PB95-963126
EPA/ESD/R08-95/099
March 1995
EPA Superfund
Explanation of Significant Difference
for the Record of Decision:
Denver Radium Superfund Site
(O.U. 6, 9, & 11), Denver, CO
1/19/1995
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EXPLANATION OP SIGNIPICANT DIPFERENCES
DENVER RADIUM SITE
OPERABLE UNITS VI, IX & XI
INTRODUCTION
The purpose of this document is to explain the significant
differences between the remedy selected in the Record of Decision
(ROD), issued by the u.s. Environmental Protection Agency (EPA)
on September 29, 1987, and the remedy that was implemented at
Operable Units VI, IX and XI (OUs VI/IX/XI) of the Denver Radium
Superfund. Site. EPA is the lead agency at these operable units
with the support of the Colorado Department of Public Health and
Environment (CDPHE). .
OUs VI/IX/XI consist of a group of properties known
collectively as the "Open Space Properties". These properties
are located in Denver in proximity to the South Platte River and:
along the Santa Fe Drive corridor (Figure 1). . .
This Explanation of Significant Differences (ESD) describes
changes to the remedy that were implemented at OUs VI/IX/XI.
This ESD explains: 1) why temporary containment was not required;
2) how the area of contamination was extended; and 3) why small
amounts of contaminated soils were left in place based on
supplemental standards and how these soils will be managed.
The Administrative Record, in accordance with Section
300.825(a) (2) of the National Contingency Plan (NCP),40 CFR Part
300, contains this ESD, the documents that form the basis for the
decision to modify the response action, and the documentation
relating to selecting a remedy for OUs VI/IX/XI. This
information is available for public review at the following
location: .
EPA Superfund Records Center
999 18th Street, Suite 500
Denver, Colorado 80202
Hours: M-F 8:00 AM to 4:30 PM
Telephone: . (303) 293-1807
This ESD is prepa~ed 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 seg. (CERCLA), (more
commonly referred to as Superfund), as amended by the Superfund
Amendments and Reauthorization Act of 1986 (SARA), and Section
300.435(c) (2) (1) of the National Oil and Hazardous Substances
- Pollution Contingency Plan (NCPL-40 CFR Part 300.
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..' S:JiI'!'E .,aJ: STORY
The Denver Radium Site consists of over 40 properties in
Denver, Colorado, along the South Platte River Valley that were
contaminated with radioactive processing residues left from the
radium industry in the early 1900's. These properties were
divided into 11 groups or "operable units" (Figure 1) to
facilitate remediation of the site. .
In 1983, EPA placed the Denver Radium Site on the NPL,
making the site eligible for cleanup under the EPA Superfund'
Program. EPA released a Remedial Investigation (RI) for OUs
VI/IX/XI on April 30, 1986 and a Feasibility Study (FS) on August
1, 1987. On September 29, 1987, EPA issued a ROD.
OUs VI/IX/XI are made up of a number of scattered, outlying
properties involving both interior and exterior radioactive
contamination. The subject of. t.his ESD is two-properties. . ..
situated within OU VI where relativeiysmall amouritsofra4i~~
contaminated soils were left in place. . - . - - .
The two OU VI properties are identified and located as
follows:
15th Street Properties
2301 15th Street (Figure 2)
Environmental Materials, Inc. (EMI)
1155 West 5th Avenue (Figure 2e)
SUMMARY OF THE REMEDY SELECTED IN THE 1987 RECORD OF DECISION
Radium and its associated decay products are the primary
contaminan~s of concern at OUs VI/IX/XI of the Denver Radium
Site. Radiologic contamination poses a health hazard by way of
three routes of exposure: 1} inhalation of radon gas and its
decay products; 2} direct exposure to gamma radiation 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 healtn hazard. Of these exposure routes,
the most significant risk is that posed by radon gas accumulating
in buildings.
The remedial action alternative preferred by EPA for OUs
VI/IX/XI was Off-site Permanent Disposal. Because an off-site
disposal facility was not available at the time the September.
1987 ROD was issued, EPA selected on-site temporary containment
(capping) or excavation and removal to a central location,
capping and maintaining the cap until.excavation andupermanent --
off~site disposal. The temporary containment plan was abandoned
when a permanent off-site disposal facility was licensed in Utah
in 1988.
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OPERABLE UNIT I '12TH AVE. AND OUIVAS ST. AREA
OPERABLE UNIT II .11 TH ST AND UMATILLA ST AREA
OPERABLE UNIT III 1000 w. LOUISIANA AVE. AREA
OPERABLE UNIT IV!V 500 S. SANTA FE DRIVE
OPERABLE UNIT VI A 2J01 15TH STREET
B '1190 YUMA STREET
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OPERABLE UNIT VIII 1805 S. BANNOCK ST.
OPERABLE UNIT IX 2000 E. COLFAX AVE.
OPERABLE UNIT X IJ14 W. EVANS AVE.
OPERABLE UNIT XI 1295 S. SANTA FE DRIVE:
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Figure 1. Denver Radium Site.
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-SUMMARY OF SIGNIFICANT DIFFERENCES
The significant differences from the 1987 ROD are:
.1) temporary containment of contamination was not required;
2) the area of contamination and associated volume of
contaminated soils increased; and 3) relatively small amounts of
radium-contaminated soils were left in place based upon
supplemental standards.
DIFFERENCE NO 1:
Temporary on-site containment was not necessary because a
permanent off-site disposal facility became available. The
contaminated material was shipped by rail to the Envirocare of
Utah, Inc. disposal facility in Tooele County, Utah.
DIFFERENCE NO 2:
During remediation of the Alley Property (located between.
5th and 6th Avenues and Lipan Street, under the 6th Street
overpass), contaminated .soils were identified at the adjacent.
Environmental Materials, Inc. Property located at 1155 West 5th
Avenue (Figures 2, 2e & 3). This 2.4 acre lot contains a 19,000
square foot masonry building and two outlying buildings. The
property is underlain by approximately thirty feet of alluvium
which rests on the Denver Formation. Surveys indicated that Ra
226 contaminated soils were present both beneath and outside the
EMI building. Investigations indicated concentrations of Ra 226
as high as 443.8 pCi/g at depths ranging from 6 to 78 inches.
DIFFERENCE NO 3:
Radium contamination was left in place at the following
locations: a) near a concrete box culvert on the Confluence Park
property; and b) under the Environmental Materials (EMI)
Building. The reasons that radiologic contamination was not
excavated from these locations are summarized below: .
a) The two areas of contamination left in place next to the
concrete culvert on the Confluence Park property are associated
with a layer of gravel to cobble sized "slag" that dips steeply
to the East. Further excavation in these areas would have placed
the culvert, which was leaking from several places, at risk.
This contamination is overlain by five feet of clean backfill and
does not pose a risk to human health or the environment.
b) Contamination was not excavateq from under the EM! building
since EPA determined that such action was not necessary for the
remedy to be protective and to meet the interior cleanup
standards set forth in 40 CFR Section 192.12 (b).. . That se~tion
states that in any occupied or habitable building:
i)
The objective of remedial action shall be, and reasonable
effort shall be made to achieve, annual radon decay product
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#~centration not to exceed 0.02 WL. The radon decay product '.
concentration in any case, shall not exceed 0.03 WL and,
ii) The level of gamma radiation shall not exceed the background
level by more than 20 microroentgensper hour.
The radon concentration and gamma radiation levels in the
EMI building meet 'these standards.
40 CFR Part 192 provides that under certain circumstances
the agency performing the cleanup may choose a remedial action
thatdoe~ not achieve complete removal of radium contamination to
'thelevelsdes,cribed in 40 CPR Section 192.12 (a). ' Under 40 CFR
Sect:i~~l, ~9.2'.2~ (c),nsuppleme~tal standards" can be applied when:
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,.~>The' es'timat,ed cost' of remedial action to satisfy 40 CFR
~>. Section 192.12 (a) at a site is unreasonably high relative, to
", the long-term benefits, and ,the residual radioactive ,,"
materials do not pOSe a clear 'present or futurehaza.rd.. The
likelihood that buildings will be erected ortha,t people
will spend long periods of time at such a vicinity site,
should be considered in evaluating this hazard. Remedial
action will generally not be necessary where residual
radioactive materials have been placed semi-permanently in a
location where site-specific factors limit their hazard and
from which they are costly or difficult to remove, or where
only minor quantities of residual radioactive materials are
involved. Examples are residual radioactive materials under
hard surface public roads and sidewalks, around public sewer
lines, or in fence post foundations.
The residual radioactive material that was left in place at
OUVI meets the criteria for the application of supplemental
standards. Detailed maps, included in the June 1994 Operable
Unit VI closeout report, show the location and estimated volume
of the radium contamination that remains on the OU VI properties.'
This closeout report is included in the Administrative Record so
that any agencies or individuals who conduct maintenance or
excavation activities on the property will be aware of the
presence of radiologically contaminated materials. Institutional
controls will be placed on these properties to assure that
interested parties are aware of the presence of radiologic
contamination on OU VI. Institutional controls may include deed
restrictions and special zoning.
Summary of Siqnificant Differences
Oriqinal Remedy
Modified Remedv
1) Tert}.p0 rary. on - site
containment of radium-
contaminated soil and removal
to permanent disposal facility
when one becomes available.
1) Temporary containment was
not' necessarY:' an- off-site
disposal facility became
available in 1988.
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2} Excavation of contaminated
material from all properties
identified in the ROD.
2} Previously identified
contamination extended onto
adjacent property at 1.1.55.
West 5th Avenue.
3} Excavation of all
contaminated soil.
3} Small amounts of radium-
contaminated soil were left
in place on, two properties in
OU VI.
SUPPORT AGENCY COMMENTS
The State of Colorado concurs with the implementation of the
remedy presented in this ESD.
STATUTORY DETERMINATIONS
Considering the new information that has been developed and
the changes that have been made to the selected remedy, EPA and
the Colorado Department of Public Health and Environment believe
that the remedy remains protective of human health and the ,
environment, complies with federal and state requirements that
are applicable or relevant and appropriate to this remedial
action, and is cost-effective. In addition, the revised remedy
utilizes permanent solutions and alternative treatment '
technologies to the maximum extent practicable for this site.
Even though the remedy does not satisfy the statutory preference
for treatment which reduces the toxicity, mobility, or volume of
hazardous substances as its principal element, the principal
threat at the properties will be addresSed. Treatment was
determined to be impracticable based upon effectiveness,
technical feasibility, implementability and cost factors.,
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Roy Romer, ~emor
Patricia A. Nolan, MD, MPH, Executive Director
Dedicaced to protecting and improving the health and environment of the people of Colorado
HAZARDOUS MATERIAlS AND WASTE MANAGEMENT DIVISION
4300 Cheny Creek Dr. S. 222 S. 6th Street, Room 232
Denver, Colorado 80222-1 S30 Grand Junction, Colorado 81501-2768
Phone (303) 692-3300 Phone (303) 248-7164
Fax (303) 759-5355 Fax (303) 248-7198
STATE OF COLOAADO
~
Ms. Rebecca J. Thomas
U.S. EPA Region VITI
999 18th Street, Suite 500
Denver, CO 80202
ColOrado ~ent
~fPubliCBealth
cziui EnvUanment
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January 6, 1995
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Re:
Explanation of Significant Differences, Denver Radium Site, Operable Units VI, IX
&XI
Dear RebecCa:
This letter confirms the Colorado Department of Public Health and Environment's
(CDPHE) support of the U.S. Environmental Protection Agency's (EPA) issuance of an
Explanation of Significant Differences (ESD) to the Denver Radium' Site, Operable Units
(OU) VI, IX & XI. . . .
The ESD accounts for the differences between the original Record Of Decision (ROD) and
the remedial action performed. The changes were necessary because 1) temporary storage
. was not required prior to removal of contaminated materials to a permanent disposal
facility; 2) during remedial action, contaminated deposits were identified at the adjacent
Environmental Materials, Inc. (EMI) property located at 1155 West 5th Avenue; and 3)
radium contamination was left in place next to a concrete box culvert on the Confluence
Park property, and beneath the EMI building. The contaminated materials which remain
in place will be managed through the use of institutional controls.
CDPHE agrees that the revised remedy remains protective of human health and
environment, complies with federal and state requirements that are relevant and
appropriate, and is cost effective.
Sincerely,
L/~
Lawrence J. Bruskin, P .E.
Denver Radium State--Project -Officer --
Hazardous Materials and Waste
Management Division
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION VIII
999 18th STREET. SUITE 500
DENVER, COLORADO 80202:2466
JAN 17.
Ref:
8HWM-SR
MEMORANDUM
FROM:
Robert L. Duprey, Director
Hazardous Waste Maruigemejf ~.i:t~ion
Rebecca J. Thomas, RPM ~
Denver Radium proj ect.. -....
Denver Radium Superfund Site
Operable Units VI/IX/XI
Explanation of Significant Differences
TO:
SUBJECT:
Attached is an Explanation of Significant Differences (ESD)
between the September 1987 Record of Decision (ROD) and the
remedy which was implemented at Operable Units VI/IX/XI (OUs
VI/IX/XI) of the Denver Radium Superfund Site.
The remedy selected in the 1987 ROD for OUs VI/IX/XI called
for the excavation of radium-contaminated soils to meet cleanup
levels identified in 40 CFR Part 192. Excavated soils were to be
temporarily maintained on-site until a permanent off~site .
disposal facility became available.
It became necessary to modify the selected remedy to address
the following significant differences from the 1987 ROD:
1)
Temporary containment was not necessary since an off-site
disposal facility became available in 1988.
Previously identified contamination increased in volume and
extended onto adjacent property at 1155 West 5th Avenue.
2)
Small amounts of radium-contaminated soil were left in place
on two properties in OU VI based upon supplemental standards.
The Colorado Department of Public Health and Environment
supported implementation of the remedy as described in this ESD.
- In addition, EPA Headquarters was consulted regarding this ESD
and had no comments. I recommend approval. of the changes to the
remedy as described in this ESD. . .
3)
o Printed on Recycled Paper.
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EXPLANATION OF SIGNIFICANT DIFFERENCES
RECORD OF DECISION (ROD) - OPERABLE UNITS VI/IX/XI
DENVER RADIUM SUPERFUND SITE
DECLARATION
Considering the new information that has been developed and
the changes that have been made to the selected remedy chosen in
, the' September 1987 ROD, EPA has dete~ned that the remedy
rema:iIlsprotective,of.human health and the environment, complies
wit;h''F'eqeral'' and, State requirements that are applicable or
.r~ye.J,ant arid appropriate to "this remedial action, and is cost-
'. ,effective..' The remedy 'utilized permanent solutions and' ,
:::alt.ernative treatmenttechnologles tb.the- extent practicable. -
.; ,Even though the revised r~ec;Iy does ilotsatisfy the Statutory "
, - preference for treatment which reduces' the toxicity, mobility! ,or'
volume of hazardous substances as its , principal element, the
principal threat at the properties will be addressed. Treatment
was determined to be impracticable based upon effectiveness,
technical feasibility, implementability, and cost factors.
~NL-
~ Robert L'-1:>uprey, Director
~~ Hazardous Waste Management
l!l9lGs
Date
Division
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