PB95-963119
EPA/ESD/R08-93/094
March 1995
EPA Superfimd
Explanation of Significant Difference
for the Record of Decision:
Denver Radium Superfund Site
(O.U. 7), Denver, CO
10/9/1992
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EXPLANATION OF SIGNIFICANT DIFFERENCES
DENVER RADIUM SUPERFUND SITE
OPERABLE UNIT VII - STREETS
September 15, 1992
OVERVIEW
The purpose of this document is to explain the significant -
differences between the remedy selected in the Record of Decision
(ROD), signed by the u.S.- Environmental Protection Agency (EPA)
on March 24, 1986, and the remedy which will be implemented at -
Operable Unit VII of the Denver Radium Superfund Site. Operable
Unit VII - Streets, is located in Denver, Colorado and consists
of eight street segments and certain intersections in the
Cheesman Park area and one segment in the upper downtown area
(see Figure 1). The exact location of these street segments are
as follows:
- 9th Avenue from Ogden Street to Cheesman Park;
- 11th Avenue from Josephine Street to Cheesman Park;
- 23rd Street from California Street to LaWrence Street;
- Corona Street from 7th Avenue to 10th Avenue;
- Downing Street from 7th Avenue to lOth Avenue;
- Humboldt Street from 7th Avenue to 9th Avenue;
- Lafayette Street from 1st Avenue to lOth Avenue;
- Marion Street from 6th Avenue to lOth Avenue; and
- York Street from 6th Avenue to 13th Avenue.
These nine contaminated street segments extend approximately 4.5
miles through largely residential areas and are owned by the City
and County of Denver. Approximately 800 households are situated
adjacent to these contaminated streets. Other than minimal
excavation controls imposed by Denver Public Health Engineering
and Denver Public Works Departments, use of these streets has not
been restricted.
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EXPLANATION OF SIGNIFICANT
DIFFERENCES (ESD)
This ESD describes ~ significant change to the remedy
that will be implemented at Operable Unit VII of the
Denver Radium Site. " "
The ROD signed in March 1986, called for radium-
contaminated material in the streets to be left in
place with the exception of material excavated during
routine maintenance, repair or other construction
activities. Such material was to 'be removed to an off-
s~te repository approved for storage or disposal of
radium-contaminated materialo
The significant difference and change to the
original remedy relates to on-site rete~tion and
reburial of radium-contaminated material excavated,
during all maintenance" repair or, other ,constructiQri
activities. " ",'
Due to the low levels of radioac~ive contamination at Operable
Unit VII, no remedial activities are planned for this specific
operable unit. Should maintenance, repair or other construction
activities be required, excavated radium-contaminated materials
will be retained and reburied on-site, if feasible, provided that
the area to be excavated is not greater than 20% of the total
area of the roadway in one city block. The 20% figure is based
on the assumption that all maintenance, repair or other
construction activities can be successfully performed without
excavation of more than 20% of the total area of the street.
Special variance to the 20% limit may be granted by the Colorado
Department of Health should an unusual circumstance require such
a variance. The location of radium-contaminated asphalt reburied
,on-site will be permanently documented by the implementing
agency. Reburied materials will be covered with a new, hard
surface, such as asphalt or concrete, having a minimum depth of 6
inches to insure no direct exposure. If retention and reburial
are not feasible, the materials will be disposed of at a
licensed, off-site disposal facility, consistent with the ROD.
This ESD provides a brief background on the Site, describes the
original remedy selected in, the ROD, and explains the ways in
which the modified remedy differs from the original remedy. It
also discusses the modified remedy's compliance with all legal
requirements, and provides instructions on how to obtain more
information on this Site. '
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The Administrative Record which 'contains this ESD, as well as
complete documentation relating to the remediation of the Site,
is available for public review at the location indicated below.
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ADMINISTRATIVE RECORD LOCATION
EPA Superfund Record Center
999 18th Street, Suite 500
Denver, Colorado 80202
Hours: M-F 8:00 AM - 4:30 PM
Phone (303) 293-1807
Toll-free Number 1-800-759-4372,
ext 1807.
This ESD is prepared in fulfillment of EPA's public participation
responsibilities under Section 117(c) of the Comprehensive,
Environmental Response, Compensation, and Liability Act of 1980,
42 U.S.C. Section 9601, et seq. ',(CERCLA) (more cO.Imnonly referred
to as Superfund), as amended by the Superfund Amendme~ts'and
Reaut~orization Act of 1986, and Section 300.435(c) (2) (1) of the
National Contingency Plan, 40 C.F.R. Part 300 (NCP).
SITE HISTORY AND BACKGROUND
In 1979, EPA discovered the presence of several long-forgotten
radium processing locations which were active in Denver from 1914
through 1925. Historically, production of refined radium
produced large quantities of radioactive waste materials. These
waste materials were discarded or left on-site when the
processing facilities were closed. Subsequently, much of this
waste material was used as fill, cover and foundation material
and sometimes as an aggregate in cement' and asphalt mixtures. As
a result, contaminated asphalt pavement was placed in certain
city streets in Denver.
The Denver Radium Site was placed on the Interim priorities List
in October 1981 and on the National Priorities List (NPL) in
September 1983. The Colorado Department of Health began
engineering assessment studies and a total of nine contaminated
street segments were identified. The Denver Public Health
Engineering Department began monitoring ga.xmna radiation levels
during any excavation carried out in these streets. State
studies were discontinued when RCRA grant funds ran out. BPA
resumed RI/FS activities in 1983. . In July 1985, EPA completed a
study further defining contamination in City streets. A Draft
Feasibility Study was released on July 26, 1985. No Final
Feasibility Study was issued. A Record of Decision was issued by
EPA on March 24, 1986. '
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SITE DESCRIPTION
Street' segments in Operable Unit VII contain a 4 to 6 inch layer
or radium-contaminated asphalt. This contaminated layer is
underlain by cqmpacted gravel road base material and is usually
overlain by 4 to 12 inches of uncontaminated asphalt pavement.
Estimates indicate that Operable Unit VII - Streets contain
approximately 38,500 cu/yds of radium-contaminated material
covering some 832,000 square feet. Radium contamination does not
extend beyond the paved right-of-way of the streets and does not
appear to have migrated into the soils below the contaminated
asphalt.
CURRENT SITE STATUS
The risk assessment for OU VII, found in the July 26, 1985,
Feasibility Study, stated that contamination in Operable Unit VII
- 'Streets poses a minimal threat t:o' 'public , heal th. This- is due:,
to the fact that the radiqactive material is bound in the asphalt
and is not free to move in ariy direction. - As-,long as the', "
contaminated material remains in its present location, the
potential routes of human exposure to the radioactivity are
limited because the contaminated material is well-contained.
None of the contaminated streets are near surface or ground water
resources and there is little potential for erosion or leaching
of the contaminated material due to the pavement cap.
In general, the most significant routes of exposure to radiation
from radium contamination at the Denver Radium Site are, in
descending order of importance: (1) inhalation of radon gas and
its decay products; (2) direct gamma radiation'exposure from the
decay of radium and its progeny; and (3) ingestion or inhalation
of radium-contaminated material. In general, the greater the
exposure rate and the longer the exposure to radiation, the
greater the associated health risks.
The risk,assessment for OU VII determined that the most
significant risk to public health associated with the
contaminated asphalt was that posed by gamma radiation emanating
from the streets. However, the risk assessment concluded that
this represented a negligible health threat since an individual
would have to stand at the location of the highest gamma
-radiation (in the middle of York Street) for five hours a day
every day of the year in order to exceed the recommended exposure
guideline of 100 milirems per year above background set by the
Inte~tional Council on Radiol9gic Protection.
In addition, the risk assessment stated that the other routes of
exposure were insignificant for the following reasons: (1) all
.radon gas .generated by-.the decay of radium . will immediately ,be -
diluted by atmospheric air to the degree that it will pose no
health hazard; and (2) the radiUm is encased in asphalt, so it is
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not in a form that easily lends itself to ingestion or
inhalation. -
~dium-contaminated material in the streets presents only a
minimal hazard in its present state. However, uncon~rolled
excavation in the streets would present the possibility of
release of radon or radioactive ma~erials potentially increasing
the risks from all three exposure pathways. Both the original
remedy described in the ROD and the modified remedy described in
this ESD provide measures to ensure that maintenance, repair or
other construction activities within OU VII will not result in
the uncontrolled release of radon or radioactive materials.
SUMMARY OF THE MARCH 24. 1986. RECORD OF DECISION -
The objective of the remedy selected in the ROD is to reduce
human exposure to radium contamination bound in the asphalt of
certain streets of Operable-Unit VII. The major components of
the remedy selected in the March 24; 1986 ROD are:
*
Leaving the contaminated material in place; .
*
Improving institutional controls so that all maintenance,
repair or other construction activities in the affected
streets by government agencies, utility companies, contracting
companies and private individuals, will be monitored; and
*
during maintenance,
the affec~ed
or
Taking any contaminated material excava~ed
repair or other construction activities in
streets to a facility approved for storage
disposal of contaminated material.
According to the ROD, the standards found in 40 C.F.R. Part 192
serve as the cleanup goals which remedial actions taken at the
Denver Radium Site muSt attain. The ROD states that the -relevant
and appropriate requirement is found at 40 C.F.R. Section
192.12(a), which specifies the maximum allowable radium
concentration in soil. In order to comply with 40 C.F.R. Section
192.12(a) , remedial actions must be conducted when the
concentration of radium in land averaged over any area of 100
square me~ers exceeds the background level- by more than (1) 5
picocuries of radium per gram soil averaged over the first 15
centimeters of soil below the surface, and (2) 15 picocuries of
radium per gram of soil averaged over 15 centimeter thick layers
of soil more than 15 centimeters belo~ the surface. The
concentrations of radium present in Operable Unit VII - Streets
exceed these levels.
In addition, the ROD states that only total excavation would
satisfy--the standard outlined- in 40-C.F-.R. Section 192.. 12(a).,-
and that the Total Excavation Alternative was eliminated during
the initial screening of remedial alternatives for Operable Unit
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VII' - Streets because the cost of implementing that alternative
far exceeded the cost of other alternatives, without providing
substantially greater public health or environmental protection.
~cording to 40 C.F.R. Section 192.21(c), the use of supplemental
standards is appropriate when the estimated cost of remedial
action to satisfy 40 C.F.R. Section 192.12(a) at a Site is
unreasonably high relative to the long-ter.m benefits, and the
residual radioactive materials do not pose a clear present or
future hazard. In evaluating this hazard, the likelihood that
buildings will be erected or that people will spend long periods
of t~e at such a Site should be considered. Section 192.21(c)
further states that "remedial action will generally not be
necessary where residual radioactive materials have been placed
semi-per.manently in a location where site-specific factors l~t
their hazard and from which they are costly or difficult to
remove, or where only minor quantities of residual radioactive
materials are involved." Examples given include residual
radioactive materials pr~sent under hard surface p\lblic roads .and~....
around public. sewer lines. .. .. ..... .
Further.more, the ROD states that if a supplemental standard is
applied, the implementing agency must select and perfor.m remedial
actions that come as close to the otherwise pertinent standard as
is reasonable under the circumstances. The remedial alternative
selected in the ROD, the Modified No Action Alternative, includes
leaving contaminated materials in place and establishing
institutional controls to monitor all routine maintenance, repair
or other construction activities in the affected streets. This
remedy complies with the supplemental standards and comes as
close to the standards outlined in 40 C.F.R. Part 192.12(a) as is
reasonable under the circumstances. Finally, the ROD states that
the Operation and Maintenance (0& M) activities required to
ensure the effectiveness of the remedy include off-site disposal
of contaminated material removed from the streets during
maintenance, repair or construction activities.
DESCRIPTION OF SIGNIFICANT DIFFERENCES
The significant differences between the remedy described in the
ROD and this ESD are:
In the ROD, a portion of the remedy dealt with off-site
removal and disposal of any radium-contaminated
materials excavated during maintenance, repair or other
construction activities in the affected streets of
Operable Unit VII of the Denver Radium Site. This
document modifies the original ROD to allow for the
retention and on-site reburial of radium-contaminated
materials' that are excavated during maintenance, repair
or other construction-activities within Operable-Unit
VII streets, if such retention and reburial is
feasible, provided that the area to be excavated is not.
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greater than 20% of the total area of the roadway in .
one city block. Special. variance to the 20% limit may
be granted by the Colorado Department of Health should
an unusual circumstance require such a variance. The
location of radium-contaminated asphalt reburied on-
site will be permanently documented by the implementing
agency. Reburied materials will be covered with a new,
hard surface having a minimum depth of 6 inches. In
situations where the retention and reburial of
contaminated materials is not feasible, the materials
will be disposed of at a licensed off-site disposal
facility consistent with the ROD. Examples of
.situations where it may not be feasible to rebury
contaminated material include: (1) a water main break
which results in flooding that may preclude the
retention and on-site reburial of contaminated asphalt;
and (2) an activity such as construction of handicapped
sidewalk ramps which could take up .contaminated
material from the asphalt surface and not.provide a
place for reburial. All other .aspects of the 1986
selected remedy remain the same. .
The modified remedy described in this ESD meets the above-
. referenced supplemental standards and comes .as close to standards
outlined in 40 C.F.R. Section 192.12(a) as is reasonable under
the circumstances.
JUSTIFICATION FOR CHANGE
The remedy selected in the ROD included leaving contaminated
material in place and establishing institutional controls to
monitor all routine maintenance, repair or construction
activities in the. affected streets. 0 & M activities required to
ensure the effectiveness of the selected remedy included off-site
disposal of contaminated material removed from the streets during
these activities. The sole change engendered by the modified
remedy is that a relatively minor amount of contaminated mater~al
removed from the streets during routine or emergency maintenance,
repair or other construction activity, would be retained and
reburied, if feasible. The location of radium-contaminated
asphalt reburied on-site will be permanently documented by the
implementing agency. The modified remedy reduces the need to
transport contaminated material and the risk associated with such
transport. In addition, the modified remedy meets the
supplemental standards outlined in 40 C.F.R. Sections 192.21 and
192.22, comes as close to the standards outlined in 40 C.F.R.
Section 192.12(a) as is acceptable under the circumstances and is
cost effective.
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SUMMARY OF SIGNIFICANT DIFFERENCES
The major differences between the original ROD remedy and the
modified remedy in this ESD are summarized as follows:
ORIGINAL REMEDY
* Off-site disposal of radium-contaminated materials excavated
during routine maintenance, repair or construction activities in
the affected streets of Operable Unit VII.
MODIFIED REMEDY
* On-site.rei:ention and reburial of radium-contaminated
materials excavated during routine or emergency maintenance,
repair or other construction activities in the affected streets.
of Operable Unit VII, if feasible, provided that the area. .to be
excavated is not greater than 20% of. the total area of the.
roadway in one city block. .. Special variance to the 20% limit may
be granted by the Colorado Department of Health should an unusual
circumstance require such a variance. Contaminated materials
that are reburied will be covered with a new, hard surface having
.a minimum depth of 6 inches to ensure no direct exposure. . If .
retention and reburial of contaminated materials is not feasible,
the materials will be disposed of at a licensed, off-site
disposal facility, consistent with the ROD.
SUPPORT AGENCY COMMENTS
The Colorado Department of Health has reviewed this ESD and
supports implementation of the modified remedy as defined herein.
STATUTORY DETERMINATIONS
It is affirmed by both EPA and the State of Colorado that this
modified remedy continues to satisfy all statutory requirements.
Fur~her, both EPA and the State of Colorado believe that the
modified remedy is protective of both human health and the
environment and complies with Federal and State requirements that
are applicable or relevant and appropriate to this remedial
action, and is cost effective.
GLOSSARY
ADMINISTRATIVE RECORD: The body of documents upon which EPA
bases a cleanup decision about a Superfund site. By law, the
administrative record fi~e, which is the file containing the
documents used in selecting the remedy for a site, must be made
. available to the public at a repository located near the
- Superfund site. . . -. -. --
APPLICABLE OR RELEVANT AND APPROPRIA.TE REQUIREMENTS (ARARs):
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Refers to the Federal and State requirements that a selected
remedy is required to attain. ARARs include requirements such as
allowable air emissions limits and allowable levels of
contaminants in site media (such as soils and water) .
COMPREHENSIVE ENVIRONMENTAL RESPONSE, COMPENSATION, AND LIABILITY
ACT OF 1980 (CERCLA OR SUPERFUND): A law passed in 1980 that
establishes a program to clean up abandoned hazardous waste
sites.
>
EXPLANATION OF SIGNIFICANT DIFFERENCES (ESD): Refers to a ,
requirement of Section 117(c) of CERCLA, as amended, and Section
300.435 (c) (2) (i) of the NCP, that the lead agency, following the
, adoption of th~ ROD, document and explain any significant changes
.--"'to tne ROD.' . The ESD and supporting information must be made
~ : 'available to. the public in the administrative record and
information repository for the site. In addition, a public
notice summarizing the'ESD mUst be :p~lished in a major local
newspaper of general circulation. . " .. ' ' ,.'. '.
FEASIBILITY STUDY (FS): A study required under Superfund in
which alternatives for cleaning up site contamination are
identified, screened and compared.
INSTITUTIONAL CONTROLS: This term may refer to legal, non-
engineering methods used to prevent or restrict use of, or access
to, contaminated soils and ground water. In general,
institutional controls may take the form of rules, regulations,
laws, or covenants such as co~ty or city ordinances, building
permits, or other appropriate measures,. as necessary.
,NATIONAL CONTINGENCY PLAN (NCP): A body of Federal regulations
governing the implementation of CERCLA.
NATIONAL PRIORITIES LIST {NPL): EPA's list of top-priority
hazardous waste sites that are eligible for investigation and
cleanup under the Federal Superfund program.
RECORD OF DECISION (ROD): A public document that sets forth and
explains the cleanup alternative(s) to be used at a Superfund
site. The ROD is generally based on information from the
remedial investigation and feasibility studies, public' comments,
and community concerns.
REMEDIAL ACTION: The actual construction or implementation phase
of Superfund work during which the selected remedy is put into
place.
REMEDIAL INVESTIGATION (RI): A study required under Superfund
that is conducted in order-to identify the-types, -amounts-and.
locations of contamination at a site.
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SUPERFUND AMENDMENTS AND REAUTHORIZATION ACT OF 1986:
passed in 1986 that reauthorizes the Superfund law.
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OCT
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IIIIIIII~
045740
AOMiNlSTRA TIVE
RECORD
~,.
.~
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
. REGION Viii
99.9 18th STREET - SUITE 500
DENVER, COLORADO 80202-2466
Ref:
8HWM-SR
MEMORANDUM
FROM:
Jack W. McGraw
Acting Regional Administrator
Robert L. Duprey, DirectJz:?~.
Hazardous Waste Manageme~>Dlv~, - ¥'
Explanation of Significant Dif ierences
Denver Radium Superfund Site, Operable
Streets
to the ROD for
Unit VII -
TO:
SUBJECT:
Attached is the final Explanation of Significant Differences
(ESD) to the 1986 Record of Decision (ROD) and the remedy which
will -be implemented at Operable Unit VII of the Denver Radium
Superfund Site.
The ROD signed in March 1986, called for radium-contaminated
asphalt in the streets to be. left in place with the exception of
material excavated during routine maintenance, repair or other
construction activities. Such material was to be removed to an
off-site repository approved for storage or disposal of radium-
contaminated material. .
The change to the original remedy will allow for on-site
retention and reburial of radium-contaminated material excavated
during all maintenance, repair or other construction activities.
The excavated material will simply be placed back in the street
and covered with new asphalt.
The State of Colorado supports implementation of the remedy
as proposed in this ESD. In addition, EPA Headquarters has
reviewed this ESD and has provided written concurrence to the
Region (attached). I recommend approval of the changes to the
remedy as proposed in this ESD.
.Attachment
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Printed on R8Cycled Paper
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EXPLANATION OF SIGNIFICANT DIFFERENCES
RECORD OF DECISION (ROD) - OPERABLE UNIT VII'
DENvER RADIUM SUPERFUND SITE
DECLARATION
, Considering the new information that has been developed and the,
changes ~hat.have been made to the selected remedy chosen in the
,~rc}]:--,,24t).98.6 "ROD, EPA has determined that the remedy remains
,:~~<,protectivebf h\J.n$1 health and the environment, complies with
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UNITED STATES ENVIRONMENTAL PROTET10N AGENCV
WASHINGTON, D.C. ~
OFFICE 01' ,
SOUDWABTE AftD 5Mli:AGliNCY 1'15SPo..SE
SEP 2 4 t~
TransmlttoC via Fax
HBHQR»1J)UX
8tJ8JJ:C'J!:' BSD Conaul't:a't:ion -' Denver Radium sup~Undl
site OU VII I 1 f
Nancy'r. Br1scoe ~~~~.~
OWPE RegiO~~ coo~~~'t ~-, ". '
~im Rehder .
Remedial Project Man~qer
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The purpose or this memorandum '18 to confirm Heo.dquarter I s support
of the september, 1992 Explanation of Siqnificant Differences (ESD)
for Denver Radiwn site, Operable unit VIJ:. Consultation regarding
.this ESD was conducted between TiJD Rehder (Denver bdium RPM) ,:-
Neilima SQ%1ja~ia (OWPE section Chief) and Nancy Briscoe (OWPE
Reqional Coordinator) on september 23, ~992.
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Because the ESD proposes a rela1:ively minor tundamental change in
t.he remedy (on-sit.e retention and re})uria1 ot radium-contaminated
materials excavatecl durinq routine or emergency maintenance or
repair), and because the modified remedy- is consistent with the
remedy chasen for t:he Majority of radium-con't2lminated materials on-
site, '!:he Offioe of Was~e Proqrams EnfOrcement supports the ESD.
Accordingly, EPA Region VIII' }{as mat and complied with all
consultation requirements of the TWenty Third Remedy Delegation
Report.. 'i .
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