PUBLIC HEALTH ASSESSMENT
SHERWOOD MEDICAL COMPANY
NORFOLK, MADISON COUNTY, NEBRASKA
Figure 5. Location of Two Ground Water Plumes
Figure 6. Soil Gas VOC Isoconcentration Map with Select VOC Soil Sample Results
APPENDIX B - RESPONSE TO PUBLIC COMMENTS
ATSDR released a draft of this public health assessment for public comment on May 22, 1995. The public comment period ended on June 30, 1995. ATSDR received comments on the draft public health assessment from Sherwood Medical Company, in a letter dated June 29, 1995, and from the Nebraska Department of Environmental Quality, in a letter dated June 28, 1995. The comments received and ATSDR's responses are detailed below.
Comments from Sherwood Medical Co.
General Comments
| 1a-1. | "The Assessment of Potential Health Implications for Park Mobile Home Court Should Use
Only Properly Controlled Data from Before the Installation of the Alternative Water Supply
Although the Draft Assessment notes that EPA installed a carbon water treatment system
there by February 1988,...the Draft Assessment uses sampling data from the PMHC wells
from after February 1988 to calculate potential health implications...the use of post-February
1988 sampling results misleadingly exaggerates the health implications, if any, from that
exposure pathway. Consequently, Table 10a. and the calculation of potential health
implications should be revised to include only the sampling data from February 1988, before
EPA installed the carbon treatment system at PMHC." |
| Response: ATSDR agrees that some sampling data from the PMHC wells after February 1988 do
not represent the actual contaminant levels to which PMHC residents were exposed since some of
the data do not take into account contaminant removal by the EPA temporary carbon treatment
system. Therefore, ATSDR has modified Table 10a to include only the following sampling data: 1)
pre-February 1988 data from samples collected from the PMHC wells themselves (i.e., untreated
water samples), and 2) post-February 1988 data from samples collected after treatment by the
carbon treatment system. These sampling data are more representative of the levels of contaminants
to which PMHC residents were exposed via their drinking water. |
|
| 1a-2. | "...[T]he Nebraska Department of Health (NDOH) sampling data from the PMHC wells in
October and November 1987 should not be used in Table 10a. and the potential health
implications analysis because they were not obtained pursuant to level III to V Quality
Assurance/Quality Control (QA/QC) protocols for health assessments as required by the
ATSDR guidance 'Environmental Data Needed for Public Health Assessments,'...Similarly
the [ATSDR Public Health Assessment Guidance] Manual explains that only level III to V
data may be used for risk assessment,...and states that '[d]ata evaluated and used to make
health assessment determinations for hazardous waste sites must meet QA/QC criteria.' The
February 1988 analyses from the PMHC wells are the only Level III data available for the
period prior to the installation of EPA's carbon treatment system, and thus, they are the only
data that should be used to calculate whether there were any health implications..." |
| Response: ATSDR believes that the 1987 NDOH sampling data are appropriate for inclusion in
Table 10a and in the analysis of potential public health implications. First, ATSDR disagrees that
the NDOH data were not obtained according to level III to V QA/QC criteria. ATSDR believes that
the NDOH data were at least analytical level III which include non-CLP analyses performed in an
off-site laboratory. Second, even if the NDOH data are below level III, that is, level I or II, the data
could still be included in the public health assessment. Although the ATSDR Public Health
Assessment Guidance Manual (the manual) indicates that data used in the public health assessment
should meet QA/QC criteria, it does not dictate the specific QA/QC criteria and does not require that
the data be of level III or higher. In addition, the manual allows for the use of data which may not
meet appropriate QA/QC criteria as long as the limitations associated with using such data are
indicated in the public health assessment. Furthermore, both ATSDR's health assessment guidance
and EPA's risk assessment guidance support the use of historical data, such as the 1987 NDOH
sampling data, to supplement more current data, such as the EPA RI data. In fact, p. 28 of the EPA
document "Guidance for Data Useability for Risk Assessment (Part A)," April 1992, states
"...historical data of lower quality may be used if the concentrations are confirmed by subsequent RI
analyses." In the case of the PMHC wells, the VOC concentrations reported by NDOH in 1987 were
confirmed by later EPA RI samples. For these reasons, ATSDR believes that the 1987 NDOH data
are appropriate for use in evaluating potential public health implications associated with exposure to
VOCs in the PMHC wells. |
|
| 1b. | "The Draft Assessment Overestimates the Time of Exposure at the PMHC The Draft
Assessment estimates that contaminants reached the PMHC wells in 1966, and that
consequently, there could have been a maximum exposure to contaminants there of 23 years.
First, it appears that it is based on an inaccurate estimate of the transport rate of contaminants
of 450 feet per year...The RI calculated that the retardation factor for PCE was 9...The RI
calculated the average groundwater flow rate at 900 feet per year, so the average transport
rate for PCE would be 100 feet per year...Similar calculations should be performed in the
final Assessment to accurately calculate the potential maximum time of exposure at the
PMHC wells. Page 36 of the Draft Assessment and the public health implications analysis
should be revised to take into account the shorter period for exposure.
In addition, the 23-year estimate was based on exposure continuing until Sherwood provided
the alternate water supply in September, 1989...The time period for drinking water exposure
should continue only until November 1987, when EPA started supplying bottled water to the
PMHC. In addition, EPA installed its carbon treatment system at the PMHC in February
1988..." |
| Response: ATSDR has reevaluated the maximum exposure period for the PMHC wells based on
information in the Final RI Report (May 1993). According to the Final RI, the average horizontal
groundwater flow velocity at the site is about 800 feet per year and the retardation factor for PCE in
site groundwater is about 1.5. Using these two values results in a PCE transport velocity of 533 feet
per year, which translates to a travel time of 2.7 years for PCE to reach the PMHC wells. Assuming
that VOCs were released at the Sherwood Medical UST area as early as 1963, they could have
migrated to the mobile home park wells by late 1965 or early 1966. This means that residents of the
PMHC could have been exposed to site-related VOCs from late 1966, when the mobile home park
was first occupied, until early 1988, when EPA installed a temporary carbon treatment system on the
PMHC wells. As such, the maximum exposure period for VOCs in the PMHC wells is about 21
years, which is fairly close to the estimate of 23 years in the draft public health assessment. ATSDR
has revised the maximum exposure period in the final health assessment and has factored the revised
exposure period into the public health implications evaluation.
Note: ATSDR does not agree that the exposure period ended in November 1988 when EPA began
supplying bottled drinking water to the PMHC residents. Although most drinking water exposures
to VOCs likely ended at that time, exposure via inhalation of VOCs evaporating from the PMHC
well water during indoor water uses (such as bathing and showering) probably continued until
February 1988 when the EPA carbon treatment system was installed. |
|
| 1c. | "The Conclusion that Past Exposure at PMHC Posed a Public Health Hazard is Inaccurate
The Draft Assessment's conclusion that past exposure to PMHC water posed a public health
hazard is inaccurate...First,..the Draft Assessment's estimate of past risk at PMHC is
overstated...due to the use of sampling data from the period after EPA installed the carbon
treatment system at PMHC, the use of inadequately QA/QC'd data, and the overestimate of
the maximum time of exposure. Second, the chloromethane and chloroform detected in the
PMHC well water are not associated with the release at Sherwood,...and thus, should not be
included in the conclusions regarding the...site." |
| Response: ATSDR has reevaluated the public health implications of past exposures to VOCs in the
PMHC wells in the final public health assessment to account for the revised contaminant
concentrations (resulting from exclusion of post-February 1988 untreated well water data) and the
shorter calculated exposure period (21 vs. 23 years). The new evaluation shows, as did the original
evaluation of the draft assessment, that exposure to VOCs in the PMHC wells represented a past
public health hazard for PMHC residents.
ATSDR disagrees that the data used in the public health assessment were inappropriate because of QA/QC inadequacies (see response to Comment 1a-2). ATSDR also disagrees that sampling data for chloroform and chloromethane from the PMHC drinking water should not be used because those two contaminants are not associated with the release from the Sherwood Medical plant. It is ATSDR's policy to consider all contaminants present at levels of concern in evaluating a human
exposure pathway, even if such contaminants are unrelated to the site. This approach is consistent
with ATSDR's mission "to prevent exposure and adverse health effects...associated with exposure to
hazardous substances..." ATSDR acknowledges that the presence of chloroform and chloromethane
in samples of PMHC drinking water may have resulted from the PMHC's chlorination system (as
Sherwood Medical claims) because these two substances are common by-products of chlorination.
However, because chloroform was found in solid and liquid wastes from the UST/septic tank and in
3 site monitoring wells, and chloromethane was detected in at least one the plant's supply wells, it is
possible that their presence in the PMHC water samples was site-related. In either case, ATSDR
believes that including the data for both chloroform and chloromethane in its analysis of the PMHC
drinking water exposure pathway was appropriate. |
|
| 2a. | "The Sherwood Wells Should Be Eliminated as a Potential Exposure Pathway. ...Sherwood
has always used carbon filtration, either at the wellhead, at the tap, or at the centralized
treatment system, to treat its water. In addition, with the exception of one sample...samples
of that treated water have not detected contaminants...Consequently, the 'Worker Drinking
Water' pathway should be eliminated because exposure to contaminants via that pathway, if
any, was 'extremely unlikely'...In addition, the reference to Sherwood plant drinking water
as a potential source of exposure should be deleted from the Conclusions...for the reasons
explained above." |
| Response: High levels of VOCs, such as 1,1-DCE, PCE, and 1,1,1-TCA, were detected in
Sherwood Medical industrial supply well #5 which, before September 1989, was used as a source of
drinking water for plant employees. Although the water from the plant's supply wells was carbon
treated at the wellhead or at the drinking water fountain, it is likely that some VOCs in the plant's
well water were not entirely removed by the plant's treatment units. Therefore, it is possible that
plant employees were exposed to some level of VOCs in their drinking water before September
1989 when the plant quit using the most contaminated supply wells and installed a modern, high-capacity centralized carbon treatment system. Therefore, ATSDR believes that it is appropriate to
include ingestion of in-plant drinking water as a past potential exposure pathway, even if the actual
levels of contaminants to which employees may have been exposed are not known. By
characterizing the drinking water pathway as a potential exposure pathway (rather than as a
completed pathway), ATSDR is indicating that such exposures could have occurred, not that they
absolutely did occur. In addition, ATSDR does not believe that one negative sample from the plant's
drinking water supply over a period of more than 20 years is sufficient evidence that VOCs were
never present in the plant's drinking water. For these reasons, ATSDR has retained in-plant
drinking water as a past potential human exposure pathway in the final public health assessment. |
|
| 2b. | "Sherwood Lake Should Be Eliminated as a Potential Exposure Pathway...Sherwood
Lake...should be eliminated as a pathway for two reasons. First,...Sherwood has posted its
property, and no trespassers have ever been found in or around Sherwood Lake. According
to the manual, a point of exposure is present only where 'evidence exists that persons had or
still have access to the contaminated medium.'...Here, the evidence is that there has not been
any exposure to children or trespassers at Sherwood Lake...so it should be eliminated as an
exposure pathway.
In addition, a pathway should be eliminated when exposure is 'extremely unlikely.'...That is precisely the case with Sherwood Lake, because of all the samples taken there, only those from 1988 detected low levels of 1,1,1-TCA (31 UG/L and 1,1-DCA (8 UG/L)...Subsequent testing did not detect volatile organic compounds in Sherwood Lake...Given that very low concentrations were detected only one time, Sherwood Lake should be eliminated as a potential pathway of exposure. For both of these reasons, the Conclusion that Sherwood Lake is a potential exposure
pathway should be deleted....In addition, the Recommendation regarding restricting access to
the Sherwood property...should reflect that Sherwood has restricted, and will continue to
restrict, such access." |
| Response: ATSDR agrees that human exposure to VOCs in Sherwood Lake is "extremely unlikely"
since 1) the site is posted, 2) no trespassers have ever been observed on or near the lake, and 3)
VOCs are unlikely to be present in the lake's water or sediments. Therefore, ATSDR has changed
the designation of Sherwood Lake from a potential to an eliminated exposure pathway in the final
public health assessment. In addition, ATSDR has revised the recommendation regarding restricting
access to Sherwood Lake to reflect that the company has posted its property. |
|
| 2c-1. | "In-Plant Areas Should be Eliminated as a Potential Exposure Pathway The Draft
Assessment identifies 'in-plant areas where solvents are used and handled' as a potential
pathway...This should be eliminated as a potential pathway for two reasons. First, the scope
of an ATSDR health assessment is limited to releases of hazardous substances in the
environment...Workplace exposures not related to an environmental release are not within
the proper ambit of an ATSDR health assessment. Second, the Sherwood plant in Norfolk
stopped using 1,1,1,-TCA in 1992, and has not used any chlorinated solvents since that time.
For both of these reasons, the conclusion that Sherwood workers who handle chlorinated
solvents are subject to exposure should be deleted." |
| Response: The purpose of ATSDR's public health assessments is "...to assist in determining
whether actions...should be taken to reduce human exposure to hazardous substances from a facility
and whether additional information on human exposure and associated health risks is needed and
should be acquired.." (42 U.S.C. 9604(i)(6)(G)) and "...to assess any current or future impact on
public health,...and identify...actions needed to evaluate and mitigate or prevent human health
effects" (42 C.F.R. 90.2 definition of 'health assessment'). Therefore, ATSDR believes that it must
consider all human exposures to hazardous substances at a site which may result in adverse health
effects, including exposures by employees or site workers. This is consistent with ATSDR's
mission "to prevent exposure and adverse human health effects...associated with exposure to
hazardous substances..." ATSDR does not believe that it is precluded by the definitions of 'health
assessment' in 42 U.S.C. 9604(i)(6)(G) and 42 C.F.R. 90.2 from evaluating employee exposures
associated with hazardous substances present in their workplace. This is especially true when site
workers or employees are subject to similar substances from multiple exposure pathways. By
ignoring workplace exposures, ATSDR could significantly underestimate a person's total exposure
to one or more substances and the potential health risks pose by such exposure. In addition, ATSDR
must consider workplace exposures to hazardous substances to determine if actions are needed to
reduce such exposures to protect public health.
At the Sherwood Medical site, some workers who used chlorinated solvents in their on-the-job activities were likely exposed to VOCs. This is supported by reports from a former plant employee who described adverse short-term health effects from exposure to chlorinated solvent fumes while working with such solvents. For these reasons, and the reasons discussed previously, ATSDR believes that it is appropriate to include workplace exposure to VOCs as a potential exposure pathway in the public health assessment. However, ATSDR has noted in the pathway discussion that chlorinated solvents are no longer used at the plant, and, therefore, employee exposures to VOCs are no longer occurring. In addition, ATSDR has changed the exposure pathway time-frame from "past/present/future" to "past" only in the final public health assessment. Note: Since the health concerns raised by the former plant worker involved on-the-job exposures
and since chlorinated solvents were still being used by the plant at the time, ATSDR concluded that
the worker's health concerns should be referred to the state agencies responsible for safeguarding
worker health and safety. |
|
| 2c-2. | "[A]n analysis of potential physical hazards unrelated to the release of hazardous substances
is beyond the scope of a Health Assessment. Consequently, the reference to 'potential
physical hazards such as Sherwood Lake and broken glass near the solid waste disposal
bins,'...should be eliminated from the Assessment. Moreover, since Sherwood has posted its
property and trespassers have not been detected at Sherwood Lake, it is inaccurate to
characterize Sherwood Lake or the disposal bins as a potential physical hazard." |
| Response: ATSDR disagrees that its public health assessments cannot include analysis of a site's
physical hazards. As stated in Sec. 3.1.1 of the ATSDR Public Health Assessment Guidance
Manual, "[a]ll aspects of a site's health implications are covered in a health assessment," and
"[p]hysical hazards at a site may constitute a public health concern." In addition, as indicated in Sec.
9.4.4 of the manual, "[i]n some instances, hazards other than those posed by chemical contamination
may be present, including physical hazards (e.g., holes, lagoons, open steel tanks, abandoned
materials, and equipment), special hazards such as the threat of fire or explosion, or hazards endemic
to the site area." Therefore, the health assessment "should contain a brief description of such
hazards and the potential health threat they represent." Furthermore, the following language from
42 U.S.C., Sec. 9604(i)(6)(F) implies that public health assessment may consider health threats
posed by a site's physical hazards: "[T]he term 'health assessments' shall include preliminary
assessments of the potential risk to human health posed by individual sites and facilities..."
ATSDR believes that Sherwood Lake and broken glass near the plant's solid waste disposal bins do
represent minor physical hazards for children who live in houses or mobile homes near the plant.
However, in accordance with the company's comments, ATSDR has added language to the Physical
and Other Hazards section of the public health assessment indicating that the plant property is posted
and that no children have ever been observed trespassing on the site property. |
|
| 3. | "The downgradient industrial/commercial wells are identified as a completed past, present,
and future exposure pathway...The Madison County Weed Control Shop, the Madison
County Maintenance Building, the Civil Defense Building, and the Medelmans and Ohlrich
properties are being provided with alternate water supplies. Accordingly, these wells should
be eliminated as a completed present and future exposure pathway." |
| Response: ATSDR agrees that the five downgradient industrial/commercial wells in question no
longer represent a current or future pathway because these wells are no longer used as a drinking
water source. Therefore, the pathway exposure time-frame has been changed from
"past/present/future" to "past" only in the final public health assessment.
Technical Comments |
|
| 1. | "...Bottled drinking water has been provided to two of the commercial/industrial well owners
(Medelman and Ohlrich) since 1993 and to the remaining three commercial/industrial wells
owners (County Weed, County Maintenance, and Emergency Management) since early
1995. Therefore, the downgradient commercial/industrial well owners and employees are no
longer exposed to drinking water with low concentrations of VOCs...Attached is a revised
version Table 10b with supporting DQO Level III analytical data on downgradient
commercial well water quality..." |
| Response: ATSDR has revised the public health assessment to reflect this information and has
changed the exposure pathway time-frame to "past" only (see response to General Comment 3.) In
addition, Table 10b has been revised to include the most recent (i.e., 12/94) sampling data submitted by the company. |
|
| 2. | "Sherwood Medical has historically carbon treated its well water either at the well head,
drinking fountain point of use, or at a centralized facility treatment system. Prior to 1979,
well. Prior to 1979, well water was treated by several 3,000-pound carbon units on each
well. Beginning in 1979, well water was treated with individual canisters on each of the
facility's drinking water fountains...In September 1989, two, 10,000-pound carbon units
were installed to centrally process all of the facility's well water prior to distribution within
the plant and to the PMHC residents.
The Nebraska Department of Health collected a sample on December 1, 1987 from the
Sherwood Medical water distribution system for DQO Level II VOC analysis. Only one
VOC (1,1,1-TCA) was detected at a trace concentration of 1 ug/l in this sample. These
results help substantiate the fact that Sherwood's well water was carbon treated prior to the
installation of the centralized large carbon treatment system in 1989..." |
| Response: ATSDR has revised the public health assessment to reflect this information. |
|
| 3. | "Sherwood Lake surface water does not constitute a current or future potential exposure
pathway...Prior to September 1989, Sherwood utilized untreated well water, which contained
VOCs, for non-contact cooling water purposes. These non-contact cooling waters containing
low concentrations of VOCs were discharged to Sherwood Lake following use.
With the shutdown of Sherwood wells 4 and 5 in September 1989..., water discharged to Sherwood Lake contains virtually no VOCs...Furthermore, Sherwood discontinued all use of chlorinated solvents at the facility in December 1992. Seven Sherwood Lake 1991 RI water samples contained no detectable concentrations of VOCs. Additionally, there has never been any reported incident where non-plant related personnel have come into contact with Sherwood Lake waters. Therefore, Sherwood Lake should not be considered a current or future potential exposure pathway since two of the exposure pathway elements (contamination and receptors) are not documented to be present. In consideration of the pre-September 1989 use of Sherwood well 5 for non-contact cooling
water and its past effect on Sherwood Lake water quality, Table 5 should be split into two
tables (5a and 5b)." |
| Response: ATSDR has 1) revised the public health assessment to reflect the information regarding
the plant's discontinued use of VOC-contaminated cooling water and the resulting decrease in VOC
levels in Sherwood Lake; 2) separated out the pre- and post-September 1989 sampling data in Table
5 of the health assessment; and 3) eliminated Sherwood Lake as a potential human exposure
pathway (see response to General Comment 2b). |
|
| 4. | "Sherwood has never used trichloroethylene at their Norfolk facility...As a result, TCE was
not detected in either the UST waste liquids, UST solids, or in site soil samples...Therefore,
none of Sherwood's employees have been exposed on the job to TCE since TCE has not
been used at the facility." |
| Response: ATSDR has revised the health assessment to reflect the fact that the plant never used
TCE and to indicate that the former plant employee who expressed health concerns about on-the-job
exposure to TCE may have actually been referring to 1,1,1-trichloroethane (TCA) (which was used
at the plant until 1992). |
|
| 5. | "...Prior to September 1989, wastewater discharged to Sherwood Lake contained low
concentrations of VOCs. Four wastewater discharges to Sherwood Lake were sampled in
1988. The wastewater discharge with the highest concentration of VOCs only contained four
detectable VOCs at low concentrations...
Following the September 1989 discontinued use of Sherwood well 5, wastewater discharged to Sherwood Lake has contained trace to no detectable concentrations of VOCs. Four wastewater discharges to Sherwood Lake were sampled in 1991. Two of the samples had no detected VOCs, while the other two samples had a trace concentration (1 ug/l)... As with Sherwood Lake water quality Table 5, the Table 1c for wastewater discharges to
Sherwood Lake should be split into two tables (1c and 1d)..." |
| Response: ATSDR has revised the public health assessment to reflect the information regarding the
plant's discontinued use of VOC-contaminated cooling water and the resulting decrease in VOC
levels in the plant's wastewater discharges to Sherwood Lake, and has separated out the pre- and
post-September 1989 sampling data in Table 1c of the health assessment. |
|
| 6. | "Carbon tetrachloride has not been documented to be present in the site's groundwater
contaminant plume. The one carbon tetrachloride value cited in this table [Table 3a] is
associated with a water sample which failed QA/QC validation. A duplicate sample
collected from the same monitoring well on the same date which passed QA/QC validation
had no detected concentration of carbon tetrachloride." |
| Response: Carbon tetrachloride was detected in Sherwood Medical supply well #3 in 1990, in the
PMHC main well in 1987, and in monitoring well #8a in 1991. This suggests that carbon
tetrachloride is present, at least to some extent, in site groundwater. The 1991 sample result was
assigned an "E" qualifier indicating that the concentration exceeded the calibration range of the
GC/MS instrument for that analysis. The "E" qualifier does not mean that the data point is invalid,
only that the value may be semi-quantitative. For these reasons, ATSDR is retaining the
concentration value for carbon tetrachloride in Table 3a of the health assessment. |
|
| 7. | "Prior to September 1989, Sherwood Medical rotated operation of facility wells 3, 4, and 5 to
provide the facility's water needs. In September of 1989, Sherwood Medical discontinued
use of facility wells 4 and 5. Sherwood well 3 with well 6 as a backup has provided all of
the facility's and PMHC water needs since September 1989.
Only one of the plant's four industrial supply wells, Sherwood well 5, has been impacted by "high levels" of VOC contamination. DQO Level III water quality information is available for each of Sherwood's facility wells. Some of the information contained in the Draft Public Health Assessment's Table 4 reflect samples which do not meet DQO Level III standards. The best source of water quality information for Sherwood well 5 are seven water samples that were collected during a 72-hour RI pump test. The highest concentration of the three principal VOC constituents detected during the pump test was 870 ug/l of 1,1,1-TCA, 600 ug/l of 1,1-DCE, and 2,300 ug/l of PCE. Attached is a new Table 4b with supporting DQO Level II analytical data on facility
groundwater supply well water quality. In accordance with ATSDR Public Health
Assessment Guidance Manual dated March 1992, the revised Table 4b only incorporates
DQO Level III data." |
| Response: ATSDR has revised the health assessment to reflect the information regarding the
historical use of the plant's water supply wells. In addition, ATSDR has modified Table 4b of the
health assessment to include the sampling data submitted by the company for the plant's industrial
supply wells. However, ATSDR disagrees that only the data submitted by the company should be
used in Table 4a. Rather, ATSDR believes that all data presented in Table 4b are valid and suitable
for use in this public health assessment. (See response to General Comment 1-c.) |
|
| 8. | "...The PMHC well water was chlorinated at the pump house prior to distribution to PMHC
residents. The well's chlorination system had historical operational problems. The presence
of two trihalomethane compounds, chloroform and chlorodibromomethane, in PMHC well
water is solely attributable to the PMHC's chlorination system and is not reflective of the
well's groundwater quality.
One DQO Level III water sample is available for the period of use of untreated PMHC well
water. The key DQO Level III sample was collected on February 2, 1988. The analytical
results for only this sample should be used for public health evaluation purposes..." |
| Response: ATSDR public health assessments consider all contaminants that may pose a threat to
public health, regardless of whether they are site-related. Since both chloroform and
chlorodibromomethane were present above ATSDR's comparison values in the PMHC well water,
they were properly identified as contaminants of concern. ATSDR acknowledges that the presence
of chloroform and chlorodibromomethane in the PMHC well water may have been due to the
PMHC's chlorination system rather than the site's groundwater contamination and has revised the
public health assessment to reflect this information.
ATSDR disagrees that only the February 2, 1988, sampling data should be used in Table 10a of the
public health assessment. As discussed in response to General Comment 1a-2, ATSDR believes that
all data used in the public health assessment are valid and that the quality of the data is adequate for
evaluating the site's public health implications. Furthermore, any QA/QC limitations associated
with specific analytical data are indicated by appropriate data qualifiers in the health assessment
contaminant tables. For these reasons, ATSDR has retained the sampling data obtained prior to
February 2, 1988, in Table 10a of the final public health assessment. |
|
| 9. | "Industrial/commercial wells should not be considered as a completed pathway for the
present or future." |
| Response: ATSDR agrees. See response to General Comment 3 and Technical Comment 1. |
|
| 10a. | "Worker drinking water should be removed as a past potential exposure pathway." |
| Response: ATSDR disagrees. See response to General Comment 2a. |
|
| 10b. | "Surface water should be removed as a present and future exposure pathway." |
| Response: See response to General Comment 2b and Technical Comment 3. |
|
| 10c. | "Other private wells should be removed as a future exposure pathway." |
| Response: ATSDR disagrees. Five private wells downgradient of the plant are currently affected by
site contamination and are part of a completed human exposure pathway. However, several other
private water supply wells are near the plant, both upgradient and downgradient, which could
potentially be affected by groundwater contaminants in the future. If any of these wells do become
contaminated, human exposure to VOCs could occur. Therefore, ATSDR believes that "other
private wells" should be included as a potential future exposure pathway in the public health
assessment. |
|
| 11. | "Plant employees of Sherwood Medical should not be considered as 'exposed' populations." |
| Response: Plant employees are identified as a potentially exposed population in the health
assessment since they were potentially exposed to site contamination. |
|
| 12a. | "The average linear groundwater flow velocity determined during the RI was approximately
900 feet per year (October 1991 Subsurface Exploration Memo, Page 4-9). The RI also
determined that the site conditions effectively yielded a contaminant retardation factor of 9
for PCE due to such factors as adsorption and dispersion (October 1991 Subsurface
Exploration Memo, Page 7-8). Accordingly, the average linear PCE contaminant transport
velocity calculated for the site is approximately 100 feet per year." |
| Response: ATSDR disagrees with the PCE transport velocity calculated by Sherwood Medical. See
response to General Comment 1b. |
|
| 12b. | "Provision of bottled water to PMHC residents in November 1987 constitutes the end of
drinking water exposure to untreated PMHC well water." |
| Response: See "Note" in response to General Comment 1b. |
|
| 13. | "Employees who worked at the Madison County Weed Control and the Madison County
Maintenance Building were exposed to low concentrations of PCE which slightly exceed the
EPA MCL drinking water standard in their work place drinking water for a period of less
than three years. PCE was not present above the laboratory detection limit of 1 ug/l when
these wells were sampled and tested in December 1991. Both wells were resampled in
December 1994 and were found to contain 7.1 and 8.5 ug/l of PCE. The MCL for PCE is 5
ug/l. Bottled drinking water was provided to these two facilities in early 1995. These two
wells have only recently been impacted by the Site's groundwater contaminant plume as it
continues to migrate in a northeasterly, downgradient direction." |
| Response: ATSDR acknowledges that the exposure period for employees who used the Madison
County Weed Control and Madison County Maintenance Building wells may have been as short as 2
to 3 years. However, since historical sampling data for these wells is limited, the actual exposure
period cannot be determined with a high degree of certainty. In any case, since ATSDR's evaluation indicates that exposure to VOCs at the levels found in those two wells did not
pose a health threat, the uncertainty associated with the length of the exposure period is not crucial. |
|
| 14a. | "The total historic time of the PMHC residents should be reduced for the reasons set forth in Comment 14." |
| Response: See response to General Comment 1b and Technical Comment 12. |
|
| 14b. | "Chloroform and chloromethane should not be considered as part of the public health
assessment since these trihalomethanes are the product of the PMHC well's past poor
chlorination practices and are not related to the site's release of VOC groundwater
contaminants." |
| Response: See response to General Comment 1c and Technical Comment 8. |
|
| 14c. | "Carbon tetrachloride, vinyl chloride, 1,1,2,2-PCA, and 1,2-DCA should not be considered
as part of the public health assessment since these VOC constituents were not detected in any
DQO Level III water samples that were collected while untreated well water was still in use." |
| Response: Carbon tetrachloride, vinyl chloride, and 1,2-DCA were detected in the PMHC wells
before the temporary carbon treatment system was installed in February 1988 by EPA to treat the
well water. The sampling data for these contaminants are valid and suitable for use in the public
health assessment. ATSDR could not verify, however, that 1,1,2,2-PCA was detected in the PMHC
wells before the carbon treatment system was in use, and, therefore, has deleted 1,1,2,2-PCA from Table 10a of the final public health assessment. |
|
| 14d. | "Corrected concentration values of the remaining VOCs (1,1-DCE, PCE, TCE, 1,1,1-TCA,
and 1,1-DCA) should be used for public health assessment purposes." |
| Response: As discussed in response to General Comment 1a-1, ATSDR has revised Table 10a of the
public health assessment to include only those VOC sampling data that represent potential drinking
water exposures for PMHC residents. The resulting "corrected" VOC concentrations are presented
in Table 10a of the final public health assessment. |
|
| 15. | "The total noncancer and cancer effects of past exposure to untreated PMHC well water need
to be re-evaluated on the sole basis of DQO Level III data." |
| Response: ATSDR has reevaluated the public health implications of past exposure to VOCs in the
PMHC's drinking water based on the revised contaminant concentrations from Table 10a of the final public health assessment. (See response to General Comment 1c.) |
|
| 16. | "The list of VOCs present in PMHC well water should correspond to DQO Level III data." |
| Response: See response to General Comment 1a-2 and Technical Comments 8 and 14d.
Comments from the Nebraska Department of Environmental Quality General Comment |
|
| 1. | "The document states ATSDR's Health Activities Recommendation Panel has evaluated the
data and information in the assessment and determined no other follow-up health activities
are indicated at this time for three reasons. One of the reasons was many persons who were
exposed to site contaminants over the years, primarily residents of Park Mobil Home Court,
have likely moved away, and therefore cannot be located or contacted.
We suggest this is not a viable reason for the panel's determination. We believe many of the
persons who were exposed that have moved away could be located or contacted. Also, we
believe there may be a number of persons who were exposed to site contaminants over the
years and have not moved away and may be contacted." |
| Response: Since exposure of PMHC residents to VOCs from the PMHC wells ended more than 9
years ago, and since turnover at the PMHC in the past was fairly high, it is likely that many of the
residents who were exposed are no longer living in the PMHC. In addition, many of the current
PMHC residents probably did not live at the PMHC during the 1970s and 1980s when the exposures
to VOCS in the PMHC drinking water supply occurred. Therefore, ATSDR believes it would be
difficult to conduct follow-up health activities with the majority of persons who were significantly
exposed to VOCs from the PMHC wells. More importantly, few persons have expressed any health
concerns related to the site, and ATSDR is not aware of any adverse health effects that have resulted
from past exposure to site contaminants. In light of these factors, especially the last two, ATSDR's
Health Activities Recommendation Panel (HARP) determined that no follow-up health activities
were warranted for the site at the present time. However, as indicated in the health assessment,
ATSDR will reevaluate the need for any follow-up health activities at the site if information
becomes available indicating that human exposure to site contaminants is occurring at levels of
health concern or that past exposure to site contaminants is causing adverse health effects.
Specific Comments |
|
| 1. | "This document states that the Sherwood Medical Company is located approximately 1.5
miles south of Norfolk, Nebraska. It is more accurate to say that the facility is one mile
south of Norfolk because the city limits south end at the Elkhorn River which is less than one
mile north of the Sherwood facility." |
| Response: ATSDR has revised the health assessment to reflect this information. |
|
| 2. | "Page 8, Para. 2, Sentence 3: The document states that the 'river intercepts groundwater
flow but is not considered by EPA to be a hydraulic barrier.' Please indicate if the river is
considered a hydraulic barrier for the health assessment." |
| Response: ATSDR has revised the health assessment to more accurately indicate that it is not
certain whether or not the Elkhorn River is a hydraulic barrier to groundwater movement. |
|
| 3. | "Page 14, Last Para., Last Sentence: The last sentence discusses contamination of surface
soils and appears to introduce circular reasoning into the discussion. This sentence needs
clarification." |
| Response: ATSDR has clarified the paragraph in question. |
|
| 4. | "Page 16, Para. 1, Last Sentence: Include a brief description of why only unfiltered data will be used in the health assessment." |
| Response: ATSDR has revised the sentence in question to explain why only data from unfiltered
samples were used in the health assessment. |
|
| 5. | "Page 23, Last Para., Last Sentence: Explain your rationale for this statement. How are
residual VOCs trapped under the parking lot going to be detected by soil gas analysis as
VOCs in the north leach field area?" |
| Response: The statement in question indicates that VOC-contaminated soil gas found near the
northern leach area could have migrated there from contaminated soil underneath the plant's parking
lot. This statement is reasonable because the impervious parking lot would tend to prevent the
VOCs from being released into the atmosphere and, therefore, force them to travel horizontally
through the soil. |
|
