Results:

National Grid operate Pressure Reduction Installations (PRI) on the transmission system in the UK and the US. These installations are predominantly maintained and operated to generic procedures which do not fully take into account location or site specific risks. National Grid has initiated work to develop decision support tools (DST5) which take into account location and site specific risk.

This report describes the PRI DST risk ranking model and scoring logic. The model development has been informed by Take and Regulator Station models and advice provided by the National Grid US operator. The PRI DST provides a qualitative assessment of the supply and safety risks associated with PRI design based on factors which affect the ability to continue to supply gas under fault conditions and the installation's reliability, integrity and condition. The qualitative risk model assigns numeric scores to each factor and calculates an overall risk score which reflects the likelihood of a supply failure or a loss of containment incident. The qualitative risk model will enable an assessment of the sites which are most vulnerable to failure against consistent criteria and allow these sites to be prioritised for more detailed consideration.

Ranking of risk scores will enable efficient and reliable sites to be identified, and the learning obtained can be applied to new sites and sites targeted for investment.

The use of qualitative risk models in the development of maintenance requirements is established good practice, but it is recognised that the availability and access to data can be problematic and can limit the use and application of such models. To address this, the tool is structured to efficiently use the experience and knowledge of National Grid operational personnel and accessible data.

The ability to disperse spilled oils at sea depends on several factors, including oil properties, prevailing sea-state and the treatment rate of oil spill dispersant applied to the oil.

Oil spill dispersants function by allowing a high proportion of the spilled oil volume to be converted by cresting wave action into very small oil droplets that are permanently dispersed. Oil spill dispersants do this because the surfactants that they contain are capable of causing a very large decrease in the oil / water interfacial tension (IFT). IFT (or surface free energy) is caused by the dissimilarity between the polar nature of the molecules of water and the non-polar nature of the hydrocarbon molecules of oil.

The work described in this report was a 'return to the basics' of using dispersants; an attempt to use a matrix of oil viscosity, dispersant brand, dispersant treatment rate and prevailing sea conditions to provide information on the limiting oil viscosity of dispersion by using a very simple method of visual observation to determine whether dispersion was or was not occurring.

The report concludes that some oil spill dispersants will be an effective response to oils with viscosity of 2,000 cP, but will not be effective on oils with a viscosity of 7,000 cP or more, in waves associated with wind speeds of 7 to 14 knots. The precise limiting viscosity between 2,000 and 7,000 cP is not known. The limiting viscosity will increase with wind speed; it is possible that oil with a viscosity of 7,000 cP will disperse at 20 or more knots wind speed. However, it was not possible to test this at sea.

1. Reasons for the Work
2. Dispersion of Spilled Oil at Sea
3. The 2003 UK Sea-Trials
4. Comparison of the Sea Trial Results with Results from Laboratory Tests
5. Conclusions

• Appendix 1 - Results obtained in Sea Trials

The objective of the 40mm Serviflex project is to prove the suitability of using a 40mm Serviflex pipe to renew 2" steel on Great Britain's (GB) gas network. The main application that this will be beneficial to is the replacement of the below ground approach mains for network risers.

SGN have almost 200 thousand network risers within multiple occupancy buildings throughout its Scotland and Southern networks. A common factor that results in risers being deemed unsuitable and subject to a full replacement is the deterioration of the below ground approach mains sections of risers, which are commonly found to be constructed from 2" steel. Serviflex is a corrugated dual wall liner manufactured by Radius Systems Ltd that when used with specialist installation equipment can negotiate tight bends without compromising its design life. SGN currently utilises the 20mm Serviflex pipe to renew gas mains services up to 1 ¼" back to the original meter position.

The use of 40mm Serviflex in riser repair applications will allow the partial repair and refurbishment of existing risers as opposed to the full replacement of them, resulting in reduced time required by SGN and minimising disruptions. It will also allow for these activities to be carried out with less disruption (excavations, lifting floor boards etc.) both within and out with consumers premises.

Project recommendations:

• Appendix A - Training presentation
• Appendix B - Trainers manual
• Appendix C - Training course test paper
• Appendix D - Course registers
• Appendix E - Draft GIS/PL5-1:2015
• Appendix F - SGN draft work instruction
• Appendix G - Field trial report
• Appendix H - Cost analysis from 'The Sunshine' pub Farlington
• Appendix I - Pipe sizing analysis

This document is an executive summary for this project. The full report is not generally available due to prior agreements with manufacturers.

The UK statutory approval scheme for oil spill treatment products has been in place for nearly 30 years. During this time the approval process, including the two toxicity testing elements (The Sea and Rocky Shore tests), has become established as one of the most respected and comprehensive in the world. However, it has changed very little in that time and this has prompted a current review of the testing and approval process.

The review will encompass many aspects of the schemes applicability, organisation and flexibility and this research project was commissioned to address one specific aspect that had been highlighted as of particular concern. Due to the longevity of the scheme, and the fact that products require their approvals to be renewed every five years, certain products have now been through the renewal process on numerous occasions. This introduced a phenomenon known as 'constituent creep' by which small amendments by applicants were made to constituent recipes thus resulting in a slightly different formulation over time.

Scientific judgement was used to assess whether these small changes were environmentally significant but it was recognised that there was a lack of sound toxicological information regarding dispersants and their constituents to aid this decision process and therefore the advice was potentially subject to challenge. This research project was commissioned to address the issue. Extensive testing was conducted using original and amended formulations (in which specific constituent proportions were changed) to see whether modest formulation changes were toxicologically significant. In general, it was found that small changes in any constituent did not change the dispersant performance in the Sea Test but that there was some evidence of changes in the Rocky Shore test. This difference was due to the masking effect of the oil toxicity in the Sea Test and it was concluded that the test was not appropriate for differentiating between these modest formulation changes.

Further studies focused on inherent toxicity assessments of original and amended dispersants using the Tisbe battagliai bioassay. These concluded that small increases in certain constituents caused an increase in formulation toxicity (e.g. sodium dioctyl sulphosuccinate - SDS) while others caused no increase or even decreased the toxicity (e.g. sorbitan monooleate - SMO). This approach allowed the categorisation of dispersant constituents in relation to their ability to contribute and amend inherent formulation toxicity.

The toxicity results are discussed in detail and their relevance to environmental scenarios and the possible use of predictive techniques such as quantitative structure activity relationships (QSAR) are also covered in the report.

Drawing on the research results four potential 'Assessment Protocol Options' have been detailed and their advantages and disadvantages discussed. A number of recommendations are made including the need to engage other stakeholders in forming a consensus way forward with the assessment process and the need for a proposed assessment process review to address a range of important issues relating to the scheme.