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PUBLIC HEALTH ASSESSMENT

POOLS PRAIRIE SITE
(a/k/a Neosho Wells)
NEOSHO, NEWTON COUNTY, MISSOURI


SUMMARY

The Pools Prairie site (formerly the Neosho Wells site) consists of six areas of volatile organiccompound (VOC)-contamination south and east of the city of Neosho, Newton County, Missouri. Of the affected areas, Areas 1 and 2 are residential. In 1994 and 1995, VOCs were detected inprivate wells in Area 1 and in Area 2, respectively. Only trichloroethylene (TCE) and carbontetrachloride were found above their respective Maximum Contaminant Levels (MCL) establishedby the Environmental Protection Agency (EPA). Wells in the two areas are used by residents astheir potable water source. Investigations into the possible source(s) of the groundwatercontamination found four potential source areas (SA-1 thru 4) located on the former Fort CrowderMilitary Reservation. The four source areas were part of a rocket engine manufacturing and testingoperation that used TCE. Two of the areas were used to test engines and components and operatedfrom approximately 1956 to approximately 1967 and 1973, respectively. The manufacturingbuilding, built in approximately 1956, is still in operation. Operations at this building used TCEuntil approximately 1992. The 900 Building was used from approximately 1968 to 1992 foroperations including the cleaning of engine fuel control components.

Residents with contaminated wells have been exposed to VOCs in the past through ingestion,inhalation, and dermal contact. To reduce residential exposure to the contaminated groundwater,bottled water was provided to more than 30 residences in 1995. In 1998, whole-house filteringsystems were installed in the houses as an interim measure to eliminate exposure until a public watersystem could be installed. A public water system is in the process of being installed and, as long asall residences connect to the public water system, long-term exposure should be eliminated for thosewith contaminated and potentially contaminated private wells.

Because contaminant levels are unknown for past exposures (possibly from 1956 until the fall of1995), and consequently the amount of exposure residents received from their potentially VOC-contaminated private wells for this time period is unknown, the Pools Prairie site is classified as anIndeterminate Public Health Hazard for past exposures. Because the exposure pathways wereeliminated by the whole-house filtering system and, ultimately, by connection to the public watersystem, the Pools Prairie site is currently classified as a No Apparent Public Health Hazard forresidents connecting to the public water supply. For those not connected/connecting to thepublic water supply, the Pools Prairie site is currently classified as a Public Health Hazard. ThePools Prairie site is classified as A Public Health Hazard for the future because: contaminatedgroundwater remains at the Pools Prairie site; some residents may not connect to the public watersystem and/or not properly maintain their whole-house filtration system; new wells may be drilled inthe contaminated aquifer; the contamination plume may move or increase in concentration; and thesource areas have yet to be remediated.


PURPOSE AND HEALTH ISSUES

In cooperation with the Agency for Toxic Substances and Disease Registry (ATSDR), the MissouriDepartment of Health (DOH) is evaluating the public health impact of the Pools Prairie site. ThePools Prairie site was proposed by the Environmental Protection Agency (EPA) for its NationalPriorities List (NPL) on January 19, 1999, and finalized on September 17, 1999. This public healthassessment determines whether health effects are possible from exposure to contamination at this siteand recommends actions to reduce or prevent possible health effects. ATSDR is a federal agencywithin the U. S. Department of Health and Human Services and is authorized by the ComprehensiveEnvironmental Response, Compensation, and Liability Act of 1980 (CERCLA) to conduct publichealth assessments at hazardous waste sites. This document will address past, current, and futureexposure to the groundwater contaminated by the site.


BACKGROUND

The Pools Prairie site (formerly the Neosho Wells site) is located south and east of the city ofNeosho in Newton County, Missouri. The site consists of six specific areas of volatile organiccompound (VOC)-contamination. Four of the areas are potential source areas (SA-1 thru 4) whereVOCs have contaminated the soil and groundwater. These source areas are located on the formerFort Crowder Military Reservation (Camp Crowder). The two other areas (Area 1 and 2) areresidential areas where private wells are used for drinking water and the groundwater iscontaminated with VOCs. These residential areas lie outside the Neosho city limits, but are adjacentto the former Fort Crowder area. One area of contaminated groundwater is located south of Neoshoin the vicinity of the Highway 71 and Quince Road intersection (Area 1). The second area ofcontaminated groundwater (Area 2) is located east of Neosho along roads HH and TT and near theintersection of Highways 71 and 60 (See Figure 1 in Appendix A).

The Pools Prairie site was discovered in July 1994, when a resident complained to the NewtonCounty Health Department (NCHD) about a leaking gas tank at a nearby truck stop. The residentwas concerned that leaking gas might be affecting their well. Subsequent sampling of the well byNCHD indicated no gasoline contamination, but various VOCs were found includingtrichloroethylene (TCE) at 110 parts per billion (ppb) and carbon tetrachloride at 5.2 ppb. Thelevels of TCE and carbon tetrachloride exceeded the Environmental Protection Agency (EPA)Maximum Contaminant Levels (MCL) of 5 ppb for public drinking water systems. An MCL is themaximum permissible level of a contaminant in water which is delivered to any user of a publicwater system.

NCHD received additional requests from other nearby residents to have their wells sampled. Through subsequent sampling by NCHD, EPA, and the Missouri Department of Natural Resources(MDNR) during the fall of 1994 and the spring of 1995, all residential wells within a one-mileradius of the Quince Road and Highway 71 junction (Area 1) were sampled. Of the 45 privatewells sampled, VOCs were detected in 12. TCE levels ranged from non-detectable to a maximum of150 ppb, and carbon tetrachloride ranged from non-detectable to 5.2 ppb. Five of the wells hadTCE contamination above its MCL. One well also had carbon tetrachloride contamination above itsMCL. Chloroform, chloromethane, 1,1-dichloroethane, and cis-1,2-dichloroethene (DCE) were alsodetected in various wells, but were below levels of health concern (1,2).

In December 1994, MDNR requested that DOH evaluate the potential for human exposure tohazardous substances at the Pools Prairie site. On December 12-13, 1994, DOH personnel, alongwith personnel from MDNR's Division of Geology and Land Survey and the NCHD, conducted asite visit. The purpose of the site visit was to become familiar with the site, determine whichresidents were being affected, the extent of exposure to the residents, and to determine the possiblesource of the contamination.

In February 1995, DOH completed a Health Consultation on the Neosho Well site (later referred toas the Pools Prairie site) under a cooperative agreement with ATSDR (2). The health consultationrecommended that:

  • an alternate source of water or a whole-house treatment system be provided to the residentswith contaminated wells to prevent continued exposure;

  • further investigation be conducted to determine if other residents were exposed;

  • the known contaminated wells be monitored for changes in the contamination level; and,

  • the source of contamination be determined to prevent other residents from being affected.

In July 1995, the U. S. Army Corps of Engineers began providing bottled drinking water to thoseresidences with wells containing TCE equal to or above its MCL. TCE was used as the indicatorchemical because it was the major contaminant found in the private wells where MCLs wereexceeded.The bottled water was intended to be a short-term response action to reduce residents'exposure from the ingestion of contaminated water until a long-term uncontaminated water supplycould be provided (3).

DOH personnel attended an MDNR public availability session on August 22, 1995, to present thehealth consultation to the public, gather community concerns, respond to health questions from thecommunity and provide community health education. The other agencies involved in theinvestigation were present to share information with the public, answer their questions, exchangeinformation about the site, and determine if there were additional residences that needed bottledwater.

From October 1995 to May 1996, EPA and MDNR expanded water sampling in Area 1 and beganextensive private water well sampling (approximately 145-150 wells) in the Highway HH and TTarea. This additional sampling was conducted to further determine the extent of contamination andto determine if residents were being exposed. This expanded sampling resulted in the discovery ofthe second area (Area 2) of TCE groundwater contamination in the Highway HH and TT area,located east of Neosho (See Figure 1). Information about the source areas that potentiallycontributed to this contamination will be discussed later under the Source Areas section. By May1996, approximately 220 private and public drinking water wells from both areas had been sampledby the different agencies. Additional sampling of another approximately 30 wells by EPA since thefall 1996 has increased that number to approximately 250 wells (3).

In Area 1, the level of TCE contamination detected in private wells ranged from non-detectable to amaximum 150 ppb and carbon tetrachloride ranged from non-detectable to a maximum of 5.2 ppb. Samples taken after bottled water was provided by the Corps of Engineers in February 1997, foundthat the level of TCE in the original well had risen from 150 ppb to 180 ppb (4). The maximumlevel detected was in a sample collected by MDNR in 1996 that contained 310 ppb TCE and 8.4ppb carbon tetrachloride (5). However, split sample results were not consistent, suggesting apossible problem with the quality control of this sample. In Area 2, TCE concentrations rangedfrom non-detectable to a maximum of 83 ppb (3). Considering the karst geology of the area, it maybe impossible to determine if these groundwater contamination levels is the maximum that has beenor will be present. Refer to the Geology Section for a better explanation about the karst geology. See Table 1 for a summary of contaminants and their levels detected in private wells.

According to an October 1997 Engineering Evaluation/Cost Analysis for the Pools Prairie site, there are 36 private wells (9 in Area 1 and 27 in Area 2) that exceed the MCL for TCE. Other wells have detectable TCE and other VOC contamination, but the levels are below levels of health concern (3).

Table 1.

Summary of Maximum Levels of Chemicals Detected in Private Wells at the Pools Prairie Site in parts per billion (ppb)
Chemicals (MCLs = 5 ppb) TCE Carbon Tetrachloride
Area    
Area 1 (Hwy 71 and Quince Road area) ND to 110 (1994)
ND to 150 (1994-95)
ND to 310 (1996)*
ND to 180 (1997)
ND to 5.2 (1994)
ND to 5.0 (1994-95)
ND to 8.4 (1996)*
NR (1997)
Area 2 (Hwy HH and TT area) ND to 83 ND to 4.0
ND = Not Detected
NR = Not Reported
* = Split sample results were not consistent, suggesting a possible problem with quality control of the sample.
MCL = EPA's Maximum Contaminant Level

On May 21, 1997, DOH/ATSDR completed an EPA-requested health consultation to indicate whatlevel of TCE contamination in residential wells should trigger the installation of a whole-housewater supply to protect the health of residents at the Pools Prairie site. The health consultationreconfirmed the February 1995 health consultation statement that residents whose private wells hadcontamination that exceeded EPA's MCL should be provided with an alternative whole-housesource of water to completely eliminate exposure (6).

On July 31, 1997, DOH/ATSDR released an MDNR-requested health consultation on what wouldbe considered the most protective method of supplying a safe, whole-house water supply to residentsto completely eliminate exposure. DOH recommended that a public water system would be themost effective method to prevent exposure to residents with contaminated wells and those that couldpotentially be affected equally (7).

On February 25, 1998, EPA and MDNR reached an agreement with the potentially responsibleparties (PRPs) to provide whole-house treatment units for residences whose private wells had TCEcontamination equal to or above the MCL. The treatment units were to replace the bottled waterand provide an interim solution until a decision could be made on a long-term water supply (8). Thirty-four in-house filtration systems had been installed by April 14, 1998 (9).

In December 1998, the EPA and MDNR completed an agreement with the PRPs that provides for a long-term water supply to areas affected or potentially affected by the Pools Prairie site (See New Service Areas on Figure 1). Work on the public water system is underway and is projected to be completed in the year 2000. Residences that were in existence prior to the effective date of the Administrative Order of Consent (December 1998) will be given the opportunity to connect to the public water system at no cost to home owners (10).

Although these residents will be given the opportunity to connect to the public water system for no cost, some have already declined connection to the system and will continue to use their contaminated or potentially contaminated private wells. The Administrative Order of Consent does not require the abandonment of existing wells (11).

Source Areas

Through investigations to find the cause of the TCE groundwater contamination in Area 1 and Area2, four potential source areas were identified. The potential source identified for Area 1 was the 900Building on the former Fort Crowder Army Base. The expanded private well sampling foundcontamination in wells of the HH and TT area that potentially could be from three different sources. All four of the potential sources are located on the former Fort Crowder Army Base (See Figure 1).

Fort Crowder was built in 1941 as a training center for the U. S. Army Signal Corps, and at its peak had nearly 47,000 troops stationed there. Fort Crowder was completely deactivated in 1958, and was declared surplus property in 1962 (1). In approximately 1957, the Army transferred a portion of Camp Crowder to the Air Force for construction of a rocket engine manufacturing plant. This installation was known as Air Force Plant No. 65. Construction of Plant 65 began in approximately 1956, with operation beginning in 1956 or 1957. Besides the main manufacturing plant, construction also included an area initially used to test-fire rocket engines (now referred to as the Engine Testing Area or ETA), an area for testing components related to rocket engines (now referred to as the component testing area or CTA), and a former Camp Crowder building, initially used as a warehouse, but later used for engine overhaul and manufacturing purposes (now referred as the 900 Building) (12). In the EPA's January 19, 1999, proposal to add the Pools Prairie site to the NPL, they list the Pools Prairie site as having five potential sources for groundwater contamination. The CTA site and the CTA's contaminated soil are listed separately (two separate sources) (13). For the purpose of this public health assessment, we will consider the CTA as a single source area.

900 Building/Source Area 1 (SA-1)

Based on reports from citizens, it was determined that the 900 building was a potential source ofTCE contamination for the Quince Road and Highway 71 site. Refer to Figure 1 for the location ofthe 900 Building (SA-1). The 900 Building was used for a laundry facility for Camp Crowder untilthe Korean War. It was then used, from 1956 to 1968, to dismantle and store engines in associationwith their testing and production at the manufacturing plant and Test Site. From 1968 to 1992, thebuilding was used for operations including the cleaning of engine fuel control components. According to a 1997 removal assessment report to the EPA, a number of citizens have reported thatTCE was used in the 900 Building during that time (1968-1992) and waste TCE was deposited onthe ground for weed control. The 900 Building is presently used for storage (14).

Sampling at the 900 Building in 1997 found TCE at a maximum concentration in the subsurface soil at 537,000 ppb (reported value was not validated by approved quality control (QC) procedures). Elevated levels were not detected in the surface soils. Groundwater samples found TCE at a maximum of 4,200 ppb in a monitoring well at the 900 Building (15). On May 5, 1999, an agreement was reached to address soil and groundwater contamination around the 900 Building and the Quince Road area. The agreement requires following: an engineering evaluation/cost analysis (EE/CA) be done to evaluate various cleanup alternatives;a risk assessment be completed to identify the risk that the chemicals pose to humans and the environment; and, to determine if further investigations are needed. This information will be used to make decisions about cleanup actions necessary in the Quince Road area (15).

Engine Test Area (ETA) and Component Test Area (CTA)

The test area (ETA and CTA) was first investigated in a preliminary assessment/site investigation (PA/SI) in July 1986. The 1986 investigation determined that waste management practices had caused low-level contamination at the site, but based on off-site sampling, there appeared to be no contaminant migration from the facility (16). In December 1993, a more in-depth investigation of the test area found contamination in the soil and groundwater at the ETA and CTA. The report recommended that additional investigation of the groundwater flow system be conducted (17). More recent dye trace studies (initiated 1996) from both the ETA and CTA have shown a hydrogeologic connection between them and the area of contaminated wells along Hickory Creek (Area 2) (2).

Engine Test Area (ETA)/Source Area 2 (SA-2)

The ETA (SA-2 on Figure 1) was used by a U.S. Air Force contractor to test rocket engines fromapproximately 1956 to approximately 1967. Newly assembled rocket engines were tested in an areathat consists of two bunkers equipped with rocket blast deflectors and concrete waste liquid drainageditches (troughs) leading to a series of storage ponds. During the main period of operation, severaltrain tanker cars of liquid rocket fuel were delivered and used per week. Operations created largequantities of waste fuels and lubricants; however, no record exists of the exact amount. Aftercompletion of the performance tests, the rockets were drained of any remaining fuel. The fuel, anylubricants that were used, TCE, methyl alcohol, hydrazine, and other waste products, were allowedto flow via concrete drainage ditches (troughs) to a hazardous waste pit and storage lagoons. After alarge volume of waste liquids had accumulated, the storage lagoons were burned off. These firescreated large clouds of black smoke that created concerns about air pollution and the practice washalted. After the practice of burning was stopped, waste liquids were sold to an asphalt company. Also, unknown quantities of waste TCE were sold to a chemical company for recycling. In approximately 1967, the ETA was closed andabandoned (2, 16, 18). In 1981, the lagoons were pumped dry and filled with soil (2).

VOC contamination was found in investigations at the ETA site since 1986, but none of the studiesfocused on the waste pit. In August 1996, EPA sampled the pit and surrounding area, anddetermined that high concentrations of contaminants remained in the pit. A liquid sample taken atthe 16-18 foot depth revealed 25% (250,000,000 ppb) TCE, 4% (43,000,000 ppb) 1,2-dichloroethylene, and almost 1% (910,000 ppb) vinyl chloride. Soil samples from the samedepth revealed TCE at 1,500,000 ppb, along with other VOCs. Results reported from a singlemonitoring well indicated that groundwater was contaminated with 4,200 ppb TCE, 1,600 ppb 1,2-dichloroethylene, and 34 ppb of vinyl chloride (19). During the February 1999 site visit, remedialactivities were underway and the waste pit had been covered to prevent water infiltration. Remediation continued through the fall of 1999 with liquids being pumped from the pit and storedon site for later disposal (20).

Component Test Area (CTA)/Source Area 3 (SA-3)

At the CTA (SA-3 on Figure 1) tests were performed on rocket components, such as gas generators,turbo pumps, and vernier engines until 1967-68 when the mission of Plant 65 changed. A differentcontractor began using the CTA to test small turbo-jet engines. In 1970, another company took overthe operation using the site for identical purposes until it closed the site in 1973. In 1976, the U.S.Government sold the CTA portion of the Test Site to the Water and Wastewater Technical School,Inc. (16, 21).

During the time of operation of the CTA, waste liquids were routed to primary and secondarystorage lagoons and/or a hazardous waste pit. In 1981, the storage lagoons were pumped dry andthe liquids disposed of on site. The storage lagoons were destroyed by bulldozing the existingberms. Sampling performed between October 1991 and January 1993 found TCE in soil at amaximum concentration of 5,910,000 ppb and TCE in groundwater from a monitoring well at amaximum of 200,000 ppb (17). Dye tracing performed in 1996, by the Missouri Department ofNatural Resources, Division of Geology and Land Survey (DGLS) confirmed a pathway from thesecondary lagoon to Gibson Springs (located approximately 10,500 feet to the north-northeast) (21). On August 27, 1998, EPA reached an agreement with the PRP to address soil and groundwatercontamination at the CTA site. The PRP agreed to reduce storm water infiltration into thehazardous waste pit, install a system to contain and treat contaminated groundwater, and conduct anengineering evaluation/cost analysis to identify and evaluate long-term alternatives to addresscontaminated soil (22). During the February 1999 site visit, remedial activities were observed to bein progress. Remediation continued through the fall of 1999 with contaminated groundwater beingpumped from the site, treated, and discharged (20).

Manufacturing Facility/Source Area 4 (SA-4)

The Manufacturing Facility (SA-4 on Figure 1) was built in 1956 and used to make rocket engine parts and assemble rocket engines. Manufacturing processes performed included machining, welding, heat treatment, plating, degreasing, and final assembly. After being purchased by a new owner in 1968, the facility was used to overhaul jet engines. Although, ownership has changed, the facility has continued to be used for that purpose through the present. TCE is believed to have been used by the previous owners. The current owners have used perchloroethylene (PCE, also known as tetrachloroethylene) since September 1992 and have used 1,1,1-trichloroethane (TCA) in the past. Soil samples collected by MDNR in January 1996 found low levels of TCE contamination (maximum of 690 ppb) (2). Additional sampling begun by EPA in 1998 to better determine the extent of contamination has been completed. TCE was found at a maximum level of 3,700,000 ppb in subsurface soils (23). Monitoring wells have been installed to determine the extent of groundwater contamination. Results are not available at this time.

Geology

The Neosho area is underlain by limestone bedrock. This limestone formation is considered karst,with caves, losing streams, and springs. Little research has been conducted into the actualgroundwater flow patterns through the karst materials from the source areas. Dye tracing hasindicated that groundwater from the CTA and ETA reappeared in springs (1). At the CTA site, aconceptual site model indicates that VOC-contaminated soil has affected the perched groundwater inthe karst area and that downward flow over time through the bedrock and/or rapid flushing inresponse to storm events through conduits in the bedrock has contaminated the groundwater andsprings (21). This model may or may not apply to the other source areas.

Upper and lower aquifers exist in the area, separated by a regional confining unit made up of shaley limestone and shales. Thickness of this confining layer varies from 25 to 40 feet. Private wells in the area range in depth from 35 to 525 feet. The wells that penetrate the deep aquifer are almost always open to both aquifers. Groundwater from the shallow and deep aquifer is a highly used resource. Wells in both the shallow and deep aquifers have shown TCE contamination (1). The shallow aquifer (less than approximately 300 feet deep) has shown TCE contamination from non-detectable to a maximum of 310 ppb. The deep aquifer (greater than approximately 300 feet deep) has shown TCE contamination ranging from non-detectable to 11 ppb (3).

Demographics

The 1990 population of Neosho was 9,254 with the population of the city's zip code (64850) being 15,847 (24, 25). Within one mile of the two areas of groundwater contamination (Area 1 and 2), the population is 1,778. Most of these residents would be using private wells and have the potential to be exposed if their private wells became contaminated. Of that potentially exposed population (1,778), 97% are white, with the remaining 3% representing various minorities. Children six years and younger represent 12.8% of the population and those 65 and over account for 11.5% of the population. Women of child-bearing age between the ages of 14 to 44 account for 23% of the population (26).

Site Visits

Numerous site visits have been made to the site and surrounding areas by personnel of DOH, including the initial site visit in December 1994. The most recent site visit of the area, including the ETA and CTA, occurred on February 10, 1999. The site visit consisted of visiting the ETA and CTA sites to observe the remedial activities taking place to prevent further contamination of groundwater. Some of the activities included the modifications of drainage systems, the addition of covers to prevent water movement through contaminated materials, and the installation of monitoring wells to measure groundwater contamination and its movement. During earlier site visits by DOH personnel, it was evident that trespassing had occurred on the ETA and CTA sites, but the 900 Building and the Manufacturing Facility are fenced and secure. During the February 1999 site visit of the ETA and CTA, security had increased, the remedial work was in progress, and signs of recent trespass were not evident. Also a fence is being installed through the woods at the CTA to prevent Missouri National Guard personnel from wandering onto the site from an adjoining area.

Land Use

The southern portion of the Pools Prairie site is located on relatively flat prairie land that gives way to a more rolling woodland to the north. The property that was once Fort Crowder has been converted to an industrial park and the closed Newton-McDonald County Landfill on the southern portion. The northern portion is more remote. Part of this area is used by the Missouri National Guard for training. No residences are located on the old Fort Crowder property, but homes with large sized lots adjoin the property on the north. On the western side a combination of residential and small businesses lie along US Highway 71. To the south and east are scattered large acreage farmsteads that consist of pastureland and some crop land.


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