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A. Environmental Pathways

Environmental sampling conducted at the MOTCO site since 1981 hasrevealed contamination in soils, ground water, and sediments. The majority of the on-site contamination is contained in, andassociated with, the waste pits. The primary contaminants ofconcern found both on and off the site include semi-VOCs, VOCsand heavy metals.

On-site contaminants found in soil and ground water may migrateinto other environmental media such as surface water, air andbiota. They may also migrate off site. Contaminants may migratefrom soil with surface-water run-off, over the ground, andsubsequently enter surface-water bodies. Contaminants may betransported downstream until deposited with sediments. Sedimentsmay contribute to ground-water contamination by percolation or tocontamination of the ecosystem by fish or plant uptake. Contaminants in pit waste may leach into the ground water belowthe pits. These contaminants will then migrate in the directionof ground-water flow until degraded by natural processes orremoved by remediation. Contaminants found in surface soil mayadhere to soil particles and be transported by winds or, if theyare volatile, they may enter the air and migrate off site. Eachof these environmental pathways is discussed below with respectto this site.

1. Soil Pathways

Analysis of top soil and subsurface soil samples defined twoprimary areas of soil contamination: southeast of Pit 7 andnorthwest of the site in the area of the abandoned trailer park. Contaminants were also detected east of the site near Pit 5. Most of the top-soil contamination was found outside the siteboundary fence. In the top soil, only benzene was identifiedabove the HAC value; the maximum level found slightly exceededthis comparison value. Subsurface contamination was detected inthe area east of the site.

Top-soil contamination may migrate through surface-water run-offtracking, and in the form of airborne particulate matter. Top-soil contamination can also migrate through the soil tosubsurface levels and ground water as a result of leaching. Surface water and sediment sampling data along with air qualitymonitoring does not support appreciable migration of top-soilcontaminants through surface-water run-off or airborne dispersal. The increase in semi-VOC contaminants observed with increaseddepth suggests that downward migration through the soil may beoccurring.

2. Ground-water Pathways

Contaminants found in ground water may migrate in the directionof ground-water flow vertically and horizontally. They may alsocontaminate surface-water bodies if they are fed fromground-water sources.

Ground-water samples collected from wells installed in theshallow aquifer defined two plumes of contamination, locatedsouth and northwest of the site. The first plume, located southof the site and near Pit 7, extends approximately 500 feet pastthe site boundary. The second plume, northwest of the site andnorth of Pit 2 and Pit 3, extends approximately 275 feet past thesite boundary. Limited contamination was detected in the deepaquifer. Sampling data supports the current migration ofcontaminants through ground-water flow.

3. Surface-Water Pathways

The MOTCO site is in the Highland Bayou drainage basin. Sitedrainage is south and east through a series of drainage ditchesand storm sewers. A large drainage ditch is located on thesouthwestern boundary of the site. Run-off passes through aseries of storm sewers into a marsh area south of the DelIndustries site. Drainage from the site ultimately reaches JonesBay. Galveston Bay is located approximately 2.0 miles from thesite and the Jones Bay/Trinity-San Jacinto estuary isapproximately 1.5 miles south of the site. Surface waterprovides opportunity for migration of soil contaminants. As theyare dispersed, these contaminants can evaporate into the air,accumulate in fish and other wildlife, and leach into the groundwater.

Surface-water samples were collected primarily from drainageditches and marsh areas around the periphery of the site. Themajority of samples were taken off site. Samples taken in theinitial investigation revealed low levels of the volatilecompounds 1,1,2-trichloroethane and 1,2-dichloroethane. Bothcontaminants were from the same site, a drainage ditch on theHL&P right-of-way, west of the MOTCO site. Samples collectedduring the SFSI study resulted in identification of noappreciable levels of contaminants. Migration of contaminantsvia this pathway is unlikely.

4. Sediment Pathway

Sediment samples were taken in conjunction with surface-watersamples. Sediment samples may provide several exposure pathways. Contaminants may enter sediments from surface water throughdissolution and may establish an equilibrium relationship forcommunication of contaminants with surface-water bodies. Sediments also provide sources of contaminant contact with fishand crustaceans. Sediments in drainage ditches may also be asource of contamination of marshes and bays into which theyultimately empty. Lead was detected in sediments up to 483 ppm. No other contaminants were found at levels of concern. Dataresulting from sediment sampling does not support contaminantmigration through sediments as an active exposure pathway inrelation to the MOTCO site.

B. Human Exposure Pathways

Several exposure pathways are possible because of contaminatedmedia and environmental transport at the site.

1. Top Soil:

Inhalation, dermal contact, and ingestion of contaminatedoff-site surface soils are possible routes of human exposure atthis site. The population primarily at risk would be workersinvolved in remediation activities. However, trespassers gainingaccess to the area may be exposed to contaminated soils, as wellas children who might play along the fence.

As a result of frequent hand-to-mouth activity, small children (less than 6 yrs of age) typically ingest 0.2 g of soil per day. The estimated ingestion rate for adults is 0.1 g soil per day. At the MOTCO site, physical barriers exist such that children would not be expected to readily gain access to high levels of soil contamination.

The primary location of top-soil contamination exists immediatelyoutside site boundaries in areas not currently in active use. Anovergrowth of vegetation in these areas provides protection fromsoil erosion as well as a mechanical barrier to reduce the riskof dermal contact. Access to the area is limited due to thepresence of highways, the HL&P right-of-way, and borrow pits.

Because evidence of activities in areas of soil contamination hasnot been observed, exposure pathways involving top-soilcontamination are considered potential rather than completedpathways. Potential for exposure to contaminated soils willincrease during site remediation activities.

2. Waste Pit Contaminants:

On-site waste pit contaminants provide possible exposure, throughdermal contact and inhalation (if pit contents are disturbed),particularly for on-site workers involved in remediation. Eventhough the site is fenced and locked, and the surrounding areasare diked, skin contact with or inhalation of contaminants mayoccur if persons enter the waste pits. The facility is fencedand locked reducing the possibility of trespassers becomingexposed. Areas surrounding the pits are diked reducing potentialfor contact, although exposure to contaminants may occur ifpersons were to enter the area of the waste pits. This exposurepathway is considered a potential exposure pathway for remedialworkers and trespassers, and will be eliminated following siteremediation.

3. Ground Water:

Contaminated ground water may lead to human exposure throughingestion, dermal contact, and inhalation (during showers,bathing, etc.). People may become exposed to contaminants whenthey drink contaminated water, but exposure also occurs duringuse of contaminated water for domestic chores such as washingclothes, taking baths and showers, and washing dishes. Exposureoccurs not only as a result of dermal contact and ingestion, butinhalation of contaminants may be attributed to the naturalevaporation occurring during these activities.

Surrounding neighborhoods obtain their water from public watersupplies that are not directly affected by aquifer contaminationin this area. Existing area private wells are abandoned or areused for nonpotable purposes.

Existing on-site ground-water contamination is present at theMOTCO site, but on-site wells are currently not in operation. Presently, there is no indication of contaminant migration to theDel Industries or Central Freight process wells. Current areawater use does not support the classification of ground-watercontamination as a past or present exposure pathway. However, ifinactive or nonpotable sources of water are used for potablepurposes in the future, a complete exposure pathway would exist.

4. Surface-water Sediments:

Off-site surface-water sediments present in drainage ditches andmarsh areas provide possible human exposure to low levelcontamination through ingestion and dermal contact. The primarycontaminant of concern is lead. Specific populations at riskinclude workers involved in remediation activities as well asworkers employed in activities along the HL&P right-of-way. Trespassers and children gaining access to the area may also beexposed.

5. Biota:

The data in this Addendum indicate that fish and shellfish arenot contaminated with site-related chemicals; therefore, personsconsuming these biota will not be exposed to site-relatedcontaminants. However the pond adjacent to Del Industries andCentral Freight was not sampled. This area is not restricted andfishing may occur. In the event that fishing would occur, thehuman exposure potential has not been defined.

6. Air:

Air exposure pathway analyses were conducted on the basis ofmonitoring data collected in 1981. At that time, no elevated levels of air contaminants were found. Nevertheless, with theimplementation of incineration, air sampling activities hasresumed and air quality is being monitored around the peripheryof the site.


The primary site contaminants consisted of three groups: volatile organics, semivolatile organics, and metals. Thefollowing discussion used the ATSDR Toxicological Profiles for1,1,2-trichloroethane, 1,2-dichloroethane, vinyl chloride,benzene, bis(2-chloroethyl)ether, arsenic, and lead (7-11, 13,16).

A. Toxicological Evaluation

1. Volatile Organics

Appreciable levels of VOCs were found both on and off site in theshallow ground water. The primary VOCs detected were 1,1,2-trichloroethane, 1,2-dichloroethane, vinyl chloride and benzene. In general, these chemicals are toxic to the liver as the resultof their metabolic conversion to highly-reactive chemicalintermediates. Exposures of VOCs related to MOTCO are expectedto be low level and short term, with remediation workersconsidered the primary population at risk.

Limited information is available concerning health effectsrelated to short term low level exposure to VOCs. Short-termeffects resulting from high levels of vinyl chloride exposureinclude dizziness, ataxia, and headache. In addition, long-term,low-dose exposures have resulted in "vinyl chloride disease". This syndrome is characterized by liver, circulatory,integumentary and hematopoietic involvement. The exposed persondevelops poor circulation in the fingers, thickening of the skin,and changes in the blood. Epidemiologic evidence has indicatedthat occupational inhalation exposure to vinyl chloride caninduce tumors of the liver (hepatic angiosarcoma) and otherorgans in exposed workers. However, vinyl chloride levelsassociated with the MOTCO site are considerably lower thanexpected in standard occupational settings (9).

Benzene was found as a contaminant in soil and ground water bothon and off site and in waste materials in the pits on site. Theprimary consideration for health risk with benzene are effects onbone marrow which can result in blood abnormalities and leukemia. Benzene is also a known human carcinogen. Epidemiologic studiesof occupational exposure have indicated that exposure to benzenecan cause bone marrow toxicity. Occupational exposures have alsobeen associated with an increased incidence of blood dyscrasia,aplastic anemia, and leukemia (10).

Due to site location and proximity of highways, it is unlikelythat children or trespassers will gain contact to the shallowground water at the MOTCO site or surrounding vicinity.

3. Bis(2-chloroethyl)ether

A semi-VOC found in appreciable concentrations both on and offsite is bis(2-chloroethyl)ether.

Inhalation exposure to bis(2-chloroethyl)ether is a pathway ofconcern. At the MOTCO site, the primary areas of contaminationare off-site subsurface soil and on-site and off-site shallowground water. Inhalation exposure resulting from contact withcontaminants associated with subsurface soil and ground watermight occur during remediation activities, but would beconsidered highly unlikely. Inhalation of contaminants may occurduring water use if contaminated ground water is used as apotable water source.

Potential exposure to bis(2-chloroethyl)ether may also occur fromingestion and dermal contact with contaminated soils or water. Although remediation activities are not designed to disturb largeamounts of soil or release appreciable quantities of groundwater, workers involved in remediation activities should beconsidered at potential risk for exposure.

This compound has been primarily shown to cause pulmonary damage. Inhalation of the compound results in pulmonary congestion,edema, and hemorrhage. Animal studies have exhibited nohistologic evidence of residual injury resulting from isolatedexposures. Bis(2-chloroethyl)ether causes central nervous systemdepression in animals and skin irritation in both animals and manafter dermal contact. Limited human exposure data oncarcinogenicity exists; however, there are some animal datalinking bis(2-chloroethyl)ether and hepatic cancer.

4. Arsenic

Elevated levels of arsenic were noted in off-site subsurface soilsamples (3 to 50 feet depth). Ingestion of arsenic is theprimary exposure pathway of concern. If excavation of off-sitecontaminated areas would occur, unprotected workers, children andtrespassers gaining access to excavated areas would be at risk ofexposure. Arsenic is quickly absorbed through the stomach andintestines and enters the blood stream but does not tend tobioaccumulate. Local effects of ingested arsenic includeirritation to the digestive tract that results in nausea,vomiting, and diarrhea. Systemic effects include cardiac,circulatory, and neurologic damage. The most characteristicsystemic effect is a pattern of skin abnormalities. Theseinclude dark and light spots on skin and small "corns" on thepalms, soles, and trunk. Dermal contact frequently results inmild to severe irritation of the skin. Arsenic has been reportedto increase risk of cancer, especially of the lung, throughinhalation and the skin through ingestion.

The amount of arsenic required for adverse human health effectsvaries with the chemical and physical form of the arsenic. Dataas to the specific form of arsenic recovered at this site was notavailable. It may be noted, however, that inorganic forms tendto be more toxic than organic forms. In addition, more-solubleforms of arsenic tend to have a higher toxicity than less-solubleforms.

5. Lead

Elevated lead levels were detected on-site and off-site in theshallow aquifer and off-site in subsurface soil samples. Lead isabsorbed through the lungs, gastrointestinal tract, and skin. Lead exposure is of greatest concern in children and pregnantwomen.

Due to more frequent hand-to-mouth activity, young children havea higher exposure potential through ingestion and are moresusceptible to lead toxicity. Lead has been shown to decreaseintelligence scores, slow growth, and cause hearing problems. Athigh levels, lead exposure can cause brain and kidney damage.

Present contact with contaminated soil and ground water isminimized because of the depth of soil contamination and nonuseof the shallow ground water. However, if this ground water wasused for potable purposes in the future, lead exposure may resultfrom ingestion of contaminated ground water. Exposure toremedial workers may occur during remediation activities ifadequate personal protective measures are not used.

B. Health Outcome Data Evaluation

Community concerns have been focused on the incineration ofwastes on site and the possible air emissions into surroundingcommunities. We have not received any reports of concerns ofadverse health outcomes related to the MOTCO site and surroundingcommunities. Based on the evaluation of environmental data, nopast or present pathways of exposure to site contaminants havebeen identified for the surrounding communities.

Galveston County contains numerous refining and petrochemicalplants that are located primarily in Texas City. Texas City liesadjacent to La Marque. Therefore, it would be difficult toattribute any county level or city level (La Marque) differencesin birth outcomes or cancer mortality to the MOTCO site withouthaving additional information on occupational exposures orresidential histories. Based on the lack of past or presentcommunity exposure pathways to MOTCO site contaminants and theclose proximity of the nearest city (La Marque) to variouschemical industries, we did not evaluate the available GalvestonCounty or La Marque health outcome data.


Since there is no evidence of current or past human exposure tohazardous substances and because access to the site isrestricted, this site is currently classified as no public healthhazard. The site could pose a future public health hazard if notremediated, current site conditions change, or remediationworkers fail to follow personal protection guidelines. On-sitepit waste provides physical hazards as well as a health risk dueto possible inhalation of and dermal contact with contents of thepits. The primary population of concern is on-site workers.

Although both on-site and off-site shallow ground water iscontaminated, public utilities provide drinking water to homes inthe MOTCO area. Available information indicates that there areno existing area wells used for potable purposes. There iscurrently no known human consumption of contaminated ground waterand since the contaminated ground water is a Class III aquifer,it is unlikely that the water will be used for human consumptionin the future. If the site is not remediated, however, thecontamination could migrate to the Upper Chicot Aquifer, which isa Class II aquifer. Therefore, the site represents a potentialsource of contamination to deep groundwater and needs to beremediated. On-site and off-site shallow groundwater is heavilycontaminated with volatile organic compounds. During remediationof groundwater, volatilization of these compounds might occur. Remedial workers could be exposed to these contaminants throughinhalation without the appropriate personal protective equipment.

In the documents reviewed, no surface water or biota samplingfrom the Del Industries' pond were done. Therefore, the riskpotential of this area could not be characterized in theAddendum.

The test burn for the liquids incinerator was completed October1990, and the test burn for the solids incinerator was completedJuly 1991. No air samples, however, were available to evaluateduring the preparation of this Addendum. Stack sampling protocols have been developed to determine release of potentialcontaminants during the incineration process. Due to the absenceof data, the incineration process is an indeterminate publichealth hazard.

Present contact with soil and sediment contaminants is limited. Current physical boundaries decrease human contact with the MOTCOsite and peripheral areas. However, during remediationactivities and in the event of future excavation or public use ofareas adjacent to the MOTCO site, exposure to site-relatedcontaminants could cause adverse health effects in the exposedpopulation.

Present remediation activities do not involve excavation ofsubsurface soil. However, in the event of future excavation orpublic use of the site and its peripheral areas of identifiedcontamination, workers and neighboring populations would be atincreased risk of exposure to contaminants through inhalation,dermal absorption, and ingestion.


  1. Restrict access to the waste pits to minimize the risk ofremedial workers falling into the pits.

  2. Sampling of the surface waters and biota of the DelIndustries' pond should be performed to determine whethercontamination is present in these media.

  3. As air monitoring data from the incinerator's stack emissions becomes available, it should be evaluated to ensurethat nearby residential areas are not exposed to site-relatedcontaminants. In addition, EPA should monitor air quality at thesite perimeter and at downwind locations off site. Thesedownwind locations should be selected based upon air modelingavailable. It should be analyzed to determine health risksassociated with this process. Fugitive air emissions duringexcavation activities should also be considered in the airmonitoring program.

  4. During remedial activities, workers should be provided withthe appropriate personal protective equipment in accordance withapplicable Occupational Safety and Health Administration (OSHA)guidelines.

  5. Institutional controls should be implemented to prevent useof contaminated groundwater.

  6. In the event of off-site excavation of subsurface soil,precautions should be taken to restrict access to these areas. Procedures should be implemented to reduce or eliminate dustexposure to workers and nearby populations. In addition, workersshould be provided with the appropriate personal protectiveequipment.

  7. During remediation of groundwater, air monitoring forvolatile organic compounds should be considered if there is apossibility of the volatilization of these compounds andpotential exposure to workers.

  8. It is recommended that ATSDR continue to reevaluate the sitefor any indicated follow-up as additional sampling becomesavailable.


In accordance with the Comprehensive Environmental Response,Compensation and Liability Act (CERCLA) of 1980, as amended, theMOTCO site has been evaluated for appropriate follow-up withrespect to health activities. Because there is no indicationthat human exposure to site contaminants at levels of publichealth concern is occurring or has occurred, this site is notbeing considered for follow-up health activities at this time. However, if emissions from the incineration process or otherenvironmental data become available suggesting that humanexposure to significant levels of hazardous substances iscurrently occurring or has occurred in the past, ATSDR and TDHwill reevaluate this site for any indicated follow-up. Inaddition, TDH recommends community education to residentsconcerning the emissions from the incinerator pilot test.


To respond to community concerns and based on the HARPrecommendations, the following actions have been or will beperformed to meet the needs expressed by the Recommendations ofthis Health Assessment Addendum.

TDH in cooperation with the ATSDR will conduct the following publichealth actions:

  1. As air emission data from the site and incinerationprocess become available, ATSDR and TDH will evaluate this datawith regards to public health impact. This data will also beshared by TDH with the Texas Air Control Board for theirevaluation.

  2. TDH in conjunction with ATSDR will provide communityeducation to residents concerning emissions from the incinerator.

  3. ATSDR and TDH will continue to coordinate efforts withfederal and state environmental agencies in evaluating the site'simpact on public health and will provide recommendations to addresspublic health issues.


Suzanne D. Hahn, D.V.M.
Staff Epidemiologist
Health Assessment Coordinator
Texas Department of Health

Michelle Kelly, M.M.Sc.
Environmental Quality Specialist
Texas Separtment of Health

Jean D. Brender, R.N., Ph.D.
Director, Environmental
Epidemiology Program
Texas Eepartment of Health

Nancy B. Ingram
Administrative Technician
Texas Department of health


Carl Hickam, R.S.
Senior Regional Consultant
ATSDR - Region 6

George Pettigrew, P.E.
Regional Representative
ATSDR - Region 6


William Greim, M.S., M.P.H.
Environmental Health Scientist
Division of Health Assessment and Consultation
Remedial Programs Branch
State Programs Section


This Public Health Assessment Addendum was prepared by the TexasDepartment of Health under a cooperative agreement with the Agencyfor Toxic Substances and Disease Registry (ATSDR). It is inaccordance with approved methodology and procedures existing at thetime the Public Health Assessment Addendum was initiated.

William J. Greim
Technical Project Officer, SPS, RPB, DHAC

The Division of Health Assessment and Consultation, ATSDR, hasreviewed this Public Health Assessment Addendum and concurs withits findings.

Director, DHAC, ATSDR


  1. USEPA (United States Environmental Protection Agency). 1989.Endangerment Assessment - Management of Migration Feasibility Study(FS) for the MOTCO site, LaMarque, Texas, Volume 1. Prepared byWoodward-Clyde Consultants.

  2. USEPA (United States Environmental Protection Agency). 1989.Endangerment Assessment - Management of Migration Feasibility Study(FS) for the MOTCO site, LaMarque, Texas, Volume 2. Prepared byWoodward-Clyde Consultants.

  3. USEPA (United States Environmental Protection Agency). 1988.Supplemental Feasibility Study Investigation - Management ofMigration Feasibility Study (FS) for the MOTCO site, LaMarque,Texas, Volume 1 (draft). Prepared by Woodward Clyde Consultants.

  4. USEPA (United States Environmental Protection Agency). 1988.Supplemental Feasibility Study Investigation - Management ofMigration Feasibility Study (FS) for the MOTCO site, LaMarque,Texas, Volume 2 (draft). Prepared by Woodward Clyde Consultants.

  5. 1990-1991 Texas Almanac, copyright 1989, published by theDallas Morning News, Mike Kingston, editor.

  6. USEPA (United States Environmental Protection Agency). 1981.Initial Investigation of MOTCO Hazardous Waste Disposal Site,LaMarque, Texas (final). Prepared by Black and Veatch ConsultingEngineers.

  7. ATSDR (Agency for Toxic Substances and Disease Registry). 1989. Toxicological Profile for 1,1,2 Trichloroethane. Preparedby the Syracuse Research Corporation. Atlanta, Ga.: ATSDR, PublicHealth Service, U.S. Department of Health and Human Services.

  8. ATSDR (Agency for Toxic Substances and Disease Registry). 1989. Toxicological Profile for 1,2-Dichloroethane. Prepared bythe Clement Associates, Inc. Atlanta, Ga.: ATSDR, Public HealthService, U.S. Department of Health and Human Services.

  9. ATSDR (Agency for Toxic Substances and Disease Registry). 1989. Toxicological Profile for Vinyl Chloride. Prepared by theSyracuse Research Corporation. Atlanta, Ga.: ATSDR, Public HealthService, U.S. Department of Health and Human Services.

  10. ATSDR (Agency for Toxic Substances and Disease Registry). 1989. Toxicological Profile for Benzene. Prepared by the OakRidge National Laboratory. Atlanta, Ga.: ATSDR, Public HealthService, U.S. Department of Health and Human Services.

  11. ATSDR (Agency for Toxic Substances and Disease Registry). 1989. Toxicological Profile for Bis (2-Chloroethyl) ether. Prepared by the Life Systems, Inc. Atlanta, Ga.: ATSDR, PublicHealth Service, U.S. Department of Health and Human Services.

  12. ATSDR (Agency for Toxic Substances and Disease Registry). 1989. Toxicological Profile for Polycyclic Aromatic Hydrocarbons. Prepared by the Clement Associates, Inc. Atlanta, Ga.: ATSDR,Public Health Service, U.S. Department of Health and HumanServices.

  13. ATSDR (Agency for Toxic Substances and Disease Registry). 1989. Toxicological Profile for Arsenic. Prepared by the LifeSystems, Inc. Atlanta, Ga.: ATSDR, Public Health Service, U.S.Department of Health and Human Services.

  14. ATSDR (Agency for Toxic Substances and Disease Registry). 1989. Toxicological Profile for Cadmium. Prepared by the LifeSystems, Inc. Atlanta, Ga.: ATSDR, Public Health Service, U.S.Department of Health and Human Services.

  15. ATSDR (Agency for Toxic Substances and Disease Registry). 1989. Toxicological Profile for Chromium. Prepared by theSyracuse Research Corporation. Atlanta, Ga.: ATSDR, Public HealthService, U.S. Department of Health and Human Services.

  16. ATSDR (Agency for Toxic Substances and Disease Registry). 1989. Toxicological Profile for Lead. Prepared by the SyracuseResearch Corporation. Atlanta, Ga.: ATSDR, Public Health Service,U.S. Department of Health and Human Services.

  17. Sax N.I., Lewis R.J.: Dangerous Properties of IndustrialMaterials (pp 1047-1048). New York: Van Nostrand Reinhold.



July 20, 1984

George Buynoski
Public Health Advisor, CDC

Remedial Alternatives - MOTCO

Don Porter,
Operations Section, Superfund Branch

As requested, staff at the Center for Environmental Health , at the Centers for Disease Control, have the document that you provided entitled "Summary of Remedial Alternative Selection MOTCO". Through our analysis we have attempted to answer two questions. Does the site constitute a significant potential threat to public health? Do the remedial alternatives proposed sufficiently reduce and/or eliminate the possibilities of human exposure to hazardous substances?

For the Centers for Disease Control to consider a site as a potential/actual threat to the public's health several conditions must be satisfied.

  1. There must be toxic substances present at concentrations that would be hazardous to humans.

  2. There must be a human population that could actually/ potentially be exposed.

  3. There must be pathways that are actually/potentially contaminated through which exposure can occur.

The data contained in the report documents the presence of numerous organic volatiles and, base neutrals at concentrations into the thousands of parts per million (ppm). Current standards for air and ground water could very conceivably be acutely or chronically exceeded. Several of the contaminants are designated carcinogens, therefore chronic exposure to even very low levels would be a serious health concern.

The report states that two residential subdivisions are located near the site: Omega Bay is approximately 1500 feet to the west-southwest and Bayou Vista is 1500-2000 feet the south-southwest. There is a private residence 2000 feet to the northwest. Since public health concerns involve possible long-term exposure future development in the area could very likely increase the size of the potentially exposed population.

While we have seen no evidence that indicates that actual exposure is presently occurring, the report states that contamination is migrating from the waste pits.

Releases from the pits have occurred in the past, and several immediate remedial actions have been carried out at the site. There is evidence that the shallow ground water is also contaminated. Since the wastes are found in elevated unlined pits future releases should be anticipated. Climatic conditions, (eg. rainfall, temperature, air currents etc.) would also affect site conditions. Because of the numerous volatiles present, air emissions could also occur. Since the site is secured by a chain link fence with a locked gate exposure by direct contact is a less probable occurrence.

The MOTCO site in its present condition would constitute a significant potential threat to public health and remedial action that would reduce/eliminate potential exposure would be advisable from a public health perspective.

The remedial alternatives designated as "retained" would apparently all adequately address the issue of gross contamination and thereby lessen the potential risk to the public. Selection of a particular alternative can be based on cost and engineering considerations. Waste destruction rather than waste containment is preferable from a public health viewpoint because it alleviates the concern we would have regarding assurances that the integrity of the containment will be maintained and future land utilization will be restricted.

Because of the acknowledged ground water contamination problem, we recognize that the alternatives detailed do not represent the final solution for the MOTCO site. While no evidence has been presented that suggest that potable water sources are being impacted, the probabilities of such an occurrence must be addressed. The site cannot be certified as completely safe by the public health authorities until this issue is resolved. We would be willing to work with you and TDWR on this problem.

Because of the presence of volatiles we are concerned about possible emissions when the site remedial work is undertaken. Appropriate measures to suppress possible releases and an effective site monitoring program would be essential. If requested the Center for Environmental Health would be willing to provide consultation in this area. If it is desired our consultation could also include review and comment on the site safety plan.

I hope these comments will be of some use. If you have any questions please call me.


Site Location Map
Appendix B. Site Location Map


Motco Well and Boring Sites
Appendix C. Motco Well and Boring Sites


vinyl chloride
methylene chloride
carbon disulfide
1,1 dichloroethene
1,1 dichloroethane
total 1,2-dichloroethene
carbon tetrachloride
vinyl acetate
4-methyl-2 pentanone
total xylenes
total volatiles (calculated by adding all values except values denoted as U or B)
gamma-BHC (lindane)
heptachlor epoxide
endosulfan I
endosulfan II
endosulfan sulfate
endrin ketone
benzyl alcohol
benzoic acid
dimethyl phthalate
diethyl phthalate
4-chlorophenyl phenylether
n-nitroso diphenylamine
4-bromophenyl phenylether
butylbenzyl phthalate
total semi-volatiles (calculated by adding all values, except values denoted as U or B)

Table of Contents The U.S. Government's Official Web PortalDepartment of Health and Human Services
Agency for Toxic Substances and Disease Registry, 4770 Buford Hwy NE, Atlanta, GA 30341
Contact CDC: 800-232-4636 / TTY: 888-232-6348

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