PB95-963111
EPA/ESD/R08-93/089
February 1995
EPA Superfund
Explanation of Significant Difference
for the Record of Decision:
Denver Radium Superfund
Site (O.U. 2), CO
9/17/1993
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION VIII
399 18th STREET • SUITE 500
DENVER. COLORADO 80202-2466
Ref: 8HWM-SR
MEMORANDUM
TO: Robert L. Duprey, Director
Hazardous Waste Management
FROM: Dianna Shannon, Chief
Superfund Remedial Branch
SUBJECT: Explanation of Significant Differences to the ROD for
Denver Radium Superfund Site, Operable Unit II -
Du-Wald Steel Corporation
Attached is the final Explanation of Significant Differences
(BSD) between the 1987 Record of Decision (ROD) and the remedy
which will be implemented at Operable Unit II of the Denver
Radium Superfund Site.
The remedy selected in the 1987 ROD for OU II called for the
excavation of radium Contaminated soils to meet cleanup levels
identified in 40 CFR Part 192. Excavated soils were to be
shipped to a permanent disposal facility licensed to accept such
waste.
It became necessary to modify the selected remedy when
elevated concentrations of lead were discovered in .soils and
debris on the Du-Wald property during the design phase of the
radium cleanup. Much of the lead contamination was present in
soils that contained radium-226 in excess of the cleanup levels
identified in the ROD (commingled contamination). . EPA modified
the selected remedy because commingled contamination could not be
placed in the permanent disposal facility without first being
treated to reduce the mobility of the lead component. In
addition, this ESD describes how the remedy was modified to
address the discovery of much larger volumes of contamination
than were anticipated at the time of the ROD, why temporary
storage was not utilized,s; and how radiologic contamination was
left underneath structures and around public utilities on the Du-
Wald property.
The State of Colorado supports implementation of the remedy
-as-proposed -iir this ESD. -in addition, =EPA^ Headquarters-. Jaas-:.-.^
reviewed this ESD and has provided written concurrence to the
Region (attached). I recommend approval of the changes to the
remedy proposed in this ESD.
Attachments
Pflntoo on /wcycwo Popor
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EXPLANATION OF SIGNIFICANT DIFFERENCES
RECORD OF DECISION (ROD) - OPERABLE UNIT II
DENVER RADIUM SUPE~FUND SIT.E
DECLARATION
Considering the new information that has been developed and the
changes that have been made to the selected remedy chosen in the
. September 29, 1987 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, except those
for which a waiver is invoked, and' is cost-effective.. In
addition, the revised remedy utilizes permanent solutions and
alternative treatment technologies to the max~ extent
practicable for this Site. .
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Robert L. Dupr . ector
Hazardous Waste Management 'Division
f/;? /f?
Date
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EXPLAHA'rJ:ON OF SJ:GNJ:FJ:CAH'l' DJ:FP'ERDCES
POR .
SEPTEMBER 29, 1987 RECORD 01' DECJ:SJ:ON
DENVER RADmH SJ:'rB
OPERABLE UNJ:T J:J:
J:NTRODtJ'CTJ:ON
This document explains the significant differences between the
remedy chosen in the Record of Decision (ROD) signed by the U.S.
Environmental Protection Agency (EPA) on September 29, ~987, and
the remedy implemented at Operable Unit II (OU II) of the Denver
Radium Superfund Site located at ~~th Avenue and Umatilla Street,
Denver, Colorado. Specifically, this Explanation of Significant.
Differences (ESD) focuses on contamination that is present 9n the'
Du~Wald Steel Corporation (Du-Wald) property located at ~~OO
. Umatilla Street. BPA is the lead agency for the site and the
Colorado Department of Health is the support agency. .
Under Section ~~7(c) of the Comprehensive Environmental Response,
Compensation, and Liability Act of ~980 (CERCLA or Superfund), as
amended by the Superfund Amendments and .Reauthorization.Act of
1986 (SARA), and Section 300.435(c) (2) (i) of the National Oil and
Hazardous Substances Pollution Contingency Plan (NCP), EPA is
required to publish an ESD when the remedy implemented differs
significantly from that destribedin the ROD. . .
The remedy'selected in the 1987.ROD for OU II called for the
excavation of radium contaminated soils to meet cleanup levels
identified in 40 CPR Part 192. Excavated soils were to be
shipped to a permanent disposal facility licensed to accept such
waste. .
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It became necessary to modify the selected remedy when elevated
concentrations of lead were discovered in soils and debris on the
Du-Wald property during the design phase of the radium cleanup.
Much of the lead contamination was present in soils that
.contained radium-226 in excess of the cleanup levels identified
in the ROD (connningled contamination). The remainder of the lead
contamination present in soils was free of radiologic .
contetmitlCLtion. More commingled contamination was discovered
during the excavation of radium-only contaminated soils in the
southern portion of the Du-Wald property. EPA modified the
selected remedy because commingled,contamination could not be
placed in the permanent disposal facility without first being
treated to reduce the mobility of the lead component. In
addition, this ESD 'describes how the remedy was modified to
address the discovery' of much larger volumes of contamination '.
-...~~ than, were:.. anticipated, at ..the.time. .of "the ;,ROD "'~why;"tempora.ry:"",,,,::,,~';;::'::">-',;3;.:6;.~:;,;,,;,.
storage was not utilized, and how radiologic contetm; na.tion was . . '. '.
left underneath structures and around public utilities on the Du-
Wald property. . , . .'" . ,,'.. - '... - .. . ..
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SUMMARY OJ' SITE HISTORY
The Denver Radium Superfund Site is comprised of 45 properties
scattered 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 ~9~5 to ~927.
Production of refined radium produced large quantities of.
radioactive waste materials. Generally, these materials were
discarded or left on-site when the processing facilities wer~
closed. The Du-Wald property is a~0.5 acre site that is
included within OU II. Radium contamination on the Du-Wald
property is the result of processing activities conducted by the
Schlesinger Radium Company and the Radium Company of Colorado
between ~9~4 and ~923.
The City of Denver owned the. site from ~938to ~948and operated
a municipal landfill' on the southern portion of what is now the
Du-Wald property. In addition to household waste, large
quantities of broken battery casings were placed in the landfill.
Residual lead from the casings mixed with radium contaminated
soils to create approximately 400 tons of commingled
contamination. In the late ~950s and early ~960s, an operation
to reclaim lead from batteries was conducted in the northeast
quadrant of the site (the area surrounding the East Storage
Building). This operation resulted in commingled contamination
as well as lead-only contaminated soils.
. . .
In ~979, EPA discovered the presence of the long-forgotten radium
processing sites. The Denver Radium Site was placed on the .'
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Interim priorities List in October ~98~ and on the National -:.".,-:
priorities List in September ~983. EPA released a-Remedial ~ .~.~
Investigation for OU II in April of ~ge6 and a Draft Feasibility'.:
Study in August of ~987. No Final Feasibility Study was
released. Additional characterization of the radiologic
contamination was conducted during the design of the remedy, and
is dOcumented in Supplemental Data Release for Operable Unit II
by UNC Geotech (December ~988). . The discovery of. non-radiologic'
contamination (primarily lead) on the Du-Wald property prompted
more data gathering which is presented in ftRadiologic and
Selected Metals Assessment of the Du-Wald Steel Corporation.
Property, OU-2ft (UNC Geotech, December ~990).
The Du'-Wald Steel property is located on the corner of ~~th
Avenue and..Umatilla Street and covers ~O. 5 acres. The property
is used as a commercial facility that buys. and sells scrap metal.
Scrap metal is stacked in piles as high as 40 feet over much of
the property. A portion of the property is covered with
reinforced concrete. The topography is fairly level with a . ,
.'~>slight . westerly slope .:'..Two. maj or water conduits.,.::.Denver. Water~::-:~..-,--.~:;";~';.;;:.::.::;;;;L.~
Department Conduit ~2 and Conduit ~8, run east-west across the '
center of the Du-Wald Steel property. Both of the conduits are
approximately five feet deep and carry ~reatedwater for.
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connnercial and resident.ial use. There is another water- supply
conduit running north-south on the eastern boundary of the
property. There are six permanent structures on the Du-Wald
Steel property. These include four buildings, an aluminum scrap
smel ter complex, and one permanent scrap metal crane and shredder
complex. There is approximately 0.3 mile of railroad track on
the property. The riumber of full-time employees on the premises
varies between 35 and 40.
smomRY 01' CONTAKmATION PR.OBLEMS
Lead, radium and radium's associated decay products are the
primary contaminants of concern at the Du-Wald property.
, Radium and its Associated Decav Products
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The Remedial Investigation for the Denver Radium Site estimated
that 15,400 cubic yards (23,100 tons) of radium contaminated'
soils and debris were present on the OU II properties.
Additional characterization data gathered after the signing of
the'ROD resulted in the estimate being revised upward to 80,000
tons. ' , '
The radiologic contamination at the Denver Radium Site 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 tbe 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 on site. Elevated. ,c, '"
, concentrations of radon decay products were detected in the Du- ".
Wald Steel office building during the Remedial Investigation in
1985. ' The observed concentration levels of 0.03 working Levels
in the office building exceeded the .EPA standard of 0.02 Working.,
Levels. 'However, emergency response actions were not taken.
because the patterns of occupancy in the building reduced the
likelihood of significant exposure (i.e. the building was not
occupied on a continuous basis). 'It was thought that removal of
radium contamination adjacent to the office building would reduce
the radon levels inside the office space. Radon testing
completed in 1992 after the remoVal of radium contaminated soils
occurred indicated that the EPA standard was still exceeded'
inside the office building. Thus, a radon mitigation system is
,being installed to reduce radon concentrations to acceptab~e "
levels.within the office building. The other buildings on the
site have very limited.potential for radon aCCUImllation because, "
, :' 'theyare.primarily shops andwarehouses:,'where:,therateq,of':c:7"::---~'C:_'-"~~'""";.,:.~,-,-
exchange between inside and outside air is' high.' ,
.Ground water in the shallow alluvial aquifer on the site contains
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elevated concentrations of uranium, gross alpha and gross beta.
The ground water is flowing off the Du-Wald property in a west-
northwest direction towards the South Platte River. There is no
existing use of the ground water on or downgradient from the
site, and it is expected that the water quality will improve
drastically due to the removal of the radium contaminated soils
on the Du - Wald property. . . .
Lead
. Elevated concentrations of lead 'in soil were present in two areas
of the Du-Wald property: the area surrounding the East Storage
building where the battery cracking operation was conducted; and
an area southwest of the shredder complex that was the site of a
municipal landfill. Seyenty one (71) soil samples were collected
from thirty-six (36) bore holes in the area surrounding the East
Storage building.. OUt' of the 71 samples, . 31 had total
concentrations greater than 1,000 ppm. The highest lead
concentration was 36,600 ppm.
T1?e UNC Geotech report (December 1990) estimat'ed the volume of
lead-only contaminated soil (lead greater than 1,00D mg/kg) .
around the East Storage bu~lding to be 531 cubic yards. In
addition, the total volume of soil with commingled contamination
. (lead and radium) in the. area was estimated at. 609 cubic yards.
At the start of remedial action at the Du-Wald property, it was
thought that lead contamination at the site was limited to the
area surrounding the East Storage building. However, 2800 tons
of commingled contamination. were encountered during the .
excavation of radium contaminated soils in the southern portion
of. the property. The lead component of this conmiingled waste is
apparently associated with. broken battery casings that were
disposed of in a municipal landfill on the property. Toxicity
Characteristic Leaching Procedure (TCLP) results from composite
samples collected in this area were as high aS100,000mg/kg.
Ground water samples from monitoring wells located on the
perimeter of the Du-Wald property were negative for lead.
Therefore, the primary routes of exposure for lead on the.
property are inhalation of lead-contaminated dusts and incidental
ingestion of lead contaminated dusts and soils. .
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SUMKARY 01' THE SELECTED V~Y DI THE 1987 RECORD 01' DBCISION'
The selected remedy in the September 29, 1987 ROD entailed:
1.
Excavating radium contaminated soil from open areas and
:from:.under,the 'buildings; . '., '~'''--:::.-'.- . . "--., "
Placing the excavated material into a temporary land-
storage facility to be constructed on the OU II
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3.
properties;
Maintaining the concrete cap that 'already covers a
portion of the contaminated material on the Du-Wald
property; and
. Removing the estimated 15,400 cubic yards of
radiologically contaminated material from on-site
temporary storage and shipping to a permanent disposal
facility when such. a facility became available.
Plans for temporary on-site storage were abandoned when a
permanent disposal facility was licensed to accept radium waste
in 1988.
4.
. DBSCR:IPT:IOH OP TBB S:IGH:IP:ICAR'l' D:IPPBRBHCBS AND TBB BAS:IS POR.
THOSBD:IP~CBS
The significant differences from the 1987 ROD are: '(1) a greater
volume of radium contaminated .soil was excavated and removed, (2)
relatively small amounts of radium contamination were left on the
Du-Wald property, (3) there was no temporary on-site storage, and
(4) soils containing commingled radium and lead were solidified
in a cement matrix prior to being shipped to the permanent off7
site disposal facility.
Difference 1. Further assessment (UNC Geotech,December.1988 and
September 1990) showed the volume of radium-onl~ contaminated
soil to be almost four times greater (60,000 yd) than the amount
given in the original ROD (15,400 yd3).. .
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Difference 2. Radium contaminated soil was left in place in the
following locations: a) under structures on the Du-Wald
property, b) near the underground power line, c) within a four
foot buffer zone around water' and sewer lines, d) below the
ground water level, and e) on the Burlington Northern Railroad.
. (BNRR) right - of -way. The reasons that radiologic contamination.
was not excavated from these locations are summarized' below.
. .
Contaminated soil was not excavated from under the
Office/warehouse Complex, East Storage building, Southeast
Warehouse Complex, or beneath a one to one slope away' from
the foundations of these buildings. Contamination under a
trUck scale adjacent to the Office/Warehouse Complex was
left in place because it was located within the one to one
slope away from the office. . Excavation of this material .
would have required demolishing and replacing the buildings.
EPA determined that such demolition was not necessary for
=:.:.. -' :;.::..:.:.=~:.::;...-the :-remedy: to-be. protective and. -to.:meet~-:the-:-.interior--.:.cCleanup _:::.;,:;;.. -'-:- ~-:""-.-.
.standards set forth in 40 CPR Section 192.12(b). That
section states that in any occupied or habitable b~ilding:
a)
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1)
The objective of remedial action shall be, and
reasonable effort shall be made to achieve, annual.
radon decay product concentration not to exceed 0.02
WL. In any case, the radon decay product concentration
shall not exceed 0.03 WL, and
The level of gamma radiation shall not exceed the
background level by more than 20 microroentgens per
hour. '
2)
Radon levels and gamma radiation were measured during the
remedial investigation. In the Du-Wald office, the radon
decay product concentration was measuJ;'ed at 0.03 WL. Gamma
radiation did not exceed the background level by more than
20 microroentgens per hour. EPA believed the radon decay
product concentration would decrease as a result of the
removal of radium contaminated soils that were located
inunediately adjacent to the office. However, when EPA
performed radon monitoring after completion of remedial
action, results from this testing indicated that the
standards set forth in 40 CPR Section 192.12(b) were being
exceeded. Therefore, a radon mitigation system is being
installed in.the office building.' .
b)
Ninety-four tons of radium contamination were left in place
adjacent' to a power line'that feeds the'shredder complex.'
The line' could not be turned off without.. forcing the scrap
metal operation to shut down, and it was considered too
dangerous, from a worker safety perspective, to ~cavate -
material adjacent to a nliven power line. The cost of -~~~
rerouting the power line was excessive. . It was decided that ...>-,:
removal of this radium contaminated soil would not result in.
substantially greater protection of public health or the
enviromnent.
c)
The major water lines -and sewer line that cross the Du-Wald
property service large populations in downtown Denver and '
the Washington Park area. The Denver Water Department and
Denver Department of Public Works informed EPA that these
lines were very old and any earthwork conducted near these
lines could cause them to break., Therefore, the decision
was made to leave contaminated material within a four-foot
buffer zone around these utilities.
d)
The 1990 UNC Geotech assessment showed that radiological
, . contamination exists below the ground water table .EPA
decided not to excavate this radium contamination since the
primary health risk posed by radium contamination is from
. .~ the accumulation of radqn;-'gasinu'overlying-structures and'--"-",c"::;:
radon gas in ground water will tend to stay in solution and
not migrate upward to the surface. '.
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e)
Small amounts of surface radiologic contamination were left
in place on the BNRR right-of-way that lies immediately east
of the Du-Wald property. The decision to leave this
contamination was made because the large volume of train
traffic on this main line severely restricted access for
performing cleanup work. It is highly unlikely that
buildings will ever be erected on the right-of-way or that
individuals will spend significant amounts of t~enear the
contaminated area. Therefore, the removal of contamination
from the right-of-way would not have resulted in the remedy
being significantly more protective.
40 CFR Part 192 provides that under certain 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). Under 40 CFR
Section 192.21(c), "supplemental standards" can be applied when:
"The estimated cost of remedial action to satisfy 40 '
CFR Section 192.12(a) at a .0. 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 t~e 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 £rom 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 foun~tions."
The residual radioactive material that was left in place at the
Du-Wald property meets the criteria for the application of "
supplemental standards. A preliminary endangerment assessment
prepared ,by EPA for the Du-Wald propertyin September of ,1992'
determined that leaving contaminated material in the ' ,
aforementioned places would not pose a significant hazard to
human health or the environment. Detailed maps showing the
location and estimated volume of the radium contamination that
remains, on the Du-Wald site will be prepared and distributed to
interes,ted parties so that, any agencies or individuals who
conduct maintenance or excavation activities on the property 'will
be aware of the presence of radiologically cont~minated '
'materials. " Institutional-~:controls w,ill be placed on this. .
property to assure that interested parties are aware of the
presence of radiological contamination on the Du-Wald site.
Institutional controls may include deed re~trictions and special
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zon~ng.
Difference 3. Onsite temporary storage of excavated contaminated
material was not required since a permanent offsite disposal
facility became available before excavation began. . The material
.Was shipped by rail .to the Envirocare of Utah, Inc. disposal
facility in Tooele County, Utah. .
Difference 4. Much of the commingled radium/lead contaminated
soil discovered on the Du-Wald property was RCRA characteristic
waste, as defined by the toxicity characteristic leaching
procedure (TCLP). EPA land disposal restrictions prohibit the
placement of such waste in a land disposal unit unless the waste
is treated to remove the characteristic that makes it a RCRA
waste. Therefore, EPA a~sembled a treatment plant on the Du-Wald
property and solidified approximately 2,800 tons of commingled
contamination. in a cement matrix. .Once solidified, the
contaminated soil, which no longer exhibited the RCRA
characteristic, was shipped to the Envirocare facility.
S''"'''''ary of Significant Differences
Oriqinal Remedy
Modified Remedy
1.
Excavation of 15,400 yd3
of radium contaminated soils
1.
2.
Excavation of all
radiologically contaminated
soil .
2.
3.
Temporary on-site storage
of contaminated material
and . removal to permanent
disposal facility when one
becomes available
4.
Soils containing commingled
contaminants not addressed.
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Over 60,000 yd3 of radium
contaminated soils
excavated
3.
No excavation of
radiologically
contaminated soils
- under buildings
- under shrsdder's feeder
- near utility lines .
- below ground water
on railroad right-of~
way
No temporary storage
prior to removal to
permanent disposal
facility .
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4. .
Solidification of soils
containing commingled
contaminants prior to
removal to per.manent .
. disposal facility
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SUPPORT. AGENCY COMMBN'l'S
The State of Colorado concurs with the implementation of the
revised remedy presented in this ESD.
STA'l'tJTORY DBTERMDTATJ:OHS
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 Health 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, preference for treatment
was given, and is cost-effective. In addition, the revised
remedy utilizes permanent solutions and alternative treatment
technologies to the max~ extent practicable for this site.
PUBLIC PARTICIPATION
This ESD will become part of the Administrative Record File
pursuant to Section 300.825(a} (2) of the NCP. TheAdministrative
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
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