PB97-963119
EPA/541/R-97/053
November 1997
EPA Superfund
Explanation of Significant Difference
for the Record of Decision:
Toftdahl Drums,
Brush Prairie, WA
6/17/1997
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EXPLANATION OF SIGNIFICANT DIFFERENCES
TOFTDAHL DRUMS, BRUSH PRAIRIE, CLARK COUNTY, WASHINGTON
I. Introduction
Site Name and Location
Toftdahl Drums
Brush Prairie, Clark County, Washington
Lead and Support Agency
U.S. Environmental Protection Agency (EPA) - Lead Agency for the Record of Decision (ROD)
and Explanation of Significant Differences (BSD)
Washington State Department of Ecology (Ecology) - Support Agency for ROD and BSD; lead
agency for post-ROD site work
Statutory Authority
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), Section
117(c) and the National Oil and Hazardous Substances Contingency Plan (NCP), Section
300.435(c)(2)(I).
Purpose
The purpose of this Explanation of Significant Differences (ESD) is to discontinue the long-term
ground water monitoring at the Toftdahl Drums site. All Remedial Investigation and post-ROD
data collected by Ecology demonstrate there is no ground water contamination problem
associated with this site. Continued groundwater monitoring is not needed to ensure protection
of human health and the environment.
Administrative Record
This ESD will become part of a new Administrative Record for the Toftdahl Drum site. The
Administrative Record is located at the EPA Region 10 office in the Superfund Records Center,
7th Floor, 1200 6th Avenue, Seattle, Washington. In addition, a copy of the Administrative
Record is located at the Information Repository hi the Battle Ground Library, 12 West Main
Street, Battle Ground, WA 98604-9449, (360) 687-2322. ,
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II. Summary of Site History, Contamination Problems, Selected Remedy and Post-ROD
Sampling Results.
The Toftdahl Drum site is located four miles east-southeast of Battle Ground, Washington in a
rural residential area. In the mid- 1980's when the ROD was written, approximately 14
residences were located in a 90 acre area. These residences obtained their water from private
wells that were generally screened at least 70 feet below the ground surface. In the 10 years
since the ROD was prepared, many more residences have been built in the general area and all
residences now have access to city water.
In the early 1970's approximately 200 drums containing unknown quantities and types of wastes
were cleaned for resale at the Toftdahl property. Approximately 50 of these drums containing
residual industrial wastes were buried on-site. In 1978 or 1982, approximately 38 drums were
removed from the site by Mr. Toftdahl.
Ecology was first notified about the possible presence of buried drums in 1982. Various site
investigations were undertaken by Ecology and EPA contractors in 1983 and 1984. As a result
of these investigations and uncertainty about the degree of contamination in soil and ground
water, the Toftdahl Drum site was proposed to the National Priorities List (NPL) on October 15,
1984. The listing was made final on June 10,1986.
An Initial Remedial Measure (IRM) was conducted by Ecology's contractor in 1985. Potential
drum burial locations were identified and explored. All drums and visibly contaminated soils
(primarily paint chips) were collected and disposed off-site. Subsequent analysis demonstrated
that none of the materials were RCRA characteristic wastes.
The Remedial Investigation was begun in December 1985 and was completed in July 1986. In
addition to the pre- and post-IRM soil analysis, the RI included two years of ground water
monitoring as well as surface water monitoring. The monitoring program sampled both newly
installed monitoring wells and nearby private residential wells.
As a result of the RI, a ROD was signed on September 30,1986. The remedy selected in the
ROD was no further action to remediate the site because previous Ecology measures had
removed the drums and all significant quantities of wastes from the site. Moreover, the
groundwater and surface water monitoring had demonstrated that there were no current threats
from the Toftdahl Drum site. However, as a precautionary measure, Ecology asked that the
ROD include a requirement for Ecology to sample and analyze ground water samples from
existing monitoring wells and private residential wells semi-annually for five years, and then
annually for ten additional years, subject to funding by the Washington State Legislature.
The Toftdahl Drum site was deleted from the NPL on December 23,1988. No five year reviews
were required as part of the ROD because no land nor ground water use restrictions were
required as part of the ROD. In addition, the ROD was signed prior to SARA.
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As required by the ROD, Ecology has conducted routine ground water monitoring at the site
since 1987, primarily at the domestic water supply taps. Ground water monitoring was
conducted for all priority pollutants semi-annually until April 1991. In April 1993 the analysis
of volatile organics ceased because none had been detected in any of the samples since the RI,
except for one round that detected acetone, a likely laboratory contaminant. Since April 1990,
Ecology's sampling has consisted of annual samples from four domestic water supply taps that
are fed from private wells located near the site. One of these wells (the Boone well) is
upgradient and three of the wells are downgradient of the site. Table 1 summarizes the sampling
results from 1988 through June 1996.
Copper and zinc are the only analytes that have been regularly detected in these post-ROD
samples. Lead and mercury have occasionally been detected. All concentrations have been
below the drinking water standards in effect at the time of the ROD. In addition, all
concentrations are below the State of Washington's primary and secondary maximum
contaminant levels, and the Federal action levels for lead and copper that have been promulgated
after the ROD. The metals have been detected in the same residential water supplies both
upgradient and downgradient from the site for over 10 years and are believed to be related to
well construction and plumbing materials, not site contamination.
Description of the Significant Difference and the Basis for the Difference
Based on Ecology's sampling results and Ecology's request, the ROD requirement for
precautionary monitoring for 15 years after the date of the ROD has been changed to
precautionary monitoring until 1996, or approximately 10 years after the date of the ROD. This
change is based on over 10 years of monitoring data which indicate that no ground water
contamination has been detected in wells potentially impacted by the Toftdahl Drum site. In
addition, given the low levels of contamination that were found at the site in the mid-1980's, it is
unlikely that any source of contamination remains at the site. Accordingly, no further ground-
water monitoring will be conducted at the site. Ecology will ensure that all monitoring wells are
properly abandoned.
Support Agency Comments
Ecology has requested this change to the selected remedy. Ecology has reviewed this BSD and
their suggested changes have been incorporated.
Statutory Determinations
Based on the monitoring data collected since the cleanup action was performed in 1985, EPA has
confirmed that hazardous substances at the site have been removed and that the site is not
contaminating nearby ground water. Therefore, EPA has determined that discontinuing
monitoring at this time is consistent with CERCLA and applicable state law because the site does
not pose a significant threat to public health or the environment and no further response actions
are necessary or appropriate.
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Public Participation Activities
EPA will publish a notice of availability and a brief description of this BSD in the local
newspaper, The Columbian. Ecology will publish a notice of this BSD in the Toxics Cleanup
Program's Site Register. Also, Ecology staff have discussed ceasing ground water monitoring
with the local residents and there have been no objections.
Smith, Director Date
Office of Environmental Cleanup
EPA, Region 10
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Table 1: Summary of Sampling Results from September 1988 to June 1996
Copper
Zinc
Chromium
Lead
All concentrations are in ug/L.
"Smith" samples are duplicated "Kyle" samples.
-: Not analyzed J: Estimated Value ND: Not Detected
U: The compound was not detected at or above the listed numerical value.
B: Analyte was also found in an analytical blank.
P: Analyte detected above the instalment detection limit but below the minimum quantiution limit.
•: Primary Maximum CooUuninant Levels (MCL) are based on chronic and acute health effects.
••: Secondary Maximum Contaminant Levels (MCL) are based on facton such as taste, odor or color.
The primary MCL's listed in this table are those MCLs in effect in 1990. Since then, EPA has established an
action level for lead of 15 ppb (ug/L) and an action level for copper of 1300 ppb (ug/L) in lieu of the Federal
MCLs.
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