- possibility for contamination
Evidence obtained from historical maps and the present usage of the site indicate that possible sources as well as processes perpetuating contamination on the site may have occurred. Examples of such possible sources are:
Electrical sub-station- chilling oils as well as polychlorinated biphenyls (PCBs) that may have originated from previous electrical transformers as well as capacitors, together with oils and solvents originating from plant as well as equipment maintenance may be present in such kind of a site. In other instances, asbestos may also be present in the site particularly when used for various purposes, including padding, roofing or even cladding.
Garage- a huge variety of contaminants may be found at the site depending on the type of material stored within its locality. As such, contamination may be as a result of leakage as well as spillage of stored materials when transferring drums and barrels.
Petrol station- various contaminants that may potentially come from filling stations include BTEX, lead, hydrocarbons, explosive gases, arenes, oils, as well as halogenated solvents.
Evidence drawn from the past maps of the site further shows that there are possible sources of contamination from the land neighboring the site. The potential contaminants from the land neighboring the site may come from sources such as:
Engineering works- contamination on land may result from engineering works due to fuels, lubricants, hydraulic substances, solvents used to dilute paints, as well as heavy metals that come from welding, chopping, grinding and shot blasting activities. Contaminants may also result from metal compounds that may have been employed either as pigments or anti-oxidation agents in paints or as catalyst ingredients in anti-pollution treatments where their potentially harmful oxides as well as asbestos may be employed as the primary padding material. Remains of coal and waste ash may also constitute to potential sources of contamination particularly in aged sites.
Works- probable sources of contamination may also be present in non-specified sector of physical activity thereby causing harmful impact into a site. The various contaminants that may be present in such places include asbestos, metals and hydrocarbons.
Cooling wood-various materials used in wood treatment may as well be possible sources of contaminants. Such materials include organic materials such as solvents and phenols, metals, asbestos as well as PCB.
Laundry service-contaminant materials that may be released in the laundry service may pose potential impact into a site. For instance, soil released in the laundry service may contain contaminants such as Tetrachloroethylene together with Perchloroethylene, which may have resulted from dispensation of chlorinated solvents from storage tanks that may be situated near the site.
Depot- a depot existing near a site may be contaminated with various products, including grease and oils among other petroleum products that either leak or spill from a storage tank.
From the evidence gathered from the reviewed information, it is obvious that previous land uses near the site may have perpetuated possible contamination of surrounding soils as well as lowered quality of both the ground and service waters especially in instances where such contaminants may have had the capacity to shift from one location to another. This means that there is a high probability that soils as well as dredging materials employed to construct the site may have been contaminated to a certain degree both through past as well as present land uses within the site and it the adjacent areas.
- environmental set-up
Evidence gathered from the British Geological Research (GBS) indicates that the site basically comprises of artificial ground that overlies a superficial layer constituting of tiny deposits of beach as well as tidal products, including sand, clay as well as silt. These beach and tidal deposits are then underlain by a bedrock layer, which is made up of March Farm in addition to sand formations constituting of sand, clay as well as silt.
2.1.1 The bedrock layer
The bedrock layer is made up Marsh Farm as well as sand formations, which comprise of sand, clay as well as silt. Historical evidence shows that this sedimentary bedrock was established during the Palaeogene period in about thirty four to fifty six million years ago. The rocks were especially established in shallow seas where siliciclastic sediments, which mainly constituted of small fragments of silicate substances, were deposited in form of sand, mire, silt as well as gravel.
2.2.2 Superficial layer
The superficial layer comprises of a tidal plane-like deposit of beach products such as sand, clay as well as silt. The layer is said to have formed in about two million years ago in shoreline localities while sediments were placed along beaches as well as barrier islands.
- Reality relating to contamination that result from gas stations
The fact that the site prevails near a garage/gas station shows that there is a high probability for adjacent-surface contamination resulting from possible leakage of products such as petrol, lubricants, diesel and grease among other forms of oils. Contamination would especially take place if there is any leakage from tanks and pipes, which allow contaminant products to mix with adjacent soils and surface water. As such, air and soil pollution within the site are usually linked to contaminants emanating from gas stations. Air pollution mainly results from volatile products that vaporize during the filling process. On the other hand, soil pollution results from rusting as well as leakage of underground pipes that slowly release contaminant products into the neighboring region (Sehgal, 2011). Gas stations are also potential locations where soils may be contaminated with hydrocarbons especially because storage tanks are likely to leak as well as spill their content during fuel dispensation process. Similarly, the release of volatile products contained in gasoline, including benzene as well as semi-volatile products contained in diesel can cause toxic and cancerous effects, which may in return lead to serious implications both in the ecosystem and public health (Rosales, 2014). Additionally, light non-aqueous substances that may be leaking from storage tanks can add toxic content to ground water thereby putting both human and animal health at risk particularly if underground plume permeate an aquifer and distributes into boreholes and other water sources that are widely used for irrigation and other domestic uses. This substance further exposes both the flora and fauna to dangerous vapor. Scholarly inquiries have confirmed that leaking contaminants can spread to more than four hundred and fifty meters from the source. The degree of contamination is usually described on basis of level of concentration of the contaminants. For instance concentration of benzene in groundwater can range between ten to ten thousand parts, which explain that the level of impact instilled on human and animal health may vary significantly (PHS, 1999).
Certain organisms living both in water and soil, including bacteria and fungi, in addition to various chemical and physical activities may degrade the level of hydrocarbon contaminants without any human interference. This in return can reduce the amount, mobility, lethalness, as well as concentration of contaminants prevailing both in soil and groundwater. Compared to other microorganisms, bacteria are most vigorous in degrading petroleum contaminants. The in-situ procedures that the bacteria go through in degrading these contaminants are biodegradation, distribution, de-concentration, sorption as well as volatilization (NASGC, 2015). In instances where petroleum may have leaked from under-surface storage tanks and dispersed into the underground aquifers, it is possible for humans to drink from a water source that is contaminated with hydrocarbons. They may as well breathe air that is contaminated with volatile gases or consume hydrocarbons by eating fish that may have been obtained from a water source situated near a leaking storage tank. On the other hand, children may be exposed to toxic substances if the play in soil that may be contaminated with products that contain hydrocarbon (P HS, 1999).
The extent of health implications resulting from contact with petroleum hydrocarbon differ depending the level of substance concentration as well as the duration of time during which a person is exposed. While breathing petroleum hydrocarbon vapors can impact the human CNS, length exposures can lead to comma or even death. Similarly, inhaling toluene whose concentration is higher than one hundred parts for every million for long periods of time can cause headache, tiredness, nausea or even drowsiness. The symptoms can however disappear when exposure to this contaminant substance is stopped. However, lengthy exposure to this substance can cause permanent damage on the CNS. Liquid petroleum can lead to skin irritation when one comes into direct contact with the product externally or when some of it is absorbed through the skin. Further health implications can result from benzene, which has proven to cause leukemia among humans (TPH, 2015).
4.0 The Reality about contamination that results from laundry surface
sufficient evidence indicates that Tetrachloroethylene, which is a common product employed during dry cleaning, is a popular soil contaminant. At a gravity that is higher than one, the product exists as an intense non-aqueous phase product especially when enough quantities are released (PHS, 2015). The product may either evaporate rapidly from shallow soils or may infiltrate deeper into the soil and mix with underground water. It however takes time before it can be degraded in the soil. People that may be exposed to small proportions of this product for a lengthy period of time can experience swaying moods, memory loss, poor attention, slow attention or impaired vision (TTNAT website, 2012).
THEORETICAL SITE MODEL AND ENVIRONMENTAL HAZARD EVALUATION
The central aim for conducting this desk study is to come up with a preliminary theoretical model of the site so as to determine whether there are any potentially hazardous risks as well as propose the necessary action to generate further information that can help refine the model as well as validate the risks. As outlined in Section II of the 1990 Environmental Protection Act, land contamination is usually evaluated through the recognition as well as assessment of pollutant linkages, measured in terms of the relationship prevailing between contaminant source, passageway and the receptor (Copyright, 1990). The UK perspective in consolidating contaminated land is usually founded on the risk assessment principles, which aid in assessing if pollutant leakages may relevant. Prior to engaging in a risk assessment activity it is appropriate to create a conceptual model that would help in establishing possible contamination sources, passageways and receptors that might prevail within and nearby the site. An evaluation of environmental risks basically depends on the identification of three basic elements that constitute to a pollutant linkage. These basic elements include:
SOURCE: this refers to the contaminant
PATHWAY/PASSENGEWAY: this refines the path by which the contaminant can shift from one location to another.
RECEPTOR: this refers to any organism, including people, animals as well as plants, or properties and controlled water that is likely to be negatively impacted by the contaminant.
While these elements have to mutually co-exist in a site for possible risk to take place, the absence of any of them means that there is no possible risk that can take place.
A pilot theoretical site has been established as part of this desk study so as help determine possible environmental risks in relation to the past and present site uses as well as its possible use for unidentified development.
6.0 Qualitative hazard assessment
Qualitative assessment of site-related risks looks at the present or forecasted site usage depending on its appropriateness for use. This allows for the application of risk assessment standards to help evaluate possible impacts and concerns linked to contamination, which is usually conducted on basis of specifications linked to a specific site.
Potential health and environmental impacts taking place as a result of forecasted site developments can raise concern within site localities when various sources of contamination, as outlined above, may be present on the site. There is a high probability that chemical contaminants linked to previous or current land use may present in the soil. If such contaminants are present in the soil particularly in large quantities, they may perpetuate direct impacts on people, animals as well as plants, which mainly result from their toxicological and even hazardous characteristics.
7.0 conclusions as well as recommendations
Plans for the application of any future site development will require extra but viable inquiry and risk assessment of past and present development works. A pilot risk assessment as well as an extensive site investigation needs to be conducted by site developers to determine whether there is any risk associated with possible contamination that may interfere with site development process. While the assessment should be based on the intended use of the site, investigations should be conducted on the site to ensure that any contamination that may be present at the site does not exist in levels that may pose threats to potential future site users, constructors, ground water, plants, the forecasted redevelopment as well as the wider environment.
The sampling approach employed in the assessment should be designed in a manner that ensures sufficient determination of whether important pollutant linkages are present or not. An assessment will further be needed to help establish the degree of contamination, which would in return ensure that the most appropriate risk management and remedial option is chosen. The investigations as well as assessments should be based of Code of Conduct in Investigations and Assessments of Possibly Contaminated Sites as outlined under the British Standard 10175: 2011. An extensive investigation should also be designed to validate the assumptions made in the pilot theoretical model created as well as to perpetuate a more extensive risk assessment to be conducted.
The scope of inquiry should also constitute of extensive investigations that can help recover and test soil samples that would in return be used in chemical analysis. Soil samples should be screened for asbestos and the process should take place both at regular and alternate intervals in strata.
A sequence of tactically positioned pits should be assessed to nature and type of ground fill as well as the underlying stratum. A lasting gas installation scrutiny should be carried out to ensure that a gas membrane is installed in the final construction design.
Additionally, geotechnical screening should be carried out to gather relevant information needed for a pilot assessment of various forecasted development proposals.
In terms of the artificial materials positioned in the empty space following the extraction of underground storage tanks, the backfill materials should be tested to determine whether they are viable for re-use. Constant supervision should also be carried out to ensure that there is no residual contamination both on the sides as well as the bottom of pit.
8.0 Remedial strategy
Evidence provided by LLP (2016) shows that gas stations are major target sites that can be used for redevelopment. This is especially because there is an extensive presence of curb cuts that could be adopted and be eligible for reuse by the new site developer. This is often desirable especially among communities that control curb cuts as well as traffic flow.
8.1 Physical Treatment
Certain physical treatment strategies can be employed to distract contaminants from soil as well as ground water through the use of various chemical and physical attributes of these contaminants. After this separation, the contaminants can either be disposed or recycled. In other instances, physical treatment can be integrated with either chemical or biological treatment to enhance optimum remediation of the site.
8.2 Biological treatment
Remediation at the site may further be realised through employment of biological treatment strategies, which mainly depend on micro-organisms including bacteria, protozoa, algae as well as fungi. These micro-organisms usually eradicate, soothe or even convert organic pollutants prevailing in soil or ground water. For instance, micro-organisms can, under an aerobic state, convert fuel compounds through the process of mineralization to corm CO2, water as well as biomass. The mineralization process takes place naturally but can be supported through in-situ as well as ex-situ through various validated approaches.
8.3 Chemical treatment
Remediation may also be realised through chemical approaches, which primarily entail using chemical reactions to damage, convert or inactivate chemical contaminants. Chemical reactions can be applied for various purposes including:
Stabilization-this entails the alteration of harmful components in soil in order to lower their solubility, mobility and toxicity. The process is usually integrated with solidification procedures.
Permeable reactive inhibitors- this refers to an engineering treatment procedure that is usually implemented in the saturated zone to allow passage of ground water while on the other hand immobilizing as well as converting the pollutant materials.
Chemical oxidation-this refers to the transformation of contaminants into less toxic substances through chemically adding oxygen.