Private Well Testing in Oregon from Real Estate Transactions: An Innovative Approach Toward a State-Based Surveillance System

In 2009, the U.S. Department of Health and Human Services released “The Surgeon General's Call to Action to Promote Healthy Homes,” which highlights the link between well-water quality and health, and recommends annual testing of private wells for bacteria and chemical contamination.¹ Also in 2009, the American Academy of Pediatrics (AAP) released new guidance for private well-water testing to protect children from illnesses associated with exposure to drinking-water contaminants.² Chief among the new guidelines was the recommendation that water be tested at least annually for nitrate and coliform bacteria. The AAP also recommended that state governments require well testing when a dwelling is sold.

California, Colorado, Georgia, Idaho, Indiana, Oregon, Pennsylvania, Washington, and Wisconsin have been identified as having the highest nitrate concentrations in shallow groundwater in the U.S.³ Of these states, only Oregon has enacted legislation that requires private well testing (PWT) at the point of a real estate transaction (RET). New Jersey, in 2001, and Rhode Island, in 2008, also passed PWT-RET legislation. These laws represent an innovative policy option for state governments to assess the quality of private well water. The benefits of linking private well surveillance to the sale of a property include: (1) potential buyers are informed of water quality and can negotiate any treatment costs with the seller, (2) the state can collect and analyze sampling data to characterize groundwater quality, and (3) state and local public health agencies can identify individuals or communities exposed to high levels of drinking-water contaminants and provide information on health-protective measures.⁴

Currently, there is no federal law or program to monitor the quality of private wells, as there is for public water systems under the Safe Drinking Water Act (SDWA). Under the SDWA, the U.S. Environmental Protection Agency sets maximum contaminant levels (MCLs) for drinking water supplied through public water systems and oversees the states, localities, and water suppliers that implement these standards.⁵ Yet, approximately 43.5 million people, or 15% of the U.S. population, rely on private wells for household needs, and the quality of this water cannot be guaranteed.⁶ Oregon has approximately 350,000 private wells, and an estimated 16% of the state population consumes drinking water from private wells.⁷

Private wells are generally supplied by groundwater aquifers, which are susceptible to contamination from both point and nonpoint sources associated with human activities on land. Sources frequently cited as threats to groundwater include leaking underground storage tanks, septic systems, landfills, industrial facilities, and agricultural activities, such as widespread field application of fertilizers and manure storage or spreading.⁸

Nitrate is associated with these agricultural activities, as are septic systems, and is the most widespread contaminant in groundwater aquifers.^9,10 The normal background concentration of nitrate in groundwater is estimated to be 2 milligrams per liter (mg/L).¹¹ The MCL for nitrate (10 mg/L) was established due to concerns that ingestion of nitrate in drinking water by infants may lead to methemoglobinemia, or “blue baby” syndrome, a condition that can cause cyanosis and, in advanced stages, asphyxia.^12,13 Recent studies also have linked nitrate in drinking water to thyroid disorders,^14,15 insulin-dependent diabetes,^16,17 reproductive anomalies,^18,19 acute respiratory infections,²⁰ non-Hodgkins lymphoma,²¹ colon cancer,^22,23 and cancers of the bladder and ovary.²⁴

Other common contaminants in groundwater that pose a significant problem for private well owners are microorganisms, including bacteria, viruses, fungi, and parasites.²⁵ An estimated 51% of waterborne disease outbreaks in the U.S. during 1999–2000 were caused by microorganisms. Of these, 64% were associated with private wells.²⁶ Gastrointestinal illness, in particular, has been found to be associated with Escherichia coli (E. coli) contamination of private well water.²⁷

The most common method of detecting microorganisms that may be an indicator of fecal contamination from animals or humans is by testing total coliforms.²⁵ The MCL in public drinking-water systems for total coliforms is zero, indicating that a water source used for drinking should have no detectable coliform bacteria. Total coliforms and nitrate contamination of drinking water can stem from a common source, and some researchers argue that the health effects associated with drinking-water nitrates can be attributed, instead, to co-occurring microorganisms.^28,29

A U.S. Geological Survey (USGS) study of private wells in 48 states found that more than 20% of sampled wells contained one or more contaminants at a concentration greater than health-based standards.³⁰ More than 4% of sampled wells had nitrate concentrations exceeding the MCL for nitrate, and 34% tested positive for total coliform bacteria. Nearly 25% of sampled wells exceeded the MCL that were located in predominantly agricultural areas, defined as greater than 50% agricultural land within a 500-meter radius around the well. The USGS study warned that many states are facing the challenge of ensuring the safety of drinking water for residents using private wells.

Nitrate contamination of groundwater is a problem in Oregon due to long-term contributions from agricultural fertilizers, animal feedlot operations, leaking septic systems, and aboveground application of wastewater.⁶ Recognizing the need to preserve groundwater quality in the state, Oregon passed two pieces of legislation in 1989 enabling statewide groundwater monitoring. The Groundwater Protection Act requires the Oregon Department of Environmental Quality (DEQ) to declare a Groundwater Management Area (GWMA) if area-wide groundwater contamination exceeds trigger levels.³¹ For nitrate, the trigger level is 70% of the MCL, or 7 mg/L. Currently, there are three GWMAs in Oregon, together accounting for 966,000 acres or about 2% of the total area of the state. The Oregon DEQ declared all three GWMAs due to widespread nitrate contamination.⁷ Once a GWMA has been designated, a local committee is convened to work with state agencies to develop and implement a voluntary action plan to reduce groundwater contamination. The action plans often include educational outreach efforts to residents living inside the GWMA who may have private wells or on-site septic systems.^32–34

The second piece of legislation, the Domestic Well Testing Act, requires that any seller of a property with a well that supplies groundwater for domestic purposes must have the well water tested for nitrate and total coliform bacteria by a state-certified laboratory upon accepting a purchase offer.³⁵ Results must be sent to the state health agency, the Department of Human Services (DHS), and stored in the RET database. The following information is submitted along with the test results: Public Land Survey System description of the property; names and addresses of the owner, buyer, and individual who collected the sample; sampling point; well identification number; and well depth. In 2009, this law was amended to include arsenic as a test parameter and to require that buyers receive notification of the test results.³⁶

The purpose of this legislation was not to protect public health per se, but to “establish a program to provide water quality monitoring.”³⁷ Currently, no follow-up actions occur when test results reveal high nitrate levels or positive coliform detections. Furthermore, the law is not enforceable. There is no penalty for noncompliance, and the sale of the property can be finalized without completion of testing. Due to a lack of resources, data in the RET database are not routinely analyzed. This database, however, is a valuable repository of contaminant information, and routine analysis may help direct public health measures by state agencies to those individuals living in areas where well contamination is shown to be prevalent.

The objectives of this study were to analyze the RET data to develop policy recommendations for PWT-RET legislation. These recommendations were based on the results of the analysis and a comparison with similar programs in other states. The specific goals of the analysis were to (1) assess compliance with the law—that is, the extent to which the required testing and reporting actually occurred; (2) determine the prevalence of MCL or action-level exceedances; (3) examine the spatial distribution of these exceedances; and (4) compare the spatial distribution of exceedances with the location of GWMAs and centers of population growth.

METHODS

Data collection

The primary dataset used in this analysis consisted of nitrate and total coliform bacteria testing results from individual private well-water samples submitted to the Oregon DHS for the years 1989–2008.³⁸ All database entries had been copied manually from the submitted paper forms containing the property address and test results. The addresses were geocoded, and latitudes and longitudes were added. Prior to analysis, duplicate entries per sampling event, attributed to data-entry error, were removed. Some homes had been sold more than once during the time period captured in the data, so there was more than one measurement available for one location. In these cases, the median value was selected to represent the nitrate concentrations in the well at the address because this measure of central tendency is least affected by extremes.

To examine reporting trends over time, we counted the number of reports submitted to the RET database by year. Our goal was to assess the completeness of reporting by comparing the number of test reports with the total number of homes having a private well that were sold. Next, we determined the number and percentage of MCL violations and compared them with prevalence estimates from other surveys and states.

For analytical purposes, the nitrate data were categorized based on concentration levels. Category 1 concentrations were 0.0–6.9 mg/L (less than the GWMA trigger level of 7.0 mg/L). Category 2 included concentrations of 7.0–9.9 mg/L, and Category 3 included concentrations of ≥10.0 mg/L (the MCL).

Spatial and statistical analyses

Statewide maps of Category 2 and Category 3 nitrate concentrations as well as positive coliform detections were produced (using ArcGIS® 9.3³⁹) to allow for a visual assessment of the locations with elevated contaminant levels. The visual examination was followed by statistical analysis of the distribution of nitrate levels across Oregon. We computed the Getis-Ord General G statistic to determine whether nitrate levels were clustered in specific locations and if the clustering occurred for high or low concentrations, while controlling for the density of testing in different regions.⁴⁰

Finally, we determined the Oregon counties that had the highest number of wells with elevated nitrate levels. We compared the location of these counties with that of GWMAs in Oregon to examine whether remediation efforts were already underway in affected areas. In addition, we used census data⁴¹ and population forecasts⁴² to assess the potential risk for exposures to high nitrate levels in these counties.

RESULTS

A total of 20,173 distinct sampling events were available in the RET database at the time of analysis. Figure 1 shows the total number of sampling events reported each year from 1989 to 2008 and illustrates the large fluctuations in the number of reports submitted per year. The annual number of reports submitted has declined since 1996. After removing duplicate entries per address and retaining the median nitrate value for analysis, 18,688 addresses were represented in the spatial analysis.

Figure 1.

Total number of real estate transaction entries per year, 1989–2008, Oregon

Information about the number of RETs in Oregon that involved properties with private wells was unavailable. Therefore, we could not determine the percentage of RETs that actually complied with the law by reporting the PWT results to the Oregon DHS.

Nitrate concentrations

A total of 409 records (2.2%) contained Category 2 nitrate concentrations, while Category 3 nitrate concentrations were found in 322 records (1.7%). The percentage of Category 3 concentrations (corresponding to MCL violations) of 1.7% equals the percent of MCL violations reported as a result of a preliminary 2004 analysis by the Oregon DEQ.⁷ New Jersey found similar rates, with 2.7% of wells showing nitrate MCL exceedances.⁴ Surveys in Wisconsin⁴³ and Iowa⁴⁴ resulted in significantly higher percentages, with 14% and 18% exceedances, respectively.

Total coliform results

A total of 2,415 records (12%) in the RET database contained positive detections of total coliform bacteria. This rate was much higher than the 2.2% of wells testing positive for fecal coliform or E. coli presented in the New Jersey report.⁴ At the same time, it was substantially lower than the 62% of sampled wells with positive detections of total coliforms found in a study of 78 private wells in south-central and southeastern Pennsylvania. This latter finding probably reflects a sampling bias toward wells that were in “close proximity to agricultural land-use areas.”⁴⁵

Figure 2 presents the locations of private wells with Category 2 and 3 nitrate concentrations and wells with positive detections of total coliform bacteria. It shows that contaminated well water was found across most of the state, although most of the wells with high nitrate levels were in more rural counties and in rather circumscribed areas. In line with this observation, the Getis-Ord spatial analysis of nitrate levels revealed highly significant clustering of elevated nitrate concentrations (z=10.86). Thus, a well with a high level of nitrate was likely to have other wells with elevated nitrate concentrations in its vicinity.

Figure 2.

Oregon private wells with Category 2 (top) and Category 3 (middle) nitrate levels and positive detections of coliform (bottom), 1989–2008

mg/L = milligrams per liter

The Oregon counties with the highest number of private wells with elevated nitrate concentrations were Crook, Deschutes, Jackson, Josephine, Lane, Linn, Malheur, Marion, and Umatilla (Figure 3). Of all wells represented in the RET database, 74% were located in one of these counties. Oregon's three designated GWMAs encompass only portions of four of these counties—Lane, Linn, Malheur, and Umatilla—although each GWMA does cover substantial portions of the clusters located in these counties. As shown in Figure 2, other clusters of contaminated wells are located outside of any GWMA, and these wells are not receiving the benefits of state efforts associated with the GWMA designation to decrease contamination in groundwater.

Figure 3.

Location of wells with Category 2 and 3 nitrate concentrations in comparison with locations of Oregon's three Groundwater Management Areas^a

^aOregon's three Groundwater Management Areas are shaded in dark gray, and the counties with the largest number of domestic wells with Category 2 and 3 nitrate concentrations are shaded in light gray.

Several of the counties with nitrate contamination clusters experienced rapid population growth in 2007 (Table). Crook, Deschutes, Jackson, and Linn counties, in particular, experienced above average population growth compared with the overall state growth rate of 9.5% from 2000 to 2007.⁴¹ This population growth is expected to continue, with much of the additional growth likely to occur in counties containing many wells with elevated nitrate concentrations.⁴²

Table.

Population growth estimates and forecasts for Oregon counties with large numbers of wells with elevated levels of nitrates

DISCUSSION

The analysis revealed that the number of testing records in the PWT-RET database varied widely from year to year, and, unlike real estate sales, declined over time. Although we could not directly assess the percentage of properties with private wells that were actually tested, these results suggest that voluntary compliance with the Oregon PWT-RET law is limited and not uniformly implemented. Even though the data were limited, we noticed a pattern in clustering indicating that wells with a high level of nitrate were likely to have other wells with elevated nitrate concentrations in close proximity. This finding suggests that a single well testing high for nitrates is not an isolated anomaly, but instead is a valuable indicator of more widespread contamination, underscoring the need for other wells in the area to be tested. It is also important to note that although each well sample represents a single point in time, nitrate levels in groundwater can remain stable for decades.⁴⁶ Therefore, a single exceedance likely represents persistent contamination and, therefore, a persistent public health concern.

A comparison of the locations of contaminated wells and GWMAs showed that not all clusters of wells with elevated nitrate levels were located within a GWMA. Clusters outside of GWMAs are less likely to be subject to contamination mitigation efforts, including education outreach to private well owners. Populations in these areas may, therefore, be at particularly high risk of consuming contaminated well water. Given the population increase in Oregon generally, and in the counties with the highest numbers of contaminated wells in particular, it is likely that the number of people exposed to well water with elevated nitrate levels will increase over time. This is a particular concern for families with infants, given that the major human health risk associated with exposure to nitrate is infant methemoglobinemia. Of the nine counties with the highest number of contaminated wells, four of them (Linn, Malheur, Marion, and Umatilla) have a greater than average number of children younger than 5 years of age when compared with the rest of the state. Furthermore, three counties (Malheur, Marion, and Umatilla) exceed the state average for homes where English is not the primary language, and seven counties (Jackson, Josephine, Lane, Linn, Malheur, Marion, and Umatilla) exceed the state average for people living below the poverty line.⁴¹ These factors may indicate substantial barriers to educating well owners on the need for testing and treatment, as some owners may have limited English proficiency and may also lack the resources to pay for long-term treatment technologies. The existence of these susceptible populations requires comprehensive monitoring and targeted information campaigns to mitigate their exposure to contaminated water. Strengthening the existing PWT-RET legislation to improve the quality of data received by the state will contribute to both of these efforts.

To evaluate the relationship between the provisions of the Oregon PWT-RET law and data quality, we reviewed similar programs in other states. Only two states, New Jersey and Rhode Island, have PWT-RET laws that closely resemble those in Oregon. Because Rhode Island's program was initiated in 2008, we were unable to draw comparisons to this program. New Jersey's Private Well Testing Act (PWTA) and the associated program, which were implemented in 2001–2002, provided a rich store of information that was of considerable value in assessing the effectiveness of the Oregon law.

Comparison of New Jersey and Oregon laws

Testing contingencies and communication of results.

During the first four and a half years of the New Jersey program, 51,028 test results were submitted. These represented 13% of the estimated 400,000 private wells in New Jersey.⁴ By comparison, in the 20 years since enactment of the Oregon law, the total number of records submitted to the Oregon RET program represents only about 5% of the estimated 350,000 private wells in Oregon.⁷ This difference is likely the result of compliance problems with the Oregon PWT-RET law.

The New Jersey law makes the sale of a property contingent upon completion of well testing and the submission of written confirmation that both the buyer and seller have received the results. New Jersey requires the laboratory performing the analysis to submit test results directly to the state as well as to the financially responsible party. Results are submitted on a standardized form and sent electronically to the state database.⁴⁷

In Oregon, the sale of the property is not contingent upon well testing or submission of results to the state. The seller is assigned the responsibility for obtaining the test and submitting results to Oregon DHS. Forms are not standardized and submission is in paper format.³⁷ A 2009 amendment made it mandatory for the seller to provide the buyer with a copy of the test results. However, there are no consequences for failing to do so.³⁶

Well testing on rental properties

The New Jersey law also requires that property owners of rental properties with private wells have the well tested at least once every five years.⁴⁷ As with tests arising from RETs, laboratories must submit results to the state electronically and provide copies of the results to both parties—in this case, the owner and the renter. This provision increases data completeness and protects tenants whose water supply is provided by a private well by ensuring that they are aware of the quality of their water. In Oregon, there are no requirements to test private wells on rental property except when such a property is sold.

Confidentiality of test results

In New Jersey, test results are confidential. Information can only be released when aggregated by municipality, county, region, or state.⁴⁷ This provision addresses concerns expressed by realtor associations and property owners about the impact on sales and property values of homes located adjacent to properties with contaminated wells. When a well-water test result indicates that a contaminant exceeds the drinking-water standard, the state database automatically alerts the local health jurisdiction. While keeping the exact location of the well at issue confidential, the local jurisdiction is responsible for notifying property owners in the vicinity, when warranted.⁴⁵

The Oregon law makes no provisions for confidentiality of test results. Although not readily available to an individual other than one requesting the test, there are no legal grounds for denying interested parties access to the results.

Outreach and educational activities.

The New Jersey law requires that the state establish a public information and education program to inform the public and professional stakeholders about provisions of the PWTA, health effects of consuming water from a contaminated private well, treatment techniques, and potential funding available for water treatment.⁴⁷ Additional local outreach efforts are designed by each health jurisdiction in response to their assessment of local needs and available resources.

The Oregon PWT-RET law does not require the state to undertake any outreach or educational activities. Even if the tested water fails to meet drinking-water standards, the laboratory is not required to notify the state or the local health jurisdiction about the exceedance. Oregon currently does not have a public health program for private wells, but information on relevant health risks and options for well-water treatment are provided on the state agency's website (http://www.oregon.gov/DHS/ph/dwp/dwt.shtml).

Analytes required to be tested

Another key difference between Oregon's PWT-RET law and the law in New Jersey is the number of analytes tested. In New Jersey, testing is required for total coliform, 26 volatile organic compounds, nitrates, lead, arsenic, mercury, alpha particle radioactivity, pH, iron, and manganese.⁴⁷ While an expanded analyte list increases the cost to the party responsible for testing, the resulting information contributes to a more comprehensive characterization of water quality and greater health protection for individuals and communities.

Oregon's PWT-RET law only requires testing for total coliform bacteria, nitrate, and, with a 2009 amendment, arsenic.³⁶ The recent amendment also allows Oregon DHS to adopt rules requiring testing for other contaminants in specific areas that are of public health concern due to local geology or input from industry or agriculture.

CONCLUSIONS

The following recommendations, although specifically addressing shortcomings in the existing Oregon PWT-RET law, may also be helpful to other states that are considering implementing a private well-water testing law based on RETs.

• Sale of real estate with a well that is used for drinking water should be contingent on the completion of testing and notification of all pertinent parties.

• Knowledge of the PWT-RET law, health risks, and treatment methods relating to nitrate in well water should be included in the licensing of real estate agents.

• Test results should be sent directly from the laboratory, via electronic means, to the state agency overseeing implementation of the law and by mail to the buyer and seller of the property.

• The scope of the law should be expanded to include periodic testing of wells on rental properties, with result reporting requirements analogous to those for real estate sales.

• Confidentiality of test results should be protected by provisions in the law that allow public health departments to release only aggregated information.

• A notification process should be developed that protects confidentiality while allowing local health jurisdictions to inform property owners of a well in their vicinity that has contaminants exceeding drinking-water standards.

• Information regarding contaminant levels, health effects, and water-treatment options should be sent to individuals receiving test results.

• Contaminants that are of concern in various areas of the state should be catalogued for Oregon DHS use in flexibly adjusting testing requirements to meet local public health needs.

The Oregon PWT-RET law represents an innovative policy for ensuring the quality of private well water for state residents. With the dramatic reduction in state government budgets, public health agencies have to do more with less. A PWT-RET law represents a modest cost to the state to implement and maintain a private well-water monitoring program, yet the data that result from the law are crucial in identifying areas in the state where individuals and communities are being exposed to potentially harmful drinking-water contaminants, such as nitrate and coliform bacteria. If compliance can be strengthened through modifications in the existing law, the resulting data, on an individual level, will give prospective home buyers information they need to keep their families healthy. On a population level, the data will enable state agencies to target public health investigations and education outreach to especially vulnerable communities, such as families with newborns, limited English proficiency, or incomes below the poverty line.