The absence of the capillary rim in the monitoring well causes the well to act as a trough into which LNAPL will drain. When LNAPL accumulates in the well, the weight of the LNAPL will depress the water table in the well, resulting in additional LNAPL drainage into the well.
INTRODUCTION
AIM AND STRUCTURE OF THE STUDY
LIGHT NON-AQUEOUS PHASE LIQUIDS
LNAPLs defined
Importance of LNAPL solubility
The addition of the MTBE additive at a concentration of 7% significantly increased the total solubility in gasoline to 782 mg/l. Nadim et al (2000) indicate that the high solubility of MTBE is due to the presence of the oxygen atom in its structure.
LNAPL PRODUCTION AND CHARACTERISTICS
Petrol
Octane number is determined by the "lightness" of the product and is an inverse function of sg (Speight, 1998). Current fuel additives to increase octane include MTBE oxygenate, which can appear in gasoline up to 15 vol. % (Grunwald, 2000 and Ahmed, 2001).
Diesel
Although diesel is referred to as having carbon compounds greater than C9, BTEX compounds (lighter than C9) can also be found in diesel at trace concentrations.
Product Classes
RISKS ASSOCIATED WITH LNAPLs
- Increasing oil production
- Widespread LNAPL distribution and transportation
- LNAPL toxicity and flammability
- Groundwater vulnerability
- Costs of cleanup
- Limits to absolute remediation
- Ecological impacts
- Inadvertent spreading of contamination
- Human error and the inability to prevent all contamination
- Absence of legislation for dated equipment
- Absence of definitive clean-up guideline values
- Absence of motivation for preventative measures
- Availability of data
- Identifying a source
Risks can therefore occur in the work environment due to the potential presence of a flammable substance and explosive atmosphere. In comparison, the combined costs of LNAPL contamination remediation incurred by oil companies in South Africa are not in the public domain.
REGULATORY REVIEW
- United Kingdom
- Tanks
- Lines
- United States of America
- Installation
- Leak Detection
- Spill Prevention Infrastructure
- Overfill Protection
- Corrosion Protection
- Other
- South Africa
- National government
- Provincial government
- eThekwini Municipality structures and regulations
- South African National Standards code of practise
- Tank and pipe manufacture in South Africa
- Summary of regulatory review
- Key contamination and leak prevention mechanisms
- Voluntary oil industry specifications
Displacement valves can be installed under the dispenser pumps, activated in the event of the dispenser tipping over;. Existing sites are scrutinized using the Product Inventory Loss Policy (PILP) and interventions are implemented according to certain criteria (Engen, 2009).
STORAGE TANK SYSTEMS AND SOURCES OF LNAPL CONTAMINATION 32
- Failure
- Mechanical factors
- Corrosion factors
- General description and failure mechanisms of UST systems
- Above-ground storage tanks
- Failure literature
- USTs in the United States of America
- South African context
Corrosion can be caused due to any of the following mechanisms: pitting, chemical, galvanic, stress, biological, crevice and erosion. The study's findings showed that approximately 35% of the estimated 796,000 fuel USTs in the US were leaking at that time.
DATA SOURCE AND CLEANUP
- eThekwini Fire and Emergency Services data
- Teleatlas data
- Consultancy data
- Regulatory assessment
eThekwini Fire and Emergency Services are responsible for responding to fire-related issues; as well as the routine inspection of commercial and industrial properties to comply with SABS 0400: The Application of the National Building Regulations (SANS, 1990) and the Interim Code Relating to Fire Prevention and Flammable Liquids and Substances (Durban Metropolitan Council, undated). Sites within eThekwini The database included sites from outside the eThekwini region (according to their names) and were therefore excluded.
DATA RESULTS AND DISCUSSION
- Age of sites
Note that SANS Storage and Distribution of Petroleum Products in Above Ground Bulk Facilities has shown Class 2 to have a flash point of >38°C and <60.5°C. Given that some MSDS (e.g. Engen diesel MSDS, Engen Product Safety Advisor, 2006) for diesel indicate the flash point. All of the above fields were found to be relatively incomplete, with the exception of the COR Date Approved field, where of the 1,456 records retrieved, 1,137 sites had a COR Date Approved recorded.
The COR age represents the age at which the current installation at each site was approved by the eThekwini Fire and Emergency Service to store a flammable liquid. This certification requires renewal when there is a change in capacity or when there is a change in ownership.
Teleatlas data
Total operates 36 fuel stations, while Exel and Sasol both operate fewer than 15 locations in eThekwini. Considering that eThekwini Fire and Emergency Services data recorded a total of 1 456 petrol stations and commercial installations, this amounts to a total of 1 100 commercial installations in eThekwini (according to the data category specified).
Consultancy data
- Triggers for assessment and the introduction of bias
- Contamination status
- Type of sites assessed
- Causes of contamination
- Age of failure
- Pump type
- Volume lost
- Relationship between tank age and volume loss
- Modelling of indicator variables
The causes of contamination are mainly equipment or infrastructure failure; and cases where the cause was unknown. The graph below presents the causes of contamination for the study sites in the consultancy sample data set (n=182). The chart includes sites where the cause of contamination is unknown and excludes sites that are not considered contaminated (according to the decision tree model).
This dynamic nature of the business results in the loss of information related to the cause of the contamination. Distribution spillage (n=5) was observed as a cause of contamination where soil and/or groundwater contamination occurs as a result of spillage prior to the point of distribution. The former contamination of the reservoirs is noted where the actual cause of the contamination was unknown, however the excavation was found to be contaminated.
Top ten countries by largest volume lost where pump type was known (n=10) Volume lost (L) Cause of pollution Pump type. The site with the lowest predicted probability of contamination (excluding unknown variables) was a commercial above-ground installation consisting of a mild steel tank and served by a suction pump. The site with the highest predicted probability of contamination was a retail site consisting of underground tanks of mild steel construction material and served by submersible pumps.
CONCLUSIONS AND RECOMMENDATIONS
- eThekwini Fire and Emergency Service database
- Teleatlas GIS database
- Consultancy database
- Causes of contamination
- Severity of an incident
- Logistic regression model
- Municipal governance and regulations
- Loss reporting
- National governance and regulations
- Probabilistic model and competencies
- Non-uniform risk based approach
- Investigation of new technologies
The results indicated that, as product lines aged, especially mild steel pipes, the likelihood of contamination risk also increased, considering a positive coefficient a of the best-fitting regression line. Subsoil contamination has been found to occur as a result of operational practices, such as tank overfilling. The above findings are supported by the results of the logistic regression where a relatively higher risk is posed by retail locations served by mild steel USTs and submersible pumps, compared to commercial locations where the installation is typically above ground and serviced by a suction pump. .
This would require the adoption of the eThekwini fire and emergency response database or the establishment of a new database. The guidelines should be prescribed in the context of the current and future use of underground storage, as described by Evans et al (2009) in his paper examining the use of 'land below ground' in the UK. Similarly, the effectiveness of the EIA process required prior to remediation should be determined by evaluating a number of test sites.
Therefore, it is recommended that a probabilistic model be constructed using one of the above two methodologies to determine the likely failure rate of commercial and retail LNAPL. The results of the probabilistic model can feed back into the design of various components of USTs and tap infrastructure to enable more accurate failure prediction. The reliability of components is also dictated by the competence of designers and contractors; and build quality.
Plain Talk Motor Fuel Tanks: An Operator's Guide to Maine's Underground Tank Rules. Establishing regulatory procedures to deal with leaking underground storage tanks in South Africa. Real-time remote monitoring and control of contamination in underground gasoline tank systems.
Glass-reinforced steel tanks with polyester lining for underground storage of hydrocarbons and oxygenated solvents and intended for horizontal burial. Part 280: Technical Standards and Remedial Action Requirements for Owners and Operators of Underground Storage Tanks.
BIBLIOGRAPHY
Bioremediation of oil refinery sludge by soil farming in semiarid conditions: influence on soil microbial activity. Factors preventing the successful implementation of the polluter pays principle: A case study of the Bayne's Spruit. The evaluation of liquid hydrocarbon contamination of soil around petrochemical tank farms at a Durban refinery.
Field and laboratory research to study the fate and transport of dense non-aqueous phase liquids (DNAPLs) in groundwater.
APPENDICES
APPENDIX A: GAS CHROMATOGRAPH OF PETROL
APPENDIX B: LEGISLATED SANS STANDARDS APPLICABLE TO THE FUEL
SOUTH AFRICA'S ELECTRICITY INDUSTRY: REGIONAL EXPANSION A SOUTH AFRICA'S MAJOR ELECTRICITY INDUSTRY: REGIONAL EXPANSION A MAIN COLLECTIVE AGREEMENT APPROVED BY LOCAL COMMUNITIES INCORPORATION OF SAFETY STANDARDS Regulation. FIRE SERVICES, PUBLIC VEHICLES, PARKING, PARKING METERS, DOGS, TRAFFIC AND SHOORN MUNICIPALITIES: FIRE SAFETY ACT. FIRE SERVICES, PUBLIC VEHICLES, PARKING, PARKING METERS, DOGS, TRAFFIC MUNICIPALITY AND FIRE SAFETY MUNICIPALITY.
ELECTRICAL INDUSTRY OF SOUTH AFRICA: EXTENSION OF REGION A MAIN ELECTRICAL INDUSTRY OF SOUTH AFRICA: EXTENSION OF REGION A MAIN COLLECTIVE AGREEMENT TONON PARTY COLLECTIVE AGREEMENTS TO NON-PARTY SELECTIVE INSTALLATION REGULATIONS. Petroleum Industry Part 3: Installation of Underground Storage Tanks, Pumps/Dispensers and Pipelines at Service Stations and Consumer Installations Petroleum Industry Part 3: Installation of Underground Storage Tanks, Pumps/Dispensers and Pipelines at Service Stations and Consumer Installations Oil Industry Part 3: Installation of Underground Storage Tanks, Pumps/Dispensers and Pipelines at service stations and consumer installations Petroleum industry Part 3: Installation of underground storage tanks, pumps/dispensers and pipelines at service stations and consumer installations Petroleum industry Part 3: Installation, modification and decommissioning of underground storage tanks, pumps/dispensers and piping systems at service stations and Petroleum industry Part 3: Installation of underground storage tanks, pumps/dispensers and pipelines at service stations and consumer installations Oil industry Part 3: Installation of underground storage tanks, pumps/dispensers and pipelines at service stations and consumer installations Oil industry Part 3: Installation of underground storage tanks, pumps/dispensers and pipelines at service stations and consumer installations. Petroleum industry Part 3: Installation of underground storage tanks, pumps/dispensers and pipelines at service stations and consumer installations Petroleum industry Part 3: Installation of underground storage tanks, pumps/dispensers and pipelines at service stations and consumer installations Oil industry Part 3: Installation of underground storage tanks, pumps /dispensers and pipeworkat service stations and consumerinstallationsThe Petroleum industry Part 3: Theinstallation of underground storagetanks, pumps/dispensers and pipeworkat service stations and consumerinstallationsThe Petroleum industry Part 3: Theinstallation of underground storagetanks, pumps/dispensers and pipeworkat service stations and consumerinstallations Title.
APPENDIX C: APPLICATION FORM FOR CERTIFICATE OF REGISTRATION
Application for Certificate of Premises Registration under Interim Code Relating to Fire Prevention and Flammable Liquids and Substances. This form must be completed and sent to the Chief Fire Officer, Fire Department, along with a floor plan in accordance with the Interior Code. Provide the address of the premises you wish to register and the name of the owner.
Indicate the total quantity of each class in liters proposed to be kept on the containers.
APPENDIX D: FIRE PREVENTION WORKSHEET
APPENDIX F: OCCUPANCY CODES
APPENDIX G: CONSULTANCY DATA, DATA QUALIFICATION AND NOTES
APPENDIX H: FAULT TREE OF CAUSES OF CONTAMINATION AND RELATED
APPENDIX I: CODED DATA VARIABLES
APPENDIX J: LOGISTIC REGRESSION MODEL RESULTS
APPENDIX K: POLLUTION CONTROL OFFICER WORKSHEET
APPENDIX L: FUEL FACILITY QUESTIONNAIRE
Any comments, clarifications or additional explanations can be written in the space provided at the bottom of the survey form (Section F). If you would like to receive the results of this survey, please indicate the postal address to which they should be sent.
