Petroleum Hydrocarbon Contaminated – 1992
Artigo publicado e apresentado no Congresso ABES – 1992 – Este artigo faz uma revisão da investigação e remediação dos regulamentos e processos em casos de contaminação do solo por derramamento de Petróleo.
Autores: Michel Epelbaum e Jair Rosa Claudio
A REVIEW OF INVESTIGATION AND REMEDIATION REGULATIONS AND PROCESSES
This report covers an investigation and remediation review of contaminated sites. Mainly speaking, petroleum hydrocarbon contaminated sites. First, it makes a gathering of international legislative framework and structure of contaminated soil control, using the Netherlands, Germany, the USA and Brazil as references. It discusses some topics on investigation methodologies: (i) geological and hydrogeological assessment; (ii) pollutant and source information review; (iii) definition and implementation of an “in situ” investigation· plan; (iv) selection of health and environmental criteria and comparison with measured concentrations; (v) corrective action plan. The article discusses alternatives of site remediation, which include groundwater remediation techniques (“in situ” treatment, isolation, extraction and surface treatment) and soil remediation techniques (“in situ” treatment, excavation and surface treatment). Finally, it points out some trends of sites remediation in Brazil and abroad.
Groundwater contamination assessment; groundwater remediation techniques; petroleum hydrocarbon contamination; soil contamination assessment; soil contamination legislation; soil remediation techniques.
After the accident that happened in Guadalajara, Mexico, when fuel leaked into the sewerage system and caused a great explosion, the concern about leakage and soil contamination with petroleum hydrocarbons remarkably increased. Considered a recent subject in environmental control, the investigation and remediation of petroleum hydrocarbon contaminated soils in gasoline stations has had great advancement in Brazil, concerning both the development of control methodologies by environmental agencies and studies carried out by private organizations. An evidence to this fact is that São Paulo has housed two technical meetings on safety in gasoline stations. In practice, however, soil investigation and remediation techniques and methodologies are not yet widely spread.
Considering the subject of extreme importance, this paper will present a review on the regulations and criteria adopted in the Netherlands, Germany, the USA and Brazil. Also discussed is a methodology to address the problem.
CRITERIA AND STANDARDS
The special characteristics of soil use in the Netherlands allowed soil clean-up techniques there to achieve the best standards in the world. Over 7,500 contaminated areas were identified, covering some 20% of the country’s area (De Bruijn, 1988). This fact justifies the concern to identify, characterize and remediate such areas by setting up legal and financial mechanisms to clean and protect the country’s soil.
Two principles govern soil protection:
Multifunctional: the present use of the soil must not affect any possibility of potential uses in the future;
Polluter-payer: the organization or individual that generated the pollution is liable to pay for thecosts of removing such pollution, unless financially unable to do so.
Among the legal mechanisms to meet soil protection policies, interim quality standards have been established. Such standards do not derive from ecotoxicological methods but from other quality requirements, such as drinking water, food standards and others.
They are interim because they, have been setup as a first step of an interactive approach to establish standards fully based on cause-effect relations (Vegter, 1988).
Quality standards include three concentration levels for each element/substance:
A – values below which the soil is considered not contaminated and above which a preliminary investigation is required in view of the uncertain pollution and potential risk;
B – values above which a more detailed investigation is required, regarding the contamination extension and the risks involved;
C – values above which removal or clean-up is usually required to bring such values back to A levels. (Vegter, 1988)
The values related to hydrocarbon soil contamination are mentioned in Table 1.
Contaminated soil investigation and remediation in Germany is also very advanced. In addition to high industrialization levels in this century, that country also suffered much bombing during the two World Wars, on which occasions the soil was certainly polluted in several ways. As an aggravating factor, we must remember that most of the country’s water supply comes from underground sources.
This situation justifies the German behavior in relation to soil contamination as one of the strictest countries in this matter.
The soil protection policy in Germany is ruled by the principle of preventing environment and human health risk caused by soil and groundwater contamination.
Therefore, a soil investigation and remediation schedule is established in soil contamination episodes, where decisions are based on the contamination risk assessments. In addition, clean-up costs are always taken into consideration so that they are acceptable in relation to the benefits obtained.
So as to evaluate the need for soil and groundwater sanitation measures, German officials adopt the “Dutch List” as a reference, Tables 1A and 1B, associated to the investigation guidelines for classes 1 and 3 landfills, adopted by the German state of North Rhin Westphalia (IWL,1990).
The German standards’ used in hydrocarbon soil assessments contamination are mentioned in Table 2.
These values are used to evaluate soil and groundwater contamination status. They allow to decide on the need for further investigations or corrective measures.
As the most industrialized country in this century, the USA felt environmental pollution effects earlier. The USA public structure thus
anticipated itself for pollution control. As regards soil pollution, the concern with the investigation of contaminated soils, of which the
Resource Conservation and Recovery Act (RCRA) is only an example, can be observed already in the Seventies. The polluter-payer
principle is noticeable and federal and state agencies have full authority to enforce soil remediation measures, to be taken by the owner,
operator or individual or organization liable for the problem.
So as to finance such decontamination efforts, a US$1.6 Billion superfund was raised from taxes on crude oil and certain chemicals. The
fund covered costs of recovery activities and paid for the necessary measures to identify, enforce the remediation and obtain refunds from
the liable parties.
The criteria officially adopted to identify the need for corrective measures are based on the effects the contamination causes or may cause
on human health and the environment. Safe concentrations in water (on the surface and in depth), soil (surface and underground),
subsuperficial gas and air are calculated according to concepts of exposure ways and doses, so as not to affect men or the environment
Therefore, the federal EPA has been studying elements/substances on health. Related to petroleum hydrocarbon contamination, we could
mention studies on benzene, ethylbenzene, toluene and xylene.
On Table 3, you can see the concentrations, according to different criteria, for the parameters related to petroleum hydrocarbon soil
The California EPA also uses other parameters as references for the investigation of petroleum hydrocarbon contaminated soils: TPH – Total
Petroleum Hydrocarbon and voe – Volatile Organic Compounds in the subsuperficial air.
A country with a continental area and more recent industrialization, Brazil’s pollution problems became more clearly perceptible only in the last few years and in a localized manner, mainly in large cities, industrial poles and sugarcane monoculture areas.
Despite having an environmental law which is considered advanced, Brazilian regulations on soil protection are still rather incipient. At the federal leveI, there is no legal documentation on the subject, except for that referring to waste that can potentially pollute the soil.
In São Paulo state, Decree # 8468 (08/09/76) deals with aspects of control over waste disposal on the soil, but there is no mention of contaminated soils investigation or remediation. Decree # 32.955 (07/02/91) deals with the conservation of natural groundwater sources in the state. The main elements that relate to this subject are the following:
– requirement of detailed hydrogeological and groundwater vulnerability studies before implementing sources of great environmental impact or danger, as well as protection measures;
– requirement of a detailed hydrogeological characterization for projects of waste disposal on the soil:
– requirement of monitoring and annual submission of reports on areas where there is waste disposal on the soil:
– in case of statistically proven changes in the water quality, the incorporator will be responsible to carry out the necessary work to recover the groundwater.
Since Brazil has not yet adopted soil and groundwater quality standards, drinking water standards (groundwater) and international references are used on taking decisions about remediation. But even in drinking water standards, concentration limits are mentioned only for benzene. Without contaminated soils identification programs, such identification occurs only when the effects are actually perceived by the neighboring population, thus limiting officially controlled sites to a small number. On the other hand, there are private investigation and remediation initiatives by those responsible for the soil contamination, either for pressure from the international headcoropanies or because of international transactions or other reasons.
The first government program for contaminated soil mapping has just started in São Paulo city metropolitan area, implemented by the São Paulo environmental agency in cooperation with a German development agency.
Due to frequent problems of fuel leakage detected in gasoline stations and their consequences, the guidelines for investigation and recovery of soils contaminated with such substances are more developed in São Paulo state.
The parameters adopted for decision-making on recovery measures are the same used in the USA, namely Benzene, Toluene ,
Ethylbenzene, Xylene (BTE&X), TPH (Total Petroleum Hydrocarbon) and VOC (Volatile organic compounds).
ADDRESSING THE PROBLEM
More than other activities related to pollution control, soil contamination investigation requires great care in the planning and field stages.
This is due to the fact that it is necessary to study a material which is not directly accessible, which demands high costs of drilling, tests and collection of samples.
A work chart to address the investigation and remediation of petroleum hydrocarbon contaminated soils is mentioned in Figure 1. The work phases are detailed as follows:
Phase I – Data Survey
In this phase, alI information and data relating to the suspect site are collected, including the following:
– plans and information about the existing facilities and equipment;
– data and information about soil pollution potential sources;
– history of soil contamination and spills;
– geological and hydrogeological information available.
Phase II – Preliminary Diagnosis
Based on the initial data obtained, field work planning is carried out considering:
– specifications of field tests, assessments and studies:
– detailed schedule:
– material and human resources;
– service contracting.
The plan is executed through the development of the following activities:
Identification of contamination sources – through examining the facilities and processes on the site, the history of leakage/spillis and the results off field tests and assessments (waterproof tests in storage tanks, products/waste analysis, etc.)
Field environmental diagnosis – preliminary contamination evaluation through soil, groundwater and subsoil gas testing on the site. Such tests may be carried out using portable testing equipment, test kits or field gas chromatographers.
With the information obtained, a first diagnosis is obtained of contamination signs. In case the tests produce a negative result, a continuing environmental monitoring is suggested. If the results are positive, the area’s hydrogeological and environmental characterization is carried out.
The preliminary diagnosis further allows to evaluate the need for short-term measures, which may include measures to control the soil contamination sources and emergency actions to minimize possible risks to human health, the environment and existing facilities.
Phase III – contamination Characterization
First, the work necessary to characterize the contamination is planned. The planning stage includes the following:
– specifications for soundings, tests and geotechnical analysis;
– specifications for environmental assessments;
– specifications of procedures for drilling and sample collection;
– material and human resources;
– service contracting.
The contamination characterization plan is executed through the development of two parallel activities:
Hydrogeological characterization – by using geological and hydrogeological data available, regional maps of soil use and the information obtained from drilling on the site, the following data must be obtained:
– description of soil layers;
– data on the size of grains and hydraulic conductivity;
– direction of the freatic aquifer flow;
– use of the are a groundwater and soil.
Environmental characterization – mapping and definition of the contamination plume, which are done through the following activities:
– implementation of a monitoring wells network in the freatic aquifer;
– evaluation of phases: (i) free, by means of collection and visual examination of groundwater samples; (ii) retained, by means of collection and chemical analysis of subsoil gases, or collection and chemical analysis of the soil; (iii) dissolved, by means of collection and chemical analysis of groundwater;
– isoconcentration maps tracing;
– evaluation of the contamination plume direction.
Phase IV – Control Measures
The decision on the need for soil or groundwater recovery measures is based on the international standards mentioned earlier and on assessments of potential environmental risks of the contamination for human health or ecosystems.
Therefore, the pollutant’s concentration is calculated in the soil, water, air and plants. Models of massive means of transportation are used to sirou1ate the contamination movement. The exposure evaluation must include the following:
– soil ingestion;
– ingestion of contaminated food;
– ingestion of the water supplied;
– inhalation of particulate vapor and materials;
– skin contact with contaminated materials.
The standard values are defined based on hypothetical exposure ways of each receptor, for several soil use scenarios.
The risks are evaluated through calculating the receptor’s exposure and comparing it to parameters such as the “systemic toxicants” or the “healthbased criteria for carcinogens” (Bulman, 1988).
If there is need for control measures, a recovery plan is prepared for the area, considering the following:
– sanitation technology;
– sanitation limit-levels;
– implementation schedu1e;
– methods to dispose of contaminated materials that may be found in the area;
– sanitation monitoring plan;
– remediation alternatives to minimize the impact on receptors.
TECHNOLOGICAL ALTERNATIVES FOR REMEDIATION
If there is need for adopting soil pollution control measures, the adequate technological alternative is defined, according to an evaluation of the characteristics of contamination, the area and related costs. On Tables 4 and 5, some technological alternatives for the recovery of petroleum hydrocarbon contaminated soils and freatic aquifers are listed and commented.
These alternatives are described below.
Freatic Aquifer Clean-up
This alternative’s main characteristic is to treat the freatic aquifer’s contaminated areas with a minimal soil excavation or water extraction. The options adopted include physio-chemical or biological treatment, according to the summary on Table 6.
It refers to isolating the contamination plume by means of barriers, thus minimizing related risks.
The main methods known to cutoff contamination plumes in aquifers are listed below:
– use of cutoff barriers, such as mud wells, earth curtains and stake walls. These barriers must have extraction wells to reduce pressure at
– use of a hydraulic barrier consisting of a system of extraction wells in the contaminated aquifer so as to cutoff the plume:
– cutoff trenches to stop the flow in less deep aquifers.
We shall not forget that the selection of a plume cutoff method requires a detailed examination of the aquifer physical and geological
Extraction and surface treatment
The most widely used corrective action is the extraction of the aquifer’s contaminated water (through gravity flows in trenches and drains, or
through pumping), followed by the surface treatment through traditional chemical engineering processes. This alternative of extraction and
surface treatment is generally combined with the plume cutoff. The contaminated water extracted from the aquifer may be treated using
individual or combined biological, chemical, physic or therma1 treatment processes.
This alternative requires the use of chemicals to transform the contaminating agent into a non-toxic element. The treatment may be used
individually or combined with a biological treatment to reduce or to eliminate the soil contamination. This alternative is usually adopted in
cases when the soil contamination is caused by watersoluble light compounds. The procedure adopted is to promote leaching of the
contaminated soil 1ayers, with the use of detergents and a subsuperficial drainage network.
This alternative includes the local treatment of the soil contaminated parts by using microorganisms or enzymes that can degrade the
contaminating agents. It is usually adopted in cases when the soil contamination is caused by heavy organic compounds. The procedures
adopted aim at the degradation of the contaminating agents, accelerated by airing the soil (through ploughing) and adding nutrients (an
aqueous fertilizer solution).
This alternative requires removal of the soil contaminated parts and elimination of the contaminating agents through incineration. This
procedure supposes high costs and is thus adopted only in very restricted contaminated areas with highly toxic contaminating agents.
Due to severe soil contamination cases in gasoline stations, oil companies and environmental agencies in Brazil begin to search for stricter
environmental standards. Waterproof tests and environmental assessments of soil contamination are usually required when gasoline
stations change their flags.
Therefore, the work methodology must be adjusted according to each specific case and there must be special care during the planning and field stages.
The parameters adopted and assessment methodologies must be carefully calibrated to validate the proposed addressing model.
The use of the soil along with potential contamination risks will increasingly dictate the need for remediation measures, as well as their limitations and the
techniques adopted to accomplish the desired goals.
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