United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
EPA/ROD/R03-89/077
September 1989
3EPA
Superfund
Record of Decision
New Gastle Spill, DE
-------
50272-101
REPORT DOCUMENTATION 11. REPORTNO.
PAGE EPA/ROD/R03-89/077
2.
3. A8c1pient'. AcC88810n No.
4. TltIe.nd Subtitle
SUPERFUND RECORD OF DECISION
New Castle Spill, DE
First Remedial Action - Final
7. Author(.)
5. Report D...
09/28/89
I.
a. P8rf0nnlng Org8llization Rept. No.
a. Perfonnlng Org.lnlzation Nllme .nd Add....
10. ProjectlT.8klWork Unit No.
11. ContnIc1(C) or Grant(G) No.
(C)
(G)
12. ~orIng Organlz8tlon Name and Addr-
U:S. Environmental Protection
401 M Street, S.W.
Washington, D.C. 20460
13. Type of R8pOft . Period Covered
Agency
800/000
14.
15. Supplementary No..
16. Ab8tract (Umit: 200 _rd.)
The New Castle Spill site is a former manufacturing facility 0.5 mile north of New
Castle, Delaware, and is in 'the 100'-year floodplain of the Delaware River. Commercial
enterprises and residences neighbor the site and receive potable water from the deeper
of the two aquifers underlying the site. The six-acre area associated with the site
consists of municipal property, wetlands, and the Witco manufacturing facility which
.roduced plastic foams using (2-chloropropyl)-phosphate. In 1977, because of dead
~rass near the facility's drum storage area, witco investigated the area and determined
that four to five drums of tris had spilled and contaminated the soil and the shallow
aquifer. The State' subsequently pumped and diicharged contaminated ground water into
adjacent wetlands. A 1988 remedial investigation revealed that there is no longer a
source of contamination at the site and that tris has contaminated the shallow aquifer
but not the deeper aquifer. This limited response action addresses the ground water
contamination in the shallow aquifer. The primary contaminant of concern affecting the
ground water is (2-chloropropyl)-phosphate.
The selected remedial action for this site includes natural attenuation as the
treatment of the principal threat to ground water; ground water, surface water, and
sediment monitoring; and implementation of institutional controls. The estimated
ISpp ".....~~1-.~A Shppj-\
17. Document Analyai. L Descrlptora
Record of Decision - New Castle Spill, DE
First Remedial Action - Final
Contaminated Media: sediment, gw, sw
Key Contaminants: (2-chloropropyl)-phosphate
b. Identifler8l0pen-Ended Terme
c. COSA TI Reid/Group
~. Av8ilabiUty Statement
1a. Security Cia.. (Thia Report)
None
20. Secwity Cia.. (Thla Page)
N(')np
21. No. of Pagea
43
22. Price
(See ANSI.Z3a.18)
See Instructlona on Rave,..
272 (4-77)
(Formerty NTlS-35)
Department 01 Commerce
-------
DO NOT PRINT THESE'INSTRUCTIONS AS A PAGE IN A REPORT
INSTRUCTIONS
Optional Form 272, Report Documentation Page la based on Guidelines for Format and Production of Scientific and Technical Reportsr
ANSI Z39.18-1974 available from American National Standard8lnatltute, 1430 Broadway, New York, New Yone 10018. Each separately
bound report-for example, eech volume In a multivolume set-shall have Ita unique Report Documentation Page.
1. Report Number. Each Individually bound report shall carry a unique alphanumeric de.lgnatlon a88lgned by the performing orga-
nization or provided by the sponsoring organization In accordance with American National Standard ANSI Z39.23-1974, Technical
Report Number (STRN). For registration of report code, contact N11S Report Number Clearinghouse, Springfield, VA 22161. Use
upperca.ele"er.. Arabic numerala, slashea, and hyphen. only, a.ln the following examplea: FASEBIN5-75/87 and FAAI
RD-75/09.
Leave blank.
2.
3. Recipient'. Acceulon Number. Reserved for u.e by each report recipient.
4. TItle and Subtitle. 11tle should Indicate cle...ly and briefly the sub/ect coverage of the report, subordinate subtitle to the main
, title. When a report la prepared In more than one volume, repeat the primary title, add volume number and Include subtitle for
the specific volume.
5. Report Date. Each report shall carry a date Indicating at lea.t month and year. Indicate the basla on which It was selected (e.g.,
date of Issue, date of approval, date of preparation, date published).
6. Sponsoring Agency Code. Leave blank.
7. Author(s). Give name(s) In conventional order (e.g., John R. Doe, or J. Robert Doe). List author's affiliation if It differs from
the performing organization.
8. Performing organization Report Number. Insert If performing organlzaton wishes to a88lgn this number.
9. Performing Organization Name and Mailing Address. Give name, street, city, state, and ZIP code. Ust no more than two levels of
an organizational hlerac'hy. Display the name of the organization exactly as It should appear in Government Indexes such as
Government Reporta Announcements & Index (GRA & I). -
10. Pro/ectlTaskIWork Unit Number. Use the project, task and work unit numbers under which the report was prepared.
11. Contract/Grant Number. Insert contract or grant number under which report wa. prepared.
12. Sponsoring Agency Name and 'Mailing Address. Include ZIP code. Cite main sponsors.
13. Type of Report and Period Covered. State Interim, final, etc., and, if applicable, Inclusive dates.
.
14. Performing Organization Code. Leave blank.
15. Supplementary Notes. Enter Information not Included elsewhere but useful, such a.: Prepared in cooperation with. . . Translation
of. . . Presented at conference of . . . To be published In . .. When a report Is revised, include a statement whether the new
report supersedes or supplements the older report.
16. Abstract. Include a brief (200 words or less) factual summary of the most significant Information contained in the report. If the
report G.Jntains a significant bibliography or literature survey, mention It here.
17. Document Analysis. (a). Descriptors. Select from the Thesaurus of Engineering and Scientific Terms the proper authorized terms
that Identify the major concept of the research and are sufficiently speclffc and precise to be used as Index entries for cataloging.
(b). Identifiers and Open-Ended Terms. Use Identifiers for project names, code names. equipment designators, etc. Use open-
ended terms written In descriptor form for those subjects for which no descriptor exists.
(c). COSATI Field/Group. Field and Group assignments are to be taken form the 1964 COSATI Subject Category Ust. Since the
majority of documents are multidisciplinary in nature, the primary Field/Group assignment(s) will be the specific discipline,
area of human endeavor, or type of physical object. The appllcation(s) will be cross-referenced with secondary Field/Group
assignments that will follow the primary postlng(s).
18. Distribution Statement. Denote public releasability, for example "Release unlimited", or limitation for reasons other than
security. Cite any availability to the !)ubllc, with address, order number and price, If known.
19. &20. Security Classification. Enter U.S. Security Classification In accordance with U. S. Security Regulations (I.e., UNCLASSIFIED).
21. Number of pages. Insert the total number 01 pages, Including Introductory pages, but excluding distribution list, if :1ny.
22. Price. Enter price In paper copy (PC) and/or microfiche (MF) if known.
* GPO'
19830- 381-526(8393)
OPTIONAL FORM 272 BAC.L"
( 4-77)
-------
. EPA/ROD/R03-89/077
New Castle Spill, DE
First Remedial Action - Final
Abstract (Continued)
present worth cost for this remedial action is $466,147, which includes O&M costs of
$25,000.
-------
RECORD OF DECISION
DEClARATION
Site Name and Location
New Castle Spill Site
New Castle, Delaware
Statement of Basis and Puruose
This decision document presents the selected remedial action for the New
Castle Spill Site, in New Cas tIe, Delaware, in accordance with the
Comprehensive Environmental Response, Compensation and Liability Act of 1980,
as amended by the Superfund Amendments and Reauthorization Act of -1986,
Section 113 (k) (2) (B) (v), and to the extent practicable, the National
Contingency Plan. This decision is based on the Administrative Record for the
site. The attached index identifies the items which comprise the
Administrative Record upon which the selection of the remedial action is
based.
Assessment of the Site
Actual or threatened releases of hazardous substances from this site, if not
addressed by implementing the response action selected in this ROD, may
present an imminent and substantial endangerment to public health, welfare, or
the environment.
.
Descriution of the Remedy
New Castle Spill Site has One Operable Unit: groundwater contaminated with
tris in the Columbia aquifer. This Operable Unit no longer has a source of
contamination but requires a groundwater response action to address the
potential threats posed by the contaminated groundwater. The underlyi.ng
Potomac aquifer separated by a confining layer from the Columbi.a aquifer is
not contaminated. The remedy selected for the site is limited actiol1, which is
monitoring and institutional restrictions. In utilizing this remedy, the
principal threat at the site is not physically treated, but is allowed to be
cleansed through natural attenuation.
The major components of the selected remedy include:
o Monitoring the Columbia aquifer on a quarterly basis for tris'to ensure the
effectiveness of the natural attenuati0n process.
o Monitoring the Potomac aquifer on an annual basis for tris to ensure that
contamination has not occurred in the Potomac aquifer.
o Monitoring the surface water. of the wetlands adj acent to the site on an
annual basis for tris. Resample in the next quarter if a~ anomaly occurs in
the results.
-------
o Further evaluation and bioassay testing if the trigger value of 100 ugjl
tris in surface water of the adjacent wetlands is reached.
o Monitoring the sediments of the wetlands adjacent to the site on an annual
basis for tris. Resample in the next quarter if an anomaly occurs in the
results.
o Further evaluation and bioassay testing if the trigger value of 1000 ugjkg
tris in the sediments of the adjacent wetlands is reached.
o Institutional restrictions on the placement of wells
aquifer in the vicinity of the site.
in
the Columbia
o
A five year effectiveness review to re-evaluate the site.
Declaration Statement
The selected remedy is protective of human health and the environment and is
cost-effective. There are no applicable or relevant and appropriate
requirements for tris, but this remedy meets the equivalent standard criteria
"to be considered" in lieu of applicable or relevant and appropriate
requirements. This remedy consists of monitoring for tris together with
periodic evaluations to ensure that the natural degradation process is
yielding the expected permanent result, that is, the decrease and eventual
disappearance of tris in the Columbia and adjacent wetlands. This remedy does
not satisfy the statutory preference for treatment as a principal element of
the remedy. The present lack of human and environmental receptors and the
natural remediation process makes treatment of the groundwater unnecessary.
Because this remedy will result in hazardous substances remaining onsite above
health-based levels, a review will be conducted within five years after
initiation of remedial actions to ensure that the remedy continues to provide
adequate protection of human health and the v~ 0 ent.
Philli G.
Director
Division of Air
Management.
Department of .Natural Resources
and Environmental Control
State of Delaware
and
Waste
DATE~~1)t7
DATE .h~ 2~ /1cfCt
~~
Edwin B. Erickson
Regional Administrator
EPA Region III
-------
1.
NEiol CASTLE SPILL
ADMINISTRATIVE RECORD ~
INDEX OF DOCUMENTS
SITE IDENTIFICATION
1) U.S. EPA Identification and Preliminary Assessment, 6/19/80.
P. 100001-100004
2) Brief Summary Sheet for Witco Chemical DE-33, 8/19/8.0.
P. 100005-10005
3) U.S.EPA Site Inspection Report, 9/23/80. P. 100006-100015
II. REMEDIAL ENFORCEMENT PLANNING
1)
Secretarial Order by Consent In The Matter Of: Witco Corporation,
12/10/87. P. 200001-200028.
The following are attached:
a) a letter regarding the site classification as a state-lead
enforcement site;
b) a report entitled" Work Plan for Remedial Investigation
/ Feasibility Study at the Former WITCO Corporation Site, 900
Wilmington Road, New Castle, DE";
c) a graphical project schedule for the New Castle, Delaware
Site Remedial Investigation/Feasibility Study.
III.REMEDIAL RESPONSE PLANNING
1)
Report: New Castle Soill Technical Review of Documents. Final
Reoort. prepared by PRC Environmental Management, Inc., 2/3/86.
P. 300001-300093.
Report: Work Plan for Remedial Investi~ation/Feasibilitv
Studies ~ the Former Witco Corooration ~ 900 WilminEton
Road.New Castle. Delaware. prepared by Environmental Resources
Management, Inc.. 8/87. P300094-300433.
Report: Final Project Reoort.New Castle ~ Site. New
Castle. prepared by CDM Federal Programs Corporation,
11/11/88. P. 300434-300586.
Report: Final Remedial InvestiEation. Volume 1. prepared
by Environme~tal Resources Management, Inc., 5/5/89.
P. 300587 -300982
Report: Final Endangerment Assessment. Volume ~ prepared
by Environmental Resources Management, Inc., 5/5/89.
P. 300983-301148.
Report: Revised Draft Focused Feasibility Study. prepared
by Environmental Resources Management, Inc. ,8/1/89.
P. 301149-301251.
Memorandum to Ms. Jean Parker, U.S.EPA, from Mr. Michael L.
Dourson, U.S. EPA, re: Toxicity test conducted on rats, 2/6/84.
P. 301252-311252.
Memorandum to Mr. Phil Retallick, U.S. EPA from Mr. Bruce Molholt,
U.S.EPA, r~ Toxicological Assessment of Fryol PCF, 10/15/84.
P. 301253- 301258.
2)
3)
4)
5)
6)
7)
8)
-------
10)
11)
12)
13)
9)
Memorandum~to Ms. Ga1ina Bendersky Chadwick, U.S. EPA, from Mr.
Bruce Mo1ho1t, U.S. EPA, re: Studies on the toxicity of Fryol PCF,
10/15/84. P. 301259-301259.
Memorandum to Ms. Ga1ina Bendersky Chadwick, U.S. EPA, from Mr.
Bruce Mo1holt, U.S. EPA, re: Additional contaminants to be addressed
in the toxicologic assessment, 5/16/85. P. 301260-301261.
Memorandum to Mr. Terry Stillman [sic], U.S. EPA, from Mr. Bruce
Molho1t, U.S. EPA, re: Comments on the Draft Remedial Investigation
and Draft Endangerment Assessment, 10/21/88. P. 301262-301263. .
Report: ProDosed.~!Qt the New Castle ~ Site.
New Castle. ~,prepared by Department of Natural Resources
and Environmental Control and Environmental Protection Agency,
Region III, 8/22/89 P. 301263-301271.
Transcript: Public Meeting for New Castle Spill Site, 9/6/89.
P. 301271-301319.
-------
13)
14 )
16)
17)
~:uI. ~!~ANC! OO~S *
1)
-?~o=ulg.eion of Sites fro~ a~d.ees 1-4, - Federal R~1ster, d.eed 6/10/86.
M?~opos.l 0: ~?d.te ~,- ?ederal Re21ster, dated 9/18/8S.
2)
3)
~e~orand~ to a. S. !?A ~ro~ ~r. G~ne Lucero regardiQ3 co=sunity relac:ocs
ac Superfund !~force=enc sices, daeed 8/28/8S.
4)
Grou=dvater Concami~t~on and Protection, undated by ~r. Conald 7.
Fel~ci.no on 8/23/85.
S)
Me~orandum co ~oxic ~asce ~nag~ent Division Directorl !egionl !-! fro~
~r. -illi&: aedeman and ~r. G~ne Lucero re: Policy on Ploodplaici and
.ecl.ndl Assessmencs for C!1~~ Ac:ionl, 8/6/85.
6)
7)
Guidance of Re=ed1~l !cvesc~~ae:onl under C!XCLA~ daeed 6/8~.
Guidance on ?eaa1~il!c~ Studies under C!X~-A, daeed 6/85.
8)
9)
-Proposal of apdat. 3,- Yederal !~ist.r, daeed 4/10/85.
Me:or.ndum to ~r. Jack ~cGrav entitled -Camaunity telat10na Act!vite.
.t Super~und Sites- !~terim Gl1iunc., - dued 3/22/85.
10)
-Proposal of Update 2,- Federal !~1ster, dated 10/1~/84
11)
12)
EPA Groundwater Protection Strat~y, dated 9/84.
Me=or.ndum to cr.S. ~PA froa Mr. q1111aa aeckman, Jr. entitled
-Trans~it:.l at Sl1perfuad !,~oval Procedure. - 1eTi.ion 2,- dated 8/20/84.
-Propo..l of crpdata 1,. Federal 1~1.ter, dated 9/8/83.
CocmunitT telation. in SI1~er1und: A Handbook (interia verlion), uted
9/83.
15 )
-Propo.al of f~lt !atioaal Priority Lilt, - Yed.ral_t~1ater, dated
12/30t!:2. ~.
-!x?anded !111ib111ty Liat,- Pederal l~iat.r, dated 7/23/82.
-Interia Prioriti.. Liat,- Federal !~iat.r, dacld 10/13/81.
18 )
crnconc=olled Hazardous ~Iat. Sit. !Anki~ Syste8: A cr..r', ~aual
(undated) .
1.9)
?!eld SC3:dard O~e=3~i~1 ?=ocedureu
- " .
Surv.111AIlcI (undaced).
,!Q)
?ield S::~d~rd ~:e~~:.
.'~~C:l!dur~:J -
3.:!~C7 ?lA:1
(u:1c.aced).
. :'.:JC:;1:~~ ~.
:<...:~ ~'::.
. .
. -... a
-------
RECORD OF DECISION
SUMMARY OF REMEDIAL ALTERNATIVES SELECTION
NEY CASTLE SPILL SITE
NEY CASTLE,DELAWARE
DELAWARE DEPARTMENT OF NATURAL RESOURCES AND ENVIRONMENTAL CONTROL
DOVER, DELAWARE
and
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION III
PHILADELPHIA, PENNSYLVANIA
-------
A.
B.
X.
TABLE OF CONTENTS
Declaration
Decision Summary
I.
Site Name, Location and Description
II.
Site History and Enforcement Activities
III.
Highlights of Community Participation
IV.
Scope of Response Action
V.
Site Characteristics
VI.
Summary of Site Risks
a.
Risks from Current Exposure to Groundwater
as a Potable Water Supply
Risks from Future Exposure to Groundwater
as a Potable Water Supply
Risks from Current and Future Exposure to
Surface Water
Risks from Current and Future Exposure to
the Soils
Risk to the Environment from Site Contaminants
b.
c.
d.
e.
VII.
Documentation of Significant Change
VIII. Description of Remedial Alternatives
a.
b.
Remedial Alternative Considered
Major ARARs and TBCs Utilized for Remedial Alternatives
IX.
Summary of Comparative Analysis of Alternatives
a. Comparative Evaluation of Alternatives
l.
2.
3.
4.
5.
6.
7.
8.
9.
Overall Protection
Compliance to ARARs and TBCs
Long-Term Effectiveness
Reduction of Toxicity, Mobility
Short-Term Effectiveness
Implementability
Costs
State Acceptance
Community Acceptance
and Volume
b.
Summary of Comparative Evaluation of Alternatives
The Selected Remedy
Page
1
3
3
4
4
11
16
16
20
23
-------
C.
XI.
Statutory Determination
a. Protectiveness of Human Health and the Environment
b. Attainment of Applicable or Relevant and Appropriate
Requirements
c. Cost Effectiveness
d. Utilization of Permanent Solutions or Alternate Technologies
e. Preference for Treatment as a Principal Element
Responsiveness Summary
Page,
26
-------
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Figures
Site Map
Yater Table Contour Map, Columbia Aquifer
Site Specific Cross Section
Concentration of Tris in OB Series Yells
Tables
Exposure Pathways for New Castle Spill Site
Physical Properties of the Indicator' Chemical
Potential Environmental Exposure Pathways
Summary of Carcinogenic and Noncarcinogenic Risks
Detailed Evaluation of Alternatives
Page
2
6
7
8
10
12
14
15
24,25
-------
I.
SITE NAME', LOCATION AND DESCRIPTION
The New Castle Spill Site (NCSS) is a former manufacturing plant of the Witco
Corporation located 0,5 miles west of the Delaware River and 0.5 miles north
of the City of New Castle, Delaware. The study area associated with the site
includes the Witco facility, the property of the New Castle Board of Water and
Light (NCBt.TL) and the adj acent marsh. This area covers approximately six
acres and is accessible via Route 9, also known as New Castle Avenue,
(See Figure 1)
The Witco facility was formerly a manufacturing plant which utilized tris (2-
chloropropyl)-phosphate (tris) in the production of plastic foams.
The NCBt.TL property was formerly used as a treatment plant for an
production well of the Potomac aquifer and a shallow infiltration
system for the Columbia aquifer. This system served as part of the
water supply for the City of New Castle until its closure in 1978.
on-site
gallery
potable
The area surrounding the site is a mixed commercial and residential area,
bordered on the west by a marsh and on the east by a dual highway, It is
relatively flat and located within the lOa-year flood plain of the Delaware
River, Elevations within the study area range from a to 10 feet above mean
sea level. Surface water drainage from the site follows the gently sloping
topography to the west-northwest and discharges to a marsh, which drains to
the south via the Narrow Dyke Canal and ultimately to the Delaware River.
The marsh area on the west side consists of emergent and forested wetlands
that support diverse flora and fauna. The Narrow Dyke Canal draining the
marsh is a man-made canal for flood and mosquito control that is regulated by
sluice gates at the confluence of the major drainage ditch and the Delaware
River. Little tidal or salinity fluctuation is seen in this surface water due
to the operation of the sluice gates. The Narrow Dyke Canal has occasional
recreational uses.
The geology of the site consists of Pleistocene age sands and gravels of the
Columbia Formation overlying Cretaceous age sands and gravels of the Potomac
Formation. A thick clay layer, typical of the Potomac Formation, exists at
the top of the Potomac sediments in the vicinity of. the site. There are two
aquifer systems at the site: the shallow, or Columbia aquifer, and the deep or
Potomac aquifer. The thick clay layer at the top of the Potomac formation
separates the two aquifers from being hydraulically connected. The shallow
Columbia aquifer discharges to the freshwater non-tidal streams and to the
Delaware Bay and Atlantic Ocean. It is not currently used as a potable water
supply. The Potomac aquifer discharges primarily through pumping for
municipal and industrial purposes. The Potomac aquifer supplies most of
potable water to New Castle County.
The nearest population to the site is located approximately 250 feet west of
the site, on the other side of the marsh. It is a residential community which
receives its potable water supply from wells in the Potomac aquifer. Located
to the south of the site are several commercial establishments also receiving
potable water from the Potomac aquifer. Site access is limited ~y a fence on
the Witco property,
-------
lurea: USGS 7.5 Min. Topographic Quadran
I
FIGURE
1
'~
.N
2000
e; Wilmington Soulh. DE-NJ
New Castle Spill Site Map
r
"1U8&~~G&.&I.,"-......--.-.-~ ~
CavIll 1'1I2a'" .-o....d ....
.1<8G.r1OO
~~
/
I
1
".'. :.!1. UlJllI
-~ ~,likF9nc6
50 25 0
~
50
100
2
. '0 - :=- .,("~B Gals
~<..:- 0.) ; '~III
-------
II.
SITE HISTORY AND ENFORCEMENT ACTIVITIES
In 1977, personnel of NCB~ noticed areas of dead grass on their property
adjacent to the drum storage area of the ~itco facility. This was brought to
the attention of ~itco, who subsequently conducted an investigation which
determined the presence of tris in the soil in this area. It was estimated
that approximately 4-5 drums of tris had been spilled onto the ground.
Shortly following the discovery of the spill, contaminants were detected in
the shallow gallery system supply. Under the direction of the S tate of
Delaware Department of Natural Resources and Environmental Control (DNREC).
the groundwater from this sys tem was pumped and discharged to the adj acent
wetlands. As result of this spill, DNREC requested the assistance of the
United States Environmental Protection Agency (U.S.EPA) in the identification
of tris in the groundwater. This study was conducted in January 1978 and
indicated tris was present in the groundwater.
In September 1981, the U.S. EPA conducted a site inspection at the ~itco
facili ty and the adj acent NCBwl. property. This inspection resulted in a
Hazard Ranking System score of 39.57 and proposal to the National Priorities
List (NPL). In December 1982. the ~itco facility was listed on the NPL as the
New Castle Spill Site. Between 1982 to 1987, numerous studies were conducted
on the site by consultants for the NCB~ and ~itco. The data generated from
these studies was reviewed by EPA and DNREC and used to established the data
needs for the remedial investigation for the site.
In December 1987, an Administrative Consent Order (ACO) was signed by the
~i tco Corporation and the DNREC to address the performance of the Remedial
Investigation/Feasibility Study (RI/FS) and Endangerment Assessment (EA) for
the site. The purpose of the RI was to determine the nature, extent and
magnitude of the contamination at the site. It was accompanied by an EA which
evaluated the risks to human health and the environment from the site. These
activities were initiated by the ~itco Corporation in February 1988 and
finalized in May 1989. Upon their completion, a FS was also begun by ~itco
in June 1989 to evaluate remedial alternatives to the problems found at the
site. The FS was finalized in August 1989 and followed by the development of
the Proposed Plan.
III. HIGHLIGHTS OF COMMUNITY PARTICIPATION
Public participation has been encouraged at the site. Interviews with the
community and local municipal officials, as well as a presentation at a local
municipal meeting have been conducted to familiarize the public with the site
and the findings of the RI and EA. The Proposed Plan was advertised in the
~ilmington-based News Journal newspaper, which has state-wide circulation, to
inform the public of the alternative being proposed for selection. A 30-day
comment period was was established from August 22, 1989 to September 22, 1989
to allow the public an opportunity to review and comment on the Proposed Plan
and other pertinent documents for the site. A repository was established at
the DNREC Building, 715 Grantham Lane, New Castle for public viewing of the
Administrative Record for the site. A public meeting was held on September 6,
1989 to discuss the Proposed Plan and the findings of the RI. EA and FS. The
public was encouraged to comment either at the meeting or in writing. The
comments are summarized and responses provided in the Responsiveness Section
of this document. .
3
-------
IV.
SCOPE OF RESPONSE ACTION
From the RI, several important facts were established and have been used to
develop a response action for this site. The facts are as follows: (1) The
shallow Columbia groundwater is contaminated with tris (2) The Potomac
aquifer is not contaminated with tris; (3) There is no interconnection be~Jeen
the Columbia and Potomac aquifers; (4) The source of contamination from tris
no longer exists at the site; (5) The Columbia aquifer is not currently
being used as a potable water supply, but classified as a Class II B aquifer,
a potential source for water supply; and (6) TCE has been identified in the
shallow groundwater as originating from a site upgradient from the New Castle
Spill Site.
From these facts, it is concluded that a groundwater response action should be
considered for remediation of the site. This response addresses the principal
threat of the sole operable unit at the site, the Columbia aquifer. The
groundwater response action would protect against risks to human health and
the environment through the use of "to be considered" (TBCs) criteria for the
groundwater, surface water and sediments. The TBC for groundwater of 4.4 mg/l
would be used as a cleanup goal for the site due to the lack of Applicable or
Relevant and Appropriate Requirements (ARARs) for the contaminant of concern,
tris. This TBC of 4.4 mg/l tris was derived by EPA as a health based drinking
water level calculated from the RiD for tris of .125 mg!kg/day being consumed
by an adult weighing 70 kg and drinking 2 liters of water per day. The TBCs
for surface water and sediments as 100 ug/l and 1000 ug!kg respectively by the
National Oceanic and Atmospheric Administration (NOAA) would not be considered
as cleanup goals but as trigger values to require bioassay testing and further
evaluation of the wetlands if reached.
The use of a groundwater response action at this slote addresses the risks
presented to human health and the environment from the Columbia aquifer under
potential and hypothetical conditions. Currently, this site presents no risks
since the Columbia aquifer is not being used as a potable water supply and has
shown no adverse impact on the environment. However, since it is classified as
Class IIB aquifer, a potential source of potable water supply, the use of a
groundwater response allows us to provide for future use.
While the RI and EA concluded that tris contamina~ion at the site caused no
determinable adverse impact to human health and the environment, data on
toxicity of tris are limited. EPA intends to conduct further toxicity
testing to better determine any risks to human health and the environment from
exposure to tris. When these studies are concluded, EPA will re-evaluate the
site if necessary.
V.
SITE
CHARACTERISTICS
A Remedial Investigation was performed to investigate threats to the local
groundwater, soil, stream sediments and surface water posed by contaminants at
the site. A hydrogeological investigation was conducted which included the
installation of five monitoring wells, a 6-inch pumping well, and the
performance of a 24 hour pump test involving sustained pumping of the 6-inch
pumping well while water levels in the surrounding monitoring wells were
continuously measured. Groundwater sampling was conducted on the five new
wells and tWelve existing groundwater monitoring wells. A subsurface soil
4
-------
study was conducted which included continuous split spoon samples taken to the
water table at eight boring locations. A wetlands investigation was conducted
consisting of: the collection of surface water and sediments from six sampling
stations; a qualitative macroinvertebrae study; a wetland delineation; and a
habitat assessment. In addition, a tidal study was conducted to determine
tidal influence on the site.
From the RI, the following significant information was gained to characterize
the site and allow for an assessment of site specific threats. The unconfined
Columbia aquifer underlies the NCSS and is composed primarily of medium
grained sand with an average transmissivity of 60,000 gal/day/ft. and an
approximate saturated thickness of 23.5 feet. The groundwater flow of this
aquifer varies from the north and south sections of the site. In the northern
section, the groundwater flows northerly at a rate of 1.0 ft/day, while in the
southwestern section, the groundwater flows westerly towards the marsh at' a
rate of 0.5 ft/day. (See Figure 2) There is no tidal influence on the
groundwater in the study area.
Three distinct stratigraphic units are present a.s defined from the drilling
program. These units are a surficial layer consisting of a variable sequence
of clay, silty clay and silty sand; an intermediate layer (1. e. I Columbia
aquifer) consisting of medium grained sand; and a very dense, stiff clay layer
at an average depth of 30 feet which designated the top of the underlying
Potomac Formation. (See Figure 3)
The dense clay layer of the Potomac Formation encountered at a minimum of 5
feet in each newly installed well is considered continuous ac[oss the site.
The average vertical permeability of this clay is 2.87 x 10- cm/sec which
reflects an impermeable nature. The impermeable nature of this layer serves to
isolate the Columbia aquifer from the underlying Upper Potomac aquifer and
precludes aquifer interconnection. This impermeability is further
substantiated by: (1) the 1986 pump test data for the Potomac aquifer which
demonstrated a confined response to pumping; (2) the calculation of storage
coefficient of 0.00011, which was indicative of a confined system; and (3) the
depth to water measurements obtained in the pumping well of the Potomac which
indicated its potentiometric surface extends approximately 15 feet above its
confining layer. All of these characteristics demonstrate artesian conditions
, supporting the clay continuity throughout the site.
In the RI, the three media pathways of groundwater, soils, and the surface
water and sediments of the wetlands were investigated for the source and
extent and magnitude of contamination at the site.
In the groundwater sampling of the Columbia aquifer, three major Target
Compound List (TCL) compounds were reported and and their maximums are as
follows:
Comt>ound
Concentration
Tris
TCE
1,2-Dichloroethene
110,000 ug/l
120 ug/l
11 ug/l
Of these, tris and trichloroethe:-.e (TCE) were the most commonly identified
compounds. 1,2 -dichloroethene - detected in only tWo wells and considered
to be a COIIlI!:o:1'i~gradation '.ct of TCE. Detectable and quantifiable
concentration 0: ~;. rangi~; ~7, ~ to 110,OCO ug/l were identified in 7
-------
J 100601 06
Tr l' lorT1,F-r=13 a=ton=t:t=fJ~.t=tJ.... - --~ :a.a:aEl--~ ConraN T'acksl!:l~
Water Table Contour Map, Columbia Aquifer
30 March 1988
New Castle Spill Site
's:1
....
OQ
~
'1
IV
N
'"
50
I
o
50
100
LEGEND
. Observation Well (1979, 1980)
. Monitoring Well (1988)
Ii] 6" Production Well (1988)
1.29 Water Table Elevation (In 'eet, MSl)
- ,., Water Table Contour (In 'eet, MSL)
--
-------
31008'1
31003
.....,
: - --
40
60 -
-
, . ..
80 ..
100
sw
-
....
~
u.
~
Q)
u
cu
1:
:1
U)
1:]
c
j
::
o
Q)
m
L:.
...
Q.
Q)
o
120
140
160
180
Site-Specific Cross Section
New Castle Spill Site
";)
A1
m
AI
:t
Q
...
a
c::
'"t]
NE
Producllon Well No. 11
(Cd52-27)
Clay """"
o
Pump Iiouse
(Cd52-14)
20-
~;}~::
-te
",',',', ,
-'"0°0°,.
'-
"
-
'sj
t-'.
-
,-
-
Clay
-
.
..
d
Clay~and. and Gravel
- g - g
..
o
-
-0-
-
---
..
"
.
-~
..
<)
-
- -:--
'-
.
-:-
Sandy Clay =--
Confining Unit
--
-,
-
Clay
i::i.i .
i!i;:;::
~~[i~~~;~~j!IIIII.~'I',,~'~'I!.'~".;I'i~~I:III:~['I;'Jil!!!!I:ii!~r~~:~:~~;!!:~~!iii:iiiii!!0!:ii!':![~i!i!:i~i:ii!;::l::iiiifiii!i!wiiiiii:~i!:iii
;:::a
;.Upper ~olomac {<{
~:~:~::::::~9t.'!~,~2:2;;:2
--
-
Clay
- -
c::::: . -
-........
Sandy Clay "0 Claye~ Sand
Scale In Fee.
r I
o 20
~
"""
I
I
I
I
40
j
80
"
No Vertical Exa!J!Jcralion
--~
POlonliornelrie Swlaeo
wilhin Uppor Polornac Aquiler
{March-April 19BH)
-------
3100601
Concentration of Tris(2-Chloropropyl) Phosphate
in the 08 Series Wells (~Lg/l), 18 April 1988
. New Caslle Spill Site
1.:a::e ~a=t=t;aaa ~a~----,_.........-~~~.....Conrall TracbBf - ~~
c:c
~,
50
o
50
Scalo In foot
-.b~~!!EEEI~~-"----",,, ""--1M
80.0.22 . 80.8.2' Y
. 14600 0.0.16
J. to . 00 t.... 5' 4
B,ldGarage '88. "'. .2~ 110,000 - 6/~89 .
-~.'-' ~SIO'Y\. ""-
0.0.25 Av"'5 Dlod./ B,lck & COllcrel. ~
66.6 ) NCDW&~ \ V ~ Block Building ./
\fUlrallon rtalJ/ 80.0.82'60 "'''\ //
VO.O.7. \.. \../
A 0. . "0.8. 9 '- ./
~ ..a 8 A
NO 8 ~.v
0.0. 2" ,t-- . 0.8. ~ . q'\
'\. .0.0. '0 ~
O /,r, ,\80.0.3 0.0.5 119 ~..~Q
. O. . 1 ~ '\ NO 8 Y ,p
/NO" " ~/ '. ~~..
. '\ 8 0.0. 4 ~ ~
/ Casll.ford V\. ~-\~~
'> ,,~0.0. 1.
, . ... ~ '\ . NO
. 0.0.30 , . (> ~ ~~
~~
100
I
~.
~
OQ
t:
'1
(1)
+
EXPLANATION
-- Chain link Fenco
........-- ~ fence Gato .
. Observation Well (1979, 1980)
, 19 Concentration 01
Trls (2-Chloropropyl) Phosphate
In tho Water Table Aquller (JIg/I)
NO None Detected
(Blank Indicates ..
"It sampled)
-------
of 17 wells sampled. The distribution of tris in the Columbia aquifer was
consistent with the spill source area, and reflected a reduced mobility by its
occurrence primarily in the upper 10- feet of the aquifer.(See Figure 4) TCE
was detected in 8 of 17 wells sampled, ranged from 1 to 120 ug/l. The highest
concentration of TCE in groundwater occurred in wells located upgradient of
the spill source area, indicating a source upgradient from the site.
In the subsurface sampling, four major TCL compounds were reported and their
maximum concentrations are as follows:
Compound
Concentration
Depth
Tris
Fluoranthene
Phenanthrene
Benzo(b)fluoranthene
11. 8 mg!kg
3 . 6 mg/kg
4.4 mg!kg
2.5 mg!kg
2-4 ft
2-4 ft
2-4 ft
2-4 ft
Of these compounds, tris was identified as the contaminant of concern as it
was detacted in 9 of 15 soil samples in the highest concentrations. The higher
tris concentrations were found in the soils of the recognized spill source
area. These levels, however, do not represent levels which threaten human
health and the environment and are no longer considered a source of
contamination. TCE was not detected in any soil samples. Therefore, it can
. be concluded that the presence of TCE in the groundwater originates from an
up-gradient and off-site source and cannot be attributed to the' New Castle
Spill Site.
In the wetlands investigat.ion, two rounds of surface water and sediment
sampling occurred with the second round including TCE. The first round in
March detected concentrations of tris in the surface water ranging from none
detected to 42 ug/l. The highest concentration being detected at the sampling
location closest to the site. The second round in November detected tris.
levels in the surface water ranging from 1.2 to 5.5 ug/l reflecting an order
of magnitude lower than the original sampling in March. There was no TCE
detected in any of the surface water samples. The sediment sampling in March
detected no level of tris in all of the six sampling locations. In the second
round of sediment sampling in November, tris levels were detected at 402 and
300 ug!kg at two locations slightly away from the site. In addition, TCE was
detected at this time at an estimated value of 3 ug!kg at the sampling
location closest to the site. A wetlands delineation and habitat assessment
identified emergent and forested wetlands supporting a diverse flora and fauna
unaffected by the New Castle Spill Site. The tidal study indicated no tidal
influence exists at the site.
The conclusions from these sampling studies are; (1) The source of tris
contamination no longer exists at the site; (2) Tris contamination exists in
the Columbia aquifer; (3) There is no tris contamination in the Potomac
aquifer; (4) The source of TCE contamination has not identified but is
indicated as an upgradient source from its detection in well~ located
upgradient from the spill source area; (5) The contaminant levels in the
wetlands are well below Ambient Yater Quality Standards and (6) The tris
contamination has .no adverse impact on the environment as indicated by the
habitat assessment.
CU:T:~'-' and future exposure pathways were also identified from the RI and
inc; (l) current and future exposure to groundwater from use as potable
wa~. -:"1.:.', (2) current and future exposure to surface water from incidental
9
-------
EXPOSURE PATHWAYS FOR
NEW CASTlE SPill SITE
---- Releel. Expolur. Expolure
Trlnlporl Source Selecled 'or
°1 '.~ f 10 Uedle "echenhm Point Roule An.I"111
.;....1, Air Contamlnaled loil Votallllzallon On-811e or OII.llIe Inhalallon No . "e cove,ed by cemont aI/or
dxlillng mejo,ily 0/ 0'00
Fugiliv. DU81 On. III. or OII-I.e Inhalallon No . Ille cOl/e,ed by cemenl ol/er
mejorily 0/ area
Conlamlnaled lurlace waler Vola.Ull8l1on On '111e or OIl-III. Inhalallon No - T ri... nol I/ololila, oIher Indlcalorl
prese/ll In low concenl'lIllonl
Surt- Walor Contaminated groundwater Ground Waler Dlscharg. AdJacent marshland Dermal Conlect Vel - Marah Is neer resldenllal .,ea H
/!J
Surface Runof' Adjacent Marlhland Dermal Contact Vel - P~ed 0'00 near tredl, runs 011 0-
Ponded walor t-"
to marsh a, eo /1)
t-"
Soll/Sedlm.nt I Conlamlnated ground water Groundwater TranlpGf1, AdJacent Marlhland Dermal Contact Y.. . Marsh .0111. expaNd In dry weather Include.
AdlorptJon Inc/clllntal ingestion
t-' PICA Behavtor
0 No- Behavtor no/ Ukely
Spill Adlorpllon Oo-SlIe Dermal Conleet No . Sile cove,ed by cemont ol/ar maJorhy 0/ .rea
Hypothetlcel Ground Wat., Conlamlnated loll l.achlng, Transport Locaf ResIdence Dermal contact Ve8 . FuILlle use 0/ Columbia aquller
Future UI.
leaching, Transport local Residence Iooellioo Vel - Fulure use 0/ Columbia aqullor
leaching, Transport, local Re6ldonce Inhalallon VOl - Future use 0/ Columbia aquilor
Volallllzalion
"alles represent. change In lable
ROl/lsod ml/89
-------
ingestion and dermal contact, and (3) current and future exposure to soils
from ingestion and dermal contact. (See Table 1)
VI.
SUMMARY OF
SITE RISKS
In conjunction with the Remedial Investigation, an Endangerment Assessment
(EA) was conducted to evaluate the risks that compounds detected at the site
posed to human health and the environment. This assessment consisted of four
evaluations: identification of indicator compounds, which are used to
represent the potential risks posed by carcinogenic and noncarcinogenic
compounds at the site; an exposure assessment which includes the calculations
of doses to potentially exposed human and/or non-human populations, a toxicity
evaluation of the potential carcinogenic and noncarcinogenic effects of site
indicator compounds; and characterization of the risks to human populations
and/or the environment. -
In the selection of indicator chemicals, three mediums were considered, the
so il, the groundwater and the surface water. All three mediums were
identified as the mediums of concern by examining the levels of contaminants
present and the exposure pathways. The indicator compounds identified for the
site with mediums of concern are tris (2-chloropropyl) phosphate (soil,surface
water and groundwater), trichloroethene (TCE) (groundwater), and trans 1-2
dichloroethene (groundwater). The maximum concentrations on which the risk
assessment was conducted are as follows: -
Compound
Groundwater
Surface ~ater
Soil
trans-l,2-dichloroethene
Trichloroetpene
Tris
.01lmg/1
0.12mg/1
110.0mg/l
.042mg/1
11. 74mgjkg
In the exposure assessment the fate and transport of the indicator
compounds were evaluated, the exposure scenarios were established to determine
possible exposure to potentially affected populations and the doses and
resultant intakes were calculated. The physical properties and the relative
importance of processes influencing the fate and transport of the indicator
compounds are included on Table 2. In addition, the half-life of tris of
roughly 300 days was taken into consideration in the assessment. This half-
life value is based on the time period (1983-1988) that it took for tris to
degrade from 10,100 ppm to 110 ppm and comparison to DDT, a similar aqueous
structure.
Exposure scenarios established for the environmental media are as follows:
Medium
Air
Surface ~ater
Groundwater*
Exposure Route
None
Dermal Contact -
Dermal Contact while Bathing
Ingestion of Drinking ~ater
Inhalation while Bathing
* Evaluated only as a hypothetical scenario
The potentially affected populations consis: of the adult ar.d c~ildren livir.g
in the residential area to "the west of the sit:," - Subchronic ~ -:hror.ic daily
intakes for the actual and hypo=:,etical sc:::~-.-- - - -.; were c,,~ -d for these
-------
Table
2
RELATIVE ,"'ORTANCE OF P.OCUS£S INFI.UENCING FATE
OF TME INDICATOR COMPOUNDS FOR THE HE" CASTI.£ SPILL 511£
CC~"QUIIO soa,-r'ON VoU TlllZA TlCH "OCEGjUOA TIOH "HaTOlYSIS HYOaOl YSI S !IOACCtJnul). T ION OliO" TlCH
Tnc.~lonMlII- NO YES Y!S Ho YES Ho UHClL\R
Inns-I,2-otcnlOl'1leUI8M NO Y!S NO NO YES Ho UHCWR
In s(2-<~lore~IIOIIaSO'MIt. Y!S NO UHClUR UHClua NO NO UIIClE,IR
REF'ER£HC[s;
'ULLS. .. ".. ET AL. 1M2
CALLAHAH, 1'\.4. ET AL.. 1979
PfjYSlCAL PROPEimE5 OF THE INDICATOR CQUPClUNDS
F()R THE HEW c:.t.s'TU SPILL SITE
trans-' .2. T nC1lIoro. ttll12,Cl'lloro
PROPERTY Oictllo~m."e .... oraovtlollQsollare
a.te::L.ECULAA WEIGHT.; i.Ue.O 1 1.31£.02 328.00
ME!..TING PCtNT. 'C .1.30e.01
SCIl:NG POIHT. 'C &.OOE .01 8.70e.01
CENSITY.~ 1 .28E .00 1.48E.00 1.29
FlJ.SH POINT. 'C 3.90E .01 218.00
PARTmON coemc:el'{T'
WATE;:! S0UJ8IUTY. mgllI25"C) &.30E.Q.4 1.10E.03 0.11 WI ~. or 1100 mgIl
CiC':' »a. 'NA rc:t J
-------
populations and have been used to assess the carcinogenic risk and acute and
chronic effects from the exposures.
The toxicity evaluation establishes a data base against which exposure point
intakes can be compared during the risk characterization. It identifies
potential carcinogens and their cancer potency factors (CPFs) as well as
reference doses for noncarcinogens. CPFs have been developed by EPA's
Carcinogenic Assessment Group for estimating excess lifetime cancer risks
associated with exposure to potentiallY carcinogenic chemicals. CPFs, which
are expressed in units of (mgjkg-day)- , are multiplied by an estimated intake
of a potential carcinogen, in mgjkg-day, to provide an upper bound estimate of
the lifetime excess cancer risk associated with exposure at that intake level.
Reference doses (RfDs) have been developed by EPA to indicate the potential
for adverse health effects from exposure to chemical exhibiting
noncarcinogenic effects. RfDs, which are expressed in units of mgjkg-day, are
estimates of lifetime daily exposure levels for humans, including sensitive
individuals. Estimated intakes of chemicals from the environmental media can
be compared to the RfDs. .
The risk characterization includes comparisons between estimated daily intakes
and Acceptable Daily Intake (ADI) or reference doses (RfDs) for
noncarcinogenic compounds and estimates of excess cancer risk for exposure to
carcinogenic compounds. The comparison of estimated daily intakes of
contaminants to reference doses (RfDs), or levels established below the dose
at which effect are expect.ed to occur results in a 'Hazard Index (HI). The
acceptable risk range adopted by EPA for the HI is 1.0. The excess lifetime
cancer risk is the incremental increase in the probability of developing a
cancer from exposure to contaminants at the s~te. The acceptable excess
cancer risk range adopted by EPA is 10-4 to 10- .
In addition to the human risk assessment, an environmental assessment was
conducted which identified potential dnvironmental pathways and receptors as
shown on Table 3. This assessment consisted of: (1) comparing wetlands
sampling results to Ambient Water Quality Criteria and toxicity values; (2) a
habitat assessment; and (3) a macroinvertebrae survey.
a.
Risks from Current Exposure to Groundwater as a Potable Vater Supply
Currently, there is no exposure to the groundwater from the Columbia aquifer
as a potable water supply. All supplies are being obtained from the Potomac
aquifer. Therefore, the HI does not exceed the recommended value of less than
one and the lifetime cancer risk is approximated as zero. (See Table 4)
b.
Risks from Future Exposure to Groundwater as a Potable Vater Supply
If in the future, the groundwater of the Columbia aquifer should be used as a
potable water supply, populations would be exposed to risks from ingestion,
inhalation and dermal contact. The noncarcinogenic risk from this ext~sure or
. +1
the HI, calculated for the upper bound worst case would be 6.68 x 10 , which
exceeds the recommended value of less than one. This exceedance can be
contributed solely to the presence of tris in the groundwater and not the
other indicator compounds. The lifetime weighted carcinogenic risk for t~ts
future use calculated for upper bound worst case esttmate would be 1 .x 10 ,
which is within the EPA's acceptable range of 1 x 10- to 1 x 10 -7
(See Table 4).
13
-------
POTENTIAL ENVIRONMENTAL EXPOSURE PATHWAYS
NEW CASTLE SPILL SITE
MEDIUM
Macrolnvertebrae
Game Fish
Game Birds
RELEASE
SOURCE MECHANISM
Contaminated Leaching and
Surface Waler Transport
and Sediments
Dloconcent ration
Macrolnvertebrae Dloconcent rat Ion
Macrolnvertebrae Bloconcenl ration
Fish
EXPOSURE
POINT
Adjacent
Marshland
\larslilands
Marshlands
QUALITATIVE
EXPOSURE POTENTIAL AS
ROUTE POPULATION PATHWAY •«
Ingestlon Dotlomfcedcrs - fish
Game Fish
Fish-Cat Ing Birds *
Mammals (muskrats)
Ingest Ion Humans
ingesllon Humans
Low
Low
Low
Low
Low
Low
H
cr
i—'
n
•Includes wading birds, ducks, herons, hawks
potential to blomagnlfy In the food chain because of the low bloconcentratlon factors for these compounds
BCF. L/kg (US EPA. 1986)
trans-1.2-Dlchloroethene
Trlchloroethene
trls-(2-Chloropropyl)phosphate
1.6
1O.6
2.7*»»
•Based on trts;2.3-Dibromopropyl)phosphate
-------
Table
4
SUMMARY OF CALCULATED CARCINOGENIC RISKS
AND NONCARCINOGENIC HAZARD INDICES FOR
THE NEW CASTLE SPill SITE
PR£S£M". £XISTlNG SCENARIO. U.S. EPA'S
Upper Bound Upper Bound RECOMMENDED
Reasonable Case Worst Case GUIDELINE
CARCINOGENIC RISK = OE+OO = OE+OO 1 E-04 to 1 E-07
-.
NONCARCINOGENIC
HAZARD INDEX 5ubchronic 1.45E-05 1.45E-05 1
Chronic 3.76E-06 1.45E-04 1
HYPOTH£TlCAL FUTUR£.US£ SC£NARIO" U.S. EP A '5
Upper Bound Upper Bound RECOMMENDED
Reasonable Case Worst Case GUIDELINE
CARCINOGENIC RISK 3E-05 1 E-04 1 E-04 to 1 E~07
NONCARCINOGENIC
HAZARD INDEX Subchronic 6.71 E+OO 6.71 E+OO 1
Chronic 8.69E+00 6.68E+01 1
Bold value indicated an exceedance of U.S. EPA's risk/hazard guideline
Upper bound reasonable case represents the average concentration detected times either the
reference dose or carcinogenic potency factor
Upper bound worst case. represents the maximum concentration detected times eithar the
reference dose or carcinogenic potency factor
'" = approximate
. . Surface water and soiVsediment exposure
.. - Columbia aquifer ground water exposure
0520M 143
l~
-------
c. Risks from Current and Future Exposure to Surface Vater
The current and future exposure to the surface water receiving discharge from
the Columbia aquifer would be through dermal contact and incidental ingestion.
The risk presented by these exposures is within the acceptable range of less
than one for noncarcinogenic risk and 1 x 10 to 1 x 10 for carcinogenic
risks. (See Table 4)
d. Risks from Current and Future Exposure to the Soils
The current and future exposures to the soils would be through dermal contact
in the soils or sediments of the marsh and through ingestion, (i.e., PICA
Behavior). The risk presented by these exposures is within the acceptable
range of less than one for noncarcinogenic risks and 1 x 10" to 1 x 10 for
carcinogenic risks. (See Table 4)
e. Risks to the Environment from the Site Contaminants
The environmental assessment concluded that there is (1) no exceedance of
Ambient Water Quality Criteria by measured surface water concentrations, (2)
no exceedance of toxicity values for the most sensitive aquatic species
tested, (3) no adverse impact to the biotic communities of the wetlands
ecosystem from contaminants migrating off NCSS, and (4) low qualitative
potential for bioaccumulation of these compounds in the aquatic species and
less potential for biomagnification of the food chain to human populations.
(See Table 3)
VII. DOCUMENTATION OF SIGNIFICANT CHANGE
The Proposed Plan was released for public comment on August 22, 1989. The
Proposed Plan identified Alternative 2, limited action with monitoring of the
Columbia aquifer and the surface water and sediment of the adjacent wetlands,
as the preferred alternative. During the public comment period, the public
expressed concern over the possible contamination of the Potomac aquifer
through interconnection to the Columbia aquifer. DNREC and EPA have decided
to add a degree of protectiveness to the original preferred alternative by
including sampling of the Potomac aquifer on an annual basis for tris.
VIII. DESCRIPTION OF ALTERNATIVES
a. Remedial Alternatives Considered
A groundwater response action consisting of four alternatives was considered
for remediation of the site. The alternatives are as follows:
Alternative 1: No Action »
The no action alternative requires no remedial action. The existing site
conditions would remain unchanged. There would no institutional or monitoring
requirements on site or off site. A five year effectiveness review would be
conducted.
16
-------
Alternative ~ Limited Action with Groundwater and ~etlands Monitorin~ and the
~ of Institutional Controls
The limited action alternative consists of groundwater monitoring of the
Columbia and Potomac aquifers, and surface water and sediment monitoring of
the adj acent wetlands for tris. The groundwater monitoring of the Columbia
aquifer would be performed quarterly for tris until the TBC of 4.4 mg/l (See
Section IV.) is achieved. The ?:tomac aquifer would be monitored annually for.
the presence of tris as an ad(k.~ degree of protectiveness. The surface water
and sediments will be monitored for tris annually unless an anomaly is
de tected, at which time, monitoring would occur in the next quarter.
Additionally ,a TBC for the surface water and sediment of 100 ug/l and 1000
ugjkg respectively would act as a trigger value for requiring bioassay testing
and further evaluation. Institutional controls restricting well development
in the Columbia aquifer would also be implemented as part of this al~ernative.
A five year effectiveness. review would re-evaluate the effectiveness of this
remedy.
Alternative .l;.
Extraction ~ells. Granular Activated Carbon Treatment
and Dischar2e to Surface ~ater
This alternative requires pumping of groundwater from the Columbia aquifer
through extraction wells, treating the groundwater in a granular activated
carbon system and discharge to the' surface waters of the Narrow Dike Canal.
Monthly monitoring of the treatment system influent and effluent and
continuous flow measurements would be conducted. Implementation time
considered is 30 years or until the TBC for tris in the groundwater is
achieved. A five year effectiveness review would re - evaluate the
effectiveness of this remedy.
Alternative ~ Extraction ~ells. Dischar2e to Publicly Owned Treatment ~drks
(POTIT)
This alternative consists of pumping the groundwater from the Columbia aquifer
through extraction wells and discharging it to a sanitary sewer for treatment
at POTIT. Monthly monitoring and continuous flow measurement would be
conducted on the discharge. Implementation time considered is 30 years or
until the TBC for tris is achieved. A five year effectiveness review would
re-evaluate the effectiveness of this remedy.
b. Major ARARs and TBCs Utilized for the Remedial Alternatives
ARARs and TBCs being met/utilized for specific components of the alternatives
can be considered contaminant-specific, action-specific, or location-
specific. The ARARs and TBCs associated with the four previously described
alternatives are as follows:
Contaminant Specific ARARs and TBCs
Contaminant specific ARARs are not available for tris.
"to be cons idered" cri teria . to deve lop cleanup goals.
~ere there are no
For New Castle Spill
17
-------
Site, three TBCs were developed to address groundwater, surface water and
sediment cleanup goals. The TBCs are as follows:
- The TBC for tris in the groundwater was established at 4.4 mg/1 by U.S.
EPA. • This TBC is considered applicable to Alternative 3 and 4 where pump
and treat activities can achieve the TBC. It is not applicable to
Alternative 1 where no remedial action is performed. It can be waived
for Alternative 2 based on satisfying the following criteria: Equivalent
S tandard of Performance - the remedial action selected will attain a
standard of performance that is equivalent to that required under the
otherwise applicable, standard, requirement, criteria or limitation
through the use of another method or approach (CERCLA Section 121
- The TBC for tris in the surface water was established by the National
Oceanic and Atmospheric Administration (NOAA) at 100- ug/1 as a trigger
value to require bioassay testing and further evaluation if reached.
This TBC is applicable to Alternatives 2 and 3.
The TBC for tris in the sediments was established by NOAA at 1000 ug/kg
as a trigger value to require bioassay testing and further evaluation if
reached. This TBC is applicable to Alternatives 2 and 3.
Action Specific ARARs and TBCs
CERCLA Section 121 (e) exempts any response action conducted entirely on site
from having to obtain a Federal, State or local permit, where the action is
carried out in compliance with Section 121. The response action need only
comply with the substantive aspects of ARARs, not with the corresponding
administrative requirements. For any response actions off site, action -
specific ARARs must be met.
The Delaware River Basin Commission (ORBC) regulates surface water and
groundwater withdrawal and discharges within the Delaware River Basin.
The requirements of the DRBC are considered applicable to the activities
of Alternative 3 for the installation of an extraction well.
- The State of Delaware Regulations Gorernoring the Construction of
Monitoring Wells regulates the construction of extraction wells through
the use of permits. These regulations are applicable to Alternatives 3.
- The Natural Pollutant Discharge Elimination System (NPDES) implemented
under 40 CFR Part 122-125 has substantive requirements which must be
identified and complied with in order to discharge to surface water. A
NPDES permit is not required but the substantive requirements must be
met. These requirements are applicable to Alternative 3.
- The 40 CFR Part 403.5 requirements control the indirect discharge of
pollutants to a POTW. These requirements are applicable to Alternative 4.
- Local POTW requirements control the acceptance of a discharge for
treatment at the POTW. These requirements will be applicable for the
discharge from Alternative 4.
The Regulation of Non-Domestic Waste Water Discharge into the Public
Sewer System, Chapter 16, Article 8 of the New Castle County Court
18
-------
controls the discharge to a sanitary sewer.
considered applicable to Alternative 4.
These regulations would be
Location Soecific ~
CERCLA Section 121 (e) exempts any response action conducted entirely on site
from having to obtain a Federal, State or local permit, where the action is
carried out in compliance with Section 121. The response action need only
comply with the substant~ve aspects of ARARs, not with the corresponding
administrative requirements. For response actions o.ff site, location -
specific ARARs must be met. .
The Delaware Department of Natural Resources and Environmental Control
~etlands Regulations (Revised June 29, 1984) and the ~etlands Act (Title
7, Del. ~, Chapter 66) regulates any activities which may impact the
wetlands. These requirements would be applicable to Alternative 3 as its
activities could impact the wetlands.
The U.S. Army Corps of Engineers under the Clean Yater Act, Section 404
regulates permitting of activities in the wetlands. Alternative 3 would
require a U.S. Army Corps of Engineers permit. This ARAR is applicable
to Alternative 3 activities.
The 40 CFR Part 264.18 (b) regulates the design, construction,
maintenance and operation of a treatment facility within a 100 year
floodplain. Alternative 3 would require a treatment facility to be
constructed in the 100 year floodplain of the Delaware River. This ARAR
would be applicable to Alternative 3.
-Protection of Yetlands and Executive Order 11988, Floodplain Management
and requires agencies to avoid or minimize adverse impacts to wetlands
and floodplains, and to preserve and enhance .the natural values of
wetlands and floodplains. Alternative 3 activities would fall under this
applicable ARAR.
The Delaware Department of Natural Resource and Environmental Control
Regulations Governing the Use of Public Subaqueous Lands (revised July
30, 1985) and Subaqueous Lands (Chapter 72) regulates activities which
affect subaqueous lands. Alternative 3 would require a permit for
activities affecting subaqueous lands. This ARAR is applicable to
Alternative 3.
Approval from Conrail is needed for right of way for activities occurring
adj acent to the wetlands. This would be considereO an applicable ARAR
for Alternative 3.
Location Soecific TBCs
The U.S. EPA'S Groundwater Protection Strategy (GPS) is not a promulgated
regulation, and therefore is not a potential ARAR for a Superfund site.
However, the NCP lists the U.S. EPA's GPS among the other criteria,
standards,. and guidance "to be considered" in Superfund. For this.
reason, the U. S. EPA's GPS has been recognized as a TBC for the New
Castle Spill Site. Under the GPS, the aquifer at the site has been
classified as a Class II B. A TBC cr: tp. "ia for groundwater remediation
has been established a.~ 4.4 mg/l of . : by U.S. EPA. This TBC is
.~. :3
-------
considered applicable to Alternatives 2 I 3,4, as they all have either
monitoring controls and/or institutional controls. Alternative 1 cannot
meet this ARM.
IX. SUHMAllY OF COMPARATIVE ANALYSIS
OF ALTERNATIVES
a. Comparative Evaluation of Alternatives
In the following section, each of the four alternatives are comparatively
evaluated against the nine criteria established by the U. S. EPA for the
selection of the remedy. This evaluation will demonstrate the abilities of the
alternatives to protect human health and the environment, comply with state,
federal and local statutory requirements, be easy to implement, achieve long
and short-term effectiveness, reduce toxicity, mobility and volume and be
cost-effective.
~ Overall Protection
Overall protection is an assessment of the degree of protectiveness provided
by the alternatives to human health and the environment through their
elimination, reduction or control of the risks through treatment, engineering
or institutional controls. All of the alternatives can be considered
protective of human health and the environment with the exception of
Al ternative 1, which does not remove the risk or monitor the contaminants
migration. Alternative 3 and 4 would provide a greater degree of
protectiveness for potential groundwater user through immediate groundwater
recovery and treatment. Alternative 2 would not immediately eliminate the
hypothetical risk from the site but it exhibits protectiveness through
moni to ring of the groundwater, surface water and sediments, use of
institutional controls and five year effectiveness review.
L Comtlliance !.Q. ARARs and ~
Comparative analysis of comuliance with atltllicable Qt relevant and atltlropriate
reouirements (ARARs) of the four alternatives includes a review of state and
federal applicable or relevant and appropriate contaminant-specific, action-
specific, and location-specific requirements. This analysis also addresses
other concerns identified as "to be considered" (TBCs). TBCs are non-
promulgated advisories, criteria or guidance issued by the Federal or State
government that are not legally enforceable standards. The U.S. EPA and the
State may agree to follow the TBCs when there are no ARARs to address a
particular contaminant or situation such as in the case of tris (2-
chloropropyl) -phosphate at the New Castle Spill Site.
Alternative 1 is a no action alternative without monitoring or institutional
controls, so therefore, no action-specific, contaminant-specific or location-
specific ARARs apply. However, the TBCs of the U.S. EPA GPS and the TBCs for
groundwater, surface water and sediments would be considered applicable.
Alternative 1 would not meet these TBCs.
Alternative 2 is limited action with monitoring and institutional controls of
which~ there are no applicable action-specific, contaminant-specific or
location-specific ARARs. The TBCs of the GPS, and the TECs for groundwater,
surface water and sediments are applicable for this alternative. This
alternative meets the surface water and sediment TBCs ~'- - is unable to meet
the TBCs of the GPS and the groundwater". Pc~;~ver. it do.' :isfy the cri:eria
to invoke a waiver for t::.ese TBCs h..\ on th",".;i.ng principle:
20
-------
Alternative 2 can attain a standard of performance that is equivalent to that
required under the otherwise applicable standard, requirement, criteria, or
limitation, through use of another method or approach. (CERCLA Section 121
(d) (4)(D).)
Alternative 3 is the use of extraction wells, treacment with GAC and discharge
to surface water. For this alternative, there are numerous and significant
ARARs and TBCs as shown on Section VIIIb above. Although this alternative
should be able meet the ARARs and TBCs, the administrative and substantive
requirements for this alternative requires much more implementation than
Alternative 1, 2 or 4. Also this alternative could possibly impact the
wetlands.
Alternative 4 is the use of extraction wells, discharge to the sanitary sewer
and treacment works. This alternative meets the applicable ARARs and TBCs as
shown in Section VIIIb above. It requires only one state permit but also
requires permission to discharge to the local PON, which in the past has
expressed concern over Superfund site discharges.
1. ~ ~ Effectiveness
The long- term effectiveness criterion examines the extent and effectiveness
of controls that may be required to manage the risks posed by treatment
residuals and/or untreated wastes. All of the alternatives are expected to
achieve long- term effectiveness and permanence, either through pump and treat
or natural attenuation and the five year effectiveness review.
~ Reduction 2f Toxicitv. Mobility and Volume
Reduction of toxicity, mobility and volume refers to the amount of material to
be treated, the amount of hazardous materials that will be destroyed or
reduced, and the degree of. expected reduction. Only Alternative 3 provides
treacment which accomplishes an irreversible reduction in toxicity, mobility
and volume. Alternative 4 does remove the contaminant but the corresponding
reduction of toxicity depends on the treatment effectiveness of the PON.
Alternative land 2 will not actively afford a reduction in toxicity, mobility
and volume, except through natural attenuation processes. Alternative 2,
however, does not address the waste left onsite through its monitoring
activities of the gro1.:.Ildwater, sediments and soils, institutional controls,
and the five year effectiveness review.
2. Short- ~ Effectiveness
. .
The short-term effectiveness criterion examines the effectiveness of the
alternative to protect the health of the community and workers during remedial
actions activities, the potential for adverse impact to the environment from
the implementation of an alternative, the effectiveness of the available
mitigation measures in preventing or reducing the impacts and time until the
remedial response objectives are met. All of the four alternatives would be
considered protective of the community and workers. Only Alternative 3 could
have a slight impact on the wetlands and surface waters, because of the. need
to construct a discharge line through the wetlands. Alternative 3 and 4 may
have a shorter implementation time to that of Alternative land 2. This is
dependent on any difficul ties which may be encountered implementing
Alternatives 3 and 4.
21
-------
6. Imulementability
The evaluation of implementability considers Che technical and the
administrative feasilibity of the alternatives. All four alternatives are
considered technically feasible and do not preclude or hinder further remedial
actions. The effectiveness of the remedies would be monitored via periodical
groundwater monitoring. Alternative 2, 3 and 4 are expected to show high
system reliability . Alternative 1 is the easiest to implement as it is not a
remedial action. Alternative 2 provides ease of implementation as well as the
best degree of monitoring of all the alternatives and is more administratively
feasible than Alternatives 3 and 4. Alternatives 3 and 4 require numerous
permits and approvals which administratively make their implementation more
difficult.
li Costs
The estimated costs of each alternative is evaluated for capital costs and
operation and maintenance. Each estimate is provided in accuracy of plus 50%
to a minus 30% A present worth analysis is also conducted allowing the
alternatives to be compared on the basis of a single cost, which includes a 5%
discount rate over five years. The highest present worth costs alternative is
Alternative 4 at $1,642,000.00. The present worth costs for the other
alternatives are as follows: Alternative 1 - $0; Alternative 2 - $466,147.00;
Alternative 3 - $1,637,000.00.
8. State Acceptance
The State of Delaware accepts the selection of Alternative 2, monitoring of
the groundwater from the Columbia and Potomac aquifers and the adjacent
wetlands plus the use of institutional controls on the Columbia aquifer.
9. Community Acceptance •
The community acceptance addresses those features of the alternatives that the
community supports, those for which they have reservations and those for which
they strongly oppose. The community has indicated its acceptance of the
preferred alternative, Alternative 2 of limited action with monitoring. The
public comments on the site and the selection of the alternative are included
Lr\ the Responsiveness Summary of this document.
b. Summary of Comparative Analysis
Through the comparative evaluation of the alternatives, it has been determined
that Alternative 1 does not provide a sufficient level of protectiveness due
to its lack of monitoring and institutional controls. Therefore, it cannot be
considered as the preferred alternative.
Alternative 2 provides an adequate level of protectiveness through its
monitoring of groundwater and the surface waters and sediments of the adjacent
wetlands as the site currently poses no risk to human health and the
environment. It does not comply with the TBCs for the GPS and the
groundwater, but does satisfy criteria to invoke a waiver for the TBCs.
There is no remedial action which reduces toxicity, mobility and volume,
however natural attenuation processes will reduce all of these. The long term
and short-term effectiveness is handled easily through the control measures.
22
-------
Implementation of this alternative is easiest among all of the acceptable
alternatives. Its overall effectiveness is proportional to the costs making it
more cost-effective than the other alternatives.
Alternative 3 satisfies the criteria of protectiveness, short and long- term
effectiveness, reduction of toxicity, mobility and volume, and compliance with
ARARs. To the extent that off site activities may require permits and
approvals, implementation of this alternative may be more difficult, which
could also result in longer time for implementation. The remedial activities
could possibly disturb the wetlands during installation of the discharge
line. The cost at $1,637,000 is proportional to the activity but not as cost-,
effective as Alternative 2.
Alternative 4 also satisfies the criteria of protectiveness, reduction of
toxicity, mobility and volume, short and long- term effectiveness and
compliance with ARARs. Its implementation requires fewer approvals and permits
than Alternative 3 to the extent permits and approvals are required for off
site activities. In addition, approval to discharge to POTW may be difficult
to obtain as previous efforts have demonstrated. The cost is the highest of
all alternatives and is not justified by the overall effectiveness.
x.
THE SELECTED REMEDY
The remedy selected for the New Castle Spill site is limited action with
monitoring of the groundwater from the Columbia and Potomac aquifers,
monitoring of the surface waters and sediments of the adj acent wetlands and
institutional controls restricting the installation of wells in the Columbia
aquifer, in the vicinity of the site. This will be followed by a five year
effectiveness review to re-evaluate the effectiveness of this remedy. The
selection of this remedy is based on the following facts:
1. There are' no human receptors impacted by the site since the groundwater
from the Columbia aquifer is not currently being used as a potable water
supply.
2. The future use
water supply is
Potomac aquifer
of groundwater from the Columbia aquifer as a potable
unlikely due to the available established supply from the
and the historically poor water quality of the Columbia.
3. There are no environmental receptors adversely impacted by the site.
4. The half-life of tris can be assumed to be roughly 300 days based on the
time period. (1983-1988) that it took for tris to degrade from 10,100 ppm
to' 110 ppm and comparison to DDT, a similar aqueous structure. Using
this 300 day half-life, it will take approximately 4 years for the tris
in the Columbia aquifer to reach the TBC of 4.4 mg/l.
5. Tris contamination does not exist in the Potomac aquifer.
Using these five findings, it is obvious that the remedy of limited action is
the most cost-effective solution that provides adequate protection to human
health and the environment while effectively mitigating and minimizing the
threat from the site. This remedy also utilizes a permanent solution of
natural attenuation. which can be considered a treatment of the principal
th::8a:: to reduce --. iciey, mobility and volume of the contaminants on the'
si.~i': In addie:,: ~:.s remedy is already in place, requires no permits or
22
-------
DETAILED EVALUATION OF ALTERNATIVES
K>
•F-
Crilcilon
Sliorl-Teim EffectUeiieu
- Community Protection
- Worker Protection
- Environmental hnpncla
• Time (» Remediation
Long-Term EiYecllveneM
- Mainline of Remaining
Ulsk
- Adequacy of Controls
- Reliability of Controls
- Flve-Yenr Effectiveness
flevlcws
Reduction of Toxlclty,
Mobility, or Volume
- Amount of Hazardous
Materials Destroyed/
Treated
- Degree of Reduction In
Toxlclly. Mobility, or
Volume
- Irreveralhlltty of
Mcdiiclton
- Residuals Remaining
Alter Treatment
Alternative 1
No Action
Adequate
Not Applicable
None Expected
Not Known -
Expected to he
longer Hum (hat
for Alternatives 3
and 4
Acceptable, nfter
ground wnter
contamination
dissipation/
degradation
Not Applicable
Nut Appllciible
Needed
Little to None
Little to None
Not Applicable
Not Applicable
Alternative 2
Monitoring
.
Adequate
Adequate
None Expected
Not Knowu-
Lxpected to be
A Ycara
Acceptable.
after ground
water contam-
ination
dissipation/
degradation
Not Applicable
Not Applicable
Needed
Little to None
Through Natural
Attenuation
Through Natural
Attenuation
Not Applicable
Alternative H
Exhaclliin Wells;
Granular Activated Carbon;
Discharge 1'n Surface
Adequate
Adequate
Minor
(Wetlands
Disturbance)
Not Known-
(3O Years
Assumed fur
Gosling
Purposes)
*
Acceptable.
After Oroiiiid
Water Recovery
and Treatment
Not Applicable
Not Applicable
Needed
The Majorlly
of Tils
Dissolved In
(lie Ground
Water
Vliliially
Complete
Until Caihon
Column
rireaklhrntigli
Yes
No - Spent
Cat Imn Will
be Thermally
Reactivated
Allrmallvr 4
ICxIiiiclInn
Wells;
IMschingc
to I'OIW
Adequate
Adccptate
None Expected
Nut Known-
ClOYciiis
Assumed for
Costing
I'tnpoMCs)
Acceptable.
After Oroundwaler
liccovciy and
Ticalmcnt
Not Applicable
Nul Applicable
Needed
Little lo None
Yes for Mobility;
No lor Toxlclly and
Volume
(Iris nut considered
llliiilcniail.ilili:)
Yes. for
Mobility
Not Applicable;
Til a mil Consldcied
lllodcgiadiiblc
-------
DETAIL!::!) EVAJ.UATION OF AI.TlmNA""VE~
(eol~
Allcr"allvl~ <1
Allenlllllvc :I Ex II ;11:111111
Exl..II:1l1l1I Well:.; Wdh;
Allernllllvc I Allelllullve 2 Ollllllllllr Acllvilicil Cllllall"; IlIsl:hal,:c
Crllerloll No Aclloll Monllorlllg nl~elaorge To SlIrfuce III l'OIW
ImplemcatahUlty
- Technical Feasibility
- Ahlllly 10 Conslrucl/ Nol APpllcob!e Adequale Alle11llole AlleqllRle
Operote
- Technical Feaslhlllty
(Conl'd.)
- nellahlllly Nol APlllicable Adequale Adequale Adeqllale
- Ablllly 10 Undertnke Adequole Adequate Adequote AdeClllatc
Addilionallkmedial
Meosures
- Ablllly 10 Monllor Adequale (vlo Adequate Adequole AlIcllunle
Uellledy Effecllveness 6-year effecllve-
lIe5$ revIews) ....,
~
- Adllllnlsimlive Fensilalllly NOlie None Two Federnl ollll OIlC Si/llc I'erlllll 1:1
.....
. I'ennlt nellulrelllelils l1lree Slale nCllllhcd ~
PenulI!t UC11llheil IJI
N
IJI - J\l'llIovals I>Nm~C. EPA DNnEC. EPA Conroll, nunc. I>Nlmc:, EI'A. -
o
Apllroval Allprovul (}NUEC. I~I'A Wlllllhllllllil I'(YIW. 0
. AV/Illahlilly or Services AJiPloval New Coslle COli Illy =
Sewer Syslcm "
alllJ Mulerlals -
- OIT-Slle TSD COl'nelly Not Needed Nol Needed Ade11llalc at EXlledcl1 10 he
Prcsellt Allc11llaic
- Necessnry 'Eqlllplllcnt Not Needed Ade11llale Adequale Allc1lunlc .
nlllJ Slleclallsls
AvallabllUy or Services
all" Materials
- Avollnblllly of Ihe Nol Needed Adequale "'dequate "'llcII"mle
Techuology
- Al>lllIy 10 Olllnill Nol Needed. Adeqll~te Adequole AilclllIl1le
CompellUve Ulclfl
Cod
. Capllnl $0 $0 .116.000 $55.000
- O&M CO $25.000 $!H.OOO $!III.OOO
- I'resellt Worlh (llIcludes $0 ~466.147 $1.037.000 $1.ft't2.IUIO
5.Year Elfecllvenes'l
lIevle~1
Compliance Wltb AnARa Nol Apl'llcllhle WaIved l\
-------
additional time Co implement. Also, natural attenuation is expected to attain
an equivalent standard of performance to that of the other alternatives,
therefore invoking a waiver for TBCs and ARARs.
The limited action remedy addresses the groundwater contamination identified
by the RI as the sole operable unit of concern at the site. The groundwater
contamination was identified as the presence of tris in the shallow Columbia
aquifer. Tris is a semi-volatile compound with little known data available on
its human and environmental toxicity. An Acceptable Daily Intake (ADI) of
health based drinking water level or "to be considered" (TBC) criteria for
groundwater of 4.4 mg/1 tris. This TBC has been chosen as the cleanup goal for
groundwater at this site. In addition to the contamination identified in the
groundwater, the aquifer has been classified as a Class II B aquifer, a
potential source of drinking water.
The limited action with monitoring is a groundwater response action that
First, it monitors the groundwater in the Columbia aquifer for tris on a
quarterly basis until the TBC of 4.4 mg/1 is achieved. The quarterly results
will be reviewed and allow for a re-evaluation should an anomaly occur.
Second, it monitors the groundwater of the Potomac aquifer on an annual basis
for tris. Third, it monitors the surface water of the adjacent wetlands for
tris on an annual basis. Any anomaly in these results would require re-
sampling in the following quarter plus a trigger value of 100 ug/1 of tris has
been established which would require bioassay testing and further evaluation
if reached. Fourth, it monitors the sediments of the adjacent wetlands for
tris on an annual basis. Any anomaly in these results would require re-
sampling in the following quarter plus a trigger value of 1000 ug/kg of tris
has been established which would require bioassay testing and further
evaluation if reached. Fifth, institutional controls will be implemented by
the State of Delaware which will preclude any future installation of water
wells for domestic or commercial use in the Columbia aquifer in the vicinity
of the site. Sixth, a five year effectiveness review will be conducted which
re-evaluates the site conditions to determine the effectiveness of the remedy.
Should the remedy not achieve the anticipated results, another remedy may be
selected.
XI. Statutory Determinations
To choose a remedy for a site, the statutory requirements of Section 121 of
CERCLA must be satisfied. The requirements are that the remedy selected by
the lead agency, in consultation with the support agency, must:
1. Be protective of human health and the environment;
2. Attain ARARs (or provide ground for invoking a waiver);
3. Be cost-effective;
4. Utilize permanent solutions and alternative technologies or resource
recovery technologies to the maximum extent practicable and;
5. Address whether the preference for treatment that reduces toxicity,
mobility and volume as a principal element is satisfied, or provide an
explanation in the Record of Decision as why it is not satisfied
26
-------
Limited action of monitoring satisfies the statutory requirements of Section
121 of CERCLA through its six well designed features as demonstrated in the
following discussions on statutory requirements.
Protectiveness 2! Human Health and ~ Environment
New Castle Spill Site poses no current risks to human health and the
environment. The calculations for the lifetime cancer risks are approximated
as zero and the Hazard Index does not exceed the recommended value. of less
than one. The only risk calculated for this site which exceeded EPA's
recommended values is the hypotheticalfu~ure use scenario for
noncarcinogenic risks. The upper bound worst case hazard index for
hypothetical future use is 6.68 x 10+1 In addition, the site has
demonstrated that through natural attenuation processes, the cleanup is on-
going. However, to provide adequate protection to human health and the.
environment, several safeguards were added to monitor the mitigation and
possible migration of the contaminants and prevent any future use of the
groundwater of the Columbia aquifer. The first safeguard is monitoring of the
groundwater from the Columbia and Potomac aquifers and the surface waters and
sediments of the adjacent wetlands for tris. The monitoring will assess the
degradation of contaminants in the Columbia, assure that no contamination is
occurring in the Potomac and allow re-evaluation of the remedy should the
degradation does not process as anticipated. In addition, trigger values were
established for the surface waters and sediment which would require bioassay
testing and further evaluation should these values be exceeded. The second
safeguard is the use of institutional controls restricting future installation
of wells in the Columbia aquifer in the vicinity of the site. This would
prohibit future use of the Columbia in this area. The third safeguard is the
five year effectiveness review where site conditions are re-evaluated after
five years to determine the effectiveness of the remediation. Through these
three safeguards and the fact that the remedy requires no remedial activity
and therefore will not pose a short-term risk, or a cross media impact, the
remedy will provide a more than adequate protection to human health and the
environment.
Attainment of Applicable Qr Relevant and Appropriate Reouirements
There are no contaminant specific ARARs for tris, nor action or location
specific ARARs for the limited action with monitoring. In lieu of ARARs for
tris, TBCs values have been established for groundwater, surface water and
sediments as protective levels of cleanup for the site. These TBCs must be
considered and used as appropriate, when necessary to ensure protectiveness.
In addition, the U.S. EPA Groundwater Protection Strategy must be considered
as a TBC for the site. A list and brief description of the TBCs associated
with the preferred alternative are discussed below in greater detail.
o
The TBC for groundwater
gr~undwater cleanup goal
from the ADI for tris of
of 4.4 mg/l of tris has been established. as a
for remedial activities. This was calculated
.125 mg/kg/day.
o
The TBC for surface water'is the c~rrent level of 42 ug/l of tris with a
trigger value established at lOC ug/l which would require bioassay
testing and further evaluation.
-------
o The TBC for sediments is the current level of 402 ug/kg of tris with a
trigger value established at 1000 ug/kg or 1 ppm which would require
additional bioassay testing and further evaluation.
o The U.S. EPA Groundwater Protection Strategy classified the Columbia
aquifer as a Class II B, a potential source of potable drinking water.
Limited action with monitoring does not provide a remedial activity which
attains these TBCs. It does, however, qualify to invoke a waiver, pursuant to
CERCLA Section 121 (d)(4), for these TBCs for the following reasons. Compared
to the other alternatives, it provides an equivalent standard of performance
through natural attenuation processes. It provides a degree of protectiveness
equal to or greater than the other alternatives through its extensive
monitoring activities and use of institutional controls even though the site
currently poses no risks to human health and the environment. The level of
performance to be achieved by natural attenuation is comparable to pump and
treat alternatives. The time to achieve beneficial results is equal to the
other alternatives based on the half life estimate of 4 years to achieve the
TBCs. For these reasons, a waiver can be invoked for the TBCs.
Cost-Effectiveness
The limited action of monitoring has demonstrated that it protects human
health and the environment and qualifies to invoke a waiver for the TBCs for
the site. It has been shown that the remedy is anticipated to be completed in
4 years for the sum of $466,147. Therefore, remediation of the site could be
complete by November 1992. To implement the alternatives involving pump and
treat methods would take an additional one million dollars and significantly
longer time to begin implementation (i.e., the spring of 1990). By this time,
the limited action remedy would be half completed. By viewing all of these
factors, it is obvious that the selected remedy affords overall effectiveness
proportional to its costs so that the remedy represents a reasonable value
for the money and is more cost-effective than Alternatives 3 and 4.
Utilization of Permanent Solutions and Alternative Technologies
The limited action with monitoring is a permanent solution to the site
contamination utilizing the natural attenuation processes. It provides a
greater degree of protectiveness than the other alternatives since it not only
monitors the groundwater but also monitors the surface waters and sediments of
the adjacent wetlands and restricts future use of the Columbia aquifer
through institutional controls. In addition, it has been approximated that the
cleanup will be completed by November 1992. Alternatives 3 and 4 would have
hardly begun by this time. This remedy also affords overall effectiveness
proportional to its costs and allows for remediation of the site to be
achieved for one million dollars less than the other alternatives. In short
and long- term effectiveness, the lack of remedial action and its anticipated
cleanup date of November 1992 offers advantages the other alternatives cannot
provide. The toxicity, mobility and volume will be reduced through natural
attenuation which can be considered a treatment of the principal element and
therefore satisfies a statutory preference. Both the DNREC and the U.S. EPA
support this selection and feel the community will support a remedy which can
achieve protectiveness and be cost-effective.
23
-------
Preference !2x Treatment ~ A PrinciDal Element
The hypothetical principal threat at this site is contamination in the
groundwater of the Columbia aquifer. There is no longer a source of
contamination. Natural attenuation is a process where the contaminants in the
groundwater dissipate, disperse or degrade over a period of time. This can be
considered a permanent solution to a problem which reduces the toxicity,
mobility and volume of the contaminants even a physical treat:ment is not
occurring. Limited action with monitoring allows a permanent solution to
occur naturally.
29
-------
C. RESPONSIVENESS SUMMARY
New Castle Spill Site
New Castle, Delaware
-------
NEV CASTLE SPIU. SITE
RESPONSIVENESS SUMMARY
OVERVIEio1
The New Castle Spill Site entered into a public comment period on August 22,
1989 with the release of the Proposed Plan for the selection of the remedy
for the site. In the Proposed Plan, the DNREC and the U.S. EPA recommended
the selection of the limited action with monitoring alternative. This
alternative would monitor the Columbia aquifer for tris on a quarterly basis
and the Potomac aquifer and the surface water and sediments of the adjacent
wetlands for tris on an annual basis. Trigger values would also be
established for the surface water and sediments which would require further
evaluation and bioassay testing if reached. In addition, the alternative would
place institutional controls on the Columbia aquifer, precluding any future
installation of wells in the Columbia aquifer in the vicinity of the site. A
five year effectiveness review would re-evaluate the effectiveness of this
remedy.
Public opinion on the site was received from two avenues, community interviews
and comments received during the Public Meeting. In the community interviews,
the general public expressed little concern about the site. In the public
meeting, two contingencies expressed comments and are as follows:
o Two residents in the area of the site expressed concern over the number of
cancer deaths in their neighborhood and questioned whether the deaths could be
related to the spill at io1itco. They' were 'also disturbed that this spill had
occurred and they had not been informed.
o Members of Board of New Castle Board of Water and Light expressed
concurrence with the selection of the limited action alternative for the site
but felt that the alternative should also include the sampling of the Potomac
aquifer and institutional controls on the Potomac aquifer. It is the opinion
of this group and its consultants that an aquifer interconnection exists in
the area of the site and these additions to the alternative would allow us to
monitor for any possible contamination which may occur in the Potomac aquifer.
BACKGROUND ON COMMUNITY INVOLVEMENT
The New Castle Board of Water and Light (NCBWL) formerly operated a water
treatment plant on the property adjacent to the Witco facility. This
treatment plant serviced the water supply from the shallow gallery water
system and Potomac well located onsite. In 1977, a spill occurred at the
io1itco facility thereby contaminating the property of NCBWL. As result of this
spill, the shallow gallery system was found to be contaminated with tris and
subsequently removed from service. Because of the contamination, NCBWL
decided to shut down production in the Potomac well for fear of pulling
contamination down into the Potomac through pumping. It was their opinion
that an interconnection exists between the Columbia and Potomac in the area of
t;:.,:: site. A lawsuit is pending by the NCBWL against'the Witco Corporation for
:es to their property and source of water supply as result of the spill.
1
-------
!he community has had little involvement in. the past with the site. !his may
be attributed to their lack of knowledge of the spill and/or general community
apathy; Community interviews, presentations and newspaper articles have been
conducted to increase their awareness and knowledge of the site. !he public
has continued to appear disinterested on the site. !his is clearlyl
represented by the number of participants at the Public Meeting outside of the
NCBw~ contingency.
SUMMARY OF COMMENTS RECEIVED ~ !HE PUBLIC COMMENT PERIOD
Several written comments were received and presented for the record at the
Public Meeting on September 6, 1989. In addition, several comments were
received verbally at the meeting. !he transcript of this meeting is contained
in the Administrative Record in the Repository in the DNREC Building at 715
Grantham Lane, New Castle, DE. !he comments from this meeting together with
the responses are presented below:
1. Comment: What is the likely scenario with regard to the TCE on the site?
What has been done, what will be done and how long will it take?
Response: !he TCE detected in the site has been determined to be
originating from a site up gradient from the site. DNREC has recently
completed a Site Inspection on the up gradient site to determine if this the
origin of the TCE. !he data from this Site Inspection will be evaluated
through the Hazard Ranking System and receive a Hazard Ranking Score. If the
score exceeds 27.5 [sic], the site will be proposed for the National
Priorities List as a Superfund site. !he site would then go through the same
process as this site, meaning a Remedial Investigation and Feasibility Study
and eventually remediation. !he length of time it will take to go through
this process is unknown. .
2. Comment: What information do you have with regard to the degradation of
tris? How did you come up with the fact that it is going to eliminate itself
after four years?
Response: !he tris was compared to DDT for aqueous stability due to their
similar structures. DDT has a half-life in water in the order of 300 days.
For the tris to degrade from the 1983 sampling level of 10,100 ppm to the
1988 ~ampling level of 110 ppm would take 7 half-lives or roughly 2100 days
(for DDT).' !his roughly the time interval between the two samplings.
!herefore, using this comparison it can be assumed that for the tris to
degrade to the cleanup level of 4.4 ppm, it will take approximately four
years.
3. Comment: What will happen after five year if in doing the Effectiveness
Review it is determined that the degradation has not reached the target level
as anticipated?
Response: If the degradation is revealed in the Five Year Effectiveness
Review to have not occurred as anticipated, the site would be re-evaluated
for possible selection of a new remedy.
4. Comment: !he remedy selected for this site should include sampling and
institutional controls on the Potomac aquifer due to the risk presented by an
aquifer interconnection.
Response: !he Remedial Investigation demonstrated conclusively that an
interconnec:ion does not exist between the Columbia and Potomac aquifer in the
area or ::-.. si:e. For this reasons, it is unnecessary to either sample or
2
-------
place instiCUtional controls on the Potomac aquifer. However, as the public
has expressed concern over the possible risk to the Potomac, sampling will be
conducted on the Potomac on an annual basis as a safeguard. It is DNREC and
EPA's opinion that the placement of institutional controls on the Potomac is
unwarranted.
5. Comment: Can the tris spilled be related to the number of cancer deaths
in neighborhood located adjacent to the site?
Response: Tris has been found to be a noncarcinogen. Therefore, the
cancer deaths cannot be attributed to the presence of tris in the groundwater.
In addition, the groundwater is not currently being used as a potable supply
and has not been used since the detection of tris, which was immediately after
the spill.
6. Comment: Experts outside of the U.S. EPA feel that tris is a carcinogen.
Response: The U. S. EPA has concluded through their review of
toxicological data on tris that it is not a carcinogen. The data used to make
this determination and their basis for this conclusion can be found in the
'Administrative Record located inthe'Repository at the DNREC Building.
7. Comment: Why are there two opinions on the carcinogenicity of tris?
there a concrete method of determinating whether this compound is
carcinogenic?
Response: Animal tests where animals are subjected to high doses of the
compound are used to determine carcinogenicity of a compound. The test results
are then extrapolated to humans with difficulty due to the difference of high
to low dose exposure and interspecies extrapolation. Experts may interpret
the results differently and draw opposing conclusions.
Is
3
-------
.A: Ai
'~;':f
J:~~,
-:'-.~~.;:~=-:--
OFFICE OF THE
DIRECTOR
STATE OF DELAWARE
DEPARTMENT OF NATURAL RESOURCES
Be ENVIRONMENTAL CONTROL
DIVISION OF AIR 8: WASTE MANAGEMENT
89 KINGS HIG...WAY
PO. Box 1401
DOVER. DEL-AWARE 19903
TEL-E""'ONE: (302) 736 . 476::
September 27, 1989
Mr. Edwin B. Erickson
Regional Administrator
U.S. EPA Region III
841 Chestnut Street
Philadelphia, PA 19114
Subject: Declaration of the Record of Decision for
~.~ .~~~ Castle Spill Site .
De~:~:~:: .
As per Multisite Cooperative Agreement V-003374-0l, the State of Delaware
Department of Natural Resources and Environmental Control (DNREC), CERCLA
Management Branch, has completed the Record of Decision (ROD) for the New
Castle Spill Site.
Through the coordinated efforts Qf DNREC and EPA, the Department believes
appropriate remedy for the site has been selected. By signature of
Declaration of the ROD, DNREC has formally expressed its support of
selected remedy.
an
the
the
In order to finalize the New Castle Spill Site ROD, we
EPA's signature on the Declaration of the ROD.
are
now
requesting
51 c /;.~
Phil 1p G. etalhc
Dire tor
,
PGR/DPD/dpd
DPD2l69
Attachment
cc. E.H. Clark, II
G.A. Molchan
J.J Hardman
G.B. Chadwick
D.P. Dewsbury
------- |