PRELIMINARY PUBLIC HEALTH ASSESSMENT
10TH STREET SITE
(a/k/a COLUMBUS PUBLIC WATER SUPPLY)
COLUMBUS, PLATTE COUNTY, NEBRASKA
The U.S. Environmental Protection Agency has developed plans to conduct a Remedial Investigation and Feasibility Study (RI/FS) for the Tenth Street Superfund Site in Columbus, Nebraska. The first task for this RI/FS was to prepare a project scoping report to define the limits of the investigation. This task was completed by Sverdrup consultants in January, 1990. Sverdrup will also conduct the remainder of the tasks for this RI/FS. The RI/FS will fill the data gaps related to the groundwater and the physical setting of the site. This will include the installation of monitoring well clusters to identify the aquifers ad direction of groundwater flow and to fully characterize the nature and extent of the contamination. Site boundaries and identification of the potential release sources will be delineated through the use of soil sampling. This site is currently on the Update 10 list proposed for inclusion on the National Priorities List of Superfund sites.
The subject site is located in the business district of the City of Columbus and may be the source of contamination of several of the City's municipal supply wells. The major site contaminants are trihalomethanes (THM), trichloroethylene (TCE) and tetrachloroethylene (PCE). Contributors to the site contamination are speculated to be four dry cleaning establishments, a radiator repair/machine shop, and an unpaved parking lot that previously was a scrap metal yard.
At this stage of investigation, data regarding site contamination are limited. Indicators of site contamination are PCE, TCE, and THM in the City's municipal wells. For individual municipal supply wells, prior to being mixed for distribution, concentrations of TCE and PCE have been found ranging up to 34 and 25 parts per billion (ppb) respectively. Chloroform has been detected at levels ranging from none detected up to 240 ppb at the supply well.
Water from several municipal wells is mixed prior to distribution to the community. Average PCE concentrations in this distributed water ranged from 1 to 5 ppb; average TCE concentration ranged from 6 to 18 ppb. Both PCE and TCE concentrations meet or exceed the Maximum Contaminant Level (MCL) for these chemicals in drinking water. THMs in the distributed water have been reported as "well below" the MCL of 100 ppb.
The City reduced contamination in distributed water by taking the most heavily contaminated individual supply wells off-line. This has helped; however contamination is still detectable and for TCE has exceeded the MCL (6.3 ppb).
On-site soil gas measurement has demonstrated the presence of a plume of TCE and PCE underlying the site. Options under consideration by EPA and the city of Columbus for long-term remediation and mitigation include abandonment of the existing contaminated well-field and development of a new, more remote well-field, treatment of municipal water to reduce contamination levels, and remediation of the suspected source site to reduce contamination of the well field.
The city is continuing monitoring of the municipal wells for the identified contaminants to follow trends in the concentrations. EPA is presently conducting the RI to further characterize the groundwater and the contamination of the ground water and to delineate the sources of the groundwater contamination. It is difficult to assess possible impacts from exposures that may have occurred prior to the contaminants of concern being detected in 1984. There have been no particular health concerns expressed by the community specifically related to the site or the low-level contamination in the water supply.
A review of the 10 leading causes of death indicates an increased rate of death from diseases of the kidney (nephritis/nephrosis) in the city of Columbus when compared to the county and state rates. While the kidney is a target organ for these compounds, this elevated rate cannot be attributed to exposure to the low levels seen in the water supply. This may represent a subpopulation with increased sensitivity to the effects of exposure that must be considered. These health parameters should be investigated further to identify possible risk factors.
Until such time that the RI/FS is completed by EPA, water monitoring should be continued to prevent consumption of contaminated water. The long-term human health effects resulting from chronic exposure to low-levels of these substances is not known at present. Twenty-two percent of the population in the city of Columbus are either under five years of age or over sixty-five years of age. These age groups are potentially more sensitive to the effects of exposure. The population in the city is relatively stable, suggesting the potential for long-term exposures. In view of the potential for long-term exposure, the presence of potentially sensitive subpopulations, and the lack of data on the effects of chronic exposure to low levels of these substances, this site is considered to be an indeterminate public health hazard.
This site has been reviewed by the ATSDR Health Activities Recommendation Panel. While there is evidence that individuals are exposed to low levels of trichloroethylene and tetrachloroethylene, data at this point are very limited. Further information as provided by the site remedial investigation will assist ATSDR in determining any public health actions for the community in the future. ATSDR will review the remedial investigation information as it becomes available.
This public health assessment was released for public comment from July 15, 1991 until August 14, 1991. There were no comments received during this period.
A. SITE DESCRIPTION AND HISTORY
In November 1983, the city of Columbus, Nebraska discovered trihalomethanes (THMs) in the drinking water supply. It is not known whether this was the first time that such compounds were analyzed in the drinking water or the first time that the contaminants actually migrated into the drawdown zone of contaminated municipal wells. Trichloroethylene (TCE) and tetrachloroethylene (also known as perchloroethylene, PCE) were detected in the wells in the following year. These contaminants continue to be detected in the wells and distributed water. The U.S. Environmental Protection Agency (EPA) identified the probable source of ground water contamination in 1988. Soil gas studies conducted by EPA indicated the plume of contamination originated in the city block bounded by Tenth and Eleventh Streets on the south and north, respectively and 24th and 25th Avenues on the east and west, respectively. Possible contributors to the site contamination include four dry cleaners, a radiator repair/machine shop, and a former scrap-metal yard that is presently used as an unpaved, municipal parking lot.
The site, known as the Tenth Street Site, is located in the central business district of Columbus, Nebraska. Columbus serves as the County seat of Platte County, Nebraska, and is located approximately 75 miles west of Omaha in the eastern half of the State. The Loup River, which is located just south of the main portion of the city, flows in a general eastward direction. Nearby, and south of the Loup River is the Platte River which also flows eastward and joins the Loup River several miles east and south of the City. [See Appendix A (figures 1,2,3) or maps of the area.] Seven of the City's nine active production wells used for the municipal water supply are located within 2,000 feet of the site, with the closest at approximately 900 feet from the site. All but one of the seven wells is due west of the site. Well number 2 is west-southwest of the site at a distance of 1,200 feet. (See figure 4 in Appendix A)
To date no site remediation (i.e., clean-up activity) has taken place. Options considered by the EPA and the city of Columbus, for future implementation include abandonment of the existing municipal wells, treatment of the municipal water to reduce contamination levels, and remediation of the suspected source site to reduce contamination of the existing wells. In the interim, the city is restricting use of the contaminated wells and mixing water from the various wells to meet drinking water criteria.
Personnel from the Agency for Toxic Substance and Disease Registry (ATSDR) received a tour of the site and near-by businesses from an employee of the city water department on May 4, 1990. ATSDR visitors included Dr. Virginia Lee and Mr. Harvey Rogers from the Atlanta office and Mr. David Parker from the Region 7 office. The tenth Street site currently shows no overt signs of contamination or continued disposal activities. There were no odors or visible residues or vegetation damage apparent during our visit.
The City of Columbus reported that EPA conducted a well survey to determine the number of private wells near the site. No private wells were reported according to the municipal public works employee conducting the site tour; however, he was not sure since the survey was not done by his department. It was noted in driving in the direction of the well field from the Tenth Street site that at least one residential yard appeared to have a well pump on site.
The Tenth Street site did not have restricted access. The physical hazards present are those associated with a one story building in a business district.
The day before the site visit, the ATSDR staff met with officials from the Nebraska Department of Health and the Department of Environmental Control to review site records and data. Most of the information available had already been reflected in the EPA "Scope Report" previously furnished to ATSDR. We discussed new ground-water sampling data taken in February, 1990.
C. DEMOGRAPHICS, LAND USE, AND NATURAL RESOURCE USE
The business district is largely north of the site, with residential areas located in the other directions. No agricultural activity occurs in the immediate vicinity of the site; however, home gardening in the area is possible.
The population of the city in 1986 was 18,610, which is over 60% of the entire county population. The county is primarily agricultural with 605 of its 669 square miles being utilized by agriculture. There is one 81-bed hospital in the city. (1)
D. STATE AND LOCAL HEALTH DATA
Vital statistics information has been obtained from the Nebraska Department of Health for the city of Columbus and for the state of Nebraska for the year 1988. Census information for the community from the 1980 U.S. Census has been reviewed.
The Riggans Mortality Database have been reviewed to obtain background cancer mortality information for Platte County and the State of Nebraska.
Discussions with state and local officials did not reveal any specific community concerns about the water supply. The ATSDR Regional Representative attended a public meeting in the summer of 1990 for the site. No major community health concerns were raised at that time.
ENVIRONMENTAL CONTAMINATION AND OTHER HAZARDS
The only on-site contamination data were developed for the EPA in 1988 by Ecology and Environment/FIT in a soil-gas investigation. Soil-gas measurements were taken at depths ranging from 3 to 9 feet, with the most of the higher values being found at the 5 foot depth. Soil-gas concentrations for PCE ranged up to about 146,000 nanogram per liter (ng/L) on-site (at 5 feet below the surface). Soil-gas concentrations of TCE were not reported in the data supplied to ATSDR; however, they are reported to be about 1/100th of the PCE concentrations and cover about one third to one fourth as much land area. The soil-gas contamination appears to be spreading southward; although there is some contamination in all directions from the highest level of on-site contamination. Soil-gas contamination does extend westward into the municipal well-field.
In addition to the above-mentioned soil-gas study which addressed both on and off-site soil-gas contamination, the city has collected samples of both individual municipal supply wells and distributed water after blending from the wells. Table 1 summarizes the reported off-site contamination data. This data represents seven years of data collected from 1984 through 1990. Of 79 positive results for organic compounds in the wells sampled, 19 were above the Maximum Contamination Level (MCL) of 5 parts per billion set by EPA for trichloroethylene and tetrachloroethylene. Of 45 positive results for organic compounds found in the water distribution system (after blending of the well water), 9 were above the MCLs mentioned above. The total number of sampling events was not described.
Table 1: Contaminants of Concern
Off-Site, Tenth Street Site
Maximum Reported Values (2)
| Contaminant | Supply Well | Distribution Water |
| Trichloroethylene (TCE) Tetrachloroethylene (PCE) Trihalomethanes (THMs) |
34 ppb* 25 ppb* 240 ppb |
18 ppb 5 ppb <<100 ppb** |
* - parts per billion. (The MCL for both TCE and PCE is 5 ppb.)
** - no numerical value given, reported as well under 100 parts per billion
Other contaminants, including cis-1,2-dichloroethylene, toluene, and 1,2-dichloroethane, have also been reported in water samples at levels below 5 ppb.
In order to identify other facilities that could contribute to groundwater contamination in the area of concern, ATSDR searched the 1987 and 1988 Toxic Chemical Release Inventory (TRI). TRI is developed by EPA from chemical release (air, water, soil) information provided by certain industries. No sites in the near vicinity of the Tenth Street site reported releases of site related chemicals in Columbus, Nebraska.
C. QUALITY ASSURANCE AND QUALITY CONTROL
The EPA, the Nebraska Department of Health, and the City of Columbus did not provide quality assurance and quality control (QA/QC) information for the data reviewed for this Preliminary Health Assessment. The validity of ATSDR's findings depends upon the reliability and accuracy of the data provided and reviewed in this health assessment.
The Tenth Street Site serves primarily as a municipal parking lot and does not contain any unusual physical hazards.
A. ENVIRONMENTAL PATHWAYS (FATE AND TRANSPORT)
Groundwater
Groundwater is the major environmental pathway of concern at the Tenth Street site. Based upon on-site soil-gas analysis, groundwater underlying the site is probably contaminated with TCE, PCE and THMs. This conclusion is supported by off-site soil-gas results and concurrent observation of the same contaminants in the municipal wells located west and southwest of the subject site.
Groundwater underlying the site tends to flow east-southeast at a downward slop of approximately 10 feet of drop per mile toward the Loup River. The well-field is located generally west of the site; however, it is believed that the pumping of the wells creates a gradient (downward slope in the surface of the groundwater zone) in the direction of the well-field that results in the wells' contamination.
Because of limited data, it is difficult to evaluate trends in groundwater contamination. Well number 4 has been taken out of service because of the apparent continuing raise of TCE levels in that particular well.
Soil and Sediment
Except for EPA's soil gas data, no other data characterizes soil contamination on or off site. It appears that there is a zone of contaminated soil underlying the subject site. Since dumping activities occurred over several years, TCE, PCE, and THMs have leached into subsurface soils and are now reflected in the soil gas measurements. Surface soils probably contain little to no contaminants because the remaining chemicals at the surface easily evaporate to the air.
Surface Water
The site is largely level with no major drainage channels. Surface water from heavy rains would percolate through the site soils. More information is needed to better characterize this potential pathway.
Air
There are little data available that characterizes the air above or near the Tenth Street Site that would address known site contaminants. It is anticipated that in its present undisturbed condition the level or organic air pollution coming from the site would be negligible or unmeasurable. Excavation of the site during future site use or cleanup activities could release measurable amounts of PCE and TCE to the air and should be addressed in the planning stages of any future activities involving the site. Soil-gas is contaminated on or near the site at depths that could seep into nearby basements. This potential pathway needs further evaluation.
Food Chain
City water used to water gardens would normally be exposed to the air through sprinkling where it might be expected that most of the TCE, PCEW or THMs would be released to the atmosphere.
The other potential food chain pathway would be through contaminated groundwater migrating to the Loup River and hence possibly contaminating fish found in the river. Volatile organic compounds do not tend to accumulate in the food chain. This pathway would not be a problem.
The major human exposure pathway from this site is drinking VOC-contaminated city water. Showering or bathing with VOC-contaminated city water would also provide an opportunity for direct contact with the contaminants. Also, VOCs could be released to the air and inhaled during showering or bathing. Finally, contaminated soil gases could seep into basements near the Tenth Street site and be inhaled by site occupants.
The levels of tetrachloroethylene (PCE) in the water at the point of distribution to individual households are low (maximum 5 ppb). The Safe Drinking Water Act (SDWA) established drinking water regulations to protect the public health. These regulations apply to public water systems. These regulations include maximum permissible levels of contaminants (MCLs) in water that is delivered to the user of the public water system. The proposed MCL for PCE is 5 ppb. Tetrachloroethylene has been detected in many drinking water systems in the United States. The EPA Groundwater Survey of 945 water supplies that used groundwater sources found 8% of the supplies had detectable levels of PCE. The median levels at these 75 water supplies were ˜0.75 ppb and the maximum level reached 69 ppb. The long-term health effects to humans from ingesting low levels in water supplies have not been identified. (3,4) The estimated level of exposure through ingestion of water with the maximum levels seen at this site is below that level that has been determined to be the minimal risk level (MRL). MRLs are an estimate of daily human exposure to a chemical that is not likely to produce any harmful (non-carcinogenic) effects over a specified duration of exposure. (5) The levels found in the drinking water should not pose a significant risk to the public health at the present time.
Trichloroethylene (TCE) is widespread in the environment. The most common means of exposure to low levels in the general population is through the concentrations found in breathable air. TCE has also been detected in many water supplies in the United States. The EPA Groundwater supply Survey found TCE in 91 of the waters surveyed. The median level in these 91 waters was ˜1 ppb. One system had a single high maximum value of 130 ppb. The maximum level of trichloroethylene found at the distribution water was 18 ppb. While this value exceeds the MCL of 5 ppb, there is no data on the concentrations at the tap to which people would be exposed. The tap levels should be lower than at the distribution point so people should not be exposed to levels that would harm their health. The central nervous system, liver, and kidney are the primary organs affected by exposure to TCE; however, effects on these organs occur at much higher levels of exposure than would be seen at this site. (4,5)
Chloroform and other trihalomethanes have been found in various concentrations in over 99 percent of the water supplies surveyed in the EPA National Organics Reconnaissance Survey and the EPA National Organic Monitoring Study. The main source of chloroform in these water supplies is the chlorination of the naturally occurring humic materials. Many water supplies (primarily surface water) are chlorinated to prevent the occurrence of waterborne infectious diseases that were a major public health problem early in this century in the United States. The levels of trihalomethanes reported at this site are below the 100 ppb MCL. (4,6,7,8). These chemicals have not been identified to date at concentrations in the drinking water that should cause a significant risk to health in the general public. (9,10,11).
B. Health Outcome Data Evaluation
Census information was obtained and reviewed for the county and the city. The 1986 county population was 29,500. Sixty-three percent or 18,610 persons reside in the city of Columbus. The racial make-up of the population is over 99 percent white. (1) Appendix B contains a tabular summary of the census information.
Children under five years of age comprise 8.4 percent of the overall population. Children may represent a more sensitive population than adults to exposures from these compounds. The levels are not such that they are expected to create a threat to children's health.
Platte County Residents in 1975 (From 1980 Census): (13)
Population over age five: 15,904
Population living in same house in 1980: 8,321 (52.3%)
Population living in same county in 1980: 4,346 (27.3%)
The majority of persons in Platte county have lived in the same house for at least 5 years. This indicates a stable population in the city of Columbus with long-terms use of the municipal water by the individuals.
Summary Tables of vital statistics information are provided in Appendix B. The number of births in Columbus have remained relatively stable over the years of 1986 to 1988. The percent of births in Platte County with birth defects is not significantly higher than the range one would expect when compared to the rates for the state of Nebraska.
The slightly higher rate for infant death in Platte county when compared to the state may reflect the larger percent of very low birth weight infants born during that time period. The toxicological implications of the compounds and the levels seen at this point do not indicate a relationship between the site and the rate of very low weight births.
A review of the 10 leading causes of death indicates an increased rate of death from diseases of the kidney (nephritis/nephrosis) in the city of Columbus when compared to the county and state rates. While the kidney is a target organ for these compounds, this elevated rate cannot be attributed to exposure to the low levels seen in the water supply. This may represent a subpopulation with increased sensitivity to the effects of exposure that must be considered. These health parameters should be investigated further to identify possible risk factors.
This site presents an indeterminate public health hazard. There is evidence that the general population is and has been exposed to TCE, PCE, and THMs in the drinking water at very low concentrations. The concentrations presently are at a level that has not been demonstrated to result in adverse health effects. Because the major route of exposure is the municipal water supply, concern exists over potentially increasing concentrations of the substances that could exceed EPA's MCL. Continued well water monitoring, combined with proper blending of supplied water, should keep the contaminant concentrations below levels of public health concern. In addition to exposures through the drinking water, the potential exists for soil-gas VOC levels to contaminate indoor air of nearby buildings and lead to an inhalation exposure.
Water quality data for the years prior to 1984 were not available; therefore, conclusions regarding the duration of exposure cannot be made at present.
A review of vital statistics data yielded no clearly identifiable health effects relatable to this site. Elevated death rates from kidney diseases, compared to state and county death rates, would not be explained by exposure to the low levels of contamination attributed to this site.
Since a remedial investigation has not yet been completed for this site, there are a number of data gaps that must be filled to allow the conduct of a more thorough public health assessment. Some of the more important data gaps include understanding potential soil-gas migration pathways with respect to nearby building basements, characterization of volatile gas release and migration potential during site remediation activities, and boundaries and migration rates off the contaminated groundwater plume. Other data gaps, such as surface water drainage patterns through the site, surface soil contamination levels, and ultimate fate of contaminants migrating to the Loup River through the groundwater, are anticipated to be minor with respect to potential for adverse impact on human health. This is because the volatile nature of the contaminants in the surface soils would suggest that they are probably no longer present in the upper soil levels and consequently would not contaminate surface water flowing through the site. Also, volatile organic compounds migrating to the Loup River would not concentrate in fish and consequently would not impact the food chain.
The direct relationship of the site to the presence of trihalomethanes in the water supply is not evident at this point.
This site has been reviewed by the ATSDR Health Activities Recommendation Panel. While there is evidence that individuals are exposed to low levels of trichloroethylene and tetrachloroethylene, data at this point are very limited. Further information as provided by the site remedial investigation will assist ATSDR in determining any public health actions for the community in the future. ATSDR will review the remedial investigation information as it becomes available.
Additional public involvement was sought during the period of public comment on the preliminary public health assessment. There were no comments received during the comment period.
ATSDR in cooperation with the Nebraska Department of Health will conduct a closer evaluation of the rate of births of very low weight infants and the deaths from diseases of the kidney is indicated to identify risk factors associated with these parameters.
When indicated by public health needs, and as resources permit the evaluation of additional relevant health outcome data and community health concerns, if available, is recommended.
Harvey Rogers
Environmental Engineer
Remedial Programs Branch
Division of Health Assessment and Consultation
Virginia Lee
Medical Officer
Federal Programs Branch
Division of Health Assessment and Consultation
David Parker
ATSDR Regional Representative
Region VII
Age Make-up for Columbus in 1980 (12)
|
Total
|
Male
|
Female
|
|
| Total Population |
17,328
|
8,173
|
9,155
|
| Under 5 years |
1,451
|
702
|
749
|
| 5 to 9 years |
1,352
|
690
|
662
|
| 10 to 14 years |
1,301
|
664
|
637
|
| 15 to 19 years |
1,583
|
776
|
807
|
| 20 to 24 years |
1,527
|
730
|
797
|
| 25 to 34 years |
2,749
|
1,355
|
1,394
|
| 35 to 44 years |
1,759
|
848
|
911
|
| 45 to 54 years |
1,637
|
797
|
840
|
| 55 to 64 years |
1,576
|
719
|
857
|
| Over 65 years |
2,393
|
892
|
1,501
|
1988 Vital Statistics for the Area (14)
Number of Births by Usual Residence of the Mother
| Year |
Nebraska
|
Platte County
|
Columbus City
|
| 1986 |
24,425
|
482
|
301
|
| 1987 |
23,813
|
473
|
296
|
| 1988 |
23,904
|
522
|
328
|
| Rate per 1000 Pop. |
14.9
|
17.2
|
17.3
|
Birth Defects by County of Residence
| Year |
Nebraska
|
Platte County
|
| Percent of 1988 Births |
2.3
|
3.3
|
| Percent of 84-85 Births |
2.5
|
2.4
|
Very Low and Low Birth Weight by Place of Residence
| Year |
Nebraska
|
Platte County
|
| 1988 Less than 1500 grams Rate per 1000 Live Births |
9.5
|
11.5
|
| 1988 Less than 2500 grams Rate per 1000 Live Births |
55.3
|
57.5
|
| 1984-1988 Less than 1500 grams Rate per 1000 Live Births |
8.9
|
7.1
|
| 1984-1988 Less than 2500 grams Rate per 1000 Live Births |
54.4
|
39.7
|
Number of Deaths by Usual Residence of the Deceased
| Year |
Nebraska
|
Platte County
|
Columbus City
|
| 1988 Crude Death Rate |
9.3
|
7.7
|
8.3
|
| 1988 Infant Death Rate per 1000 Live Births |
9.0
|
11.5
|
6.1
|
| 84-88 Infant Death Rate per 1000 Live Births |
9.4
|
9.8
|
11.2
|
| 1988 Neonatal Death Rate per LB |
5.4
|
7.7
|
6.1
|
| 84-88 Neonatal Death Rate per 1000 LB |
5.9
|
6.3
|
7.5
|
LB = Live Births
Ten Leading Causes of Death in 1988
| Cause |
Nebraska Rate*
|
Platte Rate*
|
Columbus Rate*
|
| Heart Disease |
206.2
|
215.0
|
195.7
|
| Cancer |
155.4
|
145.8
|
159.6
|
| Cerebrovascular |
42.0
|
35.7
|
40.9
|
| Pneumonia |
23.6
|
9.3
|
5.2
|
| Accidents |
32.3
|
35.5
|
20.2
|
| Chronic Lung |
16.8
|
13.2
|
8.1
|
| Atherosclerosis |
8.1
|
6.8
|
8.9
|
| Diabetes Mellitis |
10.7
|
5.6
|
3.3
|
| Suicide |
9.0
|
15.9
|
12.1
|
| Nephritis/Nephrosis |
6.2
|
7.8
|
12.7
|
* Age-Adjusted Rate per 100,000 Population
