Groundwater Monitoring: A Regulatory Overview

September 1, 1993

6 Min Read
Groundwater Monitoring: A Regulatory Overview

Chris Voell

Groundwater monitoring is an issue that strikes fear into the hearts of many landfill owners and operators. It is an expensive, highly technical area that is constantly evolving to meet new regulations and technological standards.

The Subtitle D groundwater monitoring requirements apply to all landfill units, except where the owner/operator can de-monstrate that no potential for contamination of the uppermost aquifer exists during operation and post closure.

As with many parts of Subtitle D, the compliance schedule for groundwater requirements de-pends on whether the site is in an approved or un-approved state. (See Table I for a compliance schedule). New landfill units must be in compliance before waste is accepted.

The groundwater monitoring requirements consist of four areas: groundwater monitoring systems, detection monitoring, assessment monitoring and corrective action. The hope is that properly sited, designed and operated landfills will not have to progress beyond the detection monitoring stage. Going beyond that step involves a lot of effort and money.

The regulations state that a system must be installed with an appropriate number of wells to collect groundwater samples from the up-permost aquifer. The system must assess both background (upgradient) water quality and the quality of water that has passed under and around the landfill (downgradient).

Detection Monitoring Once a groundwater monitoring system is in place, the next step is detection monitoring, which checks for any releases from the landfill. The Environmental Protection A-gency (EPA) will require semi-annual testing of groundwater quality through the active life of the site and through the post-closure period. There are a total of 62 parameters that must be assessed in each sampling: 15 heavy metals and 47 vol-atile organics (see Table II on page 34). Approved states can establish alternate parameters to the heavy metal list as long as they accurately assess inorganic releases. The cost for detection monitoring (Phase I) is about $400 per sample.

All samples must be analyzed to determine if any background levels have increased significantly for one or more of the parameters being tested. If a statistically significant increase occurs, the landfill owner/ operator must establish an assessment monitoring program to demonstrate that the landfill is not the source of contamination, or that the increase is due to an error in the groundwater sampling program.

The owner/operator must sample and analyze groundwater for 213 organic and inorganic constituents. After the initial sampling, owners/ operators must perform detection monitoring twice a year, and sample for those parameters that were identified in the first assessment monitoring program. All 213 monitoring parameters must be sampled and analyzed annually.

The landfill owner/ operator is required to establish a groundwater monitoring protection standard for any constituents found in the assessment monitoring program. States with approved programs are permitted to establish a number of alternative standards in the assessment monitoring program. Results of the monitoring must be statistically analyzed using appropriate procedures.

Based on the statistical analysis, the owner/operator:

* May return to detection monitoring if the landfill is not causing the contamination, or if the concentration of all constituents is at or below background values;

* Must continue assessment monitoring if the constituent concentrations are below the groundwater protection standard; and

* Must initiate a corrective action program if one or more constituents are detected at statistically significant levels above the groundwater protection standard.

A corrective action program re-quires that landfill owners/operators characterize the nature and extent of any groundwater contamination, as-sess positive corrective action measures, select an appropriate corrective action and implement a remedy.

Characterizing the nature and extent of the release means instal-ling additional wells and notifying all persons who may be affected.

The owner/operator must assess corrective measures within 90 days, continue groundwater monitoring, analyze the effectiveness of potential corrective measures and discuss the results at a public meeting.

The owner/operator should select an appropriate remedy and develop a schedule for initiating and completing the remedial actions. Then he or she should establish corrective action plans and take any interim measures to protect human health and the environment. The owner/ operator should determine if the remedy is working and manage all byproducts of the corrective action work according to regulations.

While this overview of Subtitle D rules has been general, the rule is complicated and should be studied before making groundwater monitoring decisions. The EPA's Draft Tech-nical Manual for Solid Waste Dis-posal Criteria - 40 CFR 258 is a good resource for both the EPA regulations and their intent.

When Subtitle D was originally proposed, there was some leniency afforded to very small landfills. The affected sites were those that re-ceived very low tonnages, were in arid regions and showed no evidence of groundwater contamination. However, a recent case has removed this exemption so that all landfills must have groundwater monitoring in place. Because of the recent court ruling, the EPA plans to delete the current exemption from the groundwater monitoring requirements and to extend the effective date of the federal regulations to October 9, 1995, for those small landfills that had qualified for the exemption. This will give small communities time to make practical, economic decisions about managing their solid waste.

Groundwater monitoring and data interpretation is highly technical, with a multitude of statistical analyses and interpretation techniques. Groundwater monitoring cannot be done by unqualified individuals, because too much rides on the re-sults of the sampling program. Many of the parameters being sampled can be affected by seemingly small errors in technique.

While the costs of setting up a system and conducting a sampling program are high, they could be dwarf-ed by an assessment and corrective action that was triggered by faulty monitoring and/or sampling.

This does not mean that landfill owners/operators always must contract with outside firms for their sampling and monitoring. The goal is competency, training and consistency, regardless of who is doing the sampling. There are certainly many competent, trained individuals at various levels of government, for ex-ample in health or water quality de-partments, who can develop and provide sampling services. However, remember that the department doing the testing may be the local regulatory agency responsible for overseeing the landfill. In this case, it is probably prudent to have an outside contractor provide sampling services so that the data can be compared to that of the regulatory agency.

The groundwater monitoring re-quirements that today's landfill owner/operator has to follow are stringent, complicated and costly. False positive test results (signs of contamination when none exists) and false negative results (no signs of contamination when it does exist) from faulty sampling programs can be devastating to the landfill owner/ operator and the local environment.

Although the groundwater monitoring requirements do not become effective immediately, do not be lulled into a false sense of security. Landfill owners/operators should start planning now to have the most qualified firm possible for monitoring system design, well installation, sampling, monitoring and data analysis. This will take some time and effort, but it will be time well spent in avoiding headaches down the road.

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