenzene at 18,000 ug/kg, toluene at 2,400 ug/kg, and xylenes at 81,000 ug/kg)
were identified ;n subsurface so;ls located in a small area at the end of
Eleanor Road and adjacent to the Army Corps of Engineers dike as shown in
Figure 4. This vicinity was identified as the location of a former disposal
area. These compounds were identified in individual wells and are not believed
to be d;stri~uted throughout the aquifer or as a plume.
SOURCES
Efforts to locate source(s) of the TCE contamination were unsuccessful. The
TCE concentrations in the soil and septic system samples were low or below
analytical method detection limit. Four subareas showing higher TCE concen-
trations than those observed in the surrounding area highs were identified
and may be possible source regions.
-------
. --..
~~----...- ...
......f.
:':)1 \ I ': 'C. .
)
,/ /
, ./
/
.... j'
,;0/
.'J
....., ...,'
..-. \
.-"'/\ .
'.
'ues
.
'15e 5
.
..se.
.
'''''''' :
. . , ... ..-
. "/
/.
"'i-
-.('
....
'31
.
- .."
"ses
.
~..,:
J
."47
.
'OS
- - -
--
_." .. .-' ".- ---
,.
.
-=-
'- -=.:::::
.""
"'
- .;
i'
-\ '.
'. .
.
"-
"
"
'"
. "-
.~~' '.
~ .
~---=-;.;.
,"
-:--.
r
;.,
.1,'
---....".
'"
~"'....
.,
'00'
... .~ 1
.I
/
.,
\
\
\
"-
\
".
".
'"
I
1
\
... .
....~'
-
.I"L 10 ..0 ~. COi'CI"'.&T10"
MI.AIU..O'. ..,.. .,. .QIrII.~OI'I"'''
_,~,,"I uGl\o.
<:112
.''''II"IO...O..-el CO-C''''..''''O''
.....""-10'. ....01""." "'''Ia
,,, wGit.
...."
10 -0 ~OCA~IO" O' "..~..
--.-
- --- -'
"GU"E 3
ANAL. YTICAL TeE cONeENTIU. TIOII::; IN
OVE"'UADIN SANI'L.INC "OUNC :
O:T.,"I". """-
-------
. .
I'
.,
II
"
/. ,/:j' 1
. . . - ~ ~:. .- = - . . - . - - - - - .
-, - -.;:' - - - I "I i
":'- - - , . '." /
- -=.-::!. - -;""'"..-'. ,. -""". -- /1 " \ I. Il' , ;
~'''., ': "";~",,-f .. / \ \1 I !
~~~""::::\. f ~~.f : II I, /
. '<.~;:.. .'/~..../! .. I I I' !
".~ .. ~~'- j.!;~-A :.i .;1 (.
',~.,~:.:~,~.....~. "~._.... ~~.j~j? =--
'" :;"':"""~, ~ ~
,'" : '://I'~, ",) \ / 1/ !
- if ~'i I I, I
'l .j 1/ 'I /
'"'' "; : I !, /
... ~ /i! I ' I
" ,,~ ,( / ! I I
/l ~~ / /, I \ .
'~// / ;1 /
,. """" I / I I I
.; ;/; 1 /
"/~.': / / 1/
" '",. . ". .................. .' I /
- ~ "."" O' ' ',' ~ / / '.
eONuM""~,o ~_/ 1 /,.
SCO'''.''e, 'O,", --- / I
--- .,/ I
'" - - - .... - " /
" -- ----- I)
.~~---- /,
I
I
\
\
\
/
.~
!
!
I
. J
~:::::o ~I/'
co~~ec~oFl. /
~..I \
~ i \
"
Ii
II
.,
'. .
. "'.
. .~
!'
'r'
Itt
;j
FIGUR E 4
LOCA TiON OF
-------
- 4 -
Because we did not identify the source(s), source strength and probable
future loadings could not be specifically quantified. Hence, the actual
exposure risk estimates associated with no remedial actions cannot be quanti-
fied. The exposure assessment was based on an assumed TCE influx. The accuracy
of this assumption can only be assessed by continued monitoring of site water
quality over time.
EXPOSURE ASSESSMENT SUMMARY
An exposure assessment was conducted in the RI. It evaluted the potential
health effects that may result if no actions are taken to remove TCE and
other volatile organic compounds (VOCs) from the groundwater or to limit the
potential contaminant exposure to people in the LeHi11ier area. E~posure
risk estimates reflect potential lifetime average TCE ingestion and dermal
absorption rates. Risk estimates were generated for three types of water
use:
o Use of water from Mankato's Ranney collector;
o Use of water from a LeHil1ier private well in the
area of the plume; and,
o Use of water from the LeHi1lier HUe community well.
The resulting estimated overall increased excess lifetime cancer risk associated
with use of the Mankato Ranney collector water for ingestion and bathing was
approximately 1 X 10-6 (an increased one cancer per 1,000,000 people exposed
to TCE). The estimated total increased excess lifetime cancer risk associated
with use of LeHillier private well water was 7 X 10-~ which is the total of
the incr~~sed cancer risk of six cancers per 10,000 people exposed to other
vacs. The estimated increased excess lifetime cancer risl< associated with
use of the LeHillier HUe community well water was expected to be zero.
ENFORCEMENT
Since no specific TCE sources have been defined and no disposal records exist,
no potential responsibl~ parties (PRP) were identified. The U.S. E?A and
MPCA did interview local. residents concerning past dumping and conducted a
survey of industries that may use chlorinated solvents. Consequer1tly, at
least six waste disposal sites have been identified in the LeHillier area but
there is no recollection of them specifically receiving industrial waste.
Small scale dumping of chlorinated solvents by some of the local industries
may have been major contributers but there is no direct evidence at this
time .
-------
..
- 5 -
ALTERNATIVES EVALUATION
The Mankato Ranney collector which supplies 95 percent of the drinking water,
is approximately 1,500 feet downgradient of the leading edge of the contaminated
groundwater plume. Most residents within the LeHillier area are serviced by
a new HUD water system which utilizes a confined deeper bedrock aquifer. A
steady state flow and contaminant transport model under an assumed source
influx predicts that TCE will reach Mankato.s water supply within 20 years.
Maximum TCE concentrations of .8 ppb will occur at 50 years. Under assumptions
made in the exposure assessment, dermal contact through bathing and ingestion
over a 70 year period would result in a 10-6 lifetime cancer risk. A sensitivity
analysis was also perfonned on the ,nodel where several parameters were varied
to determine which parameters have the greatest influence on predicted conce~-
trations in the Ranney collector. The sensitivity analysis showed that the
effect of a 100 percent increase in TCE influx is a 100 percent increase in
maximum concentrations in Mankato.s water supply. Since source strength and
possible future loadings were not quantified in our RI, the actual source
influx may be much greater than assumed in our exposur~ assessment, therefore,
the actual risks to Mankato.s water supply may be great~r than 10-0.
The model also assumes a steady state flow. The actual groundwater flow
direction and velocity is heavily dependent upon flow stages in the Blue
Earth and Minnesota Rivers and is very dyn~nic in nature. By observing
groundwater flow over a 31 month period, the actual net movement of the TCE
plwne is slowly northward towards the Ranney collector. Since the actual
flow is complex and transient (not simple and steady state), forrnation of a
TCE c~ntamind't slug through a sequence of extr~ne hydrogeological events is
a possibility and may r~sult in TCE concentrations that are higner than
predicted in our exposure assessment.
Migration of uncontrolled conta,ninants frorn an unidenti fied source Inay severely
impact the water supply for the 29,000 reside~ts of Mankato. Clea~-up altern-
atives ranying from constructing alternate ~ater supplies for Mankato to
contr~lling and clean,ing the aquifer were evaluated. During initial alter~~tivp.
development, our Fe"as1bilitj Study dOCUlne~ts that controlling and cl~ansing
the aquif~r is Inore ~ost-effective than constrycting an alternate water
supply for Mankato~
REMEDIAL GOALS AND OBJECTIVF.S
. These are the rernedfdl goals and objectives for the LeHillier site:
- Adequately protect the pUblic against exposure to TCE through
di rect contact or ingestion of groundwater froln pri vate and
public water supply.
- Adequately protect the public against exposure to TCE released
to S.Jrface water from the groundwater.
-------
0- 6 -
- Adequately protect and minimize damage to the environment
.from the migration of TCE in the groundwater.
Remedial goals are also expressed in terms of specific concentrations in
groundwater and surface water through remedial action. Remedial goals and
objectives are expressed in terms of TCE only to simplify discussion. Other
volatile organic contaminants identified in groundwater would be addressed by
remedial actions directed at the more widespread TCE contamination.
REMEDIAL ALTERNATIVES
Initial steps were to screen every remedial .technology conceivable. Only
applicable and feasible technologies were further evaluated again for specific
engineering, cost, environmental, and institutional criteria consistent with
the National Contingency Plan (NCP). The remaining technologies were then
combined to form five alternatives (AI-AS) which were screened for the criteria
described above. The following are brief descriptions of each alternative
consid'!red.
Alternative No.1 (A-1).
Groundwater Extraction. A-l involves extraction of the contaminated groundwater
plume through adaptation of eight existing U.S. Army Corps of Engineers (COE)
groundwater and flood control wells and construction of two new extraction
wells, one north and one south of the existing TCE plume. An arrangement of
eight existing COE wells pumping at 225 gpm each and two new wells pumping at
500 9pm appears to provide a sufficient overall zone of capture at a ~easonable
rate of extraction. Groundwater from the CaE wells would be conveyed to the
existing COE sump by means of the existing gravity collection line. ~dter from
the north well would be conveyed to discharge through a new outfall pipe.
Water from the south well would be conveyed to the existing CaE gravity collection
1 i ne .
The arrangement of eight selected COE extraction wells and two new extraction
wells in A-1 is intended to serve three purposes:
o Tne new north well would serve as a blocking well to control migration
of the plume toward the Ranney collector.
o The CaE wells would generally control westward migration of TCE.
o The new south well would extract TCE contamination near suspected, (but
undefined) TCE sources near the southern portion of the site. '
The goal of extraction under A-1 is to manage migration and rapidly reduce TCE
concentration in the groundwater to the Clean Water Act Ambient Water Quality
Criteria for ingestion of drinking water for the estirnated 10-6 excess lifetime
cancer risk concentration of 2.8 ug/l. Assuming no active TCE sources contributing
to the groundwater, the predicted duration of extraction would be approximately
5 to 10 years a,cording to the modeling of TCE migration. '
-------
- 7 -
It is possible that at least one active source of TCE is contributing to ground-
water contamination at LeHillier. If this is the case, the groundwater extract'
drrangement would control migration and reduce sources but may not achieve
the extracticn goal of reducing TCE concentration in the aquifer to 2.8 ug/l
within the time fra~e we have estimated. However, aggressive groundwater
extracti~n may help identify and lead to the remediation of TCE sources. If
a source of contamination is found, source control actions will be evaluated
versus continued pumping and treating.
Groundwater Treatment. A-1 incorporates no treat.nent of extracted groundwater.,
Groundwater Discharge. A-1 involves discharge of extracted groundwater in
the COE 1nterceptor into the Blue Earth River through a diffuser pipe placed
along the bottom of the river. Groundwater discharged from the north extraction
well would be discharged through an outfall located on the west bank of the
river. Modeling of groundwater suggests that the maximum TCE concentration
of the extracted groundwater from the COE interceptor would be approximately
13 ug/l. Following dilution in the Blue Earth River. the concentration of
TCE in the ~iver is expected to be less than the proposed maximum contaminant
level (MCl) for trichloroethylene of 5 ug/l and below the Clean Water Act
Water Quality Criteria for ingestion of drinking water and organisms for the
estimated 10-6 excess lifetime cancer risk concentration of 2.8 ug/l.
During the first 6 months to 12 months of extraction system operation. estimates
indicate that the extraction system may need to be shut down for brief periods
when flow in the river is insufficient to dilute discharged groundwater to
the target TCE concentration of 10-6 excess lifetime cancer risk of 2.8 ug/l.
To maintain a maximum TCE concentration of less than 2.8 ug/l. groundwater
discharge would be limited to times when river flow was greater than 19.7 cubic
feet per second, or 8.840 gallons per minute.
LeHi11ier Water Supply. A-I includes extension of the HUD distribution
system to include all leHillier residential dwellings and private comnercial
operations affected by the existing TCE plume.
. Mankato Water Supply. A-I does not involve physical changes to the existing
Mankato water supply,system. A-I includes monthly monitoring of the Ranney
collector discharge for VOCs according to the SUlnmary schedule in Table 1.
Alternative No.2 (A-2).
Groundwater Extraction. A-2 involves the same COE and new groundwater extraction
well arrangement and extraction pumping rate as A-I.
Tne goal of groundwater treatment is to reduce the mass of TCE discharge to the
Blue Earth River so that the Clean Water Act Ambient Water Quality Criteria for
ingestion of drinking water and lifetime cancer risk concentration of 2.8 ug/l
is met. Assuming no active TCE sources contributing to the groundwater. the
predicted duration of extraction would be the same as A-I. that is. approximately
5 to 10 years according to the modeling of TCE migration.
It is possible that at least one active source of TCE is contributing to ground
water contamination at LeHillier. If this is the case. the groundwater
extraction arrangement would control migration and reduce sources but may not
achieve the extraction goal of reducing TCE concentration in the aquifer to
-------
- 8 -
2.8 ug/l within the time frame we have estimated. This alternative will
a9gressively extract contaminants and may lead to identification and eventual
remediation of active TCE sources. If a source of contamination is found.
source con~rol actions will be evaluted versus continued pumping and treating.
Groundwater Treatment. A-2 incorporates treatment of extracted groundwater
from the new south extraction well to rernove 98 percent of the TCE by air
stripping prior to discharge into the COE interceptor. .
The goal of groundwater treat~ent is to reduce the mass of TCE discharge to the
Blue Earth River so that the Clean Water Act Ambient Water Quality Criteria for
ingestion of drinking water and lifetime cancer risk concentration of 2.8 ug/l
would be met at the consecutive seven day average low flow over a ten year
period (Q7.10) river flow.
Based on the predicted estimated maximum TCE concentration in groundwater
extracted from the wells which would receive treatment, 98 percent TCE removal
would produce a maximum discharge concentration from the COE interceptor system
of 3.4 ug/l.
Groundwater Dischar e. A-2 involves. discharge of extracted treated groundwater
to the B ue Earth River through two near-shore outfalls located along the west
bank of the river. With the TCE removed from the new south extraction well
discharge, the maximum concentration of TCE in the extracted groundwater is
estimated at 3.4 ug/l. During the low flow condition represented by the Q7,10
in the ~lue Earth River of 10,300 gpm. the maximum estimated concentration of
TCE in the river would be 1.7 ug/1, which is less than the Ambient Water Quality
Criteria for ingestion of drinking water and organis,ns for the estimated 10-6
excess lifetime cancer risk concentration of 2.8 ug/l.
LeHil1ier Water Sup~. A-2 includes extension of the HUD distribution system
to include all LeHi11ier residential dwellings and private commercial operations
affected by the existing TCE plume.
Mankato Water Su 1 . A-2 does not involve physical changes to the existing
ankato water supp y.system. A-2 includes monthly monitoring of the Ranney
collector discharge for VOCs according to the summary schedule in Table 1.
Alternative No.3 (A-3l.
Groundwater Extraction. A-3 incorporates extraction of contaminated groundwater
through one new well installed on the north edge of the existing TCE plume.
One well pumping at 1,000 gpm appears to provide a sufficient zone of capture to
control or block the northward migration of TCE. The final placement and
extraction rate of the blocking well(s) would be established during final
design of the remedial action. .
The 90a1 of the blocking well is to minimize the migration of TCE toward the
Mankato Ranney collector. It is not intended to rapidly reduce the TCE concen-
tration in the sand and gravel aquifer at LeHillier.
Assuming no active TCE sources contributing to the groundwater, the blocking
well extraction would e~entually reduce TCE concentrations as the TCE plume
-------
- 9 -
moved north and was withdrawn. Based on an ultimate goal of.a 10-6 excess
lifetime cancer risk concentration of 2.8 ug/lin the groundwater, the predictec
duration of extraction would be greater than 20 years according to modeling of
TCE migration.
It is pos~ible that at least one active source of TCE is contributing to ground-
water contamination. If this is the case, the blocking well system would be
expected to prevent TCE migration to the Mankato Ranney collector but not to
achieve any reduction in TCE concentration in the surficial sand and gravel
aquifer in the LeHillier area. Identification and reduction of possible TCE
sources would be more difficult than with A-lor A-2 extraction operations
and, therefore, a permanent final remedy to the site may not be achieved.
Groundwater Treatment. A-3 incorporates no treatment of extracted groundwater.
Groundwater Dischar~. A-3 involves discharge of extracted groundwater directly
to the Blue Earth River through an outfall located on the west bank of the
river.
Discharge of extracted groundwater from the single blocking well into the Blue
Earth River would result in estimated in stream TCE concentrations consideraDly
below the water quality criterion for the 10-6 excess lifetime cancer risk. of
2.8 ug/l from the start of the blocking well extraction. Based on the Q7,10
flow in the Blue Earth River, dilution of the groundwater discharge would
result in an estimated maximum TCE concentration of 0.84 ug/l in the river.
Le~illier ~aterIsuppl~.d A-3 tinCl~des fthtehsamHUeDadc~ion~bas.A-1 fOtr LeHtilllielr
wa er supp y. t incTu es ex enS10n 0 e 1str1 utlon sys em 0 a
LeHillier residential dwellings and private commercial operations affected bj
the existing TCE plume.
Mankato Water Supply. A-3 does not involve physical changes to the existing
Mankato water supply system. A-3 includes monthly monitoring of the Ranney
collector discharge for VOCs according to the summary schedule in Table 1.
Alternative No.4 (A-4)
Groundwater Extraction.
containment.
A-4 does not involve groundwater extraction.or
Groundwater Treatment. .A-4 does not involve treatment of extracted groundwater.
Groundwater Discharge.
A-4 does not involve discharge of extracted groundwater.
LeHillier ~aterl~u~pl~.d A-4 tinCl~des tfhethsamHUeDadctitOn~bats.A-l fOtr LeHtill,ielr
water supp y. ~ lncTu es ex enS10n 0 e is rl u 10n sys em 0 a
LeHillier residential dwellings and private commercial operations affected by
tne TCE plume.
Mankato Water Supply. A-4 does not involve physical changes to the existing
Mankato water supply system. A-4 includes monthly monitoring of the Ranney
collector discharge for VOCs according to the summary schedule in jable 1.
Alternative No.5 (A-5)
A-5 is the no action alternative. Under A-5, no further work of any kind
would be done at the site by the U.S. EPA. .
-------
- 10 -
ALTERNATIVE MONITORING
Groundwater, surface water, and water supply sjstems must be monitored as part
of all alte.rnatives con~idered for LeHilli~r. Monitoring would serve to document
the performance of an implemented remedy, direct corrective actions as contin-
gencies in case of remedial failure, and confirm the qUdlity of drinking water
supplies.
A schedule of monitoring for VOCs was developed for each remedial alternative as
shown in Table 1. The estimated costs for monitoring under each alternative
are based on this schedule.
Consistency with Other Environmental Laws
The HC? [40 CFR 300.68] establishes the procedures for determining appropriate
remedidl actions at Superfund sites. Generally, U.S. EPA will implement
remedies that meet the standards of applicable or relevant Federal public
health or environmental laws. Other environmental laws and guidance which
may be applicable and/or relevant to the remedial alternatives evaluated in
tne FS are the Clean Water Act, Clean Air Act, and the Resource Conservation
and Recovery Act (RCRA).
The Resource Conservation and R~covery Act (RCRA) is not considered to be
applicable to the relnedial alternatives considered in the FS because of the
lack of a hazardous waste "regulated" unit. RCRA was intended to regulate
facilities used for the treatment, storage and disposal of hazardous waste.
Such a facility does not exist at LeHillier. However, though not applicable,
the RCRA Subpart F ground water protection standards are considered relevant
in determining the appropriate level of cleanup since the major portion of
the aquifer underlying the community is contaminated witn TeE and peE. .
However, certain procedural aspects of implementing RCRA Subpart F ground
water protection standards have not been used because they were developed for
hazardous waste facilities, specifically, the RCRA ground water protection
standards process for establishing an alternate concentration level' (.A.CL).
.. Instead, a ri sk management approach supported by the endangerment assessment
in the FS, prepared as Outlined in the "Guidance on Feasibility Studies Under
eERCLA" has been used.' The ilMlediate goal of protecting human health and the
environment is the same, only the procedural aspects differ. At this point
our goal will be to achieve 10-6 levels within the aquifer which is considered
an acceptable level for drinking water consumption.
. As part of alternatives 1, 2, and 3, contaminated groundwater would be withdrawn
by extraction wells and would be discharged to the Blue Earth River. Only
alternative 2 involves treatment of ground water. The Clean Water Act provi-
sions for regulating the discharge of wastewaters are administered by the
State through the National Pollutant Discharge Elimination System (NPDES)
program. Under that program, the State establishes effluent discharge limits
based on the different criteria: 1.) application of best available technology
(BAT) and 2.) protection of water quality by meeting State water quality
standards. Water Quality based effluent limits would be derived for each
contaminant by reviewing accute and chronic toxicity data and the calculating
allowable levels in the receiving surface water. For treatment of VOC contam-
inated groundwater air stripping is considered BAT.
-------
--
------
table 1
SIMIAn 0' VOC ttOIIlJOIlI1C 5CIIlIJIJIfS rOil ASSfHBI£O AlnRIIATlV£S
A..~"'h' Allernethe "!!:.l.- hl_I~' AllernaUve ""- ) Aau,""h' A !!!!!!.!!.!~!....!!!!_d....- A....I.d A \rernet !-e 110- ~
rulod \lu8bu of hr Iud _u of Pulod ""'er.f ,..Iod .........
_~~1!.~~~1'!.~ !!!.!!.!l Frequency S_lu !.!!!!..!! !!.!!uency ~!!... !.!!!!!! !uqu.nc, $aepl u lli!!!! rr~quenc, ~
1. r.".t t I -on Wr' I.
""Jlh Yo II Oll
-------
- 11 -
Under alternatives 1, 2, and 3, ambient water quality criteria i.e., less
than 10-6 .risk of increased cancer incidence (2.8 ppb) are being met. However,
when a best professional judgement (BPJ) evaluation is performed on all alter-
natives, only alternative 2 meets the BAT requirements under the Clean Water
Act.
Alternative 2 would also result in an air emissions of TCE. Under State
emission standards and with the assumed concentrations to be treated by air
stripping, no additional treatment of air emissions (e.g., granular activated
carbon) treatment will be necessary.
COST ANALYSIS
Estimated capital costs, replacement costs, annual operation and maintenance
costs, and present worth for each alternative except no action are presented
in Tables 2.to 5.
SELECTION OF RECOMMENDED ALTERNATIVE
This presents the rationale used to select a single recommended alternative
for the LeHillier site. The NCP [Section 300.68(i)J requires U.S. EPA to
select the "lowest cost alternative that is technologically feasible and
reliable. and which effectively mitigates and minimizes damage and provides
adequate protection of public health, welfare, or the environment."
ALTERNATIVE COMPARISON
Alternatives A-4 and A-S
The limited action (A-4) and no action (A-5) alternatives are considered
ineffective in preventing further contaminant migration and would not mitigate
existing TCE contaminant at the site. The exposure assessment and sensitivity
analysis presented in t~e RIfFS reports conclude that there is a potential
for exposure of the public to TCE and other volatile contaminants at the site
at concentrations that.may adversely affect health and welfare. Remedial
action is therefore required to reduce or minimize this possible exposure. On
the basis of the need for remedial action at the site, the limited action
(A-4) and no action (A-5) alternatives are not appropriate at LeHillier and
are not carried forward to final selection.
ALTERNATIVE A-3
Alternative A-3 would effectively block further northward migration of TCE
toward the Mankato Ranney collector. However, A-3 is not considered an
aggressive remedy that would lead to eventual identification or reduction
of suspected TCE sources. If active TCE sources exist, restoration of the
aquifer to acceptable concentrations may not be achieved for a very long
time. Further identification and subsequent remediation of TCE sources may
never be achieved.
-------
1,\llt E 2
cmH ER r I""H E f;&JltIW\HV
nS5El'lnLEU nL.1 EIU"" r I VI:. :
01\ -I
;;;=::=::~;;::===============c~========~~==============;==;=====;;=========:=====~===:
I'\I'II-IIIIU. : PIU::SEtH :EsllI'1nH.u.
: U&I'I t:Wj 1 S :L-UJU III : PUESEN I
:P(:.IUUI)(VUS) n...lUUrll
CI\P 1 ,nL
CU51
eos r CU"If/UNEN I
===========================I==================I=====~;====:===========:===:==;=~=~=:.
. .
. .
I.
1 WO EX IImer 1 UI't WELLS
... 126, (.(le)
... I 2. 1)(11)
10
$,~E.E.. (JUI)
.-.
.:..
o CUE "JELLS
" 15'. . (11)('
"'23,1)')1)
II)
....~ 1 '. . 1.1111)
oj.
UISCllnnm:: Ff\CILllIES
1\.
Nun III "'ELL
$2 I . (1(1(1
.,. ,::. ::1(11)
II)
~ 4 7 . 1)1.11)
[c.
s.
WELL (I. CUE WELLS
!(.21)(.., (11)('
f. I rJ, 1)(11)
II}
" 'I 3 1 , (11)1)
. ..
.. .
tlun I.U\lEn 5V5IE'.. EXl.
(I. WELL nI:4f\NUUNNEN r
.. 1(10. I)(tt)
.
.
" 1 6 1 , (.(11.1
c
J.
=================~===========c===~==========::=====;==============cc=====~=========:
I vnR 1 nt~LE
20
.. 1 77. (11)('
'-IUN I I un I NG
CONS' n. SU[-41 01 nL
(. I U CliNIINuENC'( (101-)
5COl-'E CUIU INI3£NCV (151-)
$(;15, (11)1)
$f.2, OOt)
't. 'J2. 1)1)1)
---------:
CUNS III.
11 II nL
.. 763, (11)(1
LEGI\L A nUl'll N 1511U\1 I VE (t 01-) I
, ,,7.,. .)t)(.
---------:
IUlfiL
II.tPLE"IEN 1 n' 1 UN eus r
... U 'I E., (u) 0) ':
ENtj 1 NE I.: U 11m & liE S I GI-I
( 11.11-)
!f. 1 7 , ('(11.1
=::;;=:: =:: :~:: ==:: ==:=====:===c====:: =-::=:.:====:~=;:.:",,::===:====:== ==:: ::===~~~- ::======== ==:: ==;=:===:=:::~::~ :
:: -:: =:>:::: =::::~::::;::.: ==== ;::.::::=== ==-== ==,.._::::.;:: :== c::: ===<=== =:.::~= :,~=<=:;::.:::.:::: =:::::=:: == :.:== ~= ==0::==:: :::::::= ~::== ===:.: =:: =, :
E!.i I II'"'' E
... 3~:: 3. 1)(":'
I .. . , '. ::If.. (".11)
lu,nL ells'
.
II nF! a r-l/ \-11111111 (IF (lA 1'1 t:lJ~ i I ! i I ~i OE' E W-II NE U , UII n
-. - -....".,,, "",;!!; nUl: L~it:'U.'''I:U 1\1 I,"/. .
1111-
IN' £: liES r un u::
-------
----------------------------------------------------------------------------------.
COB I- U;III,"\IL btIl'lN,"i¥
f.\!.i!iENlILEU f\L I EIU-II\ I 1 VI: ,
.:.
euS -.
-------------------------------------------------------------------------------=~._-:
COlt 11 nL
CUS I ~j
:IIUE5E.NI :EsrnlnIEU.
I ",..sI'lUf\L : won I II : PIfESEN r
: (HI.'" co~;rs: PERI 00 (VH5) I won t H
COMPlINE N r
I .
lWU E X I If I\C , I ON \-JELLS .'2f.,1)1)1) ...'3,(11)1) 10 ... 2 7 " ,(11)(1
.
.
n CUE \-JELLS 'to , 5" ,1)1)(1 '1.23,000 1(1 ... 37" , 1)(11 1
2.
3.
UISCllnRGE fnCILITIES
I
. .
.
n.
Nun 1 I 1 \-IELL
I
I
:
WELLS:
+2 I , 1)(11)
'''2, ::;1)0
II)
... 'I 7 , 1)(11)
"''3,1)(11)
"'3, 5(11)
II)
...35,1)(11:1
[-4. SUU III WELL '- CUE.
'I. I I I , (1I)(t
I
'to , 5, 1)01)
c
oJ
t: 2 '::5, (t(lI)
I, .
n I II !.i tlU I'P I Nt;
" , (, , , (1(11.1
5.
Hun t.J01EU 5VS-iEfoI EXl.
& \.JELL o[,nNUONMEN..
... 1(10, 0(11)
E..
-----------------------------------------------------------------------------------'
I
I
: vnn I OEILI::
21)
..., 77, (Ifll.l
NUN I lOIU NB
CUNSIR. SUlttOrOL
[t I 0 cm'" II'IGENCY (10:1.)
SCOPE CUNIINGENCV (15~)
-- - ... 52'3, (1(11)
.-53, (11)1)
... 1'3, (il.t(t
---------:
... (,f, , , (11)(1
I.
CON5In.
IUlnL
1 U" f-\L
1 MPLEI1EN t n I I UN COS'
"'E.G,I-'I)I)
---_-----1
... ., ,-::. 1 , (1(11)
.
",
LEGnL" nUI>IINI51nnIIVE(I01-):
ENGINEEnlNG '- UESluN
--~-~-~---~~._----------=----_._-"._-------=-------~---~----=-==--~-=--"---------="'
( 10;()
f.(,E;, (1(11)
10H\L COSI
-~------------------=--~-------_._-~-----------------=------_.~-----~----_._~--=---:
:. .. I , E'3.3, ,-,'-'I,'
"'7'33,(1(11)
EH 111-11\ fE
.
pnE~iU.1I UIJUII' UF (HlI" cml'~; I~t 1)1: lEI1I11NrO rult 1\ 10;'.
E' E C 1111 t:1\l. n)!"j' ~ nnE E !;cnUH En rH 't 1- .
IN1EnE~t
n01E .
" ."-
-------
-, ;UtLE 4
emn E!_i 1 I...n I E ~lI",...nuY
OSSEM£4LE 0 nLI E nNn 1 I VE
: nn--3
-====~==================c========================~=========================~========:
cnST CUMPONENT
cnp I TnL
: COSTS
:-==============================================:=========I============:=======~====I
t" I GnOll UN CUN rrmL
'.'ELL
(BLOCI< 1 NG1
1
I
, I,
1
$7(1,(1(11)
- .
UlscunamE rnCILlllES
$2(;, (11)0
I-tUO ,.,n rE U ~jvnl FN EX l.
& WEL.L ,-mmmONNEN I'
$ 1(10, (1(11)
',. ' -1..flN I I mn NB
: nNf\/I JI\L : fJnEsENt
: U80M cnsl 5 1 wmu"
:PEnIOI>
... '3, 5(11) 30
1
I.
$2, 5(11) I 30
: vnn I rH," E
IFSTIMnTED .
1 PRESENT
(VRS) Iwunnl
I
. .
$21 t, (11)(1
$E.~, (11)1')
f> t f., t , 1')(11)
t'
t
31)
...3 I f"t 1)(11)
, =========~============================~==~========~===================:=======~~=~=:
.
- .
~ : ;JNS ( n. sur.., () H\L
j: ! 0 CONt II'U;ENCV (t 01-)
~CUPE CON'INUENCY (151-)
f, 21-' ", (1(1(1
$20, '1(11)
... 3(1, (;(11)
---------1
- !JN51 n.
H)J nL
$255,(1(1(1
L !:.GnL & nOM I N I 51 nn ( I VE ( 1 (t~)
$25,50(1 1
---------1
$201),51)1)
ruTnL
I MPLENEN 1 n T I UN CDS r
u,mINEERING & UEBH,N
( 1 (11- )
$25,50(1 1
I
--~=======~=================c==========~==========z==================================:
... 751, (1(,1)
':-lunL CUST ESI H'OTE
- .. 31)(" (1(11)
:,==~================~=====~»===~c=================~==================a==============1
PHEBt--_'-II '.JIlin" !IF 1l1l11 r.tlHIB IS m::1Em"INEU r()n n 11)1-
I~Lr 'I:I\L UI~jl!:i (\liE E!;CnUUI:.I> (\1 ',1- .
INIERE!:ir ruBE.
.
. .
-------
lAr-tLE 5
cns rEST IMIHE SlU1Mnnv
nSSEf'JElLED nLI EUNn riVE J
nn -It
=;==~=====~=====~~==a============================~===================
COST CONPONENT
r:lW I r AL
cosr
I nNt.lUAL : E 5 TI MA , E I> .
IUIM COS1St PRESENr
I . WOR1..
. .
. .
=======================~===I==================:=========1
::1======:::===:
I.
"un wnrER svsrEM EXT.
A WELL nBnNI>UNMENT
I
$108,000 I
$ 1 e. 1 , (tOO
.-,
.:..
====;==============================================~=================:
NUN I ron I NB
:vnRIABLE
$318, (U)(I
. CONS' R. SlIftTtHAL.
[41 () CON' I NGENCV (I (I~)
SqJPE CON 1 1 Nt3ENCY (151- )
'$108,(1(1(1 :
1010 ,(tOt) :
tolE-,OOt) :
------:--~- :
CONSln.
"O:lnL
'$ 1 3/, ,(.(1(1 I
LE GnL 3. I\Ul1ltU 5 IIUH I VE Ci ')1-) :
.
.
$13,5(11)
-.-------- :
TO lI\L
I "'PLE.NE"" IH I UN CUS f
$ II, 7 ,5(11) :
ENljINU::UING & nE51GN
( (1)1-)
'$ I 3, 5(11) I
I
===~=~~=~====================~=======~==================~===========
==~~~=~=========;==============~=================~=============~====
lU1f\L COG I
EB' 1"101 E
... 1 £:.1 .,0(1) :
$53'3,(1(1(1
.
Prff ! il: N r L-.un III or- NUN I( on 1 NG CD5 r s
unlL liVEn n 3') VEnn PEnIOD.
15 DE1EI1MfI'IEI> FOR n 1')1-
INIERfST
........ -..-:
-------
- 12 -
A more aggressive TCE extraction alternative is considered necessary to
achieve groundwater remedial goals and possible identification for TCE sources.
Therefore, alternat1ve A-3 is not selected for implementation.
ALTERNATIVES A-I AND A-2
Alternatives A-I and' A-2 would mitigate the TCE contamination by aggressively
removing the TCE plume within a relatively short period of time. Both alter-
natives also minimize further TCE migration.
Both A-I and A-2 provide an agressive groundwater extraction remedy which
could lead to the eventual elimination or identification of suspected TCE
source areas for future remediation as part qf the final remedial action.
Both alternatives are in compliance with current environmental laws and
regulations. Because estimated capital costs and present worth of A-2 are
less than A-I, the recommended alternative is A-2.
RECOMMENDED ALTERNATIVE (A-2)
Recommended alternative A-2 is shown on Figure 5. The discussion below
summarizes the reasons for the selection of A-2 as the recommended remedial
alternative for the LeHillier site.
A-2 would provide environmental benefit by aggressive extraction of the TCE
plume that would eventually reduce TCE concentration in the aquifer to less
than the 10-6 excess lifetime cancer risK concentration of 2.8 ug/l, which is
considered a concentration acceptable for public use. The time to achieve
acceptable concentrations in the aquifer has been estimated at 5 to 10 years
under the assumptions used to develop A-2. .
By the
reduce
during
future
aggressive arrangement of extraction wells, A-2 would also tend to
or pinpoint and tdentify active sources of TCE in the LeHillier area
operation. If identified, source areas could be remediated at some
time.
A-2 complies with applicable and relevant environmental laws, guidances, and
standards. In particular, A-2 would comply with groundwater remedial
requirements of RCRA 40 CFR 264 SubpartF, surface water quality standards
and BAT requirements that would be imposed under tne NPDES program, and air
emission standards developed under the Clean Air Act.
A-2 would minimize and would prevent uncontrolled migration of TCE and other
site contaminants northward toward the Mankato Ranney collector. The public
water supply for the LeHillier community would be made acceptable by extension
and connection of all affected residences and commercial establishments to
the HUD water supply system.
In terms of estimated cost, A-2 is lower in estimated capital costs and
present worth than the comparable alternative, A-I, that also includes the
multiwell extraction approach. A-2 is considered the more cost-effective
alternative between these two. .
-------
I
I
I
--- --------/
\
\
\
(
\
\
. ..,.,...,
...... .'0
. ....., .
.....,,,,,IC'''. .
I
,.
I
/
/
I
I :
1 , ~
\ '. \
"\ \
. ./: \ \_._.~.
" u':.') :~~\....'e..:
. :... I '''_'D ... 00_"..'
' . . , ~ OO""'.~'"
'.," /" / .,..,..
::>~o;I!<: ~/;"'))
'~'!' . 0 :
.:.. ;' ~ ,/ - .-.) (
" '. - - ~ ~.~ - , . -~ n
-- ':: : ~. ,- - - , '- - - - ~ -", '.; , '" /' ~ I
" - :.:-- - - .-:_~--.::~ - , . (- i :
..:.-~ - -,~::;-:.=. - ,......":" '...:'.-...- I - f', \ \ ,I : ~ II
=-""'" " -'
'" . "" , , - , .
. ", . " . .' '.' -, \ ' . 1 IS'" =1 ~ .,.
, " ., \, n..-
I il 1'-
I " I i /
, " !
.c I'
".....
'."
WI'" .,. ::::s.c...
II.I'f CCI -...." .. fT'" C" II
In..C'T'c. 81\1 ~
J
UD ~ "'. ......"'.,
~::.7."",o- ..I_I.
,
I
:r'
iI!
-<
0_0-
..--, -.ACT'D"
ID~" .0
..~... ..0 ....
n.,,...
'n~ COt ceev,'"
- ,,,'.-C.fllf08 .,...
.:.. ~'
C' 70..
600'
tnt...OOo '0
'._10 ""-'000 '"fT'''
,,~ OIITa....,.
--
-
F leuRE
5
-------
- 13 -
OPERATION AND MAINTENANCE (O&M)
Activites would include the routine operation and maintenance of pumps and
the air stripper. Other costs would consist of electrical, monitoring, and
inspectio~ costs.
O&M of the extraction pumps may be over a ten year period. The air stripper
may be removed within 5 years if effluent meets the technical requirements of
the NPDES program. It is expected that TCE levels will be significantly
lower at this time.
EPA will be responsible for 90 percent of the first year of O&M at a cost of
$70,000. The State of Minnesota will continue O&M for the remaining duration
which should not exceed 9 years.
COMMUNITY RELATIONS
Community relations in this commumity began with the U.S. EPA bottled water
program that was begun October 3, 1983. Official Superfund community relations
efforts were initiated in June 1984. On-site discussions were conducted for
the Community Relations Plan that was finalized that June. "An ad and a press
release were used to announce the RIfFS kickoff meeting held June 27, 1985.
A repository was established in early July and the first fact sheet, published
in September, was placed in the repository as well as being sent to the
mailing list.
During the RI there was a certain level of interest maintained due to the
difficulty of implementing a HUD water system. The problems were of a local
political nature rather than part of the U.S. EPA RI technical work, but kept
the project in a high profile. There was some congressional interest in the
beginning. .
Although this was a federal lead project, the State took the lead on community
relations in September through a multi~site cooperative agreement (MSCA) and
took over the bottled water program in December.
The results of the RI and the proposed action of the FS were announced at the
same time at a August 21, 1985 public meeting. A press release and an ad
announcing the proposed action went out in August and the State prepared
separate fact sheets for the RI and FS. . Tnese, along with the full reports,
were added to the repository;
The public meeting was attended by 25 residents and press. The presentation
was followed by a few comments and one additional comment came by mail before
the September 3, 1985 deadline. With the HUD situation having been resolved
the night before our meeting, pUblic response was favorable for our selected
remedy. All commenters expressed their desire that the project be implemented
as soon as possible.
-------
- 14 -
One c~mnenter also was concerned about water quality impacts on aquatic life
when effluent under selected alternative A-2 is discharged into the nlue
Earth River. The discharge of all wastewaters are regulated by the State
through .the NPDES program. Under that program, the State establ;sn~s effluent
discharge limits for all applicable water quality stdndards which are developed
in a NPOES permit. Parameters to be monitored will be designated by the
State dependent upon stream. classification and anticipatej effluent character-
istics. It is U.S. EPA and the State's intent to monitor and comply with all
effluent limits applicable to this site. This may include other parameters
such as dissolved oxygen and temperature.
SCHEDULE
Because of the uncertainty of reauthorization of Superfund, Federal design and
constr~ction funds will not be readily available. The State of Minnesota has
expressed a willingness to continue into design phase using State Superfund
monies with the understanding that use of their fund will be considered part
of their 10 percent match in construction. A Cooperative Agree,nent has been
prepared and submitted to the Region for approval.
Upon approval completion of design could be achieved within a six month
period. If Federal funds are available, the construction could begin in the
third ~uarter fiscal year 86 (FY86). The following schedule is contingent
on the above.
November 1985
MPCA will formally request that its board
approve the selected remedy and authorize use
of State funds to implement design phase of
LeHillier project.
Initiate design ph~se.
October 22, 1985
May 1986
Completion of design phase.
June 1986
Start construction of remedy.
FUTURE ACTIONS
Besides managing contaminant migration, this action will control and agressively
reduce continuing sources, if any, until the groundwater reaches drinking water
. quality. By periodic monitoring groundwater quality, operational data will be
used by U.S. EPA and the State of Minnesota to evaluate performance and assess the
likelihood of reaching our goal of 10-6 lifetime cancer risk levels forTCE
(2.8 ppb). We estimate that our goal can be achieved within five years if no
continuing source exists. If continuing sources still exist after five years,
we could achieve our goal within ten years by either continuing the aggressive
pumping action and/or installing source controls as necessary.
------- |