PB95-963128
EPA/ESD/R08-95/101
March 1995
EPA Superfund
Explanation of Significant Difference
for the Record of Decision:
Denver Radium Superfund Site
(O.U. 4 & 5), Denver, CO
12/7/1994
-------
EXPLANATION OF SIGNIFICANT DIFFERENCES
DENVER RADIUM SUPERFUND SITE
OPERABLE UNIT IV/V
INTRODUCTION
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 September 30, 1986 and the remedy which was implemented at
Operable Unit IV/V (OU IV/V) of the Denver Radium Superfund Site.
EPA is the lead agency at OU TV/V with the support of the
Colorado Department of Public Health and Environment.
/
OU IV/V is located in Denver, Colorado at 500 South Santa Fe
Drive, near the intersection of West Alameda Avenue and
Interstate 25 (Figure 1). The 17 acre site consists of two
properties; the Robinson Brick Company property (OU IV) and the
adjacent Denver & Rio Grande Western Railroad property (OU V) .
OU IV/V is zoned for industrial use.
. - This Explanation of Significant Differences (BSD) describes
changes to the remedy that were implemented at OU IV/V. The BSD
explains 1) how the remedy was modified to address the discovery
of much larger volumes of contaminated soils than were
anticipated at the time of the ROD, and 2) why certain
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, 40 CFR Part 300
(NCP), contains this BSD, the documents that form the basis for
the decision to modify the response action,. and the documentation
relating to selecting a remedy for OU IV/V. It is available for
public review at the following location:
EPA Superfund Record Center
999 18th Street, Suite 500
Denver, Colorado 80202
Hours: M-F 8:00 AM - 4:30 PM
Telephone: (303) 293-1807
-------
This BSD 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 (CERCLA), 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 (NCP), 40 C.F.R. Part 300.
SITE HISTORY
The Denver Radium Site is comprised of over 40 properties
located along the South Platte River Valley that were
contaminated as a result of a radium processing industry that
flourished in Denver during the period from 1915 to 1927.
Production of refined radium produced large quantities of
radioactive waste materials. Generally, these materials were
discarded on-site when the processing facilities were closed.
In 1979, EPA discovered the presence of long-forgotten
radium processing sites. Subsequent field research revealed the
presence of thirty-one radiologically contaminated properties in
Denver. Because of the enormity and complexity of the Denver
Radium Site, EPA divided the Site into Operable Units based upon
site conditions and proximity with other radiologically
contaminated properties.
Industrial activity at OU IV/V began in 1886 with the Bailey
Smelter. The Bailey Smelter appears to have operated only
sporadically in the late 1880's. In -1890, the Gold & Silver
Extraction Company began a cyanide leaching operation. In 1901,
the Bailey Smelter burned down. By 1903, the Colorado Zinc
Company had constructed a mill on the Site of the old Bailey
Smelter. Zinc milling operations continued until about 1910.
From 1914 - 1917, the U.S. Bureau of Mines operated a Radium
processing facility (the National Radium Institute) on Site.
Other industrial activities at the site have included minerals
recovery, manufacturing and servicing of storage batteries,
treating and sacking of metallic ore insulation, oil reclamation,
and landfilling. In 1941, the Robinson Brick Company acquired
13.5 acres of the Site and in 1951 acquired an additional 3.5
contiguous acres and manufactured bricks on the Site until 1980.
The Denver Radium Site was placed on the National Priorities
List (NPL) in September 1983. EPA released a Remedial
Investigation for OU IV/V in April of 1986 and a Feasibility
Study in September, 1986. On September 30, 1986, EPA issued a
Record of Decision (ROD) for OU TV/V. Remedial action began in
May, 1988 and was completed in March, 1991.
-------
SUMMARY OF TEE REMEDY SELECTED IN THE 1986 RECORD OF DECISION
Radium and its associated decay products were the primary
contaminants of concern at OU IV/V. 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. The greater the exposure rate and the longer the
exposure to radiation, the greater the associated health hazard.
Of these three exposure routes, the most significant risk is that
posed by radon gas accumulating in buildings.
, EPA's preferred alternative and the remedy selected by EPA
for OU IV/V was removal;and permanent off-site disposal of
'radiologically contaminated materials. Because a permanent
disposal facility was hot available at the time the ROD was
issued in September, 1986, the remedy included temporary on-site
storage and stabilization measures to be implemented while EPA
and the State of Colorado searched for a permanent repository.
The selected remedy in the ROD entailed:
* Removal of approximately 11,000 tons of radium -
contaminated soil from the site.
* Removal of approximately 200 cubic yards of debris from
the demolition of the contaminated laboratory and
office buildings.
* Disposal of the contaminated soil and debris at a
facility permitted to accept radiologically
contaminated waste.
DESCRIPTION OF THE SIGNIFICANT DIFFERENCES
The significant differences from the 1986 ROD are: (1) the
volume of contaminated soils increased, and 2) relatively small
volumes of contaminated soils were left in place based upon
supplemental standards.
Difference 1. The volume of contaminated soils removed (96,984
tons) was almost nine times greater than the amount estimated in
the ROD (11,000 tons). It was discovered during the remedial
action that the contamination was not located in a single
continuous deposit. It was located in lens shaped deposits which
were layered on top of each other. Between the lenses of
radiological contaminated soils were deposits of soils free from
radiological contamination. Thus, the radiological contamination
occurred deeper than estimated -in.the Remedial-Investigation, 1 ..
resulting in a much greater volume of contaminated soils to be
excavated and disposed at an off-site disposal facility. ; - ei -
-------
Difference 2. Radium and thorium- contaminated soil was left in
place below the groundwater level. . (Figure 2 shows the locations
where contaminated soil was left in place.)
40 CFR Part 192, the primary ARAR identified for the site, .
provides that under specific circumstances the agency performing
the cleanup may choose a remedial action that does not achieve
complete removal of radium contamination to the levels described
in 40 CFR Section 192.12(a). The following are circumstances
under which such "supplemental standards" can be applied (40 CFR
Section 192.21(c)):
"The estimated 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 future hazard. The likelihood that
buildings will be erected or that 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 primary health risk posed by the radium (and thorium
when it degrades to radium) contamination is from the
accumulation of radon gas in overlying structures. Any radon gas
emanating from the contaminated soil below the ground water will
rise to the ground water and will tend to stay in solution.
Since the radon will stay in solution, there will be little risk
of the radon accumulating in overlying structures.
The residual radioactive material that was left in place at
the OU IV meets the criteria for the application of supplemental
standards. The estimated cost to remove the material left in
place is unreasonably high relative to any long-term benefit, and
the residual radioactive materials do not pose a clear present or
future hazard. Institutional controls will be placed on the OU
IV property to assure that interested parties are aware of the
presence of radiological contamination. Institutional controls
may include deed restrictions and special zoning.
-------
Summary of Significant Differences
Original Remedy
1} Excavation and off-site
disposal of 11,000 tons
of contaminated soil
2) Excavation of all
contaminated soil
SUPPORT AGENCY COMMENTS
Modified Remedy
1) About 97,000 tons of
contaminated soil was
excavated for off-site
disposal
2) Small volumes of contam-
inated soil were .left in
place based on supple-
mental standards
The Colorado Department of Public Health and Environment
concurs with the implementation of the remedy presented in this
ESD.
STATUTORY FINDINGS
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.
PUBLIC PARTICIPATION
This ESD will become part of the Administrative Record File
pursuant to Section 300.825(a)(2) of the NCP. The Administrative
Record File is available for public review at the following
location:
EPA Superfund Records Center
999 18th Street, Suite 500
Denver, CO 80202
(303) 293-1807 _. . _
Hours: M-F 8:00 AM - 4:30 PM
-------
EPA
PUBLIC NOTICE .
DENVER RADIUM SUPERFUND SITE
OPERABLE UNIT IV/V - ROBCO
United States Environmental Protection Agency
The U.S. EPA has published an Explanation of Significant
Differences (BSD) for Operable Unit IV/V of the Denver Radium
Superfund Site. Operable Unit • IV/V (OU IV/V) is located in
Denver, Colorado at 500 South Santa Fe Drive, near the
intersection of West Alameda Avenue and Interstate 25. This 17
acre site encompasses two properties; the Robinson Brick Company
property (OU IV) and the adjacent Denver & Rio Grande Western
Railroad property (OU V) . The BSD explains the differences
between the remedy selected in the 1986 Record of Decision (ROD)
and the modified remedy. " ~ •-•,. : " ~ :
*•» • •
The remedy selected in the 1986 ROD for OU rv/V called for the
excavation of approximately 11,000 tons of radium-contaminated
soils and disposal at an off-site facility permitted to accept
such waste. In addition, approximately 200 cubic yards of debris
from the demolition of a contaminated laboratory and office
buildings were to be disposed of off-site.
The modified remedy differs significantly from the remedy
selected in the 1986 ROD in the following ways:
* The volume of contaminated soils removed increased from
the estimated 11,000 tons to a total of 96,984 tons.
* Small volumes of radium and thorium contaminated soil
were left in place below the groundwater level. This
remaining contaminated material does not pose a health
or environmental hazard. .
A copy of the ESD can be obtained by calling the Superfund
Records Center at (303) 293-1807.
A copy of the ESD is available for public review at:
EPA Superfund Records Center EPA Contact Person:
999 18th Street, Suite 500 Rebecca Thomas (303) 293-1538
Denver, CO 80202
Hours: M-F 8:00 AM to 4:30 PM
-------
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION VIII
999 18th STREET - SUITE 500
DENVER, COLORADO 80202-2466
Ref: 8HWM-SR
EMORANDU
TO: Robert L. Duprey, Director
Hazardous Waste Management Division
FROM: Rebecca J. Thomas,
Denver Radium Project
SUBJECT: Denver Radium Superfund Site
Operable Unit IV/V - ROBCO
Explanation of Significant Differences
Attached is an Explanation of Significant Differences (ESD)
between the 1986 Record of Decision (ROD) and the remedy which
was implemented at Operable Unit IV/V (OU IV/V) of the Denver
Radium Superfund Site.
The remedy selected in the 1986 ROD for OU IV/V 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 1986 ROD:
1) the volume of contaminated soils increased, and
2) relatively small volumes of contaminated soils were
left in place (based on 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 described in this ESD.
Printed on Recycled Paper
-------
STATE OF COLORADO
Roy Romer, Governor - PPPETJU
Patricia A. Nolan, MD, MPH, Executive Director j;:- . . ^CUH,} V
Dedicated to protecting and improving the health and environment of the people of Colorado
4300 Cherry Creek Dr. S. Laboratory Building •• .
Denver, Colorado 80222-1530 4210 E. 11 th Avenue
Phone (303) 692-2000 Denver, Colorado 80220-3716
(303)691-4700
November 22,1994 . •
Mr. Robert L. Duprey, Director l
Hazardous Waste Management Division
U.S. EPA, Region VHI
999 18th Street, Suite 500
Denver, CO 80202
Re: Explanation Of Significant Differences, Denver Radium Site, Operable Unit IV/V
Dear Mr. Duprey:
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 the
Explanation Of Significant Differences (ESD) for the Denver Radium Site, Operable Unit
(OU) IV/V.
The ESD accounts for differences between the original Record Of Decision (ROD) and the
remedial action performed. The changes were necessary because 1) the volume of
contaminated materials excavated and removed increased from an estimated 11, 000 tons to
96,984 tons; and 2) relatively small volumes of contaminated materials were left in place,
based on supplemental standards. The contaminated materials which remains in place will
be managed through the use of institutional controls.
CDPHE agrees that the revised remedy remains protective of human health and the
environment, complies with federal and state requirements that are applicable or relevant
and appropriate, and is cost effective.
Sincerely,
Howard Roitman
Acting Director
Hazardous Materials and Waste
Management Division
-------
EXPLANATION OF SIGNIFICANT DIFFERENCES ' ~ ;
RECORD OF DECISION (ROD) - OPERABLE UNIT IV/V
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 1986 ROD, EPA has determined 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. The remedy utilized permanent solutions and
alternative treatment technologies to the extent practicable.
Even though the revised 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.
.fSL/7 ///
i^feo'r ^ Da
7
Robert L.'Dupre^xDire^feol: Date' Y
Hazardous Waste Msmagjnnent Division £
------- |