Introduction: National Grid will work with a research supplier to deliver a report at the end of each of the three phases outlined below:

1. Test how effective National Grid’s existing drainage solutions (installed to prevent the release of mineral oil) are at controlling a release of Midel 7131.
   • Test the efficacy of existing civil infrastructure to control the presence of potential Midel 7131 pollutants to less than 5ppm in water discharged from a National Grid substation site?

   • Assess the performance of Bund Water Control Units (BWCU) and Class I oil separators when dealing with Midel 7131 instead of mineral oil..

2. Test the biodegradability of MIDEL 7131 in a typical substation environment.
   • Investigate the impact that different volumes of Midel 7131 released on substation chippings has on biodegradation rates.

   • Research and report on the availability of suitable accelerants that can be used to increase the rate of Midel 7131 biodegradation?

3. Investigate the availability of alternative innovative secondary containment solutions and recommend bunding solutions for Midel 7131 filled transformers.

Objectives:

The objective of this project is to research and document appropriate environmental containment solutions for Midel 7131 filled transformers on National Grid electricity substations. This will include a study of how bund pumps and separators will ensure that Midel 7131 can be prevented from polluting the environment. The project also aims to enhance industry understanding of the biodegradation of Midel 7131 in a substation environment.

Expected Benefits: The three reports delivered against each of the three phases outlined in the Scope section will provide National Grid with the knowledge required to inform the development of relevant policy documents and technical specifications.