PUBLIC HEALTH ASSESSMENT
RAILROAD AVENUE GROUNDWATER CONTAMINATION
WEST DES MOINES, POLK COUNTY, IOWA
The Railroad Avenue groundwater contamination site (the site) is in West Des Moines, PolkCounty, Iowa. Located on approximately 120 acres, the site comprises mixed residential,industrial and commercial properties. Underneath the site, chlorinated volatile organiccompounds (VOCs) have contaminated the shallow (i.e., 30-50 feet deep) groundwater. Thesecompounds have compromised several shallow wells within the West Des Moines water workssystem. A contamination source, however, has not yet been identified.
In 1993, routine water analysis by the city of West Des Moines identified 1, 2 cis-dichloroethylene (1, 2 cis-DCE) at a concentration of 1.2 µg/L (micrograms per liter of water) in the water supply. Subsequently, several shallow municipal wells were found to be contaminated by VOCs, including 1, 2 cis-DCE, trichloroethylene (TCE), tetrachloroethylene (PCE) and benzene. Five of these wells have been taken out of service. Because of the impact on the West Des Moines water supply, the U.S. Environmental Protection Agency (USEPA) has assigned the site to the National Priorities List.
Surface water and sediment at the site have not been impacted by the VOCs. Testing for VOCs in surface soils has not revealed any significant VOC contamination. Subsurface soilsgenerally 8 feet or greater in depthare contaminated with VOCs, but at levels which should not present a health hazard.
The past, present, and future health hazard category chosen for this site is no apparent publichealth hazard. This category is used when exposure to toxins might be occurring or might haveoccurred in the past, but at levels below any known health hazard. Analysis of availableenvironmental data has not revealed that residential or commercial water customers are or have been exposed to VOCs at concentrations that might cause any adverse health effects.
The Railroad Avenue site comprises residential, commercial and light industrial properties.Much of the land contained within the site was once used for railroad car repair and servicing.The site is about 120 acres in size and is approximately bounded on the south by the lakes at theRaccoon River Park, on the west by 19th Street, on the north by Holiday Park, and on the east by5th Street in West Des Moines. Site access is not restricted. Residences are located primarily onthe northern and western boundaries of the site (1, 2).
In 1993, a routine water distribution sample collected by the West Des Moines water works was found to contain the volatile organic compound (VOC) 1, 2 cis-dichloroethylene (1, 2 cis-DCE) at a concentration of 1.2 µg/L (micrograms per liter of water). Prior to 1993, no evidence of VOC contamination had been found in West Des Moines water. VOC contamination in the municipal water supply was traced back to two shallow wells installed in 1991, within the confines of the Railroad Avenue site. After the discovery of the VOCs, these wells were immediately taken out of service. Nevertheless, under the combined effects of natural groundwater flow and pumping from uncontaminated wells, underground contaminants have moved toward the south and east. From 1994-1999, several other municipal wells within the site were found to contain DCE and other VOCs, including benzene, trichloroethylene (TCE) and tetrachloroethylene (PCE). Three more wells were taken out of service as soon as the contamination was discovered. In 1997 USEPA contractors conducted a Preliminary Assessment/Site Investigation (PASI) and in 1999 conducted an Expanded Site Investigation (ESI). But they could not identify a source of the VOCs (1, 2), despite the fact that the investigations involved extensive soil, water and sediment sampling and analysis. Based on these prior investigations and the impact of VOCs on the West Des Moines municipal wells, the USEPA has assigned the site to the National Priorities List (NPL).
About 3,700 persons live within 1 mile of the Railroad Avenue site. Still, the population at risk could potentially include all residential and commercial water users within the city limits of WestDes Moines--the West Des Moines water system supplies water to a population of 46,980 (3).This population is served by 22 wells: 19 shallow municipal wells drilled approximately 30 to 50feet deep in the alluvial aquifer, and three deep wells approximately 2,500 feet into the Jordanaquifer. Four of these shallow wells and one deep well are within the boundaries of the RailroadAvenue site. All other wells are from ½-2 miles to the south and southwest and slightlydowngradient of the site. Additional water is purchased from the Des Moines water works,supplied by surface water intakes on the Raccoon and Des Moines Rivers. The amount purchaseddepends on the time of year, with more being purchased during the summer months.
West Des Monies relies on a blended system of water distribution whereby water from severalmunicipal wells is combined into a finished product. The blended nature of the water supplyensures that no one well will supply a significant fraction of the total water used by thecommunity. About half of West Des Moines water comes from the three deep wells, which havenot been contaminated by VOCs. Water supplied to West Des Moines residential andcommercial customers is tested quarterly, and has not shown evidence of VOC contaminationapproaching levels of health concern (1, 2, 4) (see Tables 1 and 2).
There are no known private wells in use within the Railroad Avenue site, or within the West DesMoines water works service area.
Contaminants of Concern
VOCs are the contaminants of concern at this site because they are present in the largest quantities and have directly impacted the West Des Moines water supply system. VOC contamination has caused several municipal wells to become unusablethis is why the site has been assigned to the NPL .
Surface Water and Sediment
Surface water and sediments associated with the Railroad Avenue site have not shown VOCcontamination above any health-based screening or reference levels (1, 2). The Racoon and DesMoines rivers, both of which supply a part of West Des Moines' water needs, have high-volumeflows and act as sinks to dilute any contaminants that might reach them.
Subsurface and Surface Soils
Shallow soils (0-2 feet) within the Railroad Avenue site do not contain levels of VOCs above any health screening or reference values. No true surface soil samples (0-2 inches) are available for review, however, because of the volatile nature of the chemicals of concern at this site, it is very unlikely that significant levels would be found in the top inches of soil. Subsurface soils (8-10 feet deep) on industrial properties within the site are contaminated with 1, 2 cis-DCE at up to 3,800 µg/kg (micrograms per kilogram of soil), TCE at 26.7 µg/kg, and benzene at 58 µg/kg (1, 2). The concentrations of VOCs found in subsurface soil are less than the ATSDR environmental media evaluation guides (EMEG) or cancer risk evaluation guides (CREG) for DCE, TCE and benzene in soil. The EMEG and CREG are screening or comparison values, used to assess the relative health hazard posed by contaminants at a particular site. No level of VOCs exceeding any reference or screening values has been found in residential soils at the Railroad Avenue site.
Table 1 lists the concentrations of 1, 2 cis-DCE and benzene in West Des Moines (WSDM) wells #12 and #13 for the period 1991-1999. Wells #12 and #13 are where VOC contamination was discovered originally in 1993. The maximum contaminant levels (MCLs) for drinking water sources are health-based standards established by the USEPA and are considered to be protective of public health for a lifetime of exposure. The MCL for 1, 2 cis-DCE is 70 µg/L, and for benzene the MCL is 5 µg/L. In 1994, well #12 contained benzene at a concentration of 11 µg/L, which exceeded the MCL. In 1996, well #13 exceeded the benzene MCL and the MCL for 1, 2 cis-DCE. To date, no other VOCs have been found in wells #12 and #13. Generally, DCE and benzene concentrations in these two wells have been decreasing since 1994 (1, 2).
|Sampling Date||Location-well number||1,2 cis-DCE |
ND = compound not detected above method detection limits.
In 1997, 1, 2 cis-DCE was found in West Des Moines wells #6 and #7 at 4 µg/L and 38 µg/L, respectively. The 1999 ESI report found low concentrations of 1, 2 cis-DCE in municipal wells #5 and #21. These wells contained 1, 2 cis-DCE at 2.3 µg/L and 0.22 µg/L (see Table 2). Benzene has not been found in any of the wells listed in Table 2.
|Sampling Date||Location-well number|| 1,2-cis DCE |
| Benzene |
| TCE |
ND = compound not detected above method detection limits.
The MCL for both TCE and PCE is 5 µg/L. In only one instance from 1997 to 1999 was the MCL exceeded, and that was well #21 at 6.8 µg/L TCE in September 1999. Wells #6, #7, #12, #13, and #21 have been taken out of service because of the presence of VOCs. Wells #5 and #19 remain in service, but like all other wells, they are monitored regularly for evidence of further contamination. The post-treatment distribution water sample collected in 1999 contained TCE and 1, 2 cis-DCE, but at levels considerably below the MCLs. According to the West Des Moines water works, no VOCs were detected in the post-treatment supply during the year 2000 (4).
Community Health Concerns
There are no known community health concerns regarding the West Des Moines RailroadAvenue site. In the summer of 2000, West Des Moines water works mailed to its customers aninformational flyer about the site. The flyer described the water contamination problem andassured the public that any wells posing a health risk would be taken out of service as quickly aspossible. A public availability session regarding the site was held on October 24, 2000. Those inattendance included representatives from USEPA, IDPH, Iowa Department of Natural Resources(IDNR) and West Des Moines municipal government. No private citizens attended thisavailability session. In October 2001, the USEPA distributed a fact sheet requesting publiccomment about the site (5). IDPH staff made site visits in the winter of 2001 and spring of 2002.No unusual site conditions were observed during either of these visits.
Quality Assurance and Quality Control
In preparing this health assessment, IDPH relied on the information provided in the referenceddocuments. IDPH assumes that adequate quality assurance and quality control measures werefollowed regarding chain of custody, laboratory procedures and data reporting. Furthermore,during the preparation of this public health assessment, IDPH concluded the data were adequate and reliable.
A public health assessment determines whether people have been exposed, or could possiblybecome exposed to site contaminants. Identification of exposure pathways, either completed orpotential, is a necessary part of the public health assessment process. A completed exposurepathway consists of the following five elements: 1) a source of contamination, 2) transportationof the contaminants through an environmental medium (air, water or soil), 3) a point of exposure,4) a route of human exposure, and 5) an exposed population. For an exposure pathway to becomplete, all these elements must be present. Completed exposure pathways indicate thatexposure has occurred in the past, might be occurring now, or could possibly occur in the future.
In a potential exposure pathway, at least one of the five elements is missing. Also, an exposurepathway can be eliminated from further analysis if one or more elements do not exist, or mightnever exist.
Completed Exposure Pathways
No completed exposure pathways, to significant levels of contaminants, have been identified atthe site. Based on available site data, any past exposures to Railroad Avenue site contaminantswould have been at levels well below those known or suspected of causing human healthproblems. VOCs were first discovered in the water supply in 1993; there is no existing evidenceof VOC contamination or exposure prior to that time.
Currently, people living in and around the site are not exposed to on-site contaminants. West DesMoines water customers are not being exposed as no VOC contamination now exists in thetreated water supply. Future exposures are unlikely to occur because any contaminated wellshave been removed from service, and the West Des Moines water supply is monitored regularlyfor the presence of VOCs and other contaminants. Discontinuing use of contaminated wells and aprogram of regular well monitoring will help to ensure that public health is protected, and thatVOCs do not enter the treated water delivered to West Des Moines residents.
Potential Exposure Pathways Analysis
Ingestion of contaminated water and soil, and inhalation of vapors from that water or soil,constitute potential exposure pathways. The following is an analysis of the likelihood of humanexposure through potential ingestion or inhalation pathways.
|Groundwater:||Volatile organic compounds have contaminated the groundwater at the Railroad Avenue site. Concentrations of these compounds are generally well below any health-based water quality standards, and supply wells are monitored quarterly. For these reasons, current and future exposures to VOCs at levels of concern are not likely. Additionally, past exposures to VOCs were probably not at levels of concern because the limited duration of those exposures and the blending of water from multiple sources.|
|Soil:||Because of the depth of contamination, soil is not a viable exposure pathway. The largest contamination concentrations are on industrial properties within the site, at depths of 8 feet or more. These soils contain VOCs, but at concentrations below health-based screening values. The soils and dust have not been, and are not expected to be, sources of environmental exposure for those who live and work in and around the site. For these reasons, it is also unlikely that soils will present a health hazard in future.|
|Surface water:||Surface water has not been impacted by the Railroad Avenue contamination. The Racoon and Des Moines rivers have high volume flows, thus they act as sinks to dilute any contaminants that might reach them. Also, analysis of surface waters has not revealed the presence of VOCs at levels approaching any health concerns.|
|Air:||Because contaminants are not found at the surface but underground, air is not a likely pathway of exposure. Dusts and vapors arising from soils are not likely to pose a health hazard. Migration of vapors from groundwater into homes and businesses is also unlikely because of the relatively low concentrations of VOCs present and the depth to the contaminated water (30-50 feet). Likewise, inhalation of VOCs while showering or bathing should not be a viable exposure pathway, as no significant VOC contamination has been found in the treated water supply.|
Ingesting water containing VOCs such DCE, TCE, PCE and benzene for long periods could lead to adverse health effects, although the extent of some of these effects is not yet clear (6-9). Health studies of populations exposed to low levels of VOCs in drinking water have shown conflicting results as to any long-term adverse health effects. One study suggested an association between long-term exposure to VOC-contaminated well water (containing up to100 µg/L VOCs) and increased urinary tract infections in childrenalthough these children were also exposed to a number of other chemicals. In another study involving well water contamination, three communities in Michigan exposed to TCE and PCE in drinking water at levels above MCLs experienced no increase in kidney disease (6, 7).
The link between ingestion of VOC-contaminated water and cancer is controversial. A study of 1.5 million residents in 75 New Jersey towns found elevated rates of total leukemias, childhood leukemias, acute lymphatic leukemia, and non-Hodgkin's lymphoma in females after long-term exposure to greater than 5 µg/L TCE (6). By contrast, a study of total cancer incidence, liver cancer, non-Hodgkin's lymphoma, Hodgkin's disease, and leukemia in two Finnish villages with drinking water containing 200 µg/L TCE and 180 µg/L PCE found no significantly increased rates of these diseases (6, 7). A study in New Jersey found PCE in drinking water was associated with an increased incidence of non-Hodgkin's lymphoma in females. That said, however, the investigators noted that the conclusions of their study were limited by lack of information on individual long-term residence and water consumption (7).
Benzene is a known human carcinogen, but much of the evidence for this conclusion is from inhalation exposure studiesnot studies of drinking contaminated water (9). No studies have reported a link between an increased risk of cancer andprimarilyingestion, or oral exposure to benzene. Any other long-term (chronic) health effects from ingesting water containing benzene are not well established. The ATSDR Toxicological Profile for Benzene could not find any human health studies relating respiratory, cardiovascular, liver, or kidney effects and oral exposure to benzene. Likewise, no studies could be found on any reproductive or developmental health hazards following ingestion of benzene-contaminated water (9).
It is unlikely that any chronic health symptoms, including an increased risk of cancer, wouldoccur following exposure to the very low concentrations of VOCs found at the Railroad Avenuesite. This conclusion applies equally to sensitive populations such as children and the elderly.
Exposure to toxic substances poses a greater risk to children than to adults. Children breathemore air and consume more food and water per unit of body weight than do adults. They are alsoless likely to recognize and avoid hazardous situations and conditions.
The health effects of possible toxic exposure to children living within or visiting the RailroadAvenue site have been considered in relation to the degree of health threat the site poses. Becauseno VOC contamination now exists in the West Des Moines water distribution system, it isunlikely that children would experience any adverse health effects from ingesting West DesMoines water. As has been stated, due to their depth, contaminated soils at the site are not readilyaccessible. And surface waters and sediment are not contaminated at levels which would be a health concern, even to children.
Several West Des Moines water wells have been taken out of service because of contamination,and testing of the treated (finished) water supply has shown only trace amounts of VOCs, belowany level of health concern. Based on the available information, no adverse health effects areexpected in residents or commercial water customers who consume water from the city of WestDes Moines. As a result, IDPH and ATSDR have determined that the Railroad Avenue sitecurrently presents no apparent public health hazard.
The health hazard category for any past exposures at the site is no apparent public healthhazard. Exposure to VOCs in the West Des Moines water supply might have occurred beforeany contaminated wells were taken out of service, but at levels far below any that have been shown–or suggested to have caused–adverse health impacts.
IDPH recommends continued quarterly monitoring of municipal wells and the water distribution system in West Des Moines.
- In October 2000, IDPH staff attended a public availability meeting for the RailroadAvenue site.
- IDPH staff have completed a public health needs assessment for this site.
- This Public Health Assessment went out for public comment for 30 days starting on July22, 2004. A draft copy of this assessment was made available for public comment at theWest Des Moines Public Library. No comments from the public were received during the30-day comment period.
- IDPH will update the public health assessment if new data become available.
- IDPH will work with EPA, IDNR and the West Des Moines water works to develophealth education and community involvement materials to inform residents regarding thewater quality.
- Ecology and Environment, Inc. Final preliminary assessment/site assessment report forWest Des Moines WS Well #13 Site, West Des Moines, Iowa. Prepared for USEnvironmental Protection Agency Region 7, Superfund Division. Overland Park, KS;August 27, 1999.
- Ecology and Environment, Inc. Expanded site inspection report for the Railroad AvenueGroundwater Contamination Site, West Des Moines, Iowa. Prepared for USEnvironmental Protection Agency Region 7, Superfund Division. Overland Park, KS;August 21, 2000.
- State Library of Iowa Information Center. Des Moines Iowa; May 2002.
- West Des Moines Water Works. 2001 water quality report. West Des Moines, Iowa;January 2002.
- US Environmental Protection Agency Region 7. Office of External Programs. Fact sheetfor Railroad Avenue Groundwater Contamination Site, West Des Moines, Iowa. KansasCity, Missouri; October 2001.
- Agency for Toxic Substances and Disease Registry. Toxicological profile fortrichloroethylene. Atlanta: US Department of Health and Human Services; September1997.
- Agency for Toxic Substances and Disease Registry. Toxicological profile fortetrachloroethylene. Atlanta: US Department of Health and Human Services;D. September 1997.
- Agency for Toxic Substances and Disease Registry. Toxicological profile for 1, 2-dichloroethene. Atlanta: US Department of Health and Human Services;. August 1996.
- Agency for Toxic Substances and Disease Registry. Toxicological profile for benzene.Atlanta: US Department of Health and Human Services; September 1997.
Stuart Schmitz, P.E., and Charles Barton, Ph.D., DABT
Hazardous Waste Site Health Assessment Program
Division of Health Protection and Environmental Health
Iowa Department of Public Health
The public health assessment for the Railroad Avenue site was prepared by the Iowa Departmentof Public Health, Hazardous Waste Site Health Assessment Program, under a cooperativeagreement with the Agency for Toxic Substances and Disease Registry (ATSDR). It is inaccordance with approved methodology and procedures existing at the time the health assessment began.
Technical Project Officer, Cooperative Agreement Team, SSAB, DHAC, ATSDR
The Division of Health Assessment and Consultation, ATSDR, has reviewed this healthassessment, and concurs with its findings.
Lead, CAT, SSAB, DHAC, ATSDR