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HEALTH CONSULTATION

RIDGEFIELD PRIVATE WELL SURVEY
(a/k/a PACIFIC WOOD TREATING CORPORATION)
RIDGEFIELD, CLARK COUNTY, WASHINGTON


BACKGROUND AND STATEMENT OF ISSUES

The Washington State Department of Health (DOH) conducted a survey to identify existing private wells near the former Pacific Wood Treating Corporation (PWT) site located in the City of Ridgefield, Clark County, Washington. This health consultation summarizes the procedure and results of the well survey and evaluates the past worst-case scenario of contamination in the City's water supply to determine if health effects would occur. DOH prepares health consultations under a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR).

The former PWT facility, on about 41 acres, is located at 111 West Division Street, Ridgefield Washington. Burlington Northern Railroad is on the east border of the site, and Ridgefield Marina is on the south. Lake River, a side channel of the Columbia River, forms the west border, and Carty Lake and Ridgefield National Wildlife Refuge are on the north border. The facility operated from 1964 to 1993, pressure-treating specialty wood products with pentachlorophenol (PCP), creosote and copper/chromium/arsenic (CCA) solutions. Several site and facility investigations conducted over the years have shown groundwater contamination on and off the site.1, 2, 3, 4 Pentachlorophenol (PCP) (0.31- 4.0 micrograms per liter [g/L]) and naphthalene (1g/L), a polycyclic aromatic hydrocarbon (PAH), were detected in City water-supply wells in the 1980s. Subsequently, these wells were abandoned as drinking-water sources and were replaced with new wells about one-half mile upgradient.4

Several monitoring wells have been installed in and around the PWT site. The plume of contaminated groundwater in the shallow aquifer has moved north towards Carty Lake and Ridgefield National Wildlife Refuge. Maximum levels of 16 µg/L PCP and 9.4 µg/L trichloroethylene (TCE) have been found in off-site groundwater wells near Carty Lake and Ridgefield National Wildlife Refuge.3,5 A steam-injection and extraction system was installed in 2002 to remove contaminants from groundwater at the PWT site.5, 6, 7


DISCUSSION

Discussions with the Washington State Department of Ecology and the Southwest Washington Health District indicated that no drinking-water wells are located near the PWT site. However, DOH did not locate any record of the well survey done for the area. This survey was conducted to identify any wells that might be exposure points for contaminants in groundwater originating at PWT.

The survey area was defined using Arcview® geographic information system (GIS) software by drawing a 500-foot radius around the PWT site. The resulting map was provided to the Clark County Department of Assessment and Geographical Information System (GIS) to obtain a list of tax parcel numbers and the names and addresses of property owners within the area to be surveyed. All property owners in the survey area were sent letters and forms (Appendix A) to submit well-construction information. The basic intent of the survey was to confirm the lack of private drinking-water wells in the area near PWT and to evaluate past, worst-case human exposure that resulted from contamination of the City's water supply.

Table 1 shows that responses were received from 36% of those surveyed. All respondents said they were either on a municipal water system or had no well or water source. It is therefore unlikely that exposure to PCP contamination in drinking water is occurring.

Table 1.

urvey of private wells near the former Pacific Wood Treating facility, Ridgefield, Washington, 2003.
No. of property owners % of effective sample
Survey sample 56 NA
Non-respondents 33 59
Respondents 20 36
Returned mail, no forwarding address 3 5

NA - Not applicable

Past Exposure to Naphthalene and Pentachlorophenol

Naphthalene and PCP data from drinking water wells were screened using ATSDR and U.S. Environmental Protection Agency (EPA) health-based criteria (comparison values). Contaminant concentrations below comparison values are unlikely to pose health threats and were not evaluated further in this health consultation. Contaminant concentrations exceeding comparison values do not necessarily pose health threats but were evaluated further to determine whether they are at levels that could result in adverse human health effects.

See Table 2, naphthalene and PCP were the only chemicals detected in the City's drinking water. Because naphthalene concentrations did not exceed its health comparison value and, as a result, do not pose public health hazards, no further evaluation for naphthalene was conducted.

No current exposure to PCP in drinking water exists. After PCP was detected in a composite sample at 4g/L in November 1986, the well field remained in service until 1987 then was discontinued for use as public wells. Past exposure is difficult to assess because of the limited data available. In a single composite sample of the public drinking-water supply, PCP exceeded its cancer and noncancer health comparison values (Table 2). Because of the limited data, DOH is unable to determine whether concentrations of PCP or naphthalene were higher in the past. Potential noncancer and cancer effects estimated from past exposure to PCP in drinking water are evaluated below.

Table 2.

Analytic result of a drinking water composite sample (µg/l) taken in 1986 from public water-supply wells, Ridgefield, Clark County, Washington.
Contaminant Maximum concentration Comparison value EPA cancer class Comparison value reference
Naphthalene 1 100 D LTHA
Pentachlorophenol 4 0.2 B2 CREG

LTHA - EPA's Lifetime Health Advisory for drinking water
CREG - ATSDR's Cancer Risk Evaluation Guide

Noncancer effects

To evaluate possible noncancer effects from past exposure to PCP in drinking water, an exposure dose was calculated and then compared with a minimal risk level (MRL) and oral reference dose (RfD). RfDs and MRLs are doses below which noncancer adverse health effects are not expected to occur.

A level of uncertainty exists when defining an MRL or RfD because of uncertainty about the quality of data on which it is based. To account for this uncertainty, "safety factors" are used to set RfDs and MRLs below actual toxic effect levels (e.g., Lowest Observed Adverse Effect Level [LOAEL]). This approach provides an added measure of protection against the potential for adverse health effects to occur. For chronic oral exposure to PCP, the MRL is 0.001 milligrams/kilogram/day (mg/kg/day). Animal studies have shown that oral exposure to PCP can have adverse effects on the liver and kidney and on the nervous, endocrine, immune, and reproductive systems. 8

Exposure dose calculations for PCP comparison values are provided in Appendix B. The maximum concentration of 4 µg/L PCP in the City's drinking-water wells in 1986 exceeds both the health comparison value of 0.2 µg/L and the MCL of 1 µg/L. These wells were then abandoned in 1987 as drinking-water wells. The estimated dose for children drinking an average of 0.9 liter of water per day at this level would be equal to 4 µg/day or 0.004 mg/day consumed. Because a child weighs an average of 15 kg, the child would receive an exposure dose of 0.0002 mg/kg/day, which is less than the RfD of 0.03 mg/kg/day. Adults drink an average of 1.4 liters per day and weigh about 72 kg; therefore they would be exposed to approximately 0.00007 mg/kg/day, which is also less than the RfD. The maximum level of PCP found in the wells is not expected to result in any noncancer health effects.

Cancer effects

EPA classifies PCP as a Group B2 probable human carcinogen, using inadequate human but sufficient animal studies. The maximum concentration of PCP in drinking water of 4 µg/L is 20 times above the Cancer Risk Evaluation Guide (CREG) of 0.2 µg/L. PWT came into existence in 1964, and the wells were abandoned in 1987. Assuming that the contamination affected the well immediately, a dose was calculated for a child growing to adulthood over 23 years (Appendix B). The theoretical excess cancer risk for such a person is estimated at about 4 in 1,000,000, a very low cancer risk. In this worst-case scenario, the levels of PCP in the City's drinking water would not be expected to result in adverse health effects.


CHILD HEALTH CONSIDERATIONS

The unique vulnerabilities of infants and children demand special attention in communities that have contamination of their water, food, soil, or air. The potential for exposure and subsequent adverse health effects is often increased for younger children compared with older children or adults. At this site, the estimated risks for children were a little higher than for adults but the risks were still very low. ATSDR and DOH recognize that children are susceptible to developmental toxicity that can occur at levels much lower than those causing other types of toxicity. The levels of exposure to both naphthalene and PCP in drinking water at this site were far below doses given to animals that showed no reproductive effects. Past exposure to the maximum level of PCP detected in the now-abandoned public supply wells shows only a slight increase in cancer risk for a person assumed to be exposed from birth through 23 years of age. This exposure duration is an overestimate because the site began operation in 1964 and the wells were abandoned in 1987. In this worst-case scenario, the levels of naphthalene and PCP in the City's drinking water would not be expected to result in adverse health effects for children.


CONCLUSIONS

  1. No drinking-water wells were identified in the survey. Although the response rate was only 36%, the survey provides some reassurance that no drinking-water wells are located near the PWT site.

  2. The limited data available indicate that past exposure to the maximum concentration of PCP in the City's drinking water (4 µg/L) is characterized as a no apparent public health hazard.


  3. No public health hazard currently exists in the City's drinking-water supply because new wells were installed in 1987.

RECOMMENDATIONS/ACTION PLAN

  1. No drinking-water wells should be drilled in the contaminated area or immediately downgradient of the site. Future human exposure pathways would be of concern if wells were drilled in this area for drinking water.

  2. DOH recommends a follow-up, door-to-door survey because response to the original survey was low.

    • DOH will do a door-to-door survey

PREPARER OF REPORT

Lenford O'Garro
Washington State Department of Health
Office of Environmental Health Assessments
Site Assessment Section


DESIGNATED REVIEWER
Robert Duff, Manager
Site Assessment Section
Office of Environmental Health Assessments
Washington State Department of Health


ATSDR TECHNICAL PROJECT OFFICER
Debra Gable
Division of Health Assessment and Consultation
Agency for Toxic Substances and Disease Registry


REFERENCES

  1. Ecology and Environment. Pacific wood treating site assessment report, TDD:96-02-0024. Prepared for U.S. Environmental Protection Agency, contract no. 68-W6-0008. Seattle: Ecology and Environment, Inc.1996.

  2. Hart Crowser, Inc. RCRA facility investigation site characterization work plan, Pacific Wood Treating Corporation, Ridgefield, WA. J-5036-02. Portland, Oregon: Hart Crowser, Inc.1992.

  3. Buck, Jeremy. Preliminary assessment to determine Superfund site impacts on the Ridgefield National Wildlife Refuge, Project ID: 13420-1216-1C58. Portland, Oregon: Oregon State Office of the U.S. Fish and Wildlife Service. 2000.

  4. Ecology and Environment. Memorandum to Lew Kettle (DOH) from Dawn Hartley concerning human health concerns at Pacific Wood Treating. Seattle: Ecology and Environment, Inc. 1995.

  5. Washington State Department of Ecology. Contamination confirmed in Ridgefield [Washington] refuge. Department of Ecology news release - May 2001. Seattle: Washington State Department of Ecology. Toxics Cleanup Program.

  6. Washington Public Ports Association: Ridgefield starts steam-cleaning site. Washington Ports Members Letter August 2002. Olympia, WA: Washington Public Ports Association.

  7. Ellis, Margaret. High-tech cleanup on tap: Firm plans to use steam to extract toxic chemicals. The Columbian 2002 June 24; Sect.A:1.

  8. US Department of Health and Human Services, Agency for Toxic Substances and Disease Registry: Toxicological profile for pentachlorophenol (update) PB/2001/109106/AS. Atlanta: US Department of Health and Human Services; September 2001.

APPENDIX A: LETTER AND WELL SURVEY

February 10, 2003


Dear Resident:

The Washington State Department of Health is requesting information on drinking water wells in your area. We need this information to ensure that groundwater contaminants at the former Pacific Wood Treating site are not threatening nearby drinking water wells. While it is unlikely that these contaminants would move in your direction, we want to know what wells might be in the area. We would then determine if sampling and analysis for these contaminants is necessary to ensure that your drinking water is safe.

This information will not be used for any other purpose and will be available to the public only by formal request. Your participation in this survey is voluntary. You will not lose any services or benefits if you choose not to participate. If you do use a private well, your participation will allow us to assess the need for sampling and, if necessary, evaluate sample results.

Please take a few minutes and fill out the enclosed form and return it to us according to the instructions given on the form. We ask that you fill it out regardless of your water source so that we know you have received this request.

If you have any questions, please do not hesitate to call me toll-free at 1-877-485-7316 or (360) 236-3376. Your cooperation is appreciated.

Sincerely,


Robert Duff
Manager
Site Assessment Section

Enclosure (Survey)

Click here to view the Appendix A Survey in PDF format (PDF, 14kb)


APPENDIX B:

EXPOSURE CALCULATIONS
Water Ingestion Route of Exposure - Noncancer
Variables:
Ingested Dose (ID)
Water Concentration (Cw)
Ingestion Rate (IR)
Exposure Frequency (EF)
Exposure Duration (ED)
Body Weight (BW)
Averaging Time (AT)
ID equals Cw times IR times EF times ED divided by BW times AT
Pentachlorophenol: RfD = 0.03 mg/kg-day
Child drinking 0.9 liter of water per day
Cw = 0.004 l/day
IR = 0.9mg/l
EF = 350days
ED = 5 yrs
BW = 15 kg
AT = 1825 days
ID equals 0.004 times 0.9 times 350 times 5 divided by 15 times 1825
ID = 0.0002 mg/kg/day
Adult drinking 1.4 liter of water per day
Cw = 0.004 mg/l
IR = 1.4 l/day
EF = 350days
ED = 23 yrs
BW = 72 kg
AT = 8395 days
ID equals 0.004 times 1.4 times 350 times 23 divided by 72 times 8395
ID = 0.00007 mg/kg/day
Water Ingestion Route of Exposure - Cancer
Variables:
Ingested Dose (ID)
Water Concentration (Cw)
Ingestion Rate (IR)
Exposure Frequency (EF)
Exposure Duration (ED)
Body Weight (BW)
Averaging Time cancer (AT)
Oral Cancer Slope Factor (CSF)
ID equals Cw times IR times EF times ED times CSF divided by BW times AT
Pentachlorophenol: RfD = 0.03 mg/kg-day
Child drinking 0.9 liter of water per day
Cw = 0.004 l/day
IR = 0.9mg/l
EF = 350days
ED = 5 yrs
BW = 15 kg
AT = 27375 days
ID equals 0.004 times 0.9 times 350 times 5 times 0.12 divided by 15 times 27375
ID = 0.000002 mg/kg/day
Adult drinking 1.4 liter of water per day
Cw = 0.004 mg/l
IR = 1.4 l/day
EF = 350days
ED = 8 yrs
BW = 72 kg
AT = 27375 days
ID equals 0.004 times 1.4 times 350 times 8 times 0.12 divided by 72 times 27375
ID = 0.000001 mg/kg/day


CERTIFICATION

This Health Consultation was prepared by the Washington State Department of Health under a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR). It is in accordance with approved methodology and procedures existing at the time the health consultation was begun.

Debra Gable
Technical Project Officer,
SPS, SSAB, DHAC
ATSDR


The Division of Health Assessment and Consultation, ATSDR, has reviewed this public health consultation and concurs with the findings.

Roberta Erlwein
Section Chief,
SPS, SSAB, DHAC
ATSDR



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