ATSDR - PHA - Barstow Marine Corps Logistics Base, (a/k/a Marine Corps Logistics Base Barstow), Barstow, San Bernardino County, California

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ATSDR > Public Health Assessments & Consultations

PUBLIC HEALTH ASSESSMENT

BARSTOW MARINE CORPS LOGISTICS BASE
(a/k/a MARINE CORPS LOGISTICS BASE BARSTOW)
BARSTOW, SAN BERNARDINO COUNTY, CALIFORNIA

VI. CONCLUSIONS

Based on an evaluation of available environmental information, ATSDR reached the following conclusions and assigned a public health hazard conclusion category.

Past use of groundwater from the production wells at the Nebo Main Base is not an apparent public health hazard. We have used the qualifier "apparent" because these wells were never sampled for TCE and PCE prior to 1994. Limited indirect data exists to indicate that they were probably not impacted prior to 1994 and direct sampling data from the wells in 1994 showed very low levels of trichlorobenzene. Samples collected in 1999 did not find detectable concentrations of organics.

Past use of the groundwater at the Nebo Main Base for irrigating the golf course is not an apparent public health hazard. We use the qualifier "apparent" because the low levels of two volatile organic compounds (VOCs) were detected in 1994. We analyzed the potential exposure to TCE and PCE if present, via inhalation using a simple box model and found the concentration below levels of concern.

Current and future use of the groundwater at the Nebo Main Base for irrigating the golf course is not a public health hazard since the 1999 samples did not find VOCs.

Past use of drinking water at the Yermo Annex is not an apparent public health hazard because contaminants were not detected or not detected at levels that do not pose a public health hazard.

Current and future use of the groundwater at the Yermo Annex is not a public health hazard because the water is monitored regularly for drinking water standards and by the IRP program for volatile organic compounds.

No public health hazards are associated with the use of off-site drinking water wells. TCE was detected below health concern guidelines at two private wells adjacent to the Yermo Annex. Although TCE was detected above ATSDR's CREG and EPA's MCL at one private well adjacent to the Nebo Main Annex, conservative estimates of potential exposure doses showed that there were likely no health hazards associated with consuming the maximum TCE concentration detected for the exposure period. ATSDR determined that exposure to the private well water is not expected to pose an apparent public health hazard.

No past or present public health hazards are associated with the use of the firing range. However, in the future, if the range is used for other purposes or turned over to other public or private entities for use other than a firing range, MCLB should remediate the soils because of lead contamination.

On the basis of a review of available information on contamination of soil, groundwater, and surface water and sediment, ATSDR concludes that MCLB should be assigned an overall public health assessment conclusion category of No Apparent Public Health Hazard category.

VII. PUBLIC HEALTH ACTION PLAN

The public health action plan (PHAP) for MCLB contains a description of actions taken and those to be taken at and in the vicinity of the base subsequent to the completion of this public health assessment. The purpose of the PHAP is to ensure that this PHA not only identifies potential and ongoing public health hazards but also provides a plan of action designed to mitigate and prevent adverse human health effects resulting from exposure to hazardous substances in the environment. The following actions at MCLB have been completed, are ongoing, or are planned.

A. Completed, Ongoing, and Planned Actions

The Marine Corps completed investigations at the 38 IRP sites and the 247 SWMUs to identify potentially contaminated areas. These investigations, as well as, completed and ongoing corrective actions for these sites are listed in Tables 2 and 3. Three of the major actions that involve the exposure pathways discussed in the preceding sections include:

The areas of the contaminant plume at the Yermo Annex that exceed the MCL will be remediated, except for those areas located directly under the waste management areas. This will be done by extracting groundwater, treating it and recharging the aquifer with the treated water.

The source of contamination of the Nebo North Plume will be removed at Warehouse 2, using a air sparging/soil vapor extraction (AS/SVE) system. Natural attenuation will be used to reduce the groundwater contaminant concentrations outside the source area to levels at or below MCLs.

The groundwater at the Nebo South Plume that exceeds MCLs will be extracted through five groundwater extraction wells and treated with activated carbon units prior to being recharged into the aquifer. A pilot study of the AS/SVE technology is ongoing at this site to determine if the remediation time can be reduced. Institutional controls that include access restrictions to prevent the use of untreated groundwater as drinking water in the areas of the plume (above MCLs) will be implemented.

MCLB has prepared and implemented a Long Term Groundwater Monitoring Plan as required by the Record of Decision (ROD) for Operable Units 1 and 2. The plan is updated annually to address the current status of the groundwater. MCLB has met with the San Bernardino County Department of Health Services and discussed off-base groundwater contamination issues. MCLB is keeping the county up-to-date on the status of the groundwater.

B. Recommendations

ATSDR has one recommendation:

No present public health hazards are associated with the use of the firing range. However, in the future, if the range is used for other purposes or turned over to other public or private entities for use other than a firing range, MCLB should remediate the soils because of lead contamination.

VII. REFERENCES

Almgren and Koptionak, Inc., 1986. Hydrogeological Assessment for Marine Corps Logistics Base, Barstow, California. November 1986.

ATSDR, 1997, ATSDR Hazardous Database System (HazDat) Record of Activity (AROA), record of communication regarding Marine Corps Logistics Base-Barstow, California. January 12, 1999.

ATSDR, 1998c, ATSDR Hazardous Database System (HazDat) Record of Activity (AROA), record of communication regarding Marine Corps Logistics Base-Barstow, California. September 24, 1998.

Bechtel Corporation. 1995. Potential Benefits of the Proposed Mojave River Pipeline Project on the Groundwater Resources of the Mojave River Region. May 1995.

Brown and Caldwell, 1970. Domestic and Industrial Waste Study. December, 1970.

Environmental Research Laboratory, 1981. Report of Water Analysis for Marine Corps Logistics Base for samples collected November 24, 1981. December 16, 1981.

Foster Wheeler Environmental Corporation, 1999. Data for Groundwater Samples, Nebo Main Base, Marine Corps Logistics Base (MCLB), Barstow, California. July 30, 1999.

Jacobs Engineering Group, Inc. 1990a. Summary Report CTO #016 regarding the comprehensive long term environmental action navy cleanup program at Marine Corps Logistics Base, Barstow, California. February 1990.

Jacobs Engineering Group, Inc. 1990b. Navy Clean Program, Sampling and Analysis Report for Public/Private Drinking Water Wells, Yermo Area, Marine Corps Logistics Base, Barstow, California. May 29, 1990.

Jacobs Engineering Group, Inc. 1992. Groundwater Remediation Assessment Technical Memorandum TM-008, Operable Units 1 and 2, Marine Corps Logistics Base, Barstow, California. December 14, 1992.

Jacobs Engineering Group, Inc. 1993a. Notification of Removal Action at the Private Property Well Contaminated with Trichloroethene (TCE) Adjacent to the Nebo Annex, California. March 12, 1993.

Jacobs Engineering Group, Inc. 1993b. On-site Coordinator Report - Removal Action of Trichloroethene Contaminated Off-base Well at Nebo Annex, California. November 3, 1993.

Jacobs Engineering Group, Inc. 1995a. Draft Final Community Relations Plan. Marine Corps Logistics Base, Barstow, California. October 1995.

Jacobs Engineering Group, Inc. 1995b. Draft Feasibility Study Report for Operable Units 1 & 2, Volume 1. Marine Corps Logistics Base, Barstow, California. August 1995.

Jacobs Engineering Group, Inc. 1995c. Draft Remedial Investigation Report for Operable Units 1 & 2, Vol 1 of 10. Marine Corps Logistics Base, Barstow, California. July 1995.

Law/Crandall Inc., 1994. Report of Analytical Results for Groundwater Samples taken at the Nebo Main Base and Yermo Annex on March 24 and 25, 1994. Marine Corps Logistics Base, Barstow, California. May 11, 1994.

MCLB, 1985. Marine Corps Logistics Base-Barstow, AB 8103 Sample Results for Groundwater and Well Construction Date. Marine Corps Logistics Base, Barstow, California. February 25, 1985.

MCLB. 1989. Marine Corps Logistics Base-Barstow, Utilities Section - 3980, Water Plants, Pumps & Motor Information. Marine Corps Logistics Base, Barstow, California. June 12, 1989.

Southwest Division Naval Facilities Engineering Command. 1998. Marine Corps Logistics Base Barstow, Barstow, California, Record of Decision, Operable Units 1 & 2, April 1998.

Southwest Division Naval Facilities Engineering Command. 1996. Marine Corps Logistics Base Barstow California (CTO 294) Draft RCRA Facility Assessment Report, Volume 2. April 1996.

U.S. Bureau of the Census. 1990. Census of Population and Housing. 1990.

U.S. Geological Survey. 1969. Water Resources of the Marine Corps Supply Area, Barstow, California. 1969.

U.S. Geological Survey. 1975. Evaluation of Groundwater Degradation Resulting from Waste Disposal to Alluvium near Barstow, California. 1975.

U.S. Geological Survey. 1997. Geohydrology and Water Quality of Marine Corps Logistics Base, Nebo and Yermo Annexes, near Barstow, California, Water Resources Investigations Report 96-4301. 1997.

U.S. Marine Corps. 1986. Personal communication between Steve Wisbaum, MCLB Barstow, and Stewart Long, San Bernardino County Health Department. March 1986.

U.S. Marine Corps. 1998. Personal communication between Michael Cox, MCLB Barstow, and Audrey Wagenaar, Eastern Research Group, Inc. August 1998.

Western Division Naval Facilities Engineering Command, 1998. Letter to California Regional Water Quality Control Board, Lahontan Region regarding monthly monitoring reports. December 15, 1977.

VIII. PREPARER OF THIS REPORT

Brian Kaplan
Environmental Health Scientist
Federal Facilities Assessment Branch
Division of Health Assessment and Consultation

TABLES

TABLE 1. EVALUATED EXPOSURE PATHWAYS

Pathway Name Source of Contamination Environmental Medium Point of Exposure Route of Exposure Time of Exposure Exposed Population Comments

Past use of the Nebo Main Base production wells for on-base drinking and production. Light industrial activities at MCLB Groundwater Base wells for drinking stopped in 1977. Ingestion
Inhalation
Dermal Past 1998 data: 3,700 people working on base and about 885 working and living on base. The 885 number may include dependents. Production wells apparently not impacted by Nebo North Plume based on monitoring data and production well sample data. See Appendix E for constituents in the Nebo North Plume.

Past, current, and future use of the Nebo Main Base production wells for irrigation. Light industrial activities at MCLB Groundwater Inhalation downwind of golf course during irrigation and downwind of water reservoir Inhalation Past, Current, and Future Unknown but less than 2,000. Past
Contaminants are not detected at levels that are likely to pose a health hazard under past exposure situations, as indicated by conservative dose estimates. Trichlorobenzenes were detected below levels of concern in Production well 2.
Present/Future
Recent analysis did not detect contaminants.

Past use of off-site private wells southeast of the Nebo Main Base Light industrial activities at MCLB Groundwater Private well Ingestion
Inhalation
Dermal Past
TCE has been detected above both the CREG and MCL values. Three families who used the well. Estimate of 12 people, 4 per household. Past
Contaminants are not detected at levels that are likely to pose a health hazard under past exposure situations, as indicated by conservative dose estimates
(Appendix C).
Present/Future
The private well is no longer in use and the residents are receiving water from the city of Barstow, therefore, no present or future exposures are possible.

Past use of the Yermo Annex production wells for on-base drinking and production Light industrial activities at MCLB Groundwater Drinking water wells Ingestion
Inhalation
Dermal Past
TCE has been detected above both the CREG and MCL values. Estimated time of exposure 3 years. Workers at the Yermo Annex of MCLB. Estimate of 1,300 people in 1988. Past
Contaminants are not detected at levels that are likely to pose a health hazard under past exposure situations, as indicated by conservative dose estimates
(Appendix C).
Present/Future
Water treatment systems have been installed on the base production wells to remove organic contaminants, therefore, no present or future exposures are possible.

Past use of off-site private wells east of the Yermo Annex Light industrial activities at MCLB Groundwater Two Private wells Ingestion
Inhalation
Dermal Past
TCE was detected at trace levels, below both the CREG and MCL values. Time of exposure unknown but estimated to be 3 to 5 years. A few families (number not specified) Assumed to be 15 at the most. Past
Contaminants are not detected at levels that are likely to pose a health hazard under past exposure conditions.
Present/Future
Water treatment systems have been installed on the wells as a precautionary measure, therefore, present or future exposures are not possible.

Past, current, and future exposure to soils at the rifle range given present land use. Firing Range Soil Ingestion Past, Current, Future Unknown. Past, Present
No public health hazard since soils are not accessible by public
Future
If range is reused in the future, precautions are needed to insure remediation prior to reuse.

TABLE 2. WATER SUPPLY WELLS AT MCLB¹

Well Year Drilled Status Depth
(Feet BGS) Top of Open Interval (Feet BGS) Bottom of Open Interval (Feet BGS) Normal Pumping Rate

Nebo 1 1942 Out of Service 1968 192 70
161² 151²171² 770

Nebo 2 1958 Out of service 1993 for drinking water. Used for golf course from 1977 to 1993 467 107 407 880

Nebo 3 1947 Used for golf course since 1977. 280 37 280³ 390

Nebo 4 1964 Out of service 1977 348 48 348 1200

Nebo 5 1960 Out of service 1977 456 65 440 630

Nebo 6 1969 Used for golf course since 1977. 336 109² 312² 770²

Yermo 1 1942 Abandoned 1950s 296 142 260 190

Yermo 2 1942 Out of service 1975 174 -- -- 220

Yermo 3 1942 Out of service 1995 214 - 214 940

Yermo 4 1961 350 60 -- 1000

Yermo 5 1969 400 160 400 1200²

Yermo 6 Planned

Sources:
1 - Almgren and Koptionak, Inc., 1986.
2 - U.S. Geological Survey, 1975.

TABLE 3. PARAMETERS AND WELLS SAMPLED 1970, 1976, 1981, 1982, 1994, and 1999

Date General Sample Locations Parameters

Sept. 1970 Nebo Wells 2, 3, 4, 5, and 6.
Yermo Wells, 2, 3, 4, and 5.
Also sampled the unclorinated and chlorinated water supply reservoirs at Nebo and the unchlorinated reservoir at the Yermo Annex Sodium, sulfate, chloride, fluoride, boron, total hardness, pheonols, methylene blue active substances (anionic surfactants), total chromium, ammonia, specific conductance, total dissolved solids.

May through November 1976 Nebo Well 6 and Yermo Well 3 Phenols (unspecified compounds)

November 1981 Nebo Wells 2, 3, and 6
Yermo Wells 3, 4, and 5 Ammonia, sodium, potassium, calcium, magnesium, bicarbonate, carbonate, chloride, sulfate, nitrate, fluoride, hydroxide, pH, specific conductance, alkalinity, total dissolved solids, hardness, langlier index, iron, manganese, copper, zinc, silica, phosphate, methylene blue active substances (anionic surfactants), silver, arsenic, barium, cadmium, chromium, mercury, lead, selenium, endrin, methoxyclor, 2,4-D, alpha-BHC, beta-BHC, delta-BHC, gamma-BHC (lindane), aldrin, dieldrin, 4,4'-DDD, 4,4'-DDT, 4,4'-DDE, endosulfan I, endosulfan II, endosulfan sulfate, PCBs (1016, 1232, 1248, 1260, 1221, 1242, 1254), toxaphene, 2,4,5-TP silvex, heptachlor, heptaclor epoxide, chlordane.

Yermo Well 5 Additional constituents - well specific

Radionuclides (alpha and beta particle activity), radium, chloroform, bromodichloromethane, bromoform, and dibromochloromethane, total trihalomethanes (sum of the previous four compounds).

March 1982 Nebo Wells 2, 3, and 6
Yermo Wells 3, 4, and 5 Radionuclides (alpha and beta particle activity), radium, chloroform, bromodichloromethane, bromoform, and dibromochloromethane, total trihalomethanes (sum of the previous four compounds).

April 1982 Yermo Well 5 Radionuclides (alpha and beta particle activity), chloroform, bromodichloromethane, bromoform, and dibromochloromethane, total trihalomethanes (sum of the previous four compounds).

June and September 1982 Nebo Well 3 and Yermo Well 5 Radionuclides (alpha and beta particle activity) and radium.

May 1994 Nebo Wells 2, 3, and 6; Yermo Wells 3, 4 and 5. Metals, pesticides, VOCs, anions, cations, solids

June 1999 Nebo Wells 3 and 6 Metals, VOCs, SVOCs, anions, solids

TABLE 4. PHENOLS MEASURED AT MCLB

SEPTEMBER 1970¹

NEBO WELL NUMBER PHENOLS (MG/L) YERMO WELL NUMBER PHENOLS (MG/L)

2 0 2 0

3 0.008 3 0

4 0.003 4 0

5 0 5 0

6 0 Unchlorinated Reservoir 0

Unclorinated Reservoir 0
1. Brown and Caldwell, 1970.

JUNE-DECEMBER, 1976¹

DATE NEBO WELL 6 (PPB) YERMO WELL 3 (PPB) SOURCE DATE¹

May 3, 1976 2 3 June 21, 1976

June 4, 1976 6 16 July 13, 1976

July 20, 1976 10 2.5 August 25, 1976

August 10, 1976 83 83 September 23, 1976

September 16, 1976 < 1 28 October 7, 1976

November 1, 1976 180 12 December 6, 1976

November 16, 1976 9 15 December 21, 1976
1. Department of the Navy, Western Division , Naval Facilities Engineering Command to California Regional Water Quality Control Board, Various Dates as Listed.

TABLE 5. PHENOLS MEASURED BY U.S. EPA METHOD 604

COMPOUND ATSDR COMPARISION VALUES (PPB)

4-Chloro-3-methylphenol --

2--Chlorophenol Chronic RMEG Child 50

2,4-Dichlorophenol Chronic RMEG Child 30

2,4-Dimethylphenol. Chronic RMEG Child 200

2,4-Dinitrophenol Chronic RMEG Child 20

2-Methyl-4,6-dinitrophenol Intermediate RMEG Child 40

2-Nitrophenol --

4-Nitrophenol 60 LTHA

Pentachlorophenol CREG 0.3

Phenol Intermediate CREG Child 3

2,4,6-Trichlorophenol CREG 3
U.S.Code of Federal Regulations (CFR) 40, Parts 136 - Revised as of July 1, 1995, Appendix A to Part 136 - Methods for Organic Chemical Analysis of Municipal and Industrial Wastewater

FIGURES

Figure 1. Regional Location of MCLB

Figure 2. MCLB Installation Restoration Program Sites - NEBO Main Base

Figure 3. MCLB Installation Restoration Program Sites - Yermo Annex

Figure 4. Demographic Information

Figure 5. ATSDR's Exposure Evaluation Process

Figure 6. Display of Yermo Annex Plumes and Production Wells

Figure 7. Display of NEBO Main Base Plumes

Next Section Table of Contents

Agency for Toxic Substances and Disease Registry, 1825 Century Blvd, Atlanta, GA 30345
Contact CDC: 800-232-4636 / TTY: 888-232-6348

Department of Health and Human Services

Pathway Name	Source of Contamination	Environmental Medium	Point of Exposure	Route of Exposure	Time of Exposure	Exposed Population	Comments
Past use of the Nebo Main Base production wells for on-base drinking and production.	Light industrial activities at MCLB	Groundwater	Base wells for drinking stopped in 1977.	Ingestion Inhalation Dermal	Past	1998 data: 3,700 people working on base and about 885 working and living on base. The 885 number may include dependents.	Production wells apparently not impacted by Nebo North Plume based on monitoring data and production well sample data. See Appendix E for constituents in the Nebo North Plume.
Past, current, and future use of the Nebo Main Base production wells for irrigation.	Light industrial activities at MCLB	Groundwater	Inhalation downwind of golf course during irrigation and downwind of water reservoir	Inhalation	Past, Current, and Future	Unknown but less than 2,000.	Past Contaminants are not detected at levels that are likely to pose a health hazard under past exposure situations, as indicated by conservative dose estimates. Trichlorobenzenes were detected below levels of concern in Production well 2. Present/Future Recent analysis did not detect contaminants.
Past use of off-site private wells southeast of the Nebo Main Base	Light industrial activities at MCLB	Groundwater	Private well	Ingestion Inhalation Dermal	Past TCE has been detected above both the CREG and MCL values.	Three families who used the well. Estimate of 12 people, 4 per household.	Past Contaminants are not detected at levels that are likely to pose a health hazard under past exposure situations, as indicated by conservative dose estimates (Appendix C). Present/Future The private well is no longer in use and the residents are receiving water from the city of Barstow, therefore, no present or future exposures are possible.
Past use of the Yermo Annex production wells for on-base drinking and production	Light industrial activities at MCLB	Groundwater	Drinking water wells	Ingestion Inhalation Dermal	Past TCE has been detected above both the CREG and MCL values. Estimated time of exposure 3 years.	Workers at the Yermo Annex of MCLB. Estimate of 1,300 people in 1988.	Past Contaminants are not detected at levels that are likely to pose a health hazard under past exposure situations, as indicated by conservative dose estimates (Appendix C). Present/Future Water treatment systems have been installed on the base production wells to remove organic contaminants, therefore, no present or future exposures are possible.
Past use of off-site private wells east of the Yermo Annex	Light industrial activities at MCLB	Groundwater	Two Private wells	Ingestion Inhalation Dermal	Past TCE was detected at trace levels, below both the CREG and MCL values. Time of exposure unknown but estimated to be 3 to 5 years.	A few families (number not specified) Assumed to be 15 at the most.	Past Contaminants are not detected at levels that are likely to pose a health hazard under past exposure conditions. Present/Future Water treatment systems have been installed on the wells as a precautionary measure, therefore, present or future exposures are not possible.
Past, current, and future exposure to soils at the rifle range given present land use.	Firing Range	Soil		Ingestion	Past, Current, Future	Unknown.	Past, Present No public health hazard since soils are not accessible by public Future If range is reused in the future, precautions are needed to insure remediation prior to reuse.

Well	Year Drilled	Status	Depth (Feet BGS)	Top of Open Interval (Feet BGS)	Bottom of Open Interval (Feet BGS)	Normal Pumping Rate
Nebo 1	1942	Out of Service 1968	192	70 161²	151²171²	770
Nebo 2	1958	Out of service 1993 for drinking water. Used for golf course from 1977 to 1993	467	107	407	880
Nebo 3	1947	Used for golf course since 1977.	280	37	280³	390
Nebo 4	1964	Out of service 1977	348	48	348	1200
Nebo 5	1960	Out of service 1977	456	65	440	630
Nebo 6	1969	Used for golf course since 1977.	336	109²	312²	770²

Yermo 1	1942	Abandoned 1950s	296	142	260	190
Yermo 2	1942	Out of service 1975	174	--	--	220
Yermo 3	1942	Out of service 1995	214	-	214	940
Yermo 4	1961		350	60	--	1000
Yermo 5	1969		400	160	400	1200²
Yermo 6	Planned

Date	General Sample Locations	Parameters
Sept. 1970	Nebo Wells 2, 3, 4, 5, and 6. Yermo Wells, 2, 3, 4, and 5. Also sampled the unclorinated and chlorinated water supply reservoirs at Nebo and the unchlorinated reservoir at the Yermo Annex	Sodium, sulfate, chloride, fluoride, boron, total hardness, pheonols, methylene blue active substances (anionic surfactants), total chromium, ammonia, specific conductance, total dissolved solids.
May through November 1976	Nebo Well 6 and Yermo Well 3	Phenols (unspecified compounds)
November 1981	Nebo Wells 2, 3, and 6 Yermo Wells 3, 4, and 5	Ammonia, sodium, potassium, calcium, magnesium, bicarbonate, carbonate, chloride, sulfate, nitrate, fluoride, hydroxide, pH, specific conductance, alkalinity, total dissolved solids, hardness, langlier index, iron, manganese, copper, zinc, silica, phosphate, methylene blue active substances (anionic surfactants), silver, arsenic, barium, cadmium, chromium, mercury, lead, selenium, endrin, methoxyclor, 2,4-D, alpha-BHC, beta-BHC, delta-BHC, gamma-BHC (lindane), aldrin, dieldrin, 4,4'-DDD, 4,4'-DDT, 4,4'-DDE, endosulfan I, endosulfan II, endosulfan sulfate, PCBs (1016, 1232, 1248, 1260, 1221, 1242, 1254), toxaphene, 2,4,5-TP silvex, heptachlor, heptaclor epoxide, chlordane.
November 1981	Yermo Well 5	Additional constituents - well specific
		Radionuclides (alpha and beta particle activity), radium, chloroform, bromodichloromethane, bromoform, and dibromochloromethane, total trihalomethanes (sum of the previous four compounds).
March 1982	Nebo Wells 2, 3, and 6 Yermo Wells 3, 4, and 5	Radionuclides (alpha and beta particle activity), radium, chloroform, bromodichloromethane, bromoform, and dibromochloromethane, total trihalomethanes (sum of the previous four compounds).
April 1982	Yermo Well 5	Radionuclides (alpha and beta particle activity), chloroform, bromodichloromethane, bromoform, and dibromochloromethane, total trihalomethanes (sum of the previous four compounds).
June and September 1982	Nebo Well 3 and Yermo Well 5	Radionuclides (alpha and beta particle activity) and radium.
May 1994	Nebo Wells 2, 3, and 6; Yermo Wells 3, 4 and 5.	Metals, pesticides, VOCs, anions, cations, solids
June 1999	Nebo Wells 3 and 6	Metals, VOCs, SVOCs, anions, solids

SEPTEMBER 1970¹
NEBO WELL NUMBER	PHENOLS (MG/L)	YERMO WELL NUMBER	PHENOLS (MG/L)
2	0	2	0
3	0.008	3	0
4	0.003	4	0
5	0	5	0
6	0	Unchlorinated Reservoir	0
Unclorinated Reservoir	0

JUNE-DECEMBER, 1976¹
DATE	NEBO WELL 6 (PPB)	YERMO WELL 3 (PPB)	SOURCE DATE¹
May 3, 1976	2	3	June 21, 1976
June 4, 1976	6	16	July 13, 1976
July 20, 1976	10	2.5	August 25, 1976
August 10, 1976	83	83	September 23, 1976
September 16, 1976	< 1	28	October 7, 1976
November 1, 1976	180	12	December 6, 1976
November 16, 1976	9	15	December 21, 1976

COMPOUND	ATSDR COMPARISION VALUES (PPB)
4-Chloro-3-methylphenol	--
2--Chlorophenol	Chronic RMEG Child 50
2,4-Dichlorophenol	Chronic RMEG Child 30
2,4-Dimethylphenol.	Chronic RMEG Child 200
2,4-Dinitrophenol	Chronic RMEG Child 20
2-Methyl-4,6-dinitrophenol	Intermediate RMEG Child 40
2-Nitrophenol	--
4-Nitrophenol	60 LTHA
Pentachlorophenol	CREG 0.3
Phenol	Intermediate CREG Child 3
2,4,6-Trichlorophenol	CREG 3