FAQ, Resources, Links
What is Environmental Engineering?
Environmental engineering is the application of science and engineering principles to improve the environment (air, water, and/or land resources), to provide healthful water, air, and land for human habitation and for other organisms, and to remediate polluted sites. Negative environmental effects can be decreased and controlled through public education, conservation, regulations, and the application of good engineering practices. "Pollutants" may be chemical, biological, thermal, radioactive, or even mechanical. Environmental engineering emphasizes several areas: process engineering, environmental chemistry, water and wastewater treatment (sanitary engineering), waste reduction/management, and pollution prevention/cleanup.
What is Phase I Environmental Site Assessment?
A Phase I Environmental Site Assessment is a report prepared for a real estate holding which identifies potential or existing environmental contamination liabilities. The analysis, often called a Phase I ESA, typically addresses both the underlying land as well as physical improvements to the property; however, techniques applied in a Phase I ESA never include actual collection of physical samples or chemical analyses of any kind. Scrutiny of the land includes examination of potential soil contamination, groundwater quality, surface water quality and sometimes issues related to hazardous substance uptake by biota. The examination of a site may include: definition of any chemical residues within structures; identification of possible asbestos containing building materials; inventory of hazardous substances stored or used on site; assessment of mold and mildew; and evaluation of other indoor air quality parameters.
Actual sampling of soil, air, groundwater and/or building materials is typically not conducted during a Phase I ESA. The Phase I ESA is generally considered the first step in the process of environmental Due Diligence. This type of study is alternatively called a Level I Environmental Site Assessment. Standards for performing a Phase I site assessment have been promulgated by ASTM in Standard E1527-05. If a site is considered contaminated, a Phase II Environmental Site Assessment may be conducted, ASTM test E1903, a more detailed investigation involving chemical analysis for hazardous substances and/or petroleum hydrocarbons.
Scope of Phase I
Depending upon precise protocols utilized, there are a number of variations in the scope of a Phase I study. The tasks listed here are extremely common to almost all Phase I ESAs:
- Performance of an on-site visit to view present conditions (chemical spill residue, die-back of vegetation, etc) ; hazardous substances or petroleum products usage (presence of above ground or underground storage tanks, storage of acids, etc.); and evaluate any likely environmentally hazardous site history.
- Evaluation of risks of neighboring properties upon the subject property
- Interview of persons knowledgeable regarding the property history (past owners, present owner, key site manager, present tenants, neighbors).
- Examine municipal or county planning files to check prior land usage and permits granted
- Conduct file searches with public agencies (State water board, fire department, county health department, etc) having oversight relative to water quality and soil contamination issues.
- Examine historic aerial photography of the vicinity.
- Examine current USGS maps to scrutinize drainage patterns and topography.
- Examine chain-of-title for Environmental Liens and/or Activity and Land Use Limitations (AULs).
Non-Scope Items in a Phase I Environmental Site Assessments can include visual inspections or records review searches for:
- Asbestos Containing Building Materials (ACBM)
- Lead-Based Paint
- Lead in Drinking Water
- Threatened and Endangered Species
- Earthquake Hazard
What is Phase II Environmental Site Assessment?
Phase II Environmental Site Assessment is an investigation which collects original samples of soil, groundwater or building materials to analyze for quantitative values of various contaminants. This investigation is normally undertaken when a Phase I ESA determines a likelihood of site contamination. The most frequent substances tested are petroleum hydrocarbons, heavy metals, pesticides, solvents, asbestos and mold.
What is Phase III Environmental Site Assessment?
Phase III Environmental Site Assessment is an investigation involving remediation of a site. This study normally involves assessment of alternative cleanup methods, costs and logistics. The associated reportage details the steps taken to perform site cleanup and the follow-up monitoring for residual contaminants.
What is Environmental Site Remediation?
Environmental remediation deals with the removal of pollution or contaminants from environmental media such as soil, groundwater, sediment, or surface water for the general protection of human health and the environment or from a brownfield site intended for redevelopment. Remediation is generally subject to an array of regulatory requirements, and also can be based on assessments of human health and ecological risks where no legislated standards exist or where standards are advisory.
Remediation technologies are many and varied but can be categorized into ex-situ and in-situ methods. Ex-situ methods involve excavation of impacted soils and subsequent treatment at the surface, In-situ methods seek to treat the contamination without removing the soils.
The more traditional remediation approach (used almost exclusively on contaminated sites from the 1970s to the 1990s) consists primarily of soil excavation and disposal to "landfill" (dig and dump) and groundwater "pump and treat".
Excavation or dredging
"Excavation" processes can be as simple as hauling the contaminated soil to a regulated landfill, but can also involve aerating the excavated material in the case of volatile organic contaminants. If the contamination affects a river or bay bottom, then dredging of bay mud or other silty clays containing contaminants may be conducted.
Pump and Treat
"Pump and treat" involves pumping out contaminated groundwater with the use of a submersible or vacuum pump, and allowing the extracted groundwater to be purified by slowly proceeding through a series of vessels that contain materials designed to adsorb the contaminants from the groundwater. For petroleum impacted sites this material is usually activated carbon in granular form. Chemical reagents such as flocculants and sand filters may also be used to decrease the contamination of groundwater.
Depending on geology and soil type, "pump and treat" may be a good method to quickly reduce high concentrations of pollutants. It is more difficult to reach sufficiently low concentrations to satisfy remediation standards, due to the equilibrium of absorption/desorption processes in the soil.
In Situ Oxidation
New "in situ oxidation" technologies have become popular, for remediation of a wide range of soil and groundwater contaminants. Remediation by chemical oxidation involves the injection of strong oxidants such as hydrogen peroxide, ozone gas, potassium permanganate or persulfates.
Oxygen gas or ambient air can also be injected as a more mild approach. One disadvantage of this approach is the possibility of less contaminant destruction by natural attenuation if the bacteria which normally live in the soil prefer a reducing environment. The injection of gases into the groundwater may also cause contamination to spread faster than normal depending on the site's hydrogeology.
Soil Vapor Extraction
Soil vapor extraction and oxidation (or incineration) can also be an effective remediation technology. This approach is somewhat controversial because of the risks of dioxins released in the atmosphere through the exhaust gases. Controlled, high temperature incineration with filtering of exhaust gases however should not pose any risks. Two different technologies can be employed to oxidize the contaminants of an extracted vapor stream.
1. thermal oxidation which uses a system that acts as a furnace and maintains temperatures ranging from 1350°F to 1500°F (730°C-815°C).
2. catalytic oxidation which uses a catalyst on a support to facilitate a lower temperature oxidation. This system usually maintains temperatures ranging from 600°F to 800°F (315°C-430°C).
Thermal oxidation is more useful for higher concentration influent vapor streams (which require less natural gas usage) than catalytic oxidation.
For low level concentrations, extracted vapors can also be treated by allowing them to flow through a series of vessels designed for vapor flow. These vessels contain materials designed to adsorb the contaminants from the vapors. The adsorbant is usually activated carbon in granular form.
The treatment of environmental problems through biological means is known as bioremediation and the specific use of plants for example by using phytoremediation. Bioremediation is sometimes used in conjunction with a pump and treat system. In bioremediation, either naturally occurring or specially bred bacteria are used to consume contaminants from extracted groundwater. This is sometimes referred to as a bio-gac system. Many times the groundwater is recycled to allow for continuously flowing water and enhanced bacteria population growth. Occasionally the bacteria can build up to such a point that they can affect filtration and pumping. The vessel should then be partially drained. Care must be taken to ensure that a sharp change in the groundwater chemistry does not kill the bacteria (such as a sudden change in pH).
Dual-phase extraction utilizes a soil vapor extraction system that produces a high vacuum resulting in the extraction of both contaminated vapors as well as a limited amount of contaminated groundwater. This method is somewhat inefficient due to large amount of energy required by pulling water by vacuum compared to pushing water with a submersible pump.