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1. ATSDR > Public Health Assessments & Consultations

PUBLIC HEALTH ASSESSMENT

NAVAL INDUSTRIAL RESERVE ORDNANCE PLANT
FRIDLEY, ANOKA COUNTY, MINNESOTA

EVALUATION OF CONTAMINATION AND EXPOSURE

On the basis of MDH's evaluation of environmental information collected during the site characterization and remedial process, MDH concludes that the current contaminant exposure levels from drinking water do not pose a public health hazard or concern. Based on observations made during an April 1997, site tour and review of environmental data reports, MDH has determined that a complete exposure pathway via drinking water exists for TCE. NIROP and UDLP properties are the closest known sources of TCE contamination up stream from the MWW raw water intakes. TCE concentrations are monitored along with 125 other analytes at Minneapolis Water Works as part of their water quality monitoring program. After the raw water (river water) is treated, it is distributed to approximately 500,000 people in the greater Minneapolis-St. Paul metropolitan area. This water that has been treated to meet all the Federal Safe Drinking Water Act's requirements is called finished water.

The earliest know detection of NIROP/UDLP related contamination in the MWW intakes was in raw water samples collected between 1981 and 1983 for the FMC Record of Decision. Based on 40 samples collected during this time the following contaminants were identified: TCE found 25 times ranging from 0.2 to 3.1 µg/l; 1,1,1-trichloroethylene detected twice at 1.2 and 1.4 µg/l; 1,2-dichloroethylene detected five times all approximating 0.6 µg/l; and 1,1-dichloroethylene detected twice at 0.3 µg/l. (7) Because the exact sampling locations for this data set has not been identified and the data is limited to 40 samples all of which may not be from the same location, this data is being not used for the tables and charts. Instead the more extensive MDH data base for VOC contamination in finished and raw water was used for the tables and charts. The TCE concentrations in the two data sets are similar.

MDH records show low levels of TCE in the MWW finished water 27 times ranging from 0.1 to 1.3 µg/l in the past 16 years (see tables 18 and 19). The highest TCE concentration detected in finished water (1.3 µg/l) is 1/4 the MCL of 5µg/l. Any concentration of TCE below the MCL is considered acceptable for a lifetime of exposure. No other site related contaminants have been detected in the finished water.

As required by the Federal Safe Drinking Water Act, the MCLs are maximum permissible concentrations of a contaminant in water delivered to any user of a public water system. The MCLs are based on health as well as the economic and technical feasibility of detection and treatment. This is in contrast to the Minnesota Department Health HRLs which are based only on human health effects. HRLs are health-based criteria for drinking water contaminants. HRLs are used for four general purposes: advice for private wells, environmental review, and site assessment criteria. For contaminants with a non-cancer endpoint, the HRL is a concentration that is thought to be safe for ingestion over a lifetime. For a contaminant that is a suspected carcinogen, the HRL is a concentration where the cancer risk from ingestion of the contaminated water is considered negligible. MDH considers an incremental addition to a lifetime cancer risk of one in 100,000 to be negligible. This means that if 100,000 people were to ingest water with a contaminant concentration at the HRL for a lifetime, no more than one individual would be expected to develop cancer as a result. To keep this in perspective, the HRL for TCE is 30 µg/l, the MCL for TCE is 5 µg/l and the highest TCE concentrations found in the finished water is 1.3 µg/l in 1985.

Because contamination remains in the soil and groundwater at the NIROP and UDLP sites, an evaluation of potential pathways at each of the waste sites is presented below.

B.1 Naval Industrial Reserve Ordnance Plant (NIROP) Superfund Site
The identification and characterization of all potential Areas of Concern (AOCs), source areas, and Solid Waste Management Units (SWMUs) on NIROP property is ongoing and beyond the scope of this evaluation. The following sections will evaluate contamination on site and the potential for receptors to be exposed.

B.1.a Ground Water Contamination Operable Unit 1 (OU1)
OU1 consists of plant wide groundwater. OU1 has exceeded HRLs and MCLs in groundwater for TCE and other VOCs. Appendix C show TCE concentrations for monitoring and shallow drift wells from 1993-1997. Appendix D tables list HRL and MCL exceedances for each well at NIROP from first time the well was sampled to 1997. The remedial response for this site is pump and treat. Figure 4 lists TCE concentrations found in Anoka County Park groundwater.

Current Pathways

Air (outdoor): Air is not likely to be an exposure pathway because most of the site is covered with pavement or buildings. To date, no outdoor air quality impact studies from contaminated groundwater vapor migration have been conducted. Should soil vapor gas reach the surface, it would likely be diluted with ambient air to levels below health concern. A study may not be warranted based on ambient air dilution factors and the lack of long term exposure to receptors.

Air (indoor): Under current conditions indoor exposure via soil vapor migration is not known to be occurring.In the case of indoor construction, the foundation may be opened potentially allowing soil vapor to infiltrate the building. In such cases, the Navy must first grant written consent to a contractor to open the foundation. Before permission is granted a work plan, which includes worker safety procedures are submitted to the Navy. To date no soil vapor gas migration studies have been conducted.

Soil: Soil is not likely to be an exposure pathway because most of the site is covered with pavement or buildings and small grassy areas. Dermal contact is not likely to occur on site under present conditions except when the foundation is opened for construction and excavations. In such cases, the soil is not likely to be contaminated from groundwater unless a free product is present directly below soil of concern.

Groundwater: Although a completed pathway exists via groundwater to surface water to drinking water, it is not a humanhealth risk under current conditions, based on the limited raw water and more thorough finished water data collected at the MWW. A more comprehensive sampling plan is needed to assess the impact of Site related contamination on the MWW intakes. Based on the finished water data, winter appears to be the season when the water supply is most affected (see figures 18 and 19). There are no drinking water wells on site or down gradient before groundwater discharges to the river.

Potential Future Pathways
If future activities at NIROP include excavation within the contaminant plume (saturated and unsaturated zones), exposures may occur via inhalation of soil gases and/or dermal contact. A future exposure scenario could occur from the volatilization of soil gases into nearby buildings and sewer system. Because the effluent from the extraction system is was recently being discharged to the sewer system, a potential exposure pathway exists for a sewer system worker via inhalation and dermal contact with contaminated water and vapors.

Once the groundwater treatment plant is in use, there will be emissions from its exhaust stake to the ambient air. However, based on modeling projections, the groundwater treatment plant is expected to be well below the MPCA screening emissions rate and as such is not a health concern. (27) However, if the groundwater treatment system (Phase II) is reconfigured, the outdoor air pathway will have to be re-evaluated for emissions.

Use of contaminated groundwater prior to treatment may result in ingestion, inhalation and/or dermal exposure that could pose a public health hazard.Based on the large TCE fluctuations in well 27S (see figure 23, for TCE concentrations in wells closest to the river), and the new findings from the cone penetrometer investigation in Anoka County Park, it is possible that higher levels of TCE could impact MWW.

B.1.b On Site Subsurface Source Areas In Unsaturated Zone Outside Naval Industrial Reserve Ordnance Plant Building Operable Unit 2 (OU2)
All known sources (buried drums and contaminated soil) for this operable unit have beenremoved/remediated; however, contaminated water remains at each of these sites. Based on the extent and concentrations of contaminants in the groundwater plume at each removal site, other contaminant sources may remain.

Current Pathways
Air (outdoor): Exposure to identified site subsurface source area contamination is not likely because all known sources have been removed.

Soil: Exposure to identified site subsurface source area contamination is not likely because known source areas have been removed.

Groundwater: For this operable unit, groundwater is not a current pathway by definition (unsaturated zone).

Potential Future Pathways
If future activities at NIROP include excavation within any contaminant source areas, exposures may occur via inhalation of soil gases and/or dermal contact. Another future exposure scenario is the volatilization of soil gases into nearby buildings. There is also potential for any remaining contamination in this operable unit to leach into groundwater. Use of contaminated groundwater prior to treatment may result in ingestion, inhalation and/or dermal exposure that could pose a public health hazard. However, the institutional controls including future land use (industrial), and private well limitations on site should prevent exposures in the future.

B.1.c On Site Subsurface Source Areas in Saturated and Unsaturated Zone Beneath the Naval Industrial Reserve Ordnance Plant (NIROP) Building and on Site Subsurface Areas Outside the NIROP Building in Saturated Zone Operable Unit 3 (OU3)
Data for this operable unit will be available in late 1998, and will be reviewed by MDH in late 1999. The data will help characterize potential source areas under the NIROP building. Based on the isoconcentration maps for TCE in the shallow drift in the 1996 and 1997 Annual Monitoring reports, it appears that source areas exist under the building.Soil data for this operable unit will be available in late 1998.

Current Pathways
Air (outdoor): Outdoor air is not an exposure pathway because most of the site is covered with pavement or buildings. In addition, the extraction system is removing source contamination in the groundwater.

Air (indoor): No indoor air soil vapor gas data appear to exist for groundwater related contamination. The operation of the extraction system limits the migration of soil vapor gas into the building. Furthermore, the large open spaces in the facility would greatly reduce contaminant concentrations.

Soil: This is not a pathway because most of the site is covered with pavement or buildings. Dermal contact is not likely to occur on site under current conditions as long as foundation remains intact.

Groundwater: Contaminated groundwater is being captured by the extraction system as it exits from under the facility. However, residual contamination from this operable unit is present in Anoka County Riverfront Park beyond the capture zone of the extraction system. This contamination appears to be discharging into the Mississippi.

Potential Future Pathways:
If future activities at NIROP include excavation within the contaminant plume, exposures may occur via inhalation of soil gases and/or dermal contact. Another future exposure scenario is via volatilization of soil gases into the facility. Use of contaminated groundwater prior to treatment may also result in ingestion, inhalation and/or dermal exposure that could pose a public health hazard. However institutional controls, including an excavation safety plan, and private well limitations on site should prevent exposures in the future.

B.2 United Defense Limited Partnership (UDLP)
The identification and characterization of all Areas of Concern (AOCs), source areas, and Solid Waste Management Units (SWMUs) on UDLP property is on going and beyond the scope of this evaluation. The following sections will evaluate contamination pertaining to UDLP property and the potential for receptors to be exposed.

B.2.a Groundwater Remedial Action (FMC Superfund Site)
Groundwater contamination above MCLs and HRLs remains on site. See Appendix E for tables listing exceedances of MCLs and HRLs. This data set is a historical record of what groundwater contaminants have been identified on site. Appendix F contains a graph illustrating the amounts of TCE extracted with the groundwater system.

Air (outdoor): Outdoor air exposure via soil vapor gas from contaminated groundwater is not of health concern. Any gases that migrate to the surface would be diluted with ambient air to levels below health concern. In addition, the site is isolated away from buildings and foot traffic.

Soil: Although residual soil contamination remains on site, under current site conditions exposure to soil contamination is not probable.

Groundwater: There are no groundwater receptors on site. Contaminated groundwater is being captured by the extraction system and discharged to the sanitary sewer and is treated at the local waste water treatment plant. However, it is difficult to ascertain if the plume has been completely contained based on the current monitoring network. Contaminated groundwater not captured by the extraction system will likelydischarge to the Mississippi River up gradient to the MWW's intakes.

Potential Future Pathways
Should future site conditions include excavations, dermal and inhalation exposures to groundwater contaminants are possible. Another potential exposure pathway scenario is to a sewer system worker who could be exposed via inhalation and dermal contact with contaminated water.

B.2.b Containment Treatment Facility (CTF)

Air (outdoor): Exposure to the gas extraction system effluent is a remote possibility because the site is isolated. Furthermore, the concentrations of the effluent gas are low to start with and would be diluted further by ambient air (see section A.2.b).

Soil: Exposure to site related soils is not possible unless the CTF was excavated.

Groundwater: Under current site conditions exposure to CTF leachate is not likely. There are no groundwater receptors on site, and if the CTF was to leak, the contaminants would likely be captured by the groundwater extraction system.

Potential Future Pathways
A potential exposure pathway exists for workers in the sewer system.

B.2.c RCRA Subsurface Source Area Investigation Under UDLP Portion of Building
Based on the 1996 and 1997 Annual Monitoring Reports and TCE isoconcentration maps, investigation of source areas under UDLP's portion of the main building is warranted.

Air (outdoor): To be determined.

Soil: To be determined.

Groundwater: To be determined.

Potential Future Pathways
To be determined.

CONCLUSIONS

On the basis of MDH's evaluation of available environmental information collected during the site characterization and remedial process, MDH reached the following conclusions and assigned public health conclusion categories.

MDH determined that NIROP/UDLP sites pose no apparent human health hazard based on data reviewed.

1. Groundwater under the site is contaminated with VOCs, primarily TCE. Other contaminants have also been identified above HRLs and MCLs in the groundwater the NIROP and UDLP sites. Some VOCs have migrated with the groundwater to off-property areas. A MPCA surface water assessment has determined that groundwater discharge from the NIROP Site exceeds surface water quality standards designed to protect the Mississippi River as a public water supply. The only known drinking water receptor to the NIROP and UDLP sites is the Minneapolis Water Works (MWW) that distributes to 500,000 people is located less than 1 mile down stream. NIROP off property plume migration is in the direction of the MWW and discharges into the Mississippi River from Anoka County Park.. The discharge point for the UDLP ground water plume is not known. TCE has been detected in the MWW finished water (27 times) but all the TCE detects have been below the Maximum Contaminant Level (MCL) of 5 µg/l). Finished water is sampled quarterly for volatile organic compounds (including TCE). The raw water has been sampled for TCE annually by UDLP for the past eight years with no detections. However, the method detection limit was too high to detect the concentrations found in the finished water. MDH and MPCA sampling efforts have detected TCE in river water just north of the MWW in low concentrations.



2. Groundwater contaminant source areas underneath the NIROP/UDLP facilities are being investigated. There is only one Prairie du Chien monitoring well (well 43) down gradient of the NIROP/UDLP facilities. This well has not been monitored adequately to determine the extent which this regionally important bedrock aquifer is impacted from the NIROP/UDLP past operations. UDLP has not adequately characterized its off-property groundwater plumes at the FMC Superfund Site. Based on groundwater flow directions, portions of this plume may discharge to the Mississippi River immediately up river to the MWW's intakes.



3. Anoka County Park groundwater is contaminated with TCE with concentrations up to 37,300 µg/l. The contamination is beyond the capture zone of the groundwater remedy at NIROP. The buried drums found in Anoka County Park next to the Mississippi River are part of an old dump site that has not been characterized.



4. The mass and concentrations of contaminated groundwater discharging to the Mississippi River from the NIROP/UDLP sites have not been determined. Annual fluctuations of TCE concentrations in the wells nearest the river at the NIROP Site have been considerable. The off-property groundwater plume migration and concentrations at FMC Superfund Site have not been well characterized.



5. The treatment system at the MWW was not specifically designed to treat for VOCs. However, there are several stages in the treatment process where water is aerated thereby allowing VOCs to volatilize. In addition, VOCs may be removed in the treatment process when a slurry of activated carbon is used to treat for color and taste. (2) (7) The MWW does not have a back up water supply; it has only a day reserve supply. The MWW intakes draw water from the Mississippi River for treatment and distribution to approximately 500,000 people in the Twin Cities Metro area. The raw water is monitored once a year by UDLP. For monitoring purposes, the raw water tap in the MWW laboratory appears to be a safe and practical way to sample raw river water.



6. Based on available information, MDH concludes that contamination in the MWW water supply from the NIROP/UDLP sites pose no apparent public health hazard under current conditions since there is no indication that the public is being exposed to site-related contaminants above health-based standards. However, TCE has been detected in finished water 27 times (see table 1 and graph 1) all below the MCL. The potential for TCE concentrations in drinking water to exceed drinking water standards needs further evaluation. This is because there are fluctuations in TCE concentrations in the wells nearest the Mississippi River, TCE has been found in groundwater at Anoka County Riverfront Park, and volume and concentrations of contaminated groundwater discharging to the river are not known. Access to NIROP and UDLP properties is limited. There are no well receptors. Future land use will likely remain industrial.



7. MDH has no records of NIROP wells 2 and 3 and UDLP well 1 being sealed according to Minnesota Well Code.

PUBLIC HEALTH ACTION PLAN

The Comprehensive Environmental Response, Compensation, and Liability Act of 1980, as amended, requires ATSDR to perform public health actions needed at hazardous waste sites. No public health actions are currently needed because there are no exposures at NIROP and UDLP at levels that pose a public health hazard; however, MDH/ATSDR recommend the following actions to further characterize potential public health hazards at the two Superfund sites:

1. All source areas for the groundwater contamination need to be identified, and a better understanding of the horizontal and vertical extent of contaminated groundwater is needed. For example, increased efforts to monitor the Prairie du Chien aquifer down gradient of the NIROP and FMC sites, and delineation of off-property groundwater plume migration for all groundwater plumes related to the NIROP and FMC Superfund Sites are needed.



2. Consideration should be given for the collection of raw water at the raw water tap in the MWW laboratory as a more practical way to sample raw river water. Present sample collection practices require removal of a floor grate (4ft.x2ft.) and dropping a bailer down approximately 15 ft. to reach the water. Samples collected in the winter of 1997 at the raw water tap in the MWW laboratory contained TCE at 0.2 µg/l with a detection limit of 0.1 µg/l and this corresponded with another sample collected up stream from the MWW in the Mississippi River. The river sample also contained 0.2 µg/l with a detection limit of 0.1 µg/l.



3. Increased monitoring of the MWW raw water intakes is warranted. MDH recommends that the raw water be sampled monthly using MDH method 465 and MDH Low Level Vinyl chloride method 560 for two years to take into account seasonal variations. The detection limit should be 0.1 µg/l for TCE and 0.2 µg/l for vinyl chloride. After the 2-year sampling period the sampling plan should be reassessed.



4. Wells 1, 2, and 3 should be sealed according to Minnesota Well Code.

PREPARERS OF REPORT

Minnesota Department of Health
Daniel F. Peña
(Health Assessor)

Minnesota Department of Health
Richard Soule
(Hydrogeologist)

GLOSSARY

REFERENCES

Bibliography

1. Minnesota Pollution Control Agency, Correspondence to Douglas Hildre (UDLP Environmental Control Manager) RE: RCRA Permit Modifications MN317022914. November 5, 1997.



2. Basewide Environmental Survey For Transfer (Draft) For Naval Industrial Reserve Ordnance Plant Fridley Minnesota Southern Division Naval Facilities Engineering Command August 1997 Brown & Root Environmental.



3. Record of Decision For Ground Water Remediation Naval Industrial Reserve Ordnance Plant Fridley, Minnesota. September 28, 1990.



4. Site Management Plan NIROP Fridley, Southern Division Naval Facilities Engineering Command North Carolina 29419-9010. Minnesota January 1998.



5. Authorization to Discharge And to Construct, Install And Operate A Wastewater Disposal System Under The National Pollutant Discharge Elimination System (NPDES)And State Disposal System Permit Program. Permit No. MN0000710., October 31, 1996.



6. Remedial Investigation Report For The Soils Operable Unit at The NIROP Fridley, Minnesota. RMT Inc. Madison ,WI. September 1996



7. Completion Report for Removal Action at North 40, NIROP, Fridley, MN., Morrison Knudson Corporation. North Charleston, South Carolina, October 1996.



8. United States Environmental Protection Agency, Superfund Record of Decision For FMC Corporation., Minnesota . September 1987.



9. United States Environmental Protection Agency, Five Year Review Report, FMC Corporation Site, Fridley, Minnesota. September 30, 1992.



10. Agency For Toxic Substances And Disease Registry, Kurt Manufacturing Company; Site Review And Update, Fridley, Anoka County, Minnesota. CERCLIS NO. MND059680165. January 1997.



11. Agency For Toxic Substances And Disease Registry, Health Assessment For Kurt Manufacturing Company; , Fridley, Anoka County, Minnesota., CERCLIS NO. MND059680165. April 1989.



12. United Defense/FMC, Annual Monitoring Report For 1996 Groundwater Extraction System, June 1997.



13. United Defense/FMC, Hazardous Facility Annual Waste Report - 1997 Containment Treatment Facility. Armament Systems Division of United Defense. Groundwater Extraction System, June 1997.



14. Minnesota Pollution Control Agency, Correspondence to Mr. Douglas Hildre Environmental Control Manager United Defense Limited Partnership (FMC Corporation Superfund Site), RE: FMC Corporation Superfund Site, Attachment 1, Idem 5, December 2, 1994.



15. Minnesota Pollution Control Agency, Correspondence to Mr. Douglas Hildre Environmental Control Manager United Defense Limited Partnership (FMC Corporation Superfund Site), RE: FMC Corporation Superfund Site, Attachment 1, Idem 10, December 18, 1995.



16. Metropolitan Council Environmental Services, Industrial Discharge Permit Number 2020 For Site Located at: Armament Systems Division (FMC), February 11, 1997.



17. United Defense (FMC/UDLP), 1997 Hazardous Waste Annual Report For The Containment Treatment Facility. February 1998.



18. Environmental Protection Agency, Ambient Water Quality Criteria For Trichloroethylene, EPA 440/5-80-077, October 1980.



19. Minneapolis Water Works (MWW), Correspondence to Mr. Whitaker (MWW Engineer) Pertaining to Supplemental Groundwater Resources In Anoka County Park. November 22, 1980.



20. Pollution Control Agency, Assessment of impacts to Mississippi River from a contaminant groundwater plume from the Naval Industrial Reserve Ordnance Superfund Site, David Maschwitz Memorandum, July 9, 1997.



21. U.S. Navy Covenant Deferral Request For The Naval Industrial Ordnance Plant Fridley, Minnesota Draft, Version March 31, 1998.



22. John Pollock, CTF Project Manager. Minnesota Pollution Control Agency Phone Conversation. April 8, 1998.1998.



23. FMC Corporation Naval Systems Division: Closure Alternatives Study For Area C at The Naval Industrial Reserve Ordnance Plant, RMT Inc. Madison, Wisconsin, October 1991.



24. United Defense Limited Partnership, Former Storage Area C Naval Industrial Reserve Ordnance Plant, Wenck Associates Inc., July 1997.



25. Minnesota Pollution Control Agency Five Year Report: FMC Corporation Site Fridley, Minnesota. March 30, 1999.



26. Minnesota Pollution Control Agency Five Year Report: FMC Corporation Site Fridley, Minnesota. March 30, 1999.



27. Morrison Knudsen Corporation, Calculation of Site Specific Allowable Emission Rates Groundwater Treatment Facility, NIROP Fridley Minnesota. September 1998.



28. Naval Industrial Reserve Ordnance Plant: 1996 Annual Monitoring Report Fridley Minnesota. Brown and Root Environmental. April 1997



29. Naval Industrial Reserve Ordnance Plant: 1997 Annual Monitoring Report Fridley. Brown and Root Environmental. Minnesota. March 1998

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