Submitted to
Congresswoman Jane Harman
by
Perry L. McCarty
Department of Civil and Environmental Engineering
Stanford University
and
Yoram Cohen
Chemical Engineering Department
University of California, Los Angeles
DRAFT REPORT
March 25, 2002
REPORT OF INDEPENDENT PANEL ON KENWOOD AVENUE
DDT-CONTAMINATED SOIL REMOVAL ACTION
TABLE OF CONTENTS
1. INTRODUCTION 2
2. REVIEW PROCESS 3
3. SITE CHARACTERIZATION 3
3.1 SOIL CONTAMINATION 3
3.2 GROUNDWATER CONTAMINATION 5
4. POTENTIAL EXPOSURES TO DDT AND HEALTH RISK IMPLICATIONS: PAST AND PRESENT
7
4.1 CONTAMINATED SOIL ALONG KENWOOD AVENUE 7
4.2 GROUNDWATER 8
4.3 COMMUNITY HEALTH STUDY: IMPLICATIONS FOR EXPOSURE
TO DDT PRIOR TO REMEDIATION 8
5. WAS REMEDIATION NECESSARY? 10
6. WAS THE LEVEL OF PROPOSED REMEDIATION REASONABLE AND PROTECTIVE? 11
6.1 SUBSURFACE SOIL REMEDIATION CRITERIA AND REMEDIATION STANDARDS 11
6.2 EXPOSURE TO DDT DURING REMEDIATION 12
7. SUMMARY OF RESPONSE TO QUESTIONS POSED
BY CONGRESSWOMAN JANE HARMAN 14
APPENDIX: DOCUMENTS LIST 17
REPORT OF INDEPENDENT PANEL ON KENWOOD AVENUE
DDT-CONTAMINATED SOIL REMOVAL ACTION
1. Introduction
This report summarizes the results and conclusions of an independent panel convened
by U.S. Congresswoman Jane Harman on December 13, 2001, to perform an independent
review of EPA's Kenwood Avenue DDT Removal Action. The panel members selected
for this review are Dr. Yoram Cohen, Professor of Chemical Engineering, University
of California, Los Angeles, and Dr. Perry L. McCarty, Professor Emeritus of
Civil and Environmental Engineering, Stanford University. Kenwood Avenue is
a residential community located near the former Montrose Chemical Company site
in Los Angeles, which operated from 1947 to 1982, producing about 1.6 billion
pounds of DDT. Up until 1963 the Stauffer Chemical Company also operated a small
plant on the Montrose site, producing benzene hexachloride (BHC), another pesticide.
Because of widespread contamination of soils and groundwater in the vicinity
caused by Montrose and other industry in the area, the area surrounding the
plants has been placed on the National Priority List for cleanup under the Superfund
Act.
As part of the remedial investigation to determine the nature and extent of
contamination, the U.S. Environmental Protection Agency (USEPA) commissioned
a study of DDT distribution in soils in the neighborhood near the Montrose site.
The report completed in March 2000 concluded that elevated concentrations of
DDT and low levels of chlorobenzene were present along Kenwood Avenue and recommended
that additional soil samples be collected there and that the source of the DDT
contamination be determined. A subsequent study completed in April 2001 suggested
high levels of risk from DDT contamination of soils existed to residents living
on the west side of Kenwood Avenue and recommended a cleanup action be undertaken.
The removal action commenced on July 24, 2001. During the removal action, high
DDT concentrations were found in white layers about 3 to 4 feet below ground
level. Due to concerns by the community over potential adverse health implications
of these high DDT levels, Congresswoman Harman was contacted by community members,
and as an outcome, the review panel was formed.
The questions posed by Congresswoman Harman to the review panel were:
1. How reliable is the existing data and is there a need for further soil sampling?
2. Is DDT the only contaminant of concern on Kenwood Avenue?
3. What is the likelihood of residents' exposure to unhealthy contaminants before,
during and after the removal action?
4. Has the site been appropriately characterized?
5. Does the current health risk assessment adequately characterize the on-site
risks given the information now available?
6. In light of the discovery of the "white layer", what is the appropriate
mitigation action, ranging from cleanup to permanent relocation?
The above questions are addressed in the various sections of this report with
a specific concluding summary of the responses provided in Section 7.
2. Review Process
The panel visited the Kenwood Avenue site on December 11, 2001, and met with
EPA representatives and members of the Del Amo Action Committee, a community
group, to learn more about the site and to view the ongoing remediation. Numerous
reports prepared for EPA by contractors and others sent by the Del Amo Action
Committee were reviewed. A listing of these documents is given in the Appendix.
The Panel requested additional reports for further information, which are also
listed in the Appendix. After independently reviewing the reports, the panel
members met at UCLA on March 12, 2002, to summarize their findings and to begin
preparation of this report.
3. Site Characterization
3.1 Soil Contamination
In order to assess the reliability of information reported by the USEPA regarding
the extent of contamination in the Kenwood Avenue area, the review panel first
considered the site characterization data reported by the USEPA. During Phase
I of the Remedial Investigation 350 samples were taken from a 30-square block
area southeast and southwest of the former Montrose plant property. In addition,
70 samples were taken from reference or background areas located several miles
away from the former Montrose plant. Samples were analyzed for the various forms
of DDT, isomers of benzene hexachloride, and chlorobenzene, the contaminants
most likely to originate from Montrose Chemical Plant operation. Some samples
were analyzed for a broader range of potential organic contaminants, but all
of these were taken from drainage pathways associated with the Del Amo Pits
area, rather than the Kenwood Avenue area. This initial investigation revealed
that several residences along the west side of Kenwood Avenue had DDT levels
that were significantly above background levels. Samples from the east side
of Kenwood Avenue did not reveal elevated DDT concentrations.
Soil samples not in the Kenwood Avenue corridor revealed average DDT concentrations
of 1.8 ppm and 10 ppm at the 95 percentile. Background sampling revealed average
total DDT concentrations of 1.2 ppm for 91% of the soil samples and 6-8 ppm
at the 95 percentile. An extended Phase I study of the 20723 Kenwood property
revealed significant DDT concentration in the first 2-4 ft of soil (up to 338
PPM) of some properties with an estimated lifetime cancer risk of 2x10-4 and
a hazard index (for non-cancer effects) of 10(values above 1 indicate a hazard
exists). The USEPA believed that the higher levels of DDT were associated with
a former drainage ditch on the west side of Kenwood Avenue.
In order to further evaluate the high DDT concentrations found along Kenwood
Avenue, a Phase II investigation was undertaken. The Phase II investigation
included collection and analysis of more than 1000 samples from 300 borings
taken around the location of the former Kenwood ditch and estimated ponding
areas, usually located within 25 ft of the edge of the street, and from residential
yards. Samples were analyzed for total DDT, as well as for all isomers of benzene
hexachloride (BHC) and chlorobenzene. Samples were generally taken at depths
of 0.5 ft, 2 ft and 4 ft, and also down to 6 ft along the storm drainage pathway
and flooded areas. Significant concentrations of BHC and chlorobenzene were
not found. About 16 residential yards out of 23 had soil DDT concentrations
above 17 ppm and 4 yards had DDT levels above 1000 ppm. . According to the USEPA,
an average concentration of 17 ppm DDT in soil constitutes a 10-5 cancer health
risk. Of the 1000 total samples analyzed for total DDT, 11% had concentrations
above 17 ppm and 0.4% of the samples were above 1000 ppm. The majority of the
high concentrations were detected at a depth of 2 ft, and concentrations at
2 ft and 4 ft were generally higher than in the immediate soil surface region
(0-0.5 ft).
The sampling results showed that there was a statistically significant difference
in the mean concentrations of total DDT between surface soil along the Kenwood
Avenue drainage area and the surrounding neighborhood. Total DDT in collected
samples reached no higher than about 7 ppm in 90% of the samples, but significantly
higher concentrations of up to about 6727 mg/kg soil were found in the drainage
pathway (20519-23 S. Kenwood Avenue, depth greater than 3 ft). Generally the
highest concentrations were found at depths of 2 ft or greater. The USEPA contractors
sampled the yards of all houses along the west side of Kenwood Avenue stretching
from 204 Street to Torrance Boulevard. Sampling was done by dividing the yards
into 10'x10' cells.
During the remediation phase of the property at 20713 S. Kenwood Avenue, a 1-3
inch thick white layer was encountered at a depth of approximately 4.5 ft. This
white layer extended laterally to the southern boundary of 20709 Kenwood Avenue.
The DDT concentration in this white layer was reported to be as high as 173,000
ppm (or 173 g/kg soil). A white layer of a few inches in thickness was also
uncovered in the front yard of 20523 S. Kenwood Avenue. This white layer, which
extended laterally to the property at 20531 S. Kenwood Avenue, was determined
to have a total DDT concentration of about 35,000 ppm (or 35 g/kg soil). An
additional white layer was discovered in the front yard of 20437 S. Kenwood
Avenue at a depth of 3 feet below street grade (or 5-6 ft below the yard grade).
This white layer was a few feet wide with measured DDT concentration of 97,000
ppm (or 97 g/kg). Monitoring of DDT concentrations above and below the white
layers indicated that these layers were localized.
One should also recognize that the history of the Del Amo/Montrose industrial
area and the Kenwood area is extremely complex. Soil was moved around the area,
during the construction of the Kenwood drainage channel and by the community
in the course of the development of the Kenwood neighborhood (e.g., neighbors
raising their front yards above street level and construction and renovations
of residential dwellings). Therefore, it is not possible to precisely determine
all of the causes of DDT migration in the Kenwood Avenue area. It is important
to note that, based on the distribution of DDT concentrations of over 1000 soil
samples from the Kenwood Avenue corridor one should expect, based on a log normal
distribution, that in the process of soil removal some "hot spots"
containing over 100,000 mg total DDT/kg soil would be discovered. However, the
amount of soil represented by the "hot spots" is expected to be a
relatively small fraction (0.1% to 0.01%) of the total soil in the Kenwood Avenue
corridor.
3.2 Groundwater Contamination
Groundwater is contaminated with Non-Aqueous Phase Organics (both lighter than
water and denser than water organics) at both the Montrose and Del Amo sites.
Groundwater contamination by twenty-eight different chemicals was found at the
joint Del Amo/Montrose sites. Among the detected chemicals were chlorobenzene,
benzene, ethylbenzene, naphthalene, DDT, parachlorobenzene sulfonic acid (p-CBSA),
chloroform, trichloroethylene (TCE), and perchloroethylene (PCE). However, chlorobenzene,
benzene, TCE, and p-CBSA are the most widely distributed of the detected contaminants.
At the Montrose site groundwater is contaminated with chlorobenzene and trichloroacetaldehyde
(choral) both used in the process of DDT manufacturing. The dense non-aqueous
phase liquid (DNAPL) present at the Montrose site contains chlorobenzene in
DNAPL form with concentration levels up to 400 ppm in groundwater. Contamination
by benzene is up to its solubility limit and TCE groundwater concentration is
up to 9.4 ppm were detected at the joint site. Groundwater is also contaminated
with p-CBSA with concentration levels as high as 110,000 ppb. At the Del Amo
site, groundwater is contaminated by both benzene and ethylbenzene. Perchloroethylene
(PCE) and trichloroethylene (TCE) have also contaminated the site. It is noted
that TCE was not found off the immediate areas of the former Montrose and Del
Amo industrial facilities. It is believed that other facilities, including the
Jones Chemical facility, may have also contributed to contamination by chlorinated
solvents.
Based on monitoring of groundwater, it is reported that the DNAPL has penetrated
down to about 200 feet. Chlorobenzene has migrated laterally up to 3 miles in
five successively deeper aquifers. Dissolved chlorobenzene has migrated up to
1.3 miles from the former industrial plant. The USEPA also reports that benzene
is believed to be trapped in the unsaturated zone near and under the water table
under the former Del Amo plant property. The mixed groundwater contamination
plume is reported to extend under the Kenwood Avenue area. The concentrations
of several of the groundwater contaminants greatly exceed USEPA and State of
California drinking water standards. However, this contaminated groundwater
is not currently used by the Kenwood Avenue residents, nor by any other communities,
as a source of drinking water supply. Use of such contaminated water is not
permitted by State of California regulations.
Under the Superfund Act, the USEPA proposes to remediate the contaminated groundwater,
and the remedial investigation is underway. The currently proposed treatment
would contain the DNAPL and LNAPL (low density non-aqueous phase liquid) back
to the industrial properties, but the removal of the high groundwater concentrations
under Kenwood Avenue will take an estimated 50 years. P-CBSA has migrated further
than the chlorobenzene plume reaching concentrations of about 500-1000 ppb at
the "toe" of the chlorobenzene plume (defined at 70 ppb). It is noted
that EPA does not propose to shrink or capture the p-CBSA plume. EPA proposes
to adopt the limit of 25,000 ppb for re-injection of p-CBSA into the ground,
based upon a California provisional NOEL (no observed effect limit) of 1 mg/kg/d.
4. Potential Exposures to DDT and Health Risk Implications: Past and Present
4.1 Contaminated Soil along Kenwood Avenue
Monitoring of soil and groundwater in the Montrose and Del Amo facilities revealed
the presence of twenty-eight different contaminants. The contaminants consisted
of volatile organic solvents (e.g., benzene, chlorobenzene, TCE and PCE) and
other low volatility species (e.g., DDT). The concentrations of volatile organics
(which does not include DDT) in the Kenwood Avenue corridor were below the level
of concern within the first several feet of the surface, although high concentrations
were found in groundwater in the vicinity of the former Montrose and Del Amo
industrial sites. Based on past history it is known that there have been a number
of chemical manufacturing facilities in the area and it is known that there
was direct disposal in open pits and discharges to the sewer and ocean dumping.
Unfortunately, given the lack of sufficient historical data it is not possible
to quantify the potential for past exposures to hazardous chemicals by residents
in the area. However, given that there were chronic discharges of contaminants
from the Montrose and Del Amo industrial sites it would not be surprising if
occupational exposures did occur at elevated levels. The high DDT levels in
soils along Kenwood Avenue represent one part of this legacy. Fortunately for
residences, the industrial activity is no longer present, and if it were, present
laws would prohibit the hazardous practices common with past operations.
Past accumulation of DDT in vegetables and animals due to contaminated soils
would have probably occurred to some degree as verified from monitoring of chicken
meat and eggs and vegetation in the area (prior to remediation). With the removal
of contaminated soil from areas where exposure can occur, the impact of such
exposure pathways would be reduced to acceptable levels as per the criteria
set by the USEPA. It is important to note that, at the present time, significant
portions of the Kenwood corridor area are paved (roads, sidewalks, driveways)
and sampling data from soil under these areas are lacking. Therefore, the possibility
of subsurface soil contamination in such areas cannot be discounted. However,
the paved areas constitute a barrier to volatilization and in the case of DDT
(a low volatility chemical with vapor pressure of 0.025 mPa at 25oC and aqueous
solubility of less than 1 mg/L), migration of DDT upwards would not be significant.
Therefore, the paved areas are not likely to pose a serious inhalation or dermal
exposure threat from contaminants such as DDT. The review panel also notes that
there is a significant volume of contaminated soil stored at the former Montrose
site. The presence of contaminated soil piles, in the vicinity of residential
neighborhoods, is not a palatable solution from the viewpoint of the residents
of the area and a relocation of this stored contaminated soil to permitted landfills
would be desirable. The USEPA indicates removal or treatment of this contaminated
soil is in their near-term plans.
4.2 Groundwater
EPA believes that at the present time, the contaminated groundwater does not
pose a present environmental health risk provided that the contaminated aquifers
are not used as water drinking source or potable water source. Health risk to
individuals drinking the contaminated groundwater would be extremely high. Therefore,
EPA is proposing a remediation strategy that will focus on containment of the
NAPL in the immediate location of the joint sites and cleanup of benzene, TCE
and chlorobenzene from groundwater outside the containment zone to drinking
level standards, a process that may take 50 years or more. Notwithstanding EPA's
conclusion, the residents may be at risk if the groundwater is used for either
drinking or potable water use. This is not permitted under State of California
regulations. Therefore, in order to provide adequate protection to the residents
now and in the future, strict advisory and institutional controls will be required
to ensure that residents do not inadvertently use the groundwater from the contaminated
groundwater aquifers for either drinking or potable water use.
4.3 Community Health Study: Implications for Exposure
to DDT Prior to Remediation
In an effort to assess the health status of the community members living in
the vicinity of the Del Amo/Montrose hazardous waste sites, the Del Amo/Montrose
Community Environmental Health Program (DMCEHP) medical evaluation clinic operated
near the community from January 1995 though January 1998. A total of 596 residents
were seen at the clinic.
The community health study reported that 417 participants had DDT in blood serum
levels of none to 10 ng/mL, 75 participants had DDT in blood serum levels in
the range of 10-20 ng/mL, 46 had levels of 20-50 ng/mL, 13 had levels of 50-100
ng/mL, and 8 participants had levels above 100 ng/mL. The DMCEHP report suggests
that according to the California Department of Health Services (CDHS), 10% of
the US population would be expected to have blood serum levels of DDT higher
than 21 ng/mL (the population 90th percentile reported by CDHS). Accordingly,
in the Del Amo/Montrose health study 56 people would be expected to have levels
greater than 21 ng/mL while the data revealed that 67 people had levels above
20 ng/mL. The study reports that serum levels of DDT/DDE in the community were
generally lower than the US population levels as reported in a 1980 National
survey (NHANES II). The Del Amo/Montrose Community Environmental Health Program
report stated that DDT levels were slightly elevated by current (i.e., at the
time of the study) California Department of Health Services (CDHS) guidelines.
In the community health study, pregnant women who were planning to breast-feed
were not targeted for analysis of DDT in blood serum. The rationale given is
that 81 of the female participants had one or more babies while living in the
neighborhood and none of them had serum DDT levels above 75 ng/mL. Since this
DDT concentration is approximately one-half of the level at which the CDHS recommends
women should not breast-feed (according to the DMCEHP report), it was concluded
that there was no need to target these women for serum DDT level testing. The
appropriateness of not targeting this important sector of the community has
not been adequately explained.
More recent studies (1997-1998), summarized in the ATSDR Toxicological Profiles
for DDT/DDD/DDE (2001), have reported average DDT or DDE concentrations in blood
serum of 4-11 ng/mL and 0.39-6.5 ng/mL for U.S. women (both healthy and hospital
patients) and farmers (in Iowa and North Carolina), respectively. The ATSDR
also reports a range of mean total DDT levels of 15.6-28.8 ng/mL for Great Lakes
fish eaters for the 1982-1989 period. Clearly, there are differences in DDT
and DDE levels among various sectors of the U.S. population. Linking observed
DDT and DDE concentrations with health effects, however, requires a careful
epidemiological study. We note that the Del Amo/Montrose community health study
was neither a risk assessment study nor an epidemiological study. Moreover,
during the operation of the clinic DDT monitoring data were not yet available
to the clinic investigators, thus specific correlation of health observations
with DDT field data could not be made. Therefore, it is not possible to state
whether or not DDT blood serum concentrations for the Del Amo/Montrose community,
relative to other regions in the U.S., were associated with any adverse health
effects. A revaluation of the community health study data, in relation to the
now available DDT monitoring data (prior to remediation), might assist in developing
a more accurate correlation between DDT blood serum levels and DDT field monitoring
data.
5. Was remediation necessary?
The USEPA concluded that actual or threatened releases of hazardous chemicals
found during the Phase II study in Kenwood Avenue area soils may present an
imminent and substantial endangerment to public health, welfare, or the environment.
They thus undertook the soil removal action along the west side of Kenwood Avenue.
Conservative risk analysis estimates based upon data collected during the Phase
II survey suggested an individual lifetime risk in three yards that exceeded
10-4 cancer risk and above a hazard index of 5 for non-cancer effects. The cancer
health risk and hazard index for 12 yards exceeded 10-5 cancer and 0.5 hazard
index, respectively, and for 23 yards the above two risk measurements exceeded
10-6 and 0.05, respectively. The above analysis was based on the assumption
that resident adults and children ingest 100 mg soil and 200 mg soil, respectively,
every day for a period of 30 years, and that all ingested DDT is absorbed into
body. It was also assumed that ingested soil contained the average (mean) total
DDT concentration found in a yard, not the maximum concentration.
Surface soil concentrations of total DDT were at levels (Section 3.1) that could
have posed health risks in a few residential yards if left unremediated. It
must be noted, however, that the highest concentration zones (or "hot spots")
were at depths greater than about 2 ft. Therefore, significant direct exposure
to such soils due to routine contact is unlikely. However, contact with contaminated
soil is possible due to residential construction activities, gardening, and
landscaping. Accumulation of DDT by plants is also possible. Therefore, subsistence
on fruits and vegetables from such contaminated areas could pose elevated risk
relative to background risk levels.
The discovery of the so-called white layer, in the course of excavations, as
part of the remediation process, clearly indicated that there was a need for
remedial action to restore the residential yard soils to a safe level for all
likely future activity, including construction. The presence of the white layer
signaled the possibility of a wider scale contamination. EPA hypothesized that
the white layer is the result of sedimentation of DDT from aqueous waste carried
through the Kenwood channel. If this hypothesis is correct then the "white
layer" is an indication that the channel carried an extremely contaminated
discharge stream. Lateral widespread distribution of DDT away from the channel
zone is less likely to be the result of natural transport of DDT. Some degree
of lateral migration of DDT is possibly due to flooding of the channel. If there
is indeed a wider-spread contamination than revealed by the EPA monitoring,
it could be the results of past disposal practices in the area, possible overflowing
and seepage from open pits in the industrial facilities, as well as spreading
of soil along the corridor by various construction activities.
6. Was the level of proposed remediation reasonable
and protective?
6.1 Subsurface Soil Remediation Criteria
and Remediation Standards
The remediation approach taken by EPA established Tier 1 properties as those
at greatest risk having a total DDT average concentration in excess of 17 ppm
in the surface soil or down to a depth of two feet, an average concentration
greater than 35 ppm over the entire sampling depth, or with any single sample
measuring above 350 ppm DDT. Tier one properties included 1202 West 204th Street,
and residences along Kenwood Avenue with addresses of 20421/20423, 20433/20435/20437,
20519/20523, 20529/20531, 20535, 20603, 20615, 20703, 20709, 20713, and 20723.
The remediation plan called for soil removal down to 2 feet in the areas within
the flood control easement and in all other areas with DDT concentration above
10 ppm.. Soil removal will continue to depths greater than 2 ft but not greater
than 6 feet as long as the concentration is above 10 ppm. The maximum excavation
depth was to be no greater than 6 feet. The USEPA indicated it would be extremely
unlikely that residents or others would excavate and bring soils to the surface
from below this depth. Tier 2 properties were those in which the DDT concentration
criteria did not exceed those of Tier 1. Homeowners in the Tier 2 properties
were offered the option of soil removal within the historical floodplain to
a depth of 2 ft, with a greater excavation (but not deeper than 6 ft) if DDT
concentrations above 10 ppm are discovered. All areas owned by LA County in
which DDT concentrations exceed 10 ppm were to be remediated by removal of soil
to a depth of 2 feet or greater (to a maximum depth of 6 feet) if higher concentrations
were encountered. However, soils in the vicinity of the water main or Kenwood
drain would not be removed.
When the white layer was discovered at the 20713, 20523, 20531 and 20709 Kenwood
Avenue properties, three yards out of the 15 eligible for removal action were
already being excavated. The final number of properties to be excavated was
increased to 25 as a result of the additional investigation. The remedial action
plan was modified as a result of the white layer discovery, requiring that a
check be made of soil down to a depth of 4.5 ft below street level for the presence
of hot spots (i.e., white layer). If additional white layers were found, the
contaminated soil was to be removed except that areas outside residential yards
would not be excavated to a depth greater than 6 feet below yard level. When
the white layer was found at 20531 Kenwood Avenue, fifteen yards out of the
planned 25 had already been excavated. Although the white layer approached the
20709 Kenwood Avenue property, the USEPA reported that it does not have the
resident's approval to remediate that property.
The removal of DDT contaminated soil should alleviate exposure concerns of residents
from activities associated with soil in remediated residential yards down to
a depth of 6 ft. The upper limit permitted for residual soil DDT after remediation
was 10 ppm although in many cases significantly lower DDT clean-up levels were
reached. Exposure to an average DDT concentration of 10 ppm in soil corresponds
to a cancer risk somewhat below 10-5 and a non-cancer hazard index somewhat
below 0.5, based upon the USEPA estimates. The USEPA notes that these levels
are similar to or less than background risks in the south Los Angeles area,
and that at these levels the properties can be used for residential purposes
without restriction. It is also reasonable to expect that any contaminants that
may have been co-mingled with DDT would have also been removed.
6.2 Exposure to DDT during Remediation
During remediation the major source of exposure to DDT would have been from
airborne particulates originating from DDT contaminated soil. The USEPA had
taken steps to relocate residents from properties being remediated during the
course of the soil excavation and removal process. Potential exposure to airborne
DDT laden particulates was of major concern. Therefore, during the remediation
activities USEPA employed real-time monitoring of local meteorology and real-time
particulate (PM10) monitoring. In addition, DDT concentrations were measured
for collected particulate samples. PM10 levels were recorded continuously during
workdays, checked hourly and the results were logged. In the course of excavation
and soil removal, PM10 levels above 50 µg/m3, for a period of 15 minutes,
were set as a limit that would trigger increased dust suppression. Monitors
were located at the front, rear, and at each side of the home being remediated.
In addition integrated DDT samplers were located at the front and rear of each
home. Also, a neighborhood network of five monitoring stations plus a duplicate
station was employed. In addition, Visible Emission Readers were employed during
excavation and handling activities at both the Kenwood avenue area and the Montrose
plant property.
In order to set a conservative protection level, USEPA adopted the California
24-hr ambient air quality standard for airborne particles of 50 mg/m3. PM10
exceedance was defined as 50 µg/m3 over background over a 24 hr period.
As an additional protective limit the USEPA adopted the current noncancer USEPA
Region 9 preliminary remediation goal (PRG) of 1.8 mg DDT/m3 air. Based on the
DDT soil concentration of 6,727 mg/kg, found at the drainage pathway (20519-23
S. Kenwood Avenue, Depth>3 ft), USEPA estimated that the PRG limit would
be reached when the concentration of air particulates, originating from the
above soil, would reach a PM10 level of 268 mg/m3. Therefore, USEPA argued that
the ambient air quality standard of 50 mg/m3 was sufficiently protective. It
is noted, however, that the above estimate was carried out prior to the discovery
of the white layer. If one adopts the highest concentration in the white layer
(173,000 mg/kg soil), then following the USEPA estimation method the PRG would
be reached when the concentration of air particulates (originating from the
white layer zone) would be about 10 mg/m3. Therefore, the California 24-hr ambient
air quality standard (50 mg/m3) may not have been sufficiently protective against
emissions from the white layer. It is recognized that the above approach as
used by the USEPA is conservative when considered over the entire remediation
area.
During the course of excavation and soil removal there were a few episodes of
airborne concentrations above the 50 mg/m3 limit adopted as a protective limit
by the USEPA. None of these episodes resulted in concentrations above a 100
mg/m3. However, analysis of DDT samples did not reveal any concentrations above
the PRG of 1.8 mg DDT/m3 air.
7. Summary of Response to Questions Posed
by Congresswoman Jane Harman
1. How reliable is the existing data and is there a need
for further soil sampling?
During the USEPA Phase II investigation, on the order of 1,000 soil samples
were collected along the path of the former Kenwood ditch and analyzed for DDT,
BHC, and chlorobenzene. This is a sufficient number of samples for the area
covered to evaluate the presence of these chemicals in the soil and to evaluate
the potential risk that they may pose. Sampling was not conducted to determine
the possible presence of other hazardous chemicals, nor is there sufficient
information to judge whether areas along Kenwood Avenue other than that near
the former Kenwood ditch may be contaminated above acceptable levels. Volatile
or highly soluble chemicals are not likely to be of significant concern, as
they would not persist in the upper soil surface region very long. The broad
sampling and analysis program conducted for the Montrose - Del Amo area also
indicates that aerial dispersion of DDT has not resulted in excessively high
soil concentrations of DDT in the area. The potential does exist, however, that
spreading of soil contaminated with DDT could have occurred on some Kenwood
Avenue properties, but data to confirm or refute this is not available.
2. Is DDT the only contaminant of concern on Kenwood Avenue?
The likely soil contaminants in the Kenwood Avenue neighborhood are DDT and
BHC that have poor solubility in water and are essentially non-volatile. High
levels of BHC were not found. The groundwater that lies about 200 feet below
groundwater surface at Kenwood Avenue is highly contaminated with unacceptably
high levels of several volatile and semi-volatile hazardous chemicals, including
chlorobenzene, benzene, and p-CBSA. As long as this water is not drawn for domestic
use by the residents, which is not allowed under State of California regulations,
there is little reason for concern with respect to exposure to this contamination.
The USEPA plans to remediate this contaminated groundwater, but it will be decades
before it is safe for use. As for Los Angeles in general and many other urban
areas, air contaminants of concern do exist, but this air pollution problem
is not specific to Kenwood Avenue residents.
3. What is the likelihood of residents' exposure to unhealthy contaminants
before, during and after the removal action?
There was a high likelihood of residents' exposure to unhealthy concentrations
of DDT before the removal action. Several properties had higher than desirable
concentrations in surface soils where children and individuals who garden could
be exposed. The concentrations in deeper soils were excessive on many properties,
and a possibility existed that construction activities could not only subject
construction workers to excessive concentrations, but also might spread contaminated
soil on the surface, exposing children and others to high DDT concentrations.
The finding of the white layer confirmed that quite unacceptably high concentrations
were present at depth, concentrations that should not be left in place.
During the soil removal action, near residents were provided with the opportunity
for temporary relocation, thus insuring their safety. The main potential hazard
during this time was the possible breathing of DDT-contaminated dust. Monitoring
for air particulates (PM10) and DDT contained in the particulate material indicated
that unacceptably high levels of DDT were not present in air during the removal
action. A few measured air particulate concentrations were higher than the 50
micrograms per cubic meter proposed limit, but the average DDT concentration
in the particulates resulting from removal were not excessive.
The residential areas where DDT has been removed are subject to much less chemical
hazard then they were previously. Since the removed DDT contaminated soil was
replaced with clean-soil, the risk from exposure during normal living or from
construction should be greatly reduced. Removal of soil contaminated with DDT
would also remove other possible hazardous chemicals that may have been associated
with the drainage waters from the former Montrose Chemical site.
4. Has the site been appropriately characterized?
The site has been appropriately characterized as far as DDT, BHC, and chlorobenzene
contamination of soils along the Kenwood drain is concerned. Groundwater contamination
in the area also appears to be adequately characterized to judge the risk it
poses, although this was not the main focus of this review. Little if any detailed
characterization of backyards along Kenwood Avenue appears to have been undertaken,
perhaps because there have been no indications that this area may have received
high levels of contaminants.
5. Does the current health risk assessment adequately characterize
the on-site risks given the information now available?
The health risk assessment was adequately characterized based upon the Phase
II study results. A question that might be raised is whether the characterization
was adequate given the fact that the white DDT layer was found during soil removal.
Had that layer been found during the Phase II study, it is likely to have increased
the estimated risk to owners of properties where this layer was present. It
is not clear how much it would have raised the estimated risk since the calculated
risk is a function of the geometric mean concentration, not the highest concentration
found. Thus, what the risk assessment might have otherwise been depends upon
how many samples were collected and the distribution of DDT concentrations within
those samples. However, the risk is not likely to have been lower, and a plan
for soil removal would have probably been required. Since the white layer was
relatively deep below the surface, the community would not have been exposed
directly to it. The main problem that the white layer posed was to construction
activities that may bring the contaminated soil to the surface.
6. In light of the discovery of the "white layer", what is the appropriate
mitigation action, ranging from cleanup to permanent relocation?
There are various alternatives that could protect the health of residence from
the high DDT levels found along Kenwood Avenue, including soil removal as carried
out or relocation of the residents. Either of these alternatives would have
been protective from the high DDT concentrations associated with the white layer,
as well as from other DDT contamination along the former Kenwood drain. We estimate
that most of the DDT in the removal area was not associated with the white layer,
but with the general overall distribution of higher than normal DDT concentrations
found. Other alternatives, such as capping the yards with an impermeable layer
or in-situ cleanup of the soil are possibilities, but probably would not have
been acceptable options, either to the community or to regulatory agencies.
A less intrusive cleanup, such as removal and replacement of only a surface
layer of soil, and no removal under driveways, could have resulted in some risk
reduction, but probably not sufficient for adequate protection. Another alternative
would have been more complete removal of soil, either removing it to a greater
depth or providing a greater area of removal to reduce exposure even further.
However, such greater removal would have needed further justification because
of the high cost, and by the fact that it would have extended beyond the normal
USEPA guidelines for removal action.
Appendix: Documents List
The following documents were provided by the USEPA or the Del Amo Action Committee, or requested by the independent panel in its review of the Kenwood Avenue DDT Remediation Activities
1. USEPA Memorandum, OSWER Directive No. 9355.7-04, Land Use in the CERCLA
Remedy Selection Process, May 25, 1995.
2. Final Remedial Investigation Report for the Montrose Superfund Site, Los
Angeles, California, Introductory material (Volume I of II; Montrose Chemical
Corporation; as revised by the U.S. Environmental Protection Agency, Sections
1.3 and 1.4. SFUND Records Ctr. No. 0639-04639; AR0008) ; May 18, 1998.
3. Dhont, J., "Remedy Proposed Plan for Dual Site Groundwater Operable
Unit, Montrose and Del Amo Superfund Sites, Technical and Expanded Version,
United States Environmental Protection Agency, Region IX, June 1998.
4. U.S. EPA Superfund Records Center, "EPA Proposes Groundwater Cleanup
Plan," General Fact Sheet Version, June 1998.
5. Baker, D. and H. Yang, "The Del Amo/Montrose Community Environmental
Health Program, Final Report," Center for Occupational and Environmental
Health, University of California, Irvine, December 1999.
6. Completion Report, Neighborhood Sampling Program, Montrose Chemical Superfund
Site, Los Angeles County, California, EPA. Volume I (SFUND Records Ctr. No.
0639-07541, AR0012) and II (SFUND Records Control No. 0639-07542, AR0013). Final
Redacted Versions, Harding Lawson Associates; March 2000.
7. Del Amo Action Committee, DDT and Chicken Eggs from Del Amo Area, May 1,
2000.
8. Del Amo Action Committee, Comments on "Why we need relocation permanently."
June 6, 2001.
9. U.S. District Court, Central District of California, Western Division, United
States of America and State of California v. Montrose Chemical Corporation of
California, October 26, 2000.
10. Action Memorandum, First Amendment: Request for Removal Action for Kenwood
Storm Water Drainage Pathway; Jeffrey Dhont, Environmental Protection Agency-
Region 9; To: Keith Takata, Environmental Protection Agency- Region 9; February
11, 2001.
11. Remedial Investigation Report Addendum, Residential Soils and Produce Investigation,
Montrose Chemical Superfund Site, Los Angeles County, California, Volumes I,
II, III; Harding Lawson Associates. ([SFUND Records Ctr. Nos. 0639-07544, AR0075;
0639-07545; AR0076; 0639-07546, AR0077, respectively); April 2001.
12. Lythcott, M. J., Montrose Superfund Site Final Report, Deliverable #2: Kenwood
Removal Community Situation Analysis, April 10, 2001.
13. Final Response Action Work Plan, Kenwood Storm Water Drainage Pathway, Los
Angeles, California, Volume 1 of 3; IT Corporation; June, 6, 2001
14. Action Memorandum; Request for Removal Action for Kenwood Storm Water Drainage
Pathway, Environmental Protection Agency-Region 9; To: Keith Takata, Environmental
Protection Agency- Region 9. (SFUND Records Ctr. No. 0639-07547; AR0079). June
7, 2001.
15. Ambient Air Monitoring Plan, Kenwood Avenue Storm-water Pathway; IT Corporation;
July 2001.
16. Federal Register, Notice of Lodging of Consent Decree United States, et
al. v. Montrose Chemical Corporation, Vol. 66, No. 150, Page 40724, July 19,
2001.
17. Del Amo Action Committee, Summary of Public Comments concerning consent
decree, August 31, 2001.
18. USEPA, First Amendment to Action Memorandum, Request for Removal Action
for Kenwood Storm Water Drainage Pathway, Montrose Chemical Superfund Site (CAD008242711),
Los Angeles, California, November 2, 2001.
19. Interim Data Binder, Confirmation Sample Analytical Data Maps. USEPA indicated
these data are preliminary. February 6, 2002
20. Interim Data Binder (February 6, 2002) containing the following. USEPA indicated
these data are preliminary.
a. Analytical Results for Air Samples - Detections of DDT and Other Related
Compounds - July 13, 2001 through October 23, 2001 - Kenwood Neighborhood and
residences
b. Analytical Results for Air Samples - July 19, 2001 through October 18, 2001
- Former Montrose Plant Property (where DDT-contaminated soil is brought and
stored following removal from the South Kenwood Avenue neighborhood yards)
c. Summary Table of Daily Average PM-10 Data (collected from Kenwood neighborhood
and each residence during removal activities)
d. Daily Average PM-10 Data Tables and Charts (for individual addresses and
dates - collected during removal activities)
21. Final Confirmation Sample Analytical Data Maps; including field logs and
site sketches for the white seam material, February 2002.
22. Data Binder (February 2002) containing the following:
a. Analytical Results for Air Samples - Detections of DDT and Other Related
Compounds - July 13, 2001 through October 30, 2001 - Kenwood Neighborhood and
residences
b. Analytical Results for Air Samples - July 19, 2001 through October 26, 2001
- Former Montrose Plant Property (where DDT-contaminated soil is brought and
stored following removal from the South Kenwood Avenue neighborhood yards)
c. Comprehensive Chronologic Daily Average PM-10 Data - November 5, 2001 through
December 12, 2001 (collected from Kenwood neighborhood and each residence during
removal activities
d. Daily Average PM-10 Data Tables and Charts - November 5, 2001 through December
12, 2001 (for individual addresses and dates - collected during removal activities)
e. Residential Wind Roses - November 5, 2001 through December 12, 2001
23. Del Amo Action Committee - provided several miscellaneous memoranda, letters,
newspaper reports, community comments, site photographs taken during Kenwood
Avenue remediation, and notes for review by panel.