Alternatives for Managing the Nation's Complex Contaminated Groundwater Sites (2013) / Chapter Skim
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5 Implications of Contamination Remaining in Place
5 Implications of Contamination Remaining in Place
Pages 161-218
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From page 161... ...
First, contamination from these sources must be contained on-site, by using either hydraulic or physical containment systems combined with institutional controls. Indeed, 65 percent of source control RODs from FY 1998–2008 included containment, and institutional controls are used at the vast majority of CERCLA source control remedial actions to enhance and ensure their effectiveness and protectiveness (EPA, 2010a)
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From page 162... ...
physical containment, (3) reduction of contaminant concentrations through natural processes (monitored natural attenuation)
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has recently developed a six-step procedure for evaluating the hydraulic containment of target capture zones, with an emphasis on comparing measured water levels and concentrations against model predictions (EPA, 2008a)
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From page 164... ...
Physical Containment Barriers are frequently used to influence groundwater flow in combined remedies that also use extraction wells and/or engineered reaction zones. From a containment standpoint, the overall remediation goal is similar to hydraulic containment: maintain control of groundwater within a target capture zone.
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From page 165... ...
. Permeable Reactive Barriers To function successfully, a permeable reactive barrier (PRB)
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From page 166... ...
technology, pursuit of a technical impracticability waiver, or the use of institutional controls. MNA systems could fail for many reasons, including temporal changes in site-specific hydrologic or geochemical conditions, the depletion of natural sources of nutrients or electron acceptors/donors, and lower-than-anticipated transformation rates.
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From page 167... ...
, institutional controls are necessary to prevent the exposure of local residents to chemicals in groundwater and soil. At groundwater sites, institutional controls play three roles.
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From page 168... ...
An easement or restrictive covenant prohibiting the extraction of groundwater for drinking water on property containing the contaminated groundwater plume is an example of this type of instrument. There are also direct governmental controls on the use of property, such as zoning laws, building codes, or state, tribal, or local groundwater use regulations.
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From page 169... ...
. The New Emphasis and Direction on Institutional Controls EPA has substantially improved its process of developing, implementing, and enforcing institutional controls.
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. Where residential properties are located over a contaminated groundwater plume and the properties are not the source of contamination, well drilling restrictions
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At Superfund-financed sites (i.e., those without viable PRPs) , EPA does not pay for monitoring or enforcing institutional controls because CERCLA Section 104(c)
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Developers may perform construction in contaminated soil or water that results in worker exposure. The failure of institutional controls may lead to property damage or personal injury lawsuits.
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From page 173... ...
contains 104 chemicals or chemical groups and 12 microbiological contaminants including pesticides, antibiotics, and other pharmaceuticals or their degradation products, disinfection by-products, industrial chemicals, and waterborne pathogens that are not currently regulated under national primary drinking water standards. Not all contaminants on the list are likely regulatory targets for drinking water limits; i.e., MCLs are expected to be developed for only a small subset of the contaminants on the CCL.
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From page 174... ...
operations. Although naphthalene is rarely found in drinking water supplies, at some MGP sites concentrations of naphthalene in the thousands of μg/L have been found (ATSDR, 2005)
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. EPA has decided to regulate perchlorate pursuant to the Safe Drinking Water Act due to its effect on thyroid function (EPA, 2011c)
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From page 176... ...
The present MCL of 5 μg/L is now associated with a 10–5 risk over a 70-year exposure, which falls within EPA's acceptable risk range of 10–6 to 10–4. The non-cancer reference dose has led to a regional screening level for TCE in drinking water of 2.6 μg/L1 (although it should be noted that the screening level is not a cleanup goal, and site-specific factors could result in a non-cancer TCE cleanup goal that exceeds 2.6 μg/L)
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verifying removal during drinking water treatment. Nanomaterials.
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in drinking water, albeit at much lower concentrations than in the rodent studies, is being considered. California and New Jersey have
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From page 179... ...
The reduction in the arsenic MCL from 50 μg/L to 10 μg/L has already resulted in a remedy reopener at the Arsenic Trioxide Site in North Dakota, as a result of the determination that the drinking water limit of 50 ppb was no longer protective of public health.3 Sampling determined that 84 percent of the well water users in the 26 townships were drinking water containing arsenic concentration at or over the arsenic MCL of 10 ppb (EPA, 2010d)
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From page 180... ...
or dissolved constituents that partition from the groundwater plume to soil gas. Vapors emitted from these contaminant sources disperse into air-filled void spaces within the soil and migrate below surface structures, leading to the intrusion of contaminant vapors into indoor air.
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. There are approximately 3,000 residences overlying dilute chlorinated solvent groundwater plumes outside the base, and about half agreed to participate in an indoor air monitoring program.
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This is partly because of significant uncertainty in understanding the vapor intrusion pathway. That is, contaminant concentrations in indoor air are variously determined by concentrations in the subsurface, the subsurface geology, environmental conditions (such as wind speed and temperature)
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Chapter 6 discusses both the current limits in our understanding of vapor intrusion as well as advances in real-time sensor technologies that will make it easier to detect indoor air contamination from subsurface sources and determine the best mitigation strategies. EPA has compiled an empirical data set for hazardous waste sites with paired groundwater, soil gas, and indoor air data on chlorinated solvents (EPA, 2012b)
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From page 184... ...
Some regulatory agencies suggest installing systems without fans, and then testing the indoor air after construction but before occupancy, at least where the threat of vapor intrusion is uncertain. If sampling shows elevated levels of VOCs indoors, fans are then installed and operated (e.g., see CalEPA, 2011)
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From page 185... ...
The purpose of this section is not to argue that litigation will occur in every case, but rather that the potential is likely to exist as long as chemicals remain in the groundwater above drinking water levels. The reader should not consider the examples and illustrations given to be a comprehensive review.
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From page 186... ...
. Potential Personal Injury and Property Damage Liability If chemicals remain in soil or groundwater in concentrations above unrestricted use levels, there is a potential that the active remedy, engineering controls, and institutional controls may fail and result in lawsuits alleging personal injury and/or property damage.
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and therefore are not relevant to contaminated groundwater sites. NRD settlements for mining sites, large oil spills, and contaminated sediment tend to be higher than other NRD settlements.
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A class action lawsuit was brought by 19 residents of Woburn, Massachusetts against two industrial companies for contaminating groundwater with chlorinated compounds (including TCE) alleging that exposure to groundwa ter caused injury to the local residents because the city used the groundwater as a source of drinking water.
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approved, a monitored natural attenuation remedy with a 20- to 100-year time horizon to at tain the benzene drinking water standard (Tanner, 2009, summarizing the facts in Sunburst Sch.
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From page 190... ...
and paid TNC $175,000 for the purpose of preserving and managing such land. 4. he final restoration plan is to construct T two drinking water treatment plants using reverse-osmosis technology, provide a minimum of 8,235 acre feet per year of drinking water, contain the spread of contamination in the deep aquifer and remediate it within the "affected area," and integrate the CERCLA remedial response with the NRD Consent Decree provisions.
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From page 191... ...
. Box 5-5 discusses two of these cases, along with two others from Southern California, that illustrate the range of situations in which drinking water utilities find themselves with respect to a contaminated groundwater source.
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In the Santa Monica case, 45 companies were tentatively identified as PRPs The systems used by water utilities to treat anthropogenic chemicals in groundwater are required to meet all applicable drinking water standards mandated by the SDWA as well as any additional requirements from the primacy agency (i.e., the state or local authority)
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Finally, in the San Fernando Valley Basin where the Los Angeles Department of Public Works is responsible for delivering water to 4 million people, numer ous potential sources of groundwater contamination and the emergence of new chemicals of concern such as hexavalent chromium and 1,4-dioxane have been identified. Although only approximately 11 percent of the drinking water is sup plied from groundwater, the majority of this amount is produced from the San Fernando Valley Ground Water Basin.
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, which required modifications to the existing groundwater treatment systems and caused an increase in operating costs. In addition to future changes in the drinking water standards for individual chemicals, EPA is also considering alternative regulatory strategies that may affect both remedial objectives as well as well-head treatment standards.
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declared that the 97-005 policy is no longer considered obligatory, and is considered as guidance only, since the policy was not subjected to legislative review and approval. Nonetheless, the risk analysis components of the 97-005 process provide the state with some assurance that the well-head treatment system will consistently remove all chemicals of concern to appropriate drinking water standards or below, and that the approved treatment system is capable of dealing with chemicals likely to be present in the aquifer, in addition to the chemicals designated for removal in the permit.
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From page 196... ...
Wellhead Treatment The objective of wellhead treatment is to remove natural and anthropogenic contaminants to levels consistent with standards established for the intended use. If the intended use is human consumption, the water must be rendered safe as defined by the SDWA (i.e., meet all federal MCLs or other state drinking water standards)
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From page 197... ...
Anion exchange, advanced oxidation, and biological processes are becoming more common as the treatment objectives for groundwater are being expanded to include multiple contaminants as well as due to the reduction in drinking water standards for treated water. TABLE 5-2 List of Commonly Used Groundwater Treatment Technologies Relative Technology Technology Technology Cost Applicability Limitations Packed Tower Low Moderately to • Tower height usually Aeration highly volatile limited to 20 or 30 ft compounds • Air-to-water ratio characterized with usually limited to high Henry's Law 150:1 Constant (e.g., • Scaling control (acid TCE and PCE)
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bromate formation • Excess peroxide must be quenched Advanced Oxidation High Smaller organic • Higher dosages with Ultra Violet molecules (e.g., required compared to Light (UV-AOP) 1,4-dioxane)
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From page 199... ...
In some instances, water utilities will attempt to the remove contaminants that are not currently regulated, but where state standards or compliance levels have been established or are likely in the future. For example, at a groundwater treatment facility located near the Tucson Airport where TCE-contaminated groundwater has been treated for several years using packed tower aeration, operators are installing a UV-AOP treatment process for removal of 1,4-dioxane, which has been recently detected at low levels.
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. In this case, wellhead treatment of a groundwater plume used as a primary water supply was deemed necessary because full containment of the groundwater plume was thought to be technically infeasible and not cost effective.
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Figure 5-1 provides a stylized example of costs associated with a contaminated groundwater site. "Services under baseline" represents water quality in an aquifer absent of contamination.
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Potentially Responsible Party Costs The costs faced by a potentially responsible party are the costs of remedial actions and litigation expenses (discussed in a previous section)
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reported that 44 percent of Superfund facilities have more than one potentially responsible party and 52 percent of potentially responsible parties have more than one site where they have responsibility. These conditions make it difficult to obtain sitespecific cost data for individual firms from public records and it is also difficult to aggregate cost data across firms for specific sites.
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From page 204... ...
As with the costs to potentially responsible parties, the costs of residual contamination to affected parties described above are challenging to address. The goal of any damage claim is to measure these costs as accurately as possible and to seek compensation as quickly as possible.
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From page 205... ...
As a result, mergers and acquisitions may trigger action to obtain regulatory certainty concerning cleanup efforts, the adoption of indemnification allocating future liability among the purchaser and seller, renegotiation of the sales price, or set asides of funds for cleanup or other activities. Furthermore, in 2011 six federal financial institution regulatory agencies proposed credit risk retention rules for commercial real estate property where environmental hazards, such as groundwater contamination, may potentially jeopardize the value of commercial real estate as well as the borrower's ability to repay a loan (OCC et al., 2011)
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From page 206... ...
, establish field experimental stations at operating waste sites to assess the long-term performance of physical containment systems. Implementing institutional controls at complex sites is likely to be difficult because it requires long-term monitoring of site conditions and potential exposures and maintenance of land use restrictions that may be in tension with the development preferences of local authorities.
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From page 207... ...
of institutional controls. At a minimum, those who live, work, study, play, or otherwise occupy residences, commercial buildings, or industrial facilities near hazardous waste sites should be notified of institutional controls, including the specific reasons for them.
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From page 208... ...
Furthermore, such systems reduce exposure to naturally occurring radon. As a precautionary measure, vapor mitigation could be built into all new construction on or near known VOC groundwater plumes; this could be imposed proactively as part of local or state building codes or other requirements or imposed as institutional controls at regulated sites.
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From page 209... ...
2008. Cancer mortality in a Chinese population exposed to hexavalent chromium in drinking water.
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From page 210... ...
1999. Environmental Law Institute, Protecting Public Health of Superfund Sites: Can Institutional Controls Meet the Challenge?
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2010b. Institutional Controls: A Guide to Planning, Implementing, Maintaining, and Enforcing Institutional Controls at Contaminated Sites.
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2011j. Basic Questions and Answers for the Drinking Water Strategy Contaminant Groups Effort.
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1995. Measuring the impact of the discovery and cleaning of identified hazardous waste sites on house values.
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2012. EPA Requires Cr6 Monitoring in New List of Drinking Water Contami nants.
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2010. Ten year performance evaluation of a field-scale zero-va lent iron permeable reactive barrier installed to remediate trichloroethene contaminated groundwater.
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2002. Geochemical Factors Af fecting Performance and Longevity of Permeable Reactive Barriers.
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2008. State Environmental Easement Statutes as ARARs: A New Option for Enforc ing Institutional Controls at Superfund Sites.
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2003. Capstone Report on the Application, Monitoring, and Per formance of Permeable Reactive Barriers for Groundwater Remediation: Volume 1 -- Performance Evaluation at Two Sites.
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